Experimental investigation on the influence of rice straw characteristics on the hygric, thermal and mechanical properties of straw-lime concretes

Abstract

The utilization of agricultural wastes in the construction sector has experienced impressive expansion due to the growing awareness of climate change. These materials provide a fascinating solution to reduce the energy demand and consequential carbon emissions, thanks to their attractive thermal, hygroscopic and environmental properties. In this context, the present study examines the impact of the characteristics of rice straw particles on the mechanical, hygric and thermal properties of straw concretes. The characterization of the concretes is mainly based on measurements of thermal conductivity, water vapor permeability, moisture buffering capacity, and mechanical properties. Several formulations are defined and tested by varying the type of straw particles and their sampling area on the stem. First, the impact of grinding process of rice straw on concretes incorporating these particles was evaluated. A comparison was made between concretes containing cut particles in the longitudinal direction with a tubular shape with concretes containing milled particles (flatter shape) of similar length. Then, the dependence of the physical and chemical properties of straw particles on their shape and sampling area on the stem is identified. The results showed that the properties of concretes are highly dependent on the shape and sampling area of straw particles. The dependence of the mechanical, thermal and hygric performances of concretes on the particles shape appears to be the most relevant parameter, while the variation in concrete performances based on sampling area is limited. Additionally, the results show that cut particles induce lighter and porous concretes compared to milled particles, leading to an attractive thermal conductivity, moisture buffering capacity and water vapor permeability, while decreasing the mechanical properties of concretes. It is also highlighted that particles extracted from the bottom of the stem exhibit excellent hygric properties, higher deformation capacity and lower thermal conductivity than particles from the top of the stem.