Flyash Additive

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Int. J. Mech. Eng. & Rob. Res. 2014 Karthikeyan N et al., 2014

ISSN 2278 0149 www.ijmerr.comVol. 3, No. 2, April, 2014

2014 IJMERR. All Rights Reserved

Research Paper

EFFECTS ON SETTING, STRENGTH AND WATERRESISTANCE OF SOREL CEMENT ON MIXING FLY

ASH AS AN ADDITIVE

Karthikeyan N1*, Sathishkumar A2 and Dennis Joseph Raj W2

*Corresponding Author: Karthikeyan N, [email protected]

Magnesium oxychloride cement (MOC, Magnesia / Sorel's Cement), discovered by Sorel S.T.in 1867 and has versatile cementing characteristics. It is prepared by the reaction of magnesiumchloride with magnesia in aqueous solution. Various fillers are used as to improve the settingtime, compressive strength, water tightness of oxychloride cement. Additives play an importantrole to modify the properties of Sorel's cement. In this work we have used fly ash along withmagnesium oxychloride (MOC) cement, an energy efficient and environmentally friendlycementitous material which can be used for civil, structural and industrial applications. We havefound that the compressive strength of Sorel's cement increases with the increase in quantitiesof the additive (20%, 40%,60%). It is also found that the incorporation of fly ash improves thewater resistance, decreases the workability or fluidity, retard the setting time of the final cement.

Keywords: Compressive strength, Fly ash, Magnesium oxychloride cement, Setting time, Water resistance

1 Asst.Professor, Department of Mechanical Engineering, K.Ramakrishnan College of Engineering, Trichy2 UG Scholar, Department of Mechanical Engineering, K.Ramakrishnan College of Engineering, Trichy

INTRODUCTION

Magnesium oxychloride (MOC) cement wasdeveloped shortly after the invention ofPortland cement, as a magnesia-basedcementing material that sets in air curingwhen compared to portland cement whichrequires water for curing (Brady G S,2002and Sorel S T). With a through solutionreaction at ambient temperature, the MOCsystem is a typical ternary system withmagnesium oxide, magnesium chloride andwater the three major reaction components.

The two main chemical composition phasesproduced in the ternary system are3Mg(OH)2. MgCl2. 8H2O (phase 3) and5Mg(OH)2. MgCl2. 8H2O (phase 5). The wellcrystallized needle-like structure of phase 5of chemically bonded MOC has beendescribed as scroll-tubular whiskers. Themechanical interlocking and unique fibrousmicrostructure resulting from the intergrowthof the crystals is a major source for thestrength development of MOC cement.Therefore, the physical properties of MOC



cement depend largely on the phasesformation and subsequently on theappropriate proportions of the startingmaterials.

It is well known that MOC cement hasmany properties superior to the ordinaryPortland cement (Y Karimi & A Monshi, 2012;Z Juhasz, 1977). Because of its elastic andacoustic properties, and attractive marble-likeappearance which comes from the use ofdifferent fillers, MOC cement is used forrendering wall insulation panels, interiorplasters and exterior stuccos, and decorativepanels. Some other commercial andindustrial applications of MOC cement areindustrial flooring, fire protection, grindingwheels and light weight concrete. Theexcellent performance of MOC cementincluding rapid setting and hardening, goodresistance to abrasion and chemicals, as wellas remarkable bonding ability to largeamounts of different inert fillers makes it anattractive candidate of binding materials forrepair mortar.

Moreover, MOC cement draws muchresearch interests recently due to the energysaving consideration as it can be used as aPortland cement replacement on manyoccasions. The production of light burnt MgOused in MOC requires a much lowercalcinations temperature compared to that forPortland cement, thus reducing vast amountof energy consumption and favorite for thesustainable development of the buildingindustry. Besides, generated during thecombustion of coal for energy production, flyash is one of the major industrial by-productsand being utilized in the construction industryfor decades. By incorporation of fly ash intoMOC cement, an energy saving andenvironmentally friendly construction materialcan be formed for industrial applications[5].In addition, water resistance of MOC system

is a key issue in the research before MOCrelated products could be utilized in theindustry. To that end, the effects of the fly ashon MOC cement including flow property,setting time, strength development, waterresistance have been investigated.

RAW MATERIALS

A. Magnesium oxide

Magnesium oxide is used in this study wasobtained from TANMAG, Salem that wasproduced by the calcination of magnesiumcarbonate . It is produced by sintering rawmagnesite shaft kiln at a controlledtemperature around 1000 C by using furnaceoil. The chemical analysis of the magnesiumoxide is given below.

Ingredients Percentage (%)Magnesium Oxide 87

Calcium Oxide 1.5Ferric oxide 0.2

Silica 8.5Alumina 0.25

Loss on Ignition 2.5

Table 1: Chemical Composition of theMagnesium Oxide

B. Magnesium Chloride

Magnesium chloride is the name for thechemical compounds with the formulasMgCl2 and its various hydrates MgCl2(H2O)x. These salts are typical ionic halides,being highly soluble in water. The hydratedmagnesium chloride can be extracted frombrine or sea water. Mixed with hydratedmagnesium oxide, magnesium chloride formshard material called Sorel cement.

C. Fly Ash

Fly ash, also known as flue-ash, is one ofthe residues generated in combustion, andcomprises the fine particles that rise with the



flue gases. In an industrial context, fly ashusually refers to ash produced duringcombustion of coal. Fly ash is generallycaptured by electrostatic precipitators or otherparticle filtration equipment before the fluegases reach the chimneys of coal-fired powerplants, and together with bottom ash removedfrom the bottom of the furnace is in this casejointly known as coal ash.

Two classes of fly ash are defined byASTM C618: Class F fly ash and Class C flyash. The chief difference between theseclasses is the amount of calcium, silica,alumina, and iron content in the ash. Thechemical properties of the fly ash are largelyinfluenced by the chemical content of the coalburned (i.e., anthracite, bituminous, andlignite). (Ying Li et al. 2013).

1. Class F fly ash

The burning of harder, older anthracite andbituminous coal typically produces Class Ffly ash. This fly ash is pozzolanic in nature,and contains less than 5% lime (CaO).Possessing pozzolanic properties, the glassysilica and alumina of Class F fly ash requiresa cementing agent, such as Portland cement,quicklime, or hydrated lime, with the presenceof water in order to react and producecementitious compounds.

Property ASTM C618 Requirements%SiO2 + Al2O3 + 70Fe2O3, min

SO3, max 5Moisture content, max 3

Loss on Ignition, max 6

Table 2: Class F Fly Ash ChemicalComposition

2. Class C fly ash

Class C fly ash is produced from the burningof lignite or sub bituminous coal. In addition

to having pozzolanic properties, it also hassome self-cementing properties. In thepresence of water, Class C fly ash will hardenand gain strength over time. Class C fly ashgenerally contains more than 20% lime(CaO). Unlike Class F, self-cementing ClassC fly ash does not require an activator. Alkaliand sulfate (SO4) contents are generallyhigher in Class C fly ashes.

Property Requirements (ASTMC618), %SiO2 + Al2O3 + 50Fe2O3, min

SO3, max 5Moisture content, max 3

Loss on Ignition, max 6

Table 3: Class C Fly Ash ChemicalComposition

EXPERIMENTAL PROCEDURE

Magnesium oxychloride cement is preparedby mixing the raw materials, magnesia (MgO)of Salem origin, Magnesium chloride and FlyAsh (as an inert filler). To study the effects ofadmixing fly ash as an additive, following testshave been carried out by taking fly ash indifferent proportions in the dry mix on someproperties of magnesium Oxychloridecement. All experiments were carried outaccording to IS specifications (IndianStandard et al. (1982; 1977; 1760; 1982).

SAMPLE MgO MgCl2 Fly ashNAME

F1 40% 40% 20%(class F)

F2 30% 30% 40%(class F)

F3 20% 20% 60%(class F)

C1 40% 40% 20%(class C)

C2 30% 30% 40%(class C)

C3 20% 20% 60%(class C)

Table 4: List of Proportion (by Weight %)



In order to study the effect of fly ash onthe strength and water resistance 70 mm X70 mm cubes were casted by mixingpreweighed amount of magnesium chloridein water and this solution was mixed withpreweighed amount of magnesia and fly ash.This dry powder was mixed with solution forabout 3 minutes until a smooth pourableslurry was formed and poured into cubes formeasuring the compressive strength andwater resistance. Nine cubes were casted foreach composition. The cubes were taken outand kept at room temperature for furthercuring. After one week of air curing one cubein each composition was taken and weighedand immersed in preweighed amount ofwater. The results of compressive strength,setting time and water resistance arediscussed below.

RESULTS AND DISCUSSION

A. Compressive Strength

From the table it can be seen that thecompressive strength increases steadily withage which is typical with all the cementitousmaterials. It can also noted that the strengthincreases as the fly ash loading increaseswhich is a very good from the sustainabilitypoint of view because one will be able to usemore amount of fly ash which will beotherwise land filled. From the table it can beseen that the loading of fly ash can be ashigh as 60% and still attains strength of 43Mpa which is not at all possible with Portlandcement. The industry practice has been 25%loading of fly ash in Portland cement. Thestrength development of the Oxychloridecement remains independent on the type offly ash used as filler.

Table 5: Effect of Fly Ash on CompressiveStrength of Oxycholride Cement

Compression Strength N/mm2

Class F 1st day 3rd day 27th dayF1 11.19 15.44 18.63

F2 21.73 26.59 30.09

F3 27.82 34.19 42.38

Chart 1: Comparison of Fly Ash onCompressive Strength

Table 6: Effect of Fly Ash onCompressive Strength of Oxycholride

Compression Strength N/mm2

Class F 1st day 3rd day 27th day

C1 12.75 17.12 17.62

C2 22.66 29.58 33.40

C3 28.38 36.11 45.99

Chart 2: Comparison of Fly Ash onCompressive Strength



B. Setting Time

The effect of fly ash on setting characteristicsof magnesium oxychloride cement wasstudied by admixing the additive in the drymix in varying proportions. The dry mix wasmixed with predetermined amount of wateruntil a smooth slurry is formed and tested forInitial and Final setting time. From the tableit can be seen that the setting time increaseswith increasing amount of fly ash. The initialand final setting time can be controlled byusing various proportions of fly ash

Table 7: Effect of Fly Ash on SettingTime of Oxycholride Cement

Setting Time Initial (min) Final (min)F1 120 320

F2 130 360

F3 150 400

C1 115 310

C2 120 355

C3 140 405

C. Water Resistance

The result of the water soaking tests asplotted in chart 3 exhibits that the waterresistance of the MOC would be dramaticallyboosted when appropriate amount of fly ashis utilized. From the table it can be seen thatfor class F samples the weight of the cubeincreases initially and then decreases, but forclass C1 sample the weight goes onincreasing. The sample C2 broke due toexpansion. This shows that there is a clearinteraction between the binding phase ofcement and oxides in fly ash which needs tobe analysed further.

Table 8: Effect of Fly Ash on WaterResistance of Oxycholride Cement

Water resistance (grams)Proportion Initial 1st Day 3rd Day 7th Day

F1 566.5 609.5 608.5 607.5

F2 620.5 650.0 649.0 648.5

F3 634.0 675.0 678.0 685.0

C1 647.0 693.5 695.0 697.0

C2 630.0 675.5 678.5 678.0

C3 678.5 731.5 736.0 749.0

Chart 3: Comparison of Fly Ash onWater Resistance

CONCLUSION

The influences of class C and class F fly ashon the properties of MOC cement areinvestigated in this study. By incorporatingfly ash up to 60% by weight, the workabilityor fluidity is enhanced, the setting timeretarded, and more importantly the waterresistance improved and the compressivestrength is increased. The improvement ofwater resistance of the MOC incorporatedwith a fly ash may be attributed to theinteraction between the binding phases ofcement and the oxides in the fly ash whichneeds to be analysed further.



REFERENCES

1. Brady G S and Mc Graw Hill (2002),Materials Hand Book, Fifteenth Edition,17.

2. Influence of Inert Filler on CementingProperties of Magnesium OxychlorideCement Moc with MOC-Friendly Cement,R N Yadav, Upendra Singh, PriyankaGupta, Madhu Sharma, Indian journal ofapplied research, Vol. 3, No. 10.

3. Indian Standard: 1982, 6574. Indian Standard: 1977, 2730.5. Indian Standard: 1962, 1760.6. Indian Standard: 1982, 10132.

7. Sorel S T, C R Acad Sci (1867), Paris,65, 102.

8. Y Karimi & A Monshi (2012).Investigation on the mechanical andhydration properties of Sorel cement bychanging the concentration ofmagnesium chloride.

9. Ying Li a,c, Hongfa Yu , Lina Zheng, JingWen, Chengyou Wu, Yongshan T (2013),Compressive strength of fly ashmagnesium oxychloride cementcontaining granite wastes, Constructionand Building Materials No. 38 pp. 1-7.

10. Z Juhasz (1977). Bonding mechanismof Sorel cement and mechanicalactivation of MgO.

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