Investigating the progression of transverse thermal cracking on Bituminous roads in Kampala

Abstract

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 K cpt 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.