1) If mild steel is used, the working stress in it (i.e. 140 N/mm2) is more or less completely lost due to elastic deformation, creep and shrinkage of concrete. 2) The normal loss of stress in steel is generally about 100 to 240 N/mm2 and it is apparent that if this loss of stress is to be a small portion of the initial stress, the stress in steel in the initial stages must be very high, about 1200 to 2350 N/mm2. 3) These high stress ranges are possible only with the use of high strength steel. High strength concrete is necessary in prestressed concrete since the material offers high resistance in tension shear, bond and bearing. 4) In the zone of anchorages, the bearing stress being higher, high strength concrete is in variably preferred to minimize costs. 5) High strength concrete is less liable to shrinkage cracks, and has a higher modulus of elasticity and smaller ultimate creep strain resulting in smaller loss of prestress in steel. 6) The use of high strength concrete results in a reduction in the cross-sectional dimensions of prestressed concrete structural elements. With reduced dead weight of the material, larger spans become technically and economical practicable.