Durability of concrete containing high-calcium fly ash

拟议的研究计划的目的是解决有关某些混凝土含有某些类型的C类粉煤灰的性能差的问题。粉煤灰是发电站燃烧煤炭的工业副产品。该材料已被用作混凝土中的胶结材料，部分取代传统的波特兰水泥，在加拿大已有数十年的历史。它的使用产生了许多技术、经济和环境效益。然而，加拿大生产的粉煤灰有不同类型，其成分差异很大。最近，人们对使用含有相对大量的碱或硫酸盐或两者的粉煤灰表示关注，因为这些化合物可能对混凝土的性能有害。还有人担心最近的趋势，即用粉煤灰取代更大比例的传统水泥，因为这可能导致早期性能差，特别是在典型住宅应用中使用的低强度混凝土中。本研究计划将测试粉煤灰化学对水泥、砂浆和混凝土产品的组成和性能的影响。目的是确定是否需要对粉煤灰进行更严格的化学限制，以及是否需要根据混凝土质量或应用限制某些粉煤灰的使用。发展更好地了解粉煤灰组合物在混凝土性能中的作用，将导致粉煤灰在水泥基产品中的使用增加。每年有超过400万吨的飞灰被送往垃圾填埋场，增加使用这种材料将减少环境废弃物。另一个环境效益是，增加使用粉煤灰将减少波特兰水泥的消耗，而波特兰水泥的生产是建筑业温室气体的主要产生者。

The proposed research program is aimed at addressing concerns regarding the poor performance of some concrete containing certain types of Class C fly ash. Fly ash is an industrial by-product of burning coal in electricity generating stations. The material has been used as a cementing material in concrete, partially replacing traditional portland cement, for a number of decades in Canada. Its use results in many technical, economic and environmental benefits. However, there are different types of fly ash produced in Canada, which vary widely in composition. Recently there has been concern expressed over the use of fly ashes with relatively high quantities of alkali or sulfate, or both, as these compounds can be injurious to the performance of concrete. There are also concerns over the recent trend to replace larger proportions of traditional cement with fly ash as this may result in poor performance at early age, especially in low strength concretes used in typical residential applications. The impact of fly ash chemistry on the composition and performance of cement, mortar and concrete products will be tested in this research program. The aim is to establish whether more stringent chemical limits are necessary for fly ash and whether the use of certain fly ashes needs to be restricted on the basis of concrete quality or application. Developing a better understanding of the role of fly ash composition in concrete performance should lead to an increased use of fly ash in cement-based products. More than 4 Mt per annum of fly ash are sent to landfills each year and increased use of this material will reduce environmental dereliction. A further environmental benefit is that the increased use of fly ash will result in a reduced consumption of portland cement, the manufacture of which is the chief producer of greenhouse gases in the construction industry.