Cement Americas

Fal 2017

Cement Americas provides comprehensive coverage of the North and South American cement markets from raw material extraction to delivery and tranportation to end user.

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18 CEMENT AMERICAS • Fall 2017 • www.cementamericas.com FEATURE In times of frost and thaws, trapped water expands and contracts causing unseen, yet detrimental, damage. This unseen damage can lead to unexpected safety issues in spite of regular inspections. Coatings should also provide excellent waterproofing and tolerate pooling water typical of a flat roof surface. Water resistance before and after drying should also be considered. Additionally, coatings should perform well despite weather extremes, and provide thermal stability, UV protection, and resistance to acids, alkali and salt. Polyurethanes – Polyurethanes used for roof-top coating include thermosetting coatings and spray poly- urethane foam (SPF). Polyurethanes are not intended for use in any areas that take foot traffic. When used as a standalone roofing surface, SPF is highly susceptible to damage from even light foot traffic. While some struc- tures may be able to safely rely on spray foam coatings, its use in aggregate storage silos is not recommended as easily damaged foam coating surfaces lead to easy water penetration. Sensitivity to humidity further limits the use of polyurethanes. Acrylics – Known as an inexpensive material that pro- vides good aesthetics, acrylics fall short on protection and longevity. Acrylic coatings are sensitive to ultravio- let light and cold temperatures. As such, they are prone deterioration, known as chalking, that leaves a powdery substance on the coating surface as it breaks down. Acrylics are often mixed with other coating types to improve product appearance. Epoxies – There are several downsides to epoxy coat- ings. In addition to high flammability, epoxies come with a number of health risks from fumes and dust. Epoxy- based coatings also perform poorly in cold climates where freezing temperatures increase the likelihood of cracking, splitting, or peeling. Furthermore, additional coats do not automatically bond to previous coats. Synthetic Rubbers – A highly effective coating, syn- thetic rubber offers numerous benefits and great aesthet- ics. Brands come with a variety of color choices, which all deliver excellent UV protection. Lighter colors, however, provide greater solar reflectance to help keep silo roof tops cooler and reduce the urban heat island effect. When compared to acrylic coatings, synthetic rubber coatings offer higher tensile strength, greater elonga- tion, better adhesion to foam, and superior water, fun- gi and fire resistance. Unlike acrylic coatings, synthetic Corroded rails and walkways on unprotected silo roof. Silo roof protected with rubberized coating. Another image of a silo roof, freshly coated with high- ly-protective synthetic rubber.

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