PSI - Issue 73

Sushant Chaudhary et al. / Procedia Structural Integrity 73 (2025) 19–26 Pratanu Ghosh / Structural Integrity Procedia 00 (2025) 000–000

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10 20 The multi-channel maturity meter comprises a thermocouple wire sensor, a data logger, and software. One end of the thermocouple wire was inserted into the concrete cylinder while the other was connected to the maturity meter. The recorded data at 0.5 hours was then transferred to the computer using the data logger and the software. On the other hand, the SmartRock consists of a small cable with the probe connected to the sensor body, as shown in Figure 1. The sensor probe was inserted into the concrete cylinder in the laboratory, and the data recorded at 0.5 hours was transferred to the computer via the SmartRock mobile app. 3.2. Methods 3.2.1. Maturity Functions Two empirical equations are used to calculate the maturity of the concrete, whose temperature history has been recorded up to the time of the test. ASTM 1074 recommends the following two maturity functions for the maturity index calculations: 3.2.1.1. Nurse-Saul Maturity (NSM) Function It is used to calculate the Time-Temperature Factor (TTF) of the concrete and is given by: ( ) = ∑ ( − 0 ). ∆ (1) Where, M = the maturity index (°C·hrs or °C·days), T a = the average concrete temperature during the time interval ∆ , T 0 = the datum temperature (typically 0°C or -10°C), ∆ = the time interval 3.2.1.2. Arrhenius Equation It is used to calculate the equivalent age at a specified temperature and is given by: = ∑ − � 1 − 1 0 � . ∆ (2) Where, = the equivalent age at the reference temperature (hours or days), Q = the activation energy (J/mol), R = the universal gas constant (8.314 J/mol·K), T 0 = the reference temperature (typically 23°C or 293K), T a = the average concrete temperature during the time interval ∆ , ∆ = the time interval 3.2.2. Calculation of datum temperature and activation energy Calculation of the maturity values mentioned in equations (1) and (2) first requires the determination of parameters- datum temperature (T 0 ) and activation energy (Q). Carrino [1991] has listed different equations- Linear Hyperbolic, Parabolic Hyperbolic, and Exponential, that can be employed to determine these parameters. These equations, however, require establishing the relationship between age and strength for mortar specimens cured in water baths maintained at three different temperatures, and performing least-squares curve fitting to determine the parameters. For the research, since concrete specimens were cured at only room temperature, these parameters were calculated using “Solver” in Excel to best fit the strength-maturity relationship for the zeolite-based concrete. 3.2.3. Strength Estimation Many researchers have proposed many strength-maturity relationship functions to better predict the compressive strength of concrete over time. The following are the most widely accepted functions according to Carino [1991]: 60 TII-V/ 20 Z/ 20 P -