Most home owners either try to do their own concrete work or they put themselves completely in the hands of an unknown contractor whose sole recommendation is that he made the lowest bid on their job. But what can a homeowner do to help guarantee that his concrete job will provided a lifetime of trouble-free service? He should, first of all, make certain that the concrete he is receiving is a top quality mix, designed specifically for the peculiar needs of his job. To do this intelligently, he must have at least some rudimentary knowledge about concrete. Concrete is a mixture of cement, water, sand, gravel, and sometimes entrained air or other special purpose additives. Entrained air is air that is purposely introduced to a concrete mix to provide greater durability and workability. Five primary elements go into quality concrete: (1) good materials; (2) proper proportioning of these materials; (3) thorough mixing; (4) skillful placing and finishing; and (5) proper curing. Most of the ills with concrete result with adding to much water. Three absolutes should be specified in the concrete that will be used in the flatwork about your home. There should be at least 6 sacks of cement per cubic yard of concrete in severe climates where concrete will be subjected to freezing and thawing and 5 sacks per cubic yard in mild climates; coarse aggregate should have a maximum size of 1 inch in diameter; and the concrete should contain 6 percent entrained air. The homeowner, though, should always remember that concrete work involves no less specialized skills than electrical work or plumbing. And the unhappy results of a poor job are apt to be just as serious- or more so- with concrete.