Abstract
Dry lean concrete, a material in which concrete aggregates are used in mixes of very low workability and with a very low cement content, has gained wide acceptance as a base material in both concrete and bituminous surfaced pavements. These bases generally develop transverse cracks and in many cases they are reflected in the superimposed surfacing. In the preliminary part of the investigation, effort was directed towards establishing satisfactory techniques for producing specimens. The latter part is concerned with a study of some of the elastic properties in order that the resistance to cracking may be assessed. A laboratory study of one method of dealing with the crack problem, in which part of the mixing water is replaced with bitumen emulsion, has been undertaken. Furthermore, in an attempt to accentuate the effect of introducing bitumen, a technique of precoating the coarse aggregate with bitumen has been developed so as to localise bitumen as a thin film over the aggregate. The effectiveness of this technique is assessed on the basis of workinability, strength and elastic properties. The precoating technique, in particular, has significantly influenced the properties under consideration. Values are given for estimated stresses in bases for a typical wheel loading and compared with the strengths obtained on the types of dry lean concrete studied in this investigation. The thesis includes recommendations for further work.