Road surfaces are often made from asphalt concrete which uses bitumen as a matrix. Various forms of pitch may also be called tar, bitumen, or asphalt. Naturally occurring asphalt/bitumen, a type of pitch, is a viscoelastic polymer. Naturally occurring asphalt is sometimes specified by the term "crude bitumen". There are also deposits of peat, bitumen, shale and oil. Dilbit (diluted bitumen) is a means of transporting highly viscous hydrocarbon. In American English, "asphalt" is equivalent to the British "bitumen". The republic has good deposits of lignite with a high degree of bitumen. Oxalic acid may increase the leaching of radionuclides conditioned in bitumen for radioactive waste disposal. These have a combined capacity of of crude bitumen. These large amounts of waste are a mixture of water, sand, clay, and residual bitumen. Commonly, the court has either a bitumen or concrete surface. Froth treatment converts bitumen into diluted bitumen, a marketable product. The soluble portion is known as bitumen. The unhardened bitumen was then dissolved away.