Tips About the Concrete

  • What is Concrete?

     

    Concrete is made up of three basic components: cement, water, and aggregate (sand, gravel, rock) in varying proportions.

     

    Cement acts as a primary binder to join the aggregate into a solid mass.

     

    Water is needed to chemically react with the cement (hydration) so the mixture solidifies.

     

    Note that cement is a component and, contrary to popular belief, not the same material. To define it more simply: when cement is mixed with the other ingredients, the cement and water form a paste that glues the aggregates into a rock-solid mass called concrete.

     

    Varying the proportions of the water and cement is known as the water/cement ratio. The lower the w/c ratio, the stronger the concrete (and the less porous). Changing the proportions allows it to have varying strength, density, and thermal resistance so that it works for the intended job.

     

    Types of Concrete

     

    Ready-mix is manufactured in a factory or batching plant, according to a set recipe, and then delivered to the work site. This results in a precise mixture and also allows for specialty mixes to be developed. But it also means less flexibility and a shorter shelf life.

     

    An alternative for the ready-mixed concrete is the use of mobile mixer concrete trucks which carry all of the ingredients to produce it in separate compartments. Once at the job site, the ingredients are measured, through calibrated controls, into the mixing device which ultimately produces the concrete. This results not only in the correct mixture but also the correct amount, eliminating waste.

     

    Reinforced concrete is imbedded with metal, usually steel. It can carry enormous loads and has great versatility in large construction projects including bridges, and arches.

     

    Signs of Concrete Damage

     

    Curling or warping around edges and at corners are signs of concrete damage. Temperature causes curling; moisture causes warping. Blistering can occur when surface mortar separates from concrete. In addition, low spots in concrete will cause water to pool if no drainage exists.

     

    Surface cracks are an obvious sign of damage to concrete. Some may appear as secondary symptoms of other defects, and can be difficult to diagnose correctly. Fine random cracks or fissures may be seen when the concrete is drying after being moistened. Cracking that occurs in a three-point pattern is generally caused by drying shrinkage. Large pattern cracking, called map-cracking, can be caused by an alkaline-silica reaction within the concrete.

     

    The surface of concrete can disintegrate as well, evidenced by broken pieces, a dusty formation on the surface, and mortar flaking and scaling. Other defects include discoloration and small or large voids in the vertical placement of concrete.

     

    Concrete repair and replacement are jobs for specialized contractors. Although it can last thousands of years, concrete needs to be cared for to achieve the best results.