Table 2: Rebound curve for concrete strength measurement and error.

Regress modelFunction expressionCorrelative coefficientMean relative error (%)Relative standard error (%)

Exponential function 0.82412.4315.33
Exponential function 0.85011.8814.7
Logarithm function 0.86811.2116.88
Power function 0.85011.1714.05
Power exponential function 0.82412.4315.33
Complex-exponential function 0.85211.0413.75