Mechanical Properties and Durability of Structural Lightweight Concrete Incorporating High Volumes of Fly Ash

Abstract

Canada Centre for Mineral and Energy Technology (CANMET) has an ongoing project dealing with the role of supplementary cementing materials in concrete. As a part of this program, a new type of concrete known as high-volume fly ash concrete has been developed. In this type of concrete, the water and cement contents are kept very low, i.e. about 115 and 155 kg/m to the third power, respectively, and the proportion of low-calcium fly ash is about 56% of the total cementitious materials. This type of concrete has excellent mechanical properties and durability characteristics. The objective of this study was to investigate the application of the high-volume fly ash system to the production of structural lightweight concrete. In this study, high-volume fly ash concrete mixtures were made using ASTM Type I portland cement, fly ashes from sources in the U.S.A. and lightweight coarse aggregates from four different producers, three from the U.S.A., and one from the U.K. A reference concrete mixture without fly ash was also made for comparison purposes. A large number of test specimens were cast to determine the mechanical properties and durability characteristics of the concrete. The test results show that the structural high-volume fly ash concrete had mechanical properties similar to those of the reference concrete. The fly ash concrete generated significantly less heat of hydration, and showed noticeably better resistance to chloride-ion penetration than the reference concrete of similar 28-day strength. All concretes investigated demonstrated an excellent resistance to the freezing and thawing cycle.