Some contractors don't see the need for a close relationship with ready mix producers. They shop for the lowest prices, place the order, install the work, and move on to the next job. The next producer is also selected by price so the job may be served by another company.
Other contractors see their ready mix producer as a partner—one they work with every day. Their goal is to build on the relationship and the trust. This is the kind of contractor on which Cemstone Products, Mendota Heights, Minn., focuses.
Several years ago Cemstone recognized the growth of decorative concrete and set a company goal of developing that market. But it knew that there are factors that make decorative concrete more difficult than plain concrete, such as:
- You must maintain the same color with integrally colored concrete load after load, and that increases the level of risk for both producers and contractors.
- The contractor's customers are more sensitive to durability issues with decorative flatwork; they might forgive some scaling and spalling on plain concrete surfaces but not on colored, imprinted, or chemically stained finishes.
- Customers are less tolerant of cracks—a crack going through a brick pattern, for instance, betrays the fact that it is concrete and not real brick.
- For the increased cost of a decorative concrete project, customers expect a more perfect finish without worker error.
- And for the producer, afterwards there is the need to wash all the color residue from the trucks that have delivered colored concrete.
Cemstone first embarked on a program to improve its quality control and service to customers. This included adding liquid color dispensers in its plants. Today eight of its plants use liquid-dispensed integrally colored concrete. It also found ways to ensure that the water-cement (w/c) ratio didn't change from load to load. This is critical for integrally colored concrete since changes in the w/c can result in shifts in the color appearance of the finished concrete. Cemstone's marketing efforts and quality control refinements have paid off. Dave Pace, Cemstone's vice president for sales, says that two years ago its goal was to provide 20,000 cubic yards of colored concrete. In 2005, its goal is 60,000 cubic yards. To accomplish this it recently hired an engineer to promote colored concrete finishes to municipalities for crosswalks, medians, walkways, and streetscapes.
The Wal-Mart Corporation recently included an option for colored concrete in its floor specifications. Cemstone is working to ensure that stores constructed in the Twin City area include, and adopt, that option.
To help ensure customer satisfaction with decorative concrete, Cemstone made a substantial commitment to training and education for contractors, architects, engineers, owners, and government code officials. Its goal is to improve the installed durability of concrete, help contractors learn more about working with decorative concrete, provide designers with model specifications and the latest trends, and raise the minimum standards for concrete in building codes—especially residential.
Training is the heart of Cemstone's program for contractors. Pace says it offers beginning and advanced classes on concrete basics and decorative techniques. Its two-day seminars cover both theory and hands-on training throughout the year. There are never more than 30 people in a seminar, and the fee is $150, just enough to cover basic costs. He adds that the next five classes are full. Training opportunities include:
- ACI finisher certification classes
- Placing and finishing with dust-on color hardeners and integral color
- Concrete basics
- Stamping and stenciling
- Chemical staining
- Overlay cement decorative finishes
Contractors and ready mix producers both want durability. One way Cemstone promotes durability and good concrete practices is by circulating architectural concrete guidelines to specifiers, contractors, and owners, encouraging them to install concrete to high standards. The guideline document is two pages long. Some of the more critical items include:
- Concrete should be placed with a w/c ratio less than 0.45. If the slump must be adjusted for ease of placement on the jobsite, Cemstone recommends that it be accomplished by adding superplastizers on the jobsite instead of water.
- The strength requirement for exterior concrete should be 4500 psi at 28 days. And the strength should be at least 4000 psi prior to concrete being exposed to freeze/thaw cycles; in Minnesota that can be as early as October 6.
- Air entrainment is perhaps the most critical parameter to guarantee durability—and one of the most difficult to control because of the wide range of factors that influence it. Cemstone's guideline is 5% to 8% at the point of placement. If placement takes longer than one hour from the time of batching, contractors should measure the air content and adjust it if necessary. But total placement should not exceed 1½ hours. When snow-melting heating elements are included in a slab, every load of concrete must be checked for air content to avoid possible removal and replacement because of improper entrainment. Cemstone will provide this service to contractors if an outside testing service isn't contracted to provide testing for a project.
- Both the water content of a mix and the placement slump must be controlled from one load to the next to achieve the most consistent results when installing integral colored finishes. The placement slump shouldn't exceed 5 inches. The ready mix producer and the contractor must work together to achieve this consistency among loads of concrete.
- Achieving durable concrete is the result of using good mix designs, proper placement procedures, and good curing. Decorative slabs must be cured with products compatible with the decorative treatment. Cemstone recommends that a final sealer be used and maintained over time. But the sealers must be compatible with the curing agents used.
Developing mix designs
Contractors must have durable concrete mixes with good finishing characteristics. One concrete mix doesn't serve all needs. Different mixes can help as weather conditions go from cold to warm, and different decorative finishes can require different concrete mixes for the best installation. Designing the ideal mix is a task that few contractors can accomplish alone. A good ready mix producer has the expertise to design the best mix for a given situation and can help contractors monitor the workability over time and make the necessary changes.
Keeping up with change
Today's concrete is a rapidly changing technology; it's difficult for contractors to keep up with the latest methods and materials. Companies like Cemstone can be an ally in this effort. Its construction supply business carries a full line of the latest decorative tools and products as well as other concrete-related materials and equipment. Pace says that contractors who buy Cemstone's concrete can also access the “my Cemstone” link on its Web site to watch their concrete placement on a job-site in real time. The day after placement, they can access their invoices on the Web.
The decorative concrete industry has more training opportunities today than any other segment of the industry (see list of training opportunities on p. 28). Contractors and workers need a good understanding of concrete basics, but that's only the first step. Learning how to work with color and other decorative techniques and manage the problems that can develop requires additional knowledge and understanding. Selecting good business partners, such as a good concrete producer, is critical to success.