Calcrete in road construction - Bulletin

Abstract

The composition, distribution, origin, and age of South African calcretes are briefly reviewed and a simple classification suitable for engineering use described. Methods of searching for economic calcrete deposits and of testing calcretes for roadmaking are considered and it is concluded that special methods of locating these must be used and that precautions must be taken during testing if the best results are to be achieved. The engineering properties of calcretes and specifications for calcrete roads are dealt with in some detail. Depending on their stage of development, these materials range in properties from those of an almost useless powder to those of rock, and this and their unusual composition and mode of formation cause them to exhibit unusual and often beneficial properties. Depending on the actual stage of development reached, calcretes can be suitable and have been used for all classes of road material, including surfacing chips, base, subbase, gravel road wearing courses and concrete aggregate. Some of the usual soi I constants and grading requirements can be considerably relaxed when these materials are employed and significant economic benefit can result.