Eco-recycled cement’s effect on the microstructure and hygroscopic behaviour of compressed stabilised earth blocks

Abstract

Recycled cement (RCP) retrieved from old cement waste aims to replace carbon-intensive ordinary Portland cement (OPC) in earth stabilisation, improving the mechanical performance and durability of earth construction, without significantly compromising its ecological character and thermophysical properties. This study analyses the microstructure and hygroscopic behaviour of compressed earth blocks (CEB) stabilised with RC. In addition, soil was partially replaced with construction and demolition waste (CDW) to further improve the CEB sustainability. To this end, the sorption-desorption isothermal behaviour of CEB with different soils, types and contents of stabiliser (0–10 % RCP or OPC), and varying percentage replacements of OPC with RCP (20, 50, 100 %) or soil with CDW (0, 15, 25 %) was analysed and related to their microstructure, which was characterised in terms of scanning electron microscopy, mercury intrusion porosimetry and nitrogen adsorption analysis. Unstabilised and OPC CEB were considered for comparison purposes. The microstructure of CEB was refined after RCP stabilisation, which influenced their hygroscopicity and adsorption-desorption hysteresis. Depending on the clay content of the soil, stabilisation reduced or increased the hygroscopic capacity of CEB. After stabilisation, the water adsorption decreased up to 25 % in CEB with clayey soil and increased up to 22 % in CEB with sandy soil. However, the hygroscopic behaviour was not significantly affected by the type of stabiliser. The substitution of OPC with RCP increased the volume of water adsorption up to 3 %, due to its slightly finer porosity. RCP has proven to be effective as an earth stabiliser, leading to CEB with adsorption-desorption properties similar to those of OPC CEB.