CIEDE2000 colour difference formula for surface colour analysis of low-carbon grey and white portland cement pastes with high-volume GGBS replacement

Abstract

Abstract The global movement towards sustainable concrete is accelerating the adoption of low-carbon cement within the construction sector. Many engineering properties of low-carbon cement-based materials (CBMs) containing supplementary cementitious materials have been extensively studied and are well understood, but information regarding colour properties is limited. In this study, a colour analysis was conducted on cement paste incorporating ground granulated blast furnace slag (GGBS) as replacement material for ordinary Portland cement (OPC) and white Portland cement (WPC). The replacement levels were set at 0%, 30%, 50% and 70% by OPC or WPC volume. Results from CIEDE2000 colour difference formula (∆ E 00 ) showed that the water-cured WPC paste had highest colour uniformity (∆ E 00  = 0.10 ± 0.03), whereas the OPC paste had the lowest (∆ E 00  = 1.29 ± 0.76). GGBS addition increases the lightness ( L *) of the OPC paste but decreases the L * of the WPC paste at similar rates. The highest colour difference (∆ E 00 ) between a control mix (has only OPC or WPC) and mixes containing 70% GGBS was approximately 7. When red iron oxide pigment was added, the ∆ E 00 value dropped to approximately 3.7 for the WPC mix and 1.5 for the OPC mix. This result shows that a notable colour change was observed when Portland cement was replaced with high-volume GGBS in the cement pastes, but this colour difference was considerably reduced in pigmented mixtures. This interesting result reveals that in construction products, Portland cement can be replaced with high-volume GGBS without compromising the products’ surface colour.