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