High-Strength/High-Performance Concrete with Fly Ash and Micro Silica

Concrete is the second most consumed material after water and it shapes the built environment around the world. High strength/High performance concrete (HPC) exceeds the properties and constructability of normal concrete. Normal and special materials such as fly ash, micro silica are used to make these specially designed concretes that must meet a combination of performance requirements. There are many good reasons to view fly ash as a resource, rather than a waste. Micro silica is a by-product from the production of silicon metal, which is formed when silicon dioxide vapour is condensed. In many cases, products made with coal ash/micro silica perform better than products made without them. In this study, compressive strength of concrete with fly ash and micro silica (micro SiO₂) is studied. It found that compressive strength of concrete with fly ash is equal or higher when fly ash amount is between 5~15% by weigh, and concrete strength reduces when fly ash content is increased beyond 15% by weigh. For durable concrete, 25% ~30% by weight of fly ash to be used unless micro silica is used in concrete mix. Test results obtained in this study indicate that up to10% by weight of micro silica in concrete effectively however optimum levels of micro silica is 3–8% by weight when we consider the strength of concrete. Slump and slump retention is higher when fly ash blended cement is used instead of ordinary Portland cement (OPC) in any concrete. However, workability drops when more and more micro silica is added into concrete mix.