Evaluation of Corrosion Degradation Law of Recycled Reinforced Concrete in Saline Soil Under Electrified Environment

In order to investigate the corrosion mechanism of recycled reinforced concrete (RRC) under harsh environments,four recycled coarse aggregate (RCA) contents were selected,and saline soil was used as an electrolyte to perform electrified accelerated corrosion experiments.The relative dynamic elastic modulus and relative corrosion current density were considered to describe the deterioration law of the RRC in saline soil.The results indicated that as the energization time increased,the corrosion current density,corrosion potential,and polarization resistance of the steel bar decreased gradually.Compared with ordinary reinforced concrete,when the RCA content was 30%,the ability of the RRC to resist corrosion was improved slightly;however,when the RCA content exceeded 30%,the corrosion resistance of the RRC deteriorated rapidly.Scanning electron microscopy revealed that for a dense RRC,less corrosion products were generated in the pores inside the concrete and on the surface of the steel bar.X-ray diffraction results indicated that SO_(4)^(2-) can generate ettringite and other corrosion products,along with volume expansion.The main corrosion products generated on the surface of the steel bars included Fe_(2)O_(3),Fe_(3)O_(4) and FeO(OH),which were the corrosion products generated by steel bars under natural environments.Therefore,using saline soil as an electrolyte is more consistent with the actual service environments of RRC.Both the relative dynamic mode and relative corrosion current density of the degradation parameters conform to the Weibull distribution;furthermore,the relative dynamic mode is more sensitive and the corresponding reliability curve can better describe the degradation law of RRC under saline soil environments.

Prediction of the Residual Strength for Durability Failure of Concrete Structure in Acidic Environments

According to the results of accelerated tests of acidification corrosion depth and compressive strength of concretes subjected to sulfuric acid environments,the acidification depth laws of concretes were predicted based on the grey system theory.Thus,the remaining compressive strength was calculated when the acidification depth reached the protection layer thickness of concrete structures,which indicates that the limit state of durability failure can be defined based on strength degradation,and the calculation process was illustrated by an example.The calculated results show that the remaining compressive strength values in the durability failure limit state for the concrete structures exposed to p H=2 and 3 sulfuric acid water environments and wet-dry cyclic sulfuric acid environment with p H=2 are 74%,72%,and 80% of initialstrength,respectively.The method provides references for the durability evaluation of concrete structure design under the acidic environments.