Experimental Study On Basic Properties Of Cement-stabilized Coral Materials

The South China Sea is a symbol of Chinese territorial sovereignty.In the process of road and airport construction in the South China Sea,the use of cement-stabilized coral base instead of traditional cement-stabilized gravel base will greatly reduce the project cost and construction time,which is of great significance for emergency construction in wartime,and the use of local coral aggregate instead of inland sand aggregate is beneficial to sustainable development strategy.Up to now,the research on cement-stabilized materials only stays at the basic level of meeting the requirements of compressive strength and limiting cement content to control shrinkage,and the related working mechanism of alkaline excitation of cement-stabilized materials system has not been revealed,let alone the research on cement-stabilized coral materials.Therefore,the results of this paper will not only fill the gap in the field of cementstabilized coral materials,but also have universal academic value.Based on the particularity of coral materials,the following research results were obtained by conducting relevant experimental studies on cement-stabilized coral materials:(1)Firstly,digital image recognition technology was used to evaluate the irregular morphology of coral materials.Then nitrogen adsorption test was carried out to reveal the characteristics of higher specific surface area and pore volume of the particles.Finally,the particle strength test revealed the low strength characteristics of coral granules and the hardening mechanism of cement cladding coral granules.(2)Based on the particularity of the above coral materials,the morphological characteristics of the cement hydration products on the surface of coral particles were analyzed by scanning electron microscopy,and the specific product composition of the cement hydration products on the surface of coral particles was analyzed by X diffraction analysis.Furthermore,the nano-indentation test showed that the surface of coral particles in cement-stabilized coral materials system had special activity.(3)Due to the irregular aggregate grain type and engineering compactness,the fine materials in the gradation are dominant(> 40%).The strength of cement-stabilized coral materials comes from the comprehensive effect of the relative reduction of the system’s accumulated particle surface area and the reduction of dense bulk void,so the cement content should be increased in coordination with the proportion of fine aggregate.When the general cement content exceeds 6%,the cement-stabilized coral materials can meet the strength requirement of base course.(4)Cement components in the water-stabilized coral system have a dual effect.On the one hand,the increase of cement components aggravates the degree of hydration reaction of the system,resulting in the increase of tensile stress and contraction strain in the system.On the other hand,when the cement component increases,the effect of system cementing compactness increases,which can also enhance the contraction restraint effect of cement-stabilized coral materials system and improve the tensile strength of it.The volume stability of the system is determined by the combined effect of two aspects.When the cement content is lower,shrinkage deterioration is more obvious.(5)Under the condition of no boundary constraints with a small pressure(0.3MPa),the scouring effect of cement-stabilized coral materials is not obvious,and the scouring damage of edge occurs at a high pressure(0.7MPa).With boundary constraints,the scouring resistance is better,and the scouring durability of cement-stabilized coral materials is significantly better than that of cement-stabilized soil.