Construction of urban roads using low-cost sealing Technology in Soroti Municipality

Abstract

Based on general field investigations, the targeted project road typically carries less than 300 vehicles per day with MESA confirmed falling below 1 million cumulative equivalent standard axles (<1.0 MESA) for which appropriate sealing technology for the low-volume traffic roads applies. The expected performance and cost effectiveness of sealing a low volume District Road Network with appropriate seals adopted for the project are un-comparable with conventional highly capital-intensive approaches that are not affordable by most District Local Governments and Urban Councils in Uganda. The adopted design approach in this case involves; carrying out road condition surveys, traffic estimation, and determination of in-situ sub-grade strength, environmental factors (Weinert number, N) and laboratory investigation of material properties for road layers. The materials studied are sub-grade soils whose results were processed using the UK 3.1 DCP software, in-situ soil tests, gravel tests whose engineering properties were determined in the laboratory such as; gradation, California Bearing Ratio and Atterberg Limit tests. The aggregates were analyzed using standard procedures for Gradation (BS 1377: Part 2:1990), ACV (BS 812: Part 110:1990), FI (BS 812: Section 105.1:1989) and LAA (ASTM C-131-89). The AIV test on aggregates (BS 812: Part 112:1990) was not conducted. The road layers were designed based on sub-grade strength with a 10 %tile CBR of 18% for Oumo, Opiyai and Mosque Road equivalent to in-situ sub-grade class-S5, Weinert N =1.75 (N<4), traffic level LV5. The aggregates registered; ACV= 22% and FI = 22%. The aggregates were found to be suitable for surfacing and hence no need for alternative source. Borrow Pit 1 (BP 1) Gravel 3 point soaked CBR= 27 at 95% MDD% (Max), PI=20%, MDD=1.92kg/m3. Hence the need for stabilization to achieve 55% base CBR. 120mm sub-base thickness with 30% CBR and 150mm base thickness with 55% CBR are the final specified pavement designs and low-cost wearing course for surface dressing was designed using the surfacing parameters outlined above. Finally, this design recommends that Low-Cost Design approach (innovation to design for fitness) be adopted as an alternative to re–gravelling and traditional bituminous surfacing with Premix (Cold Asphalt) surfacing Option adopted for the road. These reduce on maintenance backlogs and can stimulate social and economic growth of the Country.