Investigation of the Maturity and Engineering Performance of Self-Compacting Concrete for Pre-cast Elements

The prediction of concrete strength at an early age is very important in the concrete industry. This will help in accelerating the construction process, determining the safe time for de-tensioning of pre-stressed concrete and... [ view full abstract ]

The prediction of concrete strength at an early age is very important in the concrete industry. This will help in accelerating the construction process, determining the safe time for de-tensioning of pre-stressed concrete and for stripping of formwork or the proper time to conduct any construction activity. The maturity method is a technique to account for the combined effects of time and temperature on the strength development of concrete. The method provides a relatively simple approach for making reliable estimates of in-place strength during construction. The maturity concept has gained increasing interest as a scientific way to evaluate in-situ strength of concrete in a very accurate way. In tandem with this the use of self-compacting concrete in precast concrete has grown substantially, worldwide in recent years.
This paper reports on an investigation of the effect of water-to-binder ratio (w/b) and the percentage of ground-granulated blast furnace slag on fresh properties, the hardened properties and the maturity of mixes to be used in pre-stressed structural elements. The filling ability, flowability and passing ability of SCC mixes were measured using slump flow and J ring. The compressive strength 1d, at 7d and 28 were determined. The maturity index was measured using maturity box at Banagher precast concrete. The results of this investigation show that w/b and the replacement of cement by GGBS had a significant effect on the maturity index. As expected, the reduction of w/b from 0.45 to 0.40 led to an improvement of compressive strength and the increase in percentage of GGBS resulted in a reduction of compressive strength. The Relationship between the maturity index and compressive strength has been established for several SCC mixes used by Banagher precast for releasing the pre-stressed tendons used in precast elements.