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Color Differences in Concrete Slabs
Matching concrete color can be a tricky business. For those pouring decorative or exposed concrete, understanding the factors that influence color — and how to minimize differences — is critical.
In the ready-mix concrete industry, achieving a perfect color match between separate pours or truckloads is nearly impossible. Many variables affect concrete color, including the materials used (cement, stone, sand, and water), ambient temperature, sunlight exposure, relative humidity, moisture in the aggregates, and even the weather conditions during curing.
The aggregates — the stone and sand that make up the bulk of concrete — play a major role in determining color. The amount of dust in the stone can affect how it reacts with the Portland cement (the “glue” that binds concrete). Likewise, the color and moisture content of the sand can alter how the cement cures and, in turn, the final tone of the concrete. These are natural variables that finishers have no control over.
Aggregate: The First Influencer
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Water is the next biggest factor. Ready-mix plants typically use well water, and each well contains different mineral and iron levels. If two trucks are dispatched from different plants to the same job site, you can almost guarantee a color variation due to those differences in water chemistry. Even within the same plant, water composition can change throughout the day as wells recharge. Generally, higher iron content produces a warmer, more beige tone in the finished slab.
Water Quality and Source
Weather also plays a major role. It’s not that sunlight or temperature directly change color, but they affect the rate of curing — which does. Faster or slower curing alters how the pigments and materials settle and bond. When possible, scheduling pours on days with similar weather conditions (temperature, sunlight, humidity) helps promote a more uniform appearance between slabs.
Weather and Curing Conditions
How Site Mix Promotes Consistency
At Site Mix, we’ve built our entire operation around eliminating as many color variables as possible.
#1
Consistent Aggregate Sources
We source all of our stone and sand from a single quarry. In the ready-mix world, each plant typically pulls from the nearest or cheapest quarry, resulting in constant variability. Our one-source approach ensures uniform aggregate color and composition across every load.
#2
Single Supplier for Cement and Admixtures
We use Type 1L Portland cement exclusively from one trusted supplier, and we never switch vendors based on price fluctuations. The same goes for our admixtures and air-entrainment products — all are sourced from one manufacturer in bulk quantities. That consistency in materials means consistency in color.
#3
Superior Water Quality
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Most importantly, we are the only concrete manufacturer in Central Ohio using City of Columbus water. While it costs a bit more, it’s exceptionally clean and low in minerals and metals. This stable, high-quality water supply allows us to maintain the most consistent concrete mix possible.
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Traditional ready-mix companies can’t replicate our level of consistency. Their business model relies on multiple fixed plants across Central Ohio, each sourcing stone, sand, and water locally — often from different wells with different mineral compositions.
In contrast, Site Mix operates a volumetric mixing model. All materials are stored and loaded from one central location, and the concrete is mixed on-site, not in transit. Because the concrete isn’t made until the truck arrives at the job site, travel time has no effect — and centralized sourcing ensures every load meets the same high standard for quality and color consistency.
Water Quality and Source
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