română DOREL RADU, ZENO GHIZDĂVEȚ
Abstract
Both endogenous and exogenous factors influence mechanical strength of oxide glasses. Thus, this property depends on the chemical-structural particularities of the vitreous system, and, also, on the measurement procedures. Due to the influence of random factors, in practice, mechanical strength has distributed values. For its evaluation, different statistical laws can be used.
In the paper, for a flat glass, four types of statistics are tested: the normal law (Gauss-Laplace), the Gamma law, the log-normal law and the Weibull law. Based on the experimental data, a series of statistical indices are calculated, and it is decided which statistical law better model data distribution.
Keywords
statistical analysis, mechanical strength, flat glass, probability distributions
AYLIN AKYILDIZ
Abstract
There has been a rapid increase in interest in nanotechnology and nanoparticles. Nanotechnology has been increasingly brought into the study of cement-based materials in the recent years. Adding nanosized particles in small amounts as materials can affect their properties significantly. In this study, the effect of nano magnetite Fe3O4/humic acid mixture (used as addition of 0.1, 0.5, 1, 1.5, 2, 3, 4 and 5% in mass of the cement) on the microstructural development and mechanical properties of cement composites has been investigated. Hence, samples size of 40•40•160 mm were produced using obtained cement based composites. After 28th days, flexural and compressive strength and water absorption experiments were implemented for cement based mortar samples. The microstructural analysis of mixtures nanoparticles were performed by scanning electron microscopy. Results were compared with the reference composite. As a result, 1% substitution nanoparticles with cement supplied best performance in terms of strength, water absorption.
Keywords
Compressive strength; Fe3O4/humic acid nanoparticles; Mortar; Nanoparticles
GANESH BABU O., DANYA TR., SAKTHIESWARAN N, SURESH P., MUTHURAMASAN U.
Abstract
Development of sustainable and energy efficient construction material has been the viewpoint of research efforts worldwide in recent years. Although the use of Portland cement is unavoidable, many efforts are being made to minimize the use of Portland cement in concrete to a greater extent in infrastructure applications. It is time to utilize new technology materials like geopolymers that offer waste utilization and emissions reduction with enormous ability. An alternate binding material to the OPC has been found out known as geopolymer concrete (GPC). In this study, GPC will be made of fly ash incorporating alccofine in various percentages of 5%, 10%,15% and 20% as partial replacement to fly ash. Zeolite was partially added to fine aggregate at 10%, 20%, 30% and 40%. Rubber fibers were added at 2% by the weight of binder. Alkaline activator for geopolymerisation was prepared by mixing Sodium hydroxide solution at 10M with Sodium silicate solutions are used. Control mix is casted for M30 grade concrete. The samples are proposed to be cured by hot-curing for 24 hours thus mechanical and durability properties were examined. Addition of zeolite at 30% and alccofine at 15% is found to be an optimal content in geopolymer content and when the concentration of zeolite in geopolymer concrete is increased the slump value decreases. The rubber fiber contents kept constant at 2%, only lesser voids are generated due to improper bonding between rubber fiber particles, which does not contribute more in compressive strength. Geopolymer presents denser microstructure, lower total pore volume and optimized pore structure compared to OPC paste and therefore geopolymer concrete is much more durable in an aggressive environment.
Keywords
Geopolymer concrete, fly ash, alccofine, zeolite, rubber fibers
P. MARIA ANTONY SEBASTIN VIMALAN , G. LAVANYA
Abstract
The influence of glass powder as fine aggregate when used in combination with calcined zeolite for the betterment of the workability and strength improvement of self compacting concrete was analyzed in the study. Initially the fresh state properties such as the passing ability, flowing ability and the filling capacity of the SCC were examined. Then the mechanical strength of the zeolite- glass powder containing self compacting concrete was investigated using compression, flexural and split tensile tests. The durability of the SCC was assessed by the water absorption, porosity, chloride permeability and sorptivity tests. The durability and strength results were validated with microstructure analysis such as XRD and scanning electron microscopy studies. Furthermore the Alkali – silica reactivity of the concrete was characterized to analyze the reactivity of the glass aggregates. The results show that the SCC with 30% of glass powder as fine aggregate replacement and 20% of cement replacement by zeolite showed overall better performance. Thus the use of calcined zeolite can reduce the expansiveness in concrete caused by reactive glass powder aggregates and is also an eco-friendly option to minimize the cement utilization thereby reducing the global warming.
Keywords
Durability, Glass powder, Mechanical strength, Microstructure, Natural Zeolite and Self compacting concrete
MOBIN GHAVIDEL SHAHRBABAKI, ALI DELNAVAZ, MAJID GHASEMI, MOHAMMAD DELNAVAZ
Abstract
The present study investigates the effect of aggregate type on the amount of chloride ion penetration in normal weight concrete (NWC) and lightweight concrete (LWC) samples under the influence of sulfate ion. To examine the effect of W/C ratio, all mixes are made with three different W/C ratios of 0.4, 0.45 and 0.5 in this research. Also, the amount of silica fume (SF) in three values of 0, 7% and 10% were substituted for cement to consider the effect of pozzolanic materials on the level of penetration of chloride and sulfate ions. Compressive strength tests, Capillary water absorption, electrical resistivity, Rapid chloride migration test (RCMT) and accelerated corrosion test were done on concrete samples with light-weight and normal aggregates. The results of these two concrete specimens were compared. The results showed that the corrosion rate of steel bar was higher with increasing ratio of W/C. Also, the mechanical and durability properties of concrete was improved by adding SF to the concrete mix design , resulting in the lowest corrosion rate in the two, chloride solution and combined magnesium sulfate - chloride solution. In addition, concrete samples in the chloride solution became more corrosive than the combined chloride - magnesium sulfate solution. Finally, a neural network model was developed to determine the chloride ion permeation coefficient and the corrosion rate of steel in normal and lightweight aggregates.
Keywords
Chlorine ion penetration, Magnesium sulfate, Corrosion of steel reinforcing bars, Silica fume
A.VISHNU, V. PONMALAR
Abstract
This research mainly focuses on the durability of self-compacting concrete replaced with cement and Nano-metakaolin (NMK). NMK was prepared by heating kaolin at (760-780) oC sustaining for 2 hrs. NMK was used in this study by replacing cement by weight with 1, 2, 3, 4, 5 and 6 % individually. The optimal proportion of replacement of river sand by manufactured sand is 45 %. The consistency, initial and final setting of NMK were predicted and compared with ordinary Portland cement (OPC). Fresh concrete tests like slump flow, T50 cm, U Box, V-funnel, and hardened concrete tests like compressive tests were conducted at 7, 28, 60 and 90 days. Water absorption, Porosity test (Absorbency), Acid Attack, sulphate Attack, Indicator of Concrete’s Capability to Attack Chloride Ion Penetration (RCPT) tests were conducted to observe the durability of Self-compacting concrete (SCC). From the analysis it is clear shown that addition of NMK increases with 7, 28, 60, 90 and 180 days compressive strength and the optimum level was found to be 4 %. The fissure width had diminished by the incorporation of Nanometakaolin while reducing the calcium hydroxide (CH) and mediating calcium silicates to calcium silicate hydrate (C-S-H). The final consequences of compressive strength, durability and flow property shows that 4 % of Nanometakaolin by weight of cement increases the workability, strength and compromises the durable properties.
Keywords
Nanometakaolin, Self-Compacting concrete, Rapid chloride penetration test (RCPT), workability, Absorbency
GOKHAN CALIS, MUHAMMET ENES AKPINAR SADIK ALPER YILDIZEL, MUSTAFA TOLGA ÇÖĞÜRCÜ
Abstract
Due to high consumption of natural sources in the production of cement, scholars have been studying alternative materials that can replace cement in the concrete. Metakaolin and fly ash are used by scholars for their chemical properties and filler effect as pozzolanic material. In this study effect of PVA fiber, metakaolin and fly ash in concrete samples are investigated. The number of experiments to be carried out was reduced to 25 with the Taguchi optimization method, in this research. In addition, the recommended mixing ratios were obtained by this preliminary optimization study. Taguchi optimization were applied according to the experimental test results. F-value comparison of each ingredients were analyzed via ANOVA to list the most effective factors on the strengths based on the Taguchi optimization results. Later Response Surface Design was applied to the output parameters of the ANOVA and Taguchi methods to obtain better and detailed clarifications of relations between the input parameters and the strengths.
Keywords
PVA fiber, fiber reinforced concrete, optimization
OZER SEVIM, MEHMET BARAN, ŞÜKRÜ DEMIR
Abstract
Fly ash (FA) and granulated blast furnace slag (GBFS) produced as waste materials from coal power plants and iron/steel sector are commonly used in the concrete industry for partial substitution of cement. As the production of cement releases a substantial amount of carbon dioxide, its replacement with FA or GBFS reduces carbon dioxide emissions. This study explores the effects of FA and GBFS fineness determined by particle size distribution (PSD) on the hydration rate and compactness of cementitious materials. Firstly, FA and GBFS were classified to have three different fineness ranges with the help of PSDs without any grinding process: FA and GBFS without PSD, FA and GBFS with 0-25 µm PSD and FA and GBFS with 0-63 µm PSD. Then, flexural strength, compressive strength, and water absorption properties of cementitious composites containing FA and GBFS with four different replacement levels up to 20% wt. of cement and with three different fineness were investigated at curing ages of 7, 28, and 90 days. Results revealed that cementitious composites that contain FA and GBFS with lower PSD yield better mechanical and physical properties.
Keywords
Cementitious composites; particle size distribution; fineness; fly ash; granulated blast furnace slag
RĂZVAN LISNIC, SORIN ION JINGA
Abstract
Coal-fired power plant represents the major source of sulphur dioxide emissions in Romania. This study presents the influence of a wet FGD system applied to an energetic block from Rovinari power plant in Gorj county over SO2 dispersions regarding air quality. Sulphur dioxide emissions were modelled using AERMOD software considered a state-of-the-art dispersion model for industrial sources.
The results were plotted to Google Earth Pro showing a decrease of 95.6% for SO2 hourly maximum concentrations and a decrease of 92.7% for SO2 daily maximum concentrations.
Keywords
wet flue gas desulfurization, efficiency, SO2, emission modeling, software dispersion model, AERMOD.
WEICHAO YING, GE ZHANG, YINGZI YANG
Abstract
In winter construction, it is of crucial importance to predict the temperature field of concrete, to avoid frost damage, control the temperature gradient, and ensure the construction quality of concrete. In this study, a modified finite element model (FEM) considering the characteristics of winter construction was proposed to predict the temperature field of concrete. The freezing process of free water and the heat release of hydration varied with concrete temperature was involved in this model. Then, the temperature histories of two types of concrete placed at different subzero temperatures were monitored experimentally and simulated by using the modified FEM. Good agreement of these results confirms the validity and reliability of this model. Finally, some numerical experiments were performed to explore the effects of engineering parameters on the temperature field of early age concrete by using the validated finite element model. The results show the law of influence of concrete placing temperature and geometry, ambient temperature, and the thickness and thermal conductivity of insulation material on the concrete temperature field.
Keywords
Finite Element Analysis; winter construction; temperature field; thermal insulation curing
HUSSEIN HAKIM HASAN, RADU PASCU, DAN PAUL GEORGESCU
Abstract
The Fibre Reinforced Cementitious Matrix (FRCM) composite material is a relatively new retrofitting system which is used to increase the strength and overall ductility of concrete structures. This paper presents a comparative study on the performance of concrete columns confined with FRCM, using the experimental, finite element method (FEM) and analytical evaluation techniques. Six concrete columns were experimentally tested under monotonic uniaxial compression loading: two specimens without confinement, two specimens with one FRCM layer and two specimens with two FRCM layers. Material tests were also performed on concrete cubes, for each concrete column. A complex nonlinear numerical FEM tridimensional model was developed in Abaqus finite element environment for each concrete column and calibrated against the experimental results. Calibration for each concrete material was also performed, assuming the Eurocode 2 model for obtaining the stress-strain curves used to characterize the behavior of concrete under uniaxial compression. Concrete Damaged Plasticity Model (CDPM) was assigned to the concrete parts. The performance of columns is evaluated in terms of axial load carrying capacity, axial compressive strength, ultimate axial deformation and strain. FEM results also revealed the cross-section distribution of the confining stresses due to FRCM. Analytical predictions according to several researchers are also presented in view of comparison.
Keywords
plain concrete column, FRCM, confinement, CDPM, analytical model
LEONID DVORKIN, VADIM ZHITKOVSKY, YURI RIBAKOV
Abstract
The paper shows the use of activators for the hardening of cement-ash concrete, incl. passing when heating concrete. Such an activator is a composition of sodium fluorosilicate and naphthalene-formaldehyde superplasticizer. The addition of sodium fluorosilicate makes it possible to increase the early strength of the cement-ash binder, enhance the kinetics of pozzolanic reaction and reduce the drop in the strength of the cement-ash stone when it is heated to 800°C. Experimental dependences of concrete mixture water demand and concrete strength on the cement and aggregates consumption for different workability mixtures have been obtained. These dependences take into account the influence of complex admixtures of superplasticizer and sodium fluorosilicate that enabled to propose a method for design of ash and slag concrete compositions. The positive role of the proposed complex activating admixture on the change in strength and shrinkage of ash and slag concrete after drying and subsequent heating has been experimentally confirmed. A complex of experimental-statistical models of ash and slag concrete properties has been obtained, taking into account the influence of activation admixture, superplasticizer and sodium silicon fluoride consumption, cement-water ratio, temperature and the number of heating and cooling cycles.
Keywords
heat-resistant concrete, fly ash, ash and slag mixture, superplasticizer, sodium fluorosilicate
DENG CHEN, ZHI-HAI HE, AI-GUO WANG, TAO YANG
Abstract
Shrinkage of cement-based materials may cause cracking in concrete structure under restrained conditions. In this study, light-burnt dolomite (LBD) as a mixture of periclase and calcite obtained by calcinations of dolomite at 750-850 °C was incorporated in Portland cement to compensate shrinkage of cement-based materials at early age. The results show that the water requirement for normal consistency of blended cement is increased with the increase of dosage, calcination temperature and holding time of LBD. The addition of 10% LBD calcined at 800 °C for 2.0 h can effectively enhance the compressive strengths of blended cement at all ages. This is due to that 10% LBD can improve the microstructure attributed to the filler effect and hydration reactivity of LBD. Furthermore, the hydration of periclase in LBD leads to the expansion of blended cement at early age, and increases the expansion value with the increase of dosage, calcination temperature and holding time of LBD.
Keywords
light-burnt dolomite, blended cement, strength, deformation
P. AMSAYAZHI, K. SARAVANA RAJA MOHAN
Abstract
The study of High strength concrete with fibers had become the most popular topic as the demand for height and load carrying capacity of every infrastructure is increasing. The addition of fibers in concrete increases durability, tensile strength, toughness, energy absorption, high impact resistance, in terms of both static and dynamic loading. In this paper, the strength properties of glass fiber reinforced concrete as a structural element was investigated. Different ratios of GFRC mixes were designed, cast, tested, and compared with the results of compressive strength, tensile strength, flexural strength, and also impact strength.M50 grade of concrete was used in this study with five proportions (0, 0.5%, 1%, 1.5%, 2%) of Glass fibers. The impact strength test was analyzed using Weibull analysis to compare with the experimental data. The main objective of this study is to show how the increase in fibre percentage increased the strength of concrete.
Keywords
Glass Fiber, High Strength Concrete, impact strength, Weibull method, Numerical analysis, Strength Properties
RUXANDRA- ELENA GEANALIU-NICOLAE ADRIAN- IONUȚ NICOARĂ, ECATERINA ANDRONESCU, ROXANA TRUȘCĂ
Abstract
In order to obtain a drug delivery system used in tumoral treatment, this study presents the characterization of mesoporous silica /antitumor drug hybrid materials obtained in A NOVEL METHOD OF SYNTHESIS FOR NANOPOROUS SILICA MATERIALS [1]. There were synthesized eight hybrid materials, using two types of mesoporous silica as support material and irinotecan respectively thyme oil as active substances. Mesoporous silica was synthetized using two techniques, classical sol-gel and novel microwave-assisted hydrothermal method, resulting different structural characteristics for materials. Loading with irinotecan was realized in aqueous solution at neutral and acidic pH environment using impregnation method with drug solution. Other four materials were synthesized using thyme oil 3% and 5%.
In this study hybrid materials were characterized using different techniques such as X-ray diffraction, FT-IR, Thermal analysis, scanning electron microscopy which offered morpho-structural information. Others analysis performed were kinetics and in vitro cytotoxicity which established the potential use for biomedical applications showing the antitumoral activity.
Keywords
MCM, mesoporous silica, hexagonal mesostructure, drug delivery system, biomaterials, irinotecan, thyme oil, cancer treatment
RADU MIREA, GIMI RÎMBU, MIHAI IORDOC,, ANDREI TIBERIU CUCURUZ
Abstract
The experimental investigation of hydrogen adsorption capacity in Ruthenium doped nano-structured carbonic materials, by using two methods has been carried out within this paper. It is well known that carbonic materials along with metal hydrides are considered to be one of the most promising materials to be used for hydrogen storage by using adsorption method, specifically based on "spill-over" phenomena. These materials have different applications and one of the most important is considered to be fuel cells technology for mobile applications, namely onboard automotive hydrogen storage. By using transitional metals in order to dope carbonic materials, their adsorption capacity increases, thus approaching “the target” of 4,5% weight ratio of H2 adsorbed in a substrate, according to US Office Of Energy Efficiency And Renewable Energy [1]. Within this paper carbon based nanomaterials: multi-wall nanotubes (MWNT) and poly-aniline (PANI) have been used as substrates for Ruthenium doping and their hydrogen storage capacity has been determined. PANI has been firstly prepared and after that doped in laboratory, while MWNT have been purchased from the market and afterwards doped in laboratory. The doping procedure consists of a physical-chemical method which involves Ru salts and the use of ultrasounds in order to activate the carbon based substrate for doping.
The adsorption and storage capacity of carbonic materials has been determined by using spill-over phenomena in a PCT Pro-User apparatus, provided by SETARAM and also calculated from cyclic voltametry, by using VoltaLab-40 apparatus. In order to investigate the adsorption capacity of the nano-structured carbonic materials, the experiments have been carried out at different pressures (ranging from 10 to 30 bar). Both substrates have been characterized in order to determine their porosity, BET surface and XRD before and after doping.
Keywords
Hydrogen adsorption, weight ratio, doped carbonic materials, poly-aniline, and carbon nanotubes.
ALINA IULIA DUMITRU, GEORGETA VELCIU, DELIA PĂTROI, JANA PINTEA, TUDOR-GABRIEL DUMITRU, ILDIKO PETER
Abstract
In this paper, some compositions belonging to the 0.98Pb(Zr1-xTix)O3 – 0.02La(Fe3+0.5, Nb5+0.5)O3 system have been investigated. The considered materials have been obtained by solid state reaction technique at high temperatures (1100°C, 1150°C, 1200°C and 1250°C). Three values of x (one in tetragonal region, one in Morphotropic Phase Boundary-MPB- region and one in rhombohedral region) have been chosen for the study in the range of 0.42 - 0.58. Sintering behaviour of the ferroelectric compositions has been studied by the experimental determination of the density by the method Archimedes. These ferroelectric compositions have been investigated in terms of their structural behaviour using X-ray diffraction (XRD) analysis. The XRD results have evidenced the formation of the perovskite type structure for all the studied compositions. The influence of theZr4+/Ti4+ ratio correlated to the sintering temperature on the degree of incorporation of the elements in the solid solution have been studied too. All the considered ferroelectric compositions have been characterized by a high anisotropy. The PZT modified compositions reveal that the piezoelectric properties are governed by the Zr4+/Ti4+ ratio and the sintering temperature too. For the electromechanical coupling factor (kp) the maximum value kp = 0.67 has been obtained for the composition with x = 0.58 and sintered at 1200°C.
Keywords
lead zirconate titanate (PZT) ceramics, ferroelectric compositions, high anisotropy, piezoelectric properties, dielectric properties
DORINEL TĂLPEANU, MAGDALENA VALENTINA LUNGU, DELIA PĂTROI, ANCA COJOCARU
Abstract
In this study were achieved advanced materials through the processing of some titanium-hydroxyapatite (Ti-HAp) powders by spark plasma sintering (SPS) technique. The Ti-HAp powders containing 95 wt.% Ti and 5 wt.% HAp were mechanically milled for 40 hours and then sintered at 900°C, 1000°C, and 1075°C for 10 minutes by SPS. The surfaces of the SPSed samples were finished by mirror polishing so that the final sizes were 20±0.05 mm in diameter and 4±0.3 mm in height. The samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The density was determined by Archimedes’ method in distilled water, and the mechanical properties were investigated by instrumented indentation testing and Oliver & Pharr method. The surface roughness Ra was determined by contact profilometry. The tribological tests included the measurement of the coefficient of friction (COF) in dry conditions. All sintered samples revealed crystalline phases, homogeneous microstructure, high density (4.45-4.52 g/cm3), low surface roughness Ra (0.07-0.14 µm), high Vickers hardness (786-879 HV), Young’s modulus of 111-137 GPa, elastic contact stiffness between 6.48 N/µm and 6.9 N/µm, and mean COF of up to 0.47. The properties were enhanced with the increase of the sintering temperature due to the advanced features of the SPS technique. Ti-HAp powder sintered at 1075°C revealed the best properties that recommend this material as a promising candidate in the development of medical applications.
Keywords
titanium, hydroxyapatite, Ti-HAp powders, spark plasma sintering (SPS)
DORINEL TĂLPEANU, MAGDALENA VALENTINA LUNGU, ANCA COJOCARU, DELIA PĂTROI, VIRGIL EMANUEL MARINESCU
Abstract
The study was focused on the development of some porous hydroxyapatite (HAp) based ceramic materials as bone substitutes for cranioplasty. The HAp samples were elaborated by a hot pressure casting technique at a casting temperature of 90°C and 5 atm pressure, having 77 wt.% HAp and 23 wt.% melted paraffin and bee wax binder. The samples were casted without and with the addition of 5 wt.% and 10 wt.% porogen agent. Then the cast samples were dried, dewaxed, and sintered at 1150°C, 1200°C, and 1250°C for 2 hours. The final sizes of the sintered samples were 10±0.05 mm in diameter and 40±0.3 mm in length. The structural properties were investigated by X-ray diffraction (XRD). The water absorption, apparent porosity and apparent density were determined by standard test methods for ceramics. The mechanical properties were investigated by flexural and compressive tests. The microstructure was analyzed by scanning electron microscopy (SEM). All the sintered samples revealed crystalline phases and homogeneous microstructure. The apparent density was 1.28-1.76 g/cm3, the apparent porosity was 43-57 %, the flexural strength was 4-8.6 MPa, and the compressive strength was 5.4-13.7 MPa. The obtained results meet the technical requirements imposed for porous ceramics used in cranioplasty. The properties were enhanced with the increase of the sintering temperature but the addition of the porogen agent contributed to an increase of the apparent porosity and a decrease in mechanical strength. The samples sintered at 1250°C revealed the best properties that recommend the developed HAp materials for biomedical applications.
Keywords
hydroxyapatite, biomaterials, hot pressure casting, porogen agent
B. SUGUMARAN, G. LAVANYA
Abstract
Insufficient and ineffective curing may decrease the strength of self compacting concrete forming high shrinkage cracks and voids. The shrinkage due to evaporation is the main reason for the deterioration of concrete structures. The use of internal curing agents in combination with expansive agents can solve the problems of shrinkage and self desiccation caused due to self curing and has the potential for achieving predefined properties. The present research works aims at the production of self compacting concrete with higher strength and durability by utilizing GGBS, alccofine and nano metakaolin as cement admixture along with copper slag as partial substitute for fine aggregate. Several investigations were carried out to analyze the influence of using MgO based compounds as expansive agents in the concrete on the mechanical, fresh state and durability tests. The results show that addition of expansive agent provided desirable strength values and durability properties in the self compacting concretes. The use of highly free flowing concrete that are self compacting in nature with high strength and dimensional stability is also achieved due to the synergistic effect of expansive agents and mineral admixtures in the concrete.
Keywords
self compacting concrete, nano metakaolin, alccofine, copper slag, expansive agent, self curing agent, strength, durability
ALI SADRMOMTAZI, NEGAR GHASEMI KHAMENEH, REZA KOHANI KHOSHKBIJARI, MORTEZA AMOOIE
Abstract
As a novel solution, to reduce or even eliminate the dependence on the ordinary Portland cement (OPC) which as an energy-intensive and highly polluting production, and simultaneously, for effectively using waste materials, Geopolymer concrete (GPC) has emerged. GPC is manufactured by using alkali-activated binders instead of OPC. In this study, the differences and impacts of the partial replacement of the Slag by the most common pozzolans such as Rice Husk Ash (RHA), Fly Ash (FA), Metakaolin (MK), Silica Fume (SF), and Zeolite on the durability of the Slag-based GPC are investigated. To evaluate the durability performance of the specimens, a series of tests including compressive strength (7, 28 and 90-days), Rapid Chloride Permeability Test (RCPT), Rapid Chloride Migration Test (RCMT) and Accelerated Corrosion Test (ACT) were performed. Also, the samples were exposed to Sulfuric acid solution in order to investigate the effect of this corrosive environment on the weight reduction and compressive strength changes of the mix designs. The results indicated that using up to 10% replacement of Slag in GPC with FA, SF and MK can improve the durability in RCPT, RCMT, and ACT and also can cause significant improvements in durability against Sulfuric acid in all replacement ratios.
Keywords
geopolymer concrete, slag, durability, binder solid replacements
AHMET GÖKDEMİR, TALAT YATKIN
Abstract
Throughout history, the Anatolian Peninsula, with its many fertile lands and many settlements of civilization, has seen a bridge between civilizations due to its position on commercial and military roads. Ankara, the capital, since the establishment of the Republic of Turkey; is a witness to many political, administrative and military events that have been up to date. For this reason, the city has a rich cultural heritage. Ankara Castle, which has always been in the same place since the Hittites, repaired many times during the Roman, Byzantine and Seljuk periods. It is very important that the materials used in the restoration work are compatible with the existing structure. In this; an analysis of the existing material was carried out which could shed light on the restoration work to be done on the Ankara castle.
Therefore, from Ankara Castle were taken samples from the materials used in the areas where structural deterioration occurred on the east, west, north and south facade walls. On the samples, material characteristics were analyzed by using methods such as SEM, EDS, F-TIR. In addition, density, water absorption, compressive strength and thermal conductivity properties of the samples were measured.
As a result, the physical, mechanical and thermal properties of the materials used in the construction of the Ankara Castle have been revealed. As a result, it is possible to apply materials compatible with the existing structure that can be used in the restoration works of the Ankara Castle.
Keywords
Ankara Castle, Restoration, Materials, Strength, SEM, EDS
LINCHUN ZHANG, AILIAN ZHANG, QIAN WANG, YAN HAN
Abstract
This study aimed to investigate the preparation of cement foamed mortar mixed with coal gangue power. Moreover, the following rheological parameters and compressive strength were determined. Additionally, a scanning electron microscope (SEM) was used to reveal its compressive strength`s inner mechanism. Results indicated that slump flow of fresh coal gangue power foamed mortar increased first and then kept stable with water-reducing agent. The increasing content of coal gangue power could descend the compressive strength of foamed cement mortar. Compressive strength of foamed cement mortar decreased linearly with foam content and ascended in the exponential or linear functions with volume density. The scanning electron microscope (SEM) images showed that many shapes of hydration products existed in the specimens. Moreover, the microstructure of specimens became denser with decreasing cement-sand ratios
Keywords
Foamed mortar; Coal gangue powder; Rheological parameters; Compressive strength; Scanning electron microscope
A. SIČÁKOVÁ, E. FIGMIGOVÁ
Abstract
One of the progressive and currently rapidly developing methods for improving the properties of concrete with recycled aggregates is internal curing, which means the supply of curing water directly from the inside of the concrete. This article introduces two variants of internal curing of concrete with recycled brick aggregate (RBA) by pre-soaking process as a part of specific mixing course. The presented variants differ in the dosage of aggregates and water in the soaking process. Results of consistency, compressive strength, total water absorption capacity and capillary moisture content are analysed in terms of their change due to pre-soaking process, as well as due to time of processing the fresh concrete (90 minutes). The process of pre-soaking of RBA is beneficial for the consistency of concrete when evaluated immediately after mixing. For both the compressive strength and total water absorption capacity, the variant of pre-soaking is determining. Pre-soaking of only coarse RBA by amount of water derived of its absorbability (variant 1) gives better results than pre-soaking of all amount of aggregate by ½ of total mixing water (variant 2). The processing time 90 minutes does not adversely affect the compressive strength of concretes either with pre-soaked RBA or non pre-soaked RBA, even the strength increases slightly with processing time.
Keywords
concrete, internal curing, recycled brick aggregate, fly ash, mixing course, discharge time
ALI SABERI VARZANEH, MAHMOOD NADERI
Abstract
Today, it is significantly important to perform non-destructive tests to evaluate the quality of cement materials. However, in such tests, some parameters are typically measured indirectly to estimate the strength of the material by specific relations. Thus, the present study evaluates the compressive and flexural strengths of cement mortars reinforced with polypropylene fibers at different ages by using the slight-destruction twist-off and pull-off tests. For this purpose, using the linear and power regression analyses, the relationships between the results of the mentioned in-situ tests and the strengths of fiber-reinforced mortars were identified. Then, calibration diagrams were provided to translate the twist-off and pull-off results into the compressive and flexural strengths of the fiber-reinforced mortars. Also, given that the proper connection between cement materials and steel is one of the crucial issues in civil engineering, in this paper, has investigated the effect of polypropylene fibers on the shear and tensile bond strength between cement mortar and steel plates, using “Push-out”, “Twist-off” and “pull-off” tests. At the end, using the finite element method (FEM), the fiber-reinforced and non-fiber reinforced samples were modeled, analyzing the effects of fibers on the tests. The results indicated a high correlation coefficient between the experimental results and semi-destructive tests. Moreover, the addition of fibers improved the behavior of cement mortars subjected to compression. The modeling results of the in-situ tests revealed the delayed cracks and increased strengths of the fiber-reinforced mortars. Also, the obtained results revealed the marked effect of fibers in increasing the bond strength between the mortar and steel.
Keywords
Semi-destructive tests, Finite element method, Bond, Mortar, Steel
PAVLA BAUEROVÁ, PAVEL REITERMAN, VENDULA DAVIDOVÁ, EVA VEJMELKOVÁ, MAGDALENA KRACÍK ŠTORKÁNOVÁ, MARTIN KEPPERT
Abstract
Linseed oil has been used as mortars admixture in times before the modern synthetic admixtures were introduced. The present study deals with influence of linseed oil on the engineering properties of air lime mortar. The composition of mortar was inspired by a mortar used for fixing of 1890´ mosaic in Krásná Lípa (Czech Republic). The knowledge of complex influence of the oil on mortar’s performance is important for the preparation of renovation mortars but also for possible application of the oil as sustainable mortar admixture, replacing the nowadays synthetic ones. The oil is reducing the yield stress of the fresh mortar (i.e. acts as plasticizer) and is increasing its air entrapment. The water-repealing effect is the most important impact of the oil admixing on the harden mortar; it was evaluated by measurement of water absorption coefficient. The higher air entrainment and water-repellence are resulting to the improved frost resistance of the mortar containing the oil.
Keywords
mosaic, mortar, linseed oil, durability
AHMET ONUR PEHLİVAN
Abstract
Concrete is a brittle material that should be enhanced with better tensile strength and toughness capacity. Concrete matrix is generally reinforced with fibers which are extremely helpful inhibiting the crack propagation and supplying the ability of strain accumulation into concrete matrix. In this study, an environment friendly type of fiber was introduced into concrete for the investigation of mechanical properties and fracture characteristics by size independent double-K fracture parameters asserted in the literature. Effect of basalt fibers with different lengths and contents were investigated under notched three-point bending tests and relevant parameters obtained and calculated, were compared for two distinct parameters: fiber length (6, 12, 24 mm) and content (0, 0.1%,0.3%, 0.5%, 1%). Shorter fibers confronted dispersion problems when used in higher content whereas 12 mm fiber specimens performed more stable results. Fracture energy dissipation was found to be linearly increasing with increasing fiber content and also longer fibers were found to be more efficient. Double-K fracture parameters were found to be resourceful when considering toughness and ductility of the material besides these parameters indicated useful information regarding the pre-cracking and post-cracking behavior of concrete. SEM investigations were also conducted to monitor the bonding between basalt fibers and concrete matrix.
Keywords
Fracture parameters, Basalt fiber, CMOD, Fracture energy, Fiber length
A.SUMATHI, D. ELAVARASI, K. SARAVANA RAJA MOHAN
Abstract
In this research, the flexural and impact resistance of steel fibre reinforced concrete (SFRC) under static and impact loadings was experimentally investigated. High-strength reinforced concrete steel fibre containing 1% by volume fibre content with a constant w/c 0.39. Hooked steel end fibers were used with a circular cross section of 1 mm in diameter and an aspect ratio of 30. Flexural behaviour of SFRC was carried out on a beam specimen of size 1200 x 100 x 200 mm subjected to two-point bending test as per ASTM C78 standard specification. Impact resistance was performed on a thin SFRC slab specimen of size 600 x 600 x 50 mm subjected to low velocity drop weight impact test as per the prescribed ACI 944-89. For comparison purpose, the conventional RCC specimens were also cast and tested. The test results found that the flexural strength and toughness of SFRC specimen remarkably increased by 35% and 50% respectively compared to RCC specimen. The addition of steel fibers to concrete increases the stiffness and ductility characteristics. The first crack and ultimate energy absorption potential of SFRC slab specimens were increased by 173.5 and 3.72 times, respectively, compared with RCC slab specimens. From the test results concluded that the flexural and impact resistance was significantly improved with addition of steel fibres in concrete.
Keywords
HSFRC, Toughness, Ductility, Energy absorption, Impact residual strength ratio.
A.VISHNU, P. ARULMURUGAN, V. PONMALAR
Abstract
The structural recital of axially loaded concrete containing Nano metakaolin (NMK) in filled steel composite columns is investigated. The ratio of height and breadth of the specimens are kept constant as 6.25 and M20 grade of concrete is used. The width to depth ratio is assumed to be taken as 1.00, 1.25, 1.50, 1.75 and 2.00. The foremost constraint of the task is to study the effectiveness of concrete in filled steel hollow sections with bolted connection incorporating NMK as cementitious substantial. The columns examined are different in cross-sectional dimensions. The axial load is provided to the core concrete alone and the behaviour of the confined cold form steel is studied, and axial load of reinforced concrete column and confined columns are compared. The optimal percentage at which cement can be substituted with Nano-Metakaolin is found to be 4 % and XRD analysis is carried out to predict the pozzolanic activity of cementitious materials. Also, consequences show that the column with greater cross-sectional area had higher load carrying capacity of about 33 kN while comparing to reinforced columns.
Keywords
Metakaolin (MK), Nano Metakaolin (NMK), Cold-formed steel (CFS), Hat section, In-filled, Columns, Axial load
EYUBHAN AVCI
Abstract
In this experimental study, the effects of different curing temperatures and curing conditions on the unconfined compressive strength of microfine cement injected sand samples were investigated. The experiments started with determination of the rheological properties of the microfine cement suspensions prepared in different Water/Cement (W/C) ratios. With the increase in the W/C ratio, setting times and bleeding percentage decreased and viscosity values increased. After determination of rheological properties, injection experiments were carried out microfine cement suspensions with W/C ratios of 1.5, 2.0, 2.5, 3.0. While the injectability was increased with the increase of W/C ratio, it also decreased with the increase of the fine sand content. The samples that were successful in injection were kept in different curing temperatures and conditions. Then, the unconfined compressive strength tests were carried out on the 3rd, 7th, 14th, 28th, 56th and 120th days. The unconfined compressive strengths of the grouted sand samples were increased with time and the rate of increase started to slow down after a certain value. Due to the increase of temperature, the grouted sand samples were gained faster strength. The unconfined compressive strength values of the injected samples increased with increasing temperature. The unconfined compressive strength of the sand samples that were grouted and kept in the air-dried environment was higher than the unconfined compressive strength of the sand samples that were injected and kept in the wet-curing conditions.
Keywords
Curing condition; Curing temperature; Microfine cement; Unconfined compressive strength
SUHANG YANG, ZHIFENG XU, ZHENGNING BIAN
Abstract
Shear strength is the essential mechanical property of structural concrete, especially for complex stress analysis and finite element analysis. Laboratory core double shear testing (LDST) is considered time-consuming and expensive testing for the measurement of the in-situ shear strength of concrete. The object of this paper is to introduce an innovative in-situ shear test (IST) method for the measurement of the shear strength of partial concrete cores. According to the principle of the clamping mechanism, the time required for field testing was reduced to less than 30 minutes. The core samples in different diameters and lengths were compared by IST and LDST. Student’s t-tests of shear strength results obtained by using LDST and IST showed an evident difference between the two methods. The shear strength of the core increases with the decrease of the core length and increases with the core diameter. The standard deviation of the results was considered as an increase with a reduction of core diameter for both LDST and IST. Since no extraction of core specimen is needed, and the core length is less than that of tested using LDST, and the specimens can be easily carried and quickly performed in-situ with less damage to the structure. The shear strength of concrete measured by IST is inferior to that of obtained by the LDST method, and correction efficiency must be adopted to adjust IST test results to that LDST. A good correlation between concrete IST strength and cube compressive strength is proposed in the paper.
Keywords
Concrete; compressive strength; shear strength; Laboratory core double shear testing (LDST); In situ shear testing (IST); compressive strength
CRISTIAN DOBRESCU, SÂNZIANA ITTU, NICOLAE CONSTANTIN, BOGDAN FLOREA, VALERIU RUCAI, DRAGOȘ FLORIN MARCU
Abstract
The goal of this paper was to analyze the industrial behavior of CENOTERM coating powders used in continuous casting of steel. CENOTERM powder is made using thermal power plant ash in the manufacturing recipes. The thermal power plant ash is part of the range of industrial waste. In the context of this paper, CENOTERM coating powder was used for continuously casting steel under industrial conditions. Industrial experiments with powder recipes for the thermal power plant ash-based dispenser were carried out at MECHEL Târgoviște.
Testing of coating powders at an economic agent where continuous casting of steel is carried out has been carried out with a view to finalizing these powders’ manufacturing technology. The paper presents the analysis of the behavior in industrial conditions of coating powders made from indigenous raw materials, some of which are even landfilled waste. The research carried out revealed the functions of the powder on the surface of the liquid steel and the final effects of the powders on the quality of the steel.
Keywords
coating powder, secondary materials, thermal power, fly ash, steel, continuous casting.
COSMIN MIHAI MIRIŢOIU, DUMITRU BOLCU, MARIUS MARINEL STĂNESCU, ALIN DINIŢĂ, ALEXANDRU RĂDOI
Abstract
In this paper the mechanical characteristics of a new gree resin, with and without natural reinforcement are presented. In the fist part of the investigation, from the tensile test, some mechanical characteristics are determined, such as: breaking strength, elongation at break, Poisson ratio, static Young modulus and tensile stiffness. A representative image with the samples breaking section using the scanning electron microscopy analysis has been presented. Then, from the free vibrations recording by clamping the bar at one end and leaving it free at the other, the damping factor per unit mass, per unit length, the dynamic flexural stiffness, dynamic Young modulus and the loss factor are determined. Using the thermogravimetric analysis (TGA), the thermal stability of the studied resin is investigated. In the las part of the study, some green composites by using the poposed resin reinforced with wheat straw fibers are manufactured. It has been found out that the proposed eco-resin reinforced with wheat straw has incresed mechanical properties compared to other eco-resins from the engineering literature such as: soy based resins (reinforced with cotton, jute, flax, kenaf, hennequen or hemp), polylactic acid resin reinforced with wheat straw and so on.
Keywords
green composite, green resin, static behaviour, dynamic behaviour, wheat straw
OTLILIA CHIRCA, CORNELIA BICLEȘANU, ANAMARIA FLORESCU, LUDMILA MOTELICĂ, ALINA MARIA HOLBAN, ALEXANDRU BURCEA
Abstract
The purpose of this study is to analyze with the help of the scanning electron microscopy and FTIR microscopy, the way in which the adhesion to the dental structure and to different types of ceramics of some adhesive materials is made. For this study, 45 free teeth were used, which were divided into 3 equal groups: group I restored with IPS E.max CAD-On ceramic crowns, Ivoclar Vivadent cemented with Maxcem Elite, Kerr; group II restored with IPS E.max Press ceramic crowns, Ivoclar Vivadent cemented with RelyX Ultimate Clicker, 3M Espe and group III restored with Novodent GS Zirconia crowns cemented with Variolink Esthetic. The teeth were embedded into the resin, sectioned and subjected to the analyses.Both the tooth-cement interface and the cement-ceramic crown interface were evaluated with the help of SEM and FTIR. The materials used showed a good adhesion to the dental structure, and the presence of micro-cracks was observed at the ceramic interface. Moreover, the evaluated materials showed different microbial attachment ability, the most significant adherence inhibition of the Lactobacillus acidophilus being observed in the case of cemented Zirconia crowns.
Keywords
dental crown, ceramics, SEM, self adhesive cement, self-etch cement
VASILE ADRIAN SURDU, ECATERINA ANDRONESCU
Abstract
Configurational entropy has been recently used to develop innovative materials with multiple different cations or anions, belonging to different crystallographic systems. Fluorite oxides exhibit chemical stability, thermal stability and thermal insulating properties and therefore are of interest in high temperature applications. Entropy engineering via compositional considerations proved to be beneficial in increasing hardness and decreasing thermal conductivity coefficient. Several aspects need to be considered and investigated in order to understand the mechanisms involved in the functionality of such materials.
Keywords
ceramics, entropy, fluorites, oxides
ALINA IULIA DUMITRU, GEORGETA VELCIU, DELIA PĂTROI, JANA PINTEA, VIRGIL MARINESCU, TUDOR-GABRIEL DUMITRU, ILDIKO PETER
Abstract
In this paper, some compositions described by the general formula Pb(ZrλTi1-λ)1-3x/4FexO3 have been considered and investigated. The compositions selected have been obtained by solid state reaction, where x=0.01 and λ corresponds to 0.42, 0.52 and 0.58. The samples have been thermally treated in the range of 11000C -12500C and holded for 2 hours at the maximum temperature.
The influence of the sintering temperature on the microstructure and on the electrical properties of Fe3+ doped Pb(ZrλTi1-λ)O3 system has been investigated. The crystallographic phase and microstructure of the sintered compositions has been studied in detail using X-ray diffraction analysis (XRD) and Scanning Electron Microscopy (SEM). The experimental results obtained by XRD reveled that all the sintered samples have a perovskite structure. In order to correlate the behavior of the sintered materials to their microscopic structure, the domain structures have been defined by SEM. The dielectric properties, as dielectric permittivity (εr) and dielectric loss (tanδ) have been measured. The hysteresis loops at room temperature of all un-poled sintered compositions reveal a similar behaviour with “hard” PZT ceramics. The piezoelectric properties like electromechanical coupling factors (kp and kt) and the anisotropy (kt/kp) have been investigated after polarization. The results obtained from such investigations pointed out that some sintered compositions can be successfully proposed as good candidate for targets, materials to be deposited, employed for different applications as ceramic coatings in some deposition technology.
Keywords
doped PZT, dielectric properties, piezoelectric properties, ferroelectric properties
YASSINE BELAICHE, ABDELHAMID KHELEF, SALAH EDDINE LAOUINI, ABDERRHMANE BOUAFIA, MOHAMMED LAID TEDJANI, AHMED BARHOUM
Abstract
Artemisia herba-alba is a medicinal plant, and its essential oil is used as an antiseptic and antispasmodic. In this study, green synthesis of silver/silver oxide (Ag/Ag2O) nanoparticles was successfully synthesized from Artemisia Herba-Alba aqueous leaves extract. The effect of temperature, reaction time, the concentration of AgNO3, the quantity of plant extract, and pH on the synthesis process of Ag/Ag2O was optimized. More interesting, the results showed that only 5 min were required for reducing 1 mM AgNO3 into Ag/Ag2O NPs at room temperature. The crystalline nature of Ag/Ag2O NPs with an average crystallize size of 10.7-36.8 nm. The green synthesizing Ag/Ag2O NPs having in general a spherical morphology with particle/aggregate size less than 100 nm. The maximum UV-Vis absorption peak of Ag/Ag2O NPs was observed at the range of 418- 435 nm giving optical band gaps of 2.05-2.30 eV. The TGA/DTA analysis shows significant organic contents (18 wt%) were physically and chemically adsorbed on the dry weight Ag/Ag2O NPs. Artemisia herba-alba is a source of phytochemicals for effective and prompt fabrication of Ag/Ag2O NPs with relevant insecticidal and anti-bactericidal activity against species of high public health importance.
Keywords
silver /silver oxide nanoparticles; Artemisia Herba-Alba; Silver nitrate AgNO3; Green Synthesis, XRD
ANDREI VIOREL PĂDURARU, OVIDIU OPREA, ADINA MAGDALENA MUȘUC, BOGDAN ȘTEFAN VASILE, ANTON FICAI, ECATERINA ANDRONESCU
Abstract
The paper describes a rapid and a simple method for preparing photoluminescent compounds of different concentration of europium (0-10%) by doping hydroxyapatite, synthetized by coprecipitatin method. The obtained nanomaterial were further characterized by Fourier transfrom infrared spectroscopy, X-ray diffraction analysis, UV-Visible spectroscopy, room-temperature photoluminescence spectroscopy, and scanning electron microscopy. The influence of dopant ion concentration on the structure of hydroxyapatite structure and morphology was followed Hence, the present study proves the integration of europium ions in hydroxyapatite lattice and an enhanced of the luminescent properties of obtained doped hydroxyapatite materials, even at lower concentrations, being able to extend their applications to bioimaging or drug delivery.
Keywords
europium, photoluminescence, hydroxyapatite, coprecipitation
HAYRI AKMAN, KORAY SÜRME , MEHMET AKIN
Abstract
This study evaluated the shear bond strength of self-adhesive flowable composite when used with acid etching or a self-etch adhesive system. Buccal enamel surfaces on 80 extracted human primary incisors were used and randomly assigned into four groups (n=20); group 1: Vertise™ Flow; group 2: Vertise Flow with acid etching; group 3: Vertise Flow with a self-etching bonding agent; group 4: Premise Flowable™ with a total-etch bonding agent as the control group. After 5000 rounds of thermocycling, the bond strength test was performed using a universal testing machine at a crosshead speed of 0.5 mm/min. The fracture analyzes of samples were evaluated using a light stereomicroscope. The results obtained were analyzed via analysis of variance (ANOVA) and Tukey’s tests. Statistically significant differences were observed among all groups (P<0.001). Group 1 generated a lower mean shear bond strength (2.63±1.08 MPa) than those of the other groups [group 2 (7.52±2.14 MPa), group 3 (5.12±2.93 MPa), and group 4 (14.18±2.93 MPa)]. Adhesive failure was the most common failure mode in Vertise Flow groups. Vertise Flow used with a self-etching agent or acid etching exhibited in lower shear bond strength than the control group.
Keywords
Dental materials, Primary teeth, Self-adhesive flowable composite, Shear bond strength, Vertise™ flow
İSMAİL HOCAOĞLU
Abstract
Today, materials are produced with nanotechnology, which are new products as a result of the development of technology. For cement-based composites, porosity is very important in terms of the strength and durability of the material after the material hardens. Today, with the innovations in technology, new materials are produced in the construction sector. New generation materials are produced on nano-meter scale using nanotechnology. These materials are used in cement-based composites to reduce porosity and improve durability properties. This research is aimed to reduce the porosity of the mortars by adding the nanomaterial graphene oxide (GO) to cement-based mortars whose sizes are 4cm x 4cm x 16cm. To investigate the effect of graphene oxide on porosity, series were produced as water/cement ratios are 0.55, 0.70, 0.90, and 1.00, by substituting 0.025 % GO in the mortars instead of cement. Besides, to investigate the effect of DC stress intensity on porosity, 25 V DC current is applied to all series. Mortar internal temperatures were measured from the beginning of hydration reactions in fresh mortars. Various comparisons have been made by calculating the maturity values of the mortars. Hardened mortars were cured for 7 and 28 days, then current passes on the mortars were measured by using an ampere meter. It has been investigated whether a relationship can be established between flow transfer and porosity. As a result of this study, the porosity of mortars can be reduced and maturity values can be increased by adding GO to cement-based mortars and applying DC current. In addition, porosity of cement-based materials can be estimated by using electrical methods.
Keywords
Nanomaterial; Graphene oxide; DC current; Porosity; Electrical measurement
NICOLAE CONSTANTIN, ADRIAN IOANA, DANIELA TUFEANU, LUCIAN PĂUNESCU, DRAGOȘ FLORIN MARCU, BOGDAN FLOREA
Abstract
The paper presents experimental results obtained in the manufacturing process of a glass foam obtained from the recycling of glass from cathode ray tubes (CRT). The glass foam samples were performed experimentally by the sintering-foaming process. The heating technique was unconventional, the energy provided by the microwave was used as a heat source. The process is different from the conventional techniques applied both in the manufacture of industrial glass foam and in the numerous small-scale experiments known in the literature. The glass foam samples obtained were characterized by traditional methods of analysis. The main characteristics were bulk density, porosity, thermal conductivity, compressive strength, water absorption and microstructural configuration of the samples. The experimental results proved that the applied process obtained a glass foam with good characteristics (porosity of 90%, thermal conductivity of 0.042 W / m-1 • K-1 and compressive strength of 2.1 MPa) usable in construction.
Keywords
separation, recycling, glass waste, microwave field
AZHAR BADAOUI , M’HAMMED BADAOUI
Abstract
The industry poses many problems to the disposal of waste materials; the impact on the environment and space occupied by storage sites. It is necessary to find a way to valorize and re-use this waste to protect the environment.
The research aims to apply a probabilistic approach to the simple leaching of mortars based on mineral fines of industrial by-products such as marble powder by pure or low mineralized water to maximize its recycling in the formulation of cementitious matrix building materials and to solve ecological and economic problems. The leaching phenomenon is studied using a probabilistic approach in this article. The statistics of the dissolving front in the material are investigated using a parametric approach that takes into account the variation of the mortar’s calcium diffusion coefficient porosity. A lognormal probability distribution is used in Monte Carlo simulations. In comparison to solely deterministic studies, the study found that probabilistic approaches are effective tools coupled with adequate deterministic models, providing extra information. As a result, concrete buildings may be better tailored for specific service life and environmental conditions.
Keywords
leaching; coefficient of variation, simulation, mortar, marble waste
DENG CHEN , TAO YANG, KAI-WEI LIU, AI-GUO WANG
Abstract
The effects of dolomite powder (DM) with different fineness on the hydration of Portland cement (PC) are investigated by using a multi-method approach. Results show that the addition of DM decreases the hydration heat and compressive strength of PC. However, at the same replacement of PC by DM, the hydration heat and compressive strength can increase with increasing the fineness of DM. When cured at 20 °C, an increase in the fineness and amount of DM can promote the formation of carboaluminate due to the improvement of the reaction degree of DM. When cured at 60 °C, hydrotalcite (Ht) is observed in the samples containing DM, and Ht may be formed in the surface layer of DM particles. With the increase of the DM fineness and amount, the Ht strongly increases.
Keywords
dolomite powder; fineness; hydration products; curing temperatures
R. TUĞRUL ERDEM , MURAT BERBEROĞLU
Abstract
Grout mortars are non-permeable, non-shrink and flowing cement based construction materials. Due to reaching high strength values in a short time, grout mortars are used in construction works. However, behavior of cement mortars under sudden impact loading is complex. Because, loading duration is very short in impact scenarios, effect of strain rates is much higher than static loading. So, dynamic responses and failure modes of the materials are different. In this study, it is aimed to investigate the dynamic behavior of slabs that are produced by cement based grout mortars under impact loading. A drop test setup is developed for this purpose and several measurement devices utilized in the impact experiments. Acceleration, displacement and impact load values are obtained as well as drop durations and drop numbers. After completing the experimental part of the study, artificial neural networks (ANN) analysis which is used to model different physical dynamic processes depending on the experimental variables is performed to predict the impact results. So, ANN analysis is used in the verification of experimental study. Due to the comparison of experimental and analysis results, it is considered that proposed ANN model can be used for the evaluation of the dynamic responses of test specimens.
Keywords
ANN; drop test setup; grout mortars; impact; slabs
S.S.VIVEK
Abstract
In the present research, ternary blended Self Compacting Concrete (SCC) was prepared to evaluate the performance by replacing cement with the Silica Fume (SF) from 5% to 20% and ground granulated blast furnace slag (GGBS) from 20% to 60% in the total percentage of the weight of the cement. An attempt was made to study the performance of fresh concrete by slump flow test, T-500, U-box and L-box test, and the hardened properties of concrete by cube compression and cylinder split tensile test. The superplasticizer and stabilizer were added in optimum dosages to prevent the segregation and bleeding of fresh concrete. More powder content, say 60% GGBS and varying SF from 5% to 20%, as cement replacement for ternary blended SCC has obtained better fresh property behaviour. But lower content of GGBS, say 20% blended with SF 10% and SF 15% obtained higher split tensile and compressive strength, respectively.
Keywords
Self Compacting Concrete, Silica Fume, GGBS, EFNARC, Compressive strength
ALI NAJM ABED ALMAGSOOSI, DAN PAUL GEORGESCU, ION RADU PASCU
Abstract
In the past years, it has commonly seen the use of Carbon Fibers Reinforced Polymer (CFRP) externally bonded as an active technique for strengthening and repairing of deficient existing concrete columns. Accurate design models for FRP – confined concrete are required to help engineers to design suitable FRP jacket and manage the cost-effective solutions for strengthening or repairing. In this paper the evaluating of the ultimate load carrying capacities of confined square concrete columns obtained from design models are presented. Five theoretical design models, provided in codes and researchers including: ACI 440.2R-2017; FIB Bulletin-90-2019; CNR-DT 200 R1-2013; Lam and Teng model (2003) and Ouyang and Liu model (2007) have been evaluated. A comparison was made between the load carrying capacities obtained from the experimental test data and the capacities obtained from the theoretical predictions results by the mentioned codes and researchers. All three models presented by Codes showed a good agreement with experimental values except for FIB Bulletin-90-2019 that showed conservative values in two confinement cases, while Lam and Teng model showed good agreement with experimental values and Ouyang and Liu model showed conservative values with respect to the experimental values.
Keywords
FRP, concrete column, square section, confinement, load carrying capacity
P. AMSAYAZHI , K. SARAVANA RAJA MOHAN
Abstract
The strength, toughness and ductility of the High strength fiber reinforced concrete (HSFRC) is presented in this paper. the glass and polypropylene fibers are used in this study. The fiber volume fraction differs from 0.25 to 1.5. Single fibers and combined fibers in the concrete is added. From this entire study it can be understood that the hybrid fibers showed more strength, ductility and toughness when compared to the single fiber concrete. There was an increase of 67% in terms of ductility and 20% in terms of toughness in high strength hybrid fiber reinforced concrete (HSHFRC). Regression analysis is used to predict the strength, toughness and ductility of HSHFRC and HSFRC. The experimental and predicted results show a close agreement.
Keywords
Compressive strength, split tensile strength, Hybrid fiber reinforced concrete, High strength concrete, toughness, Displacement ductility.
L. J. SANJEEV KUMAR, P. BHUVANESHWARI
Abstract
The study concentrated on the resistance of lightweight concrete slabs against impact load using a low-velocity drop hammer impact test device. Coconut procured from nearby processing units has been observed to have high impact resistance on initial testing. The lesser density was achieved by replacing 30% of natural coarse aggregate with waste coconut shells (CS 30). In order to compensate for degradation in characteristic strength, cement was partially replaced with ultrafine Ground Granulated Blast Furnace Slag – GGBFS (Alccofine) in increasing percentage of 6% (CS 30 6A); 8% (CS 30 8A); 10% (CS 30 10A); 12% (CS 30 12A). Both strength tests (compressive strength, tensile strength, flexure strength, Impact strength) and durability tests (Water absorption, Porosity, Sorptivity, Acid resistance) were carried out for the combinations. Comparing the results, the optimum mix was fixed as CS 30 8A. Square slabs of 600 mm with 60 mm thickness were cast using the predesigned mix of M40 grade (slab-CC). Slab-CS 30 8A were cast using the optimum mix for the same dimensions. Low-velocity impact tests were performed on the slabs up to failure. Parametric analysis was carried out for crack pattern, energy absorption, crack resistance, ductility indices, crack resistance ratio for the slabs. Comparison of results shows that the coconut shell-based lightweight concrete slabs performed well under impact loading.
Keywords
Coconut shell; Ultrafine GGBFS; Light weight concrete; strength; durability; impact; parameter analysis
ABHIJIT WARUDKAR , S ELAVENIL
Abstract
Since the exploration of natural aggregate for construction is leading to environmental concerns, the development of sustainable construction materials, such as steel slag, is being promoted. Ecology gets threatened by the disposal issue of steel slag, as million tonnes of steel slags are produced as a by-product in steel industry. This investigation, analyze the potential of steel slag as a partial and complete replacement for coarse aggregates in cement concrete. It is seen that the inclusion of steel slag improves the abrasion resistance property of cement concrete. This study is strengthened by Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy analysis which is carried out on the basis experimental fallouts. It is concluded that, the use of steel slag improved compressive strength and the abrasion resistance property of cement concrete, that is applicable in flooring, pavements or in places where concrete surface being in contact with external forces and environment.
Keywords
Abrasion Resistance, Indian Standards 9284, Compressive strength, Steel slag mixed concrete
SANAA EL MALYH , AZZEDDINE BOUYAHYAOUI, TOUFIK CHERRADI, ANCUȚA ROTARU
Abstract
The externally bonded fiber-reinforced polymer is an innovative technique for enhancing the strength of masonry structures, however the link between fiber reinforced polymer (FRP) and the masonry presents the fragile zone. To improve the bond performance and to determine the influence of the unidirectional reinforcement bonded geometry on the local bond-slip behavior, this paper investigates the shear bond behavior of carbon fiber reinforced polymer (CFRP) laminate externally bonded to masonry prisms, to ameliorate their structural applications and to assess their effectiveness on the stress distribution and also on the load capacity along the bonded zone. The single-lap shear tests was performed on five unidirectional carbon fiber reinforced polymer laminate externally bonded on masonry prisms via epoxy adhesive. The failure modes and the displacement behavior analysis show that the strengthening system is most effective when enhancing the bonded surface, as it reduce the stress concentration along the bonded length and it increase the load bearing capacity .
Keywords
CFRP bond, masonry, fiber - reinforced polymer bond behavior, strengthening, single - lap shear test
J. SHANMUGA PRIYA , K. CHINNARAJU , V.JAGANATHAN
Abstract
This research studies self compacting concrete mixes with 0, 30, 40 and 50% fly ash as replacement which are internally cured with super absorbent polymer and lightweight expanded clay aggregates against Self Compacting Concrete which are conventionally cured by submerging in water for a specific period. The optimum dose of the Internal curing agent was determined based on the chemical shrinkage of cement paste and it was presoaked in the mixing water and incorporated at the time of mixing. Fresh properties like slump cone, V funnel and L box tests were made and the effect of fly ash and internal curing agent was reported. Properties like compressive strength and durability factors such as rate of water absorption and resistance to chloride penetration were studied. Also the relationship between compressive strength and chloride penetration was established. It was found that the addition of fly ash seems to be beneficial for self curing concrete specimens up to 40% in terms of strength and durability. Concrete internally cured with super absorbent polymer showed better performance when compared with concrete cured with clay aggregates.
Keywords
internal curing, self compacting concrete, durability, superabsorbent polymer, light weight expanded clay aggregate, fly ash, curing
ALINA MELINESCU, ENIKŐ VOLCEANOV , MIHAI EFTIMIE, ADRIAN VOLCEANOV, LAVINIA POPESCU, ROXANA TRUȘCĂ
Abstract
Electroless nickel is applied to many types of substrates to take advantage of the coating`s properties. The final electroless nickel-based deposit quality is only as good as the quality of the base substrate metal since the coating`s ability to level or hide imperfections in the base material is poor. In fact, any defect in the substrate will be more visible after the part is plated with electroless nickel. A variety of contaminants include machining oils, drawing lubricants, buffing compounds, sulfurized oils, chlorinated oils, waxes, etc. Experimental work was carried out in order to establish the effectiveness of the method for degreasing thin low carbon steel strips before chemical coating. One alkaline (Solution A) and two acidic based on deoxidants (Solution B and Solution C) were tested at a temperature of 750C.
Before the chemical deposition of Ni-P și Ni-P-Al2O3 coatings, water break test was performed on steel substrate to evaluate the presence of hydrophobic contaminants, which can be detrimental to adhesion of coatings. Nickel sulphate hexahydrate was used as the source of nickel and sodium hypophosphite was used as the reducing agent, which also serves as the source of phosphorus in the coating. Sodium acetate, ammonium sulphate, sodium citrate, sodium dodecyl sulphate and lead acetate were used as additives in the plating bath, to accelerate the rate of deposition of the coating or as stabilizers to prevent the decomposition of the plating bath. During plating (45 minutes), the temperature of the bath was maintained at 80 oC using a constant temperature bath and the pH of the bath was maintained at 5.2.
The waterbreak test has been used to evaluate how clean a surface may be. The test is based on the ability of a properly cleaned surface to retain an unbroken film or sheet of water. Normally, dirty surfaces show a water break.
The samples of thin steel strip before and after deposition electroless Ni-P and Ni-P-nano - Al2O3 layers were characterized regarding the chemical composition, layer thickness, macroscopic appearance, uniformity and adhesion.
The chemical composition of steel substrate and of the layers was determined by X-ray Fluorescence. In order to investigate the morphology and microcomposition of metallic substrate and of deposition layers and thickness coating for the samples were studied by using Scanning Electron Microscope coupled with Energy-Dispersive X-ray Spectroscopy
Keywords
electroless plating, steel surface pretreatment, Ni-P and Ni-P-Al2O3 composite coating
ENIKŐ VOLCEANOV, MIHAI EFTIMIE , ALINA MELINESCU, ADRIAN VOLCEANOV, ADRIAN SURDU
Abstract
This work emphasizes on the development of electroless nickel composite coatings with the incorporation of oxide nanosized hard particles embedded in Ni-P matrix to improve their performance. The preparation of electroless nickel composite coating bath, methods to introduce hard particles in the bath, factors that affect the particle incorporation in the coating and its effect on coating structure is discussed in detail. The nickel-phosphorus coatings alloy layer was deposited by an autocatalytic process, without external power input is from this point of view an major advantage over electrolytic nickel plating technology. However, the autocatalytic Ni-P coatings deposition has a drawback, namely the low speed of layer deposition. Our investigations were focused on enhancing the deposition speed and homogeneity of the Ni – P –XO coatings, where XO is a mixture of Al2O3 + ZrO2, nanoparticles (ratio of 95: 5 by weight) deposited on low carbon content steel strip substrates
The chemical cell (bath) was formulated for 10/L oxides admixture and then connected by immersing the pre-treated steel substrate in the electroless bath solution for 15, 30, 45 and 60 minutes, respectively. The pH of the solution was kept between 4.58 and 6.23. The temperature was controlled in the bath in 60 oC -98oC range. Different stirring intensities in 50 - 400 rpm range were tested. There was almost no difference between Ni-P coating adherence versus Ni-P-(Al2O3+ZrO2) coating obtained by electroless plating. Moreover, electroless plating have nearly constant coating thickness across all surfaces, including edges and complex interior geometry. Nodularity of the Ni-P globules is reduced due to incorporation of second phase oxide nanoparticles.
Keywords
Electroless Composite Coatings, Nickel, Nano-sized oxide powders, Process Parameters
I.GOMOIU , M. ENACHE, S. NEAGU , R. RUGINESCU, M. DUMBRĂVICIAN, R. RADVAN, L. GHERVASE, I. MOHANU, R. COJOC
Abstract
The development of effective and non-destructive conservation strategies is based on understanding the role of microorganisms as biodeteriogens and their metabolites in biocleaning and biological control. An efficient alternative to traditional strategy in restoration is biorestoration based on different green biotechnologies where microorganisms and their enzymes are main actors. They are used both in bioconsolidation due to their ability to produce calcium carbonate precipitation and biocleaning. Microorganisms are used as viable cells brushed on the art works or embedded in carriers. Biorestoration is characterized by low cost and invasiveness, high specificity, easy control, non-toxicity for restorers and friendly for environment. Due to the fact that biorestoration has advantages and disadvantages, a better information of conservators and restorers in the use of the biotechnologies applied to restoration and conservation together with new results on optimizing the biocleaning and bioconsolidation about microorganisms, enzymes and bioactive molecules is needed. They will contribute to technological transfer on a large scale.
Keywords
microorganisms, biotechnologies, biconsolidation, biocleaning, biological control, mural paintings, stone
IONELA ANDREEA NEACȘU , LILIA MATEI, ALEXANDRA CĂTĂLINA BÎRCĂ, ADRIAN IONUȚ NICOARĂ, VLADIMIR LUCIAN ENE, LAURA DENISA DRAGU, ANTON FICAI, CORALIA BLEOTU, ECATERINA ANDRONESCU
Abstract
The purpose of this study was to obtain and characterize curcumin-loaded hydroxyapatite materials for bone cancer treatment. The hydroxyapatite synthesis was performed under controlled conditions in order to obtain monodisperse, fine nanoparticles and to avoid later uncontrolled deposition of these nanoparticles, starting from Ca(OH)2 and (NH4)2HPO4. The obtained dried precipitate was thermal treated, then suspended in curcumin – dichloromethane solution (where curcumin was added in order to represent 5%, 10% wt. from the amount of hydroxyapatite) and homogenized until solvent evaporation. Morphological and structural characterization, as well as in vitro characterization were performed. All samples were biologically tested and antitumor studies were performed.
Keywords
bone cancer treatment, curcumin, hydroxyapatite
MARIA PREDA, ILEANA RĂU, ALINA CORNELIA BACIU, CRISTIAN COVACIU, ALINA MELINESCU
Abstract
Tialite (Al2TiO5) is a known compound for its excellent mechanical properties and it is used in many fields. However, it should be noted that this compound has a very good chemical stability against silicate melts, so lately it has been used for obtaining ceramic pigments. In this paper, three samples were synthesized in the ternary pseudosystem MgAl2O4-CoAl2O4-Al2TiO5, which were heat treated at temperatures between 1200 and 1450°C. The mineralogical composition of the samples was determined by X-ray diffraction. The pigments obtained were introduced into the matte glaze in a proportion of 2%. The chromatic characterization both pigments and the coloured glaze was realised by the CIELab method.
Keywords
aluminium titanate, pigment, DRX, CIELab
HAJAR KADDOURI, TOUFIK CHERRADI, IBTISSAM KOURDOU, ANCUȚA ROTARU, NICOLAE ȚĂRANU, MARINELA BĂRBUȚĂ
Abstract
Externally bonded composite systems constructed of textiles with high mechanical strength and embedded in a mortar matrix, known as Fabric Reinforced Cementitious Matrix (FRCM) have received significant attention since they are promising solutions for the strengthening of historical structures. The mechanical characterization of FRCM systems is of fundamental importance to define the appropriate parameters needed to design a strengthening intervention. Nevertheless, improved knowledge still needs to be gained on their tensile behaviour and incidence over structural performance. The purpose of this paper is to investigate the mechanical behaviour of Glass FRCM samples subjected to tensile tests. In this context, the effect of fabrics overlapped with system global behaviour is analyzed in this paper. The tensile tests were carried out on Glass FRCM coupons with different fabric overlap lengths, varying between 100 mm and 200 mm. The objective is to determine the minimum fabric overlap length required to maintain fabric continuity and to avoid the loss of tensile strength in FRCM samples.
Keywords
Composite materials; FRCM; overlap; tensile test; strengthening
IAKOV ISKHAKOV, YURI RIBAKOV
Abstract
Creep is a well-known property of concrete elements, which cannot be avoided. It is defined as an increase in deformations over time due to constant stresses at uniaxial compression. In general, linear and non-linear creep of concrete elements are considered. However, there are no strong dependences that govern these two types of creep. It is still not clear when linear creep becomes non-linear, how creep changes the concrete modulus of elasticity, which energy is dissipated by the concrete section at linear and non-linear creep, etc. Predicted creep values are important for accurate design of concrete elements at service and ultimate limit states. The present study analyzes linear and non-linear creep and proposes a creep effect algorithm. The methodology is based on Structural Phenomenon and new theoretical concepts, using just one empirical coefficient related to non-linear creep. It can be used by engineers in order to perform more accurate and rather simple design of concrete elements considering creep.
Keywords
concrete creep; linear and non-linear creep; elastic and elastic-plastic potential of an RC system at creep; Structural Phenomenon
K. SARUMATHI , S. ELAVENIL, M. SATISH REDDY
Abstract
When the sand can no longer be reused in the foundry, it is removed from the foundry and this high quality silica sand in large volumes is used in making concrete as partial replacement of fine aggregate. In this paper investigations were carried out on the mechanical properties and durability studies of concrete by adopting silica sand and fly ash during the formation of concrete where, fly ash is used as a partial replacement material of cement. Silica sand (SS) or foundry sand (FS) is incorporated (0%, 25% and 50%) along with fly ash (FA) in different proportions (0% and 25%) with water – cement ratio (w/c) as 0.5. The outcomes indicated that the inclusion of FA and SS improved the compressive as well as tensile strength of material. The study reveals the feasibility of using spent foundry sand as a partial replacement of M-sand and also that full factorial design method is a reliable tool to arrive the conclusion that the FA and SS can be replaced with 25% effectively. The statistical software was used with full factorial design to predict the values and to validate the results with true values.
Keywords
CUVINTE CHEIE (ENGLEZĂ)
ARATHI KRISHNA , SARAVANA RAJA MOHAN KALIYAPERUMAL
Abstract
Reinforced concrete structures exposed to high temperatures may significantly reduce the characteristics of concrete in terms of strength, plastic deformation of reinforced steel bar and most precisely, the bond between the concrete and the reinforcing steel. Since there are only limited literature available in the field of concrete reinforced with hybrid fibres, which contain natural fibres subjected to elevated temperature, a thorough investigation needs to be done in this area. Hence, this investigation was carried out to evaluate the strength properties of concrete after adding different types of fibres under normal and elevated temperature conditions (27oC, 200oC, 400oC and 800oC). Micro steel, polypropylene and sisal fibres were used monolithically and in hybrid form with a volume fraction of 1%. The fresh property of the mixes was evaluated by conducting slump cone test, and the hardened properties were evaluated by density, compressive strength and split tensile strength tests. In addition, the bond between the concrete and the reinforcing bar was evaluated, and the residual properties were compared with the control mix. The results reveal that in elevated temperature conditions, the inclusion of micro steel fibres has a significant role in enhancing concrete strength and bond characteristics. The addition of polypropylene and sisal fibres mainly helps prevent spalling and has a slight effect on the bond characteristics of concrete compared to that of the control specimen subjected to elevated temperature.
Keywords
fibres; hybrid fibres; microsteel; polypropylene; sisal; strength properties; bond; pullout; elevated temperature
BEKİR ÇOMAK , ALPER BİDECİ, BATUHAN AYKANAT, ÖZLEM SALLİ BİDECİ
Abstract
With the development of computer technologies in recent years, the usage of image processing techniques in different areas have significantly increased. Image processing is the computer study for altering the measured or saved digital image data in a manner to fit for a purpose in an electronical media. In this study, by adding red iron oxide pigment (RIOP) into cement mortars in 2%, 4%, 6% and 8% ratios, physical and mechanical characteristics of the mortars were analysed, and color homogenization of them were determined by image processing method. On the manufactured samples, consistency, density, water absorption, porosity, compressive strength, flexural strength tests and image processing analysis by open source coded ImageJ programme were performed. Also, SEM-EDS analyses were performed in order to determine the inner structure characteristics of the samples. As a result of this study, changes in physical and mechanical characteristics of the mortars have been observed in different ratios. When it is desired to obtain a red colored mortar, it is determined by image processing analysis that 6% of red iron oxide pigment (RIOP) addition to the mortar mixture would give the optimum result.
Keywords
Color Concrete, Image Processing, Microstructures, SEM-EDS
V. JAGANATHAN , K. CHINNARAJU
Abstract
This study aims at simplifying the process of mix design of Self Compacting Concrete (SCC) which is generally done through trial and error. Concrete being a heterogeneous material, the desired qualities are attributed to several factors, in addition SCC has the requirement of better workability, which leads to the complexity in the design process. In this paper, the various factors affecting the strength and workability of SCC such as Total Cementitious Material (TCM) content, water-cementitious material ratio, percentage of fly ash replacement, coarse aggregate content and fine aggregate content were analyzed with four different values for each factor. Based on the Taguchi optimization method, an orthogonal array with sixteen experiments was designed to obtain the best factors for the SCC mix. The performance parameters selected were slump flow value for flowing ability, T5min of V funnel test for segregation resistance, L Box ratio for passing ability and compressive strength test for strength aspect. The results indicated that the TCM content and water-cementitious material ratio plays an important role in the workability of SCC, whereas TCM content and coarse aggregate content are predominant in the compressive strength of SCC.
Keywords
self-compacting concrete, Taguchi, orthogonal array, fly ash, workability
P.KAVIMUHIL, A.BALAJI, R.SOORAJ, V.VADHUL KRISHNAN, B.KARTHIKEYAN
Abstract
This paper discusses heavy density (HDC) concrete performance by partially replacing the fine and coarse aggregate in concrete with magnetite in its fine and coarser form. Three series of mixes, namely HDC-I, HDC-II and HDC-III, were developed for the research. HDC-I series contained 10% magnetite powder (MP) and 10% quartz powder (QP) as fine aggregates, whereas the HDC-II series had 15% magnetite power MP and 5% QP. The replacement level of magnetite aggregate as coarse aggregate was maintained constant by 30%, 40% and 50% for both the series. HDC-III series mix was made by replacing coarse aggregate with a significant content of 50%, 60% and 70% of magnetite aggregate by weight. Only 20% of magnetite powder was used for replacing the fine aggregate in HDC-III. Silica fume and nano-silica were also used in a constant replacement proportion in cement by 10% and 1%. Various tests related to the mechanical and durability characteristics of the concrete were performed. Compared with conventional concrete mix, the results revealed that increasing the proportion of magnetite aggregate leads to a considerable increase in unit weight and other mechanical properties. Also, it was observed that quartz powder and magnetite did not fetch any significant benefit in the mechanical properties.
Keywords
Heavy density concrete; magnetite powder; magnetite aggregate; quartz powder; nano-silica; aggressive environment; impact test
ASIF HAMEED, MOHSIN USMAN QURESHI, ALI MURTAZA RASOOL, JAVAID KHALID, ASADULLAH QAZI, MUHAMMAD USMAN RASHID, ZAFAR MAHMOOD
Abstract
Self-compacting concrete (SCC) can compact itself under its weight without any external effort and has characteristics of flowability, passing-ability, viscosity, inhibiting segregation and filling narrow architectural sections, etc. SCC requires a larger quantitative proportion of fines e.g. pozzolans like fly ash, blast furnace slag, silica fume, metakaolin, rice husk, or non-pozzolanic materials like limestone and sandstone. However, a higher quantity of pozzolanas with lower water content may cause autogenous shrinkage. The objective of this research is to find the best mix design of SCC to reach the highest compressive and flexural strength while maintaining flowability, passing ability, and segregation resistance. For this purpose, first twenty-eight (28) mix designs were prepared and tested in a fresh state for assessing flowability, passing-ability, and segregation resistance properties. The results of these tests were found compatible with previous studies without any significant variations. Then, hardened concrete was tested by casting 448 cylinders for determining the compressive strength at 7, 14, 28, 56, and 90 days and 168 prisms were tested to determine the flexural strength at 28, 56, and 90 days. It was observed that two combinations i.e. 30%FA, 17.5%SF, and 25%FA, 7.5%SF replacement are the most favorable mineral fine admixtures in producing good quality SCC.
Keywords
Self-Compacting Concrete (SCC), Fly Ash (FA), Silica Fumes (SF), Pozzolans, Coefficient of Variance