An Experimental Study On The Basic Properties And Chloride Diffusion Characteristics Of Concrete Made With Cement For Marine Projects

Based on a coastal reclamation project of Zhejiang Province, the optimal contents of water-reducing agent and fibers were studied. The effects of various factors on the slump, strength and chloride diffusion coefficient of concrete, the time to surface cracking of reinforced concrete beams, the reinforcement corrosion rate, and the crack width were analyzed. The mechanisms of diffusion of chloride ions in concrete and of cover cracking were revealed.The experimental results showed that the compressive strength of concrete increases with the curing age but decreases with an increase in water/cement ratio. Fibers have little effect on the compressive strength of concrete. The chloride diffusion coefficient decreases with the increase of the curing age but increasing with increasing the water/cement ratio and the fiber content. Concrete with fly ash or ground slag has a low early-age compressive strength. For a given content, the early-age strength of concrete with ground slag is higher than that with fly ash. However, the strength of concrete with fly ash or ground slag develops significantly at the later age. At the prescribed curing age, the chloride diffusion coefficient is smaller than that of concrete. Ground slag exhibits better improvement to the performance of resistance to chloride ion penetration of concrete than fly ash. The mixture of fly ash and ground slag can significantly improve the early-age strength of concrete and has a better effect on the performance of resistance to chloride ion penetration than fly ash or ground slag only. Coating on the concrete surface can reduce the chloride diffusion coefficient in varying degrees. Epoxy resin has the best effect, while organosilicone has the highest quality-price ratio. The combination of mineral admixture and surface coating has a better effect on the performance of resistance to chloride ion penetration than minimal admixture or surface coating only. The time to cover cracking decreases with the increase of current density, but increases slightly with the water/cement ratio and significantly with the cover depth. The water/cement ratio only influences early-age cracking and the slow development of cracks, while the cover depth has a larger effect on the whole process of cracking.