AASHTO R 72-16 pdf free download

AASHTO R 72-16 pdf free download.Match Curing of Concrete Test Specimens.
3. TERMINOLOGY
3.1. For definitions of terms used in this practice, refer to ASTM C 125.
4. SIGNIFICANCE AND USE
4.1. This method provides a procedure for curing concrete cylinders at the same temperature as that monitored at a specific location in a concrete member. Consequently, the compressive strength of the cylinder more accurately represents the in-place concrete strength of the member. The method is particularly useful for determining the concrete compressive strength at early ages in the fabrication of precast concrete members or for determining the compressive strength of concrete at a critical location in a structural member.
5. APPARATUS
5.1. The apparatus shall consist of a monitoring and heating system capable of maintaining concrete cylinders at a temperature within ±2°C (±4°F) of the temperature of the concrete at a specific location in the member. A satisfactory system may include a temperature sensor in the member, a controller, special insulated cylinder molds with built-in heating systems, and a temperature sensor in the molds.
5.2. Temperature Sensor in the Member—Temperature sensors shall be placed at the most critical locations for strength development. The purchaser shall determine the critical locations for temperature sensors in each type of member and show the locations on the project drawings or the contractor shall submit drawings showing proposed locations to the purchaser for approval.
5.2.1. Temperature sensor wire shall be durable enough to withstand the wear associated with construction operations and shall have a size of 20 awg or larger in diameter (Note 1). Note 1—In locations where electrical interference may affect the measured data, shielded wire should be used.
5.3. Controller—The controller shall be capable of monitoring the temperatures of the member and cylinders and controlling the heating system to maintain the cylinder temperature within +2°C (+4°F) of the temperature measured in the member. Proper operation of the system shall be verified Ofl a regular basis in accordance with the manufacturer’s recommendations.
5.4. Cylinder Molds:
5.4.1. Cylinder molds shall conform to the requirements of M 205M/M 205 for reusable molds and shall be fitted with watertight lids to prevent moisture loss.
5.4.2. Cylinder molds shall have inside nominal diameter by height dimensions of 100 by 200 mm (4 by
8 in.) or 150 by 300 mm (6 by 12 in.).
5.4.3. When heated cylinder molds are used, they shall have built-in thermocouples that sense the temperature of the concrete specimens. Each cylinder mold shall have a heating element that surrounds the core of the mold, provides uniform heat to the concrete specimen, and is capable of maintaining a cylinder temperature that matches the temperature of the concrete member within the stated tolerance (Note 2).
Note 2—Because the match-curing system only provides heat to the cylinder and cannot cool it, the temperature of the cylinder may exceed that of the member if the temperature of the member decreases at a greater rate than that of the cylinder.
6. TEST SPECIMENS
6.1. Test specimens shall be cylinders of concrete cast and hardened in an upright position, with a length equal to twice the diameter. When the nominal maximum size of coarse aggregate does not exceed 50mm (2 in.), the cylinder may be 150 by 300mm (6 by 12 in.). When the nominal maximum size of coarse aggregate does not exceed 25 mm (I in.), the cylinder may be 1(X) by 200 mm (4 by 8 in.).
6.2. A minimum of two 150-by-300-min (6.by-12-in.) or three 100-by-200-mm (4-by-8-in.) cylinders shall be made for each strength test when the specifled strength does not exceed 34 MPa (5000 psi). A minimum of three cylinders shall be made for each strength test when the specified strength exceeds 34 MPa (5000 psi).AASHTO R 72-16 pdf download.