Nano Metakaolin Research Articles

The compressive behavior of cement mortar with the addition of nano metakaolin

Elastic modulus is an important mechanical index for the cement-based materials, which has a significant effect on the static and dynamic response of the concrete structure. To investigate the compressive behavior of nano metakaolin cement mortar, the effects of dispersion conditions, water to binder ratios, and mineral admixtures on the compressive strength of nano metakaolin cement mortar were examined. The elastic modulus of nano metakaolin cement mortar under different water to binder ratios and mineral admixtures was obtained. Based on the theory of micromechanics of composite materials, a theoretical model was deduced to calculate elastic modulus of nano metakaolin cement mortar. Based on the experimental results, an influence coefficient was introduced into simplified model to estimate the elastic modulus of nano metakaolin cement mortar. The results demonstrate that the application of ultrasonic dispersion and long-duration dispersion time (no more than 15 min) can effectively improve the compressive strength of nano metakaolin cement mortar. Compressive strength of nano metakaolin cement mortar mixed with ground granulated blast furnace slag, fly ash, and attapulgite clay is 33.38%, 17.65%, and 6.45% higher than that of the ordinary mortar, respectively. Compared with the experimental results, the calculated error of theoretical model is no more than 5%, while the calculated error of the simplified model is no more than 10%.

TOWARDS THE PRODUCTION OF HIGH PERFORMANCE AUTOCLAVED BINDING PRODCTS FROM INDUSTRIAL SOLID WASTES

The object of this investigation is to study the possible production of autoclaved building products using several industrial solid wastes, produced as by-products from certain industries, as pozzolanic materials activated using alkaline activators namely, cement kiln dust (CKD) and hydrated lime [Ca(OH)2]. The ground granulated blast-furnace slag (GGBFS)-cement kiln dust (CKD) mixes were made with and without nano-metakaolin (NMK) and silica fume (SF) as additives. The four dry mixtures were prepared and subjected to hydrothermal conditions in the autoclave at a pressure of 8 atmospheres of saturated steam for different curing ages of 0.5, 2, 6, 12 and 24 hours. The autoclaved specimens, thus produced were examined for their chemical and mechanical properties. These specimens are characterized using thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) as well as compressive strength and kinetics of hydration via the determination of chemically combined water (Wn, %) and free lime contents at different autoclaved ages. From the results obtained it was found that the autoclaved products obtained from the autoclaved pastes with addition silica fume (SF) or nano-metakaolin (NMK) possesses improved physico-chemical and mechanical characteristics. In addition, the extent of enhancement of mechanical properties increases with increasing NMK or SF addition.

Influence of nano-silica and -metakaolin on the hydration characteristics and microstructure of air-cooled slag-blended cement mortar

This study aims at enhancing the hydration characteristics and microstructure of cement mortar (CM) containing ground air-cooled slag (ACS), using nano-silica (NS) and nano-metakaolin (NMK) powder. Firstly, ordinary Portland cement (OPC) was replaced by 0, 5, 10, 15, and 20 wt.% ground ACS. CM was designed at 3:1 of sand: OPC/ACS ratio. The water to cement (W/C) ratio was adapted at 0.47. It was found that the CM containing 5 wt.% ACS showed the highest compressive strength and free lime content at 90-day of hydration. Meanwhile, significant reduction in compressive strength and free lime values was observed in case of CM containing 20 wt.% ACS. Different NS and NMK percentages (2, 4, 6 and 8 wt.%) were individually added to CM containing 20 wt.% ACS, in order to enhance its chemical and physico-mechanical properties. The results showed that the addition of 6 wt.% NS and 4 wt.% NMK led to increase the compressive strength of ACS-blended CM by ~116 and 42%, respectively, compared to the control sample (without ACS). The hydration products were identified using X-ray diffraction, differential thermal analysis, thermogravimetric analysis, and scanning electron microscopy.

Influence of carbon nanotubes, nanosilica and nanometakaolin on some morphological-mechanical properties of oil well cement pastes subjected to elevated water curing temperature and regular room air curing temperature

Nanotechnology has shown great potential in different applications and presents solutions to some of the upstream and downstream challenges in the oil and gas industry. This research work aimed to improve the mechanical properties of oil well cement (OWC) pastes using multiwall carbon nanotubes (CNTs), nano-silica (NS) and nano-metakaolin (NMK). The effect of different curing temperatures, namely; room temperature and elevated temperature (90°C) on the hydration reaction of OWC pastes admixed with different nano materials was investigated. XRD, TG/DTG, and SEM techniques were used to investigate the phase composition and the microstructure of some selected hardened specimens. The obtained results indicated that all of the nano materials used in this study cause a notable improvement in the mechanical properties of hardened OWC pastes at both curing temperatures. In addition, NMK – OWC hardened pastes present the highest improvement in the mechanical properties among all of other tested mixes.

Inclusion of nano metakaolin as additive in ultra high performance concrete (UHPC)

The utilisation of nano particles to enhance concrete can be seen in its densification and refining. In this study, nano metakaolined UHPC mixes were used as an additive range of 1%, 3%, 5%, 7%, 9% and 10% from cement weight. All UHPC specimens were compared to the plain UHPC and metakaolined UHPC mixes. The effect of nano metakaolined UHPC was evaluated in the forms of workability in fresh state, strength property and the morphology of the microstructure in the UHPC. The determination of the fresh property was conducted by a workability test. Meanwhile, the strength property was conducted by compressive strength in 3, 7 and 28days. Next, the morphology in the UHPC microstructure was analysed by Scanning Electron Microscope (SEM). The uniqueness and difference morphology formation was analysed and compared to the plain UHPC. It can then be concluded that the nano metakaolined UHPC mix contributed to a low workability effect due to its clay properties and ultrafine size as compared to the OPC and metakaolin. The inclusion of nano metakaolin in UHPC shows similar compressive strength at early age but gradually increased at later ages as compared to the plain UHPC and metakaolined UHPC.

Enhanced physical, mechanical and microstructural properties of lightweight vermiculite cement composites modified with nano metakaolin

This article presents a study on the influence of nano metakaolin (NMK) on physical, mechanical and microstructural properties of high volume vermiculite blended white Portland cement (WPC). WPC was replaced with 70 vol% expanded vermiculite (EVM), NMK were incorporated at a rate of 2, 4, 6, 8 and 10% as partial replacement by weight of EVM. The density, thermal conductivity, compressive strength, flexural strength, and capillary water absorption of the blended mixes were determined in accordance with ASTM standards at 28days of curing. Differential scanning calorimeter (DSC) was used to study the phase transitions. The microstructure characteristics of the hardened samples were investigated by scanning electron microscope (SEM). The experimental results revealed a significant enhancement in both compressive and flexural strength, enhancements of about 57 and 59%, respectively were obtained at 10% NMK replacement. The capillary water absorption generally decreases with increasing replacements of EVM by NMK. A considerable decrease of about 74% was observed at 10% NMK. No significant effect of the NMK content on density and thermal conductivity. NMK led to noticeable improvement in the microstructure characteristics of the hardened blends.

Effect of Sulfate in Sand on Some Mechanical Properties of Nano Metakaolin Normal Concrete

Effect of Sulfate in Sand on Some Mechanical Properties of Nano Metakaolin Normal Concrete

Thermo-physical properties of nanostructured lightweight fiber reinforced cementitious composites

Cementitious materials are widely used for cladding of the building envelopes; however, they possess low thermal resistivity, low tensile strength and ductility which leading to cracking with time. It would be advantageous to improve thermal resistivity of lightweight cementitious materials whilst keeping their mechanical performance acceptable/reasonable. This study represents an extension to a work that has investigated the role of nano metakaolin (NMK) in enhancing the flexural strength of fiber reinforced cementitious composites (FRCC). An optimum composite of NMK – modified FRCC was determined. The aim of this study is to develop nanostructured lightweight fiber reinforced cementitious surface composites (NLWFRCC) with improved thermal properties and reasonable mechanical strength. For this purpose; white Portland cement (WPC) was partially replaced with different amounts of perlite ranging from 10% up to 70% by volume of cement then substituted by 10% nano metakaolin. Natural fibers were added by 2% by mass of binder. The bulk density, thermal conductivity, solar reflectivity, flexural strength, and capillary water absorption were determined in accordance to ASTM standards at 28days of curing. The microstructure characteristics of the hardened NLWFRCC were investigated by scanning electron microscope (SEM). It was found that the density, thermal conductivity and flexural strength decrease with increasing replacements of cement by perlite, thermal conductivity at 70% perlite is 6.3 times less than the composite with no perlite (plain). Even at 70% Perlite; the developed NLWRFCC still retaining sufficient strength. Incorporating perlite into WPC, led to a significant enhancement in reflectivity especially in near infrared region; an increase of about 33% was obtained at 70% perlite.

Hydration characteristics and compressive strength of hardened cement pastes containing nano-metakaolin

In this study the effect of inclusion of nano-metakaolin (NMK) to ordinary Portland cement (OPC) on the hydration characteristics and microstructure of hardened OPC–NMK pastes was studied. The OPC–NMK blends were prepared by the partial substitution of OPC by NMK (4, 6, 10 and 15 weight %). The fresh pastes were made using an initial water/solid (W/S) ratio of 0.27 by weight and then hydrated for various time intervals. At the end of each hydration time, the hardened blended cement pastes were tested for compressive strength, free lime content, combined water content, X-ray diffraction (XRD) analysis, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The compressive strength results revealed that the inclusion of nano-metakaolin into OPC improved the mechanical properties of NMK–OPC pastes during almost all ages of hydration, especially with the paste containing 10 wt% NMK. The compressive strength values obtained for OPC paste blended with 4% silica fume (SF) and 6% NMK are comparable to those of the neat OPC paste. The DSC thermograms and XRD diffractograms obtained for some selected hardened pastes indicated the formation of amorphous calcium silicate hydrates, calcium sulfoaluminate hydrates, calcium aluminate hydrate and calcium hydroxide. SEM micrographs showed the formation of a dense microstructure for the hardened OPC–NMK and OPC–NMK-SF pastes as compared to the neat OPC paste after 90days of hydration.

Pozzolanic and hydraulic activity of nano-metakaolin

Nano-metakaolin (NMK) was prepared by firing of Nano-kaolin (NK) at different temperatures (750–825°C) for 2h. The pozzolanic activities of NMK samples were studied using hydrated lime as an activator. The optimum firing temperature of metakaolin (MK) was established from the results of hydration kinetics and differential scanning calorimetry (DSC) and found to be 750°C; NMK, thus produced, is designated as NMK(750). This was based on the marked consumption of free calcium hydroxide by NMK fired at 750°C as well as the highest values of chemically combined water at all ages of hydration. Therefore, NMK(750) was used for partial replacement of OPC and studying the physico–mechanical properties of OPC–NMK blended cement pastes. The optimum substitution of OPC by NMK was found to be 8–10%. This was based on the development of compressive strength of the various hardened OPC–NMK blended cement pastes having different NMK contents (0–16%), where the strength increases with NMK content up to 10% and then decreases. In addition, the SEM micrographs obtained for the hardened OPC (93%)–NMK (7%) blended cement paste displayed the formation of amorphous and microcrystalline CSH which fill the pores leading to a more dense structure with higher hydraulic activity as compared to neat OPC paste.

Effect of nano-metakaolin addition on the hydration characteristics of fly ash blended cement mortar

The effect of nano-metakaolin (NMK) addition on hydration characteristics of fly ash (FA) blended cement mortar was experimentally investigated. The amorphous or glassy silica, which is the major component of a pozzolan, reacts with the calcium hydroxide liberated during calcium silicate hydration. It is believable to add FA and NMK particles in order to make high performance concrete. The physico-mechanical properties of FA blended cement mortars made with different percentages of NMK were investigated. The experimental results showed that the compressive and flexural strengths of mortars containing NMK are higher than those of FA blended cement mortar at 60 days of hydration age. It is demonstrated that the nanoparticles enhances strength than FA. In addition, the hydration process was monitored using scanning electron microscopy and thermal gravimetric analysis (TG). The results of these examinations indicate that NMK behaves not only as a filler to improve microstructure, but also as an activator to promote the pozzolanic reaction.

Physico-mechanical characteristics of blended white cement pastes containing thermally activated ultrafine nano clays

The aim of this work is to produce highly active and amorphous nano sized pozzolana by means of thermal activation of nano clays and to utilize the thermally activated nano clays as additives in white Portland cement pastes (WPC) to improve their thermo mechanical properties. Nano-kaolin was thermally treated at 750°C for 2h to get active activated nano-metakaolin (NMK). The effect of thermal activation on the dehydroxylation of the nano-kaolin was determined by using different techniques such as; X-ray diffraction spectroscopy (XRD) and differential thermal analysis (DTA). The surface morphologies of both nano-kaolin and NMK were studied by transmission electron microscopy (TEM).NMK were incorporated at a rate of 2%, 4%, 6%, 8%, 10%, 12% and 14% by weight of cement. Hardened blended cement pastes were prepared by using water/cement ratio (W/C) of 0.3 by weight and hydrated for various curing ages 3, 7 and 28days. In order to study the mechanical and physical characteristics of the hardened cement pastes incorporating NMK, different techniques were used such as compressive and flexural strength testing, differential scanning calorimeter (DSC), X-ray diffraction (XRD) and scanning electron microscope (SEM). The experimental results of this study showed that thermal activation of the nano kaolin leads to transformation of the kaolinite to amorphous phase accompanied with the reduction in grain size. The partial replacement of cement by NMK is helpful in enhancing the compressive and flexural strength of cement products. There was an enhancement of compressive strength by about 50% and flexural strength by 36% at 10% nanoclay. The microstructure of the cement blended with NMK was denser, compact and more uniform than that of the conventional cement.

Flexural strength and physical properties of fiber reinforced nano metakaolin cementitious surface compound

This study aimed at investigating the role of nano metakaolin (NMK) for enhancing the flexural strength and reducing the capillary water absorption of fiber-reinforced cementitious composites (FRCCs) for building surface plastering. Short natural fibers were added to white Portland cement (WPC) by different amounts of 0.5%, 1%, 1.5%, 2%, 2.5% and 3% by weight of cement. All samples were cured in water. It was found that as the amount of fiber increases the flexural strength increases up to about 2% by 82%, then after, a decrease in flexural strength was observed. The capillary water absorption increases with increasing fiber percent. In order to develop fiber reinforced nano-cementitious composite, different percentages of NMK ranging from 2% to 14% were used with the replacement of cement keeping constant fiber content of 2%. The phase composition and microstructure of the formed hydrates were studied using thermogravimetric analysis (TGA), X-ray diffraction (XRD) & scanning electron microscope (SEM). Additional increase in the flexural strength by about 67% was achieved at 10% NMK content. The capillary water absorption generally decreases with increasing replacements of cement by NMK. A decrease of about 50% was observed at 10% NMK.

The Effect of Nano Metakaolin Material on Some Properties of Concrete

This investigation aimed to study the effect of nano metakaolin ( NMK ) on some properties (compressive strength ,splitting tensile strength & water absorption ) of concrete. The nano metakaolin (NMK) was prepared by thermal activation of kaolin clay for 2 hours at 750 Ċ. The cement used in this investigation consists of ordinary Portland cement (OPC). The OPC was partially substituted by NMK of ( 3, 5 & 10%) by weight of cement. The C45 concrete was prepared , using water/cement ratio ( W/c) of (0.53) .The Water absorption was tested at 28 days while the tests (compressive strength ,splitting tensile strength) were tested at ages of (7, 28, 60,& 90) days . The compressive strength and splitting tensile strength of concrete with NMK were higher than that of reference concrete with the same W/c ratio.The improvement in the compressive strength when using NMK was (42.2, 55.8 , 63.1% ) at age 28 days for ( 3%, 5%, &10% ) replacement of NMK respectively whereas the improvement in the splitting tensile strength was (0% , 36% & 46.8 %) at age of 28 days when using (3%, 5%, &10% ) NMK respectively. The improvement in the water absorption was (16.6%, 21.79%, &25.6 ) when using (3, 5, &10% )NMK.

Thermo-Mechanical Characteristics of Blended White Cement Pastes Containing Ultrafine Nano Clays

Abstract The aim of this work was to produce highly active and amorphous nano sized pozzolana by means of thermal activation of nanoclays and to utilize the thermally activated nanoclays as additives in white Portland cement pastes (WPC) to improve their thermo mechanical properties. The nanoclay used in this investigation is kaolin clay. The nano Kaolin was thermally treated at 750°C for 2 h to obtain active amorphous nano metakaolin (NMK). The effect of thermal activation on the dehydroxylation of the kaolin and the surface morphology of the resulting amorphous NMK were determined by using different techniques: X-ray diffraction spectroscopy (XRD), differential thermal analysis (DTA) and Transmission electron microscopy (TEM). NMK were incorporated at a rate of 2, 4, 6, 8, 10, 12, and 14% by weight of cement. Hardened blended cement pastes were prepared by using water/cement ratio (W/C) of 0.3 by weight and hydrated for various curing ages 3, 7, and 28 days. In order to study the mechanical and physical characteristics of the hardened cement pastes incorporating NMK, different techniques were used such as compressive and flexure strength testing, differential scanning calorimeter (DSC), x-ray diffraction (XRD), and scanning electron microscope (SEM). The experimental results of this study showed that thermal activation of the nano kaolin leads to transformation of the kaolinite to amorphous phase accompanied with the reduction in grain size. The partial replacement of cement by NMK is helpful in enhancing the compressive and flexure strength of cement products. There was an enhancement of compressive strength by about 50% and flexure strength by 36% at 10% nanoclay. The microstructure of the cement blended with NMK was denser, compact, and more uniform than that of the conventional cement microstructure.

Behavior of blended cement mortars containing nano-metakaolin at elevated temperatures

The effects of high temperatures up to 800°C on the mechanical properties and microstructure of nano-metakaolin cement mortars were investigated in this study. The blended cement used in this investigation is ordinary Portland cement (OPC) containing nano-metakaolin (NMK). The nano-metakaolin was prepared by thermal activation of nano kaolin clay at 750°C for 2h. The mortar was prepared using blended cement: sand ratio of 1:3 and water/binder ratio of 0.6. The cement mortar pastes were cured under water for 28days; then dried at 105±5°C for 24h and then exposed to 250, 450, 600 and 800°C for 2h. The compressive and flexural strengths were measured for blended cement mortar and compared with the strength of pure OPC mortar. It was found that after an initial increase in compressive strength at 250°C for the mortar specimens, the strength decreased considerably at higher temperatures.

Hybrid effect of carbon nanotube and nano-clay on physico-mechanical properties of cement mortar

In this work, several nanomaterials have been used in cementitious matrices: multi wall carbon nanotubes (MWCNTs) and nano-clays. The physico-mechanical behavior of these nanomaterials and ordinary Portland cement (OPC) was studied. The nano-clay used in this investigation was nano-kaolin. The metakaolin was prepared by thermal activation of nano-kaolin clay at 750 °C for 2 h. The organic ammonium chloride was used to aid in the exfoliation of the clay platelets. The blended cement used in this investigation consists of ordinary Portland cement, carbon nanotubes and exfoliated nano metakaolin. The OPC was substituted by 6 wt.% of cement by nano metakaolin (NMK) and the carbon nanotube was added by ratios of 0.005, 0.02, 0.05 and 0.1 wt.% of cement. The blended cement: sand ratio used in this investigation was 1:2 wt.%. The blended cement mortar was prepared using water/binder ratio of 0.5 wt.% of cement. The fresh mortar pastes were first cured at 100% relative humidity for 24 h and then cured in water for 28 days. Compressive strength, phase composition and microstructure of blended cement were investigated. The results showed that, the replacement of OPC by 6 wt.% NMK increases the compressive strength of blended mortar by 18% compared to control mix and the combination of 6 wt.% NMK and 0.02 wt.% CNTs increased the compressive strength by 29% than control.