Study On Performance Of Whole Coral Concrete

The compressive strength,tensile strength and brittleness of whole Coral concrete are relatively low,and the composite material is an important means to improve the performance of concrete.Therefore,this paper studies the changes of the basic mechanical properties,the micro-morphology of hydration products and the impervious performance of whole Coral concrete after the addition of short-cut fiber,fly ash and silica ash.In the early stage of this paper,five groups of all coral concrete with strength of C30were designed,and their mechanical properties were tested to choose the best reference ratio.On this basis,the effects of different kinds of chopped fiber(modified polypropylene fiber?MPPF?,imitation steel fiber?ISF?,basalt fiber?BF?and different content?0kg/m³,1kg/m³,2kg/m³,3kg/m³?on the mechanical properties of total coral concrete were studied.The results show that the addition of chopped fiber has no obvious effect on the compressive strength of whole coral concrete,and the addition of BF even slightly reduces the compressive strength of whole coral concrete,but all the three kinds of chopped fiber can increase the ductility of its failure.The splitting tensile strength and bending strength of whole coral concrete can be improved by chopped fiber,among which MPPF is the best,ISF the second,BF the least.When 2kg/m³of MPPF was added,the compressive strength,splitting tensile strength and flexural strength of whole coral concrete increased the most,which increased by 9%,29%and 46%respectively compared with the blank group.It can be seen from scanning electron microscope?SEM?that MPPF,ISF and hardened cement slurry have a good degree of adhesion,and there is a large gap between BF and cement mortar.In best fiber and the optimal dosage?2 kg/m³of MPPF?premise,continue throughout the coral adding fly ash and silica fume concrete,the research on the coral concrete mechanical properties,hydration product of microscopic morphology and permeability of performance,the results showed that the incorporation of fly ash and silica fume can significantly improve the coral concrete compressive strength,splitting tensile strength and flexural strength.When 10%fly ash and 10%silica fume are added,the compressive strength,split tensile strength and flexural strength of whole coral concrete increase the most,with the values increasing by 43%,71%and 162%respectively compared with the blank group.SEM results show that the incorporation of fly ash and silica ash can effectively reduce Ca?OH?₂crystals,generate a large amount of calcium silicate hydrate?C-S-H?,and improve the morphology of the interfacial transition zone between coral aggregate and cement slurry.In the blank group,the water-resistant permeability grade of whole coral concrete was lower and the electric flux value of 6h was up to 5821C,while the incorporation of fly ash and silica fume could effectively reduce the electric flux of whole coral concrete for 6h and improve its water-resistant permeability grade.When 10%fly ash and 10%silica fume are added,the chloride ion permeability of all coral concrete is the best,with 6h electric flux value of 2352C and water permeability resistance grade of 18.