This research presents a comparative study to highlight the differences between the effect of using various contents of steel fibers on the ultrasonic pulse velocity (UPV) in two types of self-compacting concretes (SCC) which are identical in their constituent materials, the only difference between them is the coarse aggregate type (normal in one and light in the other) with various specimen lengths (200mm cylinders and 100mm cubes). In this work, six types of mixes were casted, the first three (Mix1, Mix2 and Mix3) are of normal-weight SCC having steel fiber content (Vf) : 0.0%, 0.4% and 0.8% respectively, and the other three (Mix4, Mix5 and Mix6) are of light-weight SCC with the same aforementioned steel fiber contents respectively. It turns out that, the ultrasonic pulse velocity is smaller in light-weight SCC than in normal-weight SCC, and the percentage of this reduction is higher in cylindrical samples than in cubic samples, and this percentage of reduction is reduced with the increasing in steel fiber contents. It also turns out that, the ultrasonic pulse velocity is increased with the increase in steel fiber contents, and this percentage of increase is higher in light-weight SCC than in normal-weight SCC, and it is also larger in cylindrical samples than in cubic samples. Moreover, when the specimen length has been focused on, it was found that, the ultrasonic pulse velocity is larger in (100mm) cubic specimens than in (100×200mm) cylindrical ones, and the percentage of this rise is also larger in light-weight SCC than in normal-weight SCC, and it is reduced with increasing steel fibers contents.

This work presents an investigative study of the influence of adding chopped carbon fiber (C.C.F.) on the performance of two specified properties of cement mortar, namely; The flexural strength and density, for two (W/C) ratios (0.4 & 0.6). Four cement mortar mixtures were casted for this purpose, these mixtures were divided into two groups according to their (W/C) ratios (0.4 & 0.6), and each group was subdivided into two subgroups according to whether C.C.F. is used or not. It was found that, when C.C.F. is added, the flexural strength and density of the cement mortar mass are increased for both (W/C) ratios, and the percentages of these increases are slightly increased with the increase in (W/C) ratios. It was also found that, when (W/C) ratio is enlarged from (0.4) to (0.6), the flexural strength and density are reduced with and without the existence of C.C.F., and the percentage of this reduction is slightly decreased in the existence of C.C.F.

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