Khairul Anuar Mohd Nayan

A Microcontroller-Based Instrument for Measuring P-Wave Speed in Impact-Echo Testing of Concrete

The objective of this paper is to describe a microcontroller-based instrument for measuring P-wave speed in impact-echo test of concrete. This measurement is based on measuring the travel time of the P-wave (Deltat) between two transducers at known distance apart. The present study developed an instrument to record the Deltat using interrupt-on-change feature of microcontroller and calculate the P-wave speed. Laboratory studies were carried out on 20 cm concrete slab and obtained Deltat=73.51 s and CP=4082.6 m/s. The simple proposed instrument obtained an accurate result compared to the measurement using B&K general purpose data acquisition. For the practical, this instrument is an easy-operated one, light in weight and does not need another data acquisition, portable computer and software program

Effect of input source energy and measurement of flexible pavement deflection using the SASW method

Abstract This paper presents the effect of input source energy on the results of spectral analysis of surface wave (SASW) evaluation of flexible pavements in terms of maximum and minimum wavelength. A series of surface wave tests, namely the SASW test, were done on asphalt pavement using four steel balls with different masses as sources. These sources were dropped from two different heights, 0.25 and 0.50 m. This test was also conducted with two different configurations, i.e. with the receivers positioned 0.15 and 0.30 m apart. This paper also presents the feasibility of using accelerometers to measure flexible pavement deflection. For this purpose, the process of integrating accelerometer time history is described. It is proved that a change in input source energy has some effect on the value of maximum and minimum wavelength. The result for numerical double integration is satisfactory and is congruent with the displacement obtained through finite element analysis.

STUDY ON THE EFFECTS OF RECEIVER DISTANCE, HEIGHT AND MASS OF DROPPING STEEL BALLS ON SASW TEST RESULTS

A series of surface wave tests, namely the Spectral Analysis of Surface Wave (SASW) test, was done on asphalt pavement to study the effect of receiver distance, S; the height of dropping steel balls, H; and the mass of the source, m on the results of SASW evaluation. For each test, four steel balls with different masses, namely0.067kg, 0.228kg, 0.537kg, and 1.805kg, were used as sources, and the balls were dropped from varying heights, 0.25m and 0.50m. This test was conducted with two different configurations, in which the receivers were located 0.15m and 0.30m apart. This paper presents the results of the test in terms of maximum and minimum wavelength. The results proved that larger receiver distance yields large wavelength, and vice versa. The similar trend is observed when the mass of the dropping ball is increased. The height of the falling steel ball, however, did not have significant impact on the results of the SASW evaluation.

Measurements of the stiffness and thickness of the pavement asphalt layer using the enhanced resonance search method.

Enhanced resonance search (ERS) is a nondestructive testing method that has been created to evaluate the quality of a pavement by means of a special instrument called the pavement integrity scanner (PiScanner). This technique can be used to assess the thickness of the road pavement structure and the profile of shear wave velocity by using the principle of surface wave and body wave propagation. In this study, the ERS technique was used to determine the actual thickness of the asphaltic pavement surface layer, while the shear wave velocities obtained were used to determine its dynamic elastic modulus. A total of fifteen locations were identified and the results were then compared with the specifications of the Malaysian PWD, MDD UKM, and IKRAM. It was found that the value of the elastic modulus of materials is between 3929 MPa and 17726 MPa. A comparison of the average thickness of the samples with the design thickness of MDD UKM showed a difference of 20 to 60%. Thickness of the asphalt surface layer followed the specifications of Malaysian PWD and MDD UKM, while some of the values of stiffness obtained are higher than the standard.