High performance concrete (HPC) has been used more widely in recent years due to the increasing demand for durable concrete in an attempt to extend the service life and reduce maintenance costs of concrete structures. To identify the type of problems related to production of HPC encountered in the field, the National Ready-Mixed Concrete Association (NRMCA) conducted a survey of ready-mixed concrete producers. The National Institute of Standards and Technology (NIST) assisted in the analysis of the responses and in conducting a literature review. In this article, the results obtained from the survey and the findings from the literature review are presented. Recommendations are drawn from the results. Research needs are also presented.
The definition of HPC is not standardized, nevertheless a commonly used definition is given by Zia: "A concrete that meets special performance and uniformity requirements that can not always be obtained using conventional ingredients, normal mixing procedures, and typical curing practices" [1].
The definition we used in the survey was relative to a job specification and was based on one suggested by the Federal Highway Administration (FHWA) [2]. This concrete specification requires one or more of the following: a minimum compressive strength of 41 MPa (6000 psi), a water/cement ratio (w/c) less than 0.40 and chloride ion permeability less than 3000 Coulombs as measured by ASTM C 1202 [2,3]. These specifications can only be achieved by closely monitoring the properties and uniformity of concrete ingredients and the production process. The critical stages of using HPC are: flowing, transporting, placing, finishing and curing.