LOW COST SURFACING APPROACHES IN ZIMBABWE CASE STUDY: Marondera - Musami Road Construction Project K. Mukura TRL Ltd

Introduction  Constructed in period  Before construction:  22 km was narrow mat  41 km was gravel road in poor condition  After construction:  22 km is narrow mat  41 km is surfaced to a 7/8 standard  Low cost surfacing method was used

Introduction  Location: HARARE CITY Marondera- Musami Road Marondera Town Cross To Mozambique Malawi MUTARE CITY To Mozambique Beira Port 63km 73km 60km

Construction Standards  Alignment:  closely followed the existing gravel road  cuts and fills were designed by eye  curvature was designed by eye except in complicated situations  very sharp curves were acceptable to minimise costs  Super-elevation was difficult to set by eye

Construction Standards  Pavement Design:  x-section: 7/8, 3% camber, 2m wide drains ( detour)  150mm sub-grade and base 1 thickness  Compaction:  Ls 91% HCE for sub-grade  Ls 93% HCE for base 1  Materials specification:  base 1: triaxial class 2.8, laterite & decomposed granite sometimes marginal  sub-grade: SG9

Construction Standards  Pavement Design:  Surfacing: single seal  10mm crushed 10x10 -3 m3/m2  TP7 0.9 litres/m2  bitumen 1.2 litres/m2

Observations  Traffic:  traffic increased beyond design capacity of road  heavy to opted for the short cut bypassing Harare despite 22km of narrow mat  Pavement:  still sound to date in spite of marginal materials used.  re-sealing was done after 5 years and the carriageway looks good

Conclusion  Most sealed rural roads in Zimbabwe have been over-designed  Low-cost surfacing technique is used widely now to upgrade rural roads  Drainage system should be good enough to prevent water seeping into pavement