【作者】 张杰；

【导师】 沙吾列提·拜开依；

【作者基本信息】 新疆大学 ， 工程硕士（专业学位）， 2022， 硕士

【摘要】 近年来,为响应国家绿色可持续发展政策的号召,砂作为一种不可再生资源被限令开采,导致砂子价格上涨,混凝土成本增加。而我国沙漠砂资源丰富,且易于开采,将沙漠砂应用于混凝土中不仅能够缓解用砂紧缺的问题,还能够缓解土地荒漠化。研究发现适量的沙漠砂加入混凝土后,能够提高混凝土的密度和强度。但由于沙漠砂颗粒粒径小、吸水率大的特性,导致掺沙漠砂混凝土抗收缩开裂的能力差,限制了掺沙漠砂混凝土在实际工程中的应用。因此,找到一种提高掺沙漠砂混凝土抗收缩开裂性能的方法具有一定的现实意义。纤维是建筑行业中常见阻裂材料。两种纤维或多种纤维同时掺入混凝土后,不同纤维的优势能够共同发挥作用,对混凝土的改善效果更好。本文利用玄武岩纤维和聚丙烯纤维配制混杂纤维,研究混杂纤维掺量和掺比对掺沙漠砂混凝土力学性能以及早期收缩开裂性能的影响,找到混杂纤维在掺沙漠砂混凝土中的最优掺量和掺配比例,并通过对比其力学性能的发展规律,分析混杂纤维掺沙漠砂混凝土的早期开裂趋势,得出以下结论:（1）混杂纤维掺量和掺比对掺沙漠砂混凝土的抗压强度和静压弹性模量的影响较小;但对其劈裂抗拉强度的增强显著;拉压比明显增大,说明掺沙漠砂混凝土的脆性有所改善;混杂纤维加入后,掺沙漠砂混凝土试件的破坏形态更加完整,其整体性提高。（2）随着混杂纤维掺量的增加,掺沙漠砂混凝土的水分蒸发量、收缩率以及抗裂等级均呈现先上升后下降的趋势;且试件表面裂缝宽度和总开裂面积变小,裂缝出现的时间变晚;相比混杂纤维掺量,纤维掺比对早期收缩抗裂性能影响较小;两种纤维混掺时,掺沙漠砂混凝土抗收缩开裂的效果更好。（3）混杂纤维加入掺沙漠砂混凝土后,其3d内的抗拉强度增长率f_ts/f_ts28和弹性模量增长率E/E₂₈增长较快;随着混杂纤维掺量和玄武岩纤维占有率的增加,两者之间的差值明显变小,但由于E/E₂₈仍大于f_ts/f_ts28,说明混杂纤维掺入后,掺沙漠砂混凝土的早期开裂趋势变小,但仍存在早期开裂的风险。更多还原

【Abstract】 In recent years,in response to the call of national green and sustainable development policy,sand as a non-renewable resource is limited to mining,resulting in sand prices rise,the cost of concrete increases.However,desert sand resources are abundant and easy to be mined in China.The application of desert sand in concrete can not only alleviate the problem of sand shortage,but also alleviate land desertification.It is found that adding proper amount of desert sand to concrete can improve the density and strength of concrete.However,due to the characteristics of small particle size and high water absorption of desert sand,the anti-shrinkage cracking ability of concrete mixed with desert sand is poor,which limits the application of concrete mixed with desert sand in practical engineering.Therefore,it is of practical significance to find a method to improve the anti-shrinkage cracking performance of concrete mixed with desert sand.Fiber is a common anti-crack material in construction industry.When two or more fibers are mixed into concrete at the same time,the advantages of different fibers can play a role at the same time,and the improvement effect of concrete is better.In this paper,basalt fiber and polypropylene fiber were used to prepare hybrid fiber,and the influence of the mixing amount and ratio of hybrid fiber on the mechanical properties and early shrinkage and cracking properties of desert sand concrete was studied,so as to find the optimal mixing amount and proportion of hybrid fiber in desert sand concrete.By comparing the development of its mechanical properties,the early cracking trend of mixed fiber sand concrete was analyzed,and the following conclusions were drawn:（1）Fiber content has little effect on compressive strength and static elastic modulus of sand-mixed concrete;but the tensile strength of the concrete is significantly increased;The ratio of tension and compression increases obviously,indicating that the brittleness of concrete mixed with desert sand is improved;With the addition of hybrid fiber,the failure mode of concrete mixed with desert sand is more complete and its integrity is improved.（2）With the increase of mixed fiber content,the moisture evaporation,shrinkage rate and crack resistance grade of concrete mixed with desert sand increased firstly and then decreased.The crack width and total crack area on the specimen surface became smaller and the crack appeared later.The influence of fiber ratio on early shrinkage and crack resistance is less than that of hybrid fiber content.When the two fibers are mixed,the concrete mixed with desert sand has better shrinkage and cracking resistance.（3）The growth rate of tensile strength f_ts/f_ts28 and elastic modulus E/E₂₈ increased rapidly in 3d after mixed fiber was added to sand concrete,and the difference between them decreased with the increase of mixed fiber content and basalt fiber percentage.However,E/E₂₈ was still larger than f_ts/f_ts28,indicating that after mixed fiber was added,The early cracking trend of concrete mixed with desert sand decreases,but there is still a risk of early cracking.更多还原