Experimental Study of Effect of Fly Ash on Self-Compacting Rammed Earth Construction Stabilized with Cement-Based Composites

Abstract

As an environmentally friendly construction technique, modern rammed earth generally stabilized with portland cement has attracted growing interest recently. In this study, cement-based composites (CSCN) consisting of cement, sodium silicate, and composite promoter were used for substituting portland cement, and the effect of fly ash was investigated by unconfined compressive strength (UCS) test, thermogravimetric analysis (TG), X-ray diffraction (XRD), and scanning electron microscope (SEM). Based on the theory of pozzolanic and dispersing (P&D) effects, the contribution of fly ash was regarded as an addition of CSCN, and the quantitative analysis of P&D effects defined as P&D factors was evaluated by the clay-water/CSCN ratio hypothesis. It was found that the P&D factors for both compressive strength and secant modulus varied with CSCN content and curing age. The models of different curing ages for predicting the strength and modulus of specimens stabilized with CSCN and fly ash were developed from the combination of P&D factors and clay-water/CSCN ratio. The precisions of P&D factors and prediction models were verified by comparing predicted results and experimental results, and the deviation was mostly within 10%. The mineralogical and microstructural analyses confirmed that the combination of pozzolanic and dispersing effect hypothesis could be appropriate to study the fly ash effects.