Non-Delayed Heat Application Effects on The Strength of Concrete For Railway Sleepers
- Publication Type:
- Journal Article
- Concrete Research Letters, 2014, 5 (1), pp. 716 - 721 (6)
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Precast concrete sleepers production requires the application of low-pressure steam curing to accelerate the early age strength development. In this curing process, heat is gradually applied to the sleepers after 2 hours from casting. A typical production specification for concrete sleepers limits the rate of temperature rise to 24 o C per hour and the maximum temperature to 70 o C. However, it is not usual to consider heat application immediately after casting to achieve improved productivity to meet the supply demand. This paper reports the results of an experimental investigation into the effect of non-delayed heat application on the early age and later age compressive strength for the typical concrete mixes used for the production of concrete sleepers in Australia. The mixes had either ordinary Portland cement or high early-age strength Portland cement with the low calcium fly ash as binder materials. The results showed that the compressive strength after 8 hours and 28 days were significantly reduced when non-delayed heat application was carried out. Delayed ettringite formation (DEF) could be one of the reasons for the strength reductions and a delayed period up to 4 hours is beneficial in controlling the strength loss.
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