Influence of Surface Scaling on the Performance of Cement Concrete Roads
Dr. Rakesh Kumar, Principal Scientist, Rigid Pavements Division, CSIR-Central Road Research Institute (CRRI), Mathura Road, New Delhi
A well designed and properly constructed cement concrete road generally outperforms the structural and functional performance parameters set for it. On the other hand, premature distresses such as surface defects i.e. scaling, pop-outs, crazing, map cracking, loss of texture etc, and structural cracks are not very uncommon on a newly constructed cement concrete road. Among all the surface defects of newly constructed cement concrete road, the scaling draws a quick attention of the road users as well as road authorities. Scaling of a concrete surface is defined as the loss of surface mortar and mortar surrounding the aggregate particles (Figures 1-3). It is deterioration of the upper concrete slab surface. Scaling may occur anywhere over the pavement slab [Miller and Bellinger, 2003]. As shown in the figures 1-3, the aggregate is usually exposed and often stand out from the concrete. Normally the depth of scaling varies from 3 mm to 13 mm [FHWA-HRT-13-092, 2014, N.J. Delatte 2014, ACI 224.1R]. Scaled concrete surface gives a very ugly look of the concrete slab (Figure 1). It is measured as the square meters of affected area. Light scaling does not expose the aggregate. In moderate scaling, the aggregate are exposed and the mortar loss depth may be 3 to 10 mm. But, in case of severe scaling, more surface areas are lost and the aggregate is clearly exposed and projected from the surface. Severe scaling of a pavement slab is considered as a type of functional distress as it affects riding quality and safety of the traffic. It is common to observe scaling problem of varying severity in several pavement slabs. Such situation reduces the riding comfort and increase a chance of accident due to sudden application of break or for lowering the speed of a moving vehicle at a high speed.
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NBM&CW March 2018