Mechanical properties and hydration behavior of dehydrated cement paste-slag based composite cementitious material

Abstract

Mechanical properties are critical in engineering applications involving cementitious materials. While dehydrated cement paste-based materials are considered environmentally friendly, they suffer from poor mechanical properties, limiting their engineering applications. Therefore, enhancing the mechanical properties of these materials is crucial to overcoming their limitations in engineering and supporting the development of sustainable building engineering. Based on the pozzolanic reaction mechanism and alkali activation theory, a composite cementitious material was created by combining dehydrated cement paste with slag. Na2SiO3 and NaAlO2 were used as alkali activators. The study investigated the effects of the ratio of dehydrated cement paste to slag, alkali activator dosage, water-binder ratio, and calcination temperature on the material’s mechanical properties through an orthogonal test. The optimized ratio, determined through the orthogonal test and mathematical model, resulted in a compressive strength of 37.33 MPa (7d) and 46.89 MPa (28d), surpassing the compressive strength of the original Portland cement paste. Hydration products of the composite cementitious material primarily comprised C-(A)-S-H, C-A-H, and CaCO3, with no observed presence of AFt, AFm, and Ca(OH)2. Notably, the hydration products of the composite material exhibited clear distinctions from those of Portland cement.