Advanced Materials Research Vol. 897 (2014) pp 280-283 Online available since 2014/Feb/19 at www.scientific.net © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMR.897.280
PERLITE CONCRETE BASED ON ALKALI ACTIVATED CEMENTS Vit Petranek2b, Pavel Krivenko1a, Oleg Petropavlovskiy1c, Sergii Guzii1d 1
Scientific Research Institute for Binders and Materials, Kiev National University of Civil Engineering and Architecture, Vozdukhoflotskyi prospect, 31, Kiev 03680 Ukraine
2
Brno University of Technology, Faculty of Civil Engineering, Institute of Technology of Building Materials and Components, Veveri 331/95, 602 00 Brno, Czech Republic
a
[email protected],
[email protected],
[email protected],
[email protected]
Keywords: Alkali activated cement, concrete, expanded perlite, interfacial transition zone.
Abstract. The use of the alkali activated cements for the manufacture of perlite concrete pressed and vibro-pressed products for heat insulation intended for various purposes was studied. The interfacial transition zone “perlite grain – cement stone” was examined in order to reveal features of its formation. These features allow to create a dense and strong shell/caging around the perlite grain which helps to avoid its corrosion and produce perlite concretes with high durability. Introduction An expanded perlite is known as highly efficient heat insulating material with a bulk density ranging between 60 kg/m3and 140 kg/m3. The advantages of this material are its high thermal resistance, ecological friendliness, simplicity of manufacture, and large quantities available in Ukraine [1]. The problems associated with its wide application in the manufacture of highly efficient building products and structures are attributed to lack of such binders, that could meet the requirements of contemporary construction and, on the contrary to the generally accepted binders, would be intoxic, incombustible and would provide rather high strength of building products made from the expanded perlite. Traditional portland cements do not allow to reach target physico-mechanical characteristics and durability of the building materials from perlite [2]. Since an expanded perlite is a chemically active aggregate, with time the perlite grains in the interfacial transition zone "perlite – portland cement" start to corrode. As a result of this process, the colloidal solutions with restricted mobility are formed and accumulated. This will result in the increased osmotic pressure followed by deterioration of building products and structures especially in the conditions of the increased humidity. The use of the alkali activated cements will allow to avoid these deleterious effects [3]. Purpose of study – to determine physico-mechanical properties of the perlite concretes made using various alkali activated cements and to study processes of structure formation in the interfacial transition zone “perlite - alkali activated slag cement”. Raw materials and test procedures An expanded perlite sand according to DSTU B V.2.7-157:2011 with a mean bulk density of 75 – 120 kg/m3 from Ukrainian local deposits was used in the study. Alkali activated cements (national standard of Ukraine DSTU B V.2.7-181:2009) and metakaolin-based geocements [4] (normative document TU U В2.7–16403272.001–97, Ukraine) were used as binders. Sodium silicates with silicate modulus Мs=1 – 2.8 and density = 1150 – 1400 kg/m3 were used as alkaline activators in the alkali activated cements. In order to decrease a hygroscopic water adsorption, water-repelling agents selected from a group of polyhydrosiloxanes were added to the mixtures. Manufacturing technology for making pressed heat insulation building products included the following stages: preparation of the perlite concrete mixture, pressing at excessive pressures All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 212.26.143.18, V.D.Glukhovsky Scientific Research Institute for Binders and Materials, Kiev National University of Civil Engineering and Architecture, Kiev, Ukraine-09/04/14,11:35:45)
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ranging between 0.035 and 0.5 MPa and thermal treatment. Depending upon a binder type, temperature of heat treatment was 100 – 300 оС (duration – 30 – 40 min.) in case of the geocement, or 60 – 100 оС (duration – 4 – 6 hr) in case of the alkali activated slag cement and alkali activated portland cement. Examination of structure formation processes was done using a electron probe microanalyzer, and a hardness-testing machine “TN152” for the determination of a microhardness of the interfacial transition zone. Optimization of the concrete mixtures was done in terms of physico-mechanical characteristics as functions of density of the expanded perlite, pressure of pressing and cement content using methods of mathematical planning of experiments. Discussion of results Properties: The results of tests of the perlite concretes made using various cements are given in Table. Table. Basic physico-mechanical characteristics of the perlite concretes made using various cements as a binder Class in density 150 200 250 300 Binder- geocement Binder content [% by volume] 3.0 6.0 8.0 10.0 Compressive strength [MPa] 0.25 0.30 0.35 0.45 Flexural strength [MPa] 0.15 0.15 0.20 0.30 0.062 0.068 0.076 0.082 Heat conductivity at 25оС [W/(m⋅оС)] Binder- alkali activated slag cement Binder content [kg/m3] – 66 80 110 Compressive strength [MPa] – 0.30 0.38 0.58 Flexural strength [MPa] – 0.2 0.3 0.37 Heat conductivity at 25оС [W/(m оС)] – 0.06 0.073 0.084 Binder- alkali activated portland cement Binder content [kg/m3] – 60 77 107 Compressive strength [MPa] – 0.33 0.41 0.59 Flexural strength [MPa] – 0.19 0.32 0.41 – 0.065 0.071 0.082 Heat conductivity at 25оС [W/(m⋅оС)] Binder- ordinary portland cement Binder content [kg/m3] 80 110 − − Compressive strength [MPa] − − − − Flexural strength [MPa] 0.16 0.20 − − 0.075 0.085 Heat conductivity at 25оС [W/(m⋅оС)] − − Characteristic
350
400
– – – –
– – – –
140 0.6 0.41 0.100
200 0.7 0.48 0.120
138 0.65 0.45 0.103
182 0.72 0.51 0.125
140 − 0.23 0.11
200 − 0.26 0.13
The results of study suggested to conclude that with the higher cement content. pressure of pressing and density of the perlite – the strength tends to increase. though insulation characteristics tend to lower. The higher chemical activity of an alkaline environment with regard to perlite allows for to produce more efficient perlite concretes due to the alkali activated cements compared to those made using portland cements. Structure formation in the interfacial transition zone: A conclusion was drawn that a structure of the interfacial transition zones in the perlite concretes made using the alkali activated slag cements was characteristic of dense and strong shell/caging consisting of the cement 40 – 60 mkm in thickness. Its microhardness is by 20 – 25 % higher than that of the cement stone in the space between the grains. The cement mortar penetrates into the depth of the perlite grains to a distance of 100 – 130 mkm. as a result a total width of the interfacial transition zone is 140 – 190 mkm.
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The physical-chemical processes in the interfacial transition zone “expanded perlite- alkali activated slag cement” take place at low concentrations and high contents of silicon. The grains of the expanded perlite. as well as those of the granulated slag of which the alkali activated slag cements consist. are themselves aluminosilicate glasses containing alkali metal (Na, K) compounds which are known to be a reason of alkali-silica reaction (ASR) in portland cement concretes made with expanded perlite as an aggregate [5]. The examination of the distribution of main chemical elements in the interfacial transition zone “expanded perlite- alkali activated slag cement” showed the increased concentration of Na and K in a layer up to 50 µm from the apparent line of the contact towards the cement stone (Fig.1). since during interaction of the expanded perlite with the alkali activated slag cement the present Na and K create an auxiliary source of alkaline component. 2.85
2.54
2.87 2.3
2.55 2.2
Al Si
18
21
24
20
25.6
28.4
Ca
21.2
22
22
20 7.2 1.14
0.52
0.78
0.4
K 2.1
3.5
3.5
Na 300
21
17
200
100
Apparent line of the contact
Relative intensity of elements [%]
2.3
7.8
0
100
Binder Perlite Width of scanning of the interfacial transition zone [mkm]
Fig.1. Elemental distribution in the interfacial transition zone "expanded perlite – alkali activated slag cement” With increase in the Na and К concentrations. the Ca concentration decreases due to formation of the low-basic calcium silicate hydrates. A nearly uniform distribution of Si and Al over the width of the interfacial transition zone may testify that a silica gel. that is formed as a result of the interaction of the alkali activated cement with an aluminosilicate constituent of the perlite. is not accumulated in the interfacial transition zone. Just this is a main reason of differences of the interfacial transition zones under study and those between the portland cement and alkali- silica reactive aggregate [6]. Application A model sample of a hollow-core wall block to be produced using a principle of “permanent (retained) shuttering” was prepared using the alkali activated portland cement. The blocks (weight – 8 − 12 kg) had the following characteristics: mean density – 295 kg/m3; compressive strength – 0.6 MPa; flexural strength – 0.4 MPa; heat conductivity – 0.079 W/m °С (Fig.2). The developed manufacturing process parameters for making dense wall heat insulation blocks using the alkali activated slag cement as a binder allow for to produce products with the following
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characteristics: mean density of 450 − 1150 kg/m3; сompressive strength – 1.2 − 16 MPa; heat conductivity in a dry state (λс) − 0.08 − 0.18 W/m.°C; freeze/thaw resistance − over 35 cycles. The developed compositions of heat insulation boards have been tried on a pilot-scale (Fig.3). The boards had the following characteristics: mean density of 200 – 300 kg/m3; compressive strength − 3.0 − 4.5 MPa; flexural strength – 1.5 − 3.0 MPa; heat conductivity − 0.064 − 0.090 W/m °С (Fig.3).
Fig. 2. Heat insulation perlite concrete block (binder- alkali activated portland cement) (400×300×200 mm)
Fig. 3. Manufacture of heat insulation boards from perlite and alkali activated slag cement
Conclusions The use of alkali activated cements as a binder for making perlite concrete blocks showed their higher efficiency with regard to physico- mechanical properties and durability compared to the products made using traditional cements. Acknowledgements This work was financially supported by the MSM 0021630511 research project and state budget via Ministry of Industry and Trade of the Czech Republic (project TIP, number FR-TI2/340). Cooperation was enabled by the project CZ.1.07/2.3.00/30.0005 SUPMAT – Support for the creation of excellent interdisciplinary research teams at Brno University of Technology. References [1] [2]
[3]
[4]
[5] [6]
V.D. Glukhovsky et al.: Basics of Technology for Finishing. Heat- and Hydro-insulation Materials. − Kiev: Vyscha Shkola. 1986. V.L. Gerasimchuk: Influence of properties of aggregates on structure and strength of the alkali activated slag cement concretes: PhD Thesis. − Kiev Civil Engineering Institute. Kiev. Ukraine. 1982. P.V. Krivenko, О.N. Petropavlovskii, O.G. Gelevera, V.B. Prima: Alkaline perlite concrete and products from it //Collection of papers “Individual residential house” - Vinnitsa. 2001. pp.34-39. V. Petranek, S. Guzii, P. Kryvenko, K. Sotiriadis, A. Kravchenko: New Thermal Insulation Material Based on Geocement. Advanced Materials Research Vols 838-841. 2014. pp.183187. Information on wwww.scientific.net/AMR.838-841. 183 A.S. Timofeeva: Investigation of the processes of interaction processes between silica of perlite and alkalis of cement. PhD Thesis. Kiev. 1972. pp 22. V.M. Moskvin, G.S. Royak: Corrosion in Concrete due to Interaction of Alkalis from Cement and Silica of Aggregate. Gosstroiizdat. Moscow. 1962.
Binders and Materials XI 10.4028/www.scientific.net/AMR.897
Perlite Concrete Based on Alkali Activated Cements 10.4028/www.scientific.net/AMR.897.280
