Effect of Pouring Time on the Integrity of Pulverized Fuel Ash Concrete

Abstract

The effects of pouring time intervals on the integrity of pulverized fuel ash (PFA) concrete were evaluated by measuring ultrasonic pulse velocity and compressive strength. Concrete was poured progressively at different time intervals (30 min, 45 min, and 60 min) under similar conditions after the first batch of concrete was vibrated. The effects of the water–cement ratio (w/c) on ultrasonic pulse velocity were also compared and analyzed. Both compressive strength and ultrasonic pulse velocity decreased as the pouring time interval increased. When the water–cement ratio was 0.55, the pouring time interval had little effect on compressive strength, but when the w/c was reduced to 0.45, improvements in the compressive strength of concrete with different pouring time intervals were as high as 10 MPa. Under the condition of the same w/c and the same pouring time interval, improvements in the compressive strength of the interface were as high as 15 MPa, and the prolongation of the aging period could reduce the difference in strength to 8 MPa. The formula Fc=0.63e0.95Vc was used to infer the compressive strength of fly ash concrete at different ages by ultrasonic pulse velocity.