Integrated Experimental Assessment of Elastic Properties and Pore Structure Evolution in Alkali Activated Concrete

Alkali-activated concrete (AAC) presents a compelling and sustainable alternative to conventional Ordinary Portland Cement (OPC) concrete by utilizing industrial by-products such as ground granulated blast furnace slag (GGBS), thereby significantly curtailing carbon dioxide emissions and the depletion of natural limestone reserves. However, comprehensive evaluations of AAC must encompass not only short-term compressive strength but also vital elastic properties, such as the static modulus of elasticity and Poisson's ratio, alongside long-term deformation characteristics like drying shrinkage and dimensional creep. This experimental study systematically investigates the mechanical, elastic, and deformation behavior of GGBS-based alkali-activated concrete activated using sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). Two distinct sodium hydroxide molar concentrations (3M and 15M ) and two alkaline solution-to-binder ratios (0.25 and 0.30) were evaluated under ambient curing conditions. Furthermore, the modifying effects of calcium carbide (CC) at replacement levels of 2.5%, 5%, 7.5%, and 10%, alongside carboxymethyl cellulose (CMC), were rigorously assessed to understand their influence on matrix densification and rheological performance. The experimental results demonstrate that the 15M sodium hydroxide series combined with an alkaline solution-to-binder ratio of 0.25 yields superior mechanical performance and enhanced dimensional stability, registering a peak 28-day compressive strength of 64 MPa, a static modulus of elasticity of 47,322 MPa, and a minimized drying shrinkage of 0.302%.