Guide Specification for HPC Bridge Elements

Abstract

This paper describes how, in order to assist specifiers in selecting important criteria for HPC in bridges, the Portland Cement Association, in conjunction with the concrete industry, has developed a Guide Specification for High Performance Concrete for Bridge Elements. This document provides mandatory language that the specifier can cut and paste into project specifications. It also includes guidance on the characteristics to be specified in a given case and the performance limits needed to ensure satisfactory performance for a given element or environment. In cases where two performance criteria are in conflict, the commentary advises the user how to balance these conflicting requirements. Using the guide, specifiers should be able to select all criteria necessary for their structures, and then, using the commentary apply appropriate performance limits for each element. Specifiers are often tempted to select the highest grade for every parameter with the intention of achieving "high performance concrete." This practice is undesirable and, in some cases, produces mutually incompatible requirements and can lead to unnecessarily excessive costs. For instance, low permeability is normally achieved by using a high cementitious materials content and low water-cementitious materials ratio. This, however, will increase the modulus of elasticity and heat of hydration and thus increase the risk of thermally induced cracking. It is, therefore, not advisable to specify extremely low permeability for concrete in a massive element that is not exposed to an aggressive environment.