Physico-mechanical and durability characterization of earthen plaster stabilized with fermented rice husk for coating adobe walls

Abstract

The present study aims to study the effect of fermented rice husk (RH) on earth plaster for coating and improving the durability of adobe walls. The mixtures of clayey earthen materials and 0%, 33%, 50%, and 67% of fermented RH of the total volume of the mixture are studied to assess their physicomechanical and durability properties. The RH is previously fermented separately in water for the periods of 2, 3, and 3 weeks. The pastes obtained after mixing the clayey earth material and fermented RH were used to mold 4 × 4 × 16 cm³ test specimens. The specimens were dried under ambient laboratory conditions $(32\pm 5^{\circ }\mathit{C}$ and 35$\pm 5\mathrm{\%}$HR) for 21 days before their characterization. The clay earthen material mainly contains silt (51%), clay (24%), sand (23%), and gravel (3%). It has a liquidity limit, plasticity index, and methylene blue value of 32%, 20%, and 2.66, respectively. The results show that apparent density, linear shrinkage, resistance to compression, and the thermal conductivity of the plaster specimens, respectively, decrease from 1.88 to 1.07 g/cm³, 4.52 to 0.83%, 3.88 to 0.82 MPa, and 0.87 to 0.05 W/m.K with increasing volumetric content of RH from 0% to 67%. Moreover, the resistance to abrasion increased. The resistance to capillary water absorption and water erosion was deficient for the content of RH above 50%. The mixture containing up to 33% of RH allows to improve engineering performances and reaches acceptable durability and would therefore be useful for coating adobe walls.

Keywords:

• earthen plaster
• rice husk
• clay
• fermentation
• adobe coating
• physico-mechanical property
• durability

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by African Development Bank (AfDB) under the grant “Nelson Mandela Institutes-African Institutions of Science and Technology”.