More stories about Ready-Mixed Concrete

  • 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...

  • Algae in Mix Water Can Affect Air, Strength

    We recently supplied a house slab where the bleedwater had a greenish tint. We discovered that the water retention pond we used for water collection had green algae that had formed on the surface and was used for concrete production. The concrete met and gained strength normally, however. Is there...

  • Do Fibers Reduce Permeability?

    A customer has asked us to include fibers in the mix design for a water retention tank. The idea is that the fibers will reduce the permeability of the concrete. Is that true?

  • 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...

  • How Often to Check Mixing Drums

    We have our plants inspected and certified in accordance with the checklist in Section 3 of the National Ready Mixed Concrete Association's Quality Control Manual. This certification includes truck mixer inspection to ensure that there's no appreciable accumulation of hardened concrete in the drum...

  • 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.

  • Does Cement Brand Affect Air Content?

    When we change from one cement brand to another, we often need to adjust the dosage of our air-entraining admixture. Sometimes a new shipment of cement from the same source also requires dosage changes. Is this normal, or are we doing something wrong?

  • Acidic Mix Water

    Our water source for use in ready-mixed concrete is acidic, with a pH ranging from 5 to 6. What are the effects of this low pH, and what can be done to reduce acidity?

  • A Possible Use for Reclaimer Sludge

    Can reclaimer sludge be used to reduce soil acidity?