Characterizing Strength and Failure of Calcium Silicate Hydrate Aggregates in Cement Paste under Micropillar Compression

Abstract

A new methodology is proposed for investigating compressive failure behavior of cement paste at the micrometer scale. Micropillar geometries are fabricated by focused ion-beam milling on potential calcium-silicate-hydrate (C-S-H) locations identified through energy dispersive spectroscopy (EDS) spot analysis. Uniaxial compression testing of these pillars is performed using nanoindentation equipment. The compressive strength of C-S-H aggregates (225-606 MPa) measured from microcompression tests is found to be consistent with values from multiscale damage and molecular dynamic models. From posttest images, two primary deformation mechanisms at failure were identified; axial splitting and plastic collapse of the entire sample were observed.

Experimentally informed fracture modelling of interfacial transition zone at micro-scale

“…cement paste prepared with the identical w/c ratio (0.3) [47]. The hydration degree is quite close to the results (63.0%) reported by Haecker et al [39] using non-evaporable water content method. Due to the limitation of image resolution, pores smaller than 2 mm are not detectable and are mixed within the segmented solid phases [40][41][42].…”

“…Recent reports document the utilization of nanoindenter as a versatile instrument for loading micrometre sized specimens [37][38][39][40][41][42][43]. The specimens can be prepared either by a focused ion beam (FIB) milling technique [37][38][39] or physical micro-dicing procedure [40][41][42][43]. The FIB milling technique uses a focused Ga-ion beam for precise micromachining of various materials to fabricate specimens with designed geometries, typically the micro-cantilever [37,38] and micro-pillar [39].…”

“…The specimens can be prepared either by a focused ion beam (FIB) milling technique [37][38][39] or physical micro-dicing procedure [40][41][42][43]. The FIB milling technique uses a focused Ga-ion beam for precise micromachining of various materials to fabricate specimens with designed geometries, typically the micro-cantilever [37,38] and micro-pillar [39]. However, considering the relatively low milling efficiency, the size of the machined specimen is generally limited up to 10 μm, which is not large enough to represent the HCP matrix but for a single phase in https://doi.org/10.1016/j.cemconcomp.2019.103383 Received 27 March 2019; Received in revised form 1 July 2019; Accepted 30 July 2019 the matrix.…”

Combined experimental and numerical study of uniaxial compression failure of hardened cement paste at micrometre length scale

“…On the other hand, a large scatter is observed as a result of the heterogeneity of such material and small volume of material sampled. Recently, Shahrin et al [9] has prepared micro-pillar of C-S-H specimens (around a few micrometres) using FIB technique and measured their compressive strengths. The measured compressive strength of 10C-S-H specimens varies from 225 MPa to 606 MPa.…”

“…Loading of these micrometre sized specimens is generally applied using a nanoindenter. Most common tests include the micro-pillar compression [9] and micro cantilever bending tests [10,11]. In this work, the nanoindenter was adopted as well.…”