It is common for the contractor to request a slump increase at the jobsite. Concrete with higher slump is easier to pour, pump, and finish.
The best time to request this higher slump is during ordering. This saves time for adjustment at the jobsite and allows the ready mix concrete producer to select the most suitable mix design for the higher slump. However, contractors make the request at the jobsite for a variety of reasons.
Without Verifi, the increase in slump at the jobsite is usually made by adding water. The addition of water reduces strength and durability and delays setting time.
Verifi enables concrete producers to increase slump by adding superplasticizer, which does not negatively affect strength and durability.
In today’s Load of the Week, the original order was for a 5-inch slump. At the jobsite, the contractor requested a slump increase to 7 inches. The driver entered this new slump target on the Verifi in-cab interface. Verifi then automatically added superplasticizer to reach the new 7-inch target slump.
As a rule of thumb, a 2-inch slump increase with water would have decreased the compressive strength by about 400 psi and delayed setting time 20 to 30 minutes. This effect was avoided by the use of superplasticizer to increase slump.
[LP = leave plant, AS = arrive site, BP = begin pour, LS = leave site, RP = return plant]
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