Properties of lightweight cement-based brick incorporating alkaline pretreated wheat straw

The compatibility between cement and straw is the main problem to produce the lightweight brick with satisfactory strength from cement and wheat straw. This study is conducted to explore an effective method to improve the properties of the lightweight cement-based material incorporating wheat straw. The effects of sodium hydroxide, sodium silicate and calcium chloride used as modifiers on wheat straw and cement paste are investigated with the evaluation of the physical and mechanical properties of lightweight bricks. The results indicate that sodium hydroxide pretreatment significantly enhances the compatibility between cement and wheat straw, but the prepared brick still has low strength. Combined with sodium hydroxide pretreatment, the sodium silicate as a surface modifier of wheat straw and calcium chloride as a hydration accelerator further improve the strength development of lightweight cement-based bricks, and calcium chloride has a stronger improvement effect than sodium silicate. Furthermore, the combined modification with sodium hydroxide, sodium silicate and calcium chloride is proposed, when the prepared lightweight brick with a wheat straw to cement ratio of 0.15 meets the requirement of MU5.0 strength grade specified in the Chinese standards and has satisfying thermal insulation and flame retardant ability.