CONCRETE PIPE Testing and Quality Control Core Strength Test The core strength test is used to determine the compressive strength of cores cut from the pipe or cured cylinders obtained from concrete mix samples. The core specimen should have a diameter of at least three times the maximum size of coarse aggregate used in the concrete, and a length to diameter ratio between one and two after the curved end surfaces have been removed. The core specimen is moisture conditioned by submergence in limesaturated water before testing, unless otherwise directed by the purchaser. In addition to core strength tests, there are other daily checks conducted for precast concrete products. For example, with concrete pipe, each piece is tested using a “Go/No-Go Gauge”, which measures the dimensional tolerance of the bell and spigot connections. Hydrostatic Test The hydrostatic test is performed on a full section of pipe or two or more sections of pipe assembled with a joint gasket. The equipment for this test includes bulkheads for the pipe ends, means to secure the bulkheads, and a method to introduce and maintain internal water pressure. For a single pipe section test, the bulkhead arrangement determines whether the pipe barrel or both the barrel and joint are tested. Two or more pipe sections joined and tested provide a realistic test of the joint-gasket combination. Included are requirements for testing pipe sections in straight or deflected alignment. The exact wording on allowable leakage varies among pipe specifications but damp or wet spots and minor dripping are generally not considered leakage. Specifications typically allow presoaking before testing, or extended soaking before retesting. Every precast concrete product manufactured at Lafarge undergoes a pre and post pour inspection. Each piece that passes inspection and is made available for sale must be stamped with the letter “P” denoting its adherence to the Plant Prequalification Program as discussed in the following section. PAGE 22 LAFARGE PIPE eMANUAL