17-01-2013, 04:32 PM
Admixtures & adhesives
Admixtures &.ppt (Size: 3.51 MB / Downloads: 84)
Adhesives
STRUCTURAL ADHESIVES
Structural Adhesives are used for bonding applications, where the bonded joint must transfer high loads without deformation and creep. For automotive use, also a very high impact resistance is required to replace welding operations. Usually structural adhesives are applied in layers thinner than 1 mm.
Our structural adhesives are based on Epoxy-, Acrylic- and Polyurethane resins and can be formulated in room temperature. For lamination, solvent- or water based dispersions are used.
Natural adhesives
Animal glues used for centuries in carpentry and joinery.
An animal glue is an adhesive that is created by prolonged boiling of animal connective tissue.
Sold in powder form melted in warm water.
Greeks and Romans later used animal and fish glue to develop veneering and marquetry, the bonding of thin sections or layers of wood
Casein glues
Derived as precipitate from skimmed milk by action of acids. Mixing is carried out in cold and setting is by partly by evaporation or absorption of water and partly by a natural gelation process
Adhesive installation over concrete
SITE CONDITIONSThe environment in which the carpet is to be installed must be controlled with the temperature between 65° F and 95° F (18° C and 35° C) and the relative humidity between 10% and 65%. The slab temperature should not be less than 65° F (18° C). These conditions must be maintained for at least 48 hours before, during, and 48 hours after the installation.
FLOOR PREPARATION
Concrete must be cured, clean, and dry, free of paint, dirt, grease, oil, curing or parting agents, and other contaminants, including sealers, that may interfere with the bonding of the adhesive.
Liquid Adhesive Removers - There are liquid adhesive removers available that will effectively remove cut-back or emulsion adhesive residue from subfloors; however, there is evidence these products may adversely affect the new adhesive or the new floor covering. Any residual of these products left in or on the concrete slab is capable of causing a failure. The use of these removers may void all applicable warranties.
Definition
Admixtures are materials in the form of powder or fluids that are added to the concrete to give it certain characteristics not obtainable with plain concrete mixes. In normal use, admixture dosages are less than 5% by mass of cement and are added to the concrete at the time of batching/mixing.
Rice Husk ash
Rice husk are the hard protective covering of the grain of rice.
They are highly siliceous material which can be used as an admixture in concrete which:-
Increases both strength and durability of concrete.
also improves the early strength development of concrete.
Replace 15-30 % of Portland cement in concrete.
Provides protection against cracking by forming calcium silicate hydrate gel around the cement particles.
Blast furnace slag
Blast furnace slag is the by-product left in the manufacturing of pig iron.
Blast furnace slag is pozzolanic in nature and have all the basic elements of cement i.e. silica, alumina and lime.
It is used upto 60-65% in making cement.
The cement produced from blast furnace slag has the same durability and strength as ordinary Portland cement.
Also very economical.
Fly ash
Fly ash is the finely divided residue left from the combustion of ground or powdered coal.
fly ash particles have a very high fineness having the diameter ranges from 1 to 100 micrometer.
fly ash is added in the concrete to increase its workability because of the spherical shape of its particles.
As it is pozzolanic in nature, so it can replace unto 30 % by mass of Portland cement in making concrete.
Also increase the final strength of concrete and make it durable.