Effect of Carbonation and Drying-Wetting Cycles on Chloride Diffusion Behavior of Coral Aggregate Seawater Concrete

Based on seawater immersion,drying-wetting cycles,carbonation and drying-wetting cycles for coral aggregate sea-water concrete(CASC)with different strength grades,the effect of carbonation and drying-wetting cycles on chloride diffusion be-havior of CASC is studied.The results show that the free surface chloride concentration(Cs),free chloride diffusion coefficient(Df)and time-dependent index(m)of CASC in the drying-wetting cycles is obviously higher than that in seawater immersion.The Df and m of CASC of carbonation and drying-wetting cycles is higher than that in the drying-wetting cycles.Carbonation increases the Df and m of CASC,which is against CASC to resist chloride corrosion.The corrosion possibility of CASC structures in different ex-posed areas is as follows:splash zone(carbonation and drying-wetting cycles)>tidal zone(drying-wetting cycles)>underwater zone(seawater immersion).Besides,the chloride diffusion rate of C65-CASC is 17.8%-63.4%higher than that of C65-ordinary aggre-gate concrete(OAC)in seawater immersion(underwater zone).Therefore,anti-corrosion measures should be adopted to improve the service life of CASC structure in the oceanic environment.

A review on adhesion behavior of chip seal pavement and aggregate

Chip seal is widely used for preventive maintenance to mitigate pavement deterioration,but it is prone to aggregate loss during pavement service.To further promote the development and application of chip seals in road engineering in China,the research progress of the adhesion behavior of aggregate and binder in chip seals was reviewed in this paper,focusing on the adhesion mechanism of emulsified asphalt and alkaline aggregate.The Influencing factors and evaluation methodology of chip seals'aggregate adhesion behavior were also discussed.The results demonstrate that the adhesion process between emulsified asphalt and alkaline aggregate is divided into three processes including infiltration,demulsification,and cluster,which is more complicated when compared to hot asphalt.When designing a chip seal,not only the characteristics of single material should be paid attention to,but also the combination of binder and aggregate matters a lot.To form good adhesion between aggregate and asphalt binder,various influencing factors such as material selection,design method,and construction technical index should be considered comprehensively in the whole design,construction,and operation process.Three methods for evaluating adhesion behavior are summarized,including macroscopic adhesion performance tests,image analysis technology,and model prediction.It is not objective to evaluate the aggregate adhesion behavior of chip seal only by a single evaluation method.A comprehensive evaluation based on the micro-macro multi-scale method should be considered in the future.