Carbon Sequestration of Concrete Masonry Units

Early-age carbonation curing of concrete products results in improved strength, increased surface hardness, and reduced surface permeability to water, as well as the reduction of efflorescence. Carbonation reactions between carbon dioxide and calcium compounds result in permanent fixture of the carbon dioxide in thermodynamic stable calcium carbonate. The moisture content, relative humidity, and temperature profile of the hydrated system have considerable and important influence on the rate and ultimate extent of carbonation. During carbonation, CO₂ penetrates the surface of concrete and reacts with cement hydration products—namely, calcium hydroxide and calcium silicate hydrates—to form carbonates. This study quantifies carbon sequestration levels in concrete masonry units using various curing methodologies. The test results of a dynamic pressurized CO₂ curing chamber and normal ambient CO₂ pressure at various concentrations levels are compared to traditional kiln curing procedures. Early compressive strength profiles for 30% CO2 cured concrete masonry units (CMUs) are equivalent to 100% CO₂ cured CMUs and exceed the traditional kiln-cured compressive strengths. Carbon sequestration reduced water requirements by 20% for optimum strength performance and provided water conservation opportunities.