Table 21: Average density (t/m3) of hardened and fresh concrete at 115 and 28 days87
Table 22: Water absorption after immersion (%) and after immersion and boiling (%) at 115 days88
Table 23: Average compressive strength (MPa) at various periods (115, 7, and 28 days)88
Table 24: Average tensile splitting strength (MPa) for the different ages of tests (115, 7, and 28 days)88
Table 26: Average compressive strength (MPa) at 115 days at various speeds89
CHAPTER 1: INTRODUCTION
Background of the Study
Aggregates make up three quarter of the concrete volume, and they not only have effect on the concrete resistance, but also an effect on the domination and stability of that mixture. The stone materials in concrete withstand and transfer the loads of bars (with coarse particles) and by filling the empty spaces (with fine particles) between the other components of concrete. As it is pointed out the stone materials in the concrete are divided into coarse particles and fine particles, first section is granular materials with medium diameter bigger than 5 millimetres and the second section is smaller than 5 millimetres.
From the petrology point of view, aggregates divided into several groups, which have approximately similar properties. Clarification of natural aggregates are based on British standards including of Granit group, Lime group, slate clay group, sandstone group, Porphyry group, Gabbro Group and Quartz group. American concrete institute is also offering clarification for these minerals, which are, contain ...