الفهرس | Only 14 pages are availabe for public view |
Abstract Sulfates in fine aggregate are a major problem when it exists in excessive amount especially in the Middle East. Most of sulfate salts in fine aggregate are composed of calcium, magnesium, potassium and sodium sulfates. Calcium sulfates is the most common salt present in fine aggregate. It is usually finding as gypsum. It is difficult to obtain the specific sulfates content in fine aggregate within standard specifications. Most of samples of sand was refused because the finding of sulfates. This research was conducted to investigate the effect of adding different contents of gypsum to fine aggregate as a replacement by weight on some properties of two types of concrete self-compacting concrete( SCC) and high strength concrete(HSC) even accept more samples. In these work three bases mixes of each type of concrete are used: mixes with different contents of metakaolin, mixes with different contents of gypsum and mixes incorporating different contents of metakaolin and gypsum. This study is devoted to determine the allowable content of sulfates in fine aggregate. Three levels of gypsum were tested (0.5, 1, 1.5) % by weight of fine aggregate as a replacement and three levels of metakaolin were tested (5, 10, 15) % by the weight of cement as a replacement. The experimental program is devoted to produce concrete with different levels of metakaolin and gypsum and determine its mechanical properties such as compressive strength, splitting tensile strength, modulus of elasticity and flexural strength. The tests results arrived from this work show that the optimum gypsum content was 1.5% by weight of fine aggregates for mixes of SCC which gives increased in compressive strength and tensile strength, and 1.5% gypsum for mixes of HSC which increased the compressive strength and 1% gypsum which increased the splitting tensile strength . Results also showed that the mixes which contain 5% MK and 1% gypsum is the best mix for SCC, and mix of 10% MK and 0.5% gypsum is the best mix for HSC. In this study also two beams were mixed as the bests mixes of SCC and HSC and their results emphasized high ductility and energy absorption properties which are very use-ful for dynamic applications. The energy absorption of beam HSC is1.53 times that of beam SCC. There is no spalling of concrete cover of the tested beams at failure, this is predominant. The developed cracks at failure were fine crack widths resulting from employing the proper designed mix. |