含泥量对掺聚羧酸减水剂混凝土性能的影响

发布时间：2019-03-23 17:57

【摘要】：聚羧酸减水剂是制备高性能混凝土不可或缺的组分,也是混凝土外加剂的主要发展方向和研究热点。砂中含泥量会对掺聚羧酸减水剂混凝土的性能产生不良影响。现关于含泥量对掺聚羧酸减水剂混凝土性能影响的研究已有不少,但大多集中在新拌混凝土的工作性及力学性能,而且含泥量对掺聚羧酸减水剂配制的不同强度等级混凝土性能影响的对比研究尚不多见。本文研究了不同含泥量对掺聚羧酸减水剂的低、中、高三种强度等级混凝土性能的影响,并探究其影响机理,旨在为改善和解决含泥量对掺聚羧酸减水剂混凝土的不良影响提供理论依据和技术支撑。采用甲基烯基聚氧乙烯醚(TPEG)为大单体,丙烯酸(AA)、甲基丙烯磺酸钠(SMAS)为小单体,在引发剂过硫酸铵(APS)和侧链转移剂巯基丙酸(MPA)的作用下,制备出分散性及保坍性良好的聚醚类聚羧酸减水剂。使用自制聚醚类聚羧酸减水剂配制不同含泥量的C25、C40及C70三种强度等级的混凝土,系统地研究了含泥量对混凝土工作性、抗压强度、收缩性能、耐久性的影响,研究结果如下:(1)工作性:含泥量对低强C25和中强C40混凝土的工作性影响较大,对高强C70混凝土的工作性影响较小,这与不同强度等级混凝土聚羧酸减水剂的用量有关;从含泥量对不同浓度聚羧酸减水剂的吸附量角度阐释了含泥量对不同强度等级混凝土工作性影响程度差异的原因。(2)抗压强度:C25、C40及C70混凝土分别在含泥量大于7%、3%及1%时不满足其强度等级的要求。高强C70和中强C40混凝土抗压强度对含泥量的敏感程度远大于低强C25混凝土。(3)收缩性能:含泥量对C25、C40和C70混凝土收缩性能影响的趋势基本相同,即对混凝土1d的收缩率基本没有影响,可以减少混凝土3d和7d的收缩率,但混凝土14d后的收缩率变大。混凝土早期收缩率变小的原因是由于泥粉吸附的水分挥发,提高混凝土内部湿度,从而降低混凝土收缩率;后期收缩率增大主要与混凝土的自收缩及孔隙率有关。(4)耐久性:含泥量对混凝土氯离子扩散系数及碳化深度的影响规律与其强度等级成一定的负相关性,含泥量对低强C25、中强C40混凝土抗氯离子渗透性和抗碳化性能的影响明显大于其对高强C70混凝土的影响。含泥量对不同强度等级耐久影响的差异性主要与混凝土结构的密实度、孔隙率及碱度等有关。
[Abstract]:Polycarboxylic acid water reducer is an indispensable component in the preparation of high performance concrete, and it is also the main development direction and research hotspot of concrete admixture. The mud content in sand will have an adverse effect on the performance of concrete mixed with polycarboxylic acid water reducing agent. There have been a lot of researches on the effect of mud content on the performance of concrete with polycarboxylic acid water reducer, but most of them focus on the workability and mechanical properties of fresh concrete. Moreover, the influence of mud content on the performance of concrete with different strength grades mixed with polycarboxylic acid water reducing agent is rare. In this paper, the effects of different mud content on the properties of low, middle and high strength grade concrete mixed with polycarboxylic acid water reducer were studied, and the influence mechanism was explored. The purpose of this paper is to provide theoretical basis and technical support for improving and solving the adverse effects of mud content on polycarboxylic acid superplasticizer concrete. In the presence of ammonium persulfate (APS) and side chain transfer agent (MPA), methyl vinyl ether (TPEG) was used as macromonomer, acrylic acid (AA),) was used as small monomer, and sodium methacrylic sulfonate (SMAS) was used as small monomer. Polyether polycarboxylic acid water reducer with good dispersibility and slump-proof property was prepared. The effects of mud content on workability, compressive strength, shrinkage and durability of concrete with different strength grades of C25, C40 and C70 were systematically studied by using self-made polyether polycarboxylic acid water reducer. The results are as follows: (1) workability: the influence of mud content on workability of low strength C25 and medium strength C40 concrete is greater than that of high strength C70 concrete, which is related to the amount of polycarboxylic acid water reducer in concrete of different strength grades; The influence of mud content on the workability of concrete with different strength grades was explained from the point of adsorption capacity of different concentration of polycarboxylic acid water reducer. (2) compressive strength: C25, C40 and C70 concrete with mud content greater than 7%, respectively. 3% and 1% do not meet the strength grade requirements. The compressive strength of high strength C70 and medium strength C40 concrete is much more sensitive to mud content than that of low strength C25 concrete. (3) shrinkage performance: the effect of mud content on the shrinkage performance of C25, C40 and C70 concrete is the same as that of low strength C25 concrete. It can reduce the shrinkage of concrete for 3 days and 7 days, but the shrinkage rate of concrete increases after 14 days. The reason why the early shrinkage rate of concrete becomes smaller is due to the volatilization of moisture absorbed by mud powder, which improves the internal humidity of concrete, and thus reduces the shrinkage rate of concrete. The increase of shrinkage is mainly related to self-shrinkage and porosity of concrete. (4) durability: the influence of mud content on chloride diffusion coefficient and carbonation depth of concrete is negatively correlated with its strength grade. The influence of mud content on chloride ion permeability and carbonation resistance of low-strength and medium-strength C40 concrete is greater than that of high-strength C70 concrete. The difference of the influence of mud content on the durability of different strength grades is mainly related to the compactness, porosity and alkalinity of concrete structures.
【学位授予单位】：西安建筑科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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