Rheological propeties of engineered cementitious composites containing fly ash

In this thesis, parameters of Engineered Cementitious Composites (ECC) design, which most possibly affecting the fresh, rheological and mechanical properties are investigated. An experimental program that contains thirty-six different mixtures was undertaken to evaluate the combined effect of following factors: water-binder (W/B), sand-binder (S/B), superplasticizer-binder (SP/B) ratios and maximum aggregate size (Dmax) for the purpose of more effectively realizing mechanical properties optimized through micromechanical design theory. Mini-slump, Marsh cone, rotational viscometer were used to evaluate fresh and rheological properties of ECC. Compressive strength and four-point bending tests were used for mechanical characteristics on the 28 days age ECC specimens. Test results indicate that W/B, S/B and SP/B parameters strongly affect the fresh, rheological and mechanical properties while Dmax only statistically effective on the mid-span beam deflection values of the ECC. The effects of studied parameter (W/B, S/B, SP/B and Dmax) were characterized and analyzed using regression models, which can identify the primary factors and their interactions on the measured properties. Statistically significant regression models were developed for mini slump, Marsh cone, yield stress, plastic viscosity, compressive strength, mid-span beam deflection, modulus of rupture as function of W/B, S/B, SP/B and Dmax. To find out the best possible ECC mixtue under the condition of this research concept for the desired workability and mechanical characteristics, a multi-objective optimization problem was defined and solved based on developed regression models.