Slag cements are used to design grouts with high water-to-cement ratio and low permeability, to improve the physical and mechanical properties of permeable soils. Because of the variable physico-chemical properties of slag, it can be challenging to predict their behavior. Most research on slag reactivity involves low water-to-binder ratios in concrete and strength. This study investigates grouts with higher water-to-binder ratio of 6, for water resistant barriers executed using soilmixing or self-hardening slurry cut-off wall techniques, where the main engineering property is the hydraulic conductivity. The effect of slag composition on grout properties was studied at two water-to-binder ratios (0.5 and 6) and varying slag proportions, focusing on compressive strength and hydraulic conductivity. The results showed that higher water-to-binder ratios influence hydration, phase formation, and pore distribution, preventing the formation of portlandite. Isothermal calorimetry revealed that the silicate peak in sulfate-rich slag-based grout, linked to C-S-H and Ca(OH)2 formation, overlapped with the aluminate peak and appeared earlier, which was not observed at a water-to-binder ratio of 0.5. Higher water-to-binder ratio promoted the formation of ettringite due to high sulfate content, affecting compressive strength and pore distribution. Coarser pores in sulfate-rich slag-based grout led to low compressive strength and high permeability. In addition, results showed that the reactivity of slag could not be determined solely by its basicity index. The performance of slag-based grouts depends on sulfate content and short-term slag reactivity. However, the evaluation of long-term slag hydration is necessary to understand the potential influence of latent slag hydration on engineering properties and performance.

Alternative construction materials can allow the modern built environment to abide by sustainability and circularity. This snapshot review highlights some advances made in the stabilization of compressed earth blocks (CEB) using alternative binders in the context of Burkina Faso. The review put forward the considerations of the reactivity and processing of earth materials and binders to produce stabilized CEB. Moreover, it highlights the effects of the changes at chemico-micro-scale of materials to the macro-scale densification, strengthening, and hardening of stabilized CEB. Furthermore, it relates the physical and mechanical properties through the coefficient of structural efficiency and correlates the resistance to surface abrasion with the resistance to bulk compression of stabilized CEB. This could later be extended to the structural efficiency of CEB masonry and allow to easily assess the strength from the quasi-non-destructive test of abrasion.

Construction spoil (CS), a prevalent type of construction and demolition waste, is characterized by high production volumes and substantial stockpiles. It contaminates water, soil, and air, and it can also trigger natural disasters such as landslides and debris flows. With the advent of alkali activation technology, utilizing CS as a precursor for alkali-activated materials (AAMs) or supplementary cementitious materials (SCMs) presents a novel approach for managing this waste. Currently, the low reactivity of CS remains a significant constraint to its high-value-added resource utilization in the field of construction materials. Researchers have attempted various methods to enhance its reactivity, including grinding, calcination, and the addition of fluxing agents. However, there is no consensus on the optimal calcination temperature and alkali concentration, which significantly limits the large-scale application of CS. This study investigates the effects of the calcination temperature and alkali concentration on the mechanical properties of CS-cement mortar specimens and the ion dissolution performance of CS in alkali solutions. Mortar strength tests and ICP ion dissolution tests are conducted to quantitatively assess the reactivity of CS. The results indicate that, compared to uncalcined CS, the ion dissolution performance of calcined CS is significantly enhanced. The dissolution amounts of active aluminum, silicon, and calcium are increased by up to 420.06%, 195.81%, and 256.00%, respectively. The optimal calcination temperature for CS is determined to be 750 degrees C, and the most suitable alkali concentration is found to be 6 M. Furthermore, since the Al O bond is weaker and more easily broken than the Si O bond, the dissolution amount and release rate of active aluminum components in calcined CS are substantially higher than those of active silicon components. This finding indicates significant limitations in using CS solely as a precursor, emphasizing that an adequate supply of silicon and calcium sources is essential when preparing CS-dominated AAMs.

With the widespread use of geopolymer, the effective activation and utilization of thermally activated termite soils as alternative or eco-friendly material are great of interest. The present study investigated the use of calcined termite soils (TC) in geopolymer pastes and mortars as a precursor, while metakaolin (MK) was used as a reference material to prepare control samples. The physicochemical properties of both raw and calcined solid precursors as well as geopolymer pastes and mortars were characterized using various techniques, including BET, PSD, XRF, XRD, setting time, ICC, and SEM/EDS. Results showed that termite soil can be successfully employed as a starting material in geopolymer production. Pastes and mortars prepared using TC gave significant compressive strengths of 43.2 and 33.2 MPa, respectively, although they were approximately 26% and 6% lower than control samples made using MK. Based on the analytical studies, better mechanical performance of MK-based binders compared to TC-based ones is attributed to the presence of reactive phases within MK that promotes the geopolymerization resulting in the development of a stronger geopolymer network and better connectivity within the matrix. It can be concluded that TC can be considered as a suitable raw material for the production of geopolymer binder considering the availability and accessibility in certain regions.