KEM.660.237

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The pozzoolanic activity level of powder waste glass in comparisonswith other powders

Ofelia Corbu 1,3 a , Adrian M. Ioani 1,b , Mohd Mustafa Al Bakri Abdullah 2,3,c , Vasile Meiţă 4,d , Henriette Szilagyi 4,e and Andrei Victor Sandu 3,5,f

1Faculty of Civil Engineering, Technical University of Cluj-Napoca, Romania2Faculty of Engineering Technology, Universiti Malaysia Perlis (UniMAP), 01007, P.O Box 77, D/A

Pejabat Pos Besar, Kangar, Perlis, Malaysia3Center of Excellence Geopolymer & Green Technology (CEGeoGTech), School of Materials

Engineering, Universiti Malaysia Perlis, 01000 Kangar, Perlis, Malaysia4INCD URBAN-INCERC, Soseaua Pantelimon, nr. 266, 021652, Sector 2, Bucuresti, Romania

5Gheorghe Asachi Technical University of Iasi, Faculty of Materials Science and Engineering, Blvd.D. Mangeron 41, 700050, Iasi, Romania

[email protected] , [email protected], [email protected] ,[email protected], [email protected], [email protected]

Keywords: Pozoolanic activity, cementitious composites, pauder waste glass, SEM, XRF

Abstract. In order to streamline the mixes of concrete with powder waste glass as small as < 0.250mm, a postdoctoral program objective was to test the activity rate of its pozzoolanic reaction,through various methods and by comparing it with other powders reactions in a standardizedcement composition. The first method was to determine the compressive strength of cementmortars, partially substituted by glass powder, silica fume, ash and clay. The second method wasdetermining the chemical composition of the powder with fluorescence X-ray, XRF type. The thirdmethod, was based on fragments of mortar studied and subjected to microscopic observations –SEM determination (scanning electron microscopy) to investigate the microstructure of the rawmaterial.

Introduction

Based on the experience gained through the doctoral thesis [2, 3, 4], during the postdoctoralstudies, we made concrete mixtures with glass powder (FGP) [1], derived from the grinding ofwaste glass as a substitute for a portion of the amount of cement in the mixture; this way, givingconcrete double ecological role. To facilitate the decision making process while designing theconcrete recipes, in the most effective way, especially for road concrete with concrete waste and

powder from waste glass, I decided to conduct studies on the pozoolanic activity of glass powdervs. ultra fine silica (silica fume) , ashes, clay.

To define the observations on the pozoolanic reaction of the waste glass powder in the alcalinestate of fresh concrete and mortar, we performed mixtures of mortar to determine its compressivestrength [5] , in the first part of the study. We continued with microscope analysis type SEM(scanning electron microscopy) of the mortar samples, in collaboration with the University G.Asachi, SIM faculty of Iasi ; and the determination for the chemical composition of the type XRF

powders (X-ray fluorescence powder) were conducted in collaboration with the School of MaterialsEnginiering, University of Malaysia Perlis (UniMap). The first part of the study is conducted atUTC-N and INCERC by making fresh mortar compositions for determinations and subsequentlyachieving prismatic specimens with dimensions 40x40x160mm, for determining compressivestrength at ages 2, 7 and 28 days. In the compositions that have been put up for study, (10÷20)% of

the cement control sample is replaced by glass powder (PFS) or other existing dust at hand in thelaboratory, for a comparative study.

Key Engineering Materials Vol. 660 (2015) pp 237-243 Submitted: 2015-05-12© (2015) Trans Tech Publications, Switzerland Accepted: 2015-05-20doi:10.4028/www.scientific.net/KEM.660.237

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Puzzolanicity is the ability of a natural or artificial pozoolanic material (produced by industrial processes) to react with Ca (OH) 2 in the presence of water. Pozzolan reaction rate depends on theintrinsic characteristics of pozzolan, such as specific surface area, chemical composition andcontent of the active phase [6].

According to ASTM C618 prescriptions [7], pozzolanele should contain SiO 2 + Al 2O3 + Fe 2O3 ≥

Coal Fly Ash 70% to be a Class F or Class C ≥ 50%.Determination of pozoolanic activity of different materials such as fly ash, silica ultra fine slag,

kaolin, etc., is essential for their effective application in cement, concrete and mortar. It also playsan important role in the choice of the material as a stabilizer in various projects for cleaning theenvironment, such as the retention of heavy metals and waste immobilization strategies [8,9].

They are pozoolanic materials with higher or lower pozoolanic activity.Using more pozzolan as addition in cement or as a partial replacement of cement in concrete,

leads to a reduction of carbon-dioxide (CO 2).Pozoolanic reaction rate can also be controlled by external factors such as the mixture

proportions, the amount of water, or by the training space available for the development ofhydration products and reaction temperature.

Materials and Methods

Therefore, this study performs a mixture of mortar, standard recipe, used to test the compressivestrength of cement as a control mix in accordance with SR EN 196-7: 2008 [10]. The powders willreplace a quantity of (10÷20) % of the Portland cement mixtures, in this study. In a mixture, thewater – binder ratio and the conditions, strongly impact the reactivity of added pozzolan.

These pozoolanic materials, in literature, they are called cementitious constituents with bindingcharacteristics (CCBC); in the Romanian norms they are "Addition type II". When used in thecement, mortar or concrete composition, they reduce the amount of carbon (CO 2).

Materials. Pozoolanica powdered materials or cement constituents are highlighted below:Waste glass as glass poweder (GP) with particle size < 0, 250 mm, resulted from the crushing

of waste glass, mainly cobalt, of a former glass factory in Cluj. The size of this powder compositiondoes not cause unwanted reactions in the alkaline mixture of concrete or mortar [11].

2 silica fume (S1 and S2) manufactured by Elkem, acquired by BASF Romania (one beingrecently purchased and the other being stored in the laboratory since 2011), containing 100 timesfiner particles than the cement.

Ash – resulted from the technological process of the thermal depolymerization method of waste plastics and rubber, purchased from a recycling company.

Clay-based powder used as part of a doctoral thesis in the UTC-N.

Fig.1. Researched powders

There are multiple methods of determining the level of pozzolan reaction in powders, one ofwhich is determining the compressive strength. For compressive strength testing we surveyedseveral mixtures in which Portland cement (CEM I 42.5 R - Holcim Romania) is substituted withcertain quantities of cement components. The symbols assigned to the mixtures from the study are:CEM_M - Mortar mix of refference;

238 Innovative Materials and Engineering Research

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CEM_10%St 1- Mortar cement in which 10% of the cement (CEM) is substituted by silica powder(PFS)CEM_20%St 2- Mortar cementin in which 20% of the cement is substituted by silica powder (PFS)CEM_10%C 1 - Mortar cement in which 10 % is substituted by ash (C 1)CEM_20%C 2 - Mortar cement in which 20 % is substituted by ash (C 2)

CEM_10%S 1 - Mortar cement in which 10 % is substituted by silicia fume (SF)CEM_20%S 1 - Mortar cement in which 20% is substituted by the first silicia fume (SF) CEM_10%S 2 - Mortar cement in which 10% is substituted by the second silicia fume (SF)CEM_20%S 2 - Mortar cement in which 20% is substituted by the second silicia fume (SF)CEM_20%Arg - Mortar cement in which 20% is substituted by clay (Arg) powderThe produce resulted from the reaction occurring at the normal temperature in the mixture ofCement + Water = CSH (Gel) + CaOH and of CaOH + Cement constituents = CSH (Calciumsilicate hydrate)

The resulted mortar mixture keeps the same amount of binder prescribed in SR EN 196-7: 2008[10] and can be found in below table:

Table 1. Mortar compositions from the study

No.Mortar

compositions

Materials [g]

CementCEM I42,5R

Sand0/4 mm

WaterGlass

powder(GP)

AshSilicafume

(SF)/(S 1)

Silicafume

(SF)/(S 2)

Compositionbased on

Clay1. CEM_M 450+2 1350+5 225+12. CEM_10%St 1 405 1350+5 225+1 453. CEM_20%St 2 360 1350+5 225+1 904. CEM_10%C 1 405 1350+5 225+1 455. CEM_20%C 2 360 1350+5 225+1 90

6. CEM_10%S 1 405 1350+5 225+1 457. CEM_20%S 1 360 1350+5 225+1 908. CEM_10%S 2 405 1350+5 225+1 459. CEM_20%S 2 360 1350+5 225+1 9010. CEM_20%Arg 360 1350+5 225+1 90

Compresive strenght is a mecanical test used in evaluating the pozoolanic actuvity, and it’s based on a comparisons between the strenght of the reffernce mortar bars which contain onlyPortland cement as binder CEM I 42,5R ) and those containing powder (pozzolan) as a partialreplacement for the quantity of cement. Mortar bars are prepared, sampled, preserved and tested

following a detailed set of prescriptions in accordance with the standards [10,12]. Determination ofcompressive strength is generally carried out at age 2, 7, and 28 days after the preparation of themortar in the Laboratory Building Faculty of UTC-N with Advantest 9 Controls Italy press, theadvanced system of building materials for research laboratories.

A material is considered pozoolanic active when it contributes to the compressive strength [6].The pozoolanic global chemical composition is considered as one of the parameters that govern

the long-term performance as is the compressive strength.

X-ray fluorescence (XRF). The chemical composition of the researched powders wasdetermined by X-ray fluorescence (XRF), using (XRF-Qualitax, Italy), in School of MaterialsEngineering, University of Malaysia Perlis (UniMAP), Perlis, Malaysia [13].

Scanning Electronic Microscopy (SEM). Scanning electronic microscopy (SEM) was performed using SEM Tescan VEGA II LSH to investigate the microstructure and the raw material.The test was carried out using secondary as well as backscattered electron detectors.

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The mortar compositions tested are of components at the age of 28 days obtained aftercompression testing.

Result and Discussion

The compressive strength of the mortars is determined on fragments of size 40x40x160 mm,showing good form after breaking attempt, as shown below in fig. 2

a bFig. 2 Compression testing: a – Press test, b – specimens after testing

From Fig. 3. can notice that the composition of CEM_10% St 1 exceeds by 9.5% the baselineresistance to demonstrate the degree of activity of pozzolan cementitious constituents with binding

characteristics (CCBC); (CEM_10%S 1) exceeds by 48.2%, (CEM_20%S 1) by 44%, (CEM_10%S 2) by 39.6%, (CEM_20%S 2) by 36%. Other compositions do not reach the reference resistance value.

The chemical composition of powders is presented in Table 3.Because of its fine particles, large surface area, and the high SiO 2 content, silica fume (SF) is a

very reactive pozzolan when used in concrete/mortar. It is active, according to a minimum contentof 85% SiO 2 [14]. Except for ashes, all powders have a quantitatively favorable chemicalcomposition for pozzolanic activity.

Fig. 3. Graphical representation for compressive strength of mixtures of study


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Table 3. XRF Analysis Result- Chemical composition

ChemicalCompound

Sample

S1 S2 CEM GP ARG (clay) C (ash)SiO 2 98.35 98.03 14.3 77.7 69.9 15.7K 2O 0.874 1.03 1.08 1.01 4.1 0.54

CaO 0.334 0.376 71.46 13.6 5.77 6.57MnO 0.031 0.029 0.042 0.0098 0.072 0.044Fe 2SiO 3 0.168 0.233 3.79 0.441 3.75 5.11CuO 0.03 0.029 0.036 0.035 0.037 0.28ZnO 0.0457 0.132 0.13 - 0.004 35.76As 2O3 0.0041 0.0051 - 0.488 0.0087 -Rb 2O 0.0056 0.0048 - - 0.024 -SrO 0.006 0.0071 0.091 0.021 0.032 -RuO 2 0.126 0.11 0.17 0.27 0.297 -Re 2O7 0.015 - 0.02 - 0.01 -PbO 0.0075 0.006 - 0.259 - -Br - 0.0045 - 0.59 - 1.04

MgO - - 0.86 0.01 - -ZrO 2 - - 0.016 0.167 0.146 -Eu 2O3 - - 0.084 - 0.1 -Al 2O 3 - - 2.9 0.06 14.2 6SO 3 - - 4.68 - - -

Na 2O - - 5.7 5.27 - -TiO 2 - - 0.28 0.12 1.41 0.51Co 3O4 - - - 0.201 - 0.02V2O5 - - - - 0.035 -Cr 2O3 - - - - 0.022 0.061SO 3 - - - - - 23.5Cl - - - - - 5.05

In figure 4 we have the SEM microstructure of the mixes made on break, where we can see thecompactity and the aggregates. .

Discussion

Glass powder (GP) is on the 2 nd place when considering the contained amount of SiO 2. Doing a parallel of the silicon oxide content (SiO 2) with the compressive strength test results we confirm theleading position of silica fume (SF), followed by glass powder (GP), as level of pozoolanic activity,

both improving compressive strength. Of all the mortar mixtures, only the silica fume (SF) andglass powder, manage to reach and respectively exceed the reference resistance obtained by themixture of reference.

Because silica fume is amorphous, it didn’t mattered that one of the two sources was for a long period of time, they became active in the presence of cement and water, the compressive strengthvalues for these mortars showing similar results.

Ash has basic components which can attribute pozoolanic activity, but it does not correspondquantitatively. Waste ash from this source can be used as fine part input (addition not substitute) ina composite for constructions, increasing the capacity and all derivative features.

Clay-based powder in an amount of less than 20% cement replacement, would show a bettercontribution to the compressive strength, proving its pozoolanic quality in the alkaline environmentof mortars and concretes.


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Fig. 4. SEM Microstructures of the mixes: a - CEM_M; b - CEM_10%St 1; c - CEM_20%St 2;d - CEM_10%C 1; e - CEM_20%C 2; f - CEM_20%Arg; g - CEM_10%S 1; h - CEM_20%S 1;

i - CEM_10%S 2; j - CEM_20%S 2

Conclusions

Through these three methods we can confirm the degree of pozzoolanic activity for powdermixtures.

Glass powder (FGP) assures the increased resistance for an amount of 10% replacement of

cement, and for 20% the result is really close to the resistance of the reference mixture.Compressive strength is an important parameter when measuring the pozzoolanic characteristic

of a powder. Any powder which is to be incorporated into a composite should have themineralogical and chemical composition tested, since it’s different from a source to another.


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The research demonstrates the very good opportunity provided by the use of glass powder (GP) in composition with the cement. This way, the stored waste glass can be used as raw material,saving valuable non-renewable natural resources and protecting the environment.

Acknowledgements

This paper was supported by the Post-Doctoral Program POSDRU/159/1.5/S/137516, project co-funded from European Social Fund through the Human Resources Sectorial Operational Program2007-2013.

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[2] O. Corbu, D. Moldovan, H. Szilágyi, M. Pop “Facing crisis: a glass by-products solution”,Proceedings of the the 8th Central European Congress on Concrete Engineering CCC 2012”Durability of Concrete Structures”, 4 - 6 Oct. 2012, Plitvice Lakes, Croatia, ISBN 978-953-

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[6] *** http://en.wikipedia.org/wiki/Pozzolanic_activity[7] ASTM C618, Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan

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