english GONZÁLEZ-FÉLIX JULIO CESAR, MENDOZA-RANGEL JOSÉ MANUEL, DIAZ-PEÑA ISMAEL, FÉLIX-MEDINA JENNIFER VIANEY
Rezumat
The addition of Polypropylene Microfibers (PM) to an Ordinary Portland Cement (PC) based mortar with a substitution by weight of ground Fly Ash (FA) promotes a decrement of the angle of internal friction (Φ) in a cementitious matrix of the repair mortar and an increment of the cohesion (c) value in the interface between the substrate and the repair mortar zone. Mixtures samples were prepared by replacing cement by fly ash at 0% and 20% by weight, additions of polypropylene microfibers at 0% and 5% and compared with a reference mixture. The characterization of raw materials was carried out by Scanning Electron Microscopy (SEM) with Secondary Electrons (SE) for morphology, Backscattering Electrons (BE) for chemical composition and Energy Dispersive X-Ray Spectroscopy (EDS) for elemental analysis. Substrate and repair mortars were tested for compressive strength, indirect tensile strength, Young’s Modulus, Poisson Coefficient to study the mechanical behavior of the specimens. Electrical resistivity and carbonatation depth (concentration 4%, relative humidity 60 +/- 5%) were analyzed to study the durability of the samples. Samples with FA show a slightly decrement of the cohesion of the interface but samples with PM show an increment of this value, resulting in a higher cohesion with only PM. The use separately of FA and PM promote a lower angle of internal friction than reference samples. The results obtained under the experimental conditions used in this work, show that there is a synergistic effect between the use of polypropylene fibers and the pozzolanic material to reduce the carbonation depth caused using only the microfibers in the mixture.
Cuvinte cheie
cenușă zburătoare, mortar de reparații, proprietăți mecanice, microfibre de polipropilenă, durabilitate, materiale pe bază de ciment
SANG-SOON PARK
Rezumat
Concrete sewer pipe line is one of the important civil infrastructures. Since the concrete sewer pipe is buried underground, the deterioration could be serious problem in maintenance and the repair and replacement cost is very high. The main aggressive factor affecting the durability of concrete sewer pipe is chemical attack by chloride and sulfate, so the sulfate resistant concrete should be used for the construction of sewer pipe line. In this study, the feasibility for the application of ferronickel slag powder (FSP) as a supplementary cementing material (SCM) used to improve the performance of concrete sewer pipe was investigated and the experimental tests were performed with different replacement ratio and fineness to determine the optimum level of replacement securing the improved chemical resistance and durability. The improvement of durability and chemical resistance of FSP contained mortar was verified through accelerated chloride ion penetration test, chemical resistance test and microstructural analysis. The optimum replacement rate of FSP can be considered as 40 % to assure the durability of concrete sewer pipe.
Cuvinte cheie
conductă de scurgere din beton, pulbere de zgura din feronichel, durabilitate, rezistență chimică
SAFIA KHENGAOUI, MOULOUD ABDESSEMED, SAID KENAI, NOUREDDINE OUADAH
Rezumat
In many countries, linear infrastructures (roads, railways or airports) are the most efficient and advantageous means of transport for citizens. Some of these infrastructures, such as roads or runways, are made of concrete, and as they are exposed to repeated loads and weather conditions, cracks are forming and spreading throughout the pavement. Several repair techniques have been applied to ensure their continued use under various types of traffic. The repair technique of adding lightweight welded mesh or geosynthetic layers seems to be a suitable solution, given their mechanical and aesthetic performance. This paper presents an experimental study on the effect of wire mesh and geogrids on the reinforcement of rigid concrete pavements. Twenty-four (24) specimens of concrete slabs, unreinforced and reinforced with a combination of geogrid sheets and wire mesh, were fabricated and tested in four-point bending. Validation of the experimental results was obtained by applying the finite element method, using a commercial software. Non-destructive in situ tests with a heavy deflectometer (HWD) were carried out on the central part of a rigid runway located in southern Algeria (arid zone), before and after its reinforcement with geogrids. It was found that geogrids are more effective than wire mesh in terms of tensile strength, stress and displacement reduction and downward crack propagation, with percentages ranging from 15 to 30%.
Cuvinte cheie
pavaj, rigid, geogrid, plasă de sârmă, armătură, experimentare, HWD, numeric
RASIM CEM SAKA, HALIT YAZICI
Rezumat
In this study, LC30 structural lightweight concrete and LC60 high performance structural lightweight concrete were produced by using completely pumice aggregate. A total of 6 mixture designs were created by substituting 40% fly ash (FA) by weight into cement and adding 5.5 kg/m3 polypropylene fiber (PPF) to two different lightweight concrete designs. Flexural strength, compressive strength, total water absorption, electrical resistivity, rapid chloride ion penetrability tests were carried out on the produced concretes, and SEM-EDS analyzes were performed. As a result, lightweight structural concretes with a unit weight below 2000 kg/m3 could be produced by using 100% pumice aggregate, and LC60 high-performance lightweight concrete exhibited superior performance in all mechanical and physical tests compared to LC30 lightweight concrete. Since pumice has a porous structure, it has been confirmed by SEM images that there is a good interface between the aggregate and the matrix.
Cuvinte cheie
CUVINTE CHEIE (ROMÂNĂ)
DAN PAUL GEORGESCU, CLAUDIU MAZILU, ADELINA APOSTU, ALIN BARBU
Rezumat
Utilizarea agregatelor reciclate reprezintă o metodă eficientă și o componentă importantă pentru dezvoltarea sustenabilă a domeniului construcțiilor din beton armat. Având în vedere particularitățile betonului preparat cu agregate reciclate, legate de originea agregatelor dar în special de stratul de mortar aderent, în reglementările europene utilizarea acestora este restricționată în funcție de clasele de expunere ale betonului. Această limitare se datorează performanțelor inferioare privind durabilitatea betonului realizat cu agregate reciclate care în anumite cazuri necesită și o operațiune de pretratare. Cercetările efectuate, prezentate în acest articol, au scos în evidență particularitățile caracteristicilor de rezistență și durabilitate ale betonului preparat cu agregate reciclate cu și fără utilizarea microsilicei și a nanosilicei. Prin aplicarea unor metode experimentale de performanță pentru evaluarea durabilității betonului s-a putut optimiza compoziția betonului preparat cu agregate reciclate. De asemenea, în cazul utilizării silicei, s-a demonstrat îmbunătățirea performanțelor betonului și totodată posibilitatea sporirii procentului de agregate reciclate utilizate la prepararea acestuia, față de cel indicat în actualele reglementări.
Cuvinte cheie
betoane, micro și nanosilice, agregate reciclate ale betonului, durabilitate
Machine learning based prediction of compressive strength in concrete incorporating synthetic fibers
R. TUĞRUL ERDEM, AYBİKE ÖZYÜKSEL ÇİFTÇİOĞLU, ENGİN GÜCÜYEN, ERKAN KANTAR
Rezumat
Different types of fibers are added to the concrete mixture to improve its behavior under different loading cases. This study intends to investigate the compressive strength of concrete cubic samples in which synthetic macro fibers are added in different amounts. For this purpose, a total of 72 cubic samples are produced in the experimental program. Axial pressure test is applied to cubic samples and 7 and 28 days compressive strength values are obtained in the end. However, a lot of effort has been spent to complete the time-consuming laboratory tests. To overcome this situation, four machine learning methods—Xgboost, Random Forest, Decision Tree, and Multiple Linear Regression—are adapted for efficient compressive strength forecasting. Moreover, four metrics are employed for a more meaningful evaluation of models: R2, RMSE, MAE, and MAPE. Remarkably, all models achieved R2 values exceeding 90%, with Xgboost notably reaching an impressive R2 value of 97%. This highlights the effectiveness of integrating machine learning in predicting compressive strength, offering a viable alternative to traditional laboratory tests. Incorporating the Shapley Additive exPlanation (SHAP) method, the study provides a detailed analysis of the models interpretability. SHAP analysis revealed that "Day" and "Fiber" have been identified as crucial features influencing compressive strength predictions. Localized SHAP analyses for specific samples further enhanced the understanding of individual predictions, emphasizing the practicality and transparency of machine learning in structural engineering. The promising results of this study indicate the potential for further advancements in enhancing performance, utilizing machine learning insights.
Cuvinte cheie
beton, fibre sintetice, rezistență la compresiune, metode de învățare mașina, Xgboost
TAIZHI XIANG, PENG ZHAO, WEIXING HOU, HAIYOU SHEN, ZIQUAN ZHAI, JINYUAN WANG, XINCHAO YE
Rezumat
The development of Sea Water Sea Sand Concrete (SWSSC) holds critical importance for maritime engineering, especially given China s extensive marine resources and the potential they represent. Despite its promise, the utilization of SWSSC has been impeded by the corrosive nature of certain ions present within its constituents. The depletion of freshwater river sand coupled with advancements in construction material technology has reignited interest in SWSSC, prompting a reassessment of its viability. This review delineates the achievements in developing SWSSC, examining both the microstructural and macroscopic properties of key Supplementary Cementitious Materials (SCMs) such as seawater, sea sand, cement, fibers, and mineral admixtures. Each material s benefits and drawbacks are critically analyzed, with a focus on how they influence the concrete s durability and structural integrity. Furthermore, the review identifies existing gaps in research and offers direction for future investigations aimed at overcoming the challenges posed by corrosive elements and optimizing material properties for enhanced performance. The integration of innovative materials and techniques is proposed as a means to advance the practical application of SWSSC in building resilient marine infrastructure.
Cuvinte cheie
Beton din nisip de apa de mare (SWSSC), ciment, materiale cimentitice suplimentare (SCMs), fibre
AWADHESH SRIVASTAVA, ABHISHEK MISHRA, SACHIN KUMAR SINGH
Rezumat
The escalating construction activities have led to a significant environmental pollution due to the CO2 emission from cement industry. To address this issue, this study explored the incorporation of waste plastic polypropylene (PP) fibers at 1%, 2%, 3%, and 4% by weight of cement, combined with 2% nano titanium dioxide (TiO2). The objective was to assess how these plastic fibers influence the mechanical and physical properties of concrete. Investigation focused on various concrete properties, including water absorption, compressive, split tensile and flexural strength, as well as on non-destructive testing (NDT) to validate the destructive test. High magnification scanning electron microscopy (SEM) images were used to analyze the morphology of the concrete samples after 28 days of curing with different fiber percentages. The study revealed that all concrete mix achieved the mean target strength in compression. However, increment in the flexural strength approximately 34%, and the split tensile strength increased by about 18.18% with the addition of 2% nano TiO2 and 2% plastic fibers. 2% nano TiO2 with 1 to 2% PP fiber, gives the desired result in mechanical properties and microstructural properties.
Cuvinte cheie
beton armat cu fibre, nano-materiale, rezistență la compresiune, rezistență la rupere, ductilitate, test non-distructiv
R. KARTHIKEYAN, C.HARIHARASUDHAN, M.SIVAKUMAR, K.SUGUNA, K.K.GAAYATHIRI
Rezumat
This effort attempt to determine the durability of microsilica- zeolite based concrete. The study s main variables, zeolite and silica fume, were substituted for cement in the proper ratios: 5%, 10%, and 15% of zeolite and 10% of constant micro- silica. A total of 36 control specimens were cast and tested for this work, including cubes (150 x 150 x 150 mm), cylinders (100 mm × 200 mm) . Nine of the thirty-six control specimens are standard concrete specimens. The final 27 specimens were constructed using microsilica-zeolite based concrete. The experimental results clearly demonstrate that the addition of micro-silica and zeolite significantly enhances the durability characteristics of ternary blended concrete, including water absorption, resistance to acid attack, porosity, and carbonation depth. Moreover, incorporating micro-silica and zeolite into concrete mixtures not only improves the material s durability properties but also provides an environmentally friendly alternative to traditional cement-based mixtures.
Cuvinte cheie
beton amestecat, adâncime de carbonatare, micro-silice, zeolit, durabilitate, rezistență
ZHICHENG LIU, YICHAO ZHANG, LI SUN, XUAN LI, FENGRUI ZHANG, HUANG LI
Rezumat
Mesoscale numerical simulations can provide a more intuitive and accurate characterisation of the mechanical behaviour of recycled concrete. This study entailed the development of a mesoscopic finite element model for recycled concrete by using mesoscopic CT images of recycled concrete and mesoscopic image processing techniques. An analysis of uniaxial compression damage characteristics of recycled concrete was performed. The results indicate that the development of a refined mesoscopic finite element model can be realised with a combination of histogram equalisation, image segmental transformation, median filtering and noise removal, morphological image processing, Canny edge detection, and image vectorisation techniques. In addition, the basic mechanical properties and stress–strain curve of recycled concrete under uniaxial compression obtained from the mesoscopic finite element model are in good agreement with the experimental results. Tensile stress concentration at the interfacial transition zone (ITZ), which is the leading cause of damage in recycled concrete, was exhibited when the axial stress reaches the compressive strength of recycled concrete. Under loading, the interface ITZ3 between the recycled aggregate and old mortar, was the first to show damage, followed by ITZ2, which is the interface between the new mortar and old mortar. ITZ1, which is the interface between the recycled aggregate and new mortar, was the last to show damage. This indicates that the mechanical properties of ITZ3 are relatively weak, the mechanical properties of ITZ1 are relatively strong. The mechanical properties of the ITZs have a direct impact on the compressive strength of recycled concrete.
Cuvinte cheie
beton reciclat, compresiune uniaxială, caracteristici de deteriorare, mezo-scală, simulare numerică
J. SHANMUGAPRIYA, P. KRISHNA KUMAR, S. GEETHA, S. SIVARAMAKRISHNAN, M.SELVAKUMAR, A. KANDASAMY
Rezumat
The present study relates to creating a simplified approach for the mix design of Internally cured Self Compacting Concrete under ambient curing conditions when fly ash is used as a supplementary cementitious material. A simple and novel approach for the Mix design of internally cured SCC with fly ash has been attempted in the study. The study helps in designing a robust mix design of SCC that could provide better workability and compressive strength even under poor or adverse curing conditions. A nomogram to determine the cement content, efficiency factor of fly ash and water content required for SCC have been developed and also nomograms for determining the internal curing water requirements have been developed for medium strength SCC with fly ash replacements up to 50%. A sample mix design for a fly ash replacement percentage of 35% and a Total Cementitious Material Content of 500 kg/m3 has been worked out and validated through the results of workability and compressive strength. Hence, this approach of mix design can be used as a ready-reckoner for proportioning a mix design for Internally cured Self compacting concrete of medium strength provided the percentage of fly ash replacement is decided and the characteristics of the internal curing material is known.
Cuvinte cheie
proiectarea amestecului, nomogramă, întărire internă, beton autocompactant, factor de eficiență
LAKSHMI R, KATHIRVEL P, PRASANNAN D, SAKTHIVEL E
Rezumat
This study presents the effect of Nano Silica and Metakaolin as additive materials in developing High Performance Concrete substituted with Super Absorbent Polymer (SAP) as an internal curing agent. Mechanical properties were evaluated by conducting compressive, tensile, and flexural strength tests and a Modulus of Elasticity test. Microstructural (Sorptivity and Scanning Electron Microscopy) tests were carried out to investigate the influence of additive materials on HPC mixes to investigate the hydration products. The results revealed that Nano Silica and Metakaolin have a high pozzolanic character, which increases the packing density of concrete and facilitates impermeability. It is inferred that using 10% of Metakaolin and 3% of Nano silica in weight replacement of cement could accelerate the strength improvement at an early stage of hydration and increase the concrete s resistance to meet the demands of corrosion resistance and water permeability.
Cuvinte cheie
nanosilice, beton de înaltă performanță, polimer super absorbant, întărire internă, caracteristici rezistență, durabilitate
HÜLYA TEMİZER, ÖZLEM ÇAVDAR
Rezumat
In this study, fly ash (FA) from Sivas/Kangal thermal power plant and blast furnace slag (BFS) from Bolu cement industry were used as the main binder materials. Based on both the literature and preliminary tests, samples were prepared with 85% blast furnace slag and 15% fly ash (85BFS15FA) as the main binder. In addition, the effect of geopolymer main binders and different additives such as mine waste, marble powder, and titanium dioxide were evaluated under various working conditions. The aim was to observe the effect of three different levels and 6 different parameters on the geopolymer samples using the Taguchi optimization method. Accordingly, the L27 orthogonal matrix was created. Three different molar ratios (8M, 10M, 12M) of sodium hydroxide (NaOH) solution and sodium silicate (Na2SiO3) solution were used as alkaline activators. Physical and some mechanical tests such as flexural strength, compressive strength, water absorption, and void ratio were performed on the 7, 28, 56, and 90-day samples, and Taguchi and ANOVA statistical analyses were performed on the 90-day samples. The highest compressive strength observed among 108 samples reached 65.75 MPa in the S20 samples (90-day). Taguchi and ANOVA statistical analyses identified curing temperature as the most significant parameter influencing the geopolymer samples. Additionally, the Signal to Noise ratio data indicated that the optimal curing temperature, determined to be the most effective based on the Larger is better criterion, was found to be 75 ̊C.
Cuvinte cheie
zgură de furnal, cenușă zburătoare, geopolimer, lianți deșeuri
ANANTHI A
Rezumat
The longevity of the buildings is determined by the durability of the concrete, which is its most important attribute. Weld slag was used as a fine aggregate in high performance fibre reinforced concrete (HPFRC) combinations, and their durability was evaluated. In order to generate sixteen series of HPFRC mixes (70 MPa), weld slag (WS) and various fibre fractions were utilized. There are various amounts of fibre (0%, 0.1%, 0.3%, and 0.6%) added to the weight of cement. Different amounts of weld slag (0%, 10%, 20%, and 30%) were used in place of the fine aggregate. The tests for corrosion, sorptivity, permeability, salt and sulphate attack, and water absorption are used to evaluate the HPFRC test specimens durability. The findings of the durability test show that the combination of employing up to 10% weld slag in place of fine aggregate and adding 0.3% fibre volume proportion is more durable.
Cuvinte cheie
beton de înaltă performanță, durabilitate, permeabilitate, atac sulfatic, coroziune
ÖZLEM ÖZKAN ÖNÜR, ÖZGÜR YERLİ
Rezumat
The construction technology, design, and materials of historical structures and their surroundings are among the most important documents of history. The use of original materials in maintenance and repair work is crucial for preserving these structures with their original qualities. In this study, the aim was to produce cement-free lime mortars for the sustainability of natural stones used in the floor covering of Topkapı Palace, one of the most important structures of cultural heritage. In mortar production, 30% air lime was used as a binder, along with varying ratios of brick fragments and dust, yellow sand, clay lime and quartz aggregate, fly ash, tooth snag water, glass fiber, and water. Physical and mechanical analyses of the produced mortars were conducted, as well as FESEM-EDS and XRD analyses for the internal structure of the materials. According to the analysis results, it was determined that the tooth snag water used instead of water had no mechanical effect on the mortars, while fly ash and glass fiber had positive effects on their physical and mechanical properties. These mortars, which have a calcite mineral structure, contain high amounts of Ca, C, O, Si, Mg, Al, and small amounts of Fe and S elements. It can be recommended to use glass fiber and fly ash added mortars, which have high porosity, low unit volume weight, and sufficient compressive strength, in the hard ground pedestrian paths of the structure.
Cuvinte cheie
material compozit, mortar de pardosele, împrejmuirea cladirilor istorice, var, puzzolană