Combined investigation of Low-scale Fracture in Hydrated Cement and metal alloys Assessed by Nanoindentation and FIB

Abstract

This paper deals with an assessment of fracture properties of micro-level components of hydrated cement paste. Fracture energy and fracture toughness are studied by means of several experimental techniques at the micrometer scale. Nanoindentation is used as a primary tool for the material characterization. The work includes analysis of fracture mechanisms under the sharp indenter using focused ion beam (FIB) technology combined with scanning electron microscopy (SEM). Usual microscale approaches used in brittle solids are based on the observation of cracks from surface view after indentation. In this work, an energetic approach and decomposition of work of indentation into plastic and other parts is used instead. Based on cross sectioning of indents via FIB, several assumptions are done on the fracture area under the tip and semi-quantitative estimates of the low-scale fracture energy are performed for the cement paste components. Statistical deconvolution is applied to sort out the individual phase fracture properties.

Study On Interaction Between Fracture And Creep Of UHSC Using Microindentation Technique

“…ν i and ν IT are the Poisson's ratio of the indenter probe (0.2 for diamond) and the material (0.24 for cement paste) respectively. Energy method is useful technique to extract fracture toughness, when geometry of crack is unknown as well as multiple cracks are presented around indentation location [5]. In the classical energy method holding phase at the maximum load, during indentation cycle, has not been considered which overestimates the fracture toughness.…”

“…Researchers [3][4][5]42] have made efforts to investigate the fracture behavior that includes a holding phase. However in those studies, the creep response is subtracted or omitted [5,39], and the fracture toughness is estimated.…”

“…Researchers [3][4][5]42] have made efforts to investigate the fracture behavior that includes a holding phase. However in those studies, the creep response is subtracted or omitted [5,39], and the fracture toughness is estimated. Therefore to understand the interaction between fracture and creep, the occurrence of fracture during the creep phase was estimated.…”

“…Interaction between creep and fracture in normal strength concrete was investigated by various researchers [1][2][3][4][5][6]. However, research on creep-fracture interaction in Ultra High Strength Concrete (UHSC), i.e., concrete with 28-day compressive strength > 100MPa is scanty.…”

Microscale Tests of Cement Paste Performed with FIB and Nanoindentation

“…Standardly, the mechanical properties of the material are assessed from indentation response in a load-unload cycle [4]. Properties of cement constituents like elastic modulus, hardness or creep were studied by many author in the past [5][6][7][8][9]. In this research, nanoindenter is used as a loading tool for bending of micro-beams.…”