Incorporation of physical and chemical properties of fly ash in modeling hydration of ternary cementitious binders Graduate Assistant: Prasanth Tanikella Faculty Advisor: Jan Olek Introduction Research Objectives Summary Modeling of hydration of cement Traditional products of hydration of cement include calcium silicate hydrate, calcium hydroxide, AFm and Aft phases and hydrogarnet Depending on the type of fly ash used, addition of these pozzolanic materials alters the kinetics of hydration as well as the amounts and composition of the hydrated products The influence of chemical and physical characteristics of fly ashes on the synergistic effects in ternary binders will be evaluated Modification of CEMHYD3D model will be attempted using fly ash characterization information obtained from this project The focus of the present research is on studying and modeling the influence of variations in chemical composition of fly ashes on potential synergistic effects in ternary (cement + slag/silica fume + fly ash or cement + 2 different fly ashes) cementitious systems To explore the feasibility of modifying the CEMHYD3D program (Fig 1) to account for the use of fly ashes with particular chemical compositions in ternary cementitious systems Fig 1 : 3D rendition of hydrated particles using CEMHYD3D Fly ashes (both class C and class F) selected from 20 sources commercially available in Indiana Properties evaluated -Total Chemical Analysis -Particle Size Distribution -Magnetic particle content -X-Ray diffraction analysis -Scanning electron microscopy -Strength activity index Hydration properties of ternary binder systems modeled using CEMHYD3D Steps in hydration modeling -Creation of a 3D microstructure -Simulation of hydration and microstructure development (this includes hydration kinetics and chemistry, temperature and curing conditions -Virtual testing of the resulting microstructure Modeling of fly ash in ternary binders  CEMHYD3D is equipped with modeling the effects of incorporation of fly ash in the binder  The hydration reactions in the presence of fly ash in cement are identified and the volumetric stoichiometries on a pixel basis are used  Pozzolanic properties, the activation energies of the reactions and pH of the solution are accounted for  Present model is limited in the availability of data to model the synergistic effects of fly ash in ternary binders Characterization of selected fly ashes Proposed approach to estimate synergic action (1) Efficiency factors Efficiency factor for compressive strength Efficiency factor to determine the pozzolanic effect of the admixtures k = (Г S W S,P /W S,C )(1-aW/C) Quantification of Synergic action Synergic Action (SA) SA = P (Tf+Tm) – (W f P Tf + W m P Tm ) Strength Gain (SG) SG i = R i – (R c.C cem ) C poz where, fc’ – compressive strength K – constant which depends on cement type W,C,P – Water,Cement and Fly ash contents respectively k – efficiency factors Г S – Weight fraction of SiO 2 in secondary cementitious materials (SCM) W S,P & W S,C - Weight fraction of silica in SCM and cement respectively P Ti – measured compressive strengths of the system W i – weight proportion of ash in the blend Ri – compressive strength of the specimen at a given age Rc – compressive strength of the reference at the same age C cem & C poz – proportions by weight of cement and sum of cement and pozzolan in each mixture respectively Fig 2: SG versus SA values for ternary cements Synergic action is known to be affected by curing time and temperature in the form of the constant ‘a’ (1) S.K. Antiohos et al. / Cement and Concrete Research 37 (2007)