Required usage of supplementary cementitious materials in concrete

Abstract

Alkali-Silica Reaction (ASR) has resulted in hundreds of millions of dollars of replacement costs in airfield concrete pavements alone, and prompted research into the development of prevention measures. In particular, the use of Supplementary Cementitious Materials (SCMs) as cement replacement in concrete has proven effective. These SCMs are often recycled materials, reducing upfront costs and resulting in reduced carbon dioxide emissions, in addition to enhanced concrete durability (and reduced maintenance costs). Specifications using complex decision trees have been developed to establish the need for SCM usage. A simpler approach consists of simply prescribing minimum amounts of cement replacement with the chosen SCM. If the aggregates show no significant ASR potential, a minimum replacement amount is still chosen to insure low concrete permeability and high durability, recycling of SCMs, and to provide a safety margin against ASR in case the aggregates reactivity varies. If the aggregates are reactive, these minimum values are increased to insure that ASR is prevented. These concepts are being extended to all unified facilities criteria and guide specifications dealing with concrete. This paper summarizes the current specifications and their development.