When the weather gets hot, low concrete test-cylinder breaks are more likely. These low breaks can slow job progress by delaying acceptance of the concrete until further testing confirms adequate strength. Too often, though, low strength-test results occur due to improper concrete-cylinder storage and curing at the jobsite during the critical first 2 days after the cylinders are made. Although test-lab personnel usually make and test the cylinders, the contractor often is responsible for safe storage and proper initial curing of cylinders at the jobsite.