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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...
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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...
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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.
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Of the three methods for measuring air content--pressure, volumetric, and gravimetric--which one is the most reliable?
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I've heard that the two-cone fracture pattern is typical when compressive-strength cylinders are tested. Does that mean any other fracture pattern indicates a testing or concrete problem?
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We're supplying concrete for a tilt-up project that requires concrete with a 3500-psi (25 MPa) 28-day compressive strength. In addition to making standard test cylinders, the tilt-up contractor is also making beams that are stored in the field before they're tested. Because of nonstandard curing...
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We recently supplied controlled low-strength material (CLSM) for backfill. Specifications called for a maximum 28-day compressive strength of 200 psi to allow excavation by backhoe at a later date. We designed for a strength between 50 and 150 psi, but cylinder breaks indicated compressive...