2022 - Uganda - Thermal Cracking of Bituminous Pavements

Transverse thermal Cracking is one of the major distress modes manifesting in Uganda’s
bituminous pavements. It occurs when thermal stress builds up due temperature changes as result
of a series of hot and wet climatic conditions, and thus the tensile strength of the pavement is
exceeded (A. Shalaby, 1998). Failure of bituminous roads in Kampala has been partly attributed
towards failure to do adequate timely maintenance on these roads in Kampala reducing the service
life. This is attributed to the inability to detect paved road deterioration in time which starts with
the manifestation of cracks such as transverse cracking that propagates from the bottom to the top
of the pavement surface as a result of temperature changes. This research investigated the
progression of transverse thermal cracking on bituminous roads in Kampala. The Research was
carried out between March and September 2022. Relationships between Transverse Thermal
cracking and pavement surface age, for selected bituminous roads in Kampala, were established
based on field observations, HDM-4 model for initiation and progression of Transverse thermal
Cracking. The Following features were considered; number of transverse thermal cracks(No/Km),
time to initiation of Transverse thermal cracks(years), coefficient of Transverse Thermal cracking,
Construction Defects indicator for bituminous Surfacings, calibration factors for both initiation
and progression of transverse Thermal cracking, pavement surface age, time since crack initiation
to reach maximum number of cracks and fraction of analysis year in which transverse thermal
cracking progression applies. A Kcpt value of 2 was found to best represent the rate of progression
of transverse thermal cracks on Bituminous roads in Uganda. This means that the rate of transverse
thermal crack progression in Uganda is twice that predicted by the HDM-4 equation of prediction
of transverse thermal crack progression.