Empirical Equations for Mechanical Properties of Ca(OH)2-Based Alkali-Activated Slag Concrete

The objective of this study is to provide a data bank and comprehensible design equations for the mechanical properties of calcium hydroxide (Ca(OH)(2))-based alkali-activated (AA) ground-granulated blast-furnace slag (GGBS) concrete. A total of 34 concrete mixtures were prepared in three groups with the parameters of water-binder ratio (w/b), fine aggregate to total aggregate ratio (S/A), and unit water content. As an alkali activator, S-type for a combination of 7.5% Ca(OH)(2) and 1% Na2SiO3 and C-type for a combination of 7.5% Ca(OH)(2) and 2% Na2CO3 were used in each concrete group. As the mechanical properties of Ca(OH)(2)-based AA GCBS concrete mostly disagreed with predictions obtained from the equations specified in ordinary portland cement (OPC) concrete code provisions, new equations were proposed based on the nonlinear multiple regression analysis using test data to establish a reliable mixture design procedure and provide a fundamental reference for the structural design of Ca(OH)(2)-based AA GCBS concrete. The compressive strength gain of Ca(OH)(2)-based AA GCBS concrete was formulated considering the influencing parameters, such as the type of activators, curing condition, w/b, and S/A. The mechanical properties, including moduli of elasticity and rupture, splitting and direct tensile strengths, shear strength, and bond strength were proposed as a power function of f(c)'. The compressive strength development and mechanical properties predicted front the proposed equations closely agreed with the test results, showing that the coefficient of variation of the ratios between experiments and predictions was mostly less than 0.1. In addition, the proposed formulas for the stress-strain relationship and the bond-slip relationship of Ca(OH)(2)-based AA GGBS concrete described the experimental response well.