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Introduction
Compressive strength of concrete is an excellent indicator of concrete quality and it invariably forms the most important basis of specifications and quality control, as many other properties are directly or indirectly related to it. The application of ultrasonic pulse velocity (UPV) to the nondestructive evaluation of normal strength concrete (≤41 MPa) quality has been widely investigated for decades. The pulse velocity is influenced, however, by many variables in concrete, including mixture proportions, aggregate type and size, age of concrete, moisture content, and others ([16] Tanigawa et al. , 1984). UPV measurement on hardened concrete having different nominal aggregate sizes was investigated for normal strength concrete. Thus, normal strength concrete mix with nominal aggregate size 10 mm was investigated and correlations were proposed ([6] Bungey, 1982; [13] Neville, 1995).
Research on high performance concrete parameters using UPV test was found very limited, thus, UPV-strength correlations are not being articulated. Even though, several attempts were undertaken by different researchers to predict correlation between strength and UPV. Instinctively, researches on the strength-UPV correlation for strength estimation of HPC have been progressing to standardize a correlation equation. In fact, the effect of aggregate type in the mix and curing temperature on UPV-strength correlation has been studied ([8] De Almeida, 1991; [14] Price and Hynes, 1996). UPV-strength correlation has also been proposed for different mineral admixtures in HPC ([11] Giovanni et al. , 2000; [12] Hamid et al. , 2002). Most of the high performance concrete mixes are prepared with either, 10 mm or 19 mm nominal aggregate size. Therefore, a standard UPV-strength correlation equation is sought to estimate strength of HPC of such mixes. Thus, the purpose of the present study is to investigate the effect of pulse velocity measurement of hardened HPC having 10 mm and 19 mm nominal aggregate sizes and then propose a reliable correlation equation to estimate strength.
Experimental work
Material and properties
Ordinary Portland cement (OPC) ([1] BSI, 1996) and commercial densified silica fume (SF) was used as cementitious material. Physical properties and chemical composition of the cementitious material are given in Table I [Figure omitted. See Article Image.]. The coarse aggregate (CA) was crushed Sandstone with 10 mm (max) and 19 mm (max) nominal size, and was sourced from Hulu Langgat....