Application of Geology to Engineering Practice

Some years ago a group of geologists led by Professor C. R. Longwell of Yale University and Professor A. I . Levorsen of Stanford University proposed to honor Dr. Charles Peter Berkey, Newberry Professor Emeritus of Columbia University, for his life-long contributions in the field of engineering geology, by assembling and publishing a number of original papers each of which would deal with a special facet of the subject.
The Geological Society of America, through its President Dr. N. L. Bowen, appointed a committee to carry out this proposal and agreed to publish the symposium. Dr. W. O. Hotchkiss was duly appointed Chairman of a working group, among whom were Sidney Paige, W. S. Mead, J. P. Buwalda, and B. C. Moneymaker.
The authors, each selected for his particular knowledge in the field, have given generously of their time. I t was agreed that broad principles, rather than engineering or geologic detail, should be emphasized, but aside from this broad consideration each author was to prepare his material independently. To them all our thanks are due.
It is doubtful whether these papers need further introduction. Each is addressd to a technically trained audience and is planned to emphasize principles, rather than the minutiae of engineering and geologic practice. The title of the boor–The Application of Geology to Engineering Practice–is self-explanatory and is well understood by engineers and geologists.
Petrology of Concrete Affected by Cement-Aggregate Reaction
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Published:January 01, 1950
Abstract
The permanence of concrete in engineering structures is jeopardized where highalkali portland cement is used with aggregates containing opal, chalcedony, tridymite, intermediate to acidic volcanic rocks, or some phyllites. First recognized in 1938, deterioration caused by cement-aggregate reaction is characterized by cracking, expansion, and decline in strength and elasticity of the concrete. Petrographic and petrologic methods have contributed significantly to the investigation of cement-aggregate reaction. Microscopic criteria serve to distinguish between this and other types of deterioration. Petrographic examination of concrete aggregates can be used to predict their potential reactivity. Physical-chemical conditions contributing to the deterioration were explored by petrologic and geochemical methods. The mechanism by which reaction between rocks and minerals and the alkalies of cement causes this destruction is explained. Essentially i t consists of osmotic pressures produced by the formation and hydration of alkalic silica gels, which arise from interaction of alkalies and certain aggregates.
- aggregate
- calcium carbonate
- calcium sulfate
- cement materials
- chalcedony
- chemical reactions
- colloidal materials
- concrete
- construction materials
- cracks
- degradation
- elasticity
- engineering properties
- expansive materials
- framework silicates
- gels
- hydration
- mechanical properties
- mechanism
- microcracks
- opal
- osmosis
- petrography
- physicochemical properties
- reaction rims
- rock mechanics
- silica minerals
- silicates
- siliceous composition
- strength
- tridymite