CONSTRUCTION AGGREGATES, ENGINEERING STRUCTURES AND HUMAN ACTIVITY

Mineral aggregates played a major role in advancing engineering construction. Human progress closely parallels advances in construction methods and materials. Utilization of mineral aggregates contributed greatly; they consist of sand, gravel, crushed stone, slag, and other materials used with binders to form bituminous and portland cement concrete, macadam, mortar, and plaster; or alone as railroad ballast, filter beds, fluxing materials and scrubber stone. Aggregates greatly affect pavements and structural concrete, providing 30% of the cost and comprising by volume 65 to 85% of concrete and 92 to 96% of asphalt pavements. Natural aggregates are rocks and minerals, whereas manufactured aggregates include blast furnace slag and expanded clay or shale (lightweight aggregates). Aggregate mining results in pits, quarries and underground mines which must be reclaimed or stabilized. Significant investment is needed to find and process aggregates, but their use provides major economic impact. In the U.S. in 2000, quarry production yielded $8.7 billion, whereas sand and gravel provided $5.7 billion. Geologic challenges must be overcome during exploration for and exploitation of mineral aggregates. Geologic factors and restraints play important roles affecting economic extraction. Today, construction mining faces many challenges as the public is oblivious of its importance. Opposition to quarry/gravel operations near urbanized areas poses major obstacles. Noise, blasting, truck traffic and general nuisance are concerns. Yet, with their low value and high weight, aggregate sources must occur close to their use for economic reasons. Today, underground urban mines are preferred. In this paper, details of aggregate production, effects on human development, and current concerns will be considered.