ASTM C143/C143M
Standard Test Method for Slump of Hydraulic-Cement Concrete
The slump test — the cone-and-tape measurement of how stiff or fluid a load of fresh concrete is.
Who needs it
Field technicians, inspectors, finishers, and anyone accepting or rejecting a ready-mix truck at the chute.
What the test involves
Fresh concrete is placed into a standard steel cone in layers, each rodded a set number of times, then the cone is lifted straight up and the concrete is allowed to subside. The distance the concrete drops from the original cone height is the slump. The method also defines how quickly the whole test must be completed, because concrete stiffens measurably while the technician works.
Common misconceptions
- Slump is a consistency measurement, not a strength or quality measurement. Two mixes with identical slump can have very different strengths.
- Adding water at the site to raise slump raises the water-cement ratio and lowers strength and durability, which is why water addition is controlled by the ready-mix specification rather than by preference.
- A high slump caused by a water-reducing admixture is not the same as a high slump caused by extra water. The first can leave strength intact; the second does not.
Official source
We summarize scope and purpose only. The full text belongs to the issuing body — read it at the official source. ASTM International