Mix Proportion Design And Durability Study Of High Performance Marine Concrete In Hong Kong-zhuhai-macao Bridge

The Hong Kong-Zhuhai-Macao Bridge was used in complex marine environment.In order to abtain high performance marine concrete?HPMC?with high durability and slowing chloride penetration rate,the rational raw materials was selected and optimum design of mix proportion were studied.Therefore,the mechanical properties and durability of the C35 pile,C45 cap and C50 pie were systematically studied.Based on the experiments above,the conclusions were outlined as follows:?1?The performance of concrete,the C35 HPMC of pile,was mainly affected by water binder in the three factors of water binder ratio,fly ash content and slag powder content.When water-binder ratio,fly ash content,slag powder content,sand ratio,superplasticizer content and unit water content were 0.36,25%,25%,43%,1.0% and 150 kg,the mechanical properties and durability of the concrete were the best among all the samples.The 28 day compressive strength of concrete,the chloride diffusion coefficient of concrete and electric charge of concrete could reach to 55.2 MPa,827 C,3.0×10^-12 m²·s^-1,respectively in the 56 day.?2?When the water-binder ratio,superplasticizer content and unit water content of the C45 HPMC of cap were 0.34,1.0% and 145 kg,the slump and the compressive strength of concrete increased fristly and then decrease along with the increase of the sand ratio gradually.However,the chloride diffusion coefficient and the passed electric charge showed an opposite tendency.When the water-binder ratio,sand ratio and unit water content were 0.34,42% and 145 kg,the slump and the compressive strength of concrete increased fristly and then decrease.Nevertheless,the chloride diffusion coefficient and the passed electric charge showed an opposite tendency.Considering the durability of concrete,the final composition of the mixture was 0.34 water-binder ratio,30% fly ash content,30% slag powder content,42% sand ratio,1.2% superplasticizer content and 145 kg unit water consumption.?3?The strength of concrete,the C50 HPMC of pier,was the mainly affected by water-binder ratio,in the four factors of fly ash content,slag powder content and silica fume in early time.However,the silica fume played a major role in influencing the strength and durability of concrete in the later period.Considering the economy and durability of concrete,the final composition of the mixture was 0.33 water-binder ratio,30% fly ash content,30% slag powder content,41% sand ratio,1.2% superplasticizer content and 145 kg unit water consumption.?4?The microstructure of concrete was further observed by XRD and SEM,and the theory of concrete durability was also analyzed.The rusults show that reaction of concrete mixed with mineral admixture was mainly the hydration reaction of cement clinker in early time.However,secondary hydration were occurred between the activity Al2O3 and SiO2 in mineral admixture and the hydration product Ca?OH?2 in late stage.What's more,it increaseed the content of C-S-H and C-A-H gel in cement paste and reduced the porosity of concrete.The later strength and durability of concrete were improved.