Improving rigid concrete pavement sustainability by minimizing the clinker content

Abstract: Recent policy edicts such as Executive Order 14057 have led to federal, state, and local sustainability policies targeting reduced emissions targets for construction materials. The primary source of emissions in traditional concrete is portland cement clinker which produces approximately 0.9 lb of CO2 per lb of clinker. With these sustainability targets becoming more ubiquitous, materials suppliers and contractors are becoming more willing to provide an accurate account of emissions for given concrete mixture designs. For federal airfield pavement designs, current construction specifications require a minimum cement content for a concrete mixture design. This research investigated airfield pavement designs that incrementally lowered the clinker content below the minimum allowable to assess placement and structural performance in order to assess what changes could be made to current specifications to allow lowered minimum cement contents. The mixture designs investigated in this study varied the coarse aggregate type (limestone and granite), aggregate gradations blends (up to nominal maximum size of 3 in.), and supplementary cementitious materials (Class F fly ash and slag cement). Fresh properties measured included air content, unit weight, slump, and the box test. Cylinder and beam specimens were made to measure compressive and flexural strength, respectively. The results demonstrated that the workability and strength requirements could be met for airfield pavement mixtures with approximately 100 lbs per cubic yard less total cementitious material than the specifications currently require. One additional change to the specifications that make these mixes possible is the ability to use super plasticizing admixtures. The 35% Class F fly ash mixtures and 50% slag cement mixtures were also able to meet strength while providing improved durability properties and ultimately reducing the carbon footprint further.