A comparison of the properties of OPC, PFA and ggbs concretes in reinforced concrete tank walls of slender section

Abstract

This Paper compares the properties of cores taken from the walls (250 mm thick) of a 2·5 year old reinforced concrete tank constructed using ordinary Portland cement (OPC), pulverized fuel ash (PFA) and ground granulated blastfurnace slag (gghs) concretes of equal strength grade. Measurements taken during and shortly after construction showed the PFA and ggbs to be beneficial in terms of reducing hydration temperatures and the amount of secondary steel required to control thermal and shrinkage cracking. Ultrasonic pulse velocity measurements carried out on the tank walls before coring showed no significant difference between the three concretes, and laboratory tests on cores showed them to have comparable compressive and tensile strengths. The PFA and ggbs concretes showed greater carbonation depths than the OPC concrete, although the PFA concrete was significantly less permeable to both gas and liquid. These results are discussed with reference to pore structure measurements, which show the PFA concrete to have a coarser pore structure than the OPC concrete close to the surface—at depth the situation is reversed. Generally, the results show the three concretes to have very similar properties, suggesting that the early-age benefits observed for concretes containing PFA and ggbs can be achieved in slender concrete elements without compromising strength and durability requirements.