【作者】 杨静；

【导师】 孙建恒； 孟志良；

【作者基本信息】 河北农业大学 ， 结构工程， 2008， 硕士

【摘要】 随着现代土木工程的日益发展,普通混凝土的工作性和耐久性已不能满足要求。怎样有效提高混凝土的工作性和耐久性,扩大混凝土的使用范围,延长混凝土的使用寿命,已经成为国内外专家学者的研究焦点。自密实混凝土就是在此基础上出现的一种以高施工性为突出特点的新型高性能混凝土。它通过粗细骨料、胶结材料、外加剂等的选择和配合比的设计,使混凝土拌合物具有足够的塑性粘度,粗细骨料能够悬浮于胶凝材料浆体中不离析、不泌水,在不用或基本不用振捣的条件下,能够穿过钢筋间隙,能充分填充所有空隙,形成密实而均匀混凝土结构中的一种高性能混凝土。与普通混凝土相比,很多使用高性能自密实混凝土的工程在收缩方面的表现还不尽人意。为了满足高流动性和高稳定性的要求,自密实混凝土往往要求高胶凝材料用量和减水剂掺量、低水胶比、以及低骨料含量,这些因素均增加了自密实混凝土的收缩值。本文采用地方材料,根据固定砂石体积法确定低强度自密实混凝土（C20、C25、C30）初步配合比,利用单因素优化方法,以新拌混凝土的坍落度、扩展度、T₅₀以及7d和28d强度为考核指标,通过大量试验,分析研究不同品种外加剂及掺量对自密实混凝土拌合物工作性能的影响,接着分析研究了粉煤灰掺量对自密实混凝土早期强度（7天和28天）的影响,最后对试验结果进行综合分析,优化配制出了坍落度范围在255mm～270mm之间,扩展度范围在550mm～700mm之间,T₅₀在5s～25s以内,28d抗压强度满足配制强度要求的高流态免振捣的低强度自密实混凝土。同时本文研究了低强度自密实混凝土的收缩特点,采用膨胀剂和固硫渣对自密实混凝土的收缩进行补偿。试验研究膨胀剂对自密实混凝土拌合物的工作性和硬化混凝土强度的影响,在满足工作性及强度要求又能有效补偿自密实混凝土收缩的合理的膨胀剂掺量;试验研究了固硫渣对自密实混凝土拌合物的工作性和硬化混凝土强度的影响,对将固硫渣作为自密实混凝土掺合料的可行性进行初步探讨。更多还原

【Abstract】 With the increasing development of the modern civil engineering, the workability of ordinary concrete and durability have been unable to meet the demand of construction. How to effectively improve the workability of concrete and durability, and expand the use of concrete to extend the service life of concrete, experts and scholars at home and abroad have become the focus of research.Self-Compacting Concrete is one of the new High-Performance Concrete based on the construction of a high for the outstanding feature.Self-Compacting Concrete is obtained through selectioning the aggregate, cement materials, additives, and so on and mix designing. The mixing of SCC had adequacy of plastic viscosity, and the particles of the aggregate can suspension in cementitious material slurry without segregation and bleeding.The mixing can be reinforced through the gap and fully fill all the gaps without no vibration or do not have the basic conditions so that forming dense and uniform concrete.Compared with ordinary concrete, many of the use of High-Performance Self-Compacting concrete projects in the performance of contraction also unsatisfactory. In order to meet liquidity requirements and high stability, SCC tend to demand high cementitious material usage and water reducer volume, low water-cement ratio, and low aggregate level. All these factors have increased the contraction value of SCC.In this paper, using local materials, according to fixed volume of sand and gravel law preliminary mix for Self-Compacting Concrete (C20, C25, C30)is determined. A conclusion, which is that influence different varieties and volume of admixture to fresh concrete workability and different volume of fly ash to early strength is made through using single-factor testing method and regarding slump,slump flow, T50, 7d and 28d strength as feedback indexs, and making range analysis to experimental results. At last,the experiment successfully obtains low-strength SCC with high liquidity and no vibration,which has the characters of slup between 255mm～270mm,slup flow between 550mm～700mm, T50 between 5s～25s and enough 28d strength.At the same time in this paper, experimental study are done on low-intensity SCC shrinkage characteristics and the contraction of SCC compensation using expanders and FBC ashes. It is also studied the impaction on expansion admixture for workability for SCC mixing, the impact of hardening concrete strength and reasonable volume of compensation admixture to meet the demands; preliminary feasibility study is done whether FBC ashes can be a kind of SCC admixture by experimental study the impaction on workability for SCC mixing and strength of hardening concrete.更多还原