Concrete inFocus - Spring 2013 - (Page 18)

research Acceptance Test Reports for Ready Mixed Concrete Who Should Get Them? Colin Lobo T he process of testing concrete is reasonably well established for quality assurance of ready mixed concrete delivered to projects. The owner or his representative hires an independent testing and/or inspection agency to perform quality assurance functions during the construction of the Work. Industry standards provide requirements for the following: • Qualification of testing agencies and testing technicians; • Frequency of testing; • Standardized procedures for obtaining samples and performing tests; • Acceptance criteria for fresh and hardened concrete tests; and • Referee testing and criteria for tests that fail to meet the acceptance criteria. Standards require the concrete supplier to maintain a quality control plan and to take steps to respond to situations when test results are trending towards potential noncompliance. Prior to a project, the supplier is required to use a complete test record from previous projects as a basis for establishing their concrete mixture proportions and properties for new work and to provide this documentation in a submittal to the engineer of record. To meet these requirements, it is essential that the concrete supplier be provided ALL reports of acceptance tests performed on the concrete mixtures delivered during the progress of a project. These test reports should be provided in a timely manner so that proactive action can be taken to ensure that specified requirements for concrete, especially strength, are not violated. When low-strength problems occur, considerable time and money is expended to evaluate the cause and to take corrective action. It is thereby beneficial to all parties to minimize the risk of low-strength concrete. Why is the distribution of test reports an issue? Some testing agencies do not provide 18 ı SPRING 2013 test reports to concrete suppliers because they believe these reports should only go to the entity that contracted with them for the testing services. Some believe that distribution of test reports to several entities increases their cost, although this concern should be less of an issue with the widespread availability of electronic communication. Some testing agencies only provide failing strength test results to concrete suppliers to notify them that a problem exists. Clearly, this is undesirable because if previous tests were provided and a trend was observed, the failing test result could have likely been avoided. Many concrete producers have established relationships with local testing agencies to ensure that test reports of all tests performed on their concrete are distributed to them. Figure 1. Monitoring strength test results relative to strength acceptance criteria. Figure 2. Running average of three consecutive test results relative to the specified strength. http://www.naylornetwork.com/nrc-nxt/

Table of Contents for the Digital Edition of Concrete inFocus - Spring 2013

Corporate Suite
Enviro Scene
A Legacy in Construction
CalPortland Slip Form Success
Fly Ash FAQ
Acceptance Test Reports for Ready Mixed Concrete
First Batch Plant Certifications in Mongolia
Index of Advertisers
Taking It to the Streets
Impact of Specifications on Concrete Quality

Concrete inFocus - Spring 2013

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