Experimental Research On Frost Resistance Behavior Of Basalt Fiber Reinforced Concrete

The statistics of domestic and international indicates that the economic losses caused by the durability of concrete structure are still increasing yearly,and one of the main causes of concrete structures' durability problems is freeze-thaw failure,so the researches on frost resistance of concrete are widely concerned.Basalt fiber reinforced concrete has good features in mechanical and durability properties.However,at present the researches focus on its static mechanics properties,while the researches on its frost resistance are lacking.The aims of this thesis are to study the frost resistance of basalt fiber reinforced concrete which under different curing conditions and freeze-thaw cycles,to discuss its mechanism of frost resistance,to provide references for the wider researches and applications in the future.In this thesis,a basalt fiber volume ratio of 0.15% as the gradient were mixed into C60 high strength concrete,and the range of basalt fiber was from 0% to 60%.Quick frost method to freeze-thaw cycle test was carried out,frost resistance of basalt fiber reinforced concrete from a macro perspective was researched according to the mass loss,relative dynamic modulus of elasticity change and cubic strength decreases after freeze-thaw cycles.Scanning electron microscopy and mercury intrusion porosimetry tests were operated to measure the microstructural features and pore structure characteristics of concrete,in oreder to futher research on the frost resistance mechanism of basalt fiber reinforced concrete.The results indicate that the frost resistance of basalt fiber reinforced concrete is better than that of concrete without basalt fiber.In normal curing and short term curing tests,the addition of basalt fiber can reduce the mass loss,relative dynamic modulus of elasticity and cubic strength decreases of concrete effectively.In sea water curing test,the addition of basalt fiber has no obviously effect on reducing the mass loss,but can reduce decreases of the relative dynamic modulus of elasticity and cubic strength.Some conclusions were given by the comprehensive analysis of frost resistance indexes: concrete with 0.15% volume ratio of basalt fiber had the best frost resistance.Brittle failure tendency were appeared in concrete without basalt fiber no matter normal curing,short term curing or sea water curing freeze-thaw cycle tests,while basalt fiber reinforced concrete showed a reduction in the development trend of brittle failure in different degrees.Among the factors of osmotic pressure,hydrostatic pressure,icing expansion stress and temperature fatigue stress which canlead to concrete's freeze-thaw failure,the accumulation of internal damage caused by temperature fatigue stress,and the rapid expansion of micro-cracks are the primary reasons for the concrete's freeze-thaw failure in our tests.The addition of basalt fiber can delay the development of micro-cracks,reduce the internal damage generated during the freeze-thaw cycle tests and improve the frost resistance of the concrete effectively.