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2013WinShotcreteEMag

Sustainability Top Ten Sustainability Benefits 1. Formwork savings of 50 to 100% over conventional of Shotcrete cast-in-place construction. The United States Green Concrete Council’s (USGCC) book, 2. Formwork does not have to be designed for internal pressures. The Sustainable Concrete Guide—Applications, includes a list 3. Complex shapes require very little—if any—formwork. of the top 10 sustainability benefits of shotcrete in its chapter 4. Crane and other equipment savings or elimination. on shotcrete. Over the next 10 issues of Shotcrete magazine, 5. Labor savings of at least 50% in repair applications. this Sustainability column will elaborate on each one of the 6. New construction speed savings of 33 to 50%. listed advantages. Previous discussion of advantages from past 7. Speed of repair reduces or eliminates downtime. issues can be viewed on the ASA website at www.shotcrete. 8. Better bonding to the substrate enhances durability org. Look in the “Why Shotcrete?” section for “Sustainability.” (see below). U.S.GREEN 9. with other processes.Adaptability to repair surfaces that are not cost-effective CONCRETE COUNCIL 10. Ability to access restricted space and difficult-to-reachareas, including overhead and underground. Better Bonding to the Substrate enhances Durability cmaterial on the planet. Concrete can be easily produced perform as a single cohesive element. Research has proven thatevery concrete reconstruction or repair. Typical structuraldesigns require both the existing and replacement material tooncrete is, by the definition of sustainability, the perfectconstruction material. It is the most common construction from widely available, plentiful natural resources, and it is durable, permanent bonds can be attained by using properly completely recyclable. History has proven that structural prepared substrate conditions in conjunction with shotcrete elements made from concrete tend to last longer and require placement methods. Studies focusing on the bond qualities of less ongoing maintenance than any other common construction material. History has also proven that all concrete elements shotcrete have proven that a sound substrate surface with an eventually deteriorate or need to be reconfigured over time. adequate roughness profile provides a suitable surface to New concrete construction currently benefits from an array form a durable bond. Shotcrete applied to a properly of material advancements and innovative construction prepared substrate offers a significantly stronger and more techniques that have substantially improved the sustainability durable bond than traditional casting placement methods. Other of modern elements constructed from concrete. The use of factors, such as surface moisture conditions, impact energy, supplementary cementitious materials such as slag, fly ash, and shrinkage, and the mixture properties of the repair materials, microsilica and the more recent use of other recycled materials can also affect the long-term bond quality. For many projects, in the production of greener concrete reduce the environmental bond quality will have the strongest influence on repair impact of new concrete construction. durability (refer to Fig. 2). But what about the immense inventory of existing concrete structures? Wear, exposure, deterioration, or obsolescence Why Shotcrete Placement methods ultimately mandates the life span of all concrete elements. The increase Bond Quality ability to repair or reconfigure, rather than replace, existing Pneumatically applied shotcrete is capable of producing a concrete elements enhances sustainability, as repair methods can significantly extend the structures’ useful service life stronger, more durable bond to cementitious, masonry, or (refer to Fig. 1). stone substrates than any other common application method. Understanding the reason behind this requires insight into the Bonding Becomes the critical element principles of the shotcrete process. Both wet- and dry-mix The ability to form a durable bond interface between the shotcrete’s superior bond properties are not due to mixture existing substrate and the new concrete is critical to nearly proportion differences between shotcrete and traditional 58 Shotcrete • Winter 2013


2013WinShotcreteEMag
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