RheoTEC Z-60: The Value for the Precast/Prestressed Producer  

The Challenge

Precast/Prestressed concrete producers want the efficiency of an easy to place and consolidate concrete mixture while achieving high early compressive strength. If dosed too high, the use of a retarding admixture to extend workability retention time may result in retarded or delayed compressive strength development. However, if the dosage is reduced so as not to effect the compressive strength development, then insufficient workability retention may occur, and a less- than-optimal placeability and final surface finish may result.

How does workability retention with RheoTEC™ Z-60 improve production efficiency and enhance profitability?

By maintaining concrete workability without retardation and thereby achieving higher early compressive strength, the precast producer can significantly optimize mixture cost. At the same time, the use of RheoTEC Z-60 results in fewer surface quality issues, such as pour lines or bugholes resulting from premature concrete stiffening. Finally, the producer can adjust the dosage of RheoTEC Z-60 to compensate for changes in project requirements, materials, temperatures and other variables which can shorten slump life and impact placement time and production efficiency.

The table below provides an example of the benefits of using RheoTEC Z-60 in precast production. This example presents two identical SCC mixtures, one using a retarding admixture for workability retention and the other using RheoTEC Z-60 admixture. Slump flow retention data over 45 minutes as well as 4, 6 and 8 hour compressive strengths both with and without heat curing are presented. The slump flow retention of the RheoTEC Z-60 treated mixture is somewhat improved over the retarding admixture treated concrete, however, the more important point is the 8-hour non-heated compressive strength for the RheoTEC Z-60 treated mixture achieved 1000 psi greater compressive strength than the retarding admixture treated concrete of the same age and curing regimen. Additionally, when heated, the RheoTEC Z-60 treated mixture achieved the same compressive strength in 6 hours as the retarding admixture treated concrete did in 8 hours. The use of RheoTEC Z-60 in precast production can lead to the optimization of concrete mixture proportions and/or earlier stripping times, resulting in energy savings.