Research On Damage Effect And Control Measures Of Fiber Reinforced Concrete Under Synergy Of ASR And Freeze-Thaw Cycle

The influence factors of concrete durability are complex. The interaction of many factors often promote each other, which leds to the rapidly decline of concrete durability. The two important factors of affect concrete durability are AAR(Alkali aggregate reaction) and freeze-thaw cycles. At present, single factor on the destruction of concrete durability research has been relatively mature and perfect. However, ASR (Alkali-silica reaction)and freeze-thaw cycle on the mechanism of synergy have not a precise and reasonable statement. With expansion rate and relative dynamic modulus as damage variable,investigated the composite damage effect of fiber reinforced concrete under the synergistic effect of Alkali - silica reaction and freeze-thaw cycle,based on the research concrete durability under the effect of single role of Alkali-silica reaction and freeze-thaw cycle. And found the best combination of measures of inhibit the damage, contrary to this complex injury. Considering the ASR and freeze-thaw cycle is difficult to conduct simultaneously, the experimental arrangements two combinations: one, first ASR occurs and then to freeze-thaw cycle; two, first freeze-thaw cycle occurs and then to ASR. And then compared the situation of combined effects with single function. This study conclusions are as follows:(1) For the situation of first ASR occurs and then to freeze-thaw cycle: Specimens occurred pre-ASR will also speed up the later freeze-thaw damage. The greater of the pre-ASR(The higher of the alkali content), the more seriously crack of specimens and the worse of frost resistance. The expansion ratio and relative dynamic modulus were 1.265% and 62% at the end of experiment, when Alkali content is 1.5% .(2) For the situation of first freeze-thaw cycle occurs and then to ASR: Specimen roled by the freeze-thaw cycle at early stage, which would promote the latter part of ASR damage and accelerate injury process; The more serious the injury at early stage of the freeze-thaw cycle, the more serious post-secondary damage caused by ASR; Specimens role by freeze-thaw cycle, which injury laws are similar to ASR injury when roled by the furthe ASR, and is similar to the more serious ASR role. Early freeze-thaw cycles did not change the role of regular secondary ASR; Freezing and thawing make the concrete v generated micro-injury, changed the microstructure of concrete and the concentration of alkali of this process,which is the reason for increasing ASR secondary injury.(3) Specimens effected by the composite of ASR and freeze-thaw cycles, having demonstrated a greater deterioration than the value of a single role, even surpassed the degradation indicators roled by single of them. That is to say fiber reinforced concrete expressed as a super stack effect under the synergistic effect of Alkali - silica reaction and freeze-thaw cycle.(4) By quadratic regression orthogonal design to study the fly ash, polypropylene fiber, air-entraining agents on the ASR-fiber reinforced concrete under freeze-thaw damage synergistic inhibition of damage. Obtained content in the test range through analysis, inhibitory effect is the best when the fly ash taking 33.53 percent, polypropylene fiber content obtained 1.25kg/m3, air-entraining agent mixed with 0.0335%. In addition, single factor effect analysis showed that polypropylene fiber has less effect on expansion ratio and relative dynamic modulus.