More stories about Testing

  • Compressive vs. Flexural Strength

    Is there a good way to correlate core compressive strength and flexural strength? I have a job in which there was only one beam broken, at 28 days, and there are not enough sets to perform any statistical analysis. We are planning to core the pavement and are looking for a comparison between the...

  • More on SCC

    Editor's note: Two readers responded to recent articles on self-consolidating concrete (SCC).

  • Relativity and Rheology

    Editor's note: Two readers responded to recent articles on self-consolidating concrete

  • Air Test Variability

    Is it common to get different air readings when using a pressure meter and a roll-a-meter or volumetric meter? I continually get a difference of about 0.8% to 1%, but I feel very sure my meters are calibrated correctly. The higher reading is from the pressure meter.

  • Is it the Slab's Fault?

    A flooring contractor has experienced problems on four occasions over the years with his two-part polyurethane floor covering not bonding to our concrete slab-on-grade. He has said that the acid-etch process prior to installing the covering did not react very well with our slab surface, based on...

  • Does Intermediate Rounding Decrease Accuracy?

    I have a further question regarding the rounding of compressive strength results (ôHow Precisely Should Labs Round off Compressive Strength Results?ö April, page 26).At our lab, we test 4x8-inch and 6x8-inch concrete cylinders for compressive strength, and we round to the nearest 10 psi according...

  • Nitpicking Slump-Test Results

    A testing firm employee says concrete should be rejected if the slump exceeds the maximum allowable value by as little as 1/4 inch. Is there any published information to help us argue our case?

  • Who Pays for Comparative Testing?

    We're supplying concrete for a parking deck, to be placed by boom pump. The required air content is 4.5% to 7.5%, and, to account for air lost during pumping, specifications require the test lab to perform air-content tests on concrete sampled from the pump discharge hose. We prefer testing for air...

  • Measuring Crack Width in a Concrete Surface

    Our customer has asked us to help him evaluate some cracking that occurred on a recent pour of a large parking lot. We believe that the cracks are caused by dry shrinkage, but the owner is concerned that the cracks are structural in nature. We have agreed to monitor the cracks for a year or so to...

  • Handling Low-Strength Test Results

    Are there any simple guidelines for use when we get low-strength test results? The low tests seem to make owners especially nervous, and we'd like to have an authoritative document that lays out a course of action following the report of a low test.