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本文回顾了膨胀和自应力水泥发展以及对水泥石的硫铝酸盐膨胀研究的历史。介绍了建材研究院水泥所物化室自六十年代初至最近关于水泥石硫铝酸盐膨胀的研究结果。认为:1.在水泥石硬化初期形成的钙矾石起强度骨架作用,在水泥石具有一定强度后,继续形成的钙矾石才起膨胀作用;不管形成钙矾石的Al_2O_3、CaO、SO_3的来源如何,不管液相中 CaO的浓度是饱和还是不饱和,所形成的钙矾石均能引起膨胀。2.水泥石的硫铝酸盐膨胀时产生的自应力值和水泥石结构与下述条件有关:钙矾石形态(取决于液相CaO浓度)、数量、形成钙矾石时的水泥石强度;与钙矾石同时生成的胶凝相的形成方式、数量、形态以及混凝土的限制条件。3.水泥石液相中CaO低于饱和浓度时,某些铝酸盐矿物形成了膨胀性较小的钙矾石并在同一反应中形成了水化氧化铝凝胶,得到的水泥石的显微结构致密,强度和膨胀协调发展,混凝土的自由膨胀率和限制膨胀率的比值较小,有利于获得高自应力值及高气密性的自应力水泥混凝土。用上述论点,讨论了与形成钙矾石有关的膨胀现象和理论,展望化学予应力逐步赶上机械予应力及大幅度提高水泥制品抗气渗性能的前景。
This article reviews the history of expansion and self-stressed cement development and the study of sulphoaluminate expansion of cement stone. The results of research on the sulphoaluminate expansion of cement stone from the early 1960s to the most recent time were introduced. It is believed that: 1. The ettringite formed in the early hardening stage of cement stone plays an important role in strengthening the framework. After the cement stone has a certain strength, the ettringite that continues to form will only swell; regardless of the formation of ettringite, Al_2O_3, CaO, SO_3 Whatever the source, whether the concentration of CaO in the liquid phase is saturated or unsaturated, the formed ettringite can cause swelling. 2. The self-stress value of cementite sulphoaluminate when it expands and the cement stone structure are related to the following conditions: ettringite form (depending on liquid-phase CaO concentration), quantity, cement stone strength when ettringite is formed. The formation of the gelling phase formed at the same time as ettringite, the number, the morphology, and the confinement conditions of the concrete. 3. When the CaO content in the liquid phase of the cement is lower than the saturation concentration, some aluminate minerals form a less swellable ettringite and form a hydration alumina gel in the same reaction. The dense microstructure, the coordinated development of strength and expansion, the ratio of the free expansion rate of the concrete and the limiting expansion rate are small, and it is beneficial to obtain the self-stressing concrete with high self-stress value and high air tightness. Using the above arguments, the expansion phenomena and theories related to the formation of ettringite are discussed. It is expected that the chemical prestress will gradually catch up with the mechanical prestressing force and greatly improve the anti-permeability performance of cement products.