Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.
Issue link: http://concrete.epubxp.com/i/75186
FEATURE PORTUGUÉS DAM production of the RCC and the required cooling of the RCC. Dragados-USA teamed up with San Antonio-based Plant Architects + Plant Outfitters in designing and building the entire production and cooling system. Large bolt-together silos were utilized to store several days of aggregate production. Plant Architects designed an overhead con- veyor system to fill the three large-diameter tanks set atop a cast-in-place concrete re- claim tunnel, which feeds dual wash screens and two 300-ft.-long chilled water (recircu- lation) wet belts for chilling the individual coarse aggregate. The coarse aggregate is chilled one type per belt at a time and then dewatered on the shale-shaker-type polyurethane decks at the discharge end of the wet belts prior to feeding a customized overhead conveyor system to twin five-com- partment aggregate batching plants equipped with individual weigh batchers. The fine aggregate is cooled by air and A frontal view of the dual plant setup shows the collapsable mixer platforms on skids, and the inte- grated electrical and control rooms to the right. The containerized buildings to the left house the USACE inspectors office, testing laboratory and admixture storage. Foundation construction behind the plant is for the large-scale custom built CTC ice plant. Environmental Resources, are constructing the project. When completed, this flood control dam will stand 220-ft. high, with a 11-ft. base and a 35-ft.-wide crest spanning 1,230 ft. It will contain an estimated 367,000 cu. yd. of RCC laid in 24-in. lifts delivered by overland belt conveyor and dump trucks, spread, leveled and com- pacted with road-building equipment. The U.S. Army Corps of Engineers, Jack- sonville District, awarded the contract for construction of the Portugués Dam at a base value of $180 million to Dragados USA, Inc., of New York City. Dragados had completed other monumental projects in Puerto Rico in the past, and is the world's leading RCC dam builder, second only to the Chinese govern- ment in projects completed to date. At 4,000-ft. elevation in a rainforest, the Portugués River is barely a creek most of the year at a mere 11 cubic feet per second. However as the rainy season sets in, the soil conditions and the steep terrain com- bine into a deadly force of floodwaters rushing toward the seaside city of Ponce at hundreds of thousands cu. ft. per second. The spillway now nearing completion by comparison, will allow 47,000 cu. ft. of water to breach the dam crest by design. The freshwater storage will equal 215-plus- acre flood pool and provide a multipurpose reservoir while saving much reoccurring human suffering and financial loss. The project is located approximately 68 | JULY 2012 three miles northwest of the city of Ponce on the Portugués River. Appurtenant struc- tures include an integral spillway and in- take. A valve house and control room for reservoir operation is located just down- stream adjacent to the river. Work also in- cludes foundation excavation in rock, placing foundation concrete, foundation grouting and development of an on-site quarry for concrete aggregate production. The Portugués Dam project is cost- shared with the Puerto Rican government, with the U.S. federal government provid- ing 75 percent and the local sponsor, the Puerto Rico Department of Natural and Environmental Resources, providing 25 percent of the required funds. Construc- tion started in April 2009 and is sched- uled for completion this summer. CHALLENGES & METHODOLOGY The project contract required that only a six month per year construction window be allowed due to ferocious river conditions and massive flooding of the area during the monsoon season, which normally starts in midsummer—coinciding with hurricane season. To make matters even more chal- lenging, the area is prone to earthquakes and required seismic design of the RCC dam and appurtenant structures, as well as the project's stationary equipment. The contractor chose to utilize its proven worldwide formula with regard to both the fed by a customized overhead conveyor sys- tem to two large-diameter, bolt-together storage tanks. The sand is then reclaimed from the tanks by an automated program- mable logic controller (PLC) and sent to the twin batching plant overhead bins on a au- tomated demand basis. Cement and pozzolan are stored in two large-diameter, bolt-together silos, each holding 1,000 tons of bulk powder, allowing for ensured storage inventory to the remote rainforest location, and providing much needed temperature stabilization. The bulk powders are transferred pneumatically from the two bolt-together storage tanks to the dual overhead silos on each of the redun- dant batching plants. LARGE-SCALE ICE PLANT In mass concrete placement schemes of struc- tural slump-type concrete and in RCC for mass structures, cooling of the constituent solids material is normally undertaken. The aforementioned dual wet belts are used for the chilling of coarse aggregate, air cooler for the fine aggregate and large-capacity storage of each of these and the bulk powders. Added to this is the chilling (or sometimes super- chilling to 32.5° F) of the batch water. These forced cooling measures are utilized in addi- tion to certain passive cooling measures (the large containment of the constituent mate- rials) such as shading, solar reflective mate- rial finishes and enclosures of both materials and the production equipment. In addition to these measures, where ex- cessive wet bulb temperatures are encoun- tered (combined heat and relative WWW.CONCRETEPRODUCTS.COM