Title: Methods for determining the in-situ compressive strength of precast hollowcore slabs

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Publication: CIA

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Date: 2/28/2011

Abstract:
The daily monitoring of concrete strength used in the manufacture of zero-slump precast pre-tensioned Hollowcore Floor Planks (HCFP) is essential in identifying the intermediate and characteristic strength developments. The implementation of non-destructive tests at a precast plant which determines the time at which the prestressing forces in the tendons can be transferred onto the bed of a HCFP was the motivation of this study. In addition, a rigorous investigation was initiated to identify a suitable relationship between actual and potential concrete strength using small drilled inplace cores with companion standard cube test samples. The results of both studies will allow designers to better evaluate intermediate and characteristic strengths of hollowcore floor panels. A calibration chart was developed which relates material compressive strengths to the rebound value. The implementation of combined non destructive testing systems will provide and validate real-time information on the progress of early-age concrete strength. By utilising a non-destructive test known as the Maturity Method along with the calibrated rebound hammer, the tests will authenticate estimated readings and will develop greater understanding of the material behaviour. Experimental results revealed that the equivalent-age maturity function is appropriate for modelling the strength growth of Hollowcore concrete