Abstract
Nonlinear ultrasonics (NLU) has grown in importance over the past years. The viability of applying the newly developed NLU technique called the Sideband Peak Count-Index (SPC-I) to estimate the 28-day unconfined compressive strength (UCS) of cylindrical concrete specimens is investigated. In addition, the SPC-I technique is combined with the conventional ultrasonic pulse velocity (UPV) technique to achieve more precise UCS estimations than would be possible with a single estimation parameter. Sixteen conventional general-purpose concrete specimens are cast utilizing water-to-cement (W/C) ratios of 0.4, 0.5, 0.55, and 0.6. To ensure the reproducibility of results, experimental operations are performed utilizing consistent testing protocols and instruments. The SPC-I is determined to be a viable parameter that can be used to estimate the UCS value of concrete specimens with high accuracy. In addition, when the SPC-I is combined with the UPV, the resulting estimates become even more accurate and reliable than when utilizing only UPV values.