SMALL LINE PUMPING
From an aesthetics standpoint, integrally colored concrete can add tremendous value to residential property. It can be used to beautify driveways and walkways and is especially popular around swimming pool areas. In many cases, the installation of colored concrete is accomplished by using a small-line pump system. The technology of small-line pumps has moved forward to meet the challenge of the modern ready-mix industry and the demands placed upon contractors to work around existing structures, so that high quality concrete can be placed in otherwise inaccessible areas.
Today, ready-mix suppliers make every effort to deliver a quality product to the contractor’s project, by insuring consistency of batched materials and consistent slumps when delivered. When selecting mixes to be used for pumping colored concrete, careful consideration of factors influencing timely delivery and any anticipated placing delays on the jobshould be taken into account, so that a suitable mix with the proper ingredients can be chosen. Once the mix has been selected, it should never be changed or adjusted in any way to protect color uniformity. During the batching process at the plant, consistency of mix ingredients is of the utmost importance. When adding the oxide color, it is carefully measured and mixed according to the manufacturer’s instructions and mix water is carefully monitored.
On the job, the small line pumping contractor becomes an important player, adding an intermediate link to this chain of quality. His actions can dictate the degree of success experienced by the contractor when placing colored concrete. Water should not be added to increase pumpability because it will change the water-cement ratio of the concrete and lighten the color. Due to placement variations on each job, careful consideration must be taken to insure that finishing sequence is not adversely affected by the placement practices imposed by the project. The effects of these practices will be most prevalent when a job involves more than one load, or the colored concrete is placed over a period of several days.
From the contractor’s standpoint, the urge to alter the setting time of the concrete should be avoided. Specifically, the use of calcium chloride should be avoided at all costs, as it will cause areas of dark and light contrasted color, making the concrete appear blotchy. To insure a quality job, regard colored concrete as you would high-strength concrete, giving the material the same respect and concern.
CURING AND SEALING
Quality architectural concrete adds to the beauty and value of a completed project. There are a variety of special treatments available, and one of these is colored concrete. To enhance the life and aesthetic quality of colored concrete an important final finishing technique is proper curing and sealing.
Using a curing compound in the matching color, cures, seals, hardens, and dust proofs the concrete. It will preserve the natural look and protect against stains. It also provides a means to bring a consistent look throughout the project. Clear curing compounds specific to colored concrete are also available.
Traditional methods of curing such as ponding, fogging, intermittent wetting and drying, wet coverings such as burlap, plastic sheeting, or membrane paper have proven unsatisfactory on colored concrete. Water curing in any form leaches out soluble salts from the concrete which can result in efflorescence and color lightening. Paper and plastic covers tend to leave unsightly fold marks and discolorations on the slab.
Best results are obtained when a curing compound is used on concrete during the curing process. The curing compound can be applied with a clean airless or pump sprayer. It should be applied after final trowel or broom finish when the surface moisture sheen has disappeared. Be sure to coat the surface uniformly, avoiding puddling or runoff. Most products will dry to a hard surface within two hours and can take full traffic in 72 hours. Old colored concrete can be rejuvenated with a matching colored sealer. Generally, the same application techniques are used.
This new generation of pigmented acrylic co-polymer emulsions double as membrane forming curing compounds and as penetrating sealers and provide for attractive, permanent, and maintenance-free colored concrete.