Johnson's Materials of Construction

Johnson's Materials of Construction

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1918 edition. Excerpt: ...temperatures than the other broken stones. The granites also furnish a very good material for coarse aggregate. Both of these classes of rock are very desirable in road or floor construction, or on surfaces which are subjected to considerable abrasion. Oftentimes, however, these hard igneous rocks crush into elongated particles which cannot be closely compacted. Consequently maximum density cannot be secured in the concrete or mortar into which they are made. When such aggregate have very smooth cleavage planes, the mortar will not strongly adhere to the surfaces and the resulting concrete will be deficient in strength. In spite of these objections, however, these rocks form the most valuable class of crushed aggregates. Crushed dolomite and limestone are extensively used for coarse aggregate, and the hard varieties of these rocks form a good material for constructions requiring high strength. As a class, however, these aggregates have not as high resistance to fire or to abrasion as the traps and granites. Soft limestone is often very porous, and unless thoroughly wetted before mixing will weaken the strength of the surrounding mortar by absorbing water from it while the hardening process is going on. Limestones frequently contain large quantities of very fine dust which, in wet weather, coat the surfaces of the stones. If there is a large proportion of this dust in the coarse aggregate, and if a fine sand is being used, it may be necessary to screen out the dust in order to secure a concrete of high strength. However, if the sand is coarse, allowance may be made for this dust in proportioning. The stronger and more dense sandstones make a satisfactory coarse aggregate, but the soft varieties together with the shales and slates should...
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Product details

  • Paperback | 300 pages
  • 189 x 246 x 16mm | 540g
  • United States
  • English
  • black & white illustrations
  • 1236860381
  • 9781236860385