Concretum Aeternus: How to keep concrete forever solid.

• Date: 01 August 2022
• Author: Kvapil, Rachael
• Published date: 01 August 2022
• Author: Kvapil, Rachael

Concrete is the foundation of modern civilization. This ancient construction material is as much a part of the modern urban landscape as wood, brick, steel, and asphalt. Its ingredients are simple: water, cement, aggregate (sand and gravel), and air. However, strength and durability depend on the mix-design as much as proper application and curing. Done correctly, concrete structures can last a lifetime or, in the case of the Roman Pantheon and Colosseum, outlast the culture that built them. Despite its staying power, manufacturers and mix-designers are always looking for ways to improve concrete for enhanced performance and environmental sustainability.

Manufacturing Concrete

Given that concrete is composed of few ingredients, manufacturing it should be simple, yet mix designs vary depending on their application. According to the Portland Cement Association (based in Skokie, Illinois; Portland cement is named for an English island), a typical concrete mixture starts with 10 to 15 percent cement and 15 to 20 percent water that creates a paste that coats 60 to 75 percent aggregate. Around 5 to 8 percent entrained air (purposely created air bubbles) is added during the mixing process to make concrete more workable during placement and increase its durability when hardened in climates with high freeze-thaw cycles.

Scott Davis, president of Davis Block & Concrete (one of approximately twenty concrete manufacturers in Alaska), explains there are five steps to the concrete manufacturing process. The first involves batching, where materials are measured for the concrete mix. Once the materials are measured, they're mixed to the desired level of consistency. Depending on the project, concrete can be mixed by hand, by stationary mixer, or during transport. Once mixed, concrete is transported and placed using a variety of methods that range from manual application to large pump trucks equipped with booms. While still wet, the concrete must be compacted before it can be cured, often with additional chemicals, and finished.

Concrete is used in many ways in commercial and residential construction projects. As building material, concrete is used for foundations, superstructures, columns, driveways, floor construction, and exterior surfaces. For infrastructure, concrete is used to build bridges, dams, wastewater treatment facilities, traffic guides/barriers, sidewalks and curbs, and parking lots/structures. Concrete roads and highways are rarely found in...