Performance evaluation of pigmented fair-faced concrete under various environments: Mechanical properties, apparent properties, and color stability

Fair-faced concrete is green concrete that is directly decorated by its texture. For a more stunning visual impact, pigmented fair-faced concrete with more colors on the surface is prepared. However, the effects of different pigments and service environments on pigmented fair-faced concrete need to be explored. Therefore, four iron oxide inorganic pigments were employed to prepare pigmented fair-faced concrete, and the changes in its fresh properties and mechanical properties were studied through slump, slump flow, and compressive strength tests. Meanwhile, camera analysis and colorimetry were utilized to evaluate the changes in its apparent properties and color stability under four different distinct service environments in this experiment. Results indicate that incorporating pigments reduces both the slump and slump flow of the fresh mixture, and its fresh properties gradually decrease as the pigment content increases. The slump and slump flow of concrete with 6 % iron oxide yellow (IOY) were 30.00 % and 44.00 % lower than the control. Adding IOY and iron oxide red (IOR) can improve the 7-d and 28-d compressive strength of concretes. The 28-d compressive strength of concrete with 2 %-6 % IOY increased by 7.72 %, 11.78 % and 15.09 % over the control. Meanwhile, the surface pore area of concrete with IOY is the lowest and that of concrete containing 2 % IOY is 3.97 cm2/m2. Additionally, the color stability of concrete performs best in water immersion environments and worst in natural environments. It is noteworthy that the concrete added with IOY exhibits excellent color stability under all four service environments. This study aims to evaluate the effects of different pigments on concrete properties and investigate the color stability of four types of concrete under diverse service conditions. The findings will promote the application of pigmented fair-faced concrete in construction and provide technical insights for future research.