Experimental Investigation Of The Chloride Threshold Of Coral Aggregate Concrete In Extreme Environment

With the ongoing construction of islands and reefs in the South China Sea,it is extremely urgent to explore new locally sourced materials,such as coral aggregate concrete.The coral aggregate concrete contains considerable internal chloride ions and a large number of internal pores,which lead to a high level of diffusivity.Therefore,it is meaningful to study the chloride threshold content of the reinforcing steel embedded in coral aggregate concrete,especially for predicting the service life of concrete structure.This paper is based on the extreme hot-humid climate in South China Sea.Experimental studies are conducted to attain the chloride threshold contents of coral aggregate concrete by using the dry-wet circulation method and electro-migration method.The main content in present work are as follows:In consideration of the fact that coral aggregate is porous,lightweight and contaminated by chloride ions,an integrated experimental protocol is proposed in view of the extreme hot-humid situation,including the accelerated deterioration test methods,the determination methods of the depassivation of reinforcing steel and the test methods of chloride contents.This experimental protocol would provide a strong support to future relevant research.Taking the coral aggregate with strength grades of C30 as the subject of research,the present work analyses the electrochemical parameters'time-varying law of reinforcing steel,discusses the apparent/micro morphology characteristics and phases of corrosion products,compares the chloride threshold values of both methods(the dry-wet circulation method and electro-migration method,respectively)and establishes a correlation between these two methods.The chloride threshold values of coral aggregate concrete under high temperature and high humidity,including the total,free Cl~-and[Cl~-]/[OH~-]ratio,are investigated by applying the experimental protocol.The impact of water-binder ratio,admixture type and dosage(fly ash,silica fume and blast slag,respectively)on the chloride threshold values are also investigated.The correlation between these factors and the threshold value are established.