RAPIDFORCE(tm) High-Early Concrete is a ready mix concrete that offers unparalleled flexibility to rotate forms. This is the perfect solution for fast-track construction and repairs. It also has ultra-rapid setting properties, allowing for faster placement and turnaround.
A USPS Network Distribution Center in Capitol Heights, Maryland, needed new concrete pads quickly. It needed 120,000 cubic yards of concrete, placed in a 24-hour pour schedule. A new skybridge and parking garage were to be constructed, along with a 75-bed neonatal intensive care center. The building required an advanced concrete that could withstand the cold weather.
Holcim was tasked with designing a custom RAPIDFORCE concrete mix. The mix was formulated to provide a 5,000-psi compressive strength within 24 hours. In addition to achieving a high early strength, the mix had to meet pumpability requirements.
In order to achieve the early strength development, the mix was accelerated with a chemical admixture. Calcium chloride was used, which increased the rate of hydration of the concrete. The addition of pozzulanic admixtures, such as metakaolin, also contributed.
The project required the use of a captive batching plant. The mix was also made with superplasticizers for pumpability. The density of the mix was also adjusted. It was also pumped with high pressure, low-output pumps. The output was affected by the weather conditions.
The 5,000 Plus concrete mix was 20% stronger than standard concrete. It also included dense aggregate for strength. Unlike ordinary concrete, it is smoother under the trowel.