{{unreferenced, date=December 2013 Rhoca-Gil is a type of industrial

sealant Sealant is a substance used to block the passage of fluids through openings in materials, a type of mechanical seal. In building construction ''sealant'' is sometimes synonymous with '' caulking'' and also serve the purposes of blocking dust, so ...

produced by

Rhône-Poulenc Rhône-Poulenc () was a French chemical and pharmaceutical company founded in 1928. In 1999 it merged with Hoechst AG to form Aventis. As of 2015, the pharmaceutical operations of Rhône-Poulenc are part of Sanofi and the chemicals divisions a ...

, used in the construction of tunnels to block the passage of

groundwater Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated ...

into the tunnel. The sealant begins as a liquid, is then injected into cavities which need to be sealed, and polymerises, causing it to harden.

Process

Rhoca-Gil consists of two fluids, that are mixed, thinned out with water and then sprayed into cracks in the bedrock. One of the fluids contains

acrylamide Acrylamide (or acrylic amide) is an organic compound with the chemical formula CH2=CHC(O)NH2. It is a white odorless solid, soluble in water and several organic solvents. From the chemistry perspective, acrylamide is a vinyl-substituted primary ...

and methylolacrylamide. The mixed solution becomes a viscous fluid that penetrates cracks and holes in the rock, where the fluid reacts— polymerizes—to a tight plastic substance. When it is completely polymerized it is stable and will not exhaust any toxic compounds.

Controversies

In 1992 construction of the Hallandsås tunnel in Sweden began, with opening plans for 1995. Groundwater leaking into the tunnel was however a major problem, slowing the progress, and Rhoca-Gil was used. In 1997, fish and local cattle started dying as a result of Rhoca-Gil in its liquid form leaking into the water supply, contaminating it with acrylamide, a known

carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive subs ...

and mutagen. Furthermore, the contamination of the area led to a ban on agricultural products from the area, as well as a ban on using water from the area affecting local residents. The main contractor,

Skanska Skanska AB () is a multinational construction and development company based in Sweden. Skanska is the fifth-largest construction company in the world according to ''Construction Global'' magazine. Notable Skanska projects include renovation of t ...

, along with Rhône-Poulenc and the

Swedish Rail Administration , genre = , fate = , predecessor = Swedish State Railways , successor = Swedish Transport Administration , foundation = 1988 , founder = , defunct = 31 March 2010 , location_city ...

had criminal charges brought against them. Some senior executives resigned. Construction was halted in late 1997. The main critique of the use of Rhoca-Gil was against Rhône-Poulenc for not pointing out the risks of using the sealant, as well as against Skanska for not informing local residents about the usage of Rhoca-Gil. A similar incident occurred at the construction of Gardermobanen in

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and the ...

, leading to a ban of the substance in

in 1997. Moisture protection Polymers