Effect of Mix Constituents and Curing Conditions on Compressive Strength of Sustainable Self-Consolidating Concrete

The production of cement requires significant energy and is responsible for more than 5% of global CO2 emissions; therefore it is imperative to reduce the production and use of ordinary portland cement (OPC). This paper examines the compressive strength development of low water-to-binder (w/b) ratio self-consolidating concrete (SCC) in which 90% of the cement is replaced with industrial by-products including ground granulated blast furnace slag (GGBS), fly ash, and silica fume. The emphasis in this paper is on replacing a large volume of cement with GGBS, which represented 10% to 77.5% of the cement replaced. Fresh properties at w/b ratio of 0.27 were examined by estimating the visual stability index (VSI) and t50 time. The compressive strength was determined after 3, 7, 28, and 56 days of curing. The control mix made with 100% OPC developed compressive strength ranging from 55 MPa after three days of curing to 76.75 MPa after 56 days of curing. On average, sustainable SCC containing 10% OPC developed strength ranging from 31 MPa after three days of curing to 56.4 MPa after 56 days of curing. However, the relative percentages of fly ash, silica fume, and GGBS in the 90% binder affect the strength developed as well. In addition, this paper reports the effect of the curing method on the 28 day compressive strength of environmentally friendly SCC in which 90% of the cement is replaced by GGBS, silica fume, and fly ash. The highest compressive strength was achieved in samples that were cured for three days under water, then left to air-dry for 25 days, compared to samples cured using chemical compounds or samples continuously cured under water for 28 days. The study confirms that SCC with 10% OPC and 90% supplementary cementitious composites (GGBS, silica fume, fly ash) can achieve compressive strength sufficient for many practical applications by incorporating high amounts of GGBS. In addition, air-curing of samples in a relatively high temperature (after three days of water curing) produce a higher 28 day compressive strength compared to water curing for 28 days, or membrane curing.