dynamic modulus of elasticity

The behavior of concrete subjected to impact load, is different compared to the behavior under static loading. A test program was carried out to determine static and dynamic properties of rubberized concrete. In this study, waste tire rubber particles were replaced with fine aggregate in concrete mixture in 3 sizes, 0-1, 1-3 and 3-5 mm and in volume ratio of 0%, 10%, 20%, 30%, 40% and 50%. Static and dynamic tests are done with hydraulic and drop hammer machines. Results of compressive and flexural strength, velocity of ultrasonic wave, Static and dynamic modulus of elasticity, strain and Static and absorption energy of rubberized concrete are determined. The results indicated that: larger rubber particles in replacement of sand have better results than smaller sizes. Also increased in rubber content, decreased the unit weight, compressive strength and static and dynamic modulus of elasticity of rubberized concrete. Using rubber particles in concrete significantly increased the ductility and strain capacity of concrete. In addition in this study equation of impact test with using mass-spring modelling, was determined.

Measurements of the speed of passing ultrasonic waves are used to determine the quality and strength of materials. Velocity of ultrasonic waves of solids depends on the density and elasticity characteristics. The quality of material depends on the firmness and elasticity of the, so measurement of the speed of passing waves can be used to determine the quality of and elastic properties. According to the application of cement based grout to bridge the gap between the members and the concrete foundation and the ability to absorb and transmit static and dynamic loads by grout into the foundation, structural engineers need to grout with high quality, strength and durability that has a strong internal structure and with minimal pores and cavities inside. Ultrasound waves passing speed test is done to check these features and its results are presented based on dynamic modulus of elasticity. The results show that the modified grout mix with nano-silica, silica fume, and dynamic modulus of elasticity increased so that by replacing 1% nano-silica powder and 20% micro silica powder in grout combination with cement, dynamic modulus of elasticity increased to 64%.

Dynamic methods are, nowadays, fast and inexpensive ways of estimating elastic constants in rock engineering. Therefore, In order to get reliable outputs all effective factors of such methods are to be assessed. One of fundamental factor affecting the test results is the shape or height/diameter (L/D) ratio of the tested specimen. The existing standards, namely ASTM and ISRM standards imply that, in spite of the great role of the (L/D) ratio on the static test results, this ratio does not play an important role on dynamic test results. With aim of determining the exact role of (L/D) ratio on static and dynamic properties of rocks, 3 dynamic and 5 static tests were conducted on Neka Limestone samples with 6 various (L/D) ratios of 0.5, 1, 1.5, 2, 2.5 and 3 (48 sets of tests in all).The data produced through these tests showed that varying (L/D) ratio from 0.5 to 3 results in ample variation of mechanical parameters in both types of tests. The laboratory produced data indicated that static tests are affected more by (L/D) ratio than dynamic ones. It was also concluded that when the value of (L/D) gets close to 3, elastic dynamic parameters reach more or less constant values whereas static parameters are still in change. These finding show that the effect of sample shape on dynamic properties of rock has not been counted for properly. This importance of this factor has to be recognized. Also, when static tests are concerned, the previously recommended ratio of (L/D) has to be further assessed.