Design of low-cost and low-CO2 air-entrained fly ash-blended concrete considering carbonation and frost durability

Abstract

Fly ash is increasingly used for producing sustainable concrete. This paper outlines a procedure for the optimal mixture design of air-entrained fly ash-blended concrete considering carbonation and frost durability. First, the aim function of the optimization is set as the total cost, which equals the material cost plus the CO2 emission cost. Constraints such as mechanical, workability, carbonation, and frost durability properties are considered during the optimization design procedure. The carbonation model considers the effect of global warming, including increasing CO2 concentration and environmental temperature. Second, a genetic algorithm is used for determining the optimal concrete mixtures. A total of 12 design examples are prepared for various frost exposure conditions (including mild, moderate, and severe exposure), and the effects of the carbonation durability and climate change on the mixture design are highlighted. According to the results, 1) for ordinary-strength concrete (design strength of 30 MPa), the carbonation durability is the decisive factor in the mixture design, and the actual strength should be greater than the design strength; 2) for high-strength concrete (design strength of 45 MPa), strength is the decisive factor in the mixture design, and the actual strength can equal the design strength; 3) for a particular entrained air content, the total cost of concrete increases with increasing concrete strength. In summary, the proposed method is a general and useful approach for designing air-entrained fly ash-blended concrete considering sustainability and durability.