March 27, 2017
PENETRON Keeps Sludge out of the Concrete at Patapsco
At Baltimore’s Patapsco facility, one of the largest wastewater treatment plants in the U.S.A., PENETRON crystalline technology was applied to the entire biologically activated filter (BAF) system. The project was completed in February 2017, ensuring crucial concrete durability and resistance to chemical attack.
Concrete structures in wastewater treatment plants are exposed to various chemicals, such as chlorides, sulfates and acids that use water as a way to enter the concrete. This acid attack can potentially cause dissolution of the concrete matrix and a subsequent loss of structural integrity. PENETRON ADMIX provides the 70% or more permeability reduction as per ACI guidelines for permeability-reducing admixtures for hydrostatic conditions (PRAH). The admixture also protects against chemical attack (pH 3- 11) and is a widely-used solution for wastewater treatment plants.
In order to meet the Patapsco project’s performance criteria above and beyond the ACI 350 standard, the design mix prepared by Vulcan Materials was optimized for durability to minimize shrinkage and to self-heal cracks in the concrete. PENETRON ADMIX and a shrinkage-reducing admixture from Grace Construction Products (GCP) were used to minimize shrinkage and seal micro-cracks. Easily mixed in during batching and unaffected by climatic conditions, PENETRON ADMIX was used to treat about 23,000 cubic yards (17,600 m3) of concrete. The admixture helped meet extremely stringent concrete shrinkage length limits of 0.028% or less (7 days) and 0.035% or less (at 28 days), using a modified ASTM C157 testing procedure to measure expansion and gross shrinkage.
The construction project included advanced BAF filter systems (and related work) to enhance the nutrient removal capabilities of the Patapsco Wastewater Treatment Plant. The project was comprised of two phases. The first phase, which did not include PENETRON ADMIX, suffered from a series of major leaks. For Phase Two, PENETRON ADMIX was successfully employed to eliminate leakage and seal micro-cracks, avoiding a repeat of the issues encountered in Phase One.
Following the difficulties encountered with the Phase One, the engineer working on the second tank employed a design approach that exceeded the ACI 350 standard by proactively minimizing slab-restrained shrinkage cracking and ensuring that the small cracks were sealed with PENETRON’s crystalline technology. This solution ensured that the above-ground tank would be leak-free.
“The ready mix supplier was able to meet these shrinkage performance criteria by combining blended cementitious materials, optimized aggregate, PENETRON ADMIX and a shrinkage-reducing admixture, all at the most economical cost,” explains Jeremy Swartzfager. “The client was very pleased with the results.”