Here are the Top 3 issues that you should keep in mind when selecting a block color:
1. The color of a given concrete block is like a "visual summary" of all of the block's mix design ingredients and is further influenced by the face texture, moisture content, exposure to dust and dirt, as well as how the block has been cured during the manufacturing process, thus, as with all natural materials, there will be a slight color variation in every production run of concrete masonry units,
2. Block color can vary between manufacturing runs, based on slight differences in climate and source materials, thus, it is highly recommended that for projects where consistency of color is important, you should indicate in your contract documents that "All Concrete Masonry Units Shall Be Run At One Time For This Project". Note: this is particularly important when ordering Base Color CMU, since it can otherwise be sourced from in-stock material from various sources, each of which would likely have been made at varying times, resulting in unpredictable color variation.
3. Block colors are REGIONAL and are tied to locally available aggregates and materials. Before selecting colors for a project, ask yourself: "Where is my project located?" If your office is in San Francisco, but your project is in Reno, NV, then you want to select colors from the Reno, NV region. Don't wait until the bidding stage of a project to determine the right product for your project.
The most basic color of block, commonly called “grey block”, is a natural grey, concrete mix design, with no other colored aggregates or iron oxide color added. In addition to grey block, colored aggregates and various colors of iron oxide can be added to the mix. The second most common color of block is “tan block”, which results from adding iron oxide to the basic grey block mix design. "Base Colors" are typically available in Lightweight, Medium Weight, and Normal Weight mix designs.
The majority of the colors available for CMU are considered to be “Standard Colors”. And among the standard color options, there are hundreds of possible combinations of aggregate colors and iron oxide pigment colors available, again, available in LW, MW and NW mix designs..
Some of the more specialized color options include those containing either a “white cement” or "block cement" (rather than the normal grey cement), and/or those including a specialty aggregate, (such as dolomite), and/or those using a rarer color of iron oxide pigment (blues and lavenders, for instance, can be more expensive than most other iron oxide pigments).
It is important to note that the cost of the concrete masonry unit itself is just a small percentage of the overall cost of the installed masonry wall system, (which typically includes the CMU + footing + rebar + mortar + grout + transportation + labor).
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