Design and synthesis of macrocyclic ligands for specific interaction with crystalline ettringite and demonstration of a viable mechanism for the setting of cement
作者:Jonathan L. W. Griffin、Peter V. Coveney、Andrew Whiting、Roger Davey
DOI:10.1039/a902760b
日期:——
Cementitious materials are among those most widely used by mankind while being among the least well understood. The detailed physicochemical processes involved in the hydration and setting of cement slurries are very complex, and a clearly defined quantitative account is still lacking; indeed, even the composition of the cement powder itself is not known exactly. Still less has there been any understanding of the mechanism by which numerous known retarders of the cement setting process act. In this article, we detail the synthesis of novel macrocyclic organophosphonate retarders 1a and 2a which were developed by rational methods. Attempts to synthesise these compounds as phosphonate ester derivatives were universally unsuccessful, however direct modification of the parent hexaaza- (3) and trioxatriaza-18-crown-6 (5) derivatives was successful, to provide the phosphonic acids 1b and 2b respectively. Subsequent testing of these compounds showed their ability to inhibit the growth of crystalline ettringite and delay the setting of cement. These results support the hypothesis that the formation of crystalline ettringite is the rate determining step in the setting of cement.
水硬性材料是人类使用最广泛却最不为人所了解的材料之一。水泥浆体的水化和凝结涉及的详细的物理化学过程非常复杂,目前仍缺乏明确的定量解释;事实上,甚至连水泥粉体的成分也无法确切知晓。更不用说,对于已知的大量抑制水泥凝结过程的缓凝剂的作用机理也缺乏了解。在本文中,我们详细介绍了新型大环有机膦酸酯缓凝剂1a和2a的合成过程,这些缓凝剂是通过合理方法开发的。然而,尝试将这些化合物合成磷酸酯衍生物均未成功,相反,直接修饰母体六氮杂(3)和三氧三氮杂-18-冠-6(5)衍生物获得了成功,分别得到了膦酸1b和2b。随后对这些化合物的测试表明,它们能够抑制结晶钙矾石的生长并延缓水泥的凝结。这些结果支持了如下假设:结晶钙矾石的形成是水泥凝结速率的决定步骤。