A report on detailed engineering design and monitoring of low cost sealing of up to 1.0 KM Bukedea-Kidongole Road from Gravel to Bituminous Standard in Bukedea Town Council, Bukedea District
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The expected performance and cost effectiveness of sealing a low volume Urban road network with appropriate alternatives 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, taking levels (cross sectional and longitudinal), traffic estimation, determination of in-situ sub-grade strength, environmental factors (Weinert number, N) and laboratory investigation of material properties for road layers. Based on general field investigations, the targeted project road typically carries less than 300 vehicles per day with MESA falling below 1 million cumulative equivalent standard axles (<1.0 MESA) for which appropriate sealing alternatives for the low-volume traffic roads apply. The materials studied are sub-grade soils whose results were processed using the UK 3.1 DCP software and gravel 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 38% for Bukedea-Kidongole road in Bukedea TC road equivalent to in-situ sub-grade class-S6, Weinert N =1.75 (N<4), traffic level LV2. The aggregates registered; ACV= 27% and FI = 31%. 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%, PI=24%, MDD=1.88kg/m3 and OMC=9.2% was registered. Hence the need for stabilization to achieve 45% CBR. 150mm base thickness with 45% CBR is the final specified pavement design 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 Single Surface Dressing with Quarry Dust Capping surfacing Option adopted for the road. These reduce on maintenance backlogs and can stimulate social and economic growth of the Country.