Pre-formed Membrane Systems

When we talk about waterproofing types, preformed membrane system is very important one. Normally preformed water proofing membrane systems are available in sheets form. Preformed membrane waterproofing shall conform to these special provisions. The preformed membrane waterproofing system is consist of an adhesive (paste), conditioner or basic coverage applied to a prepared surface, a preformed membrane sheet of rubberized asphalt or polymer modified bitumen, mastic or tape for sealing the edges of the sheet and a protecting cover over the sheet held by an adhesive. The preformed membrane sheet should be either permanently applied to a polyethylene layer or reinforced with a polypropylene mesh fabric, polyester or polypropylene fabric or a fiberglass mesh fabric.

The preformed membrane sheets shall conform to the following requirements

ü Adhesives or conditioners or mastics and sealing tapes should be manufactured for use with the respective preformed membrane sheet materials

ü Above things should be applied according to the manufacturer's recommendations.

ü The protective covering shall be 3-mm minimum thickness hardboard or other material that fill in equivalent protection. Also backfill material and equipment should not cut, scratch or cause any other damage to the preformed membrane.

ü Surfaces elected to receive preformed membrane waterproofing shall be methodically cleaned of dirt, dust, loose or unsound concrete, and other unrelated material and should be free from fins, sharp edges, and projections that would puncture or otherwise damage the membrane.

ü Surfaces should be dry when components of the preformed membrane waterproofing system are applied.

ü Preformed membrane waterproofing should not be applied to any surface until the contractor is prepared to follow its application with the placing of the protective covering.

ü Also it should be backfilled within a sufficiently short time that the membrane will not be damaged by workers or equipment, exposure to weathering, or from any other cause.

ü All projecting pipe, conduits, covers or other facilities passing through the preformed membrane waterproofing should be flashed with prefabricated cover.

ü All conditioner or primers shall be thoroughly mixed and continuously agitated during application. Conditioner, primers or adhesive shall be allowed to dry to a tack free condition prior to placing membrane sheets.

ü The preformed membrane sheet should not be applied in wet or foggy weather, or when the temperature is below 4°C.

ü Preformed membrane material should be placed starting at the bottom and lapped by a minimum of 150 mm at splices and at repairs to holes.

ü The surface of the preformed membrane should be cleaned free of dirt and other harmful material before the protecting cover is placed.

ü The protective covering should be placed on a coating of adhesive type recommended by the manufacturer. The adhesive should be applied at a rate sufficient to hold the protective covering in position until the backfill is placed.

rubberized asphalt

Asphalt roof sheeting is typically used as a single ply roofing membrane for industrial and commercial flat roofs. These membranes are usually processed into sheeting rolls and applied to roofs in long strips. Synthetic or natural polymeric materials are added to the asphalt-based membrane, thereby achieving elasticity and flexibility. Typically, vinyl containing polymers are added to accomplish such results.

Rubberized asphalt is usually used as cover or pavement material that consists of regular asphalt concrete mixed with crumb rubber. Rubberized asphalt has used as waterproofing material since 1960’s because of its high durability. Also it has ability to reduce noise that means sound resistance.

Features

-Unique side-lap feature offers superior water-tightness

-Excellent cold weather application properties

-Factory controlled thickness

-No odor or VOC’s

-Fully adhered systems prevents lateral water movement

-Resists up to 231 feet of positive-side head pressure

Limitations

Non-resistant to oils and solvents. Not designed for use in direct contact with potable water or permanent exposure and must be covered to prevent damage from sunlight. Good practice calls for the membrane to be covered immediately following application. Do not use in contact with flexible PVC/vinyl products. Using solvent-based primers in below-grade applications is not recommended to avoid possible hazardous fume accumulations.

Uses

Is designed for use as a self-adhered sheet waterproofing membrane in above or below grade applications. Principal application is on concrete foundation walls, plaza decks, tunnels, and parking decks in both vertical and horizontal orientations. Is an ideal membrane for use in interior applications such as mechanical rooms, laboratories and wet-rooms.

Surface Preparation

Acceptable substrates are cast-in-place concrete, precast concrete, wood, concrete block, and polystyrene insulation form foundations. Parging of concrete blocks is not required. All surfaces to receive must be clean of oil, dust and excess mortar. Concrete surfaces must be smooth and without large voids, spalled areas or sharp protrusions. Concrete must be allowed to cure a minimum of 7 days and must be dry and free from frost before applied. Structural lightweight concrete must be cured 14 days. Where curing compounds are used, they must be clear resin based, self dissipating, without oil, wax or pigments. Primed surfaces not covered by membrane during the same working day must be reprimed.

Application

Vertical Applications: Apply waterproofing membrane to prepared substrate in lengths of 8’ or less. Provide 2 ½” laps at both sides and ends. Position for alignment and remove protective film. Press firmly into place. Promptly roll all laps with a counter top roller to affect seal. If more than one length is required on a vertical surface, apply a shingle fashion.

Horizontal Applications: Apply waterproofing membrane to prepared substrate beginning at the low point of the surface and working to the high point in a shingle fashion. Provide 2 ½” side and end laps. Roll membrane immediately over entire surface to ensure best seal.

Bituminous

Self adhesive membranes are produced with a special multi-layer design with a fiberglass or polyester reinforcement which is impregnated and coated on both sides with a uniquely formulated bitumen compound, which provides high adhesive properties.

Modified bituminous materials can bring real benefits to highway maintenance and construction. It is also the best in savings in total road life costing. The term "polymer" does not automatically mean an artificial material. It basically means a combination of a large number of similar small molecules into large molecules. There are a large number of naturally occurring polymers. These can be organic or mineral substances. Bitumen is so useful in the road making and road maintenance industries because of its basic thermoplastic nature and water resistance nature. The basic properties of bitumen can be modified by the addition of flux oils or volatile oils to produce bitumen of various grades. When we talk about polymer modified bitumen, polymer does not chemically combine or change the chemical nature of the bitumen being modified, apart from being present in and throughout the bitumen. What polymers will do is change the physical nature of bitumen, and they are able to modify such physical properties as the softening point and the brittleness of the bitumen. Elastic recovery and ductility can also be improved.

Features

· Positive barrier to water and vapor

· Excellent resistance to atmospheric agents

· High flexibility at low temperatures

· Withstand thermal shocks

· Easy application

· Resistance to chemical attacks

Application

· The surface to receive should be smooth, dry, free from dust and dirt. The surface should be primed thoroughly. Membrane is installed by progressively peeling off the release paper and unrolling the membrane along with it. The membranes, particularly at the overlaps should be firmly pressed down to ensure a good seal.

· Torch-on Application - After having mopped the surface, allow a drying time up to 24 hours. The membrane is unrolled and placed in position where it has to be torched on later. The membrane is then rerolled without changing the given orientation and unrolled again, while heating the lower surface with a propane gas torch, causing surface melting and subsequent adhesion to the primed surface. Membrane should overlap each other by at least 10cm at the side of lap and joints must be carried out to ensure total adhesion. Smooth out seams with a rounded trowel.

· Hot mop on Application - A hot primer is first mopped on or poured directly on to the laying surface. The temperature of the hot primer to be mopped should be around 111 ^oC. The membrane is then positioned and unrolled immediately over the hot primed surface. While unrolling the membrane, hot primer is poured at the seams to ensure a properly sealed overlap joint with a slight flow or primer at all the seams. Subsequent rolls are set alongside the first.

· Mechanical fixing - Membranes may be applied mechanically by nailing the membranes to the deck, using special fasteners.