Pugmill
Encyclopedia
A pugmill or pug mill is a machine in which materials are simultaneously ground and mixed with a liquid. Industrial applications are found in pottery
, brick
s, cement
and some parts of the concrete
and asphalt
mixing processes. A pugmill is a fast continuous mixer. A continuous pugmill can achieve a thoroughly mixed, homogeneous mixture in a few seconds. Mixing materials at optimum moisture content requires the forced mixing action of the pugmill paddles, while soupy materials might be mixed in a drum mixer. A typical pugmill consists of a horizontal boxlike chamber with a top inlet and a bottom discharge at the other end, 2 shafts with opposing paddles, and a drive assembly. Some of the factors affecting mixing and residence time are the number and the size of the paddles, paddle swing arc, overlap of left and right swing arc, size of mixing chamber, length of pugmill floor, and material being mixed.
Common construction and industrial uses include:
Road Base - Dense well-graded aggregate, uniformly mixed, wetted, and densely compacted for building the foundation under a pavement.
Lime Addition to asphalt – Lime may be added to the cold feed of an asphalt plant
to strengthen the binding properties of the asphalt.
Flyash Conditioning – Wetting fly ash
in a pugmill to stabilize the ash so that it won’t create dust. Some flyashes have cementitious properties when wetted and can be used to stabilize other materials.
Waste stabilization – various waste streams are remediated with pugmills forcing the mixing of the wastes with remediation agents.
Roller-compacted concrete
– (RCC) or rolled concrete is a special blend of concrete that has the same ingredients as conventional concrete but in different ratios. It has cement, water, and aggregates, but RCC is much drier and essentially has no slump. RCC is placed in a manner similar to paving, often by dump trucks or conveyors, spread by bulldozers or special modified asphalt pavers. After placement it is compacted by vibratory rollers.
The “stiff” nature of RCC may require a paddle type pugmill to force the materials to mix completely and discharge easily.
In ceramic
s pug mills, or commonly just "pugs", are not used to grind or mix, rather they extrude clay bodies prior to shaping processes. Some can be fitted with a vacuum system that ensures the extruded clay bodies have no entrapped air. According to the 1913 edition of Webster's Dictionary
, a clay pug mill typically consists of an upright shaft armed with projecting knives, which is caused to revolve in a hollow cylinder, tub, or vat, in which the clay body is placed.
Pottery
Pottery is the material from which the potteryware is made, of which major types include earthenware, stoneware and porcelain. The place where such wares are made is also called a pottery . Pottery also refers to the art or craft of the potter or the manufacture of pottery...
, brick
Brick
A brick is a block of ceramic material used in masonry construction, usually laid using various kinds of mortar. It has been regarded as one of the longest lasting and strongest building materials used throughout history.-History:...
s, cement
Cement
In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...
and some parts of the concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
and asphalt
Asphalt
Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...
mixing processes. A pugmill is a fast continuous mixer. A continuous pugmill can achieve a thoroughly mixed, homogeneous mixture in a few seconds. Mixing materials at optimum moisture content requires the forced mixing action of the pugmill paddles, while soupy materials might be mixed in a drum mixer. A typical pugmill consists of a horizontal boxlike chamber with a top inlet and a bottom discharge at the other end, 2 shafts with opposing paddles, and a drive assembly. Some of the factors affecting mixing and residence time are the number and the size of the paddles, paddle swing arc, overlap of left and right swing arc, size of mixing chamber, length of pugmill floor, and material being mixed.
Common construction and industrial uses include:
Road Base - Dense well-graded aggregate, uniformly mixed, wetted, and densely compacted for building the foundation under a pavement.
Lime Addition to asphalt – Lime may be added to the cold feed of an asphalt plant
Asphalt plant
An asphalt plant is a plant used for the manufacture of asphalt, macadam and other forms of coated roadstone, sometimes collectively known as blacktop....
to strengthen the binding properties of the asphalt.
Flyash Conditioning – Wetting fly ash
Fly ash
Fly ash is one of the residues generated in combustion, and comprises the fine particles that rise with the flue gases. Ash which does not rise is termed bottom ash. In an industrial context, fly ash usually refers to ash produced during combustion of coal...
in a pugmill to stabilize the ash so that it won’t create dust. Some flyashes have cementitious properties when wetted and can be used to stabilize other materials.
Waste stabilization – various waste streams are remediated with pugmills forcing the mixing of the wastes with remediation agents.
Roller-compacted concrete
Roller-compacted concrete
Roller-compacted concrete or rolled concrete is a special blend of concrete that has essentially the same ingredients as conventional concrete but in different ratios, and increasingly with partial substitution of fly ash for Portland cement. RCC is a mix of cement/fly ash, water, sand, aggregate...
– (RCC) or rolled concrete is a special blend of concrete that has the same ingredients as conventional concrete but in different ratios. It has cement, water, and aggregates, but RCC is much drier and essentially has no slump. RCC is placed in a manner similar to paving, often by dump trucks or conveyors, spread by bulldozers or special modified asphalt pavers. After placement it is compacted by vibratory rollers.
The “stiff” nature of RCC may require a paddle type pugmill to force the materials to mix completely and discharge easily.
In ceramic
Ceramic
A ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
s pug mills, or commonly just "pugs", are not used to grind or mix, rather they extrude clay bodies prior to shaping processes. Some can be fitted with a vacuum system that ensures the extruded clay bodies have no entrapped air. According to the 1913 edition of Webster's Dictionary
Webster's Dictionary
Webster's Dictionary refers to the line of dictionaries first developed by Noah Webster in the early 19th century, and also to numerous unrelated dictionaries that added Webster's name just to share his prestige. The term is a genericized trademark in the U.S.A...
, a clay pug mill typically consists of an upright shaft armed with projecting knives, which is caused to revolve in a hollow cylinder, tub, or vat, in which the clay body is placed.