Concrete Cylinder Sampling Procedure #construction #concrete #sampling #concreting #juancivilian

How to Make and Cure Standard Test Cylinders in the Field

1. Obtain a representative concrete sample from the revolving drum truck mixer.

Ensure all water has been added to the concrete.

Sample concrete at two or more regularly spaced intervals during discharge of the middle portion of the load.

Repeatedly pass the receptacle through the entire discharge stream or completely divert the discharge stream into the sample container.

Transport samples to the place of testing and remix to form a composite sample.

Obtain the concrete sample within 15 minutes from the start of sampling.

Start molding cylinders within 15 minutes after fabricating the composite sample.

2. Using a scoop, place concrete in the cylinder molds. For 6 by 12 inch molds, place in three equal layers (1/3 volume per layer) and for 4 by 8 inch molds, place in two equal layers (1/2 volume per layer).

3. Rod each layer 25 times throughout the layer depth distributing the roddings uniformly over the cross section. For subsequent layers, penetrate the previous layers about 1 inch. For 6 by 12 inch molds use a 5/8 inch diameter tamping rod and a 3/8 inch diameter rod for 4 by 8 inch molds.

4. Lightly tap the outside of the mold 10 to 15 times with a rubber mallet to close the voids left by the tamping rod. Use an open hand for single use molds easily damaged by a mallet.

5. Strike off the surface with the tamping rod, handheld float or trowel to produce a flat, even surface. Install the mold cap and move the cylinders to an initial curing place for storage.

6. For initial curing, store cylinders for a period up to 48 hours in a temperature range from 60 to 80° F and protect from moisture loss. For concrete with a specified strength of 6,000 psi or greater, the initial curing temperature range is between 68 and 78° F.

7. After initial curing and within 30 minutes upon removal from molds, start final curing by storing cylinders in a wet environment at a temperature of 73.5 ±3.5° F until tested.

Source: Kim Basham, PhD PE FACI ( https://www.forconstructionpros.com/concrete/article/10846921/how-to-make-and-cure-standard-concrete-test-cylinders-in-the-field)

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