Study On Mechanical Properties Of Reactive Powder Concrete Mixed With Tuff Powder And Tuff Manufactured Sand

Nowadays,manufactured sand is the main sand source to replace natural sand and has been widely used.In the process of producing tuff manufactured sand,it is inevitable to produce industrial by-product tuff powder,which has huge output and low resource utilization rate.Stacking leads to a large amount of land resources occupation and potential pollution to the environment.Reactive powder concrete(RPC)is a kind of cement based materials with excellent performance,but its material cost is high.If the tuff powder and tuff manufactured sand can be used to prepare RPC,it will not only reduce the cost of RPC,but also have considerable environmental benefits.In view of this,this thesis studies the mechanical properties of RPC mixed with tuff powder(TP-RPC)and TP-RPC mixed with tuff manufactured sand(TMSTP18-RPC)through experiments,and analyzes its microstructure by means of microscopic test to study the change mechanism of its mechanical properties.Based on the consideration of engineering application,the optimum content of tuff powder was determined through tests,and the mix proportion and curing process of RPC with 18% tuff powder(TP18-RPC)were optimized through orthogonal tests.The main conclusions are as follows:(1)The mechanical properties of RPC are adversely affected by the addition of tuff powder.With the increase of the amount of tuff powder,the compressive strength and flexural strength of TP-RPC are gradually reduced.The compressive strength and flexural strength of TP-RPC prepared with the content of tuff powder less than 18% can meet the index requirements of mechanical property grade RPC100.(2)The addition of tuff powder has a great influence on the micro morphology of RPC,and new forms of hydration products are generated.When the content of tuff powder is less than 12%,the interface transition zone of TP-RPC microstructure will be dense.When the content of tuff powder is more than 12%,the compactness and hydration reaction degree of TP-RPC interface zone will be continuously reduced.When the content of tuff powder is more than 18%,the interface transition zone will be very loose,showing a serious agglomeration effect,and the homogeneity will be significantly reduced.(3)The pore structure of RPC can be improved by adding tuff powder.With the increase of tuff powder content,the pore volume and porosity of TP-RPC show a trend of first decreasing and then increasing.Among them,the replacement rate of 12% will be the peak of tuff powder content.The porosity of RPC is the lowest,and the proportion of multi hazard holes is significantly reduced.(4)When TP18-RPC is prepared by mixing tuff manufactured sand instead of quartz sand,the compressive strength and flexural strength of TMSTP18-RPC have no obvious upward or downward trend,and only fluctuate up and down within a range.The microscopic morphology of the interface transition zone of the microstructure of TMSTP18-RPC has no obvious difference,and the influence on the total porosity,pore volume and pore size distribution of TMSTP18-RPC is not obvious.