Title: Cure Temperature Reduction by the Use of High-Range Water-Reducing Admixtures
Author(s): Lawrence R. Roberts
Publication: Symposium Paper
Appears on pages(s): 337-358
Keywords: admixtures; age-strength relation; cement content; com- -- pressive strength; curing; energy; mix proportioning; naphthalene
compounds; plasticizers; precast concrete; prestressed concrete;
temperature; water-reducing agents.
-v I High range water reducing admixtures (HRWR'S), common y known as superplasticizers, can be used in prestressed or precast concrete to reduce cycle times, cement content, or elevated curing temperatures. With today's high energy costs, the reduction or elimination of elevated curing may provide the greatest payback for the use of such admixtures. In this study, the ability of a naphthalene sulfonate type high range water reducer to decrease the curing energy requirement was investigated using four different cements, one ASTM Type III, two Type I, and one Type I/II. The proportions of the concrete mixtures were fixed at 360 Kg/m3 cement content, while three different temperatures, 22"C, 44"C, and 66"C, were used to cure specimens from each batch. Compressive strengths were determined at 12 or 18 hours, and 28 days. Comparison was made between unadmixtured concrete, that containing a normal water reducing admixture, and that contain-ing the high range water reducer. The ability to reduce curing temperature was shown to depend on the cement type, testing age, and strength requirement to be met. Use of the HRWR permitted reduction of curing temperature for the Type III cement, or substitution of a Type I or I/II cement for the Type III, but not both. At 18 hours age, cement substitution and some tem-perature reduction was possible.