Title: Evaluation of In-situ Concrete Strengths for Post-Tensioning of Concrete Slabs

Author(s):

Publication: CIA

Volume:

Issue:

Appears on pages(s):

Keywords:

DOI:

Date: 2/14/2011

Abstract:
Post-tensioned concrete is commonly used for the construction of suspended slabs in buildings. This construction method has widespread use as a result of increased construction efficiency and reduced floor height. One of the continued challenges associated with this construction method is the accurate assessment of in-situ concrete strength prior to initial and final stressing of the post-tensioning strands. There are many factors that influence early age mechanical properties of concrete including compressive strength development. In order to reduce the number of variables to be considered in design, early age compressive strength is most often specified as the requirement for concrete in post-tensioned construction. Apart from the grade of concrete, the most important factor influencing early age compressive strength is the concrete temperature. Accurate assessment and adequate early age in-situ concrete strength are critical for construction efficiency and satisfactory anchorage performance. This paper presents results from research of two concrete mixes supplied to two building projects over a 16-month period covering two winter seasons in Sydney. In this investigation, real-time in-situ concrete temperatures in post-tensioned slab are simulated in a temperature matched curing tank in a laboratory.