Physico-Mechanical and Hygro-Thermal Properties of Compressed Earth Blocks Stabilized with Industrial and Agro By-Product Binders.

Philbert Nshimiyimana,Adamah Messan,Luc Courard

doi:10.3390/ma13173769

Abstract

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.

Highlights

Despite its benefits on mechanical and durability properties, the stabilization of raw earthen material using cement is criticized for tempering with its natural advantages; i.e., low energy and carbon footprint, recyclability, moisture exchange capacity, and hygrothermal performances, among others [1,2,3]
The addition of 0–25% calcium carbide residue (CCR) decreased the bulk density of compressed earth blocks (CEBs) in the range of 1800 to 1477 kg/m3, following the increase of the total porosity in the range of 35–45% (Figure 2a)
The increase of the total porosity with the addition of CCR can be related to the optimum moisture content (OMC) for the production of stabilized CEBs which increased in the range of 17–23%

Summary

Introduction

Despite its benefits on mechanical and durability properties, the stabilization of raw earthen material using cement is criticized for tempering with its natural advantages; i.e., low energy and carbon footprint, recyclability, moisture exchange capacity, and hygrothermal performances, among others [1,2,3]. The compaction and/or incorporation of granulates or fibers can affect the mechanical and/or thermal performances due to their physico-mechanical effects in the earthen matrix This approach does not necessarily guarantee the earthen material to resist in contact with liquid water [8], mainly for the earth which has low inner cohesion. It opens up the opportunity of the addition of by-product binders from agriculture, industrial, or municipal wastes in the earthen construction material, in general, and compressed earth blocks (CEBs), in particular. The stabilization of earth was carried out by substitution of the cement and lime with by-product binders for improving the performances and sustainability of the raw earth [9]

Methods

Results

Conclusion