Micro‐reactors to Study Alite Hydration

Abstract

A new approach to study the early hydration reaction of alite is presented. It relies on milling micron-sized gaps into alite grains using a Focused Ion Beam. This provides for a "microreactor" in which hydration in confined conditions can be followed after introducing aqueous solutions of any desired composition. Hydration is followed by stopping the reaction at desired ages using solvent exchange and imaging the gaps using a Scanning Electron Microscope. These micro-reactors offer several advantages over conventional methods to monitor alite hydration. In particular, we can study the time evolution of dissolution in a reproducible manner using a setup that mimics particles in close contact. This paper presents this new methodology and applies it to studying the effects of solution composition and selected chemical admixtures on the dissolution of alite. New insights into the role of these factors are obtained and discussed.G. Scherer-contributing editor Manuscript No. 35925.

Use of micro-reactors to obtain new insights into the factors influencing tricalcium silicate dissolution

“…The effect of superplasticizers was studied by using a commercial superplasticizer (ACE 30; BASF SE, Ludwigshafen, Germany) and a synthesized, grafted, pure comb-type polycarboxylate superplasticizer (3PMA1000S, molecular weight 26,600 g/mol, side chain molecular weight 1000 g/mol, and carboxylic to ester groups ratio 3.2); the superplasticizer was synthesized by copolymerization of methoxy polyethylene glycol methacrylates and methacrylic acid (Sigma-Aldrich CO, St. Louis, MO), additional details of the characterization are presented elsewhere [24].…”

“…Solutions were prepared on a mass basis; details are presented elsewhere [24]. Aluminum was incorporated into solution using water-soluble sodium aluminate (N95% pure, VWR International, Radnor, PA).…”

“…The present study extends work published earlier using microreactors [23][24][25][26]. In those studies, micron-sized gaps were milled into alite grains using a focused ion beam and subsequently filled with solution to mimic hydration between grains in close contact.…”

“…Preparation of the gaps, hydration, and imaging was done in a similar manner as explained in detail earlier, and the method is summarized here [24]. C 3 S pellets were lightly ground using a mortar and pestle to obtain pieces about 0.1-0.5 mm in size, then a piece was placed on a flat rubber surface and a drop of liquid epoxy (EPO-TEK 301, Epoxy Technology, Inc., Billerica, MA) was dropped on it and left to harden overnight.…”

“…Results showed a strong support for the initial reaction being dissolution controlled, and that selected superplasticizers and retarders likely acted by slowing down dissolution. It was also shown that nucleation seeding with C\ \S\ \H works primarily by increasing growth, but does not affect dissolution significantly [24].…”