Q.: Concrete is sticking to the forms of our stringline curb forming machine and peeling off the newly formed curb as the machine moves on. Temperatures have been very warm, rising to about 90 to 95 degrees F in midafternoon. What causes this problem, and what can we do about it?
A.: It's quite likely you have too much fine aggregate in the concrete mix. Try replacing some of it with coarse aggregate. Start by using 100 pounds more coarse aggregate and 100 pounds less sand and then adjust further as needed. Anything you can do to keep the concrete cool during mixing, transporting and placing is also likely to help.