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 Seal (mechanical), mechanical seal. In building construction ''sealant'' is sometimes synonymous with ''caulk'' (especially if acrylic latex or ...

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 ...

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

groundwater Groundwater is the water present beneath Earth's surface in rock and Pore space in soil, soil pore spaces and in the fractures of stratum, rock formations. About 30 percent of all readily available fresh water in the world is groundwater. A unit ...

inside. The sealant begins as a liquid, then is 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 ...

(a toxic substance) and methylolacrylamide. The mixed solution becomes a viscous fluid that penetrates cracks and holes in the rock, where the fluid reacts—

polymerizes In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many form ...

—to a tight plastic substance. When it is completely polymerized it is stable.

Controversies

In 1992 construction of the Hallandsås tunnel in

Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...

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 agent that promotes the development of cancer. Carcinogens can include synthetic chemicals, naturally occurring substances, physical agents such as ionizing and non-ionizing radiation, and biologic agents such as viruse ...

mutagen In genetics, a mutagen is a physical or chemical agent that permanently changes genetic material, usually DNA, in an organism and thus increases the frequency of mutations above the natural background level. As many mutations can cause cancer in ...

and

neurotoxin Neurotoxins are toxins that are destructive to nervous tissue, nerve tissue (causing neurotoxicity). Neurotoxins are an extensive class of exogenous chemical neurological insult (medical), insultsSpencer 2000 that can adversely affect function ...

. 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. It was established in 1887 as a concrete product manufacturer. History Aktiebolaget Skånska Cementgjuteriet (Scanian Cement Casting Ltd) was established i ...

, along with Rhône-Poulenc and the

Swedish Rail Administration The Swedish National Rail Administration () was a Swedish state administrative authority which acted as owner on behalf of the State and maintained virtually all main railway lines in Sweden; except for short sidings for freight, heritage railwa ...

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 The Gardermoen Line () is a high-speed railway line between Oslo and Eidsvoll, Norway, running past Lillestrøm and Oslo Airport, Gardermoen. The line is long and replaced the older Hoved Line as the main line north-east of Oslo. The older Hove ...

Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. The remote Arctic island of Jan Mayen and the archipelago of Svalbard also form part of the Kingdom of ...

, leading to a ban of the substance in

in 1997.

References

{{reflist Moisture protection Polymers