By Debbie Sniderman
Speed Fab-Crete produces large colored MSE panels at its advanced precast concrete plant in Kennedale, Texas. Carl Hall, one of the owners, said that there are many things that affect color. His advice for consistent color: “Do the same thing every time.” Even changing one thing affects the color. If the mold cycle time is 16 hours then every piece is stripped from its mold as close to 16 hours as possible. The aperture, the mold surface, how long its been cured, the delivery system of the concrete from the mixer to the mold must all stay the same, he said. Hall described how Speed Fab-Crete met the challenges of consistent color for one long-term project providing MSE panels for TxDOT.
Speed Fab-Crete has three mixers, Hall said, but they used the same mixer for the entire project. With consistency and accuracy in mind several hundred pounds of dye was hand-weighed every day. They used the same materials for the entire project.
The production team tried to schedule pouring and stripping from the mold at the same time every day. After the cast pieces were stripped from their molds they were placed in a racking system facing each panel to the south. A third party performed a photospectrometer color measurement check on each panel before the panel was approved for shipping. This process step was a directive from the client. Speed Fab-Crete learned it had to adjust the amount of dye as the seasons changed. Batch designs developed for the summer months yielded different color in the winter.
Another requirement that complicated the project was a specification that fly ash had to be used as an additive in the concrete to meet TxDot requirements. Hall’s team had no control over the color of the fly ash, which meant additional testing to ensue color uniformity.
Hall said they found that different form liner textures make a big difference in the color, even after sandblasting the surface. Form liners with rough surfaces produced panels that reflected the light differently from those with smooth surfaces. In the end it took Speed Fab-Crete a lot of trial and error to get the desired color.