Application of the nanoindentation method in assessing of properties of cement composites modified with silica-magnetite nanostructures (original) (raw)
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Properties of Cement Composites Modified with Silica-magnetite Nanostructures
Procedia Engineering, 2017
The results of investigation of the cement composites modified with 5% of silica-magnetite nanostructures of the core-shell type are presented in the paper. The nanoindentation method employing three-sided pyramidal Berkovich indenter was used in the research. The mechanical properties and microstructure of the modified cement composites were evaluated on the basis of the values of hardness and indentation modulus measured inside the cement matrix and in the aggregate-paste interfacial zone. The results were compared with those obtained for the reference composites without nanostructures. The positive influence of the presence of silica-magnetite nanoparticles on the tested properties was found out.
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Nanoindentation technique is employed for evaluation of mechanical properties of homogeneous materials at micro-level. Many engineering materials, especially cement and concrete composites, which are extensively used as building materials, exhibit phase heterogeneity and are highly porous. The presence of pores highly influences the response obtained from nanoindentation tests. In this study, mechanical properties of Calcium-Silicate-Hydrate (C-S-H), the primary binding agent in cementitious composites, are investigated using a simulated nanoindentation technique. The influence of presence of pores and its geometrical distribution on the non-linear response of C-S-H phases and the stress distribution are critically analysed.
Nanoindentation mapping of mechanical properties of cement paste and natural rocks
Materials Characterization, 2007
This paper reports a study to assess nanoindentation mapping of mechanical properties of cement paste and natural rocks. Initial work seems to show that mechanical property mapping by nanoindentation is feasible and can be related to microscopic information. Further work is however required on the effect of indent size and spacing. Such a testing technique can be very useful for materials with different phases to study the intrinsic properties of each component, and also the interaction and properties of the interfacial regions of different phases. The values of Young's modulus and hardness of the individual mineral phases were also determined by statistically analysing a large number of experimental data.
Nanomechanical properties of cement paste
Riem Revista Ibracon De Estruturas E Materiais, 2011
Understanding the influence of each phase of concrete, among which cement paste deserves prominence, is important for the development of a more efficient concrete, with an improved hydration process and resistance to plastic shrinkage cracks. The elastic modulus of the concrete is one of the main project parameters of structures and it has extensive influence on the speed of the construction process and the durability of structures. The capacity for deformation of the concrete depends on the intrinsic characteristics of the cement hydration products, aggregates, transition zone and pores, besides variables inherent to the process, including the speed of hydration and climatic conditions. The aim of this research was to analyze the mechanical properties of the elastic modulus and hardness of a cement paste, through the nanoindentation technique, and compare these using the conventional method for concrete. The results obtained for the nanostructure of cement pastes presented mean elastic modulus values of 17.9 GPa and 0.90 GPa for hardness. Determination of the elastic modulus calculated by NBR 6118 [1] was 9.6 GPa. Nanoindentation proved to be a valid method for evaluating nanostructure modifications in cement pastes.
Nanoscale Research Letters, 2016
In the last decade, nanotechnology has been gathering a spectacular amount of attention in the field of building materials. The incorporation of nanosized particles in a small amount to the building materials can influence their properties significantly. And it can contribute to the creation of novel and sustainable structures. In this work, the effect of nano-Fe 3 O 4 as an admixture (from 1 to 5 wt.% in mass of the cement) on the mechanical and microstructural properties of cementitious composites has been characterised. The study showed that Fe 3 O 4 nanoparticles acted as a filler which improved the microstructure of a cementitious composite and reduced its total porosity, thus increasing the density of the composite. The presence of nanomagnetite did not affect the main hydration products and the rate of cement hydration. In addition, the samples containing nanomagnetite exhibited compressive strength improvement (up to 20 %). The study showed that 3 wt.% of nano-Fe 3 O 4 in the cementitious composite was the optimal amount to improve both its mechanical and microstructural properties.
Characterization of Portland cement paste using MIP, nanoindentation and esem techniques
The performance of concrete is increasingly designed through durability. Durable concrete is a driving force for a sustainable production and use of cement. One way to achieve durability of concrete is to fathom the mechanical properties of the cement matrix and the main associated features of its microstructure. Non-destructive experimental methods such as nanoindentation and ESEM were used to characterize the hardened Portland cement paste with w/c=0.40 hydrated at 7, 14 and 28 days. Grid indentation analysis was employed between approximately two equal sized hydrated cement particles. Additionally, MIP was used as a generally accepted technique for deriving porosity and pore size distribution and results correlated to those received from ESEM image analysis.
Current Applied Physics, 2016
We carry out molecular dynamics simulations of nanoindentation to investigate the effect of cementite size and temperature on the deformation behavior of nanocomposite pearlite composed of alternating ferrite and cementite layers. We find that, instead of the coherent transmission, dislocation propagates by forming a widespread plastic deformation in cementite layer. We also show that increasing temperature enhances the distribution of plastic strain in the ferrite layer, which reduces the stress acting on the cementite layer. Hence, thickening cementite layer or increasing temperature reduces the likelihood of dislocation propagation through the cementite layer. Our finding sheds a light on the mechanism of dislocation blocking by cementite layer in the pearlite. Introduction-Pearlitic phase, a lamellar structure composed of alternating layers of ferrite and cementite, plays an important role in determining the mechanical properties of steels, such as toughness, strength and formability [1]. Compared to ferrite, pearlitic structure is known as a harder phase with higher strength due to the presence of cementite lamellae, and its mechanical properties are significantly affected by the cementite microstructure [2-3]. It has been found that the fine pearlite with small interlamellar spacing (~100 nm) and narrow cementite lamellae (~10 nm) shows higher ductility than coarse pearlite during plastic deformation [4-8]. Cementite layer act as a hard obstacle in front of ferrite dislocations and causes to dislocation pile up at the ferrite/cementite interface [9]. However, to the best of our knowledge, there has been no direct experimental or simulation study on the mechanism of the dislocation blockage by the cementite layer. Nanoindentation is a mechanical test which uses an indenter with a known geometry to plunge into a specific site of the specimen by applying an increasing load [10]. It is widely used to determine the mechanical properties of thin films to clarify the effect of geometric confinement on mechanical
Nanomechanical study of cement pastes by statistical nanoindentation and peakforce QNM
The study is related to the EU 7th Framework Programme CODICE (COmputationally Driven design of Innovative CEment-based materials) project. The main aim of the project is the development of a multi-scale model for the computer based simulation of mechanical and durability performance of cementitious materials. As part of the task to study the micromechanical properties of computationally driven designs and validate the model predictions, extensive work on micro/nano-mechanical characterisation of cement-based materials has been conducted, which cover synthetic C 3 S, C 2 S pastes, cement pastes hydrated at different ages and pastes subjected to accelerated calcium leaching, etc. Statistical nanoindentation and micro-mechanical property mapping technique was used to study intrinsic properties of different hydrate phases and microstructures down to approximately 1 μm. A new experimental technique-Peakforce QNM was also used to examine mechanical properties of cement paste micro/nano-structures down to approximately 10 nm. The importance of proper specimen preparation is highlighted, particularly for the early-aged and leached samples due to their weak and fragile microstructure. The results obtained from the two experimental techniques are presented and advantages/limitations for each technique discussed.
Scientific Reports, 2020
In this study, fabrication of a composite containing the ordinary Portland cement (OPC) and magnetite (Fe3O4) micro/nanoparticles is reported. In the first stage, the cement paste samples with a fixed 0.2 wt.% Fe3O4 additive in four different particle sizes (20–40 nm, 80–100 nm, 250–300 nm, and 1–2 µm) were prepared to check the effect of magnetite size. Magnetite was found to play an effective role in reinforcing cement matrix. The results showed that the cement paste reinforced by magnetite nanoparticles of 20–40 nm size range had the highest compressive, flexural, and tensile strengths compared to those of the other samples reinforced by larger particles. In the second stage, various amounts of the Fe3O4 nanoparticles of 20–40 nm size range were added to the cement to evaluate the influence of magnetite amount and find the optimized reinforcement amount. It was revealed that adding 0.25 wt.% Fe3O4 nanoparticles of 20–40 nm size range, as the optimal specimen, increased the compre...
2020
The durability of cementitious composites continues to be an issue that receives the attention of practitioners and researchers around the world, which has led to the design of high-performance cementitious composites such as engineered cementitious composites (ECC). ECCs have high ductility capacity that makes them more durable, however, further, improvement isdesirable.This paper, therefore,sought to evaluate the mechanical properties and sorptivity capabilities of ECCs produced with dosages of nano-silica.The 28 th -day test results showed improvements in the compressive strength of the specimens with increasing dosage of nanosilica. Nonetheless, the 28 th -day flexural strength of the specimens slightly reduced with an increasing amount of nano-silica dosage. Concerning the 28 th -day sorptivity measurements,it was observed that the sorptivity coefficients reducedwith increased dosages of nano-silica. There were significant reductions in the sorptivity values of the various spec...