Repair mortar colour matching by colourimetric method

摘要

With concrete facades often used as architectural features, it is important to match the colour of a concrete repair patch on such structures with that of the surrounding concrete. Fine-tuning the colour of a patch repair mortar is problematic and no rigorous method is available to perform exact colour matching. Two specific, but independent factors affect the colour and appearance of concrete. The first deals with mortar mix design and the second with the actual application or patching process. This paper reports on some preliminary research aimed at establishing guidelines as to the percentage of white or grey cement that should be added to a patching mortar to approximate the surrounding concrete colour. As a result of this research work, a starting point for calculating the mix proportions for colour matched patching mortar has been obtained. The colourimetric method used in this research work allows accurate colour measurements as well as measurements of the time-dependant colour changing of concrete. Through the analysis of the colourimetric value (ΔE), two new coefficients are introduced by the authors. These are the colour coefficient and the colour influence coefficient, which together allow for a clearer picture with regard to the colour and the change of colour in architectural concrete. With the help of these two coefficients, designers can analyse the colourimetric value of concrete surfaces, and thereby more effectively manipulate the colour and appearance of the patching mortar mix design.