Effect of Limestone and Inorganic Processing Additions to Cement on the Strength and Durability of Concrete

The Illinois Department of Transportation (IDOT) is making several changes to concrete mix designs, using revisions to cement specification ASTM C150 / AASHTO M85 and ASTM C465 / AASHTO M327. These proposed revisions will enable the use of more sustainable materials for concrete pavements, overlays, and bridge decks. Accordingly, a study was conducted by the University of Illinois at Chicago (UIC) to test the performance of concrete mixes batched with cement comprising less (conventional) and more (modified) than 5% by weight of limestone and inorganic processing additions (IPA) specified in ASTM C465 / AASHTO M327, and/or insoluble residue (IR) with quantity above the specified limit by ASTM C150. Twenty-eight concrete mixes with different cementitious combinations and aggregates were developed for this study. The study included evaluating the fresh properties, strength characteristics, and durability performance of concrete. The strength results were measured in terms of compressive and flexural strength, and the durability results were evaluated in terms of hardened air parameters, freeze/thaw performance, rapid chloride penetration resistance (Coulombs), water penetration (DIN 1048), chloride ion concentration, and diffusion. The study found similar performance in terms of strength and durability of concrete between the conventional and modified cements and demonstrated their performance with SCMs replacements and fine aggregate types. On the basis of the experimental results, a comprehensive program was developed to study the factors influencing the freeze/thaw performance of concrete. A simplified analytical approach to predict the water penetration coefficient in concrete based on the water penetration test results, and the equivalent-steady state diffusion coefficient through the use of rapid chloride penetration test was established. In addition, a mathematical model was developed for service life prediction of concrete structures through the diffusivity of chloride, by taking into account time dependent surface chloride concentration and diffusion coefficient.