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POLYPLAST
STRENGTHENING SYSTEM
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INTRODUCTION The Polyplast Strengthening System is a thin coat reinforced plastering system designed to structurally upgrade existing masonry buildings to resist earthquake loads. The system is easily applied and provides a simple and economical alternative to traditional strengthening methods, thereby reducing construction time and site disruption. Often the building's architecture can be retained and the need for additional foundation work avoided. Masonry construction often has good compressive strength, but due to its brittle nature, lacks the tensile strength required to resist earthquake loads. In addition, any structural upgrading of a building must take account of the fact that earthquake loads can act in any direction. By using the inherent compressive strength of masonry construction and providing the required tensile capacity through the Polyplast Strengthening System, a building can be upgraded to resist these loadings. |
Loads in the direction of a wall are known as shear loads. The Polyplast Strengthening System has significant capacity to resist these loads and can act as a primary shear wall to stabilize the building as a whole. For loads at right angles to a wall, known as face loads, the Polyplast Strengthening System offers a number of options. The system can be applied on one or both sides of a wall, or alternatively in strips to provide the required loading capacity. In both situations the system offers the additional bonus of a bonding membrane that locks the individual bricks together. Full details of the various design options are available in the Polyplast Design Manual. |
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DESCRIPTION The Polyplast Strengthening System is based on three components:
The bags of plaster are mixed with water and resin on site, using a drill-powered whisk. This plaster mix is then applied to the prepared wall by trowel, hopper gun or plaster pump. A layer of fibreglass mesh is then laid against the wet plaster and trowelled into the plaster surface. The strength of the system can simply be increased with further layers of plaster and fibreglass mesh. With this system, up to five layers of fibreglass mesh and plaster can be built up. In reality most walls require only one or two mesh layers to achieve the required design load, with a resulting thickness of less than 11mm. The system can be applied to either the interior or exterior of a building. A variety of finishes can be applied over the Polyplast plaster to suit the style of the building being upgraded.
BENEFITS
DESIGN MANUAL Design Manual in PDF format (1642 KB) A comprehensive Design Manual for the Polyplast Strengthening System has been developed by engineering consultants, Kingston Morrison Ltd. who are specialists in the field of strengthening masonry buildings against earthquake loadings. All testing work associated with the development of the system, was carried out by Works Consultancy Ltd, Auckland. The Design Manual is presented in easy to use sections, covering all commonly found wall types and design situations. The first stage in the design process is to calculate the required wall loads. The Polyplast Design Manual is then used to determine the Polyplast system required. This procedure determines the number of layers of mesh required in the Polyplast plaster to satisfy the design requirements. The plaster and mesh application is continued in strips along the wall with each new layer of mesh overlapping the preceding one by at least 150mm. If multiple layers of fibreglass mesh are specified, allow the preceding mesh and plaster coat to at least reach the initial set stage before applying the next coat of plaster. Try and organise your work so that whole wall areas are completed in one day. When an area can't be completed in one day a CONSTRUCTION JOINT must be formed to allow the next day's work to be lapped into the previous reinforced mesh coats. |
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Do not let Polyplast dry out for the first 48 hours. Protect newly applied Polyplast from temperature extremes and rain for at least 24 hours. Apply Polyplast plaster only when the temperature is between 50 and 350 degrees and will be in that range for the 24 hour period after application. Aim to work on the shaded areas of the building, avoiding walls in direct sunlight. Health & Safety Polyplast plaster dust is an irritant and dust protection masks should be worn while it is being mixed. The wet plaster is alkaline and skin contact should be avoided. Plaster Storage Bags of Polyplast must be stored in a dry area, preferably off the floor on a timber pallet or timber dunnage. Rotate stock to ensure that the oldest material is used first. Plaster stock that is older than six months should be discarded. Painting & Finishing When Polyplast is used with embedded layers of fibreglass mesh and will be exposed to the weather or any dampness, a waterproof coating must be applied to ensure the long term durability of the fibreglass mesh. SUBSTRATE PREPARATION Polyplast is designed to be applied to DRY substrates. Do not wet down masonry or brick surfaces before the application of Polyplast and do not apply Polyplast to surfaces which are wet from rain or overnight dew. Brick, concrete block and masonry surfaces must be free of oil, paint, dirt and lichen growth. Any loose or unsound surface material must be hacked off back to a solid base. The surface of glazed bricks must be removed with a scabbling tool to ensure a good plaster bond. On smooth dense concrete surfaces, a suitable key must be applied to provide a suitable bond for the Polyplast plaster. Where required, corner beads or any depth gauge beads must be in place prior to the plaster application. PLASTER PREPARATION Each bag of plaster is mixed with 4.5 litres of water and one litre of resin. Depending on weather conditions and the method of application, a slight variation in the quantity of water may be required. Place all the water and Resin into a bin (a 50 litre rubbish bin is ideal) and add, while stirring with a powered whisk, all of the Polyplast plaster. Let the mix stand for 10 minutes and give it a quick re-stir before use. Do not mix more plaster than you can use in one hour. Do not re-activate the mix with water once it begins to set. Discard any plaster that has been mixed for more than one hour. APPLICATION The application and finishing of the Polyplast Strengthening System requires good plastering skills. The distributors strongly recommend that the system be applied by qualified plasterers or people experienced in the application of specialty plaster products. Thickness 5mm is the minimum plaster thickness for the first coat over any substrate. When using Polyplast with embedded layers of fibreglass mesh, the first coat is 5mm thick with subsequent plaster coats 3mm thick.
Plastering The plaster mix can be applied to the wall by trowel, hopper gun or plaster pump. The plaster is applied in strips about one metre wide and the mesh is laid against the wet Polyplast and then trowelled into the surface of the plaster. Note: Ensure the fibreglass mesh is laid into the wet plaster in the direction specified by the designer. Generally the mesh is laid in vertical drops, but for some design cases the mesh is laid in horizontally. |
