Environmental factors affecting thin concrete pavements

Abstract

An ultra-thin continuously reinforced concrete pavement (UTCRCP) has a thickness of less than 75 mm while thin concrete pavements has a thickness of less than 150 mm thickness. Both pavements are reinforced with steel reinforcement and/or steel fibres to strengthen the concrete in tension. These pavement layers placed over an existing asphalt surface to strengthen the pavement structure. The performance of these concrete pavements are dependent on the response of the concrete pavement to both environmental and traffic loading. Significant research has already been done on the effects of traffic loading on the performance of UTCRCP and limited research on the effect of environmental loading on thin concrete pavements (pavements with a thickness less than 150 mm thickness). Significant research on the effect of environmental loading on pavements of ordinary thickness (± 300 mm thickness) has already been conducted and due to the limited research done on the effect of environmental loading conditions on the behaviour of UTCRCP, this research studied the environmental factors effecting the performance of ordinary concrete pavements. This was done to determine the properties of concrete pavements that are of a main concern when considering their response to environmental loading. Literature points to the material properties and environmental conditions as being the predominant source of defects seen in pavements, which are further accentuated by traffic loading, leading to the premature failure of the concrete pavement. This study looked at the behaviour of thin continuously reinforced concrete pavement sections of 50, 75 and 100 mm thickness of two different concrete strengths in response to the ambient environmental conditions, to determine the effect of pavement thickness and material properties on the response of the pavements to environmental loading. These pavement sections were cast as being unrestrained to determine the strains that are experienced by the pavement and linked to the potential internal moment and internal stress development and curvature that would occur within a continuous concrete pavement. Concrete pavements were cast, by using concrete with and without supplementary cementitious material (SCM). The material properties of the concrete were measured to link the behaviour of the pavement section back to the material properties of the concrete. It was found that the environmental factor affecting the behaviour of the thin concrete pavements the most was precipitation, with the worst effect being seen in the concrete pavements not containing any SCM. The thermal effect on the behaviour of the thin pavements was minor with a ± 100 μƐ fluctuation in the strain readings being measured due to the heating and cooling of the concrete pavements. The worst effects of environmental loading were seen within the 75 mm thick concrete pavements, marking this a critical pavement thickness while the 50 mm thick pavements, on the other hand, performed the best with the lowest change in length, curvature and internal stresses and moment development within the concrete. The material properties were found to play a significant role in the behaviour of the concrete pavements. The addition of SCM to concrete produced concrete that was less water absorbent than concrete without SCM. Concrete containing SCM held on to moisture a lot stronger than concrete without SCM. This resulted in less shrinkage and less swelling of concrete containing SCM due to less moisture movement. It was found that by adding SCM to concrete, the pavement was not as sensitive to the environmental conditions the pavements were exposed to with less curvature and internal stresses and moment development within the concrete pavements.