| China is a large agricultural country,which produces a huge amount of agricultural residues every year,but the utilization rate is very low,most of them are used as feed or burned on site,which wastes resources and pollutes the environment.How to make full use of agricultural residues to form high value-added materials and products is an urgent problem.Using agricultural residue straw as the main raw material to prepare Portland cement-based straw composite material can solve the problem of low utilization rate of agricultural residue straw to a certain extent,at the same time,it can effectively reduce a series of environmental and social impacts caused by burning straw.It has significant environmental and social significance to utilize waste,environmental protection and develop new materials.In this paper,the bulk density of different kinds and forms of straw fiber and cement was measured to calculate the amount of raw materials used in the test;then the effect of water cement ratio on the forming and mechanical properties of Portland cement-based straw composite was studied to determine the water cement ratio in the later test;then,for untreated straw fiber,the amount,type,form and other aspects were carried out Study on the influence of composite properties.On the basis of the above research,in order to reduce the influence of Retarder in straw fiber on cement matrix and enhance the interface between straw fiber and cement matrix,the pretreatment of straw fiber was studied.Sodium hydroxide,hydrogen peroxide,sodium silicate,ethanol,polyvinyl alcohol and silane coupling agent were used to pretreat the straw fiber,and the effects of different solution concentration and treatment time on the properties of the composite were studied.On the basis of single treatment liquid,two kinds of treatment liquid sodium hydroxide and silane coupling agent with different modification mechanism were selected to carry out composite treatment of straw fiber,and the properties of composite material prepared by composite treatment straw fiber and composite material prepared by single treatment were compared and analyzed.The results show that when the water cement ratio is 0.3,the sample can hardly be formed.When the water cement ratio is 0.5,the fiber floats up obviously.When the water cement ratio is 0.4,the physical and mechanical properties of the composite are ideal.When the water cement ratio is 0.4,the physical and Mechanical properties of the composite are ideal-The flexural strength of the composite made of 4cm corn straw fiber is higher than that of 2-3cm.When the water cement ratio is 0.4 and the content of 3-4cm corn straw fiber is50%,the highest flexural strength of the composite is 10.1MPa.The compressive strength of the composite made of 2-3cm corn straw fiber is higher than that of 3-4cm.When the water cement ratio is 0.4,the content of 2-3cm corn straw fiber is 50%,the highest compressive strength of the composite is 23.1MPa.When the water cement ratio is the same as that of straw,the content of straw fiber is 25%,the highest compressive strength of the composite is25.5MPa,and the content of the composite is 50% The strength of the composite made of rice straw fiber is higher,the highest is 9.4MPa;other conditions are the same,the strength of the composite made of rice straw fiber is lower than that made of corn straw fiber.When the straw fiber was treated with 6% Na OH for 6h,the flexural strength of the composite was higher,the highest was 11.2MPa;when the straw fiber was treated with pure silane coupling agent spray,the compressive strength of the composite was higher,the highest was 31.1MPa;when the straw fiber was treated with 7% Na OH for 18 h,the water absorption of the composite was lower,the lowest was 3 When the straw fiber was treated with 1% sodium silicate for 10 minutes,the water resistance coefficient of the composite was higher,the highest was 0.96.The overall properties of the composite were improved after 6% Na OH treatment for 6h and spraying with silane coupling agent. |
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