Ready Mixed Concrete (Structural, LWC 3000-4000 psi)

Concrete is highly customizable in composition. A “straight mix” concrete is made by mixing Portland cement, water, a coarse aggregate, and a fine aggregate, and can include various mineral and chemical admixtures. Structural lightweight concrete uses lightweight aggregates conforming to ASTM C330. It has a compressive strength greater than 2500 psi at 28 days, and an air dry weight less than or equal to 115 lbs/ft³. Both coarse and fine aggregates can be lightweight, but most lightweight concrete uses a lightweight coarse aggregate and normal weight fine aggregate. Non-structural lightweight concrete, having lower density and 28-day compressive strength than structural concrete, was beyond the scope of this Common Product. 

Lightweight aggregates can include a variety of natural expanded materials including vermiculite, clay, shale, slate, and perlite. Synthetic materials such as expanded polystyrene or expanded, pelletized, or sintered fly ash or blast furnace slag can also be used. These materials have low density and higher internal porosity than normal weight aggregates. 

In lightweight concrete a portion of the Portland cement can be replaced by natural or synthetic pozzolans such as fly ash, blast furnace slag, or silica fume. Information on synthetic pozzolans is not included in this CP but is available in the Supplementary Cementitious Materials (SCMs) Common Product. Chemical admixtures added to concrete are highly variable based on local conditions and the desired properties of the concrete. See the All Contents tab for chemicals identified in admixtures specified under ASTM C494/C494M as well as information on recycled aggregates. 

Proportions of Portland cement, water, and aggregates vary based on a number of factors including desired slump, size of coarse aggregate, exposure conditions, and whether or not the concrete is air-entrained. Lightweight concrete may be supplied damp at the time of mixing, and in these cases absorbed water is accounted for when calculating the mixture proportions. This Common Product profile describes the straight mix in-situ/ready mix concrete composition for lightweight, air-entrained, structural concrete under severe exposure conditions. The concrete contains a coarse aggregate with a nominal maximum size of 3/4", a desired slump of 3 to 4 inches, and a compressive strength of 4000 psi at 28 days. The replacement of a portion of Portland cement with SCMs and the use of chemical admixtures will alter these proportions, and the exact amounts of all ingredients in concrete will vary based on the contractor, concrete supplier, and the materials used by the supplier to mix the concrete ordered.

A historical version of this CP is available here: Historical: Ready Mixed Concrete (LWC 3000-4000psi) - 2015.