Modeling of Calcium Leaching from Cement Hydrates Coupled with Micro-Pore Formation

Abstract

A computational system for predicting the long-term degradation of cement hydrates due to calcium leaching is presented. The leaching of calcium ions from hardened cement hydrates is simulated as the multi-phase equilibrium of calcium in solid and liquid phases and their transport is formulated on the basis of thermodynamics. The time-dependent properties of cement hydrates associated with hydration, pore-structure development, and moisture transport are evaluated by integrating calcium leaching and statistical models of chemo-physics. The proposed model delivers reasonable predictions of calcium leaching in high-performance concrete with a low water-to-cement ratio as self-curing takes place.

Scale-Dependent ASR Expansion of Concrete and Its Prediction coupled with Silica Gel Generation and Migration

“…Figures 23b and 23c show the computed ASR expansion of concrete with and without the idealized leaching impact by solving the already verified multi-ion modeling (see Chapter 2, Nakarai et al 2006 andIshida 2014). As discussed in Chapter 3, the simulation of larger gel permeability (κ * =10 -18 ) brings about better correlation at the early age when amorphous phase of silica gel is thought be dominant like viscous liquid.…”

Enhanced Model and Simulation of Hydration Process of Blast Furnace Slag in Blended Cement

“…Moreover, the electrical charges on the surface of hydrates are influenced by the Ca/Si ratio. The surface of hydrates from Portland cement is usually positively charged (Elakneswaran et al 2009;Glasser 1992;Nakarai et al 2006). According to the research from Glasser (1992) , as the Ca/Si ratio decline, the electric charges become less positive, and when the Ca/Si ratio is lower than 1.2-1.3, the surface charge of C-S-H reverses to negative, and C-S-H tend to bind alkali cations.…”

Investigating temperature effect on degradation of well cement in HPHT carbonic acid environment

“…The interaction between pore fluid and cement matrix leads to dissolution of hydrated products (i.e portlandite and calcium silicate hydrates), thus decreasing its mechanical strength. At extremely high temperature, portlandite is less soluble (Nakarai, 2006); hence leaching is minimized and carbonation becomes the dominant process. This trend is consistent with results obtained from similar studies that were conducted at 10% CO 2 concentration which is discussed in the next paragraph.…”