【作者】 徐鹏；

【导师】 张联盟； 宋仁义； 王传彬；

【作者基本信息】 武汉理工大学 ， 材料学， 2013， 硕士

【摘要】 减水剂是混凝土中最为重要的外加剂,被誉为“混凝土中的液体黄金”,决定着混凝土的使用状况和未来发展趋势。其中,聚羧酸系减水剂有着其他类型减水剂所不具有的优势,如减水率高、水泥分散性好、分子结构的自由度大、生产绿色化等优点。而实际生产过程中,由于混凝土原材料的质量不能得到很好的保证,砂石中的粘土不可避免地会混入到混凝土中,使新拌混凝土的坍落度损失变大,流动性大打折扣,强度也有不同程度的下降,影响了混凝土的工作和使用性能。粘土中主要矿物成分为蒙脱石、高岭土、伊利石等,它们有较强的吸附性能,吸附了部分减水剂,最终降低了混凝土的使用与工作性能。本论文使用新型聚羧酸系减水剂PC2000、蒙脱石与高岭土作为研究对象,研究了蒙脱石、高岭土以及他们的组合与聚羧酸系聚羧酸PC2000之间的吸附速率、吸附量、吸附机理,同时探讨了温度与pH值对它们之间饱和吸附量的影响,以期为解决粘土对聚羧酸系减水剂使用效果的不利影响提供理论支持。通过实验,发现：(1)在常温下,蒙脱石与聚羧酸系减水剂在他们相接触的3.5小时至4小时之间达到近似的平衡,蒙脱石表现出极强的吸附能力,每克蒙脱石对聚羧酸系减水剂的饱和吸附量达到了0.409g,当温度从25℃变化到50℃,饱和吸附量上升,继续变化到80℃时下降,当pH值从7.1变化到11.5时,饱和吸附量一直呈下降的趋势。吸附了聚羧酸系减水剂的蒙脱石,其(001)晶面间距随着吸附量的增加而增大,表明蒙脱石的层间进入了聚羧酸系减水剂分子。空间尺度表明,聚羧酸系减水剂不可能完全插入到蒙脱石的层间,而是支链或者主链的一部分进入到了(001)晶面中。相比于Freundlich方程,Langmuir方程比较适合来模拟这种吸附过程,表明聚羧酸系减水剂在蒙脱石上的吸附是分配作用和表面吸附作用共同作用而以分配作用为主导的吸附过程。(2)高岭土与聚羧酸系减水剂达到近似平衡的时间在4小时至4.5小时,每克高岭土对聚羧酸系减水剂的饱和吸附量为0.009g,当温度从25℃变化到60℃时,饱和吸附量上升,继续变化到80℃又下降,当pH值从7.1变化到11.5时,饱和吸附量一直呈下降的趋势。Langmuir方程和Freundlich方程都比较适合来模拟高岭土与聚羧酸系减水剂之间的吸附过程,说明表面吸附作用和分配作用都是主导因素。(3)蒙脱石与高岭土与聚羧酸系减水剂的共同吸附在4小时左右达到近似的平衡,在组合状态下显示出了比单一组分更高的饱和吸附量,这可能与它们所表现出来的“协同作用”有关系。更多还原

【Abstract】 Water reducing agent has been considered as the "Liquid Gold" and the pillar part in the concrete, plays a key role and determines the trend of concrete in the future. Among them, polycarboxylic copolymer is such outstanding, it has the advantages that other water reducing agents does not had, such as high reducing rate, good dispersion, large degrees freedom in the molecular structure, green process. But during the actually process, the raw materials quality of concrete can’t be very well guaranteed, the clay inevitably mixes into concrete along with sands and stones, it will decline the strength and work ability of concrete. The main mineral in clay is montmorillonite, kaolinite, illite with strong adsorption ability, they absorbed the water reducing agent, then reduced the use and work performance of concrete.Polycarboxylic copolymer PC2000, montmorillonite and kaolinite from Tianjian Damao Chemical Reagent Factory, their adsorption behavior such as adsorption rate, adsorption capacity, adsorption mechanism, the effect of temperature and pH was investigated, to provide the theory supports for soling the problem of clay.Studies shows that montmorillonite and PC2000reaches an approximate balance3.5hours to4hours after their contact at room temperature, montmorillonite showed strong adsorption capacity, Adsorption between montmorillonite and PC2000is0.409g/g. When the temperature changes from25℃to50℃, the saturated adsorption capacity is rising, continue to change to80℃falling, and when the pH changes from7.1to11.5, the saturated adsorption quantity has been a downward trend. The (001) crystal plane spacing of montmorillonite increased with the increase of adsorption capacity, showed that the poly carboxylic acid water reducing agent molecules inserted into the (001) space of montmorillonite, and the space scale indicated that poly carboxylic acid is water reducing agent can’t completely inserted into the montmorillonite layers, but part of the branched chain or main chain into the (001) crystal plane. Comparing with the Freundlich equation, the Langmuir equation is suitable to simulate the adsorption process, showed that poly carboxylic acid water reducing agent in montmorillonite is allocated on the surface absorption effect and the distribution effects, and the distribution effects is dominant. Kaolin and poly carboxylic acid water reducing agent achieved an approximate balance within4hours to4.5hours. The saturated adsorption capacity between kaolinite and poly carboxylic acid water reducing agent is0.009g/g. When the temperature changes from25℃to60℃, the saturated adsorption amount of rising, continue to change to80℃and fall, when the pH changes from7.1to11.5, the saturated adsorption quantity has been a downward trend. Langmuir equation and Freundlich equation is suitable to simulate the adsorption process of kaolin and poly carboxylic acid, surface adsorption and distribution effect is the dominant factor.The mixed and poly carboxylic acid water reducing agent achieved an approximate balance within4hours, and combination condition shows a higher saturated adsorption capacity than a single component, this may related to "Synergy".更多还原