AASHTO T23:2014 Standard Method of Test for Making and Curing Concrete Test Specimens in the Field.
4. SIGNIFICANCE AND USE
This method provides standardized requirements for making, curing. protecting. and transporting concrete test specimens under field conditions.
4.2. If the specimens are made and standard cured, as stipulated herein, the resulting strength test data where the specimens are tested arc able to be used for the following purposes:
4.2.1. Acceptance testing for specified strength,
4.2.2. Checking the adequacy of mixture proportions for strength.
4.2.3. Quality control.
4.3. If the specimens are made and field cured, as stipulated herein, the resulting strength test data when the specimens are tested are able to be used for the following purposes:
4.3.1. Determination of whether a structure is capable of being put in service,
4.3.2. Comparison with test results of standard cured specimens or with test results from various in-place test methods,
4.3.3. Adequacy of curing and protection of concrete in the structure, or
4.3.4. Form or shoring removal time requirements.
Molds, General—Molds tbr specimens or fastenings thereto in contact with the concrete shall be made of steel, cast iron, or other nonabsorbent material, nonreactive with concrete containing portland or other hydraulic cements. Molds shall hold their dimensions and shape under conditions of use. Molds shall be watertight during use as judged by their ability to hold water poured into them. Provisions for tests of watertightness are given in M 205M/M 205. A suitable sealant, such as heavy grease, modeling clay, or microcrystalline wax shall be used where necessary to prevent leakage through the joints. Positive means shall be provided to hold base plates firmly to the molds. Reusable molds shall be lightly coated with mineral oil or a suitable nonreactive form release material before use.
5.3. Bewn Molds—Beam molds shall be of the shape and dimensions required to produce the specimens stipulated in Section 6.2. The inside surfaces of the molds shall be smooth. The sides. bottom, and ends shall be at right angles to each other and shall be straight and true and free of warpage. Maximum variation from the nominal cross section shall not exceed 3.2 mm for molds with depth or breadth of 152 mm (6 in.) or more. Molds shall produce specimens not more than 1.6 mm shorter than the required length in accordance with Section 5.2. but may exceed it by more than that amount.
5.4. Twnping Rods—Three sizes are specified as indicated in Table 1. Each shall be a round, straight steel rod with at least the tamping end rounded to a hemispherical tip of the same diameter as the rod. Both ends may be rounded if preferred.AASHTO T23 pdf download.