不同分子结构聚羧酸系减水剂对水泥浆体早期性能的影响

发布时间：2018-10-31 09:25

【摘要】：聚羧酸系减水剂（Polycarboxylate ether type superplasticizer，PCE）具有掺量低、分散性好、分子结构灵活等优点，在现代混凝土中获得了广泛应用。典型的聚羧酸系减水剂有阴离子型聚羧酸系减水剂（Anionic polycarboxylate ether typesuperplasticizer，anPCE）和两性聚羧酸系减水剂（Amphoteric polycarboxylate ethertype superplasticizer，amPCE），其分子结构对水泥浆体早期性能的影响很大。本文中合成了侧链长度、侧链密度不同的anPCE，以及阳离子含量、主侧链桥接基团、侧链长度不同的amPCE，并通过宏观与微观实验相结合的方法，研究了不同分子结构聚羧酸系减水剂对水泥浆体流动性、早期强度、水化放热速率等早期性能的影响。对于阴离子型聚羧酸系减水剂，分子中吸附基团数量、侧链密度相同时，长侧链anPCE的吸附量低，分散能力及分散保持能力强。掺入质量相同情况下，与掺短侧链anPCE水泥浆体相比，掺长侧链anPCE水泥浆体的水化诱导期持续时间较短，早期水泥水化产物生成量较多，早期强度较高。根据Juilland、Nicoleau等提出的C3S早期水化矿相溶解机理，本文推测吸附在C3S表面的anPCE可能会提高此处产生新刻蚀点的能量，减缓C3S的溶解速率，从而延长水泥水化诱导期持续时间。与短侧链anPCE相比，长侧链anPCE的相对分子质量较大，在质量相同情况下，分子数量较少，因此其延缓C3S溶解的程度较小。掺入分子数量相同情况下，掺不同侧链长度anPCE水泥浆体的水化诱导期差异较小。但在水化加速阶段，掺长侧链anPCE水泥浆体的水化放热速率比掺短侧链的慢。因此anPCE在影响C3S溶解的同时可能也影响C3S水化产物成核及生长过程。分子中吸附基团数量、吸附基团与侧链的质量比相同时，侧链较长、侧链密度较低anPCE的吸附量较多，初始分散能力较强。并且掺此类anPCE的水泥浆体较早进入水化加速阶段，早期水泥水化产物生成量较多，水泥浆体早期强度较高。分子中吸附基团数量、侧链长度相同时，与高侧链密度anPCE相比，低侧链密度anPCE的吸附量较多，初始分散能力较强，但分散保持能力较弱，并且会延缓C3A及C3S的水化过程，降低水泥浆体早期强度。对于两性聚羧酸系减水剂，，随着主链吸附基团中阳离子比例提高，amPCE的吸附量先增加后减少。含一定比例（10%，15%）阳离子的amPCE能够促进水泥早期水化，提高水泥浆体早期强度。与桥接基团为醚键的amPCE相比，酯键桥接amPCE的吸附量较少、分散能力较弱。掺酯类amPCE水泥浆体水化速率较快，早期强度较高。随着侧链长度的增加，amPCE的吸附能力及分散能力先上升后下降。侧链较长的amPCE能够促进水泥早期水化，从而提高水泥浆体早期强度。本文系统研究了阴离子型和两性聚羧酸系减水剂对水泥浆体早期性能的影响规律，研究结果有助于进一步了解聚羧酸系减水剂分子结构参数与水泥浆体性能的构效关系，探明聚羧酸系减水剂在水泥水化过程的作用机理，从而为后续聚羧酸系减水剂的分子结构设计及工程应用提供一定理论依据。
[Abstract]:Polyacetal type superplasticizer (PCE) has the advantages of low doping amount, good dispersivity, flexible molecular structure and the like, and is widely applied in modern concrete. Typical polyvinyl alcohol-based water-reducing agents include anionic water-reducing agent (ANPCE) and amphoteric water-reducing agent (amPCE). Its molecular structure has great influence on the early performance of cement paste. In this paper, the length of the side chain, the anPCE with different side chain densities and the amPCE with different cationic content, main chain bridging group and side chain length are synthesized, and the fluidity of the cement slurry is studied by means of combining macroscopic and microscopic experiments. Early strength, hydration heat release rate and other early properties. When the number of adsorption groups in the molecule and the density of the side chains are the same, the adsorption amount of the long-side chain anPCE is low, the dispersing ability and the dispersion are maintained. Compared with the short side chain anPCE cement paste, the hydration induction period of the long side chain anPCE cement slurry has short duration, and the early cement hydration products produce more and early strength compared with the short side chain anPCE cement slurry. According to the mechanism of the early hydration of C3S from Juilland, Nicoleau et al., this paper speculates that the anPCE adsorbed on the surface of C3S may increase the energy of the new etching point here and decrease the dissolution rate of C3S so as to prolong the duration of hydration induction of cement. Compared with the short side chain anPCE, the relative molecular mass of the long side chain anPCE is large, and in the case of the same mass, the number of molecules is small, The hydration-induced phase difference of the length anPCE cement paste with different side chains in the same conditions as the number of molecules is smaller. At the hydration acceleration stage, the hydration heat release rate of the long side chain anPCE cement slurry is lower than that of the short side chain. slow. Therefore, the anPCE may also influence the nucleation and growth of C3S hydration products while affecting the dissolution of C3S. In the process, the number of adsorption groups in the molecule, the mass ratio of the adsorption group to the side chain are the same, the side chain is longer, the side chain density is lower than that of the low anPCE, and the initial dispersion capacity It is strong that the cement paste with such anPCE can enter the hydration acceleration stage earlier, and the early cement hydration products produce more, and the early strength of the cement paste body is high. When the number of adsorption groups in the molecule and the length of the side chain are the same, the adsorption amount of the low-side chain-density anPCE is much larger than that of the high-side chain-density anPCE, the initial dispersion capacity is strong, the dispersion retention capacity is weak, the hydration process of the C3A and the C3S is retarded, For amphoteric polyacrylate water reducer, the adsorption capacity of amPCE is first increased with the increase of cationic proportion in main chain adsorption group. After the increase, the amPCE containing a certain proportion (10%, 15%) of the cation can promote early hydration of the cement and improve the cement slurry. Compared with amPCE with bridging group as ether bond, the adsorption amount of ester bond bridge amPCE is less, The dispersion ability is weak. The hydration rate of cement paste with ester-doped amPCE is faster and early. With the increase of the length of the side chain, the adsorption capacity and the dispersing ability of the amPCE were first increased. LPCE with long side chain can promote early hydration of cement to improve cement slurry In this paper, the influence of anionic and amphoteric water reducing agents on the early properties of cement slurry is studied. The results of this study are helpful to further understand the molecular structure parameters and cement paste of the water reducer. The structure and effect relationship of the performance of the cement and the mechanism of the water reducing agent in the cement hydration process are proved, and the molecular structure design and engineering application of the water reducing agent for the subsequent polymethyl methacrylate water reducing agent are provided.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU528.042.2

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