Nonlinear models to predict stress versus strain of early age strength of flowable ordinary Portland cement

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.