We choose in this work to use rheology to understand the role of cellulose ethers in render mortars and identify their mechanisms of action in a cement paste. We develop some protocols and their analysis to improve, from macroscopic measurements, our understanding of these molecules at a microscopic scale. We then extrapolate from our results the consequences of a change in amount, nature or chemical structure of the ether on the render mortar fresh properties. In a first part, we study the influence of ethers on the viscosity of a cement paste interstitial fluid and the effect of this viscosity on water retention. In a second part, we study the effect of cellulose ethers on the yield stress and critical deformation of cement pastes and the role of these rheological parameters on the properties of the render mortar. In a third part, we focus on the influence of cellulose ethers on the viscosity of cement pastes and the role of this parameter on the application easiness of the render mortar
