不同岩性的机制砂混凝土本构关系及力学性能

为研究机制砂混凝土在单轴应力状态下的力学性能,分别以广西地区石灰岩、卵石、玄武岩3种岩性机制砂为细骨料,以混凝土强度等级为变化参数,设计并制作了24个150 mm×150 mm×300 mm标准棱柱体混凝土试件和24个150 mm×150 mm×150 mm标准立方体混凝土试件,以河砂混凝土为对比试件,进行了单轴抗压试验,获得了试件在单轴受压下的抗压强度和应力-应变全过程曲线,通过拟合得到了适用于机制砂混凝土的单轴受压本构方程。基于试验数据,提出了机制砂混凝土的弹性模量计算公式。结果表明:不同岩性的机制砂混凝土破坏形态大致相同; 机制砂混凝土应力-应变曲线变化趋势与河砂混凝土相似,在曲线的上升段,机制砂混凝土与河砂混凝土基本重合,但在下降段,机制砂混凝土脆性较大,曲线比较陡峭; 基于Sargin模型拟合得到的机制砂混凝土应力-应变全曲线与试验全曲线吻合较好; 机制砂混凝土的力学性能与不同岩性细骨料的物理特性有关,随着细度模数的增大或石粉含量的增多,机制砂混凝土试件峰值应力与峰值应变呈现出先增大后减小的趋势; 当水灰比在0.3～0.4之间时,建议机制砂混凝土换算系数取为0.77; 卵石机制砂混凝土弹性模量均高于石灰岩和玄武岩机制砂混凝土。

Constitutive Relationship and Mechanical Properties of Manufactured Sand Concrete with Different Rocks

In order to study the mechanical properties of manufactured sand concrete(MSC)under uniaxial stress, taking three kinds of manufactured sand including limestone sand, pebble sand, basalt sand in Guangxi as fine aggregates, taking the concrete design strength grade as variable parameter, 24 standard prism concrete specimens(150 mm×150 mm×300mm)and 24 cube concrete specimens(150 mm×150 mm× 150 mm)were cast. Comparing with the river sand concrete(RSC), the uniaxial compression tests were carried. The compressive strength and stress-strain relation curves were obtained, and the uniaxial compression constitutive equations suitable for MSC were obtained. The formula of elastic modulus of MSC was presented by the test data. The results show that the failure modes of MSC with different lithologies are almost the same. The stress-strain curve of MSC is similar with that of RSC, in the rising stage of the curve, MSC and RSC have basically coincident curve, however, in descending stage, the curve of MSC is much steeper than that of RSC. The stress-strain curve of manufactured sand concrete fitted by Sargin model is in good agreement with the experimental curve. The mechanical properties of manufactured sand concrete are related to the physical properties of fine aggregate with different lithologies. With the increase of fineness modulus or stone powder content, the peak stress and peak strain of manufactured sand concrete show a trend of first increasing and then decreasing. The peak stress and peak strain of manufactured sand concrete show a trend of first increasing and then decreasing. The conversion coefficient of MSC is proposed to be 0.77 when the water cement ratio is 0.3-0.4. The elastic modulus of pebble sand concrete is higher than that of basalt sand concrete and limestone sand concrete.