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Concrete is by far, the most widely used construction material in the world today. But the use of concrete does not come without certain associated and inherent problems, such as shrinkage cracking. Concrete will normally crack, and eliminating the vast majority or these cracks is what CompCon is about. There are many different kinds or types of cracks that are associated with concrete, and CompCon is the answer to eliminating the principle cause of these cracks - shrinkage cracking. Cracks caused by subbase settlement, structural cracks, or cracking that occurs while the concrete is in a plastic state (plastic shrinkage) cannot be eliminated by including CompCon in the mix. Shrinkage Compensating concrete has over 60 years of field usage with the goal to minimize or eliminate cracking that is caused by drying shrinkage. In concrete it takes relatively little water to completely hydrate the cement, in a typical mix approximately 21 pounds of water per 100 pounds of cementitious materials used. Any additional water is strictly “water of convenience”, which means it is included solely to make the mix more workable. After the mix sets, and during hardening, this water of convenience begins to evaporate or is absorbed into the subbase, causing the concrete to shrink. If the concrete is completely unrestrained, this shrinkage will occur very slowly and may not be noticed, but concrete can never be completely unrestrained. Restraint comes from the base upon which the concrete is placed, bonding to structures that are already in place (such as walls, columns, etc.), and from the reinforcing steel that is designed into the structure itself. This restraint creates tensile stresses in the concrete, and when these stresses become greater than the tensile strength of the concrete, the result is shrinkage cracking. This is the reason that control joints are used in concrete. With CompCon the use of control joints can be decreased substantially or eliminated. When CompCon is used in the mix, there is an initial expansion due to the formation of calcium hydroxide platelets that form as the concrete is bonding to the reinforcing. This restrained expansion creates a concrete which is placed in compression thereby eliminating the tensile stresses that cause shrinkage cracking. During continued curing, as the concrete is allowed to dry, the compressive stesses in the concrete that were creaed by the CompCon are dissapated and the tendency for cracking due to drying shrinkage is greatly minimized or eliminated. As expressed in ACI-223,Guide for the Use of Shrinkage-Compensating Concrete, “ideally, a residual expansion will remain in the concrete, thereby eliminating shrinkage cracking”. This type of residual expansion can be easily achieved by adding CompCon to the concrete mix. CompCon dosage and the resulting expansion is dependent on the degree of restrain as defined in ACI 223. CompCon is not a shrinkage-reducing admixture (SRA), but rather a shrinkage compensating component. ConpCon that may be used at a lower dosage rate (approximately 3%-6%) to achieve the same results as a SRA. | What is CompCon | Chemistry | Concrete Characteristics | Facts about SCC | CompCon & Floor Slabs | Pre-Stressed | Links | | Return Home | Products | What's New | Our Services | Contact Us | |
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