ABSTRACT
In this paper, the mechanical properties of alkali activated concrete (AAC) produced from three different fly ash sources were studied. Class C fly ashes (Sk, TH, and KC) were located in the State of Missouri, USA where used in this study. The three fly ashes had different chemical composition. The workability of the mixtures was assessed based on the slump value of each mixture. The mechanical properties including the compressive, splitting tensile, and flexure strengths were tested. The compressive strength was tested at different ages including 1, 7, 28 days. Elevated heat curing regime was applied on the three fly ashes in an electric oven. The temperature of the oven was constant at 70°C for 24 hours. The results revealed that the workability and the mechanical properties depended mainly on the calcium content of the fly ashes. The Sk fly ash that had lowest calcium content showed high slump value. With decreasing the calcium content in the fly ash, the mechanical properties were improved. The strength of all mechanical properties has a slightly or constant development with time. The compressive strength reached to 41.28, 39.85, and 36.43 Mpa for Sk, TH, KC that were ordered from the lowest to highest calcium content, respectively. The splitting tensile strength results showed a good match with AS 3600 code. However, the flexure strength results showed a good match with ACI 318. Proposed equations were suggested to predict the splitting tensile and flexure strengths of the AAC with R2 higher than 0.90.
