LOW COST SURFACING LOW COST SURFACING APPROACHES IN ZIMBABWEAPPROACHES IN ZIMBABWE

CASE STUDY: Marondera - Musami Road CASE STUDY: Marondera - Musami Road Construction ProjectConstruction Project

K. MukuraK. Mukura

TRL LtdTRL Ltd

IntroductionIntroduction

Constructed in 1993-1994 periodConstructed in 1993-1994 period Before construction:Before construction:

22 km was narrow mat22 km was narrow mat 41 km was gravel road in poor 41 km was gravel road in poor

conditioncondition After construction:After construction:

22 km is narrow mat22 km is narrow mat 41 km is surfaced to a 7/8 standard41 km is surfaced to a 7/8 standard Low cost surfacing method was usedLow cost surfacing method was used

IntroductionIntroduction

Location: Location:

HARARE

CITY

Marondera-Musami Road

Marondera Town

Cross

To Mozambique

Malawi

MUTARE CITY

To Mozambique

Beira Port

63km

73km

60km

Construction StandardsConstruction Standards

Alignment:Alignment: closely followed the existing gravel closely followed the existing gravel

roadroad cuts and fills were designed by eyecuts and fills were designed by eye curvature was designed by eye curvature was designed by eye

except in complicated situationsexcept in complicated situations very sharp curves were acceptable very sharp curves were acceptable

to minimise coststo minimise costs Super-elevation was difficult to set Super-elevation was difficult to set

by eye by eye

Construction StandardsConstruction Standards

Pavement Design:Pavement Design: x-section: 7/8, 3% camber, 2m wide drains x-section: 7/8, 3% camber, 2m wide drains

( detour)( detour) 150mm sub-grade and base 1 thickness150mm sub-grade and base 1 thickness Compaction:Compaction:

Ls 91% HCE for sub-gradeLs 91% HCE for sub-grade Ls 93% HCE for base 1Ls 93% HCE for base 1

Materials specification:Materials specification: base 1: triaxial class 2.8, laterite & base 1: triaxial class 2.8, laterite &

decomposed granite sometimes marginaldecomposed granite sometimes marginal sub-grade: SG9sub-grade: SG9

Construction StandardsConstruction Standards

Pavement Design:Pavement Design: Surfacing: single sealSurfacing: single seal

10mm crushed stone @ 10x1010mm crushed stone @ 10x10-3-3m3/m2m3/m2 TP7 prime @ 0.9 litres/m2TP7 prime @ 0.9 litres/m2 bitumen 150/200 @ 1.2 litres/m2bitumen 150/200 @ 1.2 litres/m2

ObservationsObservations

Traffic:Traffic: traffic increased beyond design capacity of traffic increased beyond design capacity of

roadroad heavy to opted for the short cut bypassing heavy to opted for the short cut bypassing

Harare despite 22km of narrow matHarare despite 22km of narrow mat Pavement: Pavement:

still sound to date in spite of marginal still sound to date in spite of marginal materials used.materials used.

re-sealing was done after 5 years and the re-sealing was done after 5 years and the carriageway looks goodcarriageway looks good

Conclusion Conclusion

Most sealed rural roads in Zimbabwe have Most sealed rural roads in Zimbabwe have been over-designedbeen over-designed

Low-cost surfacing technique is used Low-cost surfacing technique is used widely now to upgrade rural roadswidely now to upgrade rural roads

Drainage system should be good enough Drainage system should be good enough to prevent water seeping into pavement to prevent water seeping into pavement