EFFECT OF DIFFERENT NANOPARTICLES ON PHYSICAL AND

MECHANICAL PROPERTIES OF CONCRETE

A Seminar report

Submitted toCivil Engineering Department

GUDLAVALLERU ENGINEERING COLLEGE

In partial fulfillment of the requirements for the award of the degree of

MASTER OF TECHNOLOGY

IN

STRUCTURAL ENGINEERINGSubmitted By

SYED JEELANI BASHA14481D8720

Under the Guidance of

K SAILAJAAsst. Professor

DEPARTMENT OF CIVIL ENGINEERING

GUDLAVALLERU ENGINEERING COLLEGEAn Autonomous Institute with permanent affiliation to JNTUK, Kakinada

SeshadhriRao Knowledge Village

Gudlavalleru-521356

2015-2016

Title: Effect of different nanoparticles on physical and mechanical properties of concrete.

Abstract:

Nanoparticles like Al2O3, MnFe2O4, TiO2 and ZrO2 are used in this investigation. Nanoparticles with partial replacement of cement by 0.5 to 2 weight percent have been used as reinforcement. The results indicate that the strength and the resistance to water permeability of the specimens are improved by adding nanoparticles in the cement paste up to 2.0 wt. (%).Nanoparticles, as a result of increased crystalline Ca(OH)2 amount especially at the early age of hydration, could accelerate C-S-H gel formation and hence increase the strength of the concrete specimens. In addition, nanoparticles are able to act as nanofillers and recover the pore structure of the specimens by decreasing harmful pores. Curing of the specimens has been carried out in water for 7, 28 and 90 days after casting. Several empirical relationships have been presented to predict split tensile strength of the specimens by means of the corresponding compressive strength at a certain age of curing. In this study, Nanoparticles could improve mechanical and physical properties of the concrete specimens.

Introduction:Nanotechnology is the re-engineering of materials by controlling the matter at the atomic level, basic physics and chemistry research, where the phenomena on atomic and molecular levels are used to provide materials and structures that perform tasks that are not possible using the materials in their typical macroscopic form.Nanotechnology is the use of very small pieces of material by themselves or their manipulation to create new large scale materials. At the Nano-scale material properties are altered from that of larger scales. The Nano-scale is the size range from approximately1nm to 100nm. Nanotechnology is an enabling technology that allows us to develop materials with improved or totally new properties.

Nano technology is the world of the small and the smallest parts, of micro and nanotechnologies. The discovery of this world is, of course, not a recent one, but one which began a long time ago. The ancient Greeks imagined the atom as the smallest unit which could not be split. There then followed a long evolution comprising several different stages before the eventual development of the quantum mechanics model. Recently, a very important step was taken to improve the technology of microscopes. At last we are able to see atoms (in some ways this was already possible with the invention of transmission electron microscopy). However, now we can also manipulate them individually, change their position one by one and use them to create a new code; this is a difficult task but nevertheless it is possible. In fact, we can only create something we can actually see.

In the beginning, there were only two dimensions in nanotechnologies. Specialists in optics then created almost perfect surfaces. The difficulty lay, and still lies, in how to deal with the third dimension. Specialists in electronics working with integrated circuits took part in the miniaturization race going from micro to sub micro dimensions, all the while getting closer and closer to the nanometer. Once they reach the stage where they will finally be using a single electron as the basis of electronics. This evolution does not only concern electronics, since other fields of study such as mechanics, optics, chemistry and biology have also started creating their own nano world; today we refer to these as micro systems. The first example of mass production of micro systems which was not purely electronic was the silicon accelerometer of airbags which can be found in the majority of cars. On the contrary, nano systems do not yet exist. It will still take some time before they make it out of the laboratories. The nano world is part of our world, but in order to understand this, concepts other than the normal ones, such as force, speed, weight, etc., must be taken into consideration. The nano world is subject to the laws of quantum physics, yet evolution has conditioned us to adapt to this ever changing world. This observation has led us to further investigate theories based on the laws of physics that deal with macroscopic phenomena.

New objects

Given their size, nanoobjects have specific qualities which prove useful in a number of different applications. Structures with new properties possessing the properties similar to those of both a molecule and a solid are being discovered. In order to illustrate this, the beginning of this chapter will deal with two nano jewels.

Carbon in all its states

The carbon atom, with an atomic mass of 12 and with six protons and six neutrons, is the sixth heaviest element. Its exceptional properties, which are due to its four bonding electrons, explain the importance of its role in the natural world. It exists in all molecules; molecules being the building blocks of flora and fauna. The vast majority of these molecules are unreachable by chemical synthesis. For the moment, we can only admire and use these natural products that have developed throughout the process of evolution.

Nanoparticles:

It is defined as a particle with at least one dimension less than200nm. Nano-particles made of semiconducting material.

Nanocomposites:

It is produced by adding Nano particle to bulk material in order to improve its bulk properties.

Nanodiamonds:

Produced by plasma spraying techniques1, nanodiamonds are made of thousands of atoms and their enhanced hardness is used to create specific coatings. After the nanodiamonds are treated with luminescent properties, they are used as a single photon source for the study of quantum cryptography. Coated with active molecules from the natural world, these nano crystals will make excellent biological markers for analysis in the field of confocal microscopy.

Carbon nanotubes:

Carbon nanotubes are the most well-known of the nanostructures. Originally, the electric-arc vaporization of carbon atoms, or the laser radiation of atoms, produced some strange structures. The most well-known is fullerene C60, made of 60 carbon atoms whose structure resembles that of a soccer ball.The conditions required in order to obtain closed and roll structures were met very quickly. These single or multi walled rolls in the form of tubes with a diameter of a few nanometers, as well as the remarkable physical and chemical characteristics of the atomic grids, enable scientists to use them in numerous fields of scientific study. Their mechanical qualities (ten times harder than iron) enhance the resistance of textiles and composite plastic materials when they are inserted as adjuvants, just like an iron framework in concrete.

Nanotechnology in Construction:

The construction industry was the only industry to identify nanotechnology as a promising emerging technology in the UK Delphi survey in the early 1990s .The importance of nanotechnology was also highlighted in foresight reports of Swedish and UK construction. Furthermore, ready mix concrete and concrete products were identified as among the top 40 industrial sectors likely to be influenced by nanotechnology in 10-15 years. However, construction has lagged behind other industrial sectors where nanotechnology R&D has attracted significant interest and investment from large industrial corporations and venture capitalists.

Nano-SiO2 could significantly increase the early-age compressive strength of high volume fly ash concrete, which has early age strength gain characteristics similar to that of belite cement concrete. Modeling of the C-S-H gel is done through nano indention type methods, and using these type methods two distinct C-S-H forms have been identified. The amount and type of C-S-H in a mix can be used to predict the resulting properties of the cement pastes. It is difficult to investigate the nanostructure of C-S-H with typical methods.

Nanotechnology tools can also be used to monitor the progress of the cement hydration reaction, which can be useful in evaluating admixtures or processes such as thermal degradation and enhance the knowledge of developmental properties of concrete. Being able to see the cement reaction over time also has the potential to provide for the development of new materials for controlled delivery of admixtures in concrete.

Particle size and specific surface area related to concrete materials

Materials used partial replacement of cement

Silicon dioxide:

Nano-SiO2 could significantly increase the compressive strength of concretes containing large fly ash volume at early age, by filling the pores between large fly ash and cement particles. Nano-silica decreases the setting time of mortar when compared with silica fume (micro silica) and reduces bleeding water and segregation by the improvement of the cohesiveness.Applications:

Nano silica is only used in the high performance concretes (HPC), eco-concretes and self-compacting concretes (SSC) because of their high cost.

Nano-silica is applied in HPC and SCC concrete mainly as an anti-bleeding agent.

It is also added to increase the cohesiveness of concrete and to reduce the segregation tendency.By adding nano silica to eco-concrete mixes to obtain an accelerated setting and higher compressive strength.

Aluminium oxide:

Aluminium oxide is a chemical compound of aluminium and oxygen with the chemical formula Al2 O3. It is the most commonly occurring of several aluminium oxides, and specifically identified as aluminium (III) oxide. It is commonly called alumina, and may also be called aloxide, aloxite, or alundum depending on particular forms or applications. It occurs naturally in its crystalline polymorphic phase α-Al2O3 as the mineral corundum, varieties of which form the precious gemstones ruby and sapphire. Al2O3 is significant in its use to produce alu-minium metal, as an abrasive owing to its hardness, and as a refractory material owing to its high melting point.

Natural occurrence:

Corundum is the most common naturally occurring crystalline form of aluminium oxide. Rubies and sapphires are gem-quality forms of corundum, which owe their characteristic colors to trace impurities. Rubies are given their characteristic deep red color and their laser qualities by traces of chromium. Sapphires come in different colors given by various other impurities, such as iron and titanium.

Properties

Al2O3 is an electrical insulator but has a relatively high thermal conductivity (30 Wm−1K−1) for a ceramic material. Aluminium oxide is insoluble in water. In its most commonly occurring crystalline form, called corundum or α-aluminium oxide, its hardness makes it suitable for use as an abrasive and as a component in cutting tools.

Aluminium oxide is responsible for the resistance of metallic aluminium to weathering. Metallic aluminium is very reactive with atmospheric oxygen, and a thin passivation layer of aluminium oxide (4 nm thickness) forms on any exposed aluminium surface. This layer protects the metal from further oxidation. The thickness and properties of this oxide layer can be enhanced using a process called anodising. A number of alloys, such as aluminium bronzes, exploits this property by including a proportion of aluminium in the alloy to enhance corrosion resistance. The aluminium oxide generated by anodising is typically amorphous, but discharge assisted oxidation processes such as plasma electrolytic oxidation result in a significant proportion of crystalline aluminium oxide in the coating, enhancing its hardness.

The Al2O3 nanoparticles with average diameter of 45 to 50 nm and average surface area of 30 m2/g.

Diameter(nm)Surface volume Density

purity % make(m2/gm) (gm/cm3)

(40-50) 32-40 < 0.1 % > 99.5%Alfa

Aesar

Applications

The great majority of aluminium oxide is consumed for the production of aluminium, usually by the Hall–Héroult process.

1. Filler

Being fairly chemically inert and white, aluminium oxide is a favored filler for plastics. Aluminium oxide is a com-mon ingredient in sunscreen and is sometimes present in cosmetics such as blush, lipstick, and nail polish.2. Glass

Many formulations of glass have aluminium oxide as an ingredient.

3. CatalysesAluminium oxide catalyses a variety of reactions that is useful industrially. In its largest

scale application, aluminium oxide is the catalyst in the Claus process for converting hydrogen sulfide waste gases into elemental sulfur in refineries. It is also useful for dehydration of alcohols to alkenes.

Aluminium oxide serves as a catalyst support for many industrial catalysts, such as those used in hydrode sulfurization and some Ziegler-Natta polymerizations.

4. PurificationAluminium oxide is widely used to remove water from gas streams.

5. AbrasiveAluminium oxide is used for its hardness and strength. It is widely used as an abrasive,

including as a much less expensive substitute for industrial diamond. Many types of sandpaper use aluminium oxide crystals. In addition, its low heat retention and low specific heat make it widely used in grinding operations, particularly cutoff tools. As the powdery abrasive mineral aloxite, it is a major component, along with silica, of the cue tip “chalk” used in billiards. Aluminium oxide powder is used in some CD/ DVD polishing and scratch-repair kits. Its polish-ing qualities are also behind its use in toothpaste. Aluminium oxide can be grown as a coating on aluminium by anodising or by plasma electrolytic oxidation. Both its hardness (9 on the Mohs scale of mineral hardness) and abrasive characteristics originate from the high strength of aluminium oxide.

6. PaintAluminium oxide flakes are used in paint for reflective decorative effects, such as in the

automotive or cosmetic industries.

7. Composite fiberAluminium oxide has been used in a few experimental and commercial fiber materials for

high-performance applications (e.g., Fiber FP, Nextel 610, Nextel 720). Alumina nanofibers in particular have become a research field of interest.

8. Abrasion protectionAlumina is used to manufacture tiles which are attached inside pulverized fuel lines and

flue gas ducting on coal fired power stations to protect high wear areas. They are not suitable for areas with high impact forces as these tiles are brittle and susceptible to breakage

Iron oxide:

Iron(III) oxide or ferric oxide is the inorganic com pound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare, and iron(II,III) oxide (Fe3O4), which also occurs naturally as the mineral magnetite. As the mineral known as hematite, Fe2O3 is the main source of iron for the steel industry. Fe2O3 is ferromagnetic, dark red, and readily attacked by acids. Iron(III) oxide is often called rust, and to some extent this label is useful, because rust shares several properties and has a similar composition. To a chemist, rust is considered an ill-defined material, described as hydrated ferric oxide.

Structure:Fe2O3 can be obtained in various polymorphs. In the main ones, α and γ, iron adopts octahedral coordination geometry. That is, each Fe center is bound to six oxygen ligands.

Alpha phase

α-Fe2O3 has the rhombohedral, corundum (α-Al2 O3) structure and is the most common form. It occurs naturally as the mineral hematite which is mined as the main ore of iron. It is antiferromagnetic below ~260 K (Morin transition temperature), and exhibits weak ferromagnetism between 260 K and the Néel temperature, 950 K. It is easy to prepare using both thermal decomposition and precipitation in the liquid phase. Its magnetic properties are dependent on many factors, e.g. pressure, particle size, and magnetic field intensity.

Gamma phase

γ-Fe2O3 has a cubic structure. It is metastable and converted from the alpha phase at high temperatures. It occurs naturally as the mineral maghemite. It is ferromagnetic and finds application in recording tapes, although ultrafine particles smaller than 10 nanometers are superparamagnetic. It can be prepared by thermal dehydratation of gamma iron(III) oxide-hydroxide, careful oxidation of iron(II,III) oxide. Another method involves the careful oxidation of Fe3O4. The ultrafine particles

Other phasesSeveral other phases have been identified or claimed. The β-phase is cubic body centered,

metastable, and at temperatures above 500 °C (930 °F) converts to alpha phase. It can be prepared by reduction of hematite by carbon, pyrolysis of iron (III) chlo ride solution, or thermal decomposition of iron (III) sulfate. The epsilon phase is rhombic, and shows properties intermediate between alpha and gamma, and may have useful magnetic properties. Preparation of the pure epsilon phase has proven very challenging due to contamination with alpha and gamma phases. Material with a high proportion of epsilon phase can be prepared by thermal transformation of the gamma phase. This phase is also metastable, transforming to the alpha phase at between 500 and 750 °C (930 and 1,380 °F). Can also be prepared by oxidation of iron in an electric arc or by sol- gel precipitation from iron(III) nitrate. Additionally at high pressure an amorphous form is claimed. Recent research has revealed epsilon iron(III) oxide in ancient Chinese Jian ceramic glazes, which may provide insight into ways to produce that form in the lab.

The Fe2O4 nanoparticles with average diameter of 50 nm and average surface area of 28 m2/g were prepared by citrate nitrate auto combustion method.

Applications:

1. Iron industries

The overwhelming application of iron(III) oxide is as the feedstock of the steel and iron industries, e.g. the production of iron, steel, and many alloys.

2. Polishing

A very fine powder of ferric oxide is known as “jeweler’s rouge”, “red rouge”, or simply rouge. It is used to put the final polish on metallic jewelry and lenses, and historically as a cosmetic. Rouge cuts more slowly than some modern polishes, such as cerium (IV) oxide, but

is still used in optics fabrication and by jewelers for the superior finish it can produce. When polishing gold, the rouge slightly stains the gold, which contributes to the appearance of the finished piece. Rouge is sold as a powder, paste, laced on polishing cloths, or solid bar (with a wax or grease binder). Other polishing compounds are also often called “rouge”, even when they do not contain iron oxide. Jewelers remove the residual rouge on jewelry by use of ultrasonic cleaning. Products sold as " stropping compound” are often applied to a leather strop to assist in getting a razor edge on knives, straight razors, or any other edged tool.

3. PigmentTwo different colors at different hydrate phase (α = red, β = yellow) of iron (III) oxide

hydrate and they are useful as a pigment.

4. Magnetic recordingIron(III) oxide was the most common magnetic particle used in all types of magnetic

storage and recording media, including magnetic disks (for data storage) and magnetic tape (used in audio and video recording as well as data storage). However, modern magnetic storage media - in particular, the hard disk drives - use more advanced thin film technology, which may consist of a stack of 15 layers or more.

5. Photo catalystsα-Fe2O3 has been studied as a photo anode for the water-splitting reaction for over 25

years.6. Medicine

A mixture of zinc oxide with about 0.5% iron (III) oxide is called calamine, which is the active ingredient of calamine lotion.

Titanium dioxide:

Titanium dioxide, also known as titanium (IV) oxide or titania, is the naturally occurring oxide of titanium, chemical formula TiO

When used as a pigment, it is called titanium white.

Titanium dioxide occurs in nature as the well-known minerals rutile, anatase and brookite, and additionally as two high pressure forms, a monoclinic baddeleyite-like form and an orthorhombic α-PbO 2-like form, both found recently at the Ries crater in Bavaria. It is mainly sourced from ilmenite ore. This is the most widespread form of titanium dioxide-bearing ore around the world.

Nanotubes:Anatase can be converted by hydrothermal synthesis to delaminated anatase inorganic nanotubes

and titanate nanoribbons which are of potential interest as catalytic supports and photocatalysts. In the synthesis, anatase is mixed with 10 M sodium hydroxide and heated at 130 °C (266 °F) for 72 hours. The reaction product is washed with dilute hydrochloric acid and

heated at 400 °C (752 °F) for another 15 hours. The yield of nanotubes is quan-titative and the tubes have an outer diameter of 10 to 20 nm and an inner diameter of 5 to 8 nm and have a length of 1 μm. A higher reaction temperature (170 °C) and less reaction volume give the corresponding nanowires.

Another process for synthesizing TiO2 nanotubes is through anodization in an electrolytic solution. When anodized in a 0.5 weight percent HF solution for 20 minutes, well-aligned titanium oxide nanotube ar-rays can be fabricated with an average tube diameter of 60 nm and length of 250 nm. Based on X-ray Diffraction, nanotubes grown through anodization are amorphous. As HF is highly corrosive and harmful chemical, NH4F is now being used as the etching agent in lieu of HF. In a typical synthesis process, a formamide based non aqueous electrolyte is produced containing 0.2M NH4F and 5 vol% of DI water. The anodization process is carried out under 25V at 20oC for 20 hours, in a two electrode electrochemical cell consisting of a highly pure and thoroughly cleaned titanium plate as the anode, a copper plate or platinum wire as the cathode and the aforesaid electrolyte. The as prepared sample is annealed in air at 400oC to get anatase phase.

The ZrO2nanoparticles with average diameter of 15 to 20 nm and average surface area of 45 m2/g.

ApplicationsThe most important application areas are paints and var-nishes as well as paper and plastics, which account for about 80% of the world’s titanium dioxide consumption. Other pigment applications such as printing inks, fibers, rubber, cosmetic products and foodstuffs account for an-other 8%. The rest is used in other applications, for in-stance the production of technical pure titanium, glass and glass ceramics, electrical ceramics, catalysts, electric conductors and chemical intermediates. It also is in most red-coloured candy.

1. PigmentTitanium dioxide is the most widely used white pigment because of its brightness and

very high refractive index, in which it is surpassed only by a few other materials. Approximately 4.6 million tons of pigmentary TiO2 are used annually worldwide, and this number is expected to increase as utilization continues to rise. When de-posited as a thin film, its refractive index and colour make it an excellent reflective optical coating for dielectric mirrors and some gemstones like “mystic fire topaz". TiO2 is also an effective opacifier in powder form, where it is employed as a pigment to provide whiteness and opacity to products such as paints, coatings, plastics, papers, inks, foods, medicines (i.e. pills and tablets) as well as most toothpastes. In paint, it is often referred to offhandedly as “the perfect white”, “the whitest white”, or other similar terms. Opacity is improved by optimal sizing of the titanium dioxide particles. Some grades of titanium based pigments as used in sparkly paints, plastics, finishes and pearlescent cosmetics are man-made pigments whose particles have two or more layers of various oxides – of-ten titanium dioxide, iron oxide or alumina – in order to have glittering, iridescent and or pearlescent effects similar to crushed mica or guanine-based products. In addition to these effects a limited colour change is possible in certain formulations depending on how and at which an-gle the finished product is illuminated and the thickness of the oxide layer in the

pigment particle; one or more colors appear by reflection while the other tones appear due to interference of the transparent titanium dioxide layers. In some products, the layer of titanium dioxide is grown in conjunction with iron oxide by calcination of titanium salts (sulfates, chlorates) around 800 °C or other industrial deposition methods such as chemical vapour deposition on substrates such as mica platelets or even silicon dioxide crystal platelets of no more than 50 µm in diameter. The iridescent effect in these titanium oxide particles (which are only partly natural) is unlike the opaque effect obtained with usual ground titanium oxide pigment obtained by mining, in which case only a certain diameter of the particle is considered and the effect is due only to scattering.In ceramic glazes titanium dioxide acts as an opacifier and seeds crystal formation.

2. Photo CatalystTitanium dioxide, particularly in the anatase form, is a photocatalyst under ultraviolet

(UV) light. It has been re-ported that titanium dioxide, when doped with nitrogen ions or doped with metal oxide like tungsten trioxide, is also a photocatalyst under either visible or UV light. The strong oxidative potential of the positive holes oxidizes water to create hydroxyl radicals. It can also oxidize oxygen or organic materials directly. Hence, in addition to its use as a pigment, titanium dioxide can be added to paints, cements, windows, tiles, or other products for its sterilizing, deodorizing and anti-fouling properties and is used as a hydrolysis catalyst. It is also used in dye-sensitized solar cells, which are a type of chemical solar cell (also known as a Graetzel cell). 3. Other applications

Titanium dioxide in solution or suspension can be used to cleave protein that contains the amino acid proline at the site where proline is present

Titanium dioxide is also used as a material in the memristor, a new electronic circuit element. It can be employed for solar energy conversion based on dye, polymer, or quantum dot sensitized nanocrystalline TiO2 solar cells using conjugated polymers as solid electrolytes.

Synthetic single crystals and films of TiO2 are used as a semiconductor, and also in Bragg-stack style dielectric mirrors owing to the high refractive index of TiO2 (2.5–2.9).

Bob Ross often used Titanium White, the pigment of titanium oxide, to paint his paintings in his TV show The Joy of Painting.

Zirconium dioxide:

Zirconium dioxide (ZrO2) sometimes known as zirconia (not to be confused with zircon), is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic crystalline structure, is the mineral baddeleyite. A dopant stabilized cubic structured zirconia, cubic zirconia, is synhesized in various colors for use as a gemstone and a diamond simulant.

The ZrO2 nanoparticles with average diameter of 15 to 20 nm and average surface area of 45 m2/g.

Applications

The main use of zirconia is in the production of ceramics, with other uses including as a protective coating on particles of titanium dioxide pigments, as a refractory material, in insulation, abrasives and enamels. Stabilized zirconia is used in oxygen sensors and fuel cell membranes because it has the ability to allow oxygen ions to move freely through the crystal structure at high temperatures. This high ionic conductivity (and a low electronic conductivity) makes it one of the most useful electroceramics. Zirconium dioxides is also used as the solid electrolyte in electrochromic devices.

Zirconia is a precursor to the electroceramic lead zirconate titanate (PZT), which is a high-K dielectric, which is found in myriad components.

1. Niche uses

The very low thermal conductivity of cubic phase of zirconia also has led to its use as a thermal barrier coating, or TBC, in jet and diesel engines to allow operation at higher temperatures. Thermodynamically, the higher the operation temperature of an engine, the greater the possible efficiency. Another low thermal conductivity use is a ceramic fiber insulation for crystal growth furnaces, fuel cell stack insulation and infrared heating systems.

This material is also used in dentistry in the manufacture of 1) Sub frames for the construction of dental restorations such as crowns and bridges, which are then veneered with a conventional feldspathic porcelain for aesthetic reasons, or of 2) Strong, extremely durable dental prostheses constructed entirely from monolithic zirconia, with limited but constantly improving aesthetics.Zirconia is used to make ceramic knives. Because of its hardness, Zirconia based cutlery stays sharp longer than a stainless steel equivalent.

Due to its infusibility and brilliant luminosity when incandescent, it was used as an ingredient of sticks for limelight.

Zirconia has been proposed to electrolyze carbon monoxide and oxygen from the atmosphere of Mars to provide both fuel and oxidizer that could be used as a store of chemical energy for use with surface transportation on Mars. Carbon monoxide/oxygen engines have been suggested for early surface transportation use as both carbon monoxide and oxygen can be straightforwardly produced by Zirconia electrolysis without requiring use of any of the Martian water resources to obtain Hydrogen, which would be needed for the production of methane or any hydrogen based fuels.Single crystals of the cubic phase of zirconia are commonly used as diamond simulant in jewellery. Like diamond, cubic zirconia has a cubic crystal structure and a high index of refraction. Visually discerning a good quality cubic zirconia gem from a diamond is diffcult, and most jewellers will have a thermal conductivity tester to identify cubic zirconia by its low thermal conductivity (diamond is a very good thermal conductor). This state of zirconia is commonly called cubic zirconia, CZ, or zircon by jewellers, but the last name is not chemically accurate. Zircon is actually the mineral name for naturally occur-ring zirconium silicate (ZrSiO4).

Results and discussions:

Split tensile test:

Sample Designation

Nano Al2O3 particle (%)

7 days

28 days

90 days

C0 (control) 0 1.8 1.9 2.2N1 0.5 2.3 2.5 2.7 N2 1.0 2.2 2.8 3.1 N3 1.5 2.4 2.6 2.9 N4 2.0 1.6 1.7 2.0

Sample Designation

Nano MnFe2O4 particle (%)

7 days

28 days

90 days

C0 (control) 0 1.6 1.7 2.4 N1 0.5 2.2 2.5 2.8 N2 1.0 2.7 3.2 3.6 N3 1.5 2.5 2.8 3.2 N4 2.0 1.7 1.9 2.6

Sample Designation

Nano TiO2 particle (%)

7 days

28 days

90 days

C0 (control) 0 1.5 1.8 2.3 N1 0.5 2.3 2.6 2.9 N2 1.0 2.8 3.0 3.3 N3 1.5 2.6 2.7 3.0 N4 2.0 1.9 1.9 2.4

Sample Designation

Nano ZrO2 particle (%)Split tensile

7 days

28 days 90 days

C0 (control) 0 1.5 1.8 2.3 N1 0.5 2.5 2.9 3.4 N2 1.0 3.0 3.3 3.6 N3 1.5 2.9 3.0 3.2 N4 2.0 2.0 2.1 2.4

Comparison of the results from the 7, 28 and 90 days samples shows that the compressive strength increases with nano-Al2O3 particles up to 1.0% replacement (N2) and then it decreases, although the results of 2.0% replacement (N4) is still higher than those of the plain cement concrete (C). It was shown that the use of 2.0% nano-Al2O3 particles decreases the compressive strength to a value which is near to the control Concrete. This may be due to the fact that the quantity of nano-Al2O3 particles present in the mix is higher than the amount required to combine with the liberated lime during the process of hydration thus leading to excess silica leaching out and causing a deficiency in strength as it replaces part of the cementitious material but does not contribute to strength. Also, it may be due to the defects generated in dispersion of nanoparticles that causes weak zones. The high enhancement of compressive strength in the B series blended concrete are due to the rapid consuming of Ca(OH)2 which was formed during hydration of Portland cement specially at early ages related to the high reactivity of nano-Al2O3 particles. As a consequence, the hydration of cement is accelerated and larger volumes of reaction products are formed.

The results show that the compressive strength increases by adding MnFe2O4 nanoparticles by 0.5 wt% replacements and then it decreases. MnFe2O4 nanoparticles accelerate consumption of crystalline Ca(OH)2 which quickly are formed into C-S-H during hydration of cement specially at early ages due to the high reactivity of these nano-particles. As a consequence, larger volumes of reaction products are formed. Moreover, MnFe 2O 4 nanoparticles act as filler for strengthening the micro structure of cement. They reduce the quantity and size of Ca(OH) 2 crystals and fill the voids of C-S-H gel structure to make the structure of hydrated product more compact.However, increasing MnFe2O 4 nanoparticles more than 0.5 wt%, the compressive strength reduces. This is because the amount of MnFe2O4 nanoparticles present in the mix is higher than the amount required to combine with the liberated lime during the process of hydration. This leads to an excess of silica leaching out and causes degradation in strength. Though, nanoparticles replace part of the cementitious material but don’t contribute in the reaction. Also, cracks generated in dispersion of nanoparticles cause weak zones

N series blended concrete are due to the rapid consuming of Ca(OH)2 which was formed during hydration of Portland cement specially at early ages related to the high reactivity of nano-TiO2 particles. As a consequence, the hydration of cement is accelerated and larger volumes of reaction products are formed. Also nano-TiO2 particles recover the particle packing density of the blended cement, directing to a reduced volume of larger pores in the cement paste.

Conclusions:

The results show that the nano-Al2O3 particles blended concrete had significantly higher compressive strength compare to that of the concrete without nano-Al2O3 particles.It is found that the cement could be advantageously replaced with nano- Al2O3 particles up to maximum limit of 2.0% with average particle sizes of 45 nm. Although, the optimal level of nano-Al2O3 particles content was achieved with 1.0% replacement. Partial replacement of cement by nano-Al2O3 particles decreased workability of fresh concrete; therefore use of super plasticizer is substantial.

The results showed that concrete specimen reinforced with MnFe2O4 nanoparticles had higher compressive strength compared to that of the concrete without MnFe2O4 nanoparticles. It was found that the cement could be advantageously doped with MnFe2O4 nanoparticles up to maximum limit of 1% by weight of cement with average diameter of 49 nm. However, the maximum value of compressive strength was achieved with 0.5 wt% doped MnFe2O4 nanoparticles. The addition of MnFe2O 4 nanoparticles with 1.5 wt% and 2 wt% led to a compressive strength lower than the control specimen.

The pore structure of self-compacting concrete containing MnFe2O4 nanoparticles was improved and the volume of all mesopores and macropores was decreased.

Thermogravimetric analysis showed that MnFe2O4 nanoparticles decreased the weight loss of the specimens when they were added to concrete with 0.5 wt%. More rapid formation of hydrated products in the presence of MnFe2O4 nanoparticles which was confirmed by these results could be the reason for minimizing weight loss.

The results show that the nano-TiO2 particles blended concrete had higher compressive strength compared to that of the concrete without nano-TiO2 particles. It is found that the cement could be advantageously replaced with nano-TiO2 particles up to maximum limit of 2.0% with average particle sizes of 15 nm when the specimens cured at saturated limewater for 28 days. The optimal level of nano-TiO2 particles content was achieved with 1.0% replacement for the specimens cured in water 7, 28 and 90 days.

As the content of ZrO2 nanoparticles is increased up to 2 wt%, the compressive strength, split tensile strength and flexural strength of SCC specimens is increased. This is due to more formation of hydrated products in presence of ZrO2 nanoparticles.

ZrO2 nanoparticles could act as nanofillers and improve the resistance to water permeability of concrete at 7 and 28 days and curing. At 2 days of curing, the coefficient of water absorption is

increased by increasing the nanoparticles content up to 2.0 wt. (%) since the specimens require more water to rapid forming of hydrated products.

References:

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