Effect Of Rapid Water Intrusion On Fracture Properties Of Concrete

For the dam,the bridge pier across the river, structure seaport engineering and other that the concrete structure located in the water environment, because the concrete has the porosity and cracks which produced in the course of pouring and using, environmental water will immerse the crack, leading the structure to collapse, seriously to cause structure wreck even to destroy.If the environmental water immerse cracks,that will affect the mechanical properties and fracture properties of concrete.The current research are mainly paying attention to the mechanical properties and fracture properties of saturated concrete,but not involving the change of the fracture properties under the condition of water intrusion.In this paper, the object of study is dry and saturated concrete under the condition of rapid water intrusion.The following works have been carried in this paper:The first, by the compressive strength and splitting tensile strength test of dry and saturated concrete with different strength grade and different curing time , the impact of water on the concrete strength and the relation between the free water conctent and strength in concrete have been studied. The test results indicated that the compressive strength and splitting tensile strength of saturated concrete is higher than the compressive strength and splitting tensile strength of dry concrete.For the grade C20 and C30 concrete, the compressive strength and splitting tensile strength after 90 day's curing is higher than 28 day's curing while the free water content is decreased. The compressive strength and splitting tensile strength after 180 day's curing is also higher than 90 day's curing while the free water content somewhat increased.For the grade C40 concrete,the strength of saturated concrete increases as the free water content decreases.For the concrete of different grade,because of their different water cement ratio, the water cement ratio of low-strength concrete is higher than high-strength concrete,which make the free water conctent of low-strength concrete is higher than high-strength concrete.With the strength grade increases,the free water content of concrete decreases.The second,by the three-point bending beam test on concrete with the size of 100mmx100mmx515mm through the sample , pre-crack depth of 50mm, and width of 3mm,the fracture toughness ( K IC), fracture energy( G F) and crack mouth opening displacement(CMOD ) of the dry and water saturated concrete have been measured.The test results showed that: the water contained in concrete will change the concrete fracture toughness ( K IC), fracture energy( G F) and crack mouth opening displacement(CMOD ).The result of fracture toughness( K IC) and fracture energy ( G F) obtained the same conclusion, K ICand G F of saturated concrete is greater than K ICand G F of dry concrete, while for the crack mouth opening displacement(CMOD ), the value of dry concrete is greater than the value of saturated concrete.The third,by the three-point bending beam test on concrete with the size of 100mmx100mmx515mm through the sample , pre-crack depth of 50mm, and width of 3mm,the fracture toughness( K IC), fracture energy( G F) and crack mouth opening displacement(CMOD ) of the dry and water saturated concrete under the condition of rapid water intrusion have been measured.The test results showed that: the rapid intrusion of water will reduce the concrete fracture toughness( K IC), fracture energy( G F) and crack mouth opening displacement(CMOD ).Especially we can clearly see that the impact of rapid water intrusion on the fracture properties of concrete from thesaturated concrete with three different test condition.