| In this paper,the concrete which enables transport service within 24 hours,is produced by applying appropriate mixture proportion of polycarboxylate Superplasticizer.On this basis,different fibers(ordinary steel fiber,ultra-fine steel fiber and PVA fiber)are blended in the concrete to increase the toughness.We investigate the pavement performance of hybrid fiber concrete,cement concrete and single fiber concrete respectively on the condition that the amount of steel fiber is under 1.5%;In the case of incapable pavement repairing in winter with very low temperature,different curing temperatures are studied to obtain a scientific and feasible method of repairing.Following conclusions are drawn from a large number of experiments.(1)The workable performance of concrete mixed with fiber decreases significantly.Specifically,ordinary steel fiber and multi-hybrid fiber pose greater degradation than PVA fiber on workable performance.(2)The flexural and compressive strength can be significantly enhanced by mixing with fiber.Thereinto,the steel fiber and multi-hybrid fiber can be used to achieve more flexural strength than single PVA.The flexural and compressive strength increase along with the mixture amount.When the amount of steel fiber is fixed,the flexural and compressive strength improvement along with additional fiber is presented as follows: multi-hybrid fiber> ultra-fine steel fiber> ordinary steel fiber.In the 28 d age,the flexural strength and compressive strength of concrete containing PVA fiber increase by 8.9% and 4.7% respectively;when the concrete is mixed with steel fiber with an amount of 1% and 1.5%,the flexural strength increase by 14.2% and 21.2%respectively,and meanwhile,the compressive strength increase by 4.9% and 11%;when the concrete is mixed with ultra-fine steel fiber with an amount of 1% and 1.5%,the flexural strength increase by 30.9% and 40.7% respectively,and meanwhile,the compressive strength increase by 16.9% and 23.4%;in regard to the multi-hybrid fiber,the concrete with 1% steel fiber have about 32.1% and 19.3% more flexural and compressive strength.When the proportion of steel fiber is 1.5%,the flexural and compressive strength increase by 50.8% and 26.6%.(3)In regard to the toughness,PVA fiber can provide more toughness at early stage but similar toughness in the long run.The flexural toughness of concrete can also beimproved significantly by blending with steel fiber and multi-hybrid fiber.The improvement can be sorted as follows: ultra-fine steel fiber > hybrid fiber> ordinary steel fiber.The long-term toughness improvements derived from various fibers are presented as follows: multi-hybrid fiber> ultra-fine steel fiber> ordinary steel fiber.(4)The elastic modulus remains unchanged after blending with PVA fiber;The elastic modulus of concrete can be increased by 5.5%~11.5% through blending with steel fiber and multi-hybrid fiber.In addition,the elastic modulus increase along with the amount of fiber.(5)According to a lot of durability tests,the impermeability can be improved by blending with PVA fiber.Correspondingly,steel fiber and multi-hybrid fiber pose little influence on the impermeability.Significant improvement on frost resistance,dry-shrinkage performance,wear resistance and impact resistance can be achieved by blending fiber in concrete.(6)Concerning to the earlier flexural strength,the concrete with high curing temperature is inferior to that with 20℃~30℃ curing temperature.In this case,the long-term strength increases at a lower speed relatively.On the contrary,the concrete with high curing temperature achieve more earlier compressive strength than that with20~30C curing temperature.However,the long-term strength is inferior to that with20~30C curing temperature.According to the SEM test results,the hydration rate of concrete goes up with the increasing of curing temperature at earlier stage.In addition,more hydration product are produced in the case of higher curing temperature. |
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