aggregates, compared to sand. The unit weight of concrete is reduced by replacing natural fine aggregate with glass (Topcu and Canbaz, 2004). The dry density of concrete mix with 40% glass replacement level was 4,5% lighter than concrete with sand used and the dry density of the same mix was 2.4% lower than the control mix (Adaway and Wang ,2015
1. Waste Glass Aggregates reactions with concrete
Depending on the size of the glass particles used in concrete, two different behaviours can be observed, first, alkali silica reaction, which involves negative effects, and second pozzolanic reaction, improving the properties of concrete. Pozzolanicity of glass powder (GP) was first studied in 1973 (Reindl, 2003), but a major progress has been achieved in the last 10 years. Published research work has shown that glass powder could react in a pozzolanic manner in the cementitious systems and contribute to the strength development of concrete (Reindl, 2003, Shi and Zheng, 2007).
1.3. Properties of Glass Aggregates in Concrete
Workability of FWGAC
The slump demonstrates a decreasing trend in response to the addition of waste glass (Adaway and Wang, 2015). In higher mix proportions, the addition of waste glass as aggregates was found to negatively affect the properties of fresh concrete, resulting in severe segregation and bleeding of the mix (Taha and Nounu, 2009).Using a high proportion of waste glass aggregates was observed to decrease slump value as much as 20% due to the fact that waste glass aggregates has a poor geometry (Ismail and Hashmi, 2009). The addition of waste glass to the concrete mix has been found to decrease concrete slump, yet workability was still deemed sufficient adequate without, need for any admixtures at for replacement levels up to 50% (Taha and Nounu, 2008).
Compressive Strength of FWGAC
Compressive strength is one of the properties of concrete which gives the idea about the characteristics of compressive stress under the gradually applied load which a given concrete specimen can sustain the load without fracture. It was observed that the percentage increases in compressive strength with age, overall increased with the optimum increment of glass aggregate replacements. This may be the cause of the Pozzolanic reaction that appears to offset this trend at a later stage of hardening and such contributes to an improvement in the compressive strength at 28 days(Abdallah & Fan, 2014). A similar remarks was stated by (Metwally, 2007). Use of high dosage glass aggregate will decrease compressive strength and it is due to the high brittleness of glass leading to cracks which result in imperfect adhesion between the waste glass aggregates and cement paste, while the poor geometry and reduced specific gravity of glass leads to assorted distribution of aggregates (Topcu and Canbaz 2004).