Evaluation of bituminous mixes in pavement structures interim report V - A study of transverse cracking in Oklahoma flexible highway pavements

Abstract

Field and laboratory studies were made to investigate the nature and extent of transverse cracks on Oklahoma flexible pavements and to determine the possible causes of this form of distress. Only the influence and contribution to this type of cracking from the bituminous components of the pavements were considered. Nine test sites on State and Interstate highway sections were studied. Examinations of field cores showed that newly developed transverse cracks did not extend through the pavement matrix and supported the concept that such cracks are caused by tensile forces developed at low temperatures. Tensile properties of core sample specimens at o0 , -5° and -10° were determined using a tensile splitting test. Use was made of the "stiffness modulus" concept in characterizing·the behavior of the recovered asphalt binders and the paving mixtures from the cores. A satisfactory correlation was found between the tensile splitting test results and the cracking indices of the test site pavements. That is, cracking was more pronounced as the failure strains of the samples decreased and the failure stiffness increased. Stiffness moduli of the recovered asphalts also was significantly correlated with the cracking indices. The stiffer or harder the asphalt cement in a pavement the greater was the degree of transverse cracking.