Abstract
Fine aggregates used in ready-mixed concrete industry in Riyadh (the capital city of Saudi Arabia) are mainly blended of natural silica sand and manufactured sand obtained from crushed limestone. Fine materials (clay, silt, or dust content) are one of the most important defects of aggregate in Riyadh, particularly in crushed sand. In ready-mixed concrete plants (RMC) and independent laboratories in Riyadh, the practice of determining the amounts of fine materials in fine aggregates is either by ASTM C 117 (materials finer than No. 200 sieve by washing) or ASTM D 2419 (sand equivalent test) and sometimes both.
In this paper, the relationship between the sand equivalent and materials finer than No. 200 sieve tests was investigated. A total of 100 samples of natural silica sand and 100 samples of crushed sand were collected from the stock-piles of different ready mixed-concrete plants in Riyadh. Also, the effects of silica and crushed sands (using different values of sand equivalent and passing No. 200 sieve) on water demands of mortar were investigated.
A strong correlation was found between the sand equivalent and fine materials passing No. 200 for silica sand, whereas there was no correlation for the crushed sand. This indicates that the amount of fine materials in silica sand can be determined by either passing No. 200 sieve or sand equivalent test. However, the sand equivalent test can be misleading in crushed sand. For the same workability, the results indicated that there was a direct relation between water demand and the amount of materials passing No. 200 sieve for both silica and crushed sands. However, there was a good correlation between water demand and sand equivalent for only silica sand.
