TERMINOLOGIES (GLOSSARY) FOR CONCRETE ADMIXTURES

Admixture—A material other than water, aggregates, hydraulic cement, and fiber reinforcement, used as an ingredient of a cementitious mixture to modify its freshly mixed, setting, or hardened properties and that is added to the batch before or during its mixing.

Admixture, accelerating—An admixture that causes an increase in the rate of hydration of the hydraulic cement, and thus, shortens the time of setting, increases the rate of strength development, or both.

Admixture, air-entraining—An admixture that causes the development of a system of microscopic air bubbles in concrete, mortar, or cement paste during mixing.

Admixture, retarding—An admixture that causes a decrease in the rate of hydration of the hydraulic cement and lengthens the time of setting.

Admixture, water-reducing—An admixture that either increases slump of freshly mixed mortar or concrete without increasing water content or maintains slump with a reduced amount of water, the effect being due to factors other than air entrainment.

Admixture, water-reducing high-range—A water reducing admixture capable of producing large water reduction or great flowability without causing undue set retardation or entrainment of air in mortar or concrete.

Aggregate, reactive—Aggregate containing substances capable of reacting chemically with the products of solution or hydration of the portland cement in concrete or mortar under ordinary conditions of exposure, resulting in some cases in harmful expansion, cracking, or staining.

Air, entrained—Microscopic air bubbles intentionally incorporated in mortar or concrete during mixing, usually by use of a surface-active agent; typically between 10 and 1000 μm in diameter and spherical or nearly so.

Air, entrapped—Air voids in concrete that are not purposely entrained and are significantly larger and less useful than those of entrained air, 1 mm in diameter or larger in size.

Air content—The total volume of air voids in cement paste, mortar, or concrete, exclusive of pore space in aggregate particles, usually expressed as a percentage of volume of the paste, mortar, or concrete.

Alkali—Salts of alkali metals, principally sodium and potassium, specifically sodium and potassium occurring in constituents of concrete and mortar, usually expressed in chemical analysis as the oxides Na2 O and K2

Alkali-aggregate reaction—Chemical reaction in either mortar or concrete between alkalies (sodium and potassium) from portland cement or other sources and certain constituents of some aggregates, under certain conditions, deleterious expansion of concrete or mortar may result.

Alkali-carbonate reaction—The reaction between the alkalies (sodium and potassium) in portland cement and certain carbonate rocks, particularly calcitic dolomite and dolomitic limestones, present in some aggregates, the products of the reaction may cause abnormal expansion and cracking of concrete in service.

Alkali-silica reaction—The reaction between the alkalies (sodium and potassium) in portland cement and certain siliceous rocks or minerals, such as opaline chert, strained quartz and acidic volcanic glass, present in some aggregates; the products of the reaction may cause abnormal expansion and cracking of concrete in service.

Calcium chloride—A crystalline solid, CaCl2 ; in various technical grades, used as a drying agent, as an accelerator for fresh concrete, a deicing chemical, and for other purposes.

Cement, portland—A hydraulic cement produced by pulverizing portland-cement clinker and usually containing calcium sulfate.

Cementitious—Having cementing properties.

Sulfate attack—Either a chemical or physical reaction or both that occurs between sulfates usually in soil or groundwater and concrete or mortar; the chemical reaction is primarily with calcium aluminate hydrates in the cement-paste matrix, often causing deterioration.

Sulfate resistance—Ability of concrete or mortar to withstand sulfate attack.