The requirements for post tensioning grouts vary with the job. Standards should be set for each job and test performed to be sure the grout meets the standards. The pumpability of grout should be measured on the site as a method of control. The recommended test procedure is to measure the amount of time (efflux time) that is required for a sample of grout to run out of a flow cone after the plug is pulled. This time of efflux of the grout, in seconds, is also called the "flow factor". The flow cone and test procedure should conform to US Corps of Engineers Test Method CRD-C79. The mixer for grout should be a high-speed mechanical mixer. The use of conventional concrete or mortar mixers or hand mixing should not be permitted. Uniform grout, free of lumps and undispersed cement, can be obtained only be mixers which produce shearing action. This may be accomplished by paddles, discs, or drums running at high speed in either a vertical or horizontal position. Horizontal shaft mixers, similar to large scale plaster mixers, may still be used although mixing is somewhat less effective. The pan or turbine conventional concrete mixers are well suited for mixing grout, although maintenance of a sufficiently tight seal of the discharge gate can present problems. The grouting equipment should contain a mechanical device which can be set to limit the pumping pressure to any desired value up to 150 psi gage or adjusted to allow the grout to be bypassed at the pressure desired. Because pumping pressures higher than 150 psi gauge tend to cause leaks or to accentuate existing leaks in the seals, connections, tubing and end anchorages, such pressures should be avoided.