Graduate Assistant: Prasanth Tanikella Faculty Advisor: Jan Olek

1. 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 Proposed approach to estimate synergic action (1) 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 • Efficiency factors • Efficiency factor for compressive strength • Efficiency factor to determine the pozzolanic effect of the admixtures • k = (ГSWS,P/WS,C)(1-aW/C) • Quantification of Synergic action • Synergic Action (SA) • SA = P(Tf+Tm) – (WfPTf + Wm PTm) • Strength Gain (SG) • SGi = Ri – (Rc.Ccem) • Cpoz • where, • fc’ – compressive strength • K – constant which depends on cement type • W,C,P – Water ,Cement and Fly ash contents respectively • k – efficiency factors • ГS – Weight fraction of SiO2 in secondary cementitious materials (SCM) • WS,P & WS,C- Weight fraction of silica in SCM and cement respectively • PTi – measured compressive strengths of the system • Wi – 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 • Ccem & Cpoz – 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) 877-885 • 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 Research Objectives • 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 Characterization of selected fly ashes • 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 Summary • 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