ACI 211.1-91 ACI Standard Practice for Selecting Proportions for Normal Heavyweight, and Mass Concrete

This Best Practice of ACI 211.1-91 ACI Standard Practice for Selecting Proportions for Normal Heavyweight, and Mass Concrete outlines strategies for choosing hydraulic cement concrete proportions made with and without other cement materials and chemical admixtures. This concrete consists of regular and/or high-density aggregates (as distinguished from lightweight aggregates) with workability appropriate for ordinary cast-in-place construction (as distinguished from special mixtures for the manufacture of concrete products). A summary of the methods used to pick proportions for mass concrete is also included.
Portland cement (ASTM C 150) and mixed cement (ASTM C 595) are hydraulic cements referred to in this Good Practice. The norm does not include compressed silage proportioning with condensed silica fume.

ACI 211.1-91 ACI Standard Practice for Selecting Proportions for Normal Heavyweight, and Mass Concrete

1 Concrete consists mainly of aggregates, a portland or mixed cement and water and may contain other cement and/or chemical admixtures. It will contain a certain amount of trapped air and may also contain intentionally trained air collected through the use of a cement admixture or air conditioning. Chemical admixtures are often used to accelerate, pause, enhance workability, increasing the need for mixing water, increase power, or modify other concrete properties (see ACI 212.3R).

Depending on the type and quantity, other cementitious materials such as fly ash (see ACI 226.3R) natural pozzolans, ground granulated blast furnace (GGBF) slag (see ACI 226.1R) or silica fumes may be used in combination with portland or mixed cement for economical purposes or to provide specific properties such as reduced early hydration heat, enhanced late-age resistance or increased resistance.

2 The choice of concrete proportions requires a balance between efficiency and placeability, strength, toughness, density and appearance requirements. The required characteristics are governed by the use to which the concrete will be placed and the conditions that are expected to be met at the time of placement. In the job specifications, these characteristics should be listed.

3 The ability to adapt concrete properties to the needs of the workforce demonstrates technological developments, most of which have occurred since the early 1900s. In 1918 was recognized the use of watering ratio as a method for estimating force. The impressive durability gain resulting from air entry was recognized in the early 1940s. Such two major developments in concrete engineering have been improved in many related areas by comprehensive research and development, including the use of admixtures to overcome possible defects, create special properties, or achieve productivity (ACI 212.2R).