Publications

The influence of two types of polymeric admixture on the stress–strain (σ-ε) behavior of cement mortar is discussed in this article. The characteristics of cement mortars modified with two types of polymeric admixtures containing 0.20 percent (% wt.) were investigated. For early age (1 day) and 28-day curing periods, the σ-ε behavior of modified cement mortar with polymeric admixtures was investigated. Depending on the polymeric structure and content, adding polymeric admixture reduced the water/cement ratio (w/c) by 14.5 to 25.5 %. When 0.20 % of polymeric admixture was added to cement mortar, the compression strength improved by 72 % to 153 %. The cement mortar samples became brittle as the polymeric admixtures content increased. The amorphous gel fills the spaces between cement particles and sand particles, decreasing voids and porosity and improving the density of the cement mortar. To forecast the connection of the modified cement mortar with polymer, the nonlinear Vipulanandan p-q equation was used, and it was compared to the Farazdaghi- Harris-YD and Sinusoidal models. The compressive stress–strain models were evaluated using statistical methods, and nonlinear approaches were utilized to predict compressive strength as a function of water/cement ratio, curing age, and polymer quantity. The less complicated model, the Vipulanandan p-q model, already has a smaller sum of squares than the other two models. Therefore, the Vipulanandan p-q model is the best one.

Plain recycled aggregate concrete (RAC) struggles with issues of inferior mechanical strength and durability compared to equivalent natural aggregate concrete (NAC). The durability issues of RAC can be resolved by using mineral admixtures. In addition, the tensile strength deficiency of RAC can be supplemented with fiber reinforcement. In this study, the performance of RAC was evaluated with individual and combined incorporation of microfibers (i.e., glass fibers) and various potential waste mineral admixtures (steel slag, coal fly ash (class F), rice husk ash, and microsilica). The performance of RAC mixtures with fibers and minerals was appraised based on the results of mechanical and permeability-related durability properties. The results showed that generally, all mineral admixtures improved the efficiency of the microfibers in enhancing the mechanical performance of RAC. Notably, synergistic effects were observed in the splitting tensile and flexural strength of RAC due to the combined action of mineral admixtures and fibers. Microsilica and rice husk ash showed superior performance compared to other minerals in the mechanical properties of fiber-reinforced RAC, whereas slag and fly ash incorporation showed superior performance compared to silica fume and husk ash in the workability and chloride penetration resistance of RAC. The combined incorporation of microsilica and glass fibers can produce RAC that is notably stronger and more durable than conventional NAC.

This study applies a methodology to evaluate the ecotoxicological potential of raw materials and cement-based construction materials. In this study, natural aggregates and Portland cement were replaced with non-conventional recycled concrete aggregates (RA) and fly ash (FA), respectively, in the production of two concrete products alternative to conventional concrete (used as reference). The experimental program involved assessing both the chemical properties (non-metallic and metallic parameters) and ecotoxicity data (battery of tests with the luminescent bacterium Vibrio fischeri, the freshwater crustacean Daphnia magna, and the yeast Saccharomyces cerevisiae) of eluates obtained from leaching tests of RA, FA, and the three concrete mixes. Even though the results indicated that RA and FA have the ability to release some chemicals into the water and induce its alkalinisation, the respective eluate samples presented no or low levels of potential ecotoxicity. However, eluates from concrete mixes produced with a replacement ratio of Portland cement with 60% of FA and 100% of natural aggregates and produced with 60% of FA and 100% of RA were classified as clearly ecotoxic mainly towards Daphnia magna mobility. Therefore, raw materials with weak evidences of ecotoxicity could lead to the production of concrete products with high ecotoxicological potential. Overall, the results obtained highlight the importance of integrating data from the chemical and ecotoxicological characterization of materials’ eluate samples aiming to assess the possible environmental risk of the construction materials, namely of incorporating non-conventional raw materials in concrete, and contributing to achieve construction sustainability.

Tire rubber waste is globally accumulated every year. Therefore, a solution to this problem should be found since, if landfilled, it is not biodegradable and causes environmental issues. One of the most effective ways is recycling those wastes or using them as a replacement for normal aggregate in the concrete mixture, which has high impact resistance and toughness; thus, it will be a good choice. In this study, 135 data were collected from previous literature to develop a model for the prediction of rubberized concrete compressive strength; the database comprised different mixture proportions, the maximum size of the rubber (1-40 mm), and the rubber percentage (0-100%) replacing natural fine and coarse aggregates were among the input parameters in addition to cement content (380-500 kg/m

This research work proposed an economic and eco-efficient idea to supplement the ductility and durability of concrete by the simultaneous incorporation of several processed waste materials i.e., ground blast furnace slag (GBFS), recycled coarse aggregate (RCA), and coconut fibre (CF). Two concrete families were produced containing 0% and 100% coarse RCA. GBFS was incorporated as by 25% replacement for cement. CF was used as a fibre reinforcement at 0.25% volume fraction. The results revealed that the recycled-aggregate concrete (RAC) modified with GBFS, CF, and modified plasticizer dosage can attain similar or higher mechanical performance than unmodified natural-aggregate concrete (NAC). At a later age, the strength gain in RAC mixes due to 25% GBFS addition was found to be notably greater than that observed in NAC mixes. At 91 days, RAC containing 0.25% CF and 25% GBFS correspondingly showed 30.5% and 33% more flexural strength and splitting tensile strength, as compared to conventional plain NAC. GBFS inclusion can effectively eliminate the corrosion risk of medium-strength NAC and RAC and control the negative effects of CF incorporation on the durability of concrete. RAC with 0.25% CF and 25% GBFS yielded 1.5% and 16% lower water absorption than plain NAC, at 28 and 91 days, respectively. The modification of SP dosage can substantially enhance the strength and permeability-resistance of CF-reinforced RAC.

This experimental research investigates the effects of different nano-alumina (NA) percentages partially replaced with ground granulated blast slag (GGBS) and fly ash (FA) using a variety of tests, including compressive and flexural strengths, flowability, dry density, microstructural analysis (scanning electron microscope, energy dispersive spectrometer, thermogravimetry analysis), water absorption, and sorptivity at ages of 28 days. All mixture results were also contrasted with those obtained from a control mixture of 50% GGBS and 50% FA without NA. All of the mixtures had the same alkaline activator and solid base, and the proportion of sodium hydroxide solution (S.H)/sodium silicate solution (S.S) was 2.5; the molarity of S.H is 12 M. The aim of this research is to investigate the optimal percentages of NA that showed significant results. The mix containing 2% NA reached its maximum strength of 61.9 MPa at 28 days. The results show that the percentage of NA significantly influences alkali-activated mortar properties, including water absorption, which is affected differently at varying concentrations. The proposed alkali-activated mortar may offer stable substitutes for conventional building materials that are also environmentally friendly.