Key parameters establishing alkali activation effects on stabilized rammed earth

Abstract

• Key parameters for the dosage of SRE with an optimized ceramic tile dust and carbide lime-based AAC. • Unique relationships linking mechanical performance to η/B iv ratio and curing periods of SRE with an alternative AAC. • Compacted sandy soil-CTP-CL blends optimized with a 3 molal NaOH solution. • Sodium-aluminum-substituted calcium silicate gel ((N,C)-A-S-H) in amorphous phase as the main cementitious reaction product in the SRE with the alternative AAC. Cement stabilized rammed earth construction using calcium-based materials (e.g., Portland cement), has been done for decades. However, consumption of Portland cement has increasing limitations, due to the significant CO 2 emissions and the energy, combustible fossils and mining extraction consumption. Alkali activated cements (AAC) are becoming a viable alternative to Portland cement, in several applications. This paper aims to assess the effectiveness of a particular type of AAC for the stabilization of a rammed sand. This alternative cement was obtained from ceramic tile powder (from construction and demolition waste – CDW), and carbide lime (from the production of acetylene gas). The experimental study was based on the mechanical performance and microstructure of the sand-cement and focused on the influence of the activator and curing period on compressive strength, shear modulus and durability of the sand-binder blends. X-ray diffraction (XRD), back-scattering electron microscopy (BSEM) and energy dispersive spectroscopy (EDS) were also performed to characterize the mineralogy and microstructure. The mechanical behavior was highly influenced by the presence of the activator, and an optimum 3 molal concentration was found. The mechanical performance was successfully correlated with the porosity/binder index. Mineralogical, microscopic and compositional data revealed the formation of a heterogeneous cementitious matrix, consisting of an amorphous aluminosilicate gel binding the sand particles and forming a structure significantly different from the type of structure obtained with the water-compacted material.