Concrete Products

JAN 2019

Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.

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74 • January 2019 TECHNICAL TALK PRACTICE frequently as every hour. After the concrete begins to cool and/or the temperature differential remains within the specified range for several consecutive days, the temperature readings can be captured less frequently. Modern sensor technology offers users the ability to define the desired time intervals for acquiring sensor data. Once acquired, the data can be downloaded into software or a mobile app and used to generate reports of temperature history and temperature differential data for easy disbursement. Some mass concrete placement projects require installation of a redundant set of sensors at locations near the primary set. Data from the former is usually only acquired and recorded in the event the primary temperature sensors fail. In that case, the contractor must seek an immediate fix. If the primary system cannot be fixed, the backup temperature monitoring system must be put into service. Fail- ure to properly monitor the temperature of mass placements during the heat dissipation phase can result in the mass concrete element being rejected. Rejected elements usually must be removed at the contractor's expense. QC ALL AROUND In addition to meeting mass placement specifications, there are other ways that monitoring temperatures in general can be beneficial. Data can also be used for: • Characterizing materials; • Investigating interactions; • Tracking uniformity; • Timing finishing activities; • Tracking hydration; and, • Calculating concrete maturity. To reiterate: Minimizing the risk of temperature-related damage is a fundamental part of every mass placement project. The two main temperature-related issues to monitor in mass concrete are maximum internal temperature and temperature differential. Exceeding speci- fied limits puts concrete at increased risk of severe cracking. Thermal control plans describe the temperature monitoring procedures that a contractor intends to follow. Command Center is a system developed specifically for monitoring internal concrete temperatures and estimating concrete strength by the maturity method. Command Center sensors are among the most affordable self-logging devices available for this purpose, and greatly simplify the process. Command Center offers free software for view- ing and analyzing data, and both wired and wireless data retrieval options that are suitable for any mass placement project. — www. Sabrina Garber is Command Center Project Manager with Austin, Texas-based Transtec Group Inc., a pavement engineering specialist credited with technologies and methods advancing conventional cast- in-place and precast concrete slabs; Ohio-Kentucky River Bridge

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