Scholarly article on topic 'Sustainable Uses of Zeolitic Tuff as Building Materials'

Sustainable Uses of Zeolitic Tuff as Building Materials Academic research paper on "Materials engineering"

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Academic journal
Procedia Technology
OECD Field of science
{sustainability / "local resources" / compatibility / "microscopic analysis" / "X-ray diffraction"}

Abstract of research paper on Materials engineering, author of scientific article — Nicoleta Cobîrzan, Anca-Andreea Balog, Claudiu Aciu, Dana Adriana Iluţiu–Varvara

Abstract Sustainable building materials are of top quality from technical point of view, with a long lifetime and a low cost of maintenance and exploitation. To ensure the sustainability of a building one of the essential condition is to use local materials with reduced embodied energy, low cost and good appearance. In case of new buildings masonry works can be durable and sustainable in the same time if all the materials (units and mortars) used to realise them have the similar characteristics (mineralogical composition, texture, structure, physical and mechanical properties). The study was performed considering tuffs as masonry units, mortar based on these tuffs (both in substitution of cement and sand), and classical mortar as joining together in order to realise a homogeneous structure.

Academic research paper on topic "Sustainable Uses of Zeolitic Tuff as Building Materials"

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Procedia Technology 12 (2014) 542 - 547

The 7th International Conference Interdisciplinarity in Engineering (INTER-ENG 2013)

Sustainable uses of zeolitic tuff as building materials

Nicoleta Cobirzana'*9 Anca-Andreea Baloga9 Claudiu Aciua, Dana Adriana Hutiu-Varvaraa

aTechnical University of Cluj-Napoca, 28 Memorandumului Street, 400114, Cluj-Napoca, Romania


Sustainable building materials are of top quality from technical point of view, with a long lifetime and a low cost of maintenance and exploitation. To ensure the sustainability of a building one of the essential condition is to use local materials with reduced embodied energy, low cost and good appearance. In case of new buildings masonry works can be durable and sustainable in the same time if all the materials (units and mortars) used to realise them have the similar characteristics (mineralogical composition, texture, structure, physical and mechanical properties). The study was performed considering tuffs as masonry units, mortar based on these tuffs (both in substitution of cement and sand), and classical mortar as joining together in order to realise a homogeneous structure.


Selectionandpeer-reviewunderresponsibilityofthePetru Maior University of Tirgu Mures.

Keywords: sustainability; local resources; compatibility; microscopic analysis; X-ray diffraction.

1. Introduction

Concerns for sustainable development came into focus of the scientific community since the '70s and it is considered to be the only one viable solution for civilization, not to destroy itself. According to Agenda 21: "the

complex problem of construction and the environment, efforts towards sustainable construction are fundamentally an attempt to put in place practices that restore the balance between the natural and built environments." [I]

* Corresponding author. Tel.: +40 264401533 E-mail address:

2212-0173 © 2013 The Authors. Published by Elsevier Ltd.

Selection and peer-review under responsibility of the Petru Maior University of Tirgu Mures. doi:10.1016/j.protcy.2013.12.527

Considering sustainability principles, the building material, structural and non-structural element or an entire construction must be designed in order to resist to mechanical, chemical and physical damages, and not affecting air, water and soil quality during entire lifecycle.

In the present building materials industry is one of the largest consumers of energy which also contributes to environmental pollution. The widespread use of Portland cement shows a large disadvantage from energetically point of view, being necessary to consume a high quantity of conventional energy (fossil fuel).

Another problem is concerning the gravel extracted from riverbeds, which are limited sources of aggregates. Their exploitation can lead to ecological imbalances by changing routes and rates of groundwater flow and can lead to depletion of local resources.

The need to find substituent's for both cements and aggregates in manufacturing the building materials, became today a stringent problem for entire scientific communities. Waste resulted from construction or natural and artificial pozzolan materials (volcanic ash, volcanic tuff, burned clay, silica fume) are used as admixture in new building materials (mortar or concrete) [2, 3].

2. Material and Method

The complex state of stresses in masonry works subjected to centric or eccentric compression appears as a consequence of: the differences in the deformability of the masonry units (tuff stone or bricks) and/or mortar, the unevenness of the mortar joints and masonry units, different values of thermal expansion coefficients etc [4].

In time, during restorations of exiting building appeared a lot of problems concerning the incompatibility between the old and new building materials, accelerating degradations during time [5]. Logan Strenchockin 2009 said that: "in cases where Portland cement based mortars were used with softer units, such as sandstone and primitive bricks, serious problems often resulted "[6].

The compatibility between buildings materials associated to old or new masonry works is considered if they have the similar characteristic from all chemical, mechanical, technological, physical (water absorptions, porosity level, permeability) and esthetical (texture, color) points of view [5, 7, 8].

Considering these aspects, it were prepared and investigated new mortar recipes, using volcanic tuff (recipe R2 using the tuff as substitute of the cement (50%) and the recipe R3 as substitute of the aggregate (100%)), and their properties were compared with those of a classic mortar (R1 sample).

Physical-mechanical properties (bulk density, average bulk density, compressive strength, bending strength, fire resistance, water absorption by capillarity, apparent porosity) were investigated in each sample (both tuffs as masonry units and the mortar) using standardized specimens.

3. Results and Discussions

Bending and compressive strength of the mortars samples were analyzed at 28 days (Table 1). The brand of the material is indicated by the compressive strength value obtained in the prism halves, according to SR EN 101511/2002 [9].

Table 1 Physical-mechanical properties of mortars samples

Recipe Apparent density [kg/m3] Bending strength fti [N/mm2] Compressive strength fm [N/mm2] Mortar class

R1 2278 6.74 36.38 M 30

R2 2146 4.21 15.29 M 15

R3 1766 2.81 10.56 M 10

The fire resistance of mortars is high because of the absence of organic waste and the high content of zeolites. Water absorption by capillarity of mortars was determined according to EN 1015-18/2003 [10] on prismatic specimens of 4x4x16 cm. The values are presented in Table 2.

Table 2. Mortar classes according to water absorption

Recipe Volume Absorption coefficient Class

[cm3] [kg/(m2-min0.5)]

R1 64 0.08 W2

R2 64 0.75 WO

R3 64 0.69 WO

The mechanical properties of the tuffs sample (as rock) were performed for compression having the size 50x50x50 mm; the results range between 15.29 and 18.38 N/mm 2

Mineralogical composition of volcanic tuff (rock) and mortars were analysed microscopically in thin and polished sections, and X-ray diffraction (made on powders of the samples studied) (Fig. l-(a),(b),(c),(d)).

In order to determine the mineralogical composition of mortars, a few grams of the sample were taken and semi-quantitatively analyzed by X-ray diffraction using a diffractometer with Co-Ka radiation anticathode, X = 1.790300 Â and 20e/mm from 100 to 70° (2theta).

Qz= Quartz (70,6%) Ca=Calcite (1,3%) Chl= Chlorite (4,7%) Bi= Biotite (9.3%) Fp= Feldspar (14.1%)

o Qz= Quartz (81,8%)

Fp= Feldspar (15,3%)

Ca= Calcite (2,9%)

c ..J N O O N N o ..............Ç I it J? o? 5Ç I.....


= Quartz (21,1%) = Calcite (7,2%) Clinoptilolite (15,9%) Heulandite (48,7%) = Kaolinite (1,9%) i= Feldspar (5,2%)

Co-Ka (1.790300 A)

Co-Ka (1.790300 A)

Fig. 1. X-ray analysis (a)-sample Rl- classic mortar; (b)- sample R2- mortar with tuff as substitute of cement; (c)- sample R3- mortar mortar with

tuff as substitute of aggregate; (d)- tuff sample

Semi-quantitative X-ray analysis of tuff (rock) and tuff based mortars (as aggregate) indicate a high content of zeolites of about 60%, quartz and feldspar.

Microscopical analysis on thin sections prepared according to STAS 6200/3-81 [11] (at 28, 56 and 90 days) revealed the mineralogical content of the mortars and tuff, their transformations and alteration processes.

In the case of the classic mortar (sample Rl), after 28 days (Fig. 2(a)), it was discovered that a crown reaction (of the silicates with cement carbonates) occurs between the quartz and the cement, a reaction which is consistent of microliths (very poorly crystallized material). It contains two types of isotropic minerals in a colloidal state (possibly opal) and phyllosilicates (zeolites). At the contact between cement and micas, a silicate is formed as a

mineral reaction (the colloid turns form soil to gel), but less resistant than the one from the contact of cement with quartz.

At 56 days (Fig. 2(b)), some additional transformations are formed by loss of water (natural drying of the samples) and by the recrystallization of the iron hydroxide. Thus was formed the cryptocrystalline silica, the reaction zone around the quartz, the micas were decomposed, chloritised and deteriorated, forming clay minerals and chlorite. Clay minerals formed on the basis of such micas also attack the feldspars, which are thus turned into sericites and clays in the cracks and inside. The percentage of pores increased, being filled with calcedony (small yellow fans due to the crystallization of Si02 gels).

Groundmass at 90 days (Fig. 2(c)) shows an advanced recrystallization which causes fusion with the crown; there are fewer and fewer reactions, and more and more crystallizations - the size of new minerals, increases. The percentage of pores increases, but their dimensions are small, with rounded shapes and dusted with silica; the porosity is due to the transformation of colloidal minerals into cryptocrystalline minerals.

Fig. 2. Sample R1 analysed at 28 days (a), 56 days (b), 90 days (c); (a) 1-Biotite lithoclast; 2- Feldspar, 3- Mica (Muscovite) , 4- Opaque minerals (iron hydroxides), 5- Quartz, 6- Carbonate groundmass, 7- Alteration around the Feldspars, 8-Alteration around the Biotite; (b) 1-

Feldspars zeolitized on the borders; 2- Muscovite; 3- Inclusion in the quartz, 4- Zeolites, 5- Mica (Biotite), 6- Opaque minerals, 7-Thin anizotrope crown , 8- groundmass (carbonate cement); (c) 1- Biotite transformed into clayey minerals , 2- zeolitized feldspars, 3- Feldspars, 4- Iron hydroxides affecting the feldspars, 5- Opaque minerals, 6- Muscovite, 7- Quartz, 8- groundmass (carbonate cement), 9- Pore; scale

bar is 100 microns

After 28 days (Fig. 3(a)) in the case of the R2 mortar sample, the carbonates crown around the quartz and feldspars is very fine. At 56 days (Fig. 3(b)), muscovite appears in the feldspar cracks, the voids tend to be rounded and there is a clear distinction between fundamental mass and large clasts of quartz and biotite. At 90 days (Fig. 3(c)), the feldspars are intensely altered, zeolitized, clay minerals have penetrated the cracks.

Fig. 3. Sample R2 analysed at 28 days (a), 56 days (b), 90 days (c); (a) 1- Microcline, 2-Quartzite lithoclast, 3- Biotite,4- Mica, 5- Clayey groundmass, 6- Feldspars ; (b) 1- Criptocristaline groundmass, 2- Feldspar with reaction crown on the border, 3- Mica, 4- Intense alteration on the borders of the quartzite, 5- Alterated feldspars, 6- Fine crown around the quartz; (c) 1- Large pores, 2- Criptocristaline groundmass, 3- Mica, 4- Quartzite-intense altereted on the borders, 5- Alterated feldspar, 6- Fine crown around the quartz; the scale bar is 100 microns

In the case of the sample R3, at 28 days (Fig. 4 (a)), voids appear due to tension between mineral particles. There is a lot of isotropic cryptocrystalline material, probably incompletely crystallized, colloidal material, devitrificated volcanic glass and oxy iron hydroxides. Iron oxides and opaque minerals can affect the resistance of mortars in time due to the fact that iron hydroxides form gels.

At 56 days (Fig. 4(b)), the matrix began to crystallize (cryptocrystalline carbonate) and there are more and more iron hydroxides (limonite is formed around opaque minerals due to the reaction of the water in the mortar with opaque minerals). Around the feldspar, new minerals appear, in the form of fine flakes, the reaction spread being like a diffused crown around the feldspar. Opaque minerals were also involved in the reactions. At 90 days (Fig. 4(c), there is a crown reaction that determines the rounding of the clasts at corners of the quartz. Around the feldspars, appears an alteration area with the formation of clay minerals (isotropic areas). To the exterior of this alteration area follow a crown which makes contact with the cryptocrystalline matrix consisting of carbonates and clay minerals.

Fig. 4. Sample R3 analysed at 28 days (a), 56 days (b), 90 days (c); (a) 1-Zeolitized feldspars, 2-Aggregate of tuff and volcanic criptocristaline glass, 3- Opaque minerals (Iron hydroxides), 4- Ferulitic structure from volcanic glass, 5- transformation of the glass (devitrification); (b) 1- Feldpar, 2- reaction crown with the new minerals (clay or carbonate), 3- Iron hydroxides ;(c) 1- Tuff lithoclast, 2-Quartz, 3- Feldspar, 4- Alteration zone (clayey minerals forms on the feldspars), 5- reaction crown outside the alteration zone, 6- Matrix-mixture of carbonate and clayey mineral,7-Mica, 8-reaction crown around the tufflithoclast, 9- reaction crown around the quartz; the scale

bar is 100 microns

Microscopical analysis on thin sections and X-ray diffraction of the tuff sample, revealed the high percentage of feldspars, zeolites (clinoptilolite, heulandite) and quartz (Fig. 5(a)).

Polished sections show a high apparent porosity of mortars made of tuff instead of classical mortar, but closer to that of volcanic tuff stone (Fig. 5(c), Fig. 6(a), (b), (c)).

Fig. 5. The tuff- Sample R4- (a) Thin section:l-Feldspars ; 2- Opaque minerals; 3-clayey groundmass; 4- Quartz; Pores; the scale bar is 100 microns (b photomicrographies of the porosity in binary images; the scale bar is 1 mm

Fig. 6. Photomicrographies of the porosity in binary images; (a) sample R1 (classic mortar); (b) sample R2 (mortar with tuff substitute the cement); (c )sample R3 (mortar with tuff substitute the aggregate); the scale bar is 1 mm

The image analysis on porosity was performed on polished sections, on surfaces perpendicular to the direction of casting of mortars. Thus we found that mortars based on tuff as a substitute to cement have porosities of 22% and those based on the aggregate tuff around 17.3% while classic mortar has 8% and tuff sample 46.1%.

4. Conclusions

Mechanical and physical determination, realised on building materials analysed in these paper, do not confer enough data regarding their behaviour during life time. Mineralogical analysis (XRD, and thin sections) complete these date being possible designing new buildings based on sustainable principles.

Regarding mortars, microscopy highlighted mineralogical transformations that took place in mortars (altered feldspar, micas and quartz, zeolitizations of volcanic glass, formation of iron hydroxides).

The mortar samples present different corosion degrees to the quartz and feldspar clasts, more intese to recipes R1 and R3 and diminished to recipe R2; this fact sugest a better mineralogical stability of the mortar with tuff as substitute of cement than that with tuff as aggregate or the clasical mortar.

In the samples R3 the quantity of calcite is higher that of the sample R1 (see X-ray analysis), while the calcium oxy -hydroxides content, as products of cement hydroxylation, in R3 is higher that Rl, probably due to the other mortar compounds (feldspar, zeolites).

The transformation of CaO into CaC03 shows an accentuated chemical stage activity (see thin sections- the criptocrystaline carbonate groundmass and the crown around the quartz and the feldspars). The groundmass aggressiveness (posible of the calcite) to the quartz, is due to the accentuated chemical reactions at the boundary quartz- carbonate groundmass.

Using the tuff (as aggregate or as substitute of cement) these mortars will be more compatible with the tuff stone, as mineralogical composition, mechanical strength (the values are closer than in case of sample Rl) and as reaction with the environmental factors. Volcanic tuff used as rock and binder/aggregate are building material with low embodied energy (does not require to be burn) and low manufacturing cost (120 euro/t).


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