不同羧基密度聚羧酸减水剂对水泥石孔结构的影响（英文）
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摘要
通过水溶液自由基聚合法合成了不同羧基密度的聚羧酸减水剂,并对所合成聚羧酸减水剂分子结构进行表征,研究了不同羧基密度的聚羧酸减水剂对硬化水泥砂浆孔结构及力学强度的影响。结果表明:水泥砂浆抗压强度与其孔隙率成负相关性,但当孔隙率相同时,分级孔分布显著影响水泥砂浆抗压强度。随着聚羧酸减水剂中羧基密度的增加,聚羧酸减水剂分散性能及引气性能显著增加。当聚羧酸主链羧基密度为6时,水泥砂浆中孔隙率达到最大值。聚羧酸减水剂引入水泥砂浆中的气泡会显著改变硬化砂浆的分级孔分布,显著增加中小孔(200–500μm)的比例,减少大孔(1 200–1 600μm)比例。说明聚羧酸减水剂能够显著改善硬化砂浆孔径分布,使得硬化水泥砂浆中孔径分布更加细小化。砂浆孔结构参数与抗压强度多元线性拟合关系表明,为了提高砂浆力学性能,应采用总引气量小的聚羧酸减水剂,而当总引气量接近时,应优先选择引入分级孔(100–500μm)含量较高的聚羧酸减水剂。
A series of polycarboxylate(PCE) superplasticizers with different carboxylic densities have been synthesized through aqueous radical copolymerization methods,and the molecular structures of these self-synthesized PCEs were characterized and verified. Effects of PCEs with different carboxylic densities on the pore structure as well as mechanical performance of hardened cement mortar were systematically analyzed. The results show that the mechanical strength of hardened cement mortar is negatively correlated with the porosity. With the same porosity in the hardened cement mortar, the graded pore distribution significantly influences the compressive strength of the hardened cement mortar. With the increase of carboxylic density in the backbone, the air entraining capability of PCEs enhances, and when the carboxyl density of PCE gets to 6, the porosity of the hardened cement mortar achieves to the highest. The entrained bubbles by PCEs into the hardened cement mortar remarkably affect the graded pore distributions, with increased proportion of small and median pores(200–500 μm) and decreased proportion of large pores(1 200–1 600 μm). This indicates that PCEs can significantly improve the pore size distribution, resulting in more uniform and finer pores in the hardened cement mortar, which will be beneficial to the mechanical performance as well as durability of hardened cement mortar. The multiple linear regression result indicates that PCEs entraining low porosity into cement mixture should be preferentially chosen in order to improve the mechanical performance. With similar porosity in hardened cement, the graded proportion of pores between 100–500 μm should be enhanced.
A series of polycarboxylate(PCE) superplasticizers with different carboxylic densities have been synthesized through aqueous radical copolymerization methods,and the molecular structures of these self-synthesized PCEs were characterized and verified. Effects of PCEs with different carboxylic densities on the pore structure as well as mechanical performance of hardened cement mortar were systematically analyzed. The results show that the mechanical strength of hardened cement mortar is negatively correlated with the porosity. With the same porosity in the hardened cement mortar, the graded pore distribution significantly influences the compressive strength of the hardened cement mortar. With the increase of carboxylic density in the backbone, the air entraining capability of PCEs enhances, and when the carboxyl density of PCE gets to 6, the porosity of the hardened cement mortar achieves to the highest. The entrained bubbles by PCEs into the hardened cement mortar remarkably affect the graded pore distributions, with increased proportion of small and median pores(200–500 μm) and decreased proportion of large pores(1 200–1 600 μm). This indicates that PCEs can significantly improve the pore size distribution, resulting in more uniform and finer pores in the hardened cement mortar, which will be beneficial to the mechanical performance as well as durability of hardened cement mortar. The multiple linear regression result indicates that PCEs entraining low porosity into cement mixture should be preferentially chosen in order to improve the mechanical performance. With similar porosity in hardened cement, the graded proportion of pores between 100–500 μm should be enhanced.
引文
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[2]PLANK J,SCHROEFL C,GRUBER M,et al.Effectiveness of polycarboxylate superplasticizers in ultra-High strength concrete:the importance of PCE compatibility with silica fume[J].J Adv Concr Technol,2009,7(1):5-12.
[3]BROOKS J J.Influence of mix proportions,plasticizers and superplasticizers on creep and drying shrinkage of Concrete[J].Mag Concr Res,1989,41(148):145-153.
[4]BANFILL P F G.A viscometric study of cement pastes containing superplasticizers with a note on experimental-techniques[J].Mag Concr Res,1981,33(114):37-47.
[5]FAN W,STOFFELBACH F,Rieger J,et al.A new class of organosilane-modified polycarboxylate superplasticizers with low sulfate sensitivity[J].Cem Concr Res,2012,42(1):166-172.
[6]YAMADA K,TAKAHASHI T,HANEHARA S,et al.Effects of the chemical structure on the properties of polycarboxylate-type superplasticizer[J].Cem Concr Res,2000,30(2):197-207.
[7]Zhang Y R,KONG X M,LU Z B,et al.Effects of the charge characteristics of polycarboxylate superplasticizers on the adsorption and the retardation in cement pastes[J].Cem Concr Res,2015,67:184-196.
[8]LI S,WEN Z.Dispersibility and air entraining performance of polycarboxylate-type water reducers[J].J Chin Ceram Soc,2009,37(4):616-621.
[9]HE Y,ZHANG X,KONG Y,et al.Influence of polycarboxylate superplasticizer on rheological behavior in cement paste[J].J Wuhan Univ Technol:Mater Sci,2018,33(4):932-937.
[10]GAO H,ZHANG X,ZHANG Y.Effect of the entrained air void on strength and interfacial transition zone of air-entrained Mortar[J].JWuhan Univ Technol:Mater Sci,2015,30(5):1020-1028.