english HADEL OBAIDI, AHLAM ABDUL-RHEEM FARHAN, TAHA H. ABOOD AL-SAADI
Rezumat
Since concrete is a consistently reliable building material, its importance to all nations economies cannot be overstated. However, the cement and concrete industries continue to generate massive amounts of waste which results in the emission of carbon dioxide which is one of the environmental issues. Therefore, reducing the amount of cement is important by partially replacing one of the waste materials. In this research; two municipal materials were used as alternatives for cement. It is considered available in quantities with appropriate price as compared to other mineral materials. In addition, this research was interest given to assess the strengths and durable behaviour of concrete production with these addition materials. The amount of metakaolin used is (1-15) wt% and alum (1-5) wt% of cement. The central composite design (CCD) method was used in conjunction with the response surface method to design concrete mixtures for this research and to analyse the results obtained from laboratory tests. An empirical model was given for compressive strength, bulk density and splitting tensile strength. All concrete specimens were cured after 7 and 28 days. The best results were found when metakaolin was used between (1-3) wt% and alum sludge between (1.6-3) wt% as mixed materials to produce concrete and as a partial replacement of cement.
Cuvinte cheie
metacaolin, deșeu de alaun, beton, software Minitab, rezistență la compresiune, rezistența la tractiune la despicare, durabilitate
RASIM CEM SAKA, SERKAN SUBASI, MUHAMMED MARASLI
Rezumat
The technical term GRC (glass fiber reinforced concrete) is widely used in the precast industry. This type of concrete, which is obtained by mixing cement, sand, glass fibers and some chemicals, is very durable. Compared to conventional concretes, high compressive, flexural and impact strength is the preferred choice for building facade coatings. In this paper, the usability of sepiolite as a pozzolan in glass fiber reinforced concrete and its effects on mechanical and physical properties were investigated. GRC samples were produced by adding 3% glass fiber by volume to substituted mixtures. Crude and calcined sepiolites were replaced with cement at 5%, 10%, 15% and 20% by weight. Compressive strength, flexural strength, impact strength and abrasion resistance of produced GRC samples were determined. As a result, It was observed that as sepiolite ratio increased, mechanical and physical properties of samples decreased in early and later ages, and crude sepiolite substituted samples had lower mechanical strength than the calcined sepiolite substituted samples.
Cuvinte cheie
fibră de sticlă, GRC, sepiolit, calcinare
AYED KADA, BENADOUDA MOURAD, BENMOKRETAR KARIM, KERDAL DJAMEL EDDINE
Rezumat
This study aims at evaluating the durability of self-compacting sand concrete (SCSC) based on pozzolan, brought from the north-western town of Beni-Saf (Algeria), with respect to the diffusion of chloride ions. The influence of the addition of a large amount of natural pozzolana on the diffusion of chloride ions in SCSC samples was studied in the first part of this paper. The compressive strengths of several SCSC samples, which were formulated with different percentages of natural pozzolana, were then compared with those of standard self-compacting concrete (SCC) and vibrated concrete (VC) in the second part. The experimental tests carried out on these formulations indicated that self-compacting sand concrete (SCSC) exhibits better mechanical behavior and also only a small number of chloride ions can penetrate in it as compared to other types of concrete. This study also showed that the partial substitution of cement in the SCSC by natural pozzolana from Beni-Saf improves its resistance to the diffusion of chloride ions.
Cuvinte cheie
beton autocompactant cu nisip, puzzolană naturală, rezistență mecanică, durabilitate, difuzia ionilor de clorură, porozitate, capilaritate
SUTHANKUMAR N, THANKA JEBARSAN V, PHANI MANOJ AV
Rezumat
The development of unique and high volume cement replacement concrete with enhanced strength and durability properties is attempted in the present study. In this paper, fresh and hardened state properties of concrete containing wollastonite and limesludge are used as cement replacements to attain a unique composition and several experiments such as determination of compressive strength, flexural strength, split tensile strength, water absorption, sorptivity, ultrasonic pulse velocity, charge passed, alkali silica reaction, scanning electron microscope studies coupled with EDX analysis (Energy Dispersive X-Ray Analysis) were performed. The results show that the size of mineral additions has a pre-dominant role on the reduction of ASR expansion. Among all the ternary blended mixes, the mix containing wollastonite at 15% with 5% LS showed increased strength and durability at all ages. This paper also emphasized the measurement of electrical resistivity behaviour of the series of wollastonite-limesludge mixes thereby showing enhanced bulk resistance of the concrete mixes
Cuvinte cheie
wollastonit, nămol de var, durabilitate, rezistență mecanică, microstructură
ALI OSAT AKBARI MOGHADDAM, ALI DELNAVAZ , SEYED AMIRHOSSEIN HASHEMI , SEYED HOOMAN GHASEMI
Rezumat
The purpose of this paper is to provide a model for predicting the corrosion process in concrete. This model is defined based on the simultaneous infiltration of chloride ions and the phenomenon of carbonation of concrete under certain environmental conditions. For this purpose, the simultaneous effect of chloride ion diffusion and carbonation phenomenon was studied using experiments on the fabricated samples. For this reason, in the first case, the samples are exposed to carbon dioxide once and then to chloride ions. In the latter case, only samples under the influence of chloride infiltration are examined. To make the samples, which include 9 mixing designs, three water-to-cement ratios of 0.35, 0.4 and 0.5 and three percent of 0%, 7% and 10% silica fume have been used. In this study, accelerated chloride ion (RCPT) penetration, capillary adsorption, pressurized water penetration and compressive strength tests of concrete were performed on the samples. Also in control and carbonate samples, the results of long-term experiments including chloride ion penetration and determination of chloride ion profile and determination of chloride ion diffusion coefficient have been investigated. The results of permeability tests show that carbonation has a direct effect on reducing the flow rate in the chloride ion permeation test and also reducing the capillary adsorption coefficient in the water capillary adsorption test. While increasing the ratio of water to cementations materials, the effect of carbonation on reducing the flow rate and also the capillary absorption coefficient of water increases, it should be noted that increasing the percentage of soot silica reduces this effect. Using linear fitting models on the results of long-term experiments, the amount of changes in chloride ion diffusion coefficient due to carbonation of concrete and determination of chloride ion concentration in concrete is presented.
Cuvinte cheie
carbonatare, coeficientul de difuzie al clorurii, beton, potozitate, silice ultrafină
SABINA SCRIPCĂ, MARINELA BĂRBUȚĂ
Rezumat
Scopul principal al acestui studiu este de a investiga impactul adaosurilor de microsilice și cenușă de termocentrală ca înlocuitori de ciment asupra modulului de elasticitate al betonului și microbetonului, precum și efectul fibrelor de metal și polipropilenă în acest context. Au fost proiectate diferite amestecuri de beton și microbeton, cu 5%, respectiv 10% microsilice sau cenușă de termocentrală ca înlocuitoare de ciment, cu și fără fibre metalice sau de polipropilenă. Modulul de elasticitate a fost determinat prin încercări de compresiune, iar rezultatele au fost analizate pentru a evalua efectele adaosurilor și fibrelor asupra modulului de elasticitate în comparație cu betonul tradițional. Conform rezultatelor obținute, s-a constatat că microsilicea și cenușă de termocentrală ca înlocuitoare de ciment pot îmbunătăți modulul de elasticitate al microbetonului în majoritatea cazurilor, în timp ce în cazul betonului s-au înregistrat doar câteva excepții cu un modul de elasticitate mai mare. Comparând valorile modulului de elasticitate din cele două seturi de date, se poate observa că valorile modulului de elasticitate ale microbetonului cu cenușă/silice sunt cu până la 27.03% mai mari decât cele ale betonului cu cenușă/silice. Tendința generală observată este că înlocuirea unei proporții mai mari de ciment cu microsilice și cenușă de termocentrală poate conduce la o scădere a modulului de elasticitate al betonului/microbetonului. În ceea ce privește fibrele, acestea nu au influențat semnificativ modulul de elasticitate al microbetonului și betonului cu cenușă sau silice, cu excepția fibrelor metalice care au avut un efect mai pronunțat în unele cazuri. În același timp, este important de menționat că adăugarea de fibre de polipropilenă a avut un efect negativ în anumite situații. În ceea ce privește clasa de rezistență, majoritatea betoanelor au fost încadrate în clasa de rezistență C12/15. Este esențial să evidențiem beneficiile înlocuirii cimentului cu cenușă sau microsilice în ceea ce privește reducerea costurilor și emisiilor de dioxid de carbon asociate producției de ciment. Prin urmare, utilizarea acestor adaosuri aduce multiple avantaje de mediu și, în același timp, păstrează sau îmbunătățește proprietățile betonului
Cuvinte cheie
Beton, cenușă zburătoare, microbeton, microsilice, modul de elasticitate, fibre
DENG CHEN , LI-WU MO, AI-GUO WANG, KAI-WEI LIU, TAO YANG, SHI-PING ZHANG, FEI SONG
Rezumat
This work focuses on the sulfate resistance performances of Portland cement (PC) incorporating different amounts (0~60 wt%) of dolomite powder (DM) pre-cured at different temperatures (20 °C and 60 °C). The results show that the PC-DM samples pre-cured at 20 °C for 28 d and then eroded by sulfate solution for 180 d exhibit the worse appearances and higher expansion values than the reference PC sample. On the opposite, the sulfate resistance performances of the PC-DM samples pre-cured at 60 °C are better than those of the PC sample. Furthermore, with the increase of the DM content, the sulfate resistance properties get better and better. The degradation of the pore structure may act as a major factor for the poor sulfate resistance of the PC-DM samples pre-cured at 20 °C. However, for the PC-DM samples pre-cured at 60 °C, the poor pore structure does not increase the risk of sulfate erosion. This is mainly due to that the formation of hydrotalcite (Ht) results in the decomposition of monosulfate, and SO42- may also be bound firmly by Ht in the PC-DM samples, thus contributing to the excellent sulfate resistance. Additionally, brucite can be identified in the PC-DM samples pre-cured at 60 °C, especially with high DM dosages (≥40 wt%).
Cuvinte cheie
praf de dolomit, atac sulfatic, structura porilor, hidrotalcit
SERGII KROVIAKOV , LUBOV SHESTAKOVA
Rezumat
Influence of basalt fiber and air-entraining admixture on the properties of rigid concrete pavement was investigated. Concretes without fiber and with 0.50, 0.75 and 1.0 kg/m3 fiber were produced. The amount of air-entraining admixture varied from 0 to 0.15% of the cement mass. Due to dispersed reinforcement, the compressive strength of concrete increased by 13-24%, and the tensile strength increased by 21-29%. The use of air-entraining admixture did not affect the tensile strength of concrete, but reduced compressive strength by 2-21%. Concrete without dispersed reinforcement and air-entraining admixture has a frost resistance F200. The use of basalt fiber increases the frost resistance of concrete up to F300. When using 0.05% air-entraining admixture, the frost resistance of concrete decreases, but when using 0.15% admixture, the frost resistance of concrete without fiber increases from F200 to F300. The air-entraining admixture does not affect the abrasion resistance of concrete, and the dispersed reinforcement reduces the abrasion resistance by 14-15%, which contributes to the increase in the durability of the pavement. The use of dispersed reinforcement and complex modification with polycarboxylate type superplasticizer and air-entraining admixture made it possible to obtain concrete for rigid concrete pavement with high durability and the required strength.
Cuvinte cheie
pavaj de beton rigid, fibre de bazalt, amestec cu antrenarea aerului,durabilitate, rezistență, rezistență la îngheț
NISHANT A NAIR, VISWANATHAN T S
Rezumat
This article aims to produce sustainable and durable mortar with help of wollastonite admixing with Pozzolan portland cement with and without nano-silica. Wollastonite was chosen for its flexural capacity and nano-silica for refining the pore matrix and improving the overall properties of the mortar matrix. At 3, 7, and 28 days, eight different mix proportions were investigated. The ease with which water moves through the mortar medium and also porosity parameters were used as durability indicators. Mechanical properties tested were compressive strength, flexural strength, and dynamic modulus of elasticity. Correlations of mechanical properties were found using a graphical method. X-Ray Diffraction (XRD) and Fourier Transform infra-red (FT-IR) spectroscopy were employed to characterize the samples taken from the fractured specimens. Pore radius was calculated with the help of sorptivity and permeable porosity values. In terms of mechanical and durability properties, wollastonite replacement at 10% and nano-silica replacement at 6% were found to be optimum.
Cuvinte cheie
wolastonit, nano-silice, sorptivitate, porozitate, raza porilor
SUBBIAN MAKESH KUMAR, SARANGAPANI CHITHRA
Rezumat
In the search for sustainable development in the field of the construction sector, scientific advancements in the use of alternative materials in Self-Compacting Concrete (SCC) are of primary interest among researchers. The present study also attempted to use industrial waste materials such as Fly Ash (FA), Cement Kiln Dust (CKD), and Ecosand (ES) in the preparation of SCC, optimizing their mixture formulation using Taguchi-based Grey Relational Analysis (GRA). Batch optimization trials were conducted using a Taguchi L9 orthogonal array with different replacement levels of CKD (5%, 10%, 15%), FA (25%, 30%, 35%), and ES (10%, 20%, 30%) in SCC. Fresh properties, including slump flow, T500 time, V funnel time, L box passing ratio, and J ring step height, as well as hardened properties like compressive strength, flexural strength, and split tensile strength, were considered as responses. The Taguchi-based GRA results revealed an optimized mixture composition of 53 kg/m3 CKD, 184 kg/m3 FA, and 84 kg/m3 ES. Furthermore, a confirmation test was carried out to validate the model, and the error percentage was found to be less than 10%. ANOVA results indicated that the influencing parameters followed the order of CKD > ES > FA. Based on these findings, Taguchi-based GRA can be considered an ideal tool for optimizing concrete mixes.
Cuvinte cheie
optimizare multi răspuns, Taguchi bazată analiza relatională Gray, beton autocompactant, pulbere de ciment din cuptor, nisip
R. JEYA PRAKASH, B. SOUNDARA, K.S. ELANGO, S. CHRISTIAN JOHNSON
Rezumat
Due to Infrastructure development city streets are being covered with concrete pavements in which it makes the pavement surface impermeable. During monsoon period, the importance of counter action against the stormwater runoff develops a stress among the Central and the State Governments of India. It also attracts the attention of the Road and Transport officials mainly because of the difficulties faced with poor drainage system during heavy intensity of rainfall. The productive application of pervious concrete includes its usage for light volume transportation and it also diminishes the additional design for stormwater drainage. This concrete also holds potential to accommodate shoulders in heavy traffic roadway transportation. The behaviour of pervious pavement under various loading scenario can be well understand using Finite Element Method Analysis (FEMA). For primary assessment of pervious concrete (PC) as pavements, computer modelling software is preferable and economical comparing to ground evaluation after installation. In this paper, a EverFE (Finite Element Analysis) tool has been used to develop and determine the loading characteristics of pervious pavement based on the experimental values obtained through preliminary studies.
Cuvinte cheie
pavaj din beton permeabil, beton permeabil armat cu fibre, încărcare critică, analiza elementului finit, stress, deflecție
LEONID DVORKIN, VADIM ZHITKOVSKY, YURI RIBAKOV
Rezumat
Reactive powder concrete (RPC) is an efficient type of fine-grained concrete with extreme strength and durability characteristics. The use of RPC allows the construction of such unique objects as pedestrian and automobile bridges, thin-walled architectural forms, protective structures, hazardous waste storage facilities, etc. Obtaining RPC provides for the mandatory use of a significant amount of microsilica as an active mineral additive, which is not always available for use. The article presents the results of comparing the strength characteristics of RPC obtained on microsilica and with its complete replacement with fly ash activated by milling with sodium silicate fluoride. The studies were carried out using mathematical planning of the experiment. Experimental-statistical models of RPC water demand and compressive and flexural strength at different ages have been obtained and analyzed. It is shown that the use of activated ash in the RPC makes it possible to obtain concrete with a strength of 100...110 MPa in 28 days. A method for calculating the composition of the RPC using the obtained models is proposed.
Cuvinte cheie
beton fin reactiv, cenușă zburătoare, microsilice, planificarea experimentelor, modelul expermental statistic, putere, compoziție amestec beton, design
İSMAİL HOCAOĞLU
Rezumat
New construction materials have begun to be produced by using nano-technology. Nano aluminum oxide (nano-Al2O3) is known to have high electrical conductivity. In addition, nano-Al2O3 can increase the material s physical features and mechanical strength by spreading perfectly into cementitious composites like other nanomaterials. In this study, direct current (20V-DC) and alternating current (20V-AC) were applied to the nano-Al2O3-added to 300 dosage mortars (when they were fresh situation) for one day. It also investigated the mechanical-physical properties and microstructure of the mortars when nano-Al2O3 (0%, 1%, 1.5%, and 2% by weight instead of cement) was added. To determine the changes in the mortar s internal temperatures depending on DC and AC, the hydration temperatures of the mortars were measured every 60 seconds. It was observed that the optimum nano-Al2O3 ratio was 1%. It was also concluded that AC application was more effective in increasing the hydration temperature of the mortar. In terms of mechanical strength, It was seen that when DC-applied mortars were cured for 7 days and AC-applied mortars were cured for 28 days, they took higher values. Another result obtained from the study is that alternating cure improves the microstructure better than the direct current in cement-based materials.
Cuvinte cheie
oxid nanoaluminos, curent alternativ, curent direct, temperatură internă, microstructură