Utilizing Aggregates Characteristics to Minimize Cement Content in Portland Cement Concrete
Aggregate, the main constituent of concrete, constitutes 60 to 80% of the total volume of concrete. Proper selection of the type and particle size distribution of the aggregates affects the workability and the hardened properties of the concrete. There are two main reasons for increasing the amount of aggregates in concrete. The first is that cement is more expensive than aggregate, so using more aggregate reduces the cost of producing concrete. The second is that most of the durability problems, e.g. shrinkage and freezing and thawing or hardened concrete, are caused by cement. Generally, concrete shrinkage increases with increase in cement content; aggregates, on the other hand, reduce shrinkage and provide more volume stability. Furthermore, cement production is a key source of carbon dioxide (CO2) emissions, and reducing its usage should be a goal for concrete production. Various projects have explored methods of minimizing cement in concrete; among the most common of those is replacing cement with cementitious and pozzolanic materials such as fly ash.