MICROSCOPIC AND X-RAY DIFFRACTION EXAMINATION OF BASALT TO DETERMINE FACTORS AFFECTING DURABILITY

摘要

Similar mineralogy and textures exist in the basaltic rock studied from four quarries in the Nestucca River area of northwestern Oregon. However, durability of the aggregates manufactured from these quarries differs greatly. This study, done by petrographic and X-ray analysis shows that no new minerals form during degradation. Existing clays such as nontronite, increase in percentage as degradation progresses. In contrast degradation did not occur in rocks containing analcite, a mineral which forms under conditions unfavorable to the formation of nontronite. It was also found that durability cannot be determined solely by percentages of weathering products found in the rocks as some studies have suggested.