During the past 35 years the strength of portland cement in the United Kingdom has increased by 75 percent. As strengths went up, cement contents dropped by 34 percent, water-cement ratios increased by over 50 percent and capillary porosity increased by 500 percent. High porosity is a direct cause of corrosion of reinforcing steel and deterioration of many structures. Professor G. Wishers of Dusseldorf reported these findings in the Holderbank News. He attributes the increase in strength to the purchasing power of ready mixed concrete producers and the implications on quality of concrete construction. Dr. Wishers has suggested that poor durability can be attributed to imbalances in the free enterprise system such as strength demands for cement that go with excessive purchasing power.
To overcome the costly problem of durability, priorities must be reordered. At the top of the list is water-cement ratio and a practical way to control it. Then in order would come cement content, curing, cover and workmanship. For salt scaling, air content would be the top priority. Strength must be removed from the top of the list, or even better forgotten.