Rock Products

MAY 2018

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68 • ROCK products • May 2018 cement used in mass concrete allowed for higher strength gains and reduced peak heat of hydration. Sellwood Bridge – Portland, Ore. Member Company: Ash Grove Cement Co. Category: High Performance Almost 2,000 ft. of concrete pavement, widened lanes, side- walks and two bike lanes are a part of this bridge replacement project. Slag cement was used at 50 percent replacement of portland cement in mass concrete to lower heat of hydration and had an average strength of more than 6,700 psi in 56 days. St. Croix Crossing – Oak Park Heights, Minn. Member Company: Skyway Cement Co. Category: Innovative Application After many mix designs were tested, the project team felt slag cement was a must for its beneficial effects on compressive strength, freeze/thaw durability, surface scaling, and rapid chloride permeability. The project included more than 200 mass concrete placements, most including 65 to 70 percent slag cement. Tampa Airport Taxiway "J" Bridge Reconstruction – Tampa, Fla. Member Company: Argos USA Category: High Performance The Tampa International Airport recently finished the reconstruction of a 300-ft. long by 200-ft. wide taxiway bridge. The bridge was built to regularly support the weight of Boeing 777 and Boeing 747 aircraft and used a mix design with a 30 percent slag cement replacement of cementitious material. Zurich North America Headquarters – Schaumburg, Ill. Member Company: LafargeHolcim Category: Green Design The architectural character of the almost 800,000-sq.-ft. complex uses an interesting material palette, reinforcing the design team's commitment to sustainability. The mix designs had slag cement replacement percentages from 18.5 percent to 24.4 percent. Overall, slag compromised approximately 23 percent of the cementitious content in the almost 33,000 yd. of concrete. Reducing Cement Pre-Hydration Could Improve Quality GCP Applied Technologies presented a research paper on improving the quality of cement from vertical roller mills by reducing pre-hydration during the 25th ASEAN Feder- ation of Cement Manufacturers Technical Symposium & Exhibition. The company also showcased two new cement additive ranges – the TAVERO VM grinding aids and OPTEVA HE quality improvers. Compared with ball mills for cement production, vertical roller mills require a smaller plant footprint and offer greater energy efficiency and narrower cement particle size distri- bution. Cement produced in vertical roller mills, however, sometimes exhibits lower strengths and longer initial set- ting times as compared to ball-milled cements made with the same raw materials. "As more and more cement companies introduce vertical roller mills in their production, it was important for us to deliver solutions that can help optimize cement production and quality," said Robert AuYeung, Asia Pacific director of marketing, GCP Applied Technologies. "Our research found that using suitable grinding aids and reducing water spray could limit cement pre-hydration and improve cement compressive strength from 1.5 to 3 MPa at all ages tested. Similarly, initial setting time was also shown to have a modest reduction of 15 minutes." To enable producers to lead in cement quality, cost efficiency and sustainability, GCP introduced the new additives ranges: •  TAVERO VM grinding aid additives, which help stabilize vertical roller mills during production by reducing water injection requirements and cement pre-hydration. At the same time, they improve cement performance by delivering higher strengths and shorter setting times. •  OPTEVA HE quality improvers are cement additives that provide options for gaining higher early (HE) strength and are particularly effective for challenging cements. "TAVERO VM additives enable more stable VRM production with less usage of water and potential fuel savings with reduced need to heat the mill. It also enables better cement quality with lower energy consumption and less wear on equipment," AuYeung said. "OPTEVA HE additives enable greater use of supplementary cementitious materials in place of clinker and increasing use of alternative fuels. This reduces greenhouse gas emissions and also lowers the costs of cement production." GCP has more than 80 years of experience producing high-quality grinding aids and performance enhancers. The company's grinding aids have helped producers improve cement productivity by up to 20 percent without additional production costs. Similarly, GCP's quality improvers have helped improve mill production by up to 20 percent; early- and long-term compressive strength by up to 30 percent; and helped lower energy consumption by about 25 percent, all without any loss of cement quality. "Our cement additives and water-reducing concrete admix- tures reduce air pollution equivalent to more than 10 million cars annually," AuYeung said. "Through the use of GCP's cement additives globally, about 3,000 megawatt hours of electricity are saved daily that's equal to the daily energy consumption of half a million families."

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