Researchers have found waste foundry sand (FS) and coconut shells (CS) served as acceptable substitutes for fine or coarse aggregates in concrete, but the waste products performed better when mixed together. Researchers wrote: “CS-FS concrete exhibited superior properties over individual replacements due to the formation of a dense matrix.”



From the smallest local agencies to state DOTs, there’s been a growing emphasis on making infrastructure more sustainable and resilient. Accelerating this is the November 2021 Infrastructure and Investment in Jobs Act which incentivizes the use of local materials, such as concrete, and funds investment in the decarbonization of such materials.

Concrete is one of the oldest building materials known to man, with a history dating back to ancient Rome and earlier. Today, concrete—comprised primarily of aggregate, cementitious materials, and water—is the most widely used building material on the planet. Without it, modern society could not exist.

Concrete is often claimed to have a high carbon footprint, but this is due to its abundant use more than to its carbon footprint per unit produced. Most of its carbon emissions are associated with manufacturing portland cement, one of modern concrete’s major components. Furthermore, concrete is a long-lived material, which reduces the impact of the carbon produced during its manufacture over the extended service life.

There is another, less-talked-about way in which concrete contributes to sustainability: carbonation. During the production of portland cement, limestone consisting of calcium carbonate is added to the kiln. When heated to a high temperature, the calcium carbonate (CaCO3) converts to lime (CaO)—the product required for portland cement production—and CO2,