Experimental Research On Mechanical Properties Of Modified Rice-rusk-ash And Rubber Fiber Concrete

In this paper,in view of the current environmental degradation and energy conservation problems,a new green concrete was developed by processing agricultural waste rice husk and industrial waste tyres into rice husk ash and rubber particles,which were modified and used as part of the cementing materials and aggregates of concrete respectively,and mixed with appropriate amount of fly ash.Based on the orthogonal test method,the effect of the four factors on the mechanical properties of the concrete was investigated by taking different combinations of rubber,polypropylene fibre admixture,rice husk ash admixture and water-cement ratio as factors,with four levels of each factor,and the static mechanical properties test was used as the starting point to select four groups of optimal factor level combinations.The main results are as follows The main results of the study are as follows:(1)Static mechanical properties tests show that:the amount of rice husk ash has the greatest effect on the strength of MRRFC,and the amount of 15%-20%can effectively improve the compressive strength,splitting tensile strength and flexural strength of MRRFC;followed by the rubber combination and water-cement ratio,the overall strength of MRRFC increases and then decreases with the change of rubber combination and water-cement ratio;the amount of polypropylene fibre has the least effect on the strength of MRRFC.The influence of the amount of polypropylene fibres on the strength of MRRFC was the least.(2)The best combination of factor levels for MRRFC was group 9(A2B4C3D2)and the next best combination of factor levels was group 10(A3B1C3D4),group 4(A1B3C3D3)and group 15(A4B2C3D1).(3)The graded cyclic loading and unloading tests show that the axial peak strain increases with the number of cycles,the axial residual strain increases with the number of cycles,the modulus of elasticity shows an overall upward trend,and the smaller the polypropylene fibre doping,the better the deformation resistance.(4)The Hopkinson compression bar dynamic compression test showed that the degree of damage increased with the increase in impact air pressure.When the impact air pressure was 0.45MPa,only one corner began to be damaged,the spalling in group 9 was the smallest and the spalling in group 15 was the largest;when the impact air pressure was 0.50MPa,a large area of damage occurred in group 15;when the impact air pressure was 0.55MPa,a large area of damage occurred in MRRFC and the specimens in group 15 were completely damaged.(5)The Hopkinson compression bar dynamic compression test shows that the stress-strain curve under dynamic compression at different air pressures consists of two stages:rising and falling;the dynamic compression stress-strain curve under the same impact air pressure consists of three stages:the elastic stage,the plastic stage and the damage stage;the degree of damage increases with the increase of impact air pressure.(6)XRD diffraction tests and analysis of the hydration mechanism show that the modified rice husk ash has a high volcanic ash activity and specific surface area,and the fine particles continuously fill the voids in the material,and under the dual action of volcanic ash activity and filling effect,continuously react with the Ca(OH)2 generated by the hydration of the cement clinker,which reduces the concentration of Ca2+ and increases the concentration of Si4+,generating additional C-S-H and filling of early voids,which in turn accelerates the hydration of the cement clinker,and this cycle of "reaction-filling-reaction" results in a high density and strength of the final MRRFC..