Pengukuran Speed dan Impedansi Akustik pada Tanah Liat dengan Memanfaatkan Sinyal Echo Ultrasonik

Each material has its own characteristics, which are represented by the value of speed/ultrasonic wave propagation speed (C) and acoustic impedance/material resistance (Ztl). One technique that can be used to obtain these characteristics is by applying ultrasonic testing. This technique utilizes two ultrasonic sensors as transmitter (UST) and receiver (USR) to get signal properties from each material. The measurement mechanism is nondestructive testing (NDT) where the material tested is not damaged so it does not change the character of the sample. In this research, material characteristics are represented by reflected signals from material (echo). To process the echo signal data and get the characteristics of the sample, we need a number of data processing algorithms such as Fast Fourier Transform (FFT), Peak Detection, and Grid Search. By processing echo from reflected signals, C and Ztl values can be obtained. From the experimental results obtained, the values of C and Ztl in sample 1 with a density of 1856.97573 g/m3 are C = 636 m/s and Ztl = 474640 Ns/m3, samples 2 with a density of 1792.94208 g/m3 of C = 491 m/s and Ztl = 408080 Ns/m3, while the sample 3 with a density of 1663.85025 g/m3 is C = 434 m/s and Ztl = 405639 Ns/m3. The value of material characterization shown that a dense clay also has higher C and Ztl

Prediction of the Compressive Strength and Dynamic Modulus of Fiber Reinforced Concrete by Ultrasonic Pulse Velocity Measurement at Early Ages

This research investigates the relationship between early age ultrasonic pulse velocity and the compressive strength and dynamic modulus of steel, polypropylene, nylon, and glass fiber reinforced concrete. Previous studies prove that adding fibers to concrete alters the propagation of ultrasonic pulse velocity waves. Therefore, each type of fiber-reinforced concrete will have a unique relationship between ultrasonic pulse velocity and its compressive strength and dynamic modulus depending on fiber type, fiber volume fraction, water to cement ratio, and test age. To test this hypothesis, an experimental program comprising of one hundred eighty-nine 100 mm x 200 mm fiber reinforced concrete cylinders with varying fiber types, fiber volume fractions, and water-to-cement ratios will be tested using destructive and nondestructive test methods at the ages of 1, 3, 7, and 28 days. This research develops simple mathematical equations capable of predicting the compressive strength and dynamic modulus of different types of fiber-reinforced concrete based on early age ultrasonic pulse velocity. The equations for the prediction of the early age compressive strength of FRC had a coefficient of variation ranging from 6.4% to 14.6%. The equations for the prediction of the early age dynamic modulus of FRC had a coefficient of variation ranging from 3.3% to 9.2%. These equations can predict the compressive strength and dynamic modulus of multiple types of fiber reinforced concrete due to the incorporation of different fiber properties as variables in the equations

Evaluation of Early-Age Concrete Compressive Strength with Ultrasonic Sensors

Surface wave velocity measurement of concrete using ultrasonic sensors requires testing on only one side of a member. Thus, it is applicable to concrete cast inside a form and is often used to detect flaws and evaluate the compressive strength of hardened concrete. Predicting the in situ concrete strength at a very early stage inside the form helps with determining the appropriate form removal time and reducing construction time and costs. In this paper, the feasibility of using surface wave velocities to predict the strength of in situ concrete inside the form at a very early stage was evaluated. Ultrasonic sensors were used to measure a series of surface waves for concrete inside a form in the first 24 h after placement. A continuous wavelet transform was used to compute the travel time of the propagating surface waves. The cylindrical compressive strength and penetration resistance tests were also performed during the test period. Four mixtures and five curing temperatures were used for the specimens. The surface wave velocity was confirmed to be applicable to estimating the concrete strength at a very early age in wall-like elements. An empirical formula is proposed for evaluating the early-age compressive strength of concrete considering the 95% prediction intervals