Title: Properties of High-Volume Fly Ash Concrete Made with High Early-Strength ASTM Type III Cement
Author(s): A. Bilodeau and V. M. MalhotraI
Publication: Symposium Paper
Appears on pages(s): 1-24
Keywords: chlorides; compressive strength; drying shrinkage; fly ash; flexural strength; freeze thaw durability; high-early-strength cements; modulus of elasticity; splitting tensile strength; superplasticizers; Materials Research
Canada Centre for Mineral and Energy Technology (CANMET) has an ongoing project dealing with the role of supplementary cementing materials in concrete technology. 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 (ASTM Type I) contents are kept very low, about 115 and 155 g/m 3, respectively, and the proportion of low-calcium fly ash in the total cementitious materials content is about 56 percent. This type of concrete has excellent mechanical properties and durability characteristics. In spite of very good properties shown by the high-volume fly ash concrete, one concern about the use of this type of concrete is its performance at early ages due to its low cement content and the slow reaction process of fly ash. This can be an obstacle for the use of this type of concrete when compressive strengths over 10 MPa at one day are needed or when proper curing cannot be provided for a long period of time. One way to improve the early-age properties of this type of concrete is to use ASTM Type III portland cement. Therefore, a study was undertaken to develop engineering data base on the high- volume fly ash concrete using ASTM Type III cement. Concrete mixtures were made using ASTM Type III portland cement from a source in the U. S. A. and three low-calcium fly ashes also from source in the U. S. A. A reference mixture (without fly ash) was also made for comparison purposes. The use of ASTM Type III cement instead of Type I cement noticeably improved the early-age strength properties of the high-volume fly ash concrete incorporating the fly ashes investigated in this study; this was done without having any detrimental effect on long-term properties of the concrete. The one- day compressive strengths were about 5 to 8 MPa higher than those of the high- volume fly ash concrete made with the same fly ash and Type I cement. The use of Type III cement also shortened slightly the setting time of the high-volume fly ash concrete. Durability characteristics and drying shrinkage of high- volume fly ash concrete made with ASTM Type III cement were no different than those for the concrete made with Type I cement.