Research on Compatibility of Wheat Straw and Portland Cement

Straw burning has become a serious risk for environment and security. It is very urgent to develop and research materials to utilize straws. The compatibility between straw and portland cement is a problem to be resolved for application of straw fiber in cement-based materials. In the experiment, samples of cement-based composites with untreated straw fiber and pretreated straw fiber were prepared and mechanical properties of specimens were tested. The compatibility between straw fiber and portland cement can be improved through pretreatment process that consists of dipping straw fiber in 4% NaOH solution for 12 hours, then rinsing and drying. In this process, substances in fiber harmful to cement hydration are leached furthest. The negative influences of straw fiber on setting and hardening of cement paste are eliminated. The pretreatment can optimize the mechanical properties of the composite. The strength of composite is not linearly relative to cement-to-water ratio, instead, there exists an optimal water-to-cement ratio, i.e. 0.60. The strength of cement-based straw fiber composite prepared in this ratio reaches maximum.