Creep properties of cement and alkali activated fly ash materials using nanoindentation technique

Abstract

This paper presents creep properties of cement and alkali activated fly ash (AAFA) paste and mortar determined from statistical analysis of nanoindentation data. Cement paste having 95 MPa compressive strength at 28 days was tested for comparison and validation with a conventional test. Using nanoindentation, the specific creep of the cement paste after one year was predicted as 18.32 microstrain/MPa. For AAFA samples, an experimental program was set up using Taguchi's Design of Experiment method to consider four parameters, silica fume, sand to binder ratio, liquid to solid ratio, and superplasticiser, each with three variations.Using ANOVA, the percentage contributions of these parameters on the creep modulus of AAFA samples are: silica fume 26%, sand to binder ratio 21%, liquid to solid ratio 22%, and superplasticiser 31%. The results using deconvolution technique to identify the creep modulus of different phases of AAFA matrices show that partly-activated, non-activated slag and non-activated compact glass phases are leading the creep behaviour of AAFA samples due to their high creep modulus. Compare to other parameters, the liquid to solid ratio contributes the most to the creep property of partly-activated slag, non-activated slag and non-activated compact glass phases, that is, 51%, materials are such as blended cement, alkali-activated pozzolan cement, and Geopolymer. This paper presents the creep properties of some of these materials and how different compositions in the mixtures are affecting their creep properties. The main aim is to obtain the optimum mix design, within the range of the parameters considered, for the minimum creep behaviour.15The measurement of viscoelastic properties of a material can be obtained by considering the nature and the rate of configurational rearrangements and the interaction of the properties. Creep testing involves applying a constant instan-

Cohesive-strength homogenisation model of porous and non-porous materials using linear comparison composites and application

“…In the present work, the microstructure of the two-phase composite will be represented by a spherical inclusion. The results from the use of linear micromechanics 13 to obtain the homogenised bulk and shear modulus can be found in Part A of the Supplementary Information. The classic yield function of Drucker-Prager is defined by the mean stress σ σ = 1/3tr( ) m and stress invariance σ = s s (1/2) : d with s = σ − σ m 1 as:…”

“…he present results show that even though M1 and M2 matrices have the same mix design, Level 0 (solid) properties are not consistent to each other. It is believed that the development of calcium silicate hydrated (CSH) which is one of major hydration products of cementitious matrix contributing to the primary source of nanometre-scale elastic modulus degradation 13,18 . In fact that the nanostructure of CSH is still not known, forms poorly crystalline during the hydration of the cementitious matrix and characterised by extensive atomic imperfection and structural variations at…”

An Investigation of Nanomechanical Properties of Materials using Nanoindentation and Artificial Neural Network

“…The indenter’s angle was a contributing unknown, thus, the inverse analysis could be used to further investigate the effect of the surface roughness and the contact areas of the tested samples. The hydration products of OPC paste contain five major phases, which are capillary porosity, low-density calcium silicate hydrated (LD CSH), high calcium silicate hydrate (HD CSH), Portlandite (CH) and clinker with calcium silicate hydrated (CSH) 32,33 . It has been evident 32–35 that calcium silicate hydrated (CSH) is a governing component contributing to its fundamental properties, such as strength, relaxation, creep and fracture behaviours.…”

On Phase Identification of Hardened Cement Pastes by Combined Nanoindentation and Mercury Intrusion Method

“…Hardened cement pastes can be regarded as composites consisting of phases with different mechanical properties on both micro and nanoscale. The composition and micro-mechanical properties of hardened cement paste influence concrete macro-mechanical properties and durability [ 1 , 2 ]. Nanoindentation technology can be used to obtain the mechanical properties of cement clinker and the micromechanical properties of hydration products and porosity.…”

“…After the data sets of different mechanical properties are obtained, the types of phases and the statistical characteristics of mechanical properties of each phase can be further obtained. Lee [ 2 ] investigated the creep properties of cement and alkali-activated fly ash paste and mortar determined from statistical analysis of nanoindentation data. Based on the principle of statistical nanoindentation, many scholars have carried out a series of research.…”