【作者】 孙栋梁；

【导师】 王智；

【作者基本信息】 重庆大学 ， 材料科学与工程， 2009， 硕士

【摘要】 目前聚羧酸高效减水剂在国内高性能混凝土中的应用已基本普及,但在国内相当数量的预拌混凝土企业中却应用甚少。许多研究致力于研究如何利用聚羧酸高效减水剂配制高性能混凝土,但对聚羧酸高效减水剂在普通预拌混凝土中的研究及应用情况相对较少。鉴于此,本论文针对目前聚羧酸高效减水剂在预拌混凝土应用中存在的一些问题进行了系统研究。本文通过系统研究预拌混凝土中原材料组分和混凝土配合比对聚羧酸高效减水剂塑化效果的影响,发现聚羧酸高效减水剂受水泥、粉煤灰等原材料变化的影响较为敏感,聚羧酸高效减水剂的使用有效性受胶凝材料用量、砂率等混凝土配合比参数依赖性强,与常用减水剂、膨胀剂等其它外加剂组分相容性差等。这些问题是影响聚羧酸高效减水剂在预拌混凝土中应用的主要因素。通过对比研究掺加聚羧酸和萘系高效减水剂的预拌混凝土性能,发现相同配合比情况下,掺聚羧酸高效减水剂的混凝土不仅可以提高预拌混凝土拌合物的坍落度,同时坍落度损失率较萘系高效减水剂减少15～20%,而且可以提高硬化混凝土强度约10%,收缩可减低10%~20%。结合对影响聚羧酸高效减水剂塑化效果的主要因素的研究,本文以常用萘系高效减水剂混凝土配合比为参比对象,通过正交试验,得到了重庆地区掺聚羧酸高效减水剂的混凝土配合比中胶凝材料总用量可减少约3.0%,其中水泥用量减少约6%,矿物掺合料用量提高约8%,砂率提高约0.5%;用水量减少约6%。结合工程应用实际,分析并解决了聚羧酸高效减水剂在预拌混凝土应用中存在的储存聚羧酸高效减水剂容器管道易受腐蚀、混凝土拌合物工作性瞬时损失大和二次添加聚羧酸高效减水剂后混凝土易出现泌水等问题。在不影响减水率的前提下,调整PC溶液至弱碱性(pH=7.5),以此解决了聚羧酸高效减水剂对储存罐、管道的腐蚀问题;通过添加适量引气剂可弥补因粉煤灰烧失量高而造成的工作性瞬间损失大的问题;通过引入木质素磺酸盐解决聚羧酸高效减水剂二次添加后混凝土拌合物离析泌水的问题等。最后本文根据高附加值混凝土的发展方向,结合重庆地材,通过掺加聚羧酸高效减水剂配制了C30低强自密实混凝土、C50清水混凝土和C80高强混凝土,并成功应用于工程实践。更多还原

【Abstract】 Nowadays, polycarboxylate superplasticizer (PC) has been widely used in high performance concrete in China, but it is hardly used in the ready-mixed concrete industry. Most researchers have paid their attentions on how to prepare high performance concrete with PC. It should be noted that there is little effect have been made to investigate its use in plain ready-mixed concrete, and there is no paper published on this subject. Thus, the research on the application of PC in the ready-mixed concrete is systematically studied in this thesis.The factors (i.e., raw materials, common used admixtures and mix proportions) that influence the application of PC in ready-mixed concrete were experimentally studied. It showed that its performance was sensitively influenced by the factors such as properties of cement and fly ash, poor compatibilities with the commonly used water-reducers and expanding agents, sand ratio and mix proportion. These problems have become the main factors that seriously limit the use of PC in ready-mixed concrete.By comparing the properties of ready-mixed concretes containing PC and naphthalene water reducer, it showed that mix with PC had a higher slump, as well as a reduction of slump loss of 15～20%. At the same time, an 10%-improvement of strength and 10%~20%-reduction of shrinkage can be obtained. Based on the main factors that influence the plasticizing effects of PC, the change law of PC concrete mix design was studied by orthogonal design with naphthalene-based mix design as the reference. The change law is shown as following: a reduction of binder to 3% degree ( a reduction of cement to 6% degree, an enhancement of mineral mixtures to 8%), an improvement of sand ratio to 0.5% and a reduction of water to 6% degree.Then, the practical problems of using PC in ready-mixed concrete industry (the corrosion risks of PC containers and pipes, the great immediate loss of mix workability and bleeding of the second addition of PC, etc.) were analyzed and solved. The problems of the corrosion of PC containers and pipes can be solved by adjust the PC solution to a weak alkaline environment (pH=7.5); the problem of the great immediate loss of mix workability due to the high loss of ignition of fly ash can be solved by adding air entraining agent to a certain degree; the problem of bleeding of the mix after the second addition of PC can be solved by introduction of lignosulphonate. Finally, the self-compacting plain concretes of the low(C30), high(C50) grades and the high strength concrete (C80) were prepared according to the development routine of high-valued ready-mixed concrete by using the local materials of Chongqing, and they were successfully used in practice.更多还原