The main objective of this study is to characterize the physico-chemical and mineral properties of clay materials from Burkina Faso to produce stabilized compressed earth blocks (CEBs). The reactivity of the clay materials was tested based on the electrical conductivity of solutions and the compressive strength of CEBs stabilized with 0-20 wt% CCR (calcium carbide residue) and cured for 45 days at 40±2 °C. Pabre and Kossodo respectively contain the highest fractions of clay (20-30%) and gravel (40%). Saaba and Pabre contain the highest content of kaolinite (60˗70%) and quartz (45-60%) and recorded the highest and lowest reactivity, respectively. The compressive strength of CEBs stabilized with 20% CCR improved tenfold (0.8 to 8.3 MPa) for Saaba and only 2.6 (2 to 7.1 MPa) for Pabre. The clay materials in the present study are suitable to produce CCRstabilized CEBs for load-bearing construction.

Earth stabilization, using two by-products available in Burkina Faso: Calcium Carbide Residue (CCR) and Rice Husk Ash (RHA), improved the performance of compressed earth blocks (CEBs). The effect of adding CCR or CCR: RHA (in various ratios) to the clayey earth was investigated. CEBs were molded by manually compressing moisturized mixtures of earthen materials and 0-15 % CCR or CCR: RHA (various ratios) with respect to the weight of earthen material. The results showed that, with 15 % CCR: RHA in 7: 3 ratio, the compressive strength of CEBs (6.6 MPa) is three times that of the CEBs containing 15 % CCR alone (2.2 MPa). This improvement was related to the pozzolanic reaction between CCR, clay and RHA. These CEBs comply with the requirement for wall construction of two-storey housing.

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This paper investigates the stabilization effect on compressed earth blocks (CEB) produced from quartz-kaolinite rich earthen material stabilized with 0% -25% calcium carbide residue (CCR). The paper evaluated various physico-thermal properties of the stabilized CEB and thermal comfort in the model building made of CEB masonry. The optical properties of CEB were evaluated from the mineral composition of the earthen material and CCR and apparent density of the CEB. A simulation was carried out on naturally ventilated model building whose masonry is made of CCR stabilized CEB comparing to the so-called conventional cementitious materials such as cement blocks and concrete. The results showed a decrease of the apparent density of the CEB from 2100 kg•m −3 for unstabilized CEB (0% CCR) to 1600 kg•m −3 for 25% CCR stabilized CEB. The thermal conductivity and depth of penetration of the heat flux on a 24 hours period of CEB respectively decreased from 1 W•m −1 •K −1 and 12.7 cm for 0% CCR-CEB to 0.5 W•m −1 •K −1 and 10.2 cm for 25% CCR-CEB. The emissivity, solar absorptivity and visible absorptivity of the CEB respectively decreased from 0.82, 0.82 and 0.82 for 0% CCR-CEB to 0.80, 0.64 and 0.64 for 25% CCR-CEB. The number of hours of warm and humid thermal discomfort was impacted for stabilized CEB based masonry in comparison with cement based masonry. The warm discomfort in building made of 20% CCR-CEB masonry was 400 hours lesser than that in building made of hollow cement blocks masonry.

This study investigated the effect of production and curing parameters on the mechanical performance of compressed earth blocks (CEBs) stabilized with 0-20 wt % CCR (calcium carbide residue). Kaolinite (K) and quartz (Q)-rich earthen materials were mixed with the CCR and used to mould CEBs at optimum moisture content (OMC) and OMC+2 % of the dry mixtures, cured at 20 °C, ambient temperature in the lab (30±5 °C) and 40 °C for 0-90 days. After curing, the reactivity of the materials and compressive strength of dry CEBs were tested. Increasing the moulding moisture from OMC to OMC+2 decreased the compressive strength 0.3 times (4.4 to 3.3 MPa) for the CEBs stabilized with 20 % CCR cured at 30±5 °C for 45 days. Similarly, the compressive strength (4.4 MPa) was reached by CEBs stabilized with 10 and 20 % CCR after 28 and 45 days of curing, respectively. At 40 °C, the compressive strength increased 3.3 times (1.1 to 4.7 MPa with 0 to 20 % CCR) for K-rich and 2.5 times (2 to 7.1 MPa) for Q˗rich materials. At 20 °C, the compressive strength increased only 1.3 times (1.1 to 2.5 MPa) for K˗rich and barely 0.7 times (2 to 3.4 MPa) for Q-rich materials. These suggest that CCR is useful for stabilization and improving the performances of CEBs in hot regions.

This study investigated the engineering properties of compressed earth blocks (CEBs) stabilized with by-product binders: calcium carbide residue (CCR) and rice husk ash (RHA). The dry mixtures were prepared using the earthen material and 0–25 wt% CCR, firstly, and 20 wt% CCR partially substituted by the RHA (CCR:RHA in 20:0–12:8 ratios), secondly. The appropriate amount of water was thoroughly mixed with the dry mixtures. The moistened mixtures were manually compressed into CEBs, cured, dried, and tested. The stabilization of CEBs with CCR increased the dry compressive strength (CS) from 1.1 MPa with 0% CCR to 4.3 MPa with 10% CCR and above; decreased the bulk density (ρb:1800–1475 kg/m3) and increased the total porosity (TP:35–45%). This resulted in the improvement of the coefficient of structural efficiency (CSE: 610–3050 Pa∙m3/kg). It also improved the thermal efficiency given the decrease of the thermal conductivity (λ: 1.02–0.69 W/m∙K), thermal diffusivity (a: 6.3 × 10−7 to 4.7 × 10−7 m²/s) and thermal penetration depth (δp: 0.13–0.11 m). The RHA further improved the CS up to 7 MPa, reaching the optimum with 16:4 CCR:RHA (ρb: 1575 kg/m3 and TP: 40%). The latter reached higher CSE (4460 Pa∙m3/kg) than cement stabilized CEBs (3540 Pa∙m3/kg). It reached lower λ (0.64 w/m∙K), a (4.1 × 10−7 m²/s) and δp (0.11 m) than cement CEBs (1.01 w/m∙K, 6.8 × 10−7 m²/s, and 0.14 m). Additionally, the stabilization of CEBs with by-products improved the moisture sorption capacity. The improvement of the structural and thermal efficiency of CEBs by the stabilization with by-product binders is beneficial for load-bearing capacity and thermal performances in multi-storey buildings.

This study investigated the hydric and durability performances of compressed earth blocks (CEBs) stabilized with calcium carbide residue (CCR) and rice husk ash (RHA). Dry mixtures were prepared using kaolinite-rich earthen material and 0 to 25 % CCR or 20:0 to 12:8 % CCR:RHA of the weight of earth. Moistened mixtures were manually compressed to produce CEBs (295x140x95 mm). Stabilized CEBs were cured at 30±5 °C, wrapped in plastic bags for 45 days. The cured CEBs were dried and tested for water absorption and other indicators of durability. Unstabilized CEBs immediately degraded in water. The stabilized CEBs were stable in water, with very low coefficient of capillary absorption (<20 g/cm².min 1/2 ) and excellent durability indicators. They resisted erosion at standard water pressure (50 kPa) and at a pressure of 500 kPa. The coefficient of surface abrasion improved far higher than 7 cm²/g recommended for the construction of facing masonry. It also increased after wetting-drying 2 cycles and correlated with the evolution of compressive strength. This correlation can be used as the non-destructive test of stabilized CEBs.

Municipal wastes such as water sachets and agricultural by-products in Burkina Faso need proper management to limit their hazards to the environment. This study investigated the effect of incorporation of fibres from agricultural by-products (okra plant fibre) and water sachet wastes (polymer fibre) on thermophysical and mechanical properties of stabilized compressed earth blocks (CEBs). The CEBs were moulded from moistened mixtures of clayey earthen material stabilized with 10 wt.% CCR (calcium carbide residue) and incorporated with 0 to 1.2 wt.% fibre of each type. The CEBs were cured in a closed environment, at room temperature in the lab (30 ± 5°C) for 45 days. Cured CEBs were dried (40 ± 2°C) and tested for the thermophysical and mechanical properties. The experimental results showed that the average bulk density of CEBs decreased in the range of 1690-1565 kg/m 3 with the incorporation of 0-1.2% fibre. The thermal conductivity and diffusivity also decreased, respectively, in the ranges of 0.84 to 0.63 W/m.K and 6.1E-7 to 4.2E-7 m 2 /s with plant fibres and 0.84 to 0.38 W/m.K and 54E-7 to 2.3E-7 m 2 /s with polymer fibres. This resulted in evolution of the depth of penetration of the thermal flux from 0.12 to 0.07 m which is smaller than the total thickness of the CEBs (0.14 m). This shows the improvement of the thermal performance of the CEBs incorporated with fibres in the context of the warm climate of Burkina Faso. However, the dry and wet compressive strength respectively decreased from 4.3 to 2.9 MPa and 2.7 to 1.3 MPa, which were respectively greater than 2 and 1 MPa required for the construction of non-load bearing buildings. These results suggest that CEBs containing by-product fibres are useful to improve the thermal efficiency of one-storey building.