Scholarly article on topic 'Investigation of the Natural Pozzolans for Usage in Cement Industry'

Investigation of the Natural Pozzolans for Usage in Cement Industry Academic research paper on "Materials engineering"

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Abstract of research paper on Materials engineering, author of scientific article — Nicoleta Cobîrzan, Anca-Andreea Balog, Emilia Moşonyi

Abstract One of the most important aspect of selecting the proper natural pozzolanic material as admixture of Portland cement in concrete or mortars is the chemical reactivity and mineralogical content. If the chemical reactivity index and quartz content are high the pozzolans can substitute the cement from the binder groundmass in a greater proportion. The paper present mineralogical, petrographical, chemical and mechanical properties of few natural pozzolans (tuffs and perlite) in order to determine if they are proper for usage in cement industry manufacturing.

Academic research paper on topic "Investigation of the Natural Pozzolans for Usage in Cement Industry"

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Technology

Procedia Technology 19 (2015) 506 - 511 ^^^^^^^^^^^^^^

8th International Conference Interdisciplinarity in Engineering, INTER-ENG 2014,9-10 October

2014, Tirgu-Mures, Romania

Investigation of the natural pozzolans for usage in cement industry

Nicoleta Cobirzana'*, Anca-Andreea Baloga, Emilia Mosonyib

aTechnical University of Cluj-Napoca, 28 Memorandumului Street, 400114, Cluj-Napoca, Romania bBabes Bolyai University of Cluj-Napoca, 1 Kogalniceanu Street, 400084, Cluj-Napoca, Romania

Abstract

One of the most important aspect of selecting the proper natural pozzolanic material as admixture of Portland cement in concrete or mortars is the chemical reactivity and mineralogical content. If the chemical reactivity index and quartz content are high the pozzolans can substitute the cement from the binder groundmass in a greater proportion. The paper present mineralogical, petrographical, chemical and mechanical properties of few natural pozzolans (tuffs and perlite) in order to determine if they are proper for usage in cement industry manufacturing.

© 2015 The Authors.PublishedbyElsevierLtd.This is an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of "Petru Maior" University of Tirgu Mures, Faculty of Engineering

Keywords: local resources; petrographic; pozzolanic index; manufacturing; thin section.

1. Introduction

It is well know that building material industry consume a large amount of natural resources and generates waste and greenhouse gas emissions into the atmosphere during the manufacturing process. Cement Portland is one of the most widely used building materials in the world, whose manufacturing process is consisting in extracting the raw materials (limestone and clay) burning them at a high temperature, mixing then with gypsum in order to form a fine powder.

Researches regarding the conservation of natural resources and environmental protection are focused in the last years on finding new materials, durable, environmentally friendly and sustainable with low embodied energy, high quality and low manufacturing cost which can be used to substitute in some percent the cement Portland [1-6].

* Corresponding author. Tel.: +40-264-401533. E-mail address: nicoleta.cobarzan@cif.utcluj.ro.

2212-0173 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of "Petru Maior" University of Tirgu Mures, Faculty of Engineering doi: 10. 1016/j .protcy.2015.02.072

Natural pozzolanic materials are a siliceous or siliceous/aluminous material which, need to be mixed with lime/cement and water, to form cementations compounds.Using natural pozzolanic materials (volcanic tuff, perlite, pumice) as partially substitutes of Portland cement in building materials may lead to saving energy to lower cost. Extracting process of the natural pozzolan from the quarry is similar to extract the limestone (necessary for cement manufacturing), but needs to be grinded without burning, reducing in this way the impact upon the environment [2].

In order to determine the pozzolanic characteristics of few natural pozzolanic materials have been collected samples of perlite from Orasu Nou (sample SI) and volcanic tuffs from Tiocu (sample S2) and Macicas (sample S3).

2. Materials and Methods

The rocks (samples SI, S2, S3), cement paste (sample Bl) and cement and natural pozzolanic paste (samples B2, B3, B4) made of perlite and tuff in 25% percent, were analyzed from mineralogical-petrographic, chemical and mechanical point of view. The mineralogical content, the transformations and alteration processes were examined under polarized microscope in thin sections prepared according to STAS 6200/3-81 [7].

The chemical composition was expressed as oxides according to SR 3832-1 [8] and the reactive silica content was determined on powder of 0.063 mm grain size and expressed as pozzolanic index, determined considering the requirements imposed by SR 3832-8 [9].

3. Results and discussion

Mineralogical contents of the natural pozzolans shows that: • Sample SI contains altered volcanic glass (chloritised, sericitised, zeolitised) of 85% in rock volume, locally appear devitrified spheruliths composed by calcedonite rosettes (of 10-300 microns size) and microlites of iron, bearing opaque minerals, biotite and feldspars (up to 50 microns size) with perlitic conchoidal microfissures (see Fig. la,b).

Fig. 1. Thin section of Sample SI. (a) crystalocllasts of biotite (left side-black); (b) small orientated crystals, volcanic glass

groundmass, conchoidal fissures.

• Sample S2 has a relative fine grained texture with greyish white or greenish color (mainly due to celadonitic mica content), with crystalloclasts of maximum 500 microns size (quartz, feldspar, biotite and finely dispersed iron-bearing opaque minerals) about 60% of rock volume, lithoclasts (gneiss, carbonate sandstone, foraminifera bioclast) 40% of rock volume, a porous groundmass zeolitised and carbonated, with chloritised, sericitised volcanic hyaloclasts (palagonitic glass) (see Fig. 2.). The pores have about 200 microns channel shapes, containing secondary carbonate infillings.

Fig. 2. Thin section of Sample S2. (a) N+; (b) IN - carbonatation, zeolitization, void with carbonate and feldspar, quartz, biotite clasts, crystalloclasts (quartz, feldspar), hyaloclasts and bioclasts.

• Sample S3 is a rio-dacitic tuff, a fine grained rock with white- yellowish color. The petrographical content is: crystalloclasts (under 500 microns grain size) of quartz about 60% rock volume, zeolitised plagioclases, chloritised biotite and a very fine opaque minerals, lithoclasts (volcanoclastic and/ or fine epiclastites) 20% and a porous groundmass of volcanic zeolitised hyaloclasts (palagonite). The pores are partially infilled by devitrified silica as microcrystalline calcedonite rosettes (see Fig. 3.). The carbonate and biotite content are higher than in the previously samples presented.

Fig. 3. Thin section of Sample S3, (a-b) lithoclasts, crystalloclasts of zeolitised feldspars, and hyalloclast, plagioclases

crystalloclasts.

The pozzolanic activity of the natural pozzolans depends on the chemical composition, chemical reactivity index and mineralogical compounds.

From chemical analysis (Table 1.) it result that analyzed samples have a content of silicon dioxide (Si02), aluminium oxide (A1203), iron oxide (Fe203) above 70% and sulfur trioxide (S03) max 5% that satisfies the ASTM C618 [10] requirements imposed for pozzolanic materials which are used in concrete manufacturing.

Due to high volcanic glass content all samples have a relative high chemical pozzolanic index (Table 1). The chemical reactivity index of the sample SI is not greater than 5,5%, while the sample S2 and S3 have the chemical reactivity index 52,5%, respectively 67%.

Table 1. Chemical analysis of samples

Oxides ai2o3 BaO CaO Cr203 Fe203 k2o MgO MnO Na20 P2O5 S03 Si02 SrO Ti02 M*

Sample 20.4 0.05 8.01 0.01 6.13 1.66 0.53 0.11 7.03 0.12 0.04 49.6 0.14 0.29 76.13

Sample 13.45 0.06 3.17 0.01 9.85 5.51 0.26 0.76 8.45 0.04 0.15 52.3 0.59 0.49 75.6

Sample 12.35 0.04 3.98 0.01 1.04 1.72 0.87 0.01 0.68 0.01 0.01 68.4 0.06 0.17 81.75

M= A1203 + Fe203 + Si02

The compressive strengths of binder paste at 28 days are the following: 35.2N/mm2 for sample B1 (cement); 15.36N/mm2 for sample B2 (cement and perlite); 25.36N/mm2 in case sample B3 (cement and volcanic tuff from Tiocu) and 26.78N/mm2 for sample B4 (cement and volcanic tuff from Macicas).

The pétrographie microscopic investigations put into the evidence the differences between the mineralogical compositions of the samples, considering reaction rims created by amorphous calcium silicate hydrated, calcium hydroxide crystalized around quartz grains and calcium aluminates hydrates around Feldspar grains from pozzolans and the path of the fissures developed during the compressive test (Fig. 4-6).

In the binder stereoscopical and microscopical images (Fig. 4-6) it can be observed: • that sample B1 has a fine, homogeneous grainsize mass, with thicker reaction rims around the small crystalls of the cement groundmass (Fig. 4a,b).

Vfip* SJ

Fig.4. Sample Bl. (a) - Fine grained, homogenous groundmass (image wide 2,5mm); (b)- Thin section (N+) -relative homogeneous distribution of fine grained crystalline phases.

• in binder based on perlite (sample B2) the pozzolanic reaction rims around the grains of volcanic glass is colloidal with different mechanical properties than that of volcanic glass, consequently the sample has a brittle behavior and fissure path is developed between the grains surface and it's reaction rims (Fig. 5a). Using the perlite as admixture in the mass of the binder, will result a relatively homogeneous groundmass and the colloidal reaction rims made of amorphous calcium silicate hydrated with few crystallized grains appeared around volcanic glass due to lower pozzolanic reaction (the chemical reactivity index is less than 5%) (Fig. 5b, c, d).

Fig. 5. Sample B2. (a) fissure path between the volcanic glass grains and colloidal rim(image wide 2,5mm); (b) thin section (IN): volcanic glass grains with a mainly colloidal rim in the binder matrix; (c)- thin section (N+) few crystallized grains around volcanic glass resulted during the pozzolanic reaction; (d) thin section (IN).

• the samples B3 and B4 have both the pozzolanic index greater than 70%, and chemical reactivity index greater than 50%; the reaction rims is thicker developed especially at the surface of the quartz, zeolitized feldspar or biotite grains. (Fig.6-7). The fissure path is developed between the outer boundary rims and groundmass, due to ion exchange between the minerals grains and the cement compounds.

Fig. 6. Sample B3. (a) thin films of matter around mineral grains in binder (image wide 2,5mm); (b) thin section: feldspar and zeolitized amphibole grains with a mainly crystallized (anisotropic) colloidal rim and binder matrix. N+

(a) (b)

Fig. 7. Sample B4. (a) feldspar, quartz and carbonate grains with reaction rim (image wide 2,5mm); (b) thin section (N+)- crystallized reaction rim around the quartz, feldspar carbonate grains and in the binder matrix.

4. Conclusions

The samples analyzed in the paper shows that content of silica and pozzolanicity index are high but content of reactive silica is very different (high for tuffs samples and low for perlite).

The chemical reactivity of the samples is influenced not only from the reactive silica content but even from the grains type (quartz, feldspar, volcanic glass) and specific surface area. The perlite has a high content of volcanic glass but low reactivity with the cement mineralogical compound. This can be improved by using a very fine grain size to assure a high specific surface area and additives such as HF which can dissolve the reactive silica from volcanic glass and increase the reactivity silica index. The tuff samples having a high content of reactive silica show a high pozzolanic reaction with the cement and a large reaction rims around the quartz grains. Different mechanical characteristics of the binder (higher in case of volcanic tuffs and lower in case of perlite) can be due to different thickness of reaction rims around the grains.

Considering the characteristics of the analyzed samples, it results that all of them can be used in cement industry to produce new building materials but in different dosage depending on the domain of utilization.

References

[1] Alp i, Deveci H, Sungun YH, Yilmaz AO, Kesimal A, Yilmaz E. Characteristics of a natural raw material for use in Blended Cements, Iranian Journal Of Science & Technology, Transaction B, Engineering, Vol. 33, No. B4, Pp 291-300, 2009.

[2] Balog AA, Cobirzan N, Aciu C, Ilu^iu - Varvara DA. Valorification of volcanic tuff in constructions and materials manufacturing industry, Procedia Technology 12 (2014) 323 -328, doi: 10.1016/j.protcy.2013.12.493

[3] Kannikar J, Supapan S. Effects of Zeolite A on the Microstrncture and Strength Development of Blended Cement, Journal of the Microscopy Society of Thailand 24 (2), 94-98 (2010).

[4] Mertens G, Snellings R, Van Balen K, Bicer-Simsir B, Verlooy P, Elsen J. Pozzolanic reactions of common natural zeolites with lime and parameters affecting their reactivity, Cement and Concrete Research 39 (2009) 233-240.

[5] Skripkiunas G, Sasnauskas V, Dauksys M, Palubinskaite D. Peculiarities of hydration of cement paste with addition of hydrosodalite, Materials Science-Poland, Vol. 25, No. 3, 2007.

[6] Yoleva A, Djambazov S, Chernev G. Influence Of The Puzzolanic Additives Trass And Zeolite On Cement Properties, Journal of the University of Chemical Technology and Metallurgy, 46, 3, 2011, 261-266.

[7] STAS 6200/3-81. Piatra naturala pentru constructs. Luarea probelor confectionarea sectiunilor subtiri si a epuvetelor (Natural stones for building. Sampling, preparation of thin sections and test pieces).

[8] SR3832-1-Materiale puzzolanice naturale si artificial. Indicatii generale pentru efectuarea analizei chimice. (Natural and artificial pozzolanic materials. General indications for chemical analysis.)

[9] SR 3832-8- Materiale puzzolanice natural si artificial. Determinarea indicelui de activitate puzzolanica si a dioxidului de siliciu reactiv. (Natural and artificial pozzolanic materials. Determination of pozzolanic activity indication and of reactive silicon dioxide).

[10] ASTM C618 - 12aStandard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete