Optimizing concrete mixtures with minimum cement content for performance and sustainability

Abstract

The main purpose of this research is to investigate the minimum cement content required with an appropriate water-to-cement ratio (w/c) to meet given workability, strength, and durability requirements in a concrete pavement; and so as to reduce carbon dioxide emissions, energy consumption, and costs. An experimental program was conducted to test 16 concrete mixtures with w/c ranging between 0.35, 0.40, 0.45 and 0.50; and cement content ranging from 400, 500, 600 and 700 lb/yd 3 (pcy). The fine aggregate-to-total aggregate ratio was fixed as 0.42 and the void content of combined aggregates was maintained the same for all the mixtures. Slump; setting time; 1, 3 and 28-day compressive strength; 28-day chloride penetration; and 1, 3, and 28day air permeability were determined. The test results showed that strength is a function of w/c and independent of cement content after the required cement content is reached, for a given w/c. Workability is a function of w/c and cement content: increasing w/c or cement content improves workability. Setting time is reduced when cement content is increased for a given w/c. Chloride penetration increases as w/c or cement content increases, when one parameter is fixed. Air permeability increases as cement content increases, for a given w/c. Based on these findings, it is possible to reduce the paste content without sacrificing the desired workability, strength and durability, for a given w/c. When the overall effect of cement content on concrete properties is evaluated, 400 pcy of cement content is not recommended due to its high porosity caused by its low paste content. Furthermore, 700 pcy would also not be appropriate as increasing cement content does not improve the strength, after the required content is reached; and may decrease durability as high cement content both increases air permeability and chloride penetration. Moreover, for a w/c higher than 0.35, cement content of more than 500 pcy adversely affects the concrete performance by decreasing strength (increasing cement content from 500 pcy to 700 pcy approximately reduced the 28-day compressive strength by 15%) and may cause shrinkage related cracking problems. Therefore, for a given w/c and for the aggregate system used in this study, the range of 500 pcy to 600 pcy is found to be the most appropriate cement content that provides the