Minimizing Cementitious Content for Performance and Sustainability in Rigid Pavements

The production of each ton of portland cement clinker emits approximately 1 ton of carbon dioxide. Therefore, there is a demand on the industry to reduce its carbon footprint by environmental agencies. A solution for the concrete construction industry is to use cement more efficiently. However, many concrete specifications impose minimum cementitious contents that may be in excess of those required to achieve desired durability and strength, leading to increased costs and increased carbon loading on the environment. In addition, in some cases, excessive cementitious content adversely affects concrete performance and durability by causing shrinkage related cracking. Therefore, minimizing the cementitious amount will not only reduce the cost but also lead to a more sustainable method of constructing performance-based rigid pavements. The main purpose of this research is to investigate the minimum cementitious content required with an appropriate water to cementitious ratio (w/cm) to meet given workability, strength, and durability requirements in a rigid pavement; and so to reduce carbon dioxide emissions, energy consumption, and cost. This paper presents an experimental program that was conducted on 32 concrete mixtures with w/cm ranging between 0.35 and 0.50; and cementitious contents ranging from 400 to 700 pcy. 16 mixtures were prepared using ASTM Type I ordinary portland cement and 16 contained ASTM C618 class C fly ash at 20% of portland cement replacement level. Hardened concrete properties such as compressive strength, chloride penetration and air permeability were determined up to 90 days. The test results showed that strength is a function of w/cm and independent of the cementitious content after a certain cementitious content is reached, for a given w/cm. Chloride penetration increases as w/cm or cementitious content increases. At constant w/cm, air permeability also increases as cementitious content increases. For the aggregate system used in this work, 500 pcy is found to be the most appropriate cementitious content that provides a workable mixture whilst meeting the desired strength and durability performance of mixtures. Based on these findings, it is possible to reduce the use of cementitious content without sacrificing the desired strength and durability