微波效应下托贝莫来石的结构形成机理与调控

Microwave curing technology can be used to manufacture aerated concrete due to its advantages including uniform heating and fast heating speed. It can greatly shorten curing time, reduce energy consumption and save production cost, which conforms to the requirements of energy saving and emission reduction that our country strongly advocates. However, during the microwave heating that is different from the conventional heating, microwave effects are generated, which include thermal effects and non-thermal effects. Due to the existence of non-thermal effects, the formation and structure of tobermorite and aluminum substituted tobermorite (Al-tobermorite) that are the main hydrates of aerated concrete may be affected, thus affecting the structure and mechanical properties of aerated concrete. In this project, under autoclaved curing heated by microwave, influence of different microwave frequencies, autoclaved temperatures and reaction time on the crystallinity, crystal size, crystal structure and morphology of tobermorite and Al-tobermorite will be investigated, and then dynamic models of the formation of tobermorite and Al-tobermorite will be established, based on which the working mechanism of microwave effects can be identified; influence of various influencing factors on the structure and composition of hydrates of aerated concrete will be studied, and then the internal relationship among the three factors that are influencing factors, structure and mechanical properties. This project aims to make a theoretical breakthrough in the microwave effect and working mechanism of microwave curing technology, providing theoretical support for applying microwave heating technology to manufacture aerated concrete.

微波养护技术具有加热均匀、速度快等优点，用于加气混凝土的制备可显著缩短养护时间、降低生产能耗、节约生产成本，符合国家大力提倡的节能减排要求。在微波加热过程中形成了与常规加热方式不同的微波效应，包括热效应和非热效应。由于微波非热效应的存在，加气混凝土主要水化产物托贝莫来石晶体的形成和结构可能会受到影响，从而影响加气混凝土的结构和力学性能。本项目通过研究在微波蒸压条件下，不同微波频率、蒸压温度和反应时间对托贝莫来石、铝代托贝莫来石结晶度、晶粒大小、晶体结构和微观形貌的影响规律，建立托贝莫来石、铝代托贝莫来石形成的动力学模型，揭示微波效应的工作机制；通过研究在微波蒸压条件下，不同调控因素对加气混凝土硬化体结构形成和产物组成的影响，明晰调控因素-结构-力学性能三者之间的内在联系。项目旨在微波养护技术的微波效应和工作机制方面做出突破，为微波技术制备加气混凝土提供理论基础。

为了减少制备托贝莫来石的能耗和碳排放、缩短生产时间，相比较而言，微波水热合成技术具有更加突出的优势。首先，研究了不同液固比、不同合成时间、不同反应温度对托贝莫来石形成与结构的影响；其次，研究了不同Al/Si比对铝代托贝莫来石形成与结构的影响；再次，研究了不同合成时间对粉煤灰基托贝莫来石形成与结构的影响；最后，研究了不同Cu/Ca比对铜代托贝莫来石结构和重金属铜去除率的影响，探究了微波效应的作用机制。主要研究结论如下： 1）微波水热合成托贝莫来石的时间仅为传统水热合成时间的9%，但结晶度不如传统水热合成的样品，微波水热合成托贝莫来石的形貌为小片状堆叠成的蜂窝状晶体，传统水热合成托贝莫来石为晶须状。2）制备铝代托贝莫来石的合适Al/Si比为0.15，微波水热合成的铝代托贝莫来石比表面积、孔容、孔径均大于传统水热合成的铝代托贝莫来石；制备的铝代托贝莫来石结构中，铝取代了Q2与Q3位置的硅，且随着铝离子的掺量增加，铝代托贝莫来石的结晶度增大，同时晶格常数c值变大。3）粉煤灰基托贝莫来石的主要产物为铝代托贝莫来石，呈长片状，相比较而言，微波水热合成的粉煤灰基托贝莫来石晶体较细、平均孔径较小、比表面积大，合成时间仅为传统水热合成时间的一半。4）微波水热合成托贝莫来石固化重金属铜，可将重金属铜固定在托贝莫来石晶格中，固化率高达99%，避免了传统物理吸附法去除重金属铜离子带来的二次污染问题。研究结果为利用微波技术制备以托贝莫来石为主要产物的加气混凝土提供一定理论依据。