The research that was conducted for this thesis attacked the lack of information on early tensile strength of concrete. This was achieved by obtaining tensile stress-stain curves of fresh concrete. The concrete ages ranged within the 4 to 8 hour period and results were found for two 32 MPa concrete mixes with differing water/cement ratios. These w/c ratios were characterised by different slumps, which were 25 and 80mm.
This research provided comparisons between strength and time, and strength and water/cement ratios. The results show that the tensile strength gain is a two staged process. Firstly, there is a dormant stage, which occurs within the first 4 hours. During this period the tensile strength remains extremely low and it is at this time that cracking is likely to initiate. In the second stage a far more rapid growth of strength is experienced.
This information is important for the understanding of early age cracking in concrete. An understanding in this area would help quantify and optimize saw cutting and formwork removal times with the intent to minimise cracking. As it is these early cracks that manifest into serious problems.