Study On Microscopic Characteristics And Compressive Properties Of Rubber Concrete With Nano-SiO₂ Endogenous Solution

With the rapid development of the domestic automobile industry,the number of waste tires continues to grow,which not only pollutes water sources and soil,but also endangers human health.At present,the incorporation of rubber particles into concrete can improve the performance of concrete in many aspects such as impermeability and carbonization resistance,and also provides an effective way to solve rubber pollution,which is of great significance to the national sustainable development policy.In this thesis,the compressive strength,microstructure characteristics,element distribution,phase composition,pore structure and pore size distribution of rubber with nano-Si O₂endogenous solution were mainly studied.The main results are:（1）Through the cube compressive test,the effects of rubber content,rubber particle size,internal solution content and p H value on the compressive strength of rubber concrete were studied.The results showed that the rubber particles reduced the compressive strength of concrete.The larger the rubber content,the smaller the rubber particle size and the lower the compressive strength of the rubber concrete.The nano-Si O₂endogenous solution improves the compressive strength of rubber concrete to a certain extent.The higher the content of nano-Si O₂endogenous solution,the higher the compressive strength;when the content of nano-Si O₂endogenous solution is too low,the effect of improving the strength is not obvious;When the rubber particle size is 3-6mm,the rubber content is 4%,and the nano-Si O₂endogenous solution content is 15%,the compressive strength of rubber concrete increases the most,increasing by 25.73%.The compressive properties of the rubber concrete were significantly improved when the internal solution was p H=6,the compressive strength of the rubber concrete decreased obviously when p H=4 and p H=8,and the strength decreased the most at p H=4.（2）Through scanning electron microscopy（SEM）and energy dispersive analysis（EDS）experiments,the effects of rubber content,rubber particle size,and endogenous solution content on the microscopic morphology,element distribution,hydration products and the width of the interface transition zone of rubber concrete were studied.The results show that:（1）The rubber particles are poorly combined with the cement matrix,there are obvious holes and cracks,and a large amount of calcium hydroxide and ettringite are accumulated in the microscopic area;when the rubber particle size is 3-6mm and the rubber content is 8%,in the microscopic area the content of ettringite is the highest;when the rubber content is 12%,the microstructure stability is the worst.（2）The rubber changed the change rule of Ca element in the concrete microscopic area of 0-60μm.At 0μm,a large number of CH crystals aggregated to form a weak area;The larger the rubber content,the higher the Ca element content,the lower the Si element content and the greater the decrease,but the rubber particle size has little effect on the Ca element and Si element content.Furthermore,the rubber particles increased the concrete microscopic ITZ width from35μm to 60μm.（3）The nano-Si O₂endogenous solution improves the microscopic morphology of the rubber concrete.With the increase of the endogenous solution content,the hydration products attached to the surface of the rubber particles increase,the rubber particles are better combined with the cement matrix,and the microscopic compactness is improved.CH,AFt content decreases,size decreases,C-S-H content increases,cement hydration products gradually became smaller and the hydration degree increased.The endogenous solution increased the content of Ca and Si elements in the micro-region of rubber concrete,changed the changing trend of Ca and Si elements,decreased the Ca/Si ratio in the interface region,and reduced the width of ITZ to 45μm.（3）Through the X-ray diffraction test,the effect of the endogenous solution on the phase composition and hydration rate of rubber concrete was studied.The results show that:（1）Neither the rubber particles nor the endogenous solution generated new phase structures in the concrete.（2）The rubber particles greatly reduced the diffraction peak of CH,hindered the hydration reaction of cement,and reduced the quantity of cement hydration products.The endogenous solution significantly increased the diffraction peak of C-S-H,increased the rate of cement hydration reaction,promoted the degree of hydration,and increased the number of hydration products.（4）Through mercury intrusion experiments,the effects of rubber content,rubber particle size,and endogenous solution content on the pore structure of rubber concrete were studied.The results show that:（1）The rubber particles and the internal solution have little effect on the critical pores and the most probable pores of the rubber concrete.The larger the rubber content,the smaller the rubber particle size,the larger the median pore size,specific pore volume and total porosity;the change in average pore size is 3-6mm>20 mesh>1-3mm.（2）The rubber particles reduce the proportion of harmless pores and less harmful pores in the concrete,and increase the proportion of harmful pores.The larger the rubber content,the smaller the rubber particle size,the smaller the proportion of harmless pores,and the more the proportion of harmful pores;in addition,it is the rubber particles that increase the proportion of harmful pores in the concrete,not the rubber particle size.（3）The endogenous solution significantly reduces the median pore size,average pore size,specific pore volume and total porosity of rubber concrete;the larger the content of the endogenous solution,the higher the proportion of less harmful pores,the lower the proportion of harmless pores,harmful pores and multi-harmful pores,and the more obvious the improvement effect on the pore structure of rubber concrete.This paper has 90 pictures,25 tables,and 101 references.