Maintenance Free, Sustainable Pre-cast Construction A Distinct Possibility
Not only admixtures have crucial role to play in precast quality enhancement, in an interaction with Built Constructions, Ms. Ishita Manjrekar and Mr. Sourabh Manjrekar of Sunanada Speciality Coatings Pvt. Ltd., say that exposed aggregates, admixtures, inserts and speciality coatings to enhance aesthetic appearance as well.
The widespread popularity of concrete as a building material can be attributed to the availability, favourable properties and geographic distribution of its naturally occurring mineral constituents. Concrete itself is easily formed and moulded, comparatively economical, and durable in its finished state. Architectural precast panel use has increased because of the nature of concrete as a material and the fact that prefabricated components add to construction efficiency. In addition by exposing decorative aggregates, using veneer facing materials and by varying sizes, shapes and textures of panels, the engineer/architect has significant aesthetic possibilities for creative response to the client’s needs.
Basic materials used in the fabrication and erection of precast concrete are the same as those used in cast-in-place structural concrete. However, precast concrete panels also make extensive use of special materials including exposed aggregates, admixtures, inserts and speciality coatings to enhance aesthetic appearance.
A typical inventory of materials used in the construction of precast concrete panels are:
- Portland Cement
- Aggregates both standard and decorative
- Insulating Materials
- Reinforcement and Inserts
- Surface Retarders
- Form Release Agents
- Corrosion Inhibiting Systems Coatings and Admixtures
- Admixtures
- Grouts
- Curing Compounds and Sealers
- Joint Sealants and Fillers
Sunanda Chemicals hold an expertise with respect to supply to manufacturers and users of pre-cast concrete. Outlined below is a brief description of each specialized system manufactured by Sunanda.
Corrosion Protection of Reinforcement
When aesthetic considerations cause reduction of the concrete minimum cover below that ordinarily specified or recommended, reinforcement in thin precast concrete panels becomes susceptible to corrosion. In such cases, the long term appearance and durability of the panels a corrosion protection strategy is required to be implemented. Admixing, POLYALK CP 293TM Bipolar Migratory corrosion Inhibiting Admixture to the concrete is the most user-friendly and effective way to ensure long term corrosion protection. Use of corrosion inhibiting admixture overcomes the problems associated with discontinuity and holidays in steel coatings which inturn become sites for rapid corrosion damage.
Grouts
Cementitious and epoxy grouts POLYEXPANSE TM and SUNEPOXY 368 TM respectively are used in case doweled or grouted connections are part of the structural design concept. Epoxy injection material may also be required to repair large cracks.
Curing Compounds
Although not generally used, curing compounds are preferred over water or other wetted coverings where additional curing of the concrete is required. SUNPOLICURE W TM has been found to give good results in these special cases.
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Ms. Ishita Manjrekar
Director, Sunanda Speciality
Coatings Pvt. Ltd.
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Mr. Sourabh Manjrekar
Director (International Operations),,
Sunanda Speciality Coatings Pvt. Ltd.
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Surface Sealers
The use of a clear, protective, water-repellent sealer like SUNSILOX PRIMER TM serves to improve the weather ability of the concrete especially in urban and industrial areas. These sealers have a water repellent property and reduce the attack of airborne pollutants on the exposed concrete.
Joint Sealants
Cement mortars are not extensible and cannot accommodate panel movement. Only elastomeric materials with excellent bonding ability to a wide variety of materials should be used as sealants in precast panel installation. Despite higher initial costs, elastomeric sealants are preferred because of lower maintenance costs, watertight joints and longer life. Sunanda recommends FLEXIROOF PU TM single component, polyurethane with an elongation ability of more than 600%.
Sustainability
All the above product systems serve to increase the durability and service life of the structure by preventing pre-mature damage due to corrosion, water-seepage and chemical attack on the exposed concrete. A wise selection of materials, quality control during both manufacturing and erection are as important as design.