Assessment of suitability of existing mix design methods of normal concrete for designing high performance concrete mixes

The prime objective of proportioning a concrete mix is to obtain relative quantities of ingredients for the most economical mix that meets the minimum criteria of strength, workability, durability, aggregate characteristics and economy. A number of standard mix proportioning methods are available for conventional normal strength concrete (NSC). Concrete with a compressive strength less than 50 MPa is regarded as normal strength concrete (NSC). Mix proportioning of high performance concrete (HPC) is a more critical process than that of NSC in view of higher powder content and requirement of low waterbinder ratio. Existing mix design methods of NSC such as Bureau of Indian Standards (BIS), Department of Environment (DOE), American Concrete Institute (ACI) are not directly applicable for designing HPC mixes due to several reasons, primarily due to the presence of mineral admixtures. It is felt that the mix design procedures for HPC can be based on these available methods but with suitable modifications. Therefore, this paper examines the suitability of these methods of mix design through experimental procedures on mixes containing mineral admixtures like micro-silica and fly ash. The results indicate that some of these methods can be applied for making HPC mixes with certain modifications in the proportions of aggregates and also in dosages of specific types of superplasticizer for achieving desired workability and strength properties.