Influence of Rice Straw Fibers on Concrete Strength and Drying Shrinkage

Fibers have been used in construction materials for centuries. This study investigated the impact of the addition of rice straw fibers (RSF) on the compressive and flexural strengths of concrete, drying shrinkage, and on the heat of cement hydration. RSF was saturated before being added to concrete. Addition of RSF in concrete reduced concrete strength, increased concrete drying shrinkage, and increased the induction period of cement hydration. It was suggested that water squeezed out of RSF during mixing and sample consolidation increased effective water-to-cement ratios (w/c) and resulted in reduction of concrete strength and increase of concrete drying shrinkage. The increase of retardation time was attributed to leaching of organic and inorganic compounds out of RSF into the pore solution. It was shown that samples containing washed RSF did not have noticeable improvement in compressive strength over samples containing unwashed (as received) RSF. However, samples containing washed RSF had lower drying shrinkage and shorter induction period compared to those containing unwashed RSF