The coefficient of friction is a quantity indicates the ratio of frictional force between objects. As pavement experiences thermal changes, it may slide against supporting subbase resistance. This resistance must be determined in order for pavement to perform as anticipated. Cracking of concrete does not occur if the pavement is jointed. In the joint plain concrete pavements, A separator layer is installed between the subbase and the plate to smooth the interface. A smooth surface shows less resistance to the concrete’s displacement caused by temperature difference. Two stages of the push-off test were conducted for subbase conditions (smooth and rough). Friction properties among the concrete and subbase were investigated based on the friction test results. The results show the parameters impacting the maximum coefficient of friction and displacement (interface condition, movement rate, thickness) respectively for friction and (movement rate, interface condition, thickness) for displacement. In conclusion, the frictional force rises significantly until the applied force reaches the stable condition. This force is affected by interface condition, which has the most significant impact, followed by movement rate and thickness. Changing conditions from smoother to rougher interface leads to raising maximum coefficient of friction regardless of changing slab thickness or movement rate.
The coefficient of friction is a measurement of the frictional force between two objects. As the temperature of the pavement changes, it might slide against the resistance of the supporting subbase. In order for pavement to perform as anticipated, this resistance must be calculated. Concrete cracking does not occur when the pavement is joined. A membrane layer is positioned between the subbase and the plate in joint plain concrete pavements to smooth the interface. The displacement of concrete caused by temperature differences is less resistant on a smooth surface. For subbase conditions, two stages of the push-off test were performed (smooth and rough) to show the effects of movement cycles. Based on the results of the friction tests, the friction properties of the concrete and subbase were investigated. The parameters that influence the coefficient of friction and displacement are (interface state, movement rate, thickness number of movement cycles), changing the interface condition from smooth to rough leads to an increase the FRF of (6, 9 and 12 cm/hr) by (194.7, 194.4 and 189.8 %) respectively. Finally, once the applied force reaches a stable state, the frictional force increases dramatically. The most important influence on this force is the interface state, which is accompanied by movement rate and thickness. The variation of the relationship curves with number of cycles tends to be insignificant after the third to fourth cycle of slab movement.
The frictional forces between the concrete slab and base has been combined with the movements of the horizontal slab that have been induced by variations of the moisture and temperature in concrete slabs. The frictional drag that acts on the slab bottom as a result of base friction is in an opposite horizontal slab displacement direction, and resist movements of the horizontal slab. A condition of smoother interface provides lower resistance to slab movement. On the other hand, rough interfaces are beneficial in the reduction of the load-related stresses. As bonding degree between slab and foundation affects the friction that has been mobilized at interface, a realistic evaluation of friction of the interface is required for the rational designs of the concrete pavement. In this work, push-off test has been performed. Based upon results of the friction tests, the friction characteristics of concrete and soil have been researched. The parameters that influence the maximal displacement and friction coefficient are (interface state, rate of movement) for friction and (rate of movement, interface condition) for the displacements, respectively. Finally, once the applied force reaches a stable state, the frictional force increases dramatically. The most important influence on this force is the interface state, which is accompanied by movement rate. The change of the interface from a smooth to a rough surface increases the overall coefficient of friction.
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