Adsorption isotherms of aliphatic-based superplasticizer in CFBC ash-Portland cement paste

摘要

This paper studies the adsorption isotherms of aliphatic-based superplasticizer in CFBC ash-cement pastes. UV-visible absorption spectroscopy was used to evaluate the adsorption isotherms. Results show that the adsorption of aliphatic-based superplasticizer in coal ash-Portland cement pastes can be characterized as a monolayer adsorption and described by the Langmuir adsorption model. CFBC ash-cement pastes possess higher adsorption ability than the Pulverized Coal Combustion (PCC) fly ash-cement pastes and the adsorption increases with the increase of ash replacement ratio. It is concluded that the high amount of unburnt carbon along with irregular shape and porous surface morphology of CFBC ashes leads to high adsorption of superplasticizer.