As part of its proficiency sample program, the ASTM-sponsored Cement and Concrete Reference Laboratory (CCRL), located at NIST, issues two portland cements semi-annually for testing by the appropriate ASTM chemical and physical test methods by participating laboratories [5]. CCRL issued Cements 115 and 116 in January of 1995. A sufficient supply of these cements stored in a double layer of plastic in cardboard boxes was obtained for the present studies. Results [5], obtained using the appropriate ASTM [6] test method, and available in the CCRL report, include the cements' oxide compositions (ASTM C114), the initial and final times of set via the Vicat (ASTM C191) and Gillmore (ASTM C266) needle methods, measured finenesses (ASTM C204 and C115), mortar cube compressive strengths (ASTM C109), and the heats of hydration at 7 and 28 days of age measured via the heat of solution method (ASTM C186).
For the non-evaporable water content and chemical shrinkage studies described below, cement pastes were prepared with water-to-cement (w/c) ratios of 0.3, 0.4, and 0.45. The cement powder and necessary mass of water were mixed together by kneading by hand in a sealed plastic bag for two to three minutes. Samples were then removed and stored in capped plastic vials and small glass jars for the non-evaporable water content and chemical shrinkage measurements, respectively. In both cases, after placing the cement paste sample (typically 10-15 grams) in its container, about 1 ml of water was added on top of the cement paste to maintain saturated conditions throughout the experiment. For the non-evaporable water content measurement, the samples were stored at 25 ºC until being evaluated. Evaluations of non-evaporable water content were typically made after the following times of hydration: 8 hours and 1, 2, 3, 7, 14, 28, 56, and 90 days.