Studies have been conducted on three different systems: 1) bulk liquids, 2) cement pastes, and 3) mortars. For the bulk liquids, the properties of distilled water were contrasted against a solution prepared by adding 6 % by mass of Eclipse SRA 2 to distilled water. The surface tensions of the two solutions were measured at 23 ºC (and 55 % RH) using a Dunouy tensiometer. In addition, mass loss measurements were made for the solutions placed in parallelpiped cuvettes 10 mm x 10 mm x 5 mm deep, open at one end. These cuvettes were exposed to a constant environment of approximately 25 ºC and 50 % RH.
Two cements were used for the cement paste studies. Mass loss measurements and concurrent X-ray absorption measurements to determine the drying profiles [4,5,6] were performed for cement pastes with a w/c ratio of 0.35, prepared using a low alkali sulfate-resistant Aalborg portland cement. The cement has a Blaine fineness of 368 m2 /kg and a Bogue calculated phase composition of 58 % C3S, 25 % C2S, 4.0 % C3A, and 7.3 % C4AF, with a 3.4 % calcium sulfate content. Pastes were prepared with distilled water, and with and without a 2 % mass addition (by mass of cement) of the SRA. The pastes were mixed by hand and placed in cuvettes. Drying kinetics were monitored both in the lab and in the X-ray environmental chamber (a slightly more severe drying environment due to the air circulation within the chamber). In addition to the two "pure" systems, two composite layered systems were also prepared. Both possible layerings, paste with the SRA over paste without the SRA and vice versa, were examined in this study.
For a second experiment, cement paste specimens were prepared from an ultrafine cement with a Blaine fineness of 654 m2/kg. This cement's potential Bogue composition was 73.5 % C3S, 16.5 % C2S, 7.1 % C3A, and 2.5 % C4AF. Cement pastes with a w/c=0.3, with and without a 2 % mass addition of the SRA, were mixed by hand. The internal relative humidity of these pastes under sealed curing conditions at 25 ºC was monitored for 11 d using a Rotronic Hygroscope DT equipped with four measuring cells [7]. Before and after this experimental run, the Rotronics equipment was calibrated using salt solutions with RHs between 75 % and 100 %. For companion specimens, the maximum standard deviation in RH between readings was 0.42 %, with an average standard deviation of 0.17 %. After the 11 d of sealed curing, the non-evaporable water contents of the specimens were determined by loss on ignition (mass at 1050 ºC vs. mass at 105 ºC). The measured values were corrected for the loss on ignition of the cement powder. For the specimens with the SRA, the results were further corrected by 0.02 to account for the 2 % addition of organic SRA (boiling point of about 212 ºC).
Finally, mortars were prepared using the low alkali portland cement with a water-to-solid binder (w/s- where binder is cement + silica fume) ratio of 0.35 and an 8 % replacement of cement by silica fume (mass basis). The silica fume used had a specific surface area of 23.2 m2/g. Once again, mortars with and without a 2 % addition of the SRA were prepared by mixing in a 5-liter epicyclic mixer. For these mortars, prepared with CEN standard sand EN 196-1, the following measurements were performed: cylinder compressive strength after 7 d and 28 d of sealed curing, internal relative humidity development over the course of at least 21 d, and autogenous deformation using a custom-built dilatometer immersed in a constant temperature oil bath [8,9]. After setting was achieved, the maximum standard deviation in relative deformation (dilatometer) readings made on companion specimens was 27 microstrains, with typical standard deviations being in the range of 5 microstrains to 17 microstrains. For this portion of the study, all curing and measurements were conducted at a temperature of 30 ºC under sealed conditions.
2 Certain materials and commercial equipment are identified in this paper to specify the experimental procedure. In no case does such identification imply endorsement by the National Institute of Standards and Technology, nor does it indicate that the products are necessarily the best available for the purpose.