Structural behavior of alkali activated fly ash concrete. Part 1: mixture design, material properties and sample fabrication

Abstract

Alkali Activated Fly Ash Concrete (AAFAC) is an alternative form of concrete that uses fly ash as a 100 % replacement for ordinary portland cement. In producing AAFAC, fly ash is combined with alkali activators that chemically react to form a binder. When combined further with fine and coarse aggregates and often cured at elevated temperature, a concrete material is produced with strength and stiffness properties similar to ordinary portland cement concrete (OPCC). In this paper fabrication of full scale steel reinforced AAFAC beams is presented. The research scope includes: development of an AAFAC mixture design, fabrication of nine AAFAC beam samples, development of an elevated temperature curing system, temperature measurement during curing, and investigation of hardened AAFAC material properties. Results show AAFAC can be manufactured in the same way as OPCC, and that it has a self consolidating consistency in the fresh state. Curing at 60 °C for 24 h produced very rapid strength gain. Compression strengths at 1 day ranged between 47 and 53 MPa, with 28 days compression strengths ranging from 48 to 55 MPa. Material test results show AAFAC is a brittle material with an approximately linear stress–strain response, and an elastic modulus slightly less than that predicted by ACI 318.