Slump

Slump is a property of concrete, which is quite commonly measured on a construction project. It is a measurement of the consistency of the concrete, and will be indicative of the behavior of the concrete in the situations where it will be placed. The standard slump test is defined by ASTM C143:

The test is performed with a slump cone (well, actually a frustrum, but who's counting? This is construction after all) and a steel rod. The cone is 12 inches tall, with an 8 inch diameter base, and a 4 inch diameter top. The steel rod is 24 inches long, and 5/8 inch in diameter, with a hemispherical tip. The cone is dampened, then placed on a flat surface. It is then filled in three layers of equal volume. This roughly approximates to filling it to 2 1/2 inches, then 6 inches, and finally to overflowing. Each layer is rodded 25 times, with the roddings ideally penetrating about half an inch into the layer below the one being rodded. After the final layer is rodded, the excess concrete is struck off the top of the mold, and the mold is slowly removed. The mold is then placed next to the concrete, and the rod placed on top of it, parallel with the ground. The distance from the rod to the top of the concrete in inches is the slump of the concrete. As you could probably guess, slump can range from 0 to 12 inches, with 0 being a very stiff concrete, and 12 being a very flowable concrete.

According to ACI 318, concrete should be tested, including slump tests, at least once per day, and once per 150 cubic yards of concrete or 5000 square feet of slab or wall surface area.

Many construction specifications require slump tests to ensure that concrete is of theproper strength. This is due to the belief that the slump is a good indicator of water-cement ratio, a key indicator of concrete strength. However, this is not the case, as many factors influence the slump of a particular mix of concrete, such as coarse and fine aggregate contents, and the use of admixtures such as water reducers or superplasticizers. Slump is only a valid measurement of the consistency of concrete.

Slump (?), n. [Cf. D. slomp a mass, heap, Dan. slump a quantity, and E. slump, v.t.]

The gross amount; the mass; the lump. [Scot.]

 

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Slump, v. t. [Cf. Lump; also Sw. slumpa to bargain for the lump.]

To lump; to throw into a mess.

These different groups . . . are exclusively slumped together under that sense.
Sir W. Hamilton.

 

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Slump, v. i. [imp. & p. p. Slumped (?); p. pr. & vb. n. Slumping.] [Scot. slump a dull noise produced by something falling into a hole, a marsh, a swamp.]

To fall or sink suddenly through or in, when walking on a surface, as on thawing snow or ice, partly frozen ground, a bog, etc., not strong enough to bear the person.

The latter walk on a bottomless quag, into which unawares they may slump.
Barrow.

 

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Slump, n.

1.

A boggy place. [Prov. Eng. & Scot.]

2.

The noise made by anything falling into a hole, or into a soft, miry place. [Scot.]

 

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Slump, v. i.

1.

To slide or slip on a declivity, so that the motion is perceptible; -- said of masses of earth or rock.

2.

To undergo a slump, or sudden decline or falling off; as, the stock slumped ten points. [Colloq.]

 

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Slump, n.

A falling or declining, esp. suddenly and markedly; a falling off; as, a slump in trade, in prices, etc. [Colloq.]

 

© Webster 1913