00473103

Component

http://onlinepubs.trb.org...1987/1106v1/1106v1-014.pdf

https://scholar.google.co...lilu&publication_year=1987

Specifications for aggregate surfacings in Ethiopia are based on plasticity and grading with a maximum aggregate size of 38 mm. Roads built to these specifications have performed well, but the cost of construction has usually been relatively high because it is often necessary to process the material through crushers and screening plants. The natural gravels, including weathered basalts, do not normally comply with aggregate surfacing specifications, but their abundance makes them a relatively cheap construction material. Two experimental roads were constructed in Ethiopia in a joint study by the Ethiopian Transport Construction Authority and the Transport and Road Research Laboratory of the United Kingdom to examine the possibility of using weathered basalt gravels as a surfacing material for unpaved roads. These experiments involved the study of gravels from several different sources under traffic levels that ranged from 30 to 175 vehicles per day. Test sections were placed on roads with different geometric characteristics so that their performance could be studied under a range of conditions. The performance of the materials was assessed in terms of resistance to deformation, rate of gravel loss, and deterioration of riding quality. These factors were related to the physical characteristics of the gravel, including any possible change with time, and to the traffic loads. The measurements of the road surface were based on optical levelling, which was used to monitor rutting, corrugations, and gravel loss. These standard measurements were supplemented by visual inspection to identify features such as surface texture or the development of potholes. Riding quality was measured with a vehicle-mounted bump integrator. Materials were tested by means of density measurements and grading checks. The results of the experiments have led to proposals for the use of weathered basalt gravels and have shown that crushing or screening is cost-effective to reduce oversized materal when used on roads with traffic levels greater than about 50 vehicles per day.

This paper appeared in Transportation Research Record N1106, Fourth International Conference on Low-Volume Roads, Volume 1. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Copyright © National Academy of Sciences. All rights reserved

00490258

pp 103-115

1987-8

Transportation Research Record

International Conference on Low Volume Roads, 4th, 1987, Ithaca, New York, USA

0309044545

Print

Figures (13) ; References (16) ; Tables (5)

Basalt coarse aggregates; Cost effectiveness; Costs; Crushing; Deformation; Geometric design; Gravel roads; Low volume roads; Performance; Physical properties; Riding qualities; Screenings; Test sections; Traffic loads; Unpaved roads; Weathered rock

Ethiopia

Design; Finance; Freight Transportation; Geotechnology; Highways; Pavements; I22: Design of Pavements, Railways and Guideways; I36: Aggregates

TRIS, TRB

Sep 30 1987 12:00AM