However, this mix design is not appropriate when a concrete structure is exposed to the cycles of freezing and thawing in a wet environment.
In this case, the mix design should include an air-entraining admixture since entrained air will help to protect the concrete under these conditions. The Portland Cement Association publishes Design and Control of Concrete Mixtures, which contains an excellent guide to the concrete mix design.
Construction joints in a concrete structure are unavoidable. They are also a common weak point in the structure where water will often find its way in and through. Water penetrating through joints can deteriorate your structure in a variety of ways, but most notably by causing corrosion of the reinforcing steel.
Be sure to design your structure with adequate, predetermined control joint locations in order to avoid random cracking. Cracks in concrete are just unplanned joints that the concrete makes for itself.
Next, be sure that each joint employs a reliable waterproofing system of its own. A joint waterproofing system that includes crystalline technology can provide the best long-term protection at joint locations. Note that crystalline technology can also self-seal random cracking and thus provide added reliability and protection.
Even though mix designs must change to match the conditions, there is one factor that is common to all good concrete and that is low permeability. It is essential that water is kept out of your concrete structure. Lower permeability through good mix proportioning and by reducing the amount of free water in your mix using water-reducing admixtures or plasticizers. Concrete that is exposed to water should also employ a waterproofing system.
Probably the most often overlooked step in achieving durable concrete is proper curing. Curing means maintaining conditions that will allow the concrete to harden and gain strength optimally. Proper temperature and humidity are the most important. Moisture must be maintained, especially in the first few days in order to promote cement hydration and keep the concrete from drying, shrinking and cracking.
Concrete must be placed properly. The workability and consistency of the concrete mix must be sufficient to. Voids most commonly occur below or behind reinforcing steel bars — especially in areas where there are many bars together. Dedication to proper vibration practices is the key to success here. Be sure to properly vibrate all concrete with special attention around congested reinforcement. Rock pockets are areas where there is not enough cement paste and fine aggregate to close the space between large aggregate.
Make sure there is no standing water prior to concrete placement and do not move a concrete large distance from where it is initially poured.
The use of self-consolidating concrete can alleviate many of these concerns. Reinforce a concrete pour with rebar or steel mesh. Rebar is the most common addition for strengthening the pour. In vertical or horizontal projects, the more rebar present in the concrete, the stronger the finished project will be.
The standard application for installing rebar is on 2-foot centers, meaning that every 2 feet, you will place a rebar bar. Double the number of bars for greater strength. The next thing to do is to raise the level of rebar in a flat pour so the steel is in the center of the wet concrete, instead of lying at the bottom.
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Have an account? Log in Now. Join for free or log in to continue reading Remember Me! When an existing structure deteriorates, or alterations need to be made due to the form failing to serve its purpose, concrete strengthening is the best way to repair issues for long-term benefits. Reinforced concrete results when a steel reinforcement, usually a kind of steel bar, is used to increase the strength of the structure. To create reinforced concrete, building owners turn to carbon fiber strengthening of concrete and Fiber Reinforced Polymer Concentrate FRP.
Such solutions are available for use on reinforced concrete, steel, wood, and masonry load-bearing structures. However, in some cases, concrete strengthening additives are also needed to extend the life of the concrete, control setting and hardening, and fix the general structural behavior of the concrete.
Over time, a building can take quite a beating, its purpose can change, loads may increase, the local standards may evolve, or even historical structures may need more support.
In response to this, repair and strengthening of reinforced concrete structures resist these stresses that would cause regular concrete to crack and crumble. While other resources, such as building waterproofing services , can help maintain a building for the short term, concrete strengthening will become a necessity.
According to Structure Magazine , reinforced concrete will allow for the arrangements supported to have more comprehensive strength than traditional concrete, extending the long life service of the design. Using concrete strengthening , the steel supports added to larger systems will have a lower risk of erosion due to less water gradually entering the masonry work.
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