机制砂混凝土材料与构件性能试验及细观数值模拟研究

发布时间：2018-03-18 22:22

  本文选题：机制砂　切入点：骨料形状　出处：《浙江大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着我国城镇化进程的不断加深以及基础设施建设的日益发展,近年来不少地区天然砂资源逐渐匮乏。机制砂作为天然砂的良好替代物,正受到越来越高的重视。然而,机制砂在颗粒粒形、级配与石粉含量等方面与天然砂存在显著差异,机制砂一般级配较差、细度模数偏大,且表面粗糙、颗粒尖锐有棱角,这些都导致了其对混凝土力学性能的影响与天然砂相比存在巨大差异。本文选取了浙江省地区常用的三种机制砂和一种天然砂,从各自特性入手,根据现行规范评定了其质量等级。同时,定义了三种形状参数并利用数字图象处理技术比较了不同种类砂之间的形状差异,并由此建立了特定形状参数骨料组成的混凝土模型,利用有限元数值模拟方法研究了骨料形状差异对混凝土力学性能的影响。本文还针对每一种砂制作了混凝土试块和钢筋混凝土试验梁,通过试验研究了机制砂对混凝土工作性能、力学性能、干缩性能、梁受弯性能、梁受剪性能等的影响,得到如下主要结论:(1)本文采用的细骨料样品中,工程用台州精品机制砂(机制砂C)为Ⅰ类中砂,台州普通机制砂(机制砂B)为Ⅲ类中砂,富阳产卵石机制砂(机制砂A)不符合现行规范的规定,但由于目前有工程尚在应用,仍列为研究目标,杭州地区普通河砂(天然砂)为Ⅱ类中砂;(2)本文利用数字图像技术获取了细骨料图像并分析了其形状参数,结果表明天然砂总体上形状较机制砂更平整圆润。不同机制砂中,机制砂A的各项形状参数略好于另外两种机制砂,说明卵石母岩的机制砂其形状相对碎石母岩的机制砂略光滑圆润;(3)本文提出了一种随机骨料单元生成方式,其特征是能够生成特定形状参数的骨料单元。本文参照了骨料形状参数的实测结果,建立了混凝土细观模型,然后结合有限元数值模拟方法分析了不同种类细骨料混凝土的抗压强度;(4)本文制作了混凝土试块并进行了工作性试验、力学性能试和体积稳定性试验,结果表明良好的细骨料颗粒形状是保证其混凝土工作性的重要因素,且由合格的机制砂制作的混凝土其强度和长期干缩性能能够达到甚至超过天然砂混凝土;(5)本文通过钢筋混凝土梁试验研究发现,机制砂及天然砂梁的受弯、受剪性能总体上非常相似,由天然砂梁的设计方法计算得到的机制砂梁受弯、受剪极限承载力也均满足工程要求。但是,从试验结果中发现,天然砂钢筋混凝土梁抗裂能力略优于机制砂钢筋混凝土梁,特别是由现行方法计算得出的机制砂钢筋混凝土梁开裂荷载偏于不安全,建议对机制砂钢筋混凝土梁的开裂荷载设计进行适度调整。
[Abstract]:With the deepening of China's urbanization and the development of infrastructure construction, natural sand resources in many areas have been gradually scarce in recent years. As a good substitute for natural sand, machine-made sand is receiving more and more attention. There are significant differences in grain shape, gradation and stone powder content between machine-made sand and natural sand. The general gradation of machine-made sand is poor, the fineness modulus is large, the surface is rough, and the grain is sharp and angular. All of these results in a great difference between the mechanical properties of concrete and the natural sand. In this paper, three kinds of machined sand and one kind of natural sand which are commonly used in Zhejiang Province are selected, starting with their respective characteristics. The quality grade is evaluated according to the current specifications. At the same time, three shape parameters are defined, and the shape differences among different kinds of sand are compared by digital image processing technology, and a concrete model composed of aggregates with specific shape parameters is established. The influence of the shape difference of aggregate on the mechanical properties of concrete is studied by using finite element numerical simulation method. In this paper, concrete test blocks and reinforced concrete test beams are made for each kind of sand. The effects of machine-made sand on the working properties, mechanical properties, dry shrinkage properties, flexural properties of beams and shear properties of beams are studied. The main conclusions are as follows: 1) in the sample of fine aggregate used in this paper, The fine machined sand of Taizhou (machine-made sand C) is class 鈪，

本文编号：1631558