Study on properties of metakaolin-based cement paste coating and its application of adsorbing methylene blue in water

• The properties of metakaolin based cement paste coating and the effects of the metakaolin on removing methylene blue in water were investigated. • Metakaolin increased the adsorption capacity of the cement paste coating to methylene blue in water. • Metakaolin increased the thickness of the cement paste coating and improved the transition zone between the cement paste coating and the aggregate. Cement paste coating is closely related to the water purification performance of porous concrete. The properties of metakaolin (MK) based cement paste coating and the effects of the metakaolin on removing methylene blue in water were investigated. The results showed the fluidity of the cement paste decreased and the cohesiveness increased with increase of the content of MK. It is found that the MK promoted the hydration of cement, which not only refined the pore structure of the cement paste, but also improved the interface transition zone. Besides, MK increased the adsorption capacity of the cement paste coating to methylene blue in water. The results showed that the content of MK is an important factor for affecting the methylene blue removal rate of the cement paste coating. Under the same MK content, the thickness of the cement paste coating had little positive effect on the methylene blue removal rate of the cement paste coating. The study is expected to provide a new approach for preparing cement paste coating with good methylene blue removal.