集料附含粘土对混凝土高效减水剂的作用影响及机理研究

The existence of microfines in aggregates is inevitable through the current aggregate production. Studies showed that clay is the most primary component in micofines that influences the properties of concrete and its effect on the dispersion of high-range water reducing agent (HWRA) is prominate. However, present studies mainly focus on the effect of single clay mineral or clay on the performances of HWRA or concrete with HWRA, influencing factors such as the mineral compositions of clay and their characteristics, relationship between clay mineral and clay, were not fully considered.The representativeness and mineral compositions of clay in aggregate will be fully considered in this proposed project. The competitive and intercalative adsorptions of HWRA on clay and cement particles and their adsorption kinetics will be studied based on the study of the interaction of clay in aggregate with various kinds of solutions. The effects of clay on the steric and electrostatic repulsions will be investigated through studies of the agglomeration of HWRA, the degree of chain stretching, the hydrodynamic radius or the mean square radius of gyration, and ZETA potential etc.. The influence of clay mineral, simulative clay and clay in aggregate on the performance of HWRA will be explored through investigations of the action process and action mechanism of HWRA. The predictive model of the influence of clay on the performance of HWRA will be proposed, which may act as a theoretical guide for the application of low-quality aggregate with a high-clay content in modern concrete.

集料生产现状表明集料含泥是不可避免的，泥中的粘土是对混凝土性能影响最显著的组分，集料附含粘土对高效减水剂的减水分散作用的影响尤其明显。现有研究集中在粘土、单粘土矿物的掺量对高效减水剂作用和掺高效减水剂混凝土性能影响，但未充分考虑集料附含粘土矿物组成与特性、单粘土矿物与粘土关联性等因素。项目充分考虑集料附含粘土代表性和矿物组成，以集料附含粘土与不同溶液相互作用后的特性为基础，研究粘土、水泥颗粒对高效减水剂的竞争吸附、插层吸附等吸附行为与吸附动力学；通过研究高效减水剂的聚集行为、链伸展程度、流体力学半径与均方旋转半径、ZETA电位等，表征粘土对高效减水剂的空间位阻与静电斥力的影响；从减水剂的作用历程与机理两个层面探明单粘土矿物、模拟粘土、集料附含粘土对高效减水剂作用的影响，采用数学方法建立粘土对减水剂作用影响的预测模型，为研发含泥量高或超标的低品质集料在现代混凝土的应用技术提供理论指导。

集料生产使用现状表明集料含泥不可避免，泥中粘土是对混凝土性能影响最显著的组分之一，其对聚羧酸高效减水剂的减水分散作用的影响尤其明显。现有研究主要集中在粘土、单粘土矿物的量对聚羧酸减水剂减水分散作用和掺聚羧酸减水剂混凝土性能影响，但未充分考虑粘土的矿物组成与特性、单粘土矿物与粘土关联性等因素。.项目充分考虑集料附含粘土代表性和矿物组成、及其与水泥混凝土溶液相互作用后的特性为基础，重点研究泥中所含的不同粘土及其矿物组成等因素对聚羧酸减水剂分散性能的影响，并结合各种粘土的不同物理化学性质及粘土在水泥混凝土液相体系中的性质探究了其影响机理，粘土影响聚羧酸减水剂分散性能的主要机理是粘土吸水膨胀，消耗拌合用水和减水剂，其中蒙脱土组分最为明显；蒙脱土吸水膨胀最大，消耗拌合用水最多，且膨胀后的蒙脱土对聚羧酸减水剂分子的层间吸附导致吸附减水剂最多，二者共同作用是其明显影响聚羧酸减水减水分散性能的主要原因。同时还研究粘土的量和存在形式对聚羧酸减水剂分散性能、砂浆体积稳定性和力学性能的影响，并利用X-射线衍射仪、傅立叶红外光谱仪、微量热仪、电子扫描显微镜和显微硬度仪等分析手段对粘土对水泥水化的影响和界面过渡区的影响，以此探讨其影响机理。.在探明粘土影响聚羧酸减水剂减水分散性能影响因素和作用机理后，从释放粘土吸附的拌合水、选择吸附能力强而优先被粘土吸附的助剂从而减少粘土对聚羧酸减水剂的吸附、防止粘土膨胀以减少对拌合水及聚羧酸减水剂的吸附三个技术路线，通过宏观试验研究系统研究了陶瓷减水剂、粘土吸附剂和粘土防膨剂作为添加剂降低粘土对聚羧酸减水剂负效应的效果，微观试验探讨了添加剂的抑制机理，研发了一种屏蔽粘土对聚羧酸减水剂负效应的助剂，以此建立一套有效的技术方案。.在试验研究的基础上，运用模拟分析方法，将粘土矿物组成对粘土影响聚羧酸减水剂减水分散性能、对助剂降低粘土对聚羧酸减水剂负效应的作用效果进行回归分析，对粘土产生的负效应和助剂对不同矿物组成粘土负效应的改善效果进行模拟、回归，建立了良好的定量关系，提高了研究结果的普适性。.项目通过试验与模拟研究粘土降低聚羧酸减水剂减水分散性能的影响因素和作用机理、改善粘土降低聚羧酸减水剂减水分散性能的技术措施与作用机理等重要内容，阐明粘土、聚羧酸减水剂和助剂三者之间相互作用的关系，为含泥量高或超标的低品质集料在现代混凝土的应用技术提供试验指导和理论参考。