Research On The Mechanical Properties And Durability Of Organic Polymer Modified Coral Concrete

Coral concrete as a porous,non-homogeneous,loose inorganic brittle material,under the action of external loads and the surrounding environment,it is easy to develop micro-cracks,triggering local damage to the structure,which will reduce the strength and stiffness of the concrete structure,shortening the life of the concrete and affecting the overall safety of the concrete structure.The compounding of materials is an important means of improving the performance of concrete,so this thesis investigates the changes in the workability,basic mechanical properties,microscopic morphology of hydration products and resistance to sulphate after the existing design strength of C30 all-coral concrete is mixed with organic polymers alone or in combination with organic polymers,fly ash and silica fume.The main studies are as follows:(1)The PH value,solid content and viscosity of the four organic polymers were determined with reference to the instrumentation specifications for the physical properties of organic polymer emulsions.Slump tests were also carried out on organic polymer-modified coral concrete mixed with different types of organic polymers and with different mix ratios.The analysis of the test results showed that the slump of fresh concrete showed an increasing trend with the increase of the poly-ash ratio.(2)The basic mechanical properties of organic polymer modified coral concrete were tested to investigate the effects of different organic polymers,poly-ash ratios and ages on compressive strength,splitting tensile strength and flexural strength.The analysis of the test results shows that the incorporation of organic polymers will reduce the compressive strength of all coral concrete,but can improve the splitting tensile strength and flexural strength,and the four organic polymers at 5%-10% have the best effect on the mechanical properties of all coral concrete.Scanning electron microscopy(SEM)shows that the coral concrete becomes more rounded and smooth inside after the addition of organic polymers,resulting in a tighter connection between the coarse aggregates and the cement paste.(3)On the basis of the selection of poly-ash ratio of 5% butylbenzene latex modified coral concrete and benzene propylene emulsion modified coral concrete,continue to mix with different contents of fly ash and silica fume,and study its effect on the mechanical properties of organic polymer modified coral concrete and the microscopic morphology of hydration products.The analysis of the test results shows that: silica fume can improve the compactness of the organic polymer modified coral concrete;the use of fly ash to replace part of the cement can be used to reduce the amount of water and concrete water secretion rate,while maintaining the original concrete and ease;and the incorporation of silica fume and fly ash can strengthen the organic polymer film,to a certain extent to strengthen the internal structure of the organic polymer modified coral concrete.The incorporation of fly ash and silica fume can improve the compressive strength,splitting tensile strength and flexural strength of coral concrete.(4)The values and microstructures of compressive corrosion resistance coefficient,mass loss rate and relative dynamic elastic modulus were used as evaluation indexes for the performance of concrete under the dry and wet cycle erosion mechanism of sulphate solution.The results show that organic polymer-modified coral concrete can resist sulphate attack more effectively as the amount of silica fume and fly ash is increased,and that the incorporation of benzene propylene emulsion into coral concrete is more effective than styrene butadiene latex in resisting sulphate attack.