Perlite, Expanded

A concrete additive consists of an expanded perlite with a volume weighted mean particle size of approximately 10-100 pm. The perlite further includes at least one additional component to improve workability and compensate for the natural tendency of expanded perlite to absorb water from the concrete mix. The additional component may include water, a superplasticizer such as polycarb-oxylates, naphthalene sulfonate, and melamine sulfonate, or a hydrophobic compoimd such as salts of fatty acids, fatty acids, silanes, and sUoxanes. 

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Filter aids as well as flocculants are employed to improve the filtration characteristics of hard-to-filter suspensions. A filter aid is a finely divided solid material, consisting of hard, strong particles that are, en masse, incompressible. The most common filter aids are applied as an admix to the suspension. These include diatomaceous earth, expanded perlite, Solkafloc, fly ash, or carbon. Filter aids build up a porous, permeable, and rigid lattice structure that retains solid particles and allows the liquid to pass through. These materials are applied in small quantities in clarification or in cases where compressible solids have the potential to foul the filter medium. 

Usually special solids, such as nut shells, limestone, expanded perlite, etc., are added to the drilling muds to fill or clog rock fractures in the open hole of a well. Most of these lost circulation materials can shorten the life of pump parts. They are especially hard on valves and seats when they accumulate on the seats or between the valve body and the valve disc. 

The most common low-specific-gravity solids used to reduce cement slurry specific weight are bentonite, diatomaceous earth, solid hydrocarbons, expanded perlite and pozzolan. It may not be possible to reduce the cement slurry specific weight enough with the above low-specific-weight materials when very weak formations are exposed. In such cases nitrogen is used to aerate the mud column above the cement slurry to assist in further decreasing the hydrostatic pressure. 

Expanded Perlite. Expanded perlite requires a great deal of water to be added to the slurry when it is used to reduce the specific weight of a slurry. Often perlite as an additive is used in a blend of additives such as perlite with volcanic glass fines, or with pozzolanic materials, or with bentonite. Without bentonite the perlite tends to separate and float in the upper part of the slurry. 

Still air is the important factor in dispersed solids, such as wood libers, exfoliated mica, powdered diaiomiie. and expanded perlite. 

The containers used for transporting and storing the majority of cryogenic liquids are insulated cryogenic tankers, liquid cylinders, and stationary storage tanks. These containers are similar in design to a Thermos bottle. There is an inner vessel, which contains the cryogenic product, and an outer vessel. The space between the two vessels is under a vacuum and usually contains a wrapped insulation material such as aluminized Mylar, or it may contain a powdered insulation such as expanded perlite. The liquid cylinders, usually 160-250 L in capacity, are constructed to a... 

Repeat Prob. 3-30 for expanded perlite insulation assuming conductivity is A = 0.052 W/m °C. 

Alkan, M., Demirbas, O., and Dogan, M., Zeta potential of unexpanded and expanded perlite samples in various electrolyte media, Micropor. Mesopor. Mater, 84, 192,... 

Drying furnaces are the main sources of solid (dust) emissions from the production of expanded perlite. The secondary technology operations of the production, accompanied by the formation of harmful emissions are as follows mechanical treatment of the raw perlite and its transportation. 

Filter aids should have low bulk density to minimize settling and aid good distribution on a filter-medium surface that may not be horizontal. They should also be porous and capable of forming a porous cake to minimize flow resistance, and they must be chemically inert to the filtrate. These characteristics are all found in the two most popular commercial filter aids diatomaceous silica (also called diatomite, or diatomaceous earth), which is an almost pure silica prepared from deposits of diatom skeletons and expanded perlite, particles of "puffed lava that are principally aluminum alkali silicate. Cellulosic fibers (ground wood pulp) are sometimes used when siliceous materials cannot be used but are much more compressible. The use of other less effective aids (e.g., carbon and gypsum) may be justified in special cases. Sometimes a combination of carbon and diatomaceous silica permits adsorption in addition to filter-aid performance. Various other materials, such as salt, fine sand, starch, and precipitated calcium carbonate, are employed in specific industries where they represent either waste material or inexpensive alternatives to conventional filter aids. 

Synonyms/Trade Names Expanded perlite [Note An amorphous material consisting effused sodium potassium aluminum silicate.]... 

Physical Description Odorless, light-gray to glassy-black solid. [Note Expanded perlite is a fluffy, white particulate.]... 

Expanded perlite. See Perlite Expanded polystyrene. See Polystyrene, expandable... 

Synonyms Expanded perlite Classification Silicon compd. 

Definition Amorphous mineral consisting of fused sodium potassium aluminum silicate, with variable chemical composition and <1% quartz Properties Lt. gray to glassy black transparent solid wh. or grayish-wh. fluffy or glassy-wh. particulate (expanded perlite) mod. sol. in NaOH si. sol. in min. acids (expanded) very si. sol. in water (expanded) dens. 2.2-2A, 0.05-0.3 (expanded perlite) m.p. > 1093 C, > 2000 F (expanded perlite) nonflamm. 

In combination with lightweight fillers (such as expanded perlite), concretes or mortars... 

In insulating refractory concretes the conventional aggregates are replaced by lightweight heat-resistant aggregates such as expanded vermiculite, expanded perlite, expanded chamotte, or pumice. These concretes are widely used to limit the heat losses of industrial kilns and high-temperature installations. 

To control the bulk density, low- or high-density materials may be added to the mix. To lowering the density, bentonite (sodium montmorrilonite based clay), typically in amounts between 2 and 12 wt%, may be used. Bentonite woiks by increasing the water demand of the slurry, as it can hold several times its own weight of water. The effectiveness of bentonite may be increased and its dosage lowered significantly if it is mixed with water and allowed to swell before being added to the slurry. Other materials that may be added to the slurry to lower its density include pulverized fly ash, diatomaceous earth, or expanded perlite. To increase the density of the slurry, finely... 

In the event that the sohds in the suspension are either too fine, even for the most efficient of filter fabrics, pre-coating the filter cloth with filter aids such as diatomaceous earth or expanded perlite will significantly enhance particle capture. In similar vein, where filtration conditions are difficult due to slimy suspensions, such agents are often added as body feed... 

Low density fireproof thermal insulation is bonded with colloidal silica. One type is a moldable foam of soluble silicate and colloidal silica foamed with a cationic surfactant. The foam type may include a polyalkylsiloxane for improved water resistance. Another is expanded perlite bonded with soluble silicate and colloidal... 

Absorbent for oil spills is a use in which synthetic hydrophobic silicas may play a role. However, a hydrophobic low cost expanded perlite, made hydrophobic by treatment with sodium methyl silanolate in water, is used to absorb floating oil. For some reason the presence of aluminum powder is said to improve the efflciency of the hydrophobing reaction (642). 

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