What can be done by a producer of ready mixed concrete to combat rapid slump loss and low strength obtained with Type K expansive cement in hot weather?
The National Ready Mixed Concrete Association has published Technical Information Letter Number 294 on this subject. The Association recommends that when concrete temperatures are above 80 degrees F the ready mixed concrete producer should either cool the concrete with ice or else transport the mix ingredients to the job before doing any mixing. In the latter procedure the cement is charged to the mixer drum in a layer over the aggregates, and the batch should be one to two cubic yards smaller than the rated capacity of the mixer. Shrinkage-compensated cement requires careful control of delivery time and truck schedules, as well as control and recording of all water that goes into the batch via the aggregate at the batch plant and at the job site. It has also been pointed out by others that admixtures, if used, should be carefully checked out ahead of time. Some admixtures that would retard Type I cement actually act as set accelerators with Type K.