Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Effect of compression casting technique on the water absorption characteristics of low grade 100% Recycled Aggregate Concrete (RAC) of target strength range 11 to 15 MPa to be used in the manufacturing of masonry units is investigated. Water absorption characteristics were determined by performing sorptivity test. Recycled aggregates were produced by crushing laboratory-tested concrete samples of strength ranging from 21 MPa to 28 MPa. Two different ratios of recycled coarse aggregate and recycled fine aggregates were investigated using two different cement contents. For comparison, natural aggregate concrete mixes were also tested. The study parameter included effect of aggregates type, casting pressure, casting technique and cement content on the water absorption properties of RAC. Further, depth of penetration of salt was observed using silver nitrate solution after 3-month immersion in 10% NaCl solution. The results of sorptivity test showed positive impact of compression casting technique on water absorption properties of low grade 100% RAC. Further, results showed that RAC mixes exhibited inferior water absorption properties compared to natural aggregates concrete mixes. Various equations were proposed to predict water absorption of 100% RAC under different conditions of casting pressure and cement content based on initial and secondary rate of water absorption.

This study compares the rutting and cracking resistance and fatigue parameters of crumb rubber (CR) modified warm asphalt binders, which were determined by viscoelastic continuum damage (VECD) theory. The effect of the combination of CR modification and Sasobit, a warm mix additive, was investigated. Performance of CR + Sasobit compound was compared with styrene-butadiene-styrene (SBS) modification. Newly developed rheological tests such as multi stress creep recovery (MSCR), lineer amplitude sweep (LAS) and conventional tests were applied to modified binders.  It was determined that the CR + Sasobit modified binders improved the rutting parameter better in comparison to SBS-added binders. Although the CR additive improved the rheological properties of the binder at low and medium temperatures, this effect was reduced when used with Sasobit additive. Sasobit additive increased the stiffness and decreased the fatigue parameter at low temperatures. Besides, the results of the LAS test revealed that at high strain values ​​(i.e.> 6%), the fatigue life of CR and Sasobit modified binders was lower than the fatigue life of the pure binder. In other words, CR and Sasobit modified binders could not preserve material integrity.

In this study, roller compacted concrete was produced by using a modified lignosulfonate-based chemical admixture which is suitable for use in wet, semi-dry or zero slump concrete, and the effect of admixture dosage on the physical and mechanical properties of the concrete was investigated. In the production of roller compacted concrete, the cement content was 300 kg/m3 and the chemical admixture dosages have been changed as 0%, 0.3%, 0.6% and 0.9%. Percentage of compactibility, total water absorption, unit weight, ultrasonic pulse velocity, dynamic modulus of elasticity, concrete compressive strength at the ages of 3 and 28 days were determined for the roller compacted concrete specimens. Roller compacted concrete with the lowest percentage of water absorption, the highest percentage of compactibility, ultrasonic pulse velocity, compactness, compressive strength and dynamic modulus of elasticity was the concrete produced with 0.6% admixture dosage. With the concrete design and the chemical admixture in question, it has been observed that the optimum dosage of chemical admixture for the production of the best quality concrete in terms of the concrete properties examined was 0.6%.

After the construction of the Keban Dam, some settlements with historical, cultural, and natural value were flooded. A scientific committee consisting of academicians and public authorities decided to the relocation of the buildings including the historical Çelebiağa Mosque. In this study, the seismic soil-structure interaction analysis of the historical Çelebiağa Mosque, which was dismantled and reconstructed in a separate region due to the construction of the Keban Dam was carried out. The analysis of the masonry mosque was performed with the SAP2000 finite element analysis software. The Winkler foundation model was used to idealize the soil environment on which the historical mosque was built. The effects of soil-structure interaction on historical masonry mosque were examined in terms of transmitted acceleration, response spectra, and lateral displacement at various heights of the structure. Depending on the results of the analysis, the effects of soil-structure interaction of a reconstructed historical masonry building were investigated. PGA was obtained as 0.51g at the flag level of the minaret under the Kocaeli earthquake and 0.94g under the Sivrice earthquake. Again, the maximum horizontal displacements of the minaret at the flag level were obtained as 11 cm and 8.5 cm under the Kocaeli and Sivrice earthquakes. The behavior of historical masonry structures under earthquake loads has been interpreted by considering the geological conditions.

This work presents a sustainable panel elaboration for housing interiors through banana fiber and peanut shells gathered from crop residues, consolidated with a polyester resin binder. A material characterization process was defined by forming three prototypes with different dosages. The prototypes performed physical and mechanical tests following recommendations from previous research and the standards. The results obtained were favorable regarding thermal transmittance percentages, achieving an average resistance comparable to non-structural medium density particleboard (MDP). Performance comparisons were also established, which depict the potential of these prototypes to contribute to the building industry, including the development of thermally comfortable environments.

This study assessed the effect of lightweight expanded clay aggregate (LECA) grain size and curing with polyethylene concrete curing film (PCCF) on microstructure, interfacial transition zone (ITZ), and compressive strength of structural lightweight aggregate concrete (LWAC) produced with two different Dmax (16 or 22.4 mm). To this end, 2 series of normal weight aggregate concretes (NWAC) and 6 series of LWAC incorporating 40% by vol. unprewetted LECA having (0-3, 3-8, or 8-16 mm) grain sizes were evaluated by using unit weight, compressive strength tests at 1, 7, and 28 days and SEM-EDX observations. Preventing the moisture loss from fresh concrete through PCCF curing had positive effects on compressive strength up to 14 and 9% for 1 and 28 days respectively. Shell thickness of LECA considerably increased with the decrease in LECA grain size. Thus, the compressive strength of LECA and LWAC increased by the decrease in LECA grain size. LWAC containing 0-3 mm LECA, achieved up to 21% higher compressive strength to weight ratio compared with the NWAC with the aid of the pozzolanic reactivity of fine LECA particles.

As the COVID-19 pandemic continues, construction projects have struggled to be completed. As such, it is necessary to find alternatives that optimize the limited human resources that can be working on construction sites. One alternative to do so is using multiskilled workers so workers can be reassigned to construction activities minimizing projects’ disruption due to workers getting contagion with COVID-19. This study simulates the influence of multiskilled workers in the development of a construction project in the context of the COVID-19 pandemic using an agent-based modeling approach. The aim of the study is to quantify the influence of multiskilled workers in the deficit of construction workers due to COVID-19. The proposed model generates six scenarios to include the uncertainty from limited data from the field due to the pandemic context to quantify the deficit of workers to develop a construction project. This study found that using multiskilled workers reduces the deficit of workers required to perform critical activities in construction projects. More specifically, it can reduce the average deficit of workers roughly in half when compared with the alternative of using only single-skilled workers, from 33.4% to 16.7% of deficit. Consequently, multiskilled workers represents an alternative for construction managers to deal with the disruption from COVID-19 in construction projects from a workforce management standpoint. Understanding alternatives to minimize the impacts of COVID-19 in construction projects may assist engineers and managers in applying strategies to develop construction projects accounting the limitations that COVID-19 places on construction sites. 

polymer balls can supply water to the mortar or concrete mixture when added during the initial stage of mixing the concrete ingredients. It supplies the absorbed water during the hydration process of concrete as an internal water source. Water Absorption polymers (WAP) can absorb water up to hundred times of their own weight. Using this idea, the concrete mixture has been prepared with WAP and without WAP (Control) and subjected to air curing and water curing respectively. In this work WAP has been added in two different percentages i.e., 2.5% and 5% of the weight of cement, and the hardened concrete has been subjected to compression load. The mechanical strength and the volumetric change of these mixes were compared with the water cured control mix (Concrete without WAP). From the result, it was concluded that the air-cured specimen showed strength of 30.37 MPa and 28.74 MPa for 2.5% and 5% of addition of WAP balls respectively.  This strength is about 99% and 94.2% of the strength of control water-cured specimen.  Results also showed that specimens in air behave for expansion while samples in the water acted for shrinkage. Experiment results also showed that air-cured concrete specimens with WAP balls show significant strength gain over a period of 84 days compared to water-cured normal concrete mix samples.

This paper focuses on serving twofold benefits for the environment by providing not only recycling of a waste material but also improving rutting performance of sand subgrade under cyclic traffic loads. In this context, a series of laboratory experiments have been conducted to benchmark the performance of commercially manufactured geotextile and palm tree pruning waste (PTPW) as soil improvement agents. Experimental results of the study were evaluated based on permanent (plastic), total, and elastic deformation, rut depth reduction (RDR), traffic benefit ratio (TBR), percentage of elastic deformation, and resilient modulus (MR). In the view of experimental results, geotextile and PTPW-reinforced sand subgrades demonstrated well performance in the sense of permanent and elastic deformations when compared to unreinforced case. It is also realized that the most satisfactory performance was obtained when geotextile or PTPW are located at a burial depth of both 50 mm and 100 mm. In that case, TBR values of geotextile and PTPW-reinforced subgrades were almost the same at 20 mm permanent deformation (i.e., 6.71 and 6.76, respectively). Furthermore, when the results were evaluated based on RDR, it is observed that geotextile and PTPW reinforcements reduced the rut depth at the rate of 49.31 % and 37.15 % at the end of 5000 load cycle, respectively.

In this study, the mechanical, thermal and porosity properties of mortar samples containing aerogel and silica fume under different curing conditions were investigated. For this purpose, 0%, 0.25% and 0.50% by weight of silica aerogel as a cement additive and 10% silica fume as an industrial waste material were incorporated in the cement mixtures. The prepared mortar samples were exposed to curing process in water, the wetting-drying effect and MgSO4 effect for 16 weeks. The highest thermal conductivity reduction of 31.2% was obtained from the water curing sample with silica fume addition at an aerogel content of 0.25%. Maximum compressive and flexural strengths were determined respectively from samples with silica fume addition at an aerogel content 0.50% as 74.5 MPa and no aerogel content as 11.3 MPa by wetting-drying curing. However, the lowest thermal conductivity coefficient was measured as 1.458 W/mK from the sample at an 0.25% aerogel content containing silica fume which completed the curing process under the influence of MgSO4 with a highest compressive strength increase by 24.6%.