| Concrete dams
Left: Hoover Dam is concrete arch-gravity structure on the Colorado River between Arizona and Nevada
copper tailings at the Sierra Gorda Mining operation in Northwestern Chile. While at the country’s Spence Copper Mine it also helped to waterproof the facility’s tailings dam, where repair and expansion of the existing tailings dam was an important part of the recent project to extend the mine’s useful life. “Unlike the more familiar hydroelectric dams, a tailings dam is designed for permanent containment; once deposited in the dam, the material stays there forever,” Domingo Lema, Managing Director of Penetron Chile, explains. “This type of long-term containment poses unique challenges to the reinforced concrete structure lining the dam.” Waterproofing the concrete had not been part of the original project specifications but this changed when numerous leaks appeared in the existing reinforced concrete structures after exposure to the aggressive tailings from the mine. To help address this, the Penetron team
recommended cleaning out and filling all existing leaks with Penecrete Mortar, a crystalline mortar used to repair cracks, form-tie holes, honeycombed areas, and structurally damaged concrete. The next step was applying a layer of a topically applied, integral crystalline waterproofing material, to waterproof the entire concrete surface of the bottom slab and perimeter slopes of the dam. Then Penetron Admix was added to the concrete mix for new construction to ensure a durable and waterproof structure from the start. The project successfully sealed 60m of cracks, the
waterproofing material was applied to almost 5000m2 of concrete surfaces, and about 10,000m3 mix was treated with Penetron Admix.
of concrete
Environmental considerations Cement can be one of the key contributors to carbon emissions within the construction industry and one way to reduce this includes the use of eco cement. Viewed as being a less environmentally damaging form, this type of concrete can be manufactured from industrial and agricultural waste, recycled aggregates, and sand substitutes like ash combined with limestone and clay.
Some of the first major documented uses of high-
www.waterpowermagazine.com | July 2023 | 39
volume fly ash concrete in the US include the Hoover Dam, where the US Bureau of Reclamation repaired a tunnel spillway in 1942, while during construction of the Hungry Horse Dam in Montana between 1948-52, just over one third of Portland cement was replaced with coal fly ash. According to Libby Snow, Vice President of independent insurance broker Lockton, from an underwriter’s point of view, the use of sustainable materials such as eco cement “is likely to introduce additional risk factors” as there can be concerns about whether more sustainable materials are as durable as traditional alternatives.
“Another challenge for underwriters is the lack of
historical data on how newer, greener materials like eco cement perform in practice,” Snow says. “This has made many insurers reluctant to provide cover but, the more such projects get built over time, the stronger insurer appetite is likely to become. A growing accumulation of claims data will hopefully allay insurer nervousness and lead to increased capacity and more attractive pricing, as competition starts to develop in the insurance market,” she adds.
Below: Waterproofing admixture was used to protect concrete structures from toxic copper tailings at the Sierra Gorda Mining operation in Northwestern Chile
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