Effects of weathering on colour of concrete paving blocks

Concrete paving blocks are utilised in a variety of commercial, municipal and industrial applications. They are usually realized with a double concrete mix and the surface layer is coloured through the addition of pigments. However fading of the blocks caused by weathering due to climate and other factors is commonly observed and it will result in the loss of the esthetical requirements. In this paper the colour and micro-structural differences between new and weathered concrete paving blocks with different coloration were examined. The colour was measured by means of image analysis and spectrophotometry and comparable results between the two techniques were obtained. Colour differences between new and weathered concrete blocks were measured. Macro and micro structural analysis showed that site exposure altered the surface layer of hardened cement paste of the concrete block, which caused colour changes.