Concrete Unit Weight
Concrete Unit Weight
(OP)
Concrete mix designs typically give a dry and plastic/wet unit weight. Is there a reference for what the final in-situ unit weight would be since some of the water evaporates? More or a curiosity on my part, but I would think the final weight would be somewhere in between.






RE: Concrete Unit Weight
When you are dealing with mix designs and testing for results, you could be in "never-never land".
A guess that definitely, a figure between the two densities and much closer to the dry weight since a significant amount of moisture is removed during the hydration and curing process, but should be good enough for curiosity. this could shift depending on whether it is lightweight concrete (less than 115 pcf) or normal concrete (140-150) using most natural aggregates.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Concrete Unit Weight
I'm not sure I follow that statement. Steel has a density of 490 pcf and concrete is 150 pcf. More steel does not mean lower unit weight of a reinforced concrete element.
RE: Concrete Unit Weight
dcarr82775 - To split hairs, the density of the aggregate used has an effect on the density. Common aggregates (igneous and sedimentary) do have a range of densities. In some cases, a mixture of "lightweight" aggregates (natural and manufactured) can produce densities of less than 100 pcf where lower weights, higher fire resistance or greater insulation are required. For an extreme example, very heavy aggregates (hematite and others) have been used for containment in plants the need radioactive protection where the wall thicknesses are limited.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Concrete Unit Weight
Depending on the type of coarse aggregate used, the unit weight of normal weight concrete will generally range from about 140 pcf to about 155 pcf, the values typically used in design calcs.
RE: Concrete Unit Weight
Hydration of concrete requires somewhere around 0.25 w/c ratio (although this is debated, it is the theoretical requirement.) As noted, the trapped moisture in voids also sequesters a fair amount of moisture. Do not count on evaporation of any of the moisture in the concrete, since properly cured concrete retains most of the mix water. Also, aggregates are processed into ready mix at a saturated, surface dry (SSD) condition, so the water added to the mix is not all that is there or all that remains for a long period after placement.
RE: Concrete Unit Weight
RE: Concrete Unit Weight