Study On The Properties Of Hemp Straw Fiber Reinforced Cement-based Composites

With the increasing awareness of environmental protection and renewable resources utilization,the research of lightweight and high-toughness agricultural straw reinforced cement composites has become a hot spot.In order to solve the problems of high density and poor toughness of cement composites,hemp straw fiber was used as a reinforcing material,the effects of particle size and content of hemp straw fiber on the properties of cement composites were studied.Under the optimal particle size and the add amount,the PVA polymer emulsion was used to enhance and modify the composites.The response mechanism model of the particle size and content of straw fiber to the flexural strength of composite was established to predict and control the flexural strength of straw fiber cement composite.Through analyzing the cross section morphology,hydration products,physical and mechanical properties,the effects of particle size and content on the properties of hemp straw fiber reinforced cement composites were studied.The results show that,the mesh number of straw fibers has an effect on the internal compactness of the composite.When the particle size is 10 mesh and the blending amount is 12%,straw fiber has better reinforcing effect on materials,the flexural strength and specific strength of the composite are 2.57MPa and 2.39N·m/g,respectively,the flexural toughness of the composite is 2.45 times of that of the pure cement sample.Under the optimized particle size and dosage of straw fiber,the effect of the amount of PVA polymer emulsion on the properties of composites was studied.The results showed that,the polymer emulsion had a better improvement on the properties of the composites when the content was 40%.The flexural strength,specific strength and flexural toughness of the modified composites were 3.01 MPa,2.88N·m/g and 1.53,respectively,which were 17.17%,20.50%and 33.17%higher than those of the unmodified sample,the interfacial bond between straw fiber and cement was improved.The three dimensional random distribution of straw fiber with different diameter was observed in the composite,and the reinforcement coefficient of straw fiber with 10 mesh diameter was the highest.The model was established based on the particle size and blending amount of straw fiber,and the flexural strength of composite material was predicted under different straw fiber particle size and blending amount.The prediction error of the model was less than 9.81%,and the predicted results were in good agreement with the experimental results.