The brittleness of plain concrete (PC) is a result of its lack of tensile strength and poor resistance to cracking, which in turn limits its potential uses. The addition of dispersed fibres into the binding material has been demonstrated to have a positive impact on the tensile properties of PC. Nevertheless, using new or engineered fibres in concrete significantly increases the overall cost and carbon footprint of concrete. Consequently, the main obstacle in creating environmentally friendly fibre-reinforced concrete is the traditional design process with energy-intensive materials. This study investigated how the engineering properties and life cycle impact of concrete were influenced by varying the volume fractions of jute fibre (JF). The impact of incorporating silica fume (SF) as a partial replacement of Portland cement was also studied. The studied parameters included mechanical behaviour, non-destructive durability indicators, and the life cycle impact of concrete using JF and SF. The efficiency of JF in mechanical performance improved with the increase in age and with the addition of SF. When using both SF and 0.3% JF, there was an improvement of around 28% in the compressive strength (CS). When 0.3% JF was added, in the presence and absence of SF, the splitting tensile strength (STS) improvement was around 20% and 40%, respectively. The addition of JF improved the residual flexural strength (FS) and flexural ductility of PC. The SF addition overcame the drawbacks of the poor resistance of JF-reinforced concrete (JFRC) against water absorption (WA) and rapid chloride ion penetration (RCIP).
Abstract In this study, a modified Artificial Neural Network (ANN) and Support Vector Regression (SVR) with three different optimization algorithms (Genetic, Salp Swarm and Grasshopper) were used to establish an accurate and easy-to-use module to predict the lateral pressure exerted by fresh concrete on formwork based on three main inputs, namely mix proportions (cement content, w/c, coarse aggregates, fine aggregates and admixture agent), casting rate, and height of specimens. The data have been obtained from 30 previously piloted experimental studies (resulted 113 samples). Achieved results for the model including all the input data provide the most excellent prediction of the exerted lateral pressure. Additionally, having different magnitudes of powder volume, aggregate volume and fluid content in the mix exposes different rising and descending in the lateral pressure outcomes. The results indicate that each model has its own advantages and disadvantages; however, the root mean square error values of the SVR models are lower than that of the ANN model. Additionally, the proposed models have been validated and all of them can accurately predict the lateral pressure of fresh concrete on the panel of the formwork.
This book is the result of a Special Issue published in Applied Sciences entitled "Low Binder Concrete and Mortars". The main aim of this work is to highlight practical approaches that facilitate the production of low binder content concrete and mortar with an acceptable level of technical performance (e.g., mechanical and durability) and environmental impacts (e.g., ecotoxicological and global warming). Its contents are organized in the following sections: Developing Zero-Cement Binder; Ecotoxicological and Chemical Characteristics of the Non-conventional Materials Used to Replace Cement and Natural Aggregates; Reduce the Environmental Impacts and Resources Use of Binders; Modify the Characteristics of the Cement-Based Materials; Low Binder Concrete On-Site Application; Sustainable Cement-Based Materials in Road Engineering.
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In this study, the impact of two types of polymers on the stress-strain (σ − ε) behaviour, elastic modulus and toughness of cement-based cementitious material. Cement paste modified with two types of polymer up to 0.06% (% wt) with an interval of 0.02% were tested. The σ − ε behaviour of modified cement with polymeric admixtures was examined for curing periods up to 28 days. Adding polymers improved the flowability of cement by 7% to 26%, but it decreased the water/cement ratio (w/c) by 12% to 43%, depending on the polymeric structure and its content. The nonlinear Vipulanandan p-q model was tested to predict the σ − ε relationship of the modified cement with polymers and was compared with the β model. The Vipulanandan p-q model and β model performance were evaluated by comparing with several functional models using residual error and root mean square error. The compression strength of cement increased by 107% to 257% when 0.06% of polymers were added to the cement. Modifying the cement with polymeric admixtures enhances cement's initial elastic modulus (Ei) by 23% to 240% according to polymeric admixture types, curing age (t), w/c and polymeric admixture percent. During the early curing time, the cement modified with polymeric admixture was able to withstand large deformations that mean increase the samples' ductility, but with increasing curing, the cement modified polymers become brittle and the strain at failure reduced. The modulus of elasticity and total toughness of the cement paste were correlated well with compressive strength.
