Gypsum rock

OC-Hemihydrate. Three processing methods are used for the production of a-hemihydrate. One, developed in the 1930s, involves charging lump gypsum rock 1.3—5 cm in size into a vertical retort, sealing it, and applying steam at a pressure of 117 kPa (17 psi) and a temperature of about 123°C (6). After calcination under these conditions for 5—7 h the hot moist rock is quickly dried and pulverized. 

Soft Materials (1) Talc, dried filter-press cakes, soapstone, waxes, aggregated salt ciystals (2) gypsum, rock salt, ciystahine salts in gener, soft coal (3) calcite, marble, soft limestone, barites, chalk, brimstone. 

Manufacture Mined phosphate rock is reacted with sulfuric acid. The product phosphoric acid is isolated as a 28-35% solution by filtering off the insoluble calcium sulfate co-product. CasfPOJj + SHzSO 2H3P04 + 3CaS04 phosphate sulfuric gypsum rock acid... 

Intake of water in the aerated zone is either by infiltration into the soil cover or, on bare rock surfaces, by infiltration into intergranular pores (as in sand-stone), fissures and joints (as in igneous rocks or quartzite), or dissolution conduits and cavities (limestone, dolomite, gypsum, rock salt). Only pores and fissures that are interconnected, or communicate, are effective to infiltration. 

By the 1983 start-up, Tampa Electric intends to meet the commercial specifications for wallboard use, as well as for briquets for local cement plants. Gypsum rock from Spain is presently imported by the local cement plants. Fully oxidized gypsum, 93 + % CaSO4 2H2O, low in chlorides and magnesia, will be produced. 

Karmazsin s paper describes a simple apparatus for measuring the degree of hydration of plaster and gypsum rock. The reactor consists of a vertical stainless steel cylinder capable of holding six small stainless steel sample tubes that are suspended from the removable roof of the cylinder by a stainless steel thermocouple well. The cylinder is fitted with a heater controlled by an external thermocouple, and a reservoir containing water vapor at 81% relative humidity is connected to the reactor. The reactor may be used to determine accurately the amount of dihydrate in either gypsum rock or incompletely hydrated plaster. 

For the last decade the growing extension of Madrid has led to the construction of housing and industrial estates to the east and southeast of the city centre. The terrain in these areas is chiefly gypsum rock affected by dissolution phenomena, covered with clayey material. 

Karst cavities in the gypsum rock are an important concern for all specialists involved in the foundation design for construction projects. In this respect, slab foundations have advantages over isolated footing foundations and over deep pile foundations. 

---