【作者】 王志华；

【导师】 周茗如；

【作者基本信息】 兰州理工大学 ， 结构工程， 2008， 硕士

【摘要】 目前,混凝土已经逐渐成为人类社会不可缺少的基础材料。国内外建筑工程中所需的混凝土材料有很大一部分来自商品混凝土搅拌站供应。由于商品混凝土具有流动性高、胶凝材料用量多、砂率大等特点,导致商品混凝土收缩偏大,容易出现早期裂缝。我国商品混凝土技术发展很不平衡,西北地区商品混凝土早期裂缝问题较为严重,本文针对兰州市商品混凝土的发展现状,结合气候特点,在配合比设计、原材料甄选、搅拌及施工工艺优化等方面,实现较好控制早期裂缝的目标。本文围绕商品混凝土早期收缩和裂缝这一主题,从形成机理、试验研究、理论探索三个方面对这一当前亟待解决的课题进行了研究。主要讨论了以下内容:(1)对商品混凝土存在的早期收缩和早期裂缝,进行了分析和概述,结合国内外的参考资料,研究了早期裂缝产生的原因和基本形式。(2)进行了单掺聚丙烯纤维、单掺膨胀剂、复掺聚丙烯纤维和膨胀剂的商品混凝土早期收缩试验研究。(3)通过平板试验,研究了水胶比、矿物掺合料、早期养护对商品混凝土早期裂缝的影响。(4)针对水胶比、砂率、矿物掺合料及聚丙烯纤维等因素对商品混凝土早期裂缝的影响,采用正交试验法对商品混凝土早期裂缝进行了试验研究。结果表明,本文研究控制商品早期裂缝的措施是有效的,为今后同样问题的出现提供了方便,可以推广使用。更多还原

【Abstract】 Nowadays,concrete gradually has become one of the necessary basic materials to the human beings.The concrete used by the construction project is usually supplied by the ready-mixed concrete factory.Owing to the larger liquidity,the cementitious material and the sand-aggregate ratio are large,ready-mixed concrete has large shrinkage and emerges early age cracking easily.Ready-mixed concrete technology has been developing differently in different areas of China.In northwest,the early age cracking of ready-mixed concrete is very serious.The character of climate in Lanzhou are analyzed and some approach are discussed to the goal of how to control the early age cracking due to design of mixture proportions,material selection,mix round and construction technics optimization according to the developmental actuality of ready-mixed concrete technology in Lanzhou.This paper studies the early age shrinkage and cracking of ready-mixed concrete and it is discussed from three aspects including formation mechanics,experimental investigation and theoretical research.The following problems are mainly discussed in this dissertation.(1)First,make an analysis and a summary of the early age shrinkage and cracking in ready-mixed concrete.With the reference to literature both at home and abroad,study the basic forms of early age cracking and reasons why cracking emerge.(2)The paper proceed early age shrinkage experiments on the ready-mixed concrete(including only polypropylene fiber in the ready-mixed concrete,only expansive admixture in the ready-mixed concrete,both polypropylene fiber and expansive admixture in the ready-mixed concrete).(3)Through the slab test,we research the influence of early age cracking of ready-mixed concrete from the water binder radio varieties,mineral admixture and early age curing.(4)Adopting the method of orthogonal experimental design in the early age cracking of ready-mixed concrete,study was carried out on effect of early age cracking of ready-mixed concrete on water binder radio varieties,sand-aggregate ratio,mineral admixture and polypropylene fiber.The experiment results indicate that the control methods on early age cracking of ready-mixed concrete are effective,it provides convenience for the similar problem and their application may be extended.更多还原