Effect of clinker grinding aids on flow of cement-based materials

Grinding aids (GAs) are increasingly used during cement production to reduce energy consumption and/or optimize clinker factor. This paper seeks to assess the effect of such additions on variations in flow of cement pastes, including static yield stress (τ₀) and viscosity (η). Grinding tests were performed at fixed specific energy consumption (Ec) or Blaine cement fineness. For fixed Ec, tests have showed that the increase in cement fineness resulting from the addition of higher GA concentration leads to reduced flow and increased τ₀ and η values. Conversely, cement ground for fixed Blaine fineness exhibited an improvement in flowability together with reduction in τ₀ and η values. This was related to a dispersion effect of cement agglomerates in the presence of GA molecules. Special emphasis is placed throughout this paper regarding the effect of GAs on ASTM C465 requirements.