The problem asks which parameters in the Elovich equation best capture early-age hydration kinetics. The options are: A. Reaction order, B. Diffusion coefficient, C. Pre-exponential factor, D. Nucleation rate, and E. Activation energy. We need to select at least two correct answers.

1. Problem Description

The problem asks which parameters in the Elovich equation best capture early-age hydration kinetics. The options are: A. Reaction order, B. Diffusion coefficient, C. Pre-exponential factor, D. Nucleation rate, and E. Activation energy. We need to select at least two correct answers.

2. Solution Steps

The Elovich equation is often used to describe the kinetics of chemisorption or heterogeneous catalytic reactions. The general form is:

$dq/dt = \alpha e^{-\beta q}$

where $q$ is the amount adsorbed at time $t$, and $\alpha$ and $\beta$ are constants. The parameters that are crucial in early-age hydration kinetics in cementitious materials are the pre-exponential factor and the activation energy which determine the rate of the reaction. Nucleation is an important aspect during the initial stages of hydration, influencing the overall reaction rate.

Therefore, the two parameters that would most directly capture early-age hydration kinetics in the Elovich equation are the pre-exponential factor and the activation energy.

3. Final Answer

C. Pre-exponential factor

E. Activation energy