The pore solution of blended cements: a review

Abstract

This paper is the work of working group 3 of the RILEM Technical Committee on Hydration and Microstructure of Concrete with SCM (TC 238-SCM). The pore solution is an essential but often overlooked part of hydrated cements. The composition of the cement pore solution reflects the ongoing hydration processes and determines which solid phases are stable and may precipitate, and which phases are unstable and may dissolve. The study of the cement pore solution therefore contributes to the understanding of the mechanisms as well as of the kinetics of cement hydration. This paper reviews the impact of supplementary cementitious materials (SCMs) on the pore solution composition of blended cements. In a first part, the extraction and analysis methods of cement pore solutions are reviewed, leading to a set of practical guidelines and recommendations. In a second part, an extensive literature survey is used to document the effect of the addition of SCMs (blast furnace slag, fly ash and silica fume) on the pore solution. Finally, in a third part the collected literature data are compared to thermodynamic simulations. The performance and current limitations of thermodynamic modelling of blended cement hydration are demonstrated and discussed in view of future progress.

The steel–concrete interface

“…A recent paper [64] reviews the 5-14 and that the free alkali content is the main factor controlling pH. Generally, the alkali content decreases with increasing replacement of Portland cement (PC) by SCMs.…”

Improved Concrete Materials with Hydrogel-Based Internal Curing Agents

“…The implicit assumption is made that the hydrogels are chemically inert within concrete materials. As shown in Figure 1, this assumption is not true for most hydrogels due to the interactions of the polyelectrolyte molecules that form the internal network of the hydrogel with mono-and multivalent ions that are naturally present in cementitious mixtures, including sodium, potassium, and calcium [23]. It has recently been shown [24] that a great deal more attention must be paid to the chemical structure as well as the method used for evaluating the swelling capacity of hydrogels when they are to be used as internal curing agents for concrete.…”

“…However, it is these same negative charges that can electrostatically interact with the various mono-and multivalent cations [29][30][31] (e.g.,sodium, potassium, calcium) that are naturally found inside fresh cement mixtures as a result of the hydration reaction [23]. Figure 1 details the hydrogel network collapse (reduction in mesh size) that occurs as the polymer network coordinates with several types of counterions.…”

Ultrasonic Techniques for Air Void Size Distribution and Property Evaluation in Both Early-Age and Hardened Concrete Samples

“…The raising of electrical resistivity can be generated from the decreasing of ion concentration in pore solution and the decline of concrete connectivity. Based on reference [40], the ion concentrations in concrete pore solution become relatively stable after Day 7. Hence the obvious increase in electrical resistivity from Day 7-28 can be mainly generated from the declining connectivity.…”