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Returned concrete is an operational nightmare for ready-mixed concrete producers. Each year, drum mixers return anywhere from 3% to 5% of the freshly batched concrete to the plant for disposal. Producers can use several recycling techniques to process these yards, including tempering and reselling. But the most common approach is to simply let the mix harden in containment areas then scoop it up, crush it, and size it into granular fill.
This entire process requires hard to find plant space, can be labor intensive, and is expensive and potentially dangerous. One operational challenge is mucking a pile of hardened concrete with variable set times. From changes in mix design to differing maturities, the inconsistency is maddening. There have even been occasions where producers have waited too long, requiring concrete breakers and blasting crews to break up the hardened concrete.
With these operational issues, producers were encouraged to learn of a new product that can take some of the variability out of reclaiming returned concrete. Scientists from Master Builders Solution recently unveiled their MasterSuna RCT 323 admixture. This single-component, powdered polymer gels the fresh concrete resulting in rapid stiffening and minimizes cement hydration and strength development. When used in most mixes, the material stiffens to a loose consistency in less than 5 minutes
Treating the returned concrete with this new admixture is easy. MasterSuna RCT 323 is packaged in water-soluble bags sized for easy dosage rates that are matched to the volume of returned material. After placing the admixture into the mixer’s drum, the driver rotates the drum for about 200 revolutions ensuring thorough dosing then discharges the treated material in the disposal area. The rapid stiffening helps minimize excess water from spreading from the pile.
The treated product has the consistency of a low controlled-strength product. It is easily scooped up by a front-end loader for use as a granular fill or even as aggregate in concrete.
While the admixture is designed for ready-mixed concrete producers, precasters and contractors may want to consider adding this new concrete treatment to their operational toolbox. Many precasters order concrete from ready-mix plants, so over-orders could be left at their plants allowing them to avoid disposal charges. Concrete contractors are often required to provide waste concrete pits or disposal containers on large job sites. MasterSuna RCT 323 could help make these areas smaller and cleaner.
MasterSuna RCT 323 was introduced to be a part of a producer’s total recycling plan that addresses the need for sustainability and reduces their carbon footprint. Engineers and product specialists from Master Builders Solutions have recorded a webinar outlining how producers can benefit from taking a new look at their returned concrete reclaiming operations.
To learn more about MasterSuna RCT 323, visit the product web page.