C157

[ATSE]

ASTM C157 is a lab-sampled test.
However, I sometimes require field sampling for C157 in the contract documents during concrete production, alongside C31 sampling / C39 testing. That is, sampling at truck discharge, then transporting to the lab.

I realize this is a bit unconventional and imperfect, and the results have higher variability.
[Aside: ASTM C157 has a brief acknowledgement of field sampling.]
The goal: confirm that the fresh concrete delivered to the site is somewhat close to that perfect concrete that the readymix lab tested.

Has anyone ever specified C157 sampling outside a lab, or something similar?
If not, can you recommend an alternate method of verifying shrinkage ("length change") for the as-delivered concrete, particularly for hydraulic structures.

Compression "break" testing is most loved - maybe because they are familiar, easy, gives higher than expected results, and usually doesn't cause trouble.
But shrinkage is a big deal in my world, and strength is no proxy for shrinkage.

 

[r13]

Below are excerptions from ASTM C157 / C157M - Standard Test Method for Length Change of Hardened Hydraulic-Cement Mortar and Concrete. Are you concerned with concrete shrinkage in general, or concrete mix using hydraulic cement? I think there is difference between the former and the latter, which is the focus of C157.

Significance and Use

4.1 Measurement of length change permits assessment of the potential for volumetric expansion or contraction of mortar or concrete due to various causes other than applied force or temperature change. This test method is particularly useful for comparative evaluation of this potential in different hydraulic-cement mortar or concrete mixtures.

1. Scope

1.1 This test method covers the determination of the length changes that are produced by causes other than externally applied forces and temperature changes in hardened hydraulic-cement mortar and concrete specimens made in the laboratory and exposed to controlled conditions of temperature and moisture.

ASTM Standards

C125 Terminology Relating to Concrete and Concrete Aggregates
C143/C143M Test Method for Slump of Hydraulic-Cement Concrete
C172 Practice for Sampling Freshly Mixed Concrete
C192/C192M Practice for Making and Curing Concrete Test Specimens in the Laboratory
C305 Practice for Mechanical Mixing of Hydraulic Cement Pastes and Mortars of Plastic Consistency
C490 Practice for Use of Apparatus for the Determination of Length Change of Hardened Cement Paste, Mortar, and Concrete
C511 Specification for Mixing Rooms, Moist Cabinets, Moist Rooms, and Water Storage Tanks Used in the Testing of Hydraulic Cements and Concretes
C596 Test Method for Drying Shrinkage of Mortar Containing Hydraulic Cement
C1437 Test Method for Flow of Hydraulic Cement Mortar
E11 Specification for Woven Wire Test Sieve Cloth and Test Sieves
E337 Test Method for Measuring Humidity with a Psychrometer (the Measurement of Wet- and Dry-Bulb Temperatures)

 

[ATSE]

r13 - thanks for your response.
I do have a copy of ASTM C157.
I am concerned with shrinkage of cast-in-place concrete for hydraulic structures, and I use C157 test results (via concrete specimens) to estimate that shrinkage for various concrete mix designs.
My question is about field vs lab sampling.
As an aside, if you have experience with hydraulic structures and you are aware of a better (and still common) test procedure to evaluate length change of concrete between placement and 28-days (or 56-days), I am interested in that as well.

 

[Settingsun]

Can't help with US codes, but the Australian code applies to both lab and field samples. It requires that field samples are reported as such, acknowledging that the non-standard initial curing makes the results not directly comparable.

As a practical matter, you still miss the field curing impacts vs lab curing, and it's often too late by 56 days for the results to matter.

 

[r13]

ATSE,

I think the focus point lies in the scope of this spec:

1. Scope

1.1 This test method covers the determination of the length changes that are produced by causes other than externally applied forces and temperature changes in hardened hydraulic-cement mortar and concrete specimens made in the laboratory and exposed to controlled conditions of temperature and moisture.

You have to ask whether the field sampling/specimen can meet the laboratory/controlled conditions, which were the bases of this spec was written on. IMO, this spec should be specified in the document issued to the lab designing the concrete mix, and the concrete supplier, in order to achieve the goal of producing high quality/low shrinkage concrete. I doubt its applicability in the field though.

 

[ATSE]

steveh - Thanks for the response. Yes, can't strictly compare field and lab initial cured samples. Good comment. Somewhat surprisingly, field sampled prisms and lab sampled prisms give close shrinkage results (my experience).

r13, Thanks again for the response. Since we're citing C157 directly,
"When collecting samples in nonstandard conditions, such as field concrete, it is suggested that Practice C 172 be followed."
If reading the "spirit" of C157, it seems to acknowledge field sampling as nonstandard, but okay, and does not restrict / forbid it.

 

[r13]

Since C172 is referenced in C157, if there is mentioning of adjustment for ambient temperature and humidity in C172, and it references C157, then I think you are fine to add C157 to the construction contract document.