【作者】 赵波；

【导师】 杨杨；

【作者基本信息】 浙江工业大学 ， 结构工程， 2015， 硕士

【摘要】 干混砂浆因其质量控制严格、性能稳定、节能环保,得到了越来越广泛的应用。但其中的干混抹灰砂浆(以下简称抹灰砂浆)在工程应用中,常常会产生开裂,其抗裂性能的研究及评价成为干混抹灰砂浆推广应用的重要课题。本文以M5、M10、M15、M20强度等级的抹灰砂浆为研究对象,通过对其基本力学性能、非约束状态下的干燥收缩性能和约束状态下的开裂特性的试验研究和综合分析,提出了一种评价干混抹灰砂浆抗裂性能的圆环约束试验方法。在本研究范围内,可得出以下结论:(1)在稠度范围相同的条件下,随抹灰砂浆中水泥用量的增加,抗压强度与抗折强度均会相应增大;同一强度等级的砂浆稠度范围不同时,强度随用水量的增加而减小,干燥条件下的强度低于标准养护条件下的强度。(2)随水泥含量增加,非约束状态下砂浆的干燥收缩以及约束状态下的棱柱体限制收缩增大。约束状态下的棱柱体收缩的开裂指数表明,砂浆开裂的可能性随水泥含量的增加而增大。(3)不同强度等级的砂浆养护时间相同时,失水率随强度等级的增大而降低。同一强度等级的砂浆失水率随养护时间的增加而降低。砂浆干燥期间,其收缩长度变化率和失水率是大致成正比。(4)圆环约束收缩试验中,同种砂浆养护时间越长,干燥时约束钢环应变发展速率越快且开裂时约束钢环的最大应变更大,但开裂时间相差不大。养护时间相同时,强度等级越大,干燥时约束钢环应变发展速率越快且开裂时间越短,但砂浆开裂时约束钢环的最大应变相差不大。(5)圆环约束试验中的砂浆试件内侧应力大于外侧应力,圆环砂浆试件裂缝可能是由内侧向外侧发展的。应力发展速率随约束钢环厚度的增加而降低。在约束钢环厚度相同的前提下,同种强度等级砂浆养护时间越长,干燥时内部应力发展速率越快,开裂时试件内部的最大应力更大;砂浆养护时间相同时,强度等级越大,干燥时内部应力发展速率越快,开裂时间越短。更多还原

【Abstract】 Because of the strict quality control, stable performance, energy conservation, environmental protection, Dry-mixed mortar has been more and more widely used. But cracking often occur in the Dry-mixed plastering mortar(Hereinafter referred to as plastering mortar), therefore research and evaluation of the crack resistance become an important subject in application of Dry-mixed plastering mortar.In this paper, the research object is the plastering mortar with strength grade M5, M10, M15 and M20. Based on the experimental research and comprehensive analysis of basic mechanical properties, drying shrinkage performance under the no constraint condition, cracking characteristics under the constraint conditions, the ring constraint test method was proposed to evaluate cracking resistance for plastering mortar. Within the scope of this study, the following conclusions can draw:(1) In the case of same range of the consistency, with the increase in the amount of cement in the plastering mortar, compressive strength and flexural strength increase accordingly; in the case of same strength grade and the different consistency, strength decreases when the water are increase. For the same mortar, strength under the dry condition is lower than that under standard curing condition.(2) With the increase of cement content, the drying shrinkage of mortar under the no constraint and constraint conditions increase. The shrinkage cracking index under constraint condition shows that the possibility of cracking of mortar increases with the increase of cement content.(3) In the case of same curing time, the water loss rate in mortar decreased with strength grade increasing. in the case of same strength grade, the water loss rate decreased with curing time increasing. During the drying period, the shrinkage rate is roughly proportional to the water loss rate.(4) The results obtained in ring constraint shrinkage test showed that, the longer the curing time, the faster development rate of the steel ring strain is, and the bigger the maximum strain of steel ring at the cracking time is, but the cracking time is almost same. In the case of same curing time, with the increase of strength grade the steel ring strain rate become faster and the cracking time become shorter, but there is no obvious difference between the maximum strain of steel ring when mortar cracking.(5) The stress inside of the steel ring is larger than outside according to ring constraint test. It means that the cracking in ring mortar specimen may be developed from the inside to the outside. During drying of the mortar, the stress development rate decreased when the thickness of the steel ring increase. When the thickness of the steel ring are same, the longer the curing time, the faster the development rate of internal stress is, and the bigger the maximum stress at the cracking time is. When the curing time is same, the greater the strength grade, the faster development rate of the stress is, and the shorter cracking time is.更多还原