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The present paper serves the purpose of presenting an extinct type of 18th–19th century masonry building, that of an ox-stable, situated in one of Europe’s most secluded areas: The Holy Monastery of Pantokrator in Mount Athos Peninsula. Architectural drawings and surveying plots of its current state can serve as a record and reference of this UNESCO site for scholars. Adding to that, an elaborated proposal for the reuse of the building is presented together with technical drawings, which were approved by Greece’s Central Archeological Council. The masonry rectangular building is founded on natural rock with masonry pillar footings of different heights. Hence, the elevation irregularity and the different elevations of the footings of the structure present an additional challenge for the structural analysis. Structural analysis with a finite element (FE) model of the restored structure was executed with SAP2000 software. Performing lateral force and response spectrum analyses, stresses and deformations at critical points of the structure were calculated. Comparing a set of simplifying structural checks with the elastic FE analysis performed, it was concluded that the proposed design is effective in improving the earthquake performance of the structure.
Styliani Papatzani; Nikolaos Pnevmatikos; Konstantinos Dimitroulias; Georgios Michail; Georgios Sapiridis; Vasilakis Flentzouris. Mount Athos: Restoration of an Almost Extinct Type of 18th–19th C. UNESCO Masonry OX Stable. Heritage 2021, 4, 1284 -1303.
AMA StyleStyliani Papatzani, Nikolaos Pnevmatikos, Konstantinos Dimitroulias, Georgios Michail, Georgios Sapiridis, Vasilakis Flentzouris. Mount Athos: Restoration of an Almost Extinct Type of 18th–19th C. UNESCO Masonry OX Stable. Heritage. 2021; 4 (3):1284-1303.
Chicago/Turabian StyleStyliani Papatzani; Nikolaos Pnevmatikos; Konstantinos Dimitroulias; Georgios Michail; Georgios Sapiridis; Vasilakis Flentzouris. 2021. "Mount Athos: Restoration of an Almost Extinct Type of 18th–19th C. UNESCO Masonry OX Stable." Heritage 4, no. 3: 1284-1303.
This paper presents the effects of the addition of (i) the organomodified nanomontmorillonite (nMt) dispersion, nC2, produced for the scope of the FP7 project name FIBCEM and of (ii) the powder, undispersed organomodified industrially produced nMt, nC4 on quaternary nMt-fibre reinforced binders. The reference binder consisted of 60% Portland cement (PC), 20% limestone (LS) and 20% fly ash (FA). Superplasticizer was added at 2%, polyvinyl alcohol fibres at 3% and nMt was added at 1%. Flexural strength test were carried out at day 7, 28, 56 and 90 showed marginal enhancement offered by the nMt dispersion, which was attributed to limited, but existing additional pozzolanic reactivity of the particles of nMt. If fact, following methodology presented in published papers on other formulations, thermal gravimetric and X-ray diffraction analysis showed limited consumption of Ca(OH)2 towards production of additional C–S–H, which is in line with the marginal increase of flexural strength for the same age of testing.
Styliani Papatzani; Sotirios Grammatikos; Kevin Paine. Interesting Remarks on the Comparison of Organomodified Nanomontmorillonites in Fibre-Cement Nanohybrids. IOP Conference Series: Materials Science and Engineering 2020, 842, 012008 .
AMA StyleStyliani Papatzani, Sotirios Grammatikos, Kevin Paine. Interesting Remarks on the Comparison of Organomodified Nanomontmorillonites in Fibre-Cement Nanohybrids. IOP Conference Series: Materials Science and Engineering. 2020; 842 (1):012008.
Chicago/Turabian StyleStyliani Papatzani; Sotirios Grammatikos; Kevin Paine. 2020. "Interesting Remarks on the Comparison of Organomodified Nanomontmorillonites in Fibre-Cement Nanohybrids." IOP Conference Series: Materials Science and Engineering 842, no. 1: 012008.
In an effort to produce cost-effective and environmentally friendly cementitious binders. mainly ternary (Portland cement + limestone + pozzolanas) formulations have been investigated so far. Various proportions of constituents have been suggested, all, however, employing typical Portland cement (PC) substitution rates, as prescribed by the current codes. With the current paper a step by step methodology on developing low carbon footprint binary, ternary and quaternary cementitious binders is presented (PC replacement up to 57%). Best performing binary (60% PC and 40% LS (limestone)) and ternary formulations (60% PC, 20% LS, 20% FA (fly ash) or 43% PC, 20% LS 37% FA) were selected on the grounds of sustainability and strength development and were further optimized with the addition of silica fume. For the first time a protocol for successfully selecting and testing binders was discussed and the combined effect of highly pozzolanic constituents in low PC content formulations was assessed and a number of successful matrices were recommended. The present paper enriched the current state of the art in composite low carbon footprint cementitious binders and can serve as a basis for further enhancements by other researchers in the field.
Styliani Papatzani; Kevin Paine. A Step by Step Methodology for Building Sustainable Cementitious Matrices. Applied Sciences 2020, 10, 2955 .
AMA StyleStyliani Papatzani, Kevin Paine. A Step by Step Methodology for Building Sustainable Cementitious Matrices. Applied Sciences. 2020; 10 (8):2955.
Chicago/Turabian StyleStyliani Papatzani; Kevin Paine. 2020. "A Step by Step Methodology for Building Sustainable Cementitious Matrices." Applied Sciences 10, no. 8: 2955.
In the present review paper, the term “effectiveness” of nanolime consolidants was redefined by presenting a suite of efficiency parameters/material properties that must be assessed in order to compare available treatments for weathered calcareous stones for historic buildings. Assessment tools in the form of characterization methods for synthetized nanolime dispersions, artificial weathering techniques, and treated calcareous stones were correlated and discussed, giving rise to non-destructive testing methods. The effect of the application method and dispersion medium was also presented. It was concluded that the presented suite of efficiency parameters and characterization techniques can be applied to further studies for the development of mass consolidation procedures in order to reach penetration depths well beyond the 5.5 cm threshold achieved up to date.
Styliani Papatzani; Emmanouil Dimitrakakis. A Review of the Assessment Tools for the Efficiency of Nanolime Calcareous Stone Consolidant Products for Historic Structures. Buildings 2019, 9, 235 .
AMA StyleStyliani Papatzani, Emmanouil Dimitrakakis. A Review of the Assessment Tools for the Efficiency of Nanolime Calcareous Stone Consolidant Products for Historic Structures. Buildings. 2019; 9 (11):235.
Chicago/Turabian StyleStyliani Papatzani; Emmanouil Dimitrakakis. 2019. "A Review of the Assessment Tools for the Efficiency of Nanolime Calcareous Stone Consolidant Products for Historic Structures." Buildings 9, no. 11: 235.
Clinker reduction in cementitious binders is of paramount importance today, and nanotechnology has extended permissible limits. In the present study, a reference binder consisting of 60% Portland cement, 20% limestone, 20% fly ash, 3% polyvinyl alcohol (PVA) fibres and 2% superplasticizer is optimized with three different types of nano-montmorillonite (nMt) dispersions; two organomodified ones and an inorganic one at different proportions (0.5% to 4%). Flexural strength, measured on day 7, 28, 56 and 90, was improved after day 28 with the addition of inorganic nMt. Thermal gravimetric analyses carried out on day 7, 28, 56 and 90 coupled with x-ray diffraction (at day 28) showed a distinctively enhanced pozzolanic reaction. Backscattered electron imaging confirmed changes in the microstructure. Late age relative density measurements of the nMt cementitious nanocomposites showed higher values than these of the reference paste, which can be attributed to better particle packing. Mercury intrusion porosimetry measurements give support to the optimal nMt dosage, being 1% by total mass of binder and water impermeability tests (modified with BS EN 492:2012) suggest that inorganic nMt can be a viable option material where permeability constitutes a prerequisite. Suggestions for further activation of the nMt-fibre reinforced cementitious nanocomposites were also made.
Styliani Papatzani; Sotirios Grammatikos; Kevin Paine. Permeable Nanomontmorillonite and Fibre Reinforced Cementitious Binders. Materials 2019, 12, 3245 .
AMA StyleStyliani Papatzani, Sotirios Grammatikos, Kevin Paine. Permeable Nanomontmorillonite and Fibre Reinforced Cementitious Binders. Materials. 2019; 12 (19):3245.
Chicago/Turabian StyleStyliani Papatzani; Sotirios Grammatikos; Kevin Paine. 2019. "Permeable Nanomontmorillonite and Fibre Reinforced Cementitious Binders." Materials 12, no. 19: 3245.
With the current paper three nano-Montmorillonites (nMt) are applied in cement nanohybrids: an organomodified nMt dispersion, nC2; an inorganic nMt dispersion, nC3; and an organomodified powder, nC4. nC4 is fully characterized in this paper (X-ray diffraction, scanning electron microscopy/X-ray energy dispersive spectroscopy and thermal gravimetric analysis/differential thermogravimetry. Consecutively a ternary non pozzolanic combination of fiber–cement nanohybrids (60% Portland cement (PC) and 40% limestone (LS)) was investigated in terms of flexural strength, thermal properties, density, porosity, and water impermeability. Flexural strength was improved after day 28, particularly with the addition of the inorganic nMt dispersion. There was no change in density or enhancement in pozzolanic reactions for the powder nMt. Mercury intrusion porosimetry showed that the pore related parameters were increased. This can be attributed to mixing effects and the presence of fibers. Water impermeability tests yielded ambiguous results. Clearly, novel manufacturing processes of cement nanohybrids must be developed to eliminate mixing issues recorded in this research.
Styliani Papatzani; Kevin Paine. From Nanostructural Characterization of Nanoparticles to Performance Assessment of Low Clinker Fiber–Cement Nanohybrids. Applied Sciences 2019, 9, 1938 .
AMA StyleStyliani Papatzani, Kevin Paine. From Nanostructural Characterization of Nanoparticles to Performance Assessment of Low Clinker Fiber–Cement Nanohybrids. Applied Sciences. 2019; 9 (9):1938.
Chicago/Turabian StyleStyliani Papatzani; Kevin Paine. 2019. "From Nanostructural Characterization of Nanoparticles to Performance Assessment of Low Clinker Fiber–Cement Nanohybrids." Applied Sciences 9, no. 9: 1938.
The dispersion medium of nano-SiO2 (nS) particles can have a significant effect on the properties of nanoparticles themselves and consequently on the cement binders it will be added to. In this paper, nS particles dispersed in (a) polycarboxylate or (b) water were added to a low-carbon footprint reference binder containing 43% Portland cement (PC), 20% limestone powder (LS), and 37% fly ash (FA) by mass of binder. Eight quaternary binders containing nS, PC, LS, and FA and eight quinary binders comprising nS, PC, LS, FA, and silica fume (μS) were investigated. nS was added at 0.1%, 0.2%, 0.5%, or 1.0% by mass of binder as a replacement of LS for the quaternary binders and at 0.5% or 1.0% for the quinary binders. The nanoparticles were examined via transmission and X-ray scanning electron microscopy (TEM/SEM/EDX). For the pastes, compressive strength tests and thermal gravimetric analyses (TGAs) were performed at days 1, 7, 28, and 56, all testified to additional pozzolanic activity and additional C–S–H production. X-ray diffraction analyses and backscattered scanning electron imaging carried out on specific formulations also confirmed this finding at days 1, 28, and 56. Notwithstanding the additional pozzolanic reactivity, nS particles could not mitigate the delayed hydration of the reference paste in the early ages. In such complex formulations, the hydration products seem to create a wrapping around the FA particles delaying their activation at early ages. At later ages, the 0.5% nS addition provided strength, microstructural, and hydration improvements. The polycarboxylate/nS particles provided more pronounced strength improvements at 0.5% addition, possibly due to their superplasticizing effect. Lastly, a tabulated literature review on the thermal decomposition ranges of the hydration products of cementitious nanocomposites is also presented.
Styliani Papatzani; Kevin Paine. Optimization of Low-Carbon Footprint Quaternary and Quinary (37% Fly Ash) Cementitious Nanocomposites with Polycarboxylate or Aqueous Nanosilica Particles. Advances in Materials Science and Engineering 2019, 2019, 1 -26.
AMA StyleStyliani Papatzani, Kevin Paine. Optimization of Low-Carbon Footprint Quaternary and Quinary (37% Fly Ash) Cementitious Nanocomposites with Polycarboxylate or Aqueous Nanosilica Particles. Advances in Materials Science and Engineering. 2019; 2019 ():1-26.
Chicago/Turabian StyleStyliani Papatzani; Kevin Paine. 2019. "Optimization of Low-Carbon Footprint Quaternary and Quinary (37% Fly Ash) Cementitious Nanocomposites with Polycarboxylate or Aqueous Nanosilica Particles." Advances in Materials Science and Engineering 2019, no. : 1-26.
Nanotechnology has changed the way we perceive science, our world and consequently the built environment. Cement sustainability is of primary importance and nanotechnology can offer new alternatives towards lowering the CO2 footprint by reducing clinker, by increasing the by-products content and by creating more durable formulations. This paper presents an optimization protocol of ternary Portland limestone nanocomposites through the addition of nanosilica or nanomontmorillonite (nMt) particles. Thermal gravimetric and X-ray diffraction analyses, confirmed the Ca(OH)2 consumption towards the production of C-S-H. Mercury intrusion porosimetry (MIP) and long-term relative density measurements coupled with field emission scanning electron imaging (FESEM) confirmed the microstructural changes leading to strength enhancement. Lastly, limitations were determined through the extensive study of the addition of nanosilica particles at four different dosages (0.1, 0.5, 1.0, 1.5% addition by total mass of solids) or three different nMt dispersions at five different dosages (0.5, 1.0, 2.0, 4.0 and 5.5%). Strength tests and characterization were carried out at day 1, 7, 28, 56, 90 and 170 to assess both the short- and long-term effects. Nanosilica and inorganic nMt particles were found to be the most effective at lower dosages for strength, hydration and microstructural improvements.
Styliani Papatzani; Kevin Paine. Lowering cement clinker: A thorough, performance based study on the use of nanoparticles of SiO2 or montmorillonite in Portland limestone nanocomposites. The European Physical Journal Plus 2018, 133, 430 .
AMA StyleStyliani Papatzani, Kevin Paine. Lowering cement clinker: A thorough, performance based study on the use of nanoparticles of SiO2 or montmorillonite in Portland limestone nanocomposites. The European Physical Journal Plus. 2018; 133 (10):430.
Chicago/Turabian StyleStyliani Papatzani; Kevin Paine. 2018. "Lowering cement clinker: A thorough, performance based study on the use of nanoparticles of SiO2 or montmorillonite in Portland limestone nanocomposites." The European Physical Journal Plus 133, no. 10: 430.
The effect of polycarboxylate/nanosilica (nS) particles in quaternary cement formulations comprising Portland cement (PC), limestone powder (LS) and fly ash (FA) was investigated for the first time. The reference formulation contained 60% PC, 20% LS and 20% FA by mass of binder in an effort to minimise clinker and maximise the other constituents. nS particles were characterised by way of transmission and X-ray scanning electron microscopy (SEM). The nS was added at 0·3 or 0·6% by mass as a partial replacement for PC and different water-to-binder (w/b) ratios were explored. Compressive strength tests and thermal gravimetric analyses (TGA) performed at day 7, 28 and 56 testified to pozzolanic behaviour. Results suggest a mechanism of ‘de-activation’ of some FA particles with age. A new ratio: (compressive strength in MPa)/(calcium hydroxide content detected by TGA) was introduced, correlating microscale characteristics (hydration products) and macroscale performance (delivered compressive strengths). Back-scattered SEM images confirmed the calcium–silicate–hydrate (C–S–H) network formation, the presence of reacted/unreacted FA particles and the availability of calcium hydroxide for delayed hydration reactions. Tests on mortars also confirmed the enhancement offered by nS addition. The lower bound nS addition was determined to be 0·6% by mass of binder for pastes and 0·5% for mortars.
Styliani Papatzani; Kevin Paine. Polycarboxylate/nanosilica-modified quaternary cement formulations – enhancements and limitations. Advances in Cement Research 2018, 30, 256 -269.
AMA StyleStyliani Papatzani, Kevin Paine. Polycarboxylate/nanosilica-modified quaternary cement formulations – enhancements and limitations. Advances in Cement Research. 2018; 30 (6):256-269.
Chicago/Turabian StyleStyliani Papatzani; Kevin Paine. 2018. "Polycarboxylate/nanosilica-modified quaternary cement formulations – enhancements and limitations." Advances in Cement Research 30, no. 6: 256-269.
The pozzolanic potentials of three non-thermally treated, nano-montmorillonite (NMt) dispersions were investigated by a new method involving the analysis of NMt/lime putty pastes via TGA/dTG and XRD crystallographic and semi-quantitative analysis. The criterion conceived was validated at eight days and eight months and was additionally verified via the Chapelle method. The inorganic NMt dispersion showed the most pronounced pozzolanic behaviour promoting Ca(OH)2 consumption towards calcium silicate/aluminate hydrates formation and binding behaviour. The two organomodified NMt dispersions exhibited pozzolanicity increasing with time. The results can pave the way for advances in cement science and restoration mortars development for historical structures rehabilitation, where low CO2-footprint, natural inorganic materials are a prerequisite.
Styliani Papatzani; Efstratios G. Badogiannis; Kevin Paine. The pozzolanic properties of inorganic and organomodified nano-montmorillonite dispersions. Construction and Building Materials 2018, 167, 299 -316.
AMA StyleStyliani Papatzani, Efstratios G. Badogiannis, Kevin Paine. The pozzolanic properties of inorganic and organomodified nano-montmorillonite dispersions. Construction and Building Materials. 2018; 167 ():299-316.
Chicago/Turabian StyleStyliani Papatzani; Efstratios G. Badogiannis; Kevin Paine. 2018. "The pozzolanic properties of inorganic and organomodified nano-montmorillonite dispersions." Construction and Building Materials 167, no. : 299-316.
In the present paper, the effect of three different types of nano-montmorillonite dispersions (nMt) on the (i) microstructure as witnessed by Scanning Electron Microscopy, (ii) long term density measurements and (iii) pore structure as determined via Mercury Intrusion Porosimetry of Portland – limestone cement formulations have been compared, in an effort to determine the upper and lower bound of nMt addition in cementitious nanocomposites. The reference formulation, contained 60% PC and 40% LS by mass of binder aiming at the minimization of clinker and maximization of other constituents. Two aqueous organomodified NMt dispersions (one dispersed with non-ionic fatty alcohol and the other with anionic alkyl aryl sulphonate) and one aqueous inorganic NMt dispersion (dispersed with sodium tripolyphosphate) were added at 0.5, 1, 2, 4 and 5.5% by mass of solids as replacement of Portland cement. The water to solids ratio was kept constant at 0.3. The inorganic nMt showed the greatest potentials for microstructural enhancement. The way in which the level of the nMt platelet separation affected the pastes was discussed. The research reported was part of a much broader project supported by the EU.
Styliani Papatzani; Sotirios Grammatikos; Bijan Adl-Zarrabi; Kevin Paine. Pore-structure and microstructural investigation of organomodified/Inorganic nano-montmorillonite cementitious nanocomposites. 2018 6TH INTERNATIONAL CONFERENCE ON NANO AND MATERIALS SCIENCE: ICNMS 2018 2018, 1957, 030004 .
AMA StyleStyliani Papatzani, Sotirios Grammatikos, Bijan Adl-Zarrabi, Kevin Paine. Pore-structure and microstructural investigation of organomodified/Inorganic nano-montmorillonite cementitious nanocomposites. 2018 6TH INTERNATIONAL CONFERENCE ON NANO AND MATERIALS SCIENCE: ICNMS 2018. 2018; 1957 (1):030004.
Chicago/Turabian StyleStyliani Papatzani; Sotirios Grammatikos; Bijan Adl-Zarrabi; Kevin Paine. 2018. "Pore-structure and microstructural investigation of organomodified/Inorganic nano-montmorillonite cementitious nanocomposites." 2018 6TH INTERNATIONAL CONFERENCE ON NANO AND MATERIALS SCIENCE: ICNMS 2018 1957, no. 1: 030004.
This is the first time an analytical protocol is proposed to investigate and live-monitor the behaviour of montmorillonite nanoparticles, of different natures, in alkaline cement environment (pH of 12-13). In this study inorganic and organomodified montmorillonite nanoparticles were characterised via TEM, XRD, SEM-EDX and TGA. The inorganic montmorillonite used consisted of a purified montmorillonite commercially available as HPS-clay, and an organomodified montmorillonite, namely XDB-organoclay, consisted of purified montmorillonite modified with Noramonium MB2HT salt. Both montmorillonite nanoparticles were tailored to increase their compatibility with the hydrating cement environment. This gave rise to three different slurries: (i) reference-slurry, (ii) inorganic-slurry, and (iii) organic-slurry. The slurries were characterised and investigated through UV/vis, to measure suspension quality in terms of physical stability and rheological properties, and by AFM and FTIR to determine the chemical stability. The results indicated that the organic-slurry can offer a good stability, preventing aggregation of the clay particles at the targeted pH (13). The inorganic-slurry showed a reduction in surface charge and increased double layer repulsion. At pH 13 it was possible to obtain dispersion of the reference slurry although it underwent gelation and became viscous. The research findings informed that the inorganic slurry favours miscibility of the montmorillonite nanoparticles with cement particles and offers additional nucleation sites for CSH. Therefore it can be considered an alternative to organomodified montmorillonite as an addition in cement based materials
Juliana Calabria-Holley; Styliani Papatzani; Benjamin Naden; John Mitchels; Kevin Paine. Tailored montmorillonite nanoparticles and their behaviour in the alkaline cement environment. Applied Clay Science 2017, 143, 67 -75.
AMA StyleJuliana Calabria-Holley, Styliani Papatzani, Benjamin Naden, John Mitchels, Kevin Paine. Tailored montmorillonite nanoparticles and their behaviour in the alkaline cement environment. Applied Clay Science. 2017; 143 ():67-75.
Chicago/Turabian StyleJuliana Calabria-Holley; Styliani Papatzani; Benjamin Naden; John Mitchels; Kevin Paine. 2017. "Tailored montmorillonite nanoparticles and their behaviour in the alkaline cement environment." Applied Clay Science 143, no. : 67-75.
The compatibility of three nano-montmorillonite (NMt) dispersions in hydrating cement binders was investigated and a new theory linking the nanostructure of nanoclay dispersions to their effect on the macroscale performance of cement pastes is presented. Two aqueous organomodified NMt dispersions (one dispersed with non-ionic fatty alcohol and the other with anionic alkyl aryl sulfonate) and one aqueous inorganic NMt dispersion (dispersed with sodium tripolyphosphate) were characterized via transmission electron microscopy imaging and crystallography, X-ray diffraction, Scanning electron microscopy/X-ray energy dispersive spectroscopy, and thermogravimetric analysis/differential thermogravimetry. With this characterization protocol, the way carbon loading and surfactants interact with the nanostructure of the nanoclay dispersions in light of their addition in composite cements was clarified. The suggested methodology is suited for the characterization of nanoclay dispersions and the new theory developed will open up a new horizon for the understanding and exploitation of nano-montmorillonite as a supplementary cementitious material.
Styliani Papatzani; Kevin Paine. Inorganic and organomodified nano-montmorillonite dispersions for use as supplementary cementitious materials – a novel theory based on nanostructural studies. Nanocomposites 2017, 3, 2 -19.
AMA StyleStyliani Papatzani, Kevin Paine. Inorganic and organomodified nano-montmorillonite dispersions for use as supplementary cementitious materials – a novel theory based on nanostructural studies. Nanocomposites. 2017; 3 (1):2-19.
Chicago/Turabian StyleStyliani Papatzani; Kevin Paine. 2017. "Inorganic and organomodified nano-montmorillonite dispersions for use as supplementary cementitious materials – a novel theory based on nanostructural studies." Nanocomposites 3, no. 1: 2-19.
Styliani Papatzani. Effect of nanosilica and montmorillonite nanoclay particles on cement hydration and microstructure. Materials Science and Technology 2016, 32, 138 -153.
AMA StyleStyliani Papatzani. Effect of nanosilica and montmorillonite nanoclay particles on cement hydration and microstructure. Materials Science and Technology. 2016; 32 (2):138-153.
Chicago/Turabian StyleStyliani Papatzani. 2016. "Effect of nanosilica and montmorillonite nanoclay particles on cement hydration and microstructure." Materials Science and Technology 32, no. 2: 138-153.
Cementitious materials have a complex chemistry and naturally form nanostructures in the hydration process, a network of calcium silicate hydrates. It is considered that nanoparticles such as nanosilica could act as a pozzolanic material as well as a seeding agent for nucleation and acceleration of the formation of the calcium silicate hydrate network. This work evaluates the effect of nanosilica on the calcium silicate hydrate network and microstructure of hardened ternary, quaternary and quinary system Portland cement based pastes. The quinary system, containing Portland cement, limestone, fly ash, microsilica and nanosilica, and ternary combinations (Portland cement, limestone and fly ash) showed mean calcium/silicon atomic ratios of the calcium silicate hydrate gel in the 28 d old hardened paste of 1·2 and 2·3 respectively. Fourier transform infrared spectroscopy results show the presence of the bridging silicate tetrahedra (Q2) characteristic of a peak at around 980 cm−1 and a shoulder at around 1060 cm−1 in the calcium silicate hydrate gel network of the ternary, quaternary and quinary combinations; these bands are thus more pronounced for the nanosilica-enhanced formulations. The sample obtained in the presence of microsilica and nanosilica (quinary combination) showed evidence of a more intricate calcium silicate hydrate gel network (bridging tetrahedra) characteristic of a honeycomb-like structure opposed to the ternary combination (control sample). Cementitious materials have a complex chemistry and naturally form nanostructures in the hydration process, a network of calcium silicate hydrates. It is considered that nanoparticles such as nanosilica could act as a pozzolanic material as well as a seeding agent for nucleation and acceleration of the formation of the calcium silicate hydrate network. This work evaluates the effect of nanosilica on the calcium silicate hydrate network and microstructure of hardened ternary, quaternary and quinary system Portland cement based pastes. The quinary system, containing Portland cement, limestone, fly ash, microsilica and nanosilica, and ternary combinations (Portland cement, limestone and fly ash) showed mean calcium/silicon atomic ratios of the calcium silicate hydrate gel in the 28 d old hardened paste of 1·2 and 2·3 respectively. Fourier transform infrared spectroscopy results show the presence of the bridging silicate tetrahedra (Q2) characteristic of a peak at around 980 cm−1 and a shoulder at around 1060 cm−1 in the calcium silicate hydrate gel network of the ternary, quaternary and quinary combinations; these bands are thus more pronounced for the nanosilica-enhanced formulations. The sample obtained in the presence of microsilica and nanosilica (quinary combination) showed evidence of a more intricate calcium silicate hydrate gel network (bridging tetrahedra) characteristic of a honeycomb-like structure opposed to the ternary combination (control sample).
Juliana Calabria-Holley; Kevin Paine; Styliani Papatzani. Effects of nanosilica on the calcium silicate hydrates in Portland cement–fly ash systems. Advances in Cement Research 2015, 27, 187 -200.
AMA StyleJuliana Calabria-Holley, Kevin Paine, Styliani Papatzani. Effects of nanosilica on the calcium silicate hydrates in Portland cement–fly ash systems. Advances in Cement Research. 2015; 27 (4):187-200.
Chicago/Turabian StyleJuliana Calabria-Holley; Kevin Paine; Styliani Papatzani. 2015. "Effects of nanosilica on the calcium silicate hydrates in Portland cement–fly ash systems." Advances in Cement Research 27, no. 4: 187-200.
The need to master factors affecting the performance of concrete has sparked research on its basic constituent, cement, whose properties are determined by one of the most critical cement hydration products, the calcium silicate hydrate. The present paper discusses the evolution of models describing the nanostructure of the calcium silicate hydrate (C–S–H) over the past century (descriptive models), with a focus on the models presented in the last fifteen years, 2000–2014 (descriptive and predictive models), marked with the breakthrough of nanotechnology. The purposes and outcomes of the suggested models are discussed, along with their limitations. The article concludes that notwithstanding the enormous potentials nanotechnology and advanced molecular modelling have offered in the field, modern models are, in essence, still expanding on the colloidal or layered models suggested in the 60s, rather than providing a ground breaking new approach. However, it is generally recognised that nanotechnology and molecular modelling have, facilitated the shift from descriptive to predictive models, saving time and resources by extrapolating results of very lengthy experiments, e.g. sorption isotherms, or by mathematically manipulating the C–S–H components to derive different structures and assemblages, that would have been difficult or impossible in practice. In that sense, the new experimental methods available, paired with analytical models are able to provide further justification of the pioneering studies and advance cement nanoscience, paving the way to the production of innovative, nanomodified cements, with minimum Portland cement content
Styliani Papatzani; Kevin Paine; Juliana Calabria-Holley. A comprehensive review of the models on the nanostructure of calcium silicate hydrates. Construction and Building Materials 2015, 74, 219 -234.
AMA StyleStyliani Papatzani, Kevin Paine, Juliana Calabria-Holley. A comprehensive review of the models on the nanostructure of calcium silicate hydrates. Construction and Building Materials. 2015; 74 ():219-234.
Chicago/Turabian StyleStyliani Papatzani; Kevin Paine; Juliana Calabria-Holley. 2015. "A comprehensive review of the models on the nanostructure of calcium silicate hydrates." Construction and Building Materials 74, no. : 219-234.
Nanotechnology offers an opportunity to modify and observe cement at the nanolevel. In this research, the degree of dispersion of two aqueous suspensions of organomodified montmorillonite (OMMT) clay nanoparticles and one inorganic nanoclay (nC) dispersion was verified by TEM. The effect of the addition of each one of the three dispersions to a high limestone content (40 % by mass of binder) Portland limestone cement was investigated in terms of compressive strength, thermogravimetric (TG) analyses and morphological characteristics of the pastes. It was found that the upper limit of nC addition, in such pastes is 1 % nC solids by mass of binder and that intercalated OMMT cannot offer significant compressive strength improvement. However, there were strong indications that the pozzolanic reactions were promoted by the better dispersed OMMT and by the inorganic nC dispersion. The FESEM images captured, depicted the morphological characteristics of the nanomodified cement formulations. Furthermore, evidences suggest that the specific nanoclays can offer enhancement for flexural performance of blended cements with no degradation over time. Overall, the inorganic nC dispersion exhibited the highest pozzolanic activity, the highest flexural strength improvement and the most dense microstructure. The research reported was part of a much broader research project (FIBCEM) supported by the EU
Styliani Papatzani; Kevin Paine. Dispersed Inorganic or Organomodified Montmorillonite Clay Nanoparticles for Blended Portland Cement Pastes: Effects on Microstructure and Strength. Nanotechnology in Construction 2015, 131 -139.
AMA StyleStyliani Papatzani, Kevin Paine. Dispersed Inorganic or Organomodified Montmorillonite Clay Nanoparticles for Blended Portland Cement Pastes: Effects on Microstructure and Strength. Nanotechnology in Construction. 2015; ():131-139.
Chicago/Turabian StyleStyliani Papatzani; Kevin Paine. 2015. "Dispersed Inorganic or Organomodified Montmorillonite Clay Nanoparticles for Blended Portland Cement Pastes: Effects on Microstructure and Strength." Nanotechnology in Construction , no. : 131-139.