Mechanical and durability properties of self-compacting concrete made with fly ash microbeads and phosphorous slag powder

The self-compacting concrete with two kinds of pozzolanic admixtures of fly ash microbeads (FB) and phosphorus slag powder (PS) was studied in this work. The mechanical properties and durability of self-compacting concrete with different admixtures were investigated and the results indicated that the concrete workability is best when FB and PS were 15%, respectively. While early mechanical properties were not as good as the control samples, but long-term strength exceeded the control from extending over curing time. Chloride ion permeation test proved that the sample of self-compacting concrete with 15% FB had the lowest electrical flux for the value for 1690 Coulombs and the minimum diffusion coefficient for 5.30 × 10−8 m2/s. The effect of improvement to PS on mechanical properties and electric flux was not as good as that of FB. Meanwhile, XRD, TGA-DTG, and SEM tests were performed on the samples for curing 7 days and 28 days. XRD test showed a 28-day peak of Calcium Hydroxide has a dramatic drop for CFB-15%. TGA-DTG test showed that the 28-day hydration degree of CFB-15% was 64.08%, which was much higher than that of the control group and CPS-15%. SEM test proved the spectacular filling property and pozzolanic effect of FB varied the interfacial adhesion of the cement particles. Mercury intrusion experiments indicated the amount of internal pore decreased with the addition of FB and PF.