Good concrete requires some basic preparation before it can even begin to be built. The first prerequisite for good concrete is that a concrete type suited for the job at hand must be found and have a satisfactory source of coarse aggregate, fine aggregate, and water. All other things being equal, then the combination of the best mixed, strongest, and cleanest concrete makes the most durable and strongest concrete available. The right concrete supplies are what make the project successful.
As concrete sets, heat and weathering begin to take their toll on the materials, especially with steel where the most damage occurs. Without repair or preventive measures, both initial construction and rework will degrade the underlying good concrete. In general, when concrete is poorly prepared before work begins its composition weakens and becomes more subject to external forces such as wind and water that weaken the aggregates and increase the amount of friction as well. The best, most durable concrete begins life as a mixture of these three key aggregates with trace amounts of water. When this basic composition is combined with proper tools and techniques, the result is much stronger concrete that will stand the test of time and weathering.
A good concrete should begin life with a specific ratio of useful ingredient to total aggregate; however, this basic formula has little meaning for concrete that is going to be poured outside. To achieve good durability with these aggregates, the overall ratio of ingredients needs to be determined before the mixing begins. This allows a skilled craftsman to mix the concrete to the exact specifications needed for each particular job. The mixing of the concrete requires a strict adherence to the ratio requirement to prevent undesirable results. Each part of the mixture is equally important to the strength and durability of the finished structure. These include;
Other important components to a good concrete mixture are voids and reinforcing elements. Aggregates in the mixture must be tightly packed into voids, while allowing air pockets and void areas to form and expand within the concrete. If these gaps and voids are not properly filled in enough, an expansion in the concrete occurs. If the expansion is not properly controlled, it can weaken the structure over time and lead to cracking, buckling, or crumbling. Reinforcement also plays an important role in the strength and durability of a concrete surface.
While some flexibility is allowed in the concrete mix during the mixing process, once poured the concrete must have a firm, consistent, and reliable initial state. A good concrete must have a minimum of 0.Mr% shrinkage and should never shrink below the specified rate during the curing process. Shrinkage creates cracks in the surface of the concrete, which, when left alone, can spread and become larger with time. It is important for the workers to remain within the recommended shrinkage range during the mixing, processing, finishing, and installation of concrete. While the ideal shrinkage is somewhere around one percent, anything greater than that will increase the overall difficulty of the project and make it more difficult to perform the final finishing touches.
The final, second requirement of good concrete is that it must have a fine sand, fine aggregate, and water content that are at least two percent. Sand is the most important ingredient in good concrete because it allows for proper compaction and separation of the materials during the manufacturing process. Sand should also be very fine or too fine will make the final product weak and brittle. Aggregates such as fine aggregate are key ingredients in the construction of any good concrete because these tiny particles are the ones that make the mix become stronger. Water is another component of good concrete, but it is not necessary to use much water and often is not even included in the mixes because the mixing process does a good enough job of homogenizing the materials.