Preparation And Characterization Of Coloured Concrete

With its excellent decorative effect,colored concrete has effectively solved the defects of single color and cold color of ordinary concrete,which has opened up a new way for the landscaping of roads and urban buildings.However,the addition of pigments will not only increase the cost of materials,but also affect the performance of concrete and restricts the wide application of colored concrete.Therefore,it is of great practical significance to study the influence of pigments on the properties of concrete and explore ways to reduce the cost of concrete dyeing.In this paper,the colored concrete was prepared by adding different pigments into the ordinary concrete,and the type?yellow,orange,red,green and blue?and content?5%,10%,15%,20%,25%?of pigments on the dyeing effect of concrete were evaluated by the colorimeter,and the best pigment content based on the effect of concrete dyeing was obtained.The effects of the type and content of pigments on the working performance and mechanical properties of concrete were studied by the slump and compressive strength and flexural strength.Immersion tests,CO₂ erosion tests and natural erosion tests were conducted to explore the color durability of colored concrete,and the influence mechanism of yellow and green pigments on the mechanical properties of concrete is analyzed by means of hydration heat test and XRD and SEM microscopic test.In order to reduce the dyeing cost of colored concrete,the coated colored concrete was prepared by coating process,and the interfacial adhesion and mechanical properties of the concrete were studied.Finally,the coating process was used to prepare colored rinding stone as an example,and the economic benefits of the coating process were analyzed.Color difference analysis of colored concrete shows that when the amount of red pigment is 15%and the other four kinds of pigments are 20%,the color of concrete is saturated,which determines that the best dosage of red pigment is 15%and the best addition of the other four kinds of pigments is 20%.The influence of pigments on the strength of concrete shows that yellow and orange pigments reduced the effective water to cement ratio of concrete because of water absorption,and increase their compressive and flexural strength.The surface active agent in the composition of blue and green pigment is introduced into the concrete in the mixing process of concrete to reduce the density of concrete,which leads to the reduction of compressive strength and flexural strength.The results of color durability test shows that the internal structure of yellow and orange concrete is more dense than blue and green concrete,therefore,under the condition of CO₂ and natural erosion,the color durability of yellow and orange concrete is better than that of blue and green concrete.The effect of pigment on the hydration mechanism of cement was analyzed by the hydration heat test and XRD test,in which yellow pigment provide nucleating sites for the formation of hydrated products,play the role of nucleation,promote the hydration of C₃S,accelerate the rate of hydration and exothermic and deepen the hydration degree.Because of the organic components of green pigment can package the cement particles,which hinders the hydration of cement,slows the rate of hydration heat and reduces the production of hydration products.The results of SEM test show that the density of the yellow concrete is better than that of the green concrete,therefore,the test results of hydration heat and XRD have also been verified.In the process of cladding molding process,the colored concrete coated with larger thickness is used as the outer cladding layer,which has better bond and mechanical properties,the coating process can reduce the dyeing cost greatly,and it has good economic benefit.