Experimental Study On Mixing Coral Reef Sand Concrete With Sea Water

Concrete is the most widely used building materials in construction projects.However,there are many difficulties and high costs in the transportation of concrete materials in offshore projects.China has a long coastline,many offshore coral islands and rich coral reef resources.Mixing Coral Reef Sand Concrete with sea water can achieve local materials such as fine aggregate and standby water,reduce the cost of material transportation,provide an effective way to solve the problem of building materials for offshore projects,and have important economic and social benefits for China's marine construction.Based on the principle of concrete preparation and the existing research results of coral aggregate concrete,the preparation process and proportion range of coral reef sand concrete are determined through a large number of trial mix research.On this basis,the orthogonal optimum mix proportion experiment is carried out,and the optimum mix proportion of coral sand concrete strength is obtained.According to the determined optimum mix proportion,the tests of cube compression,splitting tension,bending resistance,axial compression,modulus of elasticity and bond of material and soil are carried out,the basic mechanical performance indexes of coral reef sand concrete are determined,the law of strength growth of material and the influence of relevant factors are analyzed,and the feasibility of application of sea water mixing Coral Reef Sand Concrete in marine engineering is discussed ? In order to simulate the high temperature,high humidity and high radiation environment of the sea water and the sea water heavy corrosion sea water environment,the chloride ion penetration resistance,sodium sulphate corrosion resistance,magnesium sulphate corrosion resistance and low latitude strong ultraviolet aging test of the sea water mixed coral reef sand concrete were carried out,and the corresponding corrosion resistance and aging resistance indexes and performances were obtained.Through the comparative analysis of the durability experiment of the ordinary concrete,the corrosion resistance and aging resistance indexes and performances were discussed The feasibility of the coral reef sand concrete used in the sea or the corresponding heavy corrosion environment is discussed.The main research contents and conclusions are as follows:1.Optimization of preparation process and strength ratio.The strength of coral reef sandconcrete is affected by the amount of cementitious material,water cement ratio,sand ratio and other proportioning parameters.When the amount of cementitious material is limited within a certain range,the order of the influence of proportioning factors on the cube strength of coral reef sand concrete is: water cement ratio > sand ratio > cementitious material amount.When the dosage of cementitious material is 420 kg,the water binder ratio is 0.52,and the sand ratio is 40%,the cube strength of the material is the best.On the basis of optimized mix proportion,the coral reef sand concrete prepared by sea water has moderate slump and fluidity,its working performance meets the general engineering requirements,and its volume stability is not different from that of ordinary concrete.2.Basic mechanical properties.Coral reef sand concrete has the characteristics of early strength,the compressive strength of 7-day-old reached more than 85% of 28 day compressive strength,but after that,the strength growth trend gradually slowed down.Compared with the ordinary concrete with the same strength,the cube compressive strength,axial compressive strength,splitting tensile strength and flexural strength are not weak,the flexural compression ratio is 12% higher,and the axial compression ratio fluctuates at 0.9,which has relatively good ductility.The bond performance of reinforcement and Coral Reef Sand Concrete meets the expectation.3.Durability test in simulated environment of high corrosive seawater,high temperature,high humidity and high radiation.The anti-corrosion coefficient of Coral Reef Sand Concrete soaked in different concentrations of sodium sulfate and magnesium sulfate solution for six months is greater than 0.9,the anti chloride ion erosion ability is not lower than that of ordinary concrete,and the four-year aging strength loss of offshore environment is not greater than 4%,which is better than that of ordinary concrete of the same strength level.4.The preparation technology and mix proportion proposed meet the requirements of the preparation of coral reef sand concrete mixed with sea water.Its basic mechanical properties and durability such as corrosion resistance and aging resistance are not lower than that of ordinary concrete of the same strength level,which provides an effective way to replace ordinary concrete for Offshore Engineering.