The specialized high-performance grouts of today are entirely different materials from the common cement-sand grouts many constructors have used in years past. The grouts are called upon to deliver performance standards that would be unattainable with the cement-sand grouts. A list of some of the jobs and materials that call for use of these specialized, high-performance grouts are supporting major equipment, setting load-bearing columns, anchor bolts, construction joints, post-tensioned cables, and caulking. Specialized grouting can be accomplished by techniques such as dry packing, pouring, and pumping. Pouring is the ideal technique to use for most applications if the chosen grout will perform as required after hardening despite being put into place at a flowable consistency. Dry-packing is a technique that has long been used in jobs requiring high-performance grouting. The technique was first employed to minimize shrinkage of plain grouts by keeping their water content as low as possible. Pumping of specialized grouts is being done on some difficult jobs. It may be necessary where there is limited access to the space to be filled or where the grout must travel a considerable distance to the site of use. The water and cement content for a plastic or flowable consistency of ordinary cement-sand grout is so high that shrinkage and cracking render it unusable for any grouting application that is even mildly demanding. New gas-forming grouts appear on the market from time to time. Characteristically they contain a finely grouted material which reacts with water or some other constituents of cement to produce gas. Metallic aggregate grouts are of two basic types: those that contain an iron aggregate and an oxidation catalyst that causes the iron aggregate to enlarge by a controlled amount and those that contain iron aggregate but have no catalyst. Highly specialized grouting materials have been developed that hold to a safe minimum all components such as sulfides and chlorides for use with cables, bolts, rods or anchors which are stressed above 80,000 psi.