Many studies have demonstrated the fragility of calcareous sands even under small stresses. This bears an adverse influence on their engineering properties. A series of laboratory tests were carried out on poor-graded calcareous sands to investigate the crushability mechanism. Einav’s relative breakage and fractal dimension were used as the particle breakage indices. The results show that the particles broke into smaller fragments at the low-stress level by attrition which was caused by friction and slip between particles. In contrast, particles broke in the form of crushing at the relatively higher stresses. The evolution of the particle size was reflected by the variation in Einav’s relative breakage and fractal dimension. As testing commenced, the breakage index rapidly increased. When the stress was increased to 400 kPa, the rate of increase in the breakage index was retarded. As the stress was further increased beyond 800 kPa, the rate of increase in the fractal index became much smaller. This elucidated that the well-graded calcareous sands could resist crushing depending on the range of applied stresses. Based on the test findings, a new breakage law is proposed.
The tropical coastal region of Malaysia has a hot climate, high average annual temperature, and varying quality of local raw materials, making it challenging and difficult to carry out large volume concrete projects in this region. In this paper, we developed a special admixture for bulk concrete in subtropical coastal environment by modifying the basis of acrylic acid-based polycarboxylic acid admixture. The concrete prepared with this admixture has good ease, no water secretion, excellent mechanical properties and greatly improved exothermic characteristics. The C50 mass concrete prepared with this admixture has an initial slump/extension of 220/585mm, a 2h slump/extension of 210/570mm, and a crack resistance class I.
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