February 15, 2013
Shotcrete Waterproofing – A Global Solution
PENETRON technology, in conjunction with the use of “designer mixes” and customized installation by specialists, is opening a new frontier for key waterproofing applications.
Concrete impermeability and durability – for sprayed concrete, gunite or shotcrete – have been important performance enhancements for special materials manufacturers and applicator companies who are always on the lookout for waterproof and durable structural linings for many types of containment in underground or hydraulic environments.
Because it is able to penetrate the entire thickness of a concrete structure, PENETRON ADMIX Enhanced Shotcrete (PAES) is a key ingredient to waterproof the shotcrete matrix. It reacts with water and the various mineral compounds present in the mixes to form an insoluble, thread-like calcium silicate hydrate (CSH) crystalline structure that seals pores, capillaries and cracks. The “self-repair” behavior of PAES remains active over time, responding to any moisture and/or water present in underground structures and in hydraulic constructions to ensure a watertight matrix.
Thanks to this exclusive – and highly effective – formula of reactive hydrophilic components, PENETRON ADMIX Enhanced Shotcrete (PAES) drastically reduces shotcrete permeability and cracking due to thermal stress and the effects of freeze/thaw cycles. This increases the performance characteristics of the matrix right from the start during concrete spraying. It remains active over time and speeds up the installation operations by ensuring durability of the containment construction.
There are many important application types: structural shotcrete or shotcrete for renewal of tunnels, underground passages, hydraulic conduits, dams and open canals. This also includes shotcrete used in underground support constructions, such as diaphragms, piling and micro-piles.
Tunnels & Parking Garages in Italy
Based on the results of projects in the USA, Scandinavia, South America and the Middle East, several trials were carried out in Italy, which led to further, significant projects. Enrico-Maria Gastaldo Brac, Managing Director of PENETRON Italia, explains, “The PENETRON System is a revolutionary technology for internal-capillary waterproofing and enhancing the durability of concrete. It has gained an engineering following in Italy, thanks to its successful use in key projects such as the Mittewald Tunnel in Bressanone in Northern Italy.”
The Mittewald Tunnel was restored through hydro-sandblasting to remove a 10-15cm layer of deteriorated concrete, followed by the installation of a new drainage system for the construction joints to protect the tunnel cap from hydrostatic pressure. The sandblasted layer was restored with PENETRON ADMIX Enhanced Shotcrete (PAES), which completely stopped water penetration and facilitated the water flow into the new drainage system.
PENETRON Italia also completed several important construction projects in Rome by perfecting the mixes and application methods:
- Piazza Cavour
- Via di Donna Olimpia (effects of crystallization over time)
- Cassia-Monte Mario tunnel
- Underground car parks Viale Oceano Pacifico & Via Delle Medaglie D’Oro
More Tunnels in Sweden
Rail transportation is a high priority in Sweden and enabling high-speed railway traffic has necessitated upgrades for various tunnels in the Bothnia Line and the historic Ådals Railway, both located north of Stockholm along the Baltic Sea coast. Project specifications for the 45km (28 miles) of tunnels were extremely stringent, with zero pollution and ground water contamination allowed. For many locations, a PVC membrane to line the tunnel walls was not feasible due to a lack of space. A special PENETRON ADMIX Enhanced Shotcrete (PAES) was developed and the results were carefully evaluated. The application was a comprehensive success; even previously severely leaking construction joints remained completely dry.
Both the Frösvi and Ullbro highway tunnels on Route 18 (E18) outside of Stockholm were also successfully waterproofed. The PENETRON ADMIX Enhanced Shotcrete (PAES) was applied in a one spray wet shotcrete lining process, with a layer thickness of 150mm.
Fighting Back the Ocean in Australia
Severe water leaks in the existing shotcrete and concrete of the Miami One Shopping Centre required a high-performance waterproofing product to ensure that the two-level basement would remain dry. Because a less effective admixture was used, PENETRON ADMIX Enhanced Shotcrete (PAES) was applied to waterproof over 2000m3 of concrete and 600m3 of shotcrete; these structures were located only 150m from the beach. After treatment, all leaks stopped and the elevator pits, base slabs and shotcreted retaining walls remained dry.
Tanks, Tunnels & Highways
Numerous projects across the USA also confirmed the effectiveness of PENETRON ADMIX Enhanced Shotcrete (PAES) to enhance the durability of a shotcrete matrix for above-ground and below-ground structures. For example, the City of Harrisonburg, Virginia, decided to treat the new Grandview water tanks (a main eight million gallon tank, another five million gallon tank and a smaller 600,000 gallon tank) with the PAES system in a shotcrete process. This provided the concrete with very low permeability characteristics and the corrosion protection needed for the pre-stressed cables and rebar used in the pre-stressed tank construction.
Originally designed for rail transportation, the 110-year old National Bikeway pedestrian and bikeway tunnel was plagued by poor drainage and a damaged lining. This impeded traffic with dangerous water leakage and ice accumulation. A PENETRON ADMIX Enhanced Shotcrete (PAES) mix was applied to the existing structure and to the new reinforced tunnel lining to eliminate all leakage.
Acid mine drainage was a problem with the construction of the Gateway highway connector in Fairmont, West Virginia. The West Virginia Division of Highways designed a PAES mix and pneumatically applied it to all underground drainage structures to protect from chemical attack and corrosion.
Christopher Chen, Director of The PENETRON Group, summarizes: “For a multitude of shotcrete applications, the PENETRON ADMIX Enhanced Shotcrete (PAES) system provides design teams with a reliable and successful solution. PAES not only enables a thinner application and, often, elimination of traditional waterproofing channels and liners, it also helps save money on material costs and accelerates the project schedule. One of the biggest benefits of the PAES system is the support we offer to tailor the system to each individual project, ensuring the highest level of success.”