Sandless concrete with fly ash as supplementary cementing material

As a step towards an environmental friendly and sustainable construction, the properties of concrete made without natural sand (termed sandless concrete herein) and with cement partially replaced with fly ash were investigated. First, the appropriate mixture proportion to ensure the desired properties in sandless concrete for structural applications was established. The effects of coarse aggregate grading, aggregate cement (A/C) ratio, and water-cement (w/c) ratio on compressive strength were investigated. It was shown that compressive strengths of 30-50 MPa could be readily achieved with w/c ratios less than 0.5 and A/C ratios less than 3. Next, the effect of cement replacement by Class-F fly ash by up to 50% on the fresh and hardened properties of sandless concrete was investigated. The incorporation of fly ash improved workability and resulted in higher long-term strength, reduced drying shrinkage, and higher resistance to chloride ingress .