Effects of Combined Salt-Damage Resistant Agent on the Shrinkage, Chloride Penetration and Chemical Erosion of Mortar

Reinforced concrete structures located on coastal landfill frequently adjoin sea-water environment, and are exposed to sea water and humid environment during construction. Particularly, in the case of large-scale structures like dams, their drying shrinkage is accompanied by fatal cracking, and thus chlorine ion penetration becomes easier. The present study develops a salt damage-resistant agent (SRA) to which aluminum salts, oligomer condensate, and amino alcohol derivatives with the alkyl group are applied as binding inducers. SRA performs the roles of reducing the drying shrinkage of cement composites, binding chlorine ions, and preventing erosion by sulfate ions. This study tests and evaluates its resistance to degradation factors that may occur to structures constructed on coastal landfill and so on. As a result of evaluating shrinkage cracking properties by performing the restrained shrinkage cracking test, SRC showed the shrinkage reduction compared with BSC. As for the performance of resistance to chlorine ion and the chemical sulfate erosion rate, SRC showed the highest resistance performance, followed by BSC and OPC, regardless of the concentration of aqueous solutions for immersion. In addition, as for the rate of mortar weight change by sulfate erosion, the SRA-intermixed SRC mixture showed a weight reduction rate at the level of 1/3 of BSC and 1/6 of OPC, respectively

Restrained shrinkage cracking of self-consolidating concrete roads

The present study is dedicated to investigate the liability of continuously reinforced concrete pavement (CRCP) cast with self-consolidating concrete (SCC) to restrained shrinkage cracking and the values of restraint stresses in these pavements. SCC, which is becoming increasingly popular due to its several superiorities over conventionally vibrated concrete (CVC), has higher amounts and rates of shrinkage compared to CVC. The higher risk of restrained shrinkage cracking of SCC is a great cause of concern in pavement construction as the penetration of water, chemicals, and salts increases the risk of corrosion of reinforcement. In the present study, an analytical restraint stress expression was developed for typical CRC pavements by modifying the restraint stress equation developed previously for RC beams. Using this equation, the restraint stresses induced to the longitudinal reinforcement by the rigid pavement, cast with CVC or SCC, were calculated for eight different example sections. These restraint stress values were found to reach up to 50% of the limit stresses of bars, allowed by the design guidelines, when the pavement is cast with SCC. The amounts of longitudinal reinforcement used in typical CRCP roads were found to be more critical when the pavement is cast with SCC.