Molecular design of comb-shaped polycarboxylate dispersants for environmentally friendly concrete

Abstract

Concrete is the most widely used material in the world and, because of the large volume used, the production of cement, the main component of concrete, is responsible for a high CO₂ emission. To reduce the quantity of CO₂ emitted, one solution is to substitute a part of cement by supplementary cementitious materials, SCMs, such as fly ash. Because fly ash is largely inert in the first days of blended cement hydration, it is necessary to accelerate its dissolution by physical or chemical means to compensate the loss of mechanical strength in the early stage. The solution studied in this project is the alkaline activation by addition of NaOH that prevents the dispersive effect of PCE superplasticizers used in modern concrete with a low content of water. In this work, we investigated the influence of NaOH on hydration, rheology and mechanical strength of superplasticized blended cementitious systems. From the results and theoretical aspects of polymer adsorption, a simple criterion was established that defines which polymer structures are or are not compatible with alkaline activated systems.