Available online at www.sciencedirect.com
ScienceDirect Procedia Engineering 193 (2017) 192 – 197
International Conference on Analytical Models and New Concepts in Concrete and Masonry Structures AMCM’2017
Evaluation of clinker microstructure changes resulting from different subsoil contacts after long-term exposition to Polish climate conditions Maria Wesoáowskaa,*, Anna Kaczmarekb a
University of Science and Technology in Bydgoszcz, Department of Building and Building Physics, Kaliskiego 7, 85-796 Bydgoszcz, Poland
Abstract A face wall is defined as an element applied inside or outside which should have an attractive look. The achievement of expected results is very difficult. Usually, during the first years of exploitation efflorescence appears, covering mostly clinker surface. This is primary efflorescence which should disappear within the first year of exploitation. Long-term observations led by the author on real objects indicate that this period is definitely longer, and efflorescence change depending on seasons of the year. The essential influence has the wall and subsoil contact area. This is an area especially endangered with rain and soluble compounds contained in water. The cyclic character of these changes influences the clinker microstructure. This paper deals with clinker microstructure changes resulting from ten years of exposition to external climate. There are three cases of wall and ground contact: a tight concrete band, humus layer, and gravel filter layer. The tests were performed on a field station located at the University of Science and Technology in Bydgoszcz. Three types of clinker walls with different mortars were analyzed. Six samples of bricks designed for wall erecting were taken as initial material for microstructure evaluation. The tests were led on 5 mm thick face layer of bricks. Based on observation there were indicated areas of the biggest efflorescence intensity. Microstructure evaluation was done using mercury porosimetry method. The results obtained were used for comparative analysis of meso- and macropore share changes in clinker after ten years of functioning in external environment. These tests let us indicate the best solution taking into account the wall and ground contact. ©2017 2017The TheAuthors. Authors. Published by Elsevier Ltd.is an open access article under the CC BY-NC-ND license © Published by Elsevier Ltd. This (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the International Conference on Analytical Models and New Peer-review responsibility of the scientific committee of the International Conference on Analytical Models and New Concepts in Concrete and Masonry Structures. Concepts inunder
Concrete and Masonry Structures
Keywords: face wall; mercury intrusion porosimetry; subsoil contact
* Corresponding author. Tel.: +48 52 340-86-79. E-mail address:
[email protected]
1877-7058 © 2017 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 the scientific committee of the International Conference on Analytical Models and New Concepts in Concrete and Masonry Structures
doi:10.1016/j.proeng.2017.06.203
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1. Introduction One of the problems with contemporary face walls is their esthetics lowering due to salt crystallization. No matter which wall-mortar material set is used, on most of new buildings during the initial years of exploitation efflorescence appear with various intensity and chemical content. Considering a complex character of interactions, there are two basic groups of destructive factors [1]. The first one are environment and external factors, including direct disposition of chemical pollutants. The second group are internal factors including properties of built-in materials and their interactions. These factors result in transport, crystallization, and transformation of soluble mineral salts. Because of these processes crystal efflorescence can appear as well as pilling off ceramic surface and clinker microstructure damage [2]. The above actions were described with exposition classes. They define factors directly affecting construction, which in turn define the selection of appropriate wall elements, thus setting the structural wall protection. In face walls, the area most endangered by environment impact is the direct contact with substructure. In this zone there is extended intensity of rainfall, splash water, subsoil moisture, and persisting snow cover. During last years it was noticed increased interest in numerical research of mineral salts transport in porosity materials [3]. Mathematical model created and their results gained from experimental research significantly contributed to development of computer programs modeling influence of salt crystallization process on building material strength and consequently, on face walls durability [4,5]. Simulation researches [6] indicate that in case of a brick wall, subsurface tensions can reach close to brick ultimate tensile strength equal to about 1N/mm2. It can lead to wall surface scars and damages. From 2006 at the site of the University of Science and Technology in Bydgoszcz (Poland) there has been functioning a field research station in order to evaluate esthetics and durability of face walls. The walls were shaped in such way that they cover most of typical influences of external environment. For observation of wall-ground contact influence there were three options modeled: gravel filter layer, tight concrete band, and humus with a lawn. Based on multi-year research it was stated that cyclic crystallization is present with particular intensity in spring (April for the discussed location). Analyses performed for appearing efflorescence showed that intensity and size of area covered depends not only on mortar used but also on solution of wall surrounding area. Additionally, the biggest salt concentration is present in a 5 mm layer close to ground surface, independent of wall-ground contact solution used [7]. 2. Research methods 2.1. Field research station Field research station was located at premises of the University of Science and Technology in Bydgoszcz (Poland). The research station includes eight test one-brick thick walls sized 1.61 x 1.42 m. Table 1. Composition of tested mortars Contents of 1 m3 Mortar
CEM 1
Proportion
Cement
Lime
Sand 3
Plasticizer
Water
of components
[kg]
[kg]
[m ]
[kg]
[m3]
(c:s)=1:3.5
378 CEM I 42.5N
-
1050
-
0.253
CEM + plasticizer
(c:s)=1:3.5
378 CEM I 42.5N
-
1050
0.4
0.233
C-L
(c:l:s) = 1:1.25:6.75
165CEMI 42.5N
97
950
-
0.304
The walls are situated with utmost sides facing wind direction distinguished on this area according to weather reports of Voievodship Inspectorate of Environment Protection in Bydgoszcz (Poland). Clinker brick was used to build the walls in sets with eight different mortars of which six had a known material content while two others were ready-made system mortars intended to use for face walls in order to eliminate efflorescence (Fig. 1). For purposes
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Maria Wesołowska and Anna Kaczmarek / Procedia Engineering 193 (2017) 192 – 197
of this elaboration 3 walls with mortars indicated in Table 1were selected.
Fig. 1. Test wall for field research 1 – underfelt-insulation separating the analysed areas, 2 clinker semi-fitting, 3 – clinker fitting with a singleside edge bevelling, 4 – clinker roof
In the test station three variants of contact with ground surface were modelled (Fig. 2): humus with lawn, gravel filter layer, tight concrete band. The distinguished areas are separate fragments of the wall, separated with a layer of vertical, tight insulation made of asphalt underfelt. The solution prevents the migration of moisture and salt from the adjacent surface. Insulation protecting against moisture was used in the designed wall at the following two levels: foundation wall (10 cm below ground level), - 50 cm above the ground level.
Fig. 2. Cross-section of the test wall for field tests 1 – footway edging, 2 – plant soil, 3 – concrete belt, 4 – filtration layer - gravel 32/63 mm, 5 – filtration geotextile (non-woven) SF 37, 6 – foundation
The insulation was intended to protect against water migration from the foundation concrete (level 1) as well as
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Maria Wesołowska and Anna Kaczmarek / Procedia Engineering 193 (2017) 192 – 197
to separate the area exposed to splashed water (level 2) in different options of contact with the ground. When the substrate was hardened (concrete belt), the splashed water reach was 50 cm. For a rough surface that strongly dispersed precipitation water (loose gravel pack, humus with lawn), the height of activity was reduced to approx. 20 cm. In winter, the walls were exposed to snow. The reach of this hazard depends on the snow-cover thickness which, in the analysed location, did not exceed 50 cm. 2.2. Preparation of samples to researches Two groups of bricks were analyzed: - in initial state before building into the walls (from 6 bricks 5mm thick layers were cut from face layer with water-cooled diamond saw; cutting remnants were rinsed with pressurized water stream). - after building into the wall and 10-year of exposition to external climate conditions (for each wall with modeled various contacts with subsoil there were taken 3 clinker samples from face layer of 5mm in thickness; then they underwent a process of salt extraction multiple rinsing and soaking). Such prepared samples were dried to constant mass for 72h in temperature of +105 ± 5°C and cooled to 40°C in an exsiccator. Directly before the porosimetry test, samples were weighed with tolerance of 0.001g and put in penetrometer, installed in a low pressure port. 2.3. Mercury Intrusion Porosimetry test Microstructure tests were performed with AutoPore IV 9500 series porosimeter equipped with two ports: low and high pressure of maximum value of 33000 psia (228MPa), which lets measure in the range within meso- and macropores (od 2nm do 360ȝm). Before the particular test a calibration and „blank test” were made – setting the volume, compressibility, and thermal effect of the penemometer applied. Based on control measurements the balance time was stated equal to 30s. Resulting from prepared samples measurements the following structure parameters were stated: total pore volume, sample volume and its skeleton density, pore volume distribution in function of their diameter as integral and differential relationship. The volume share of these pores was calculated according to the formula: 50 nm
U MEZO
¦ =
U MAKRO =
i = 2 nm
IVMEZO
TIV
¦
i =50 nm
⋅P
IVMAKRO
TIV
(1)
⋅P
(2)
where: IVMAKRO - % of macropores share >50nm, IVMEZO - % of macropores share 2-50nm, TIV – total intrusion volume, P – general porosity. 3. Results and discussion As a result of Mercury Intrusion Porosimetry there were gained the basic clinker microstructure parameters. Based on tests performed it was stated that during 10 years of face walls exploitation, changes in face wall surface layer occurred in different solutions of contact with subsoil including meso- as well as macropores (Table 2,3,4). Despite of mortar type used linker from the wall area contacting with a tight concrete band indicated the highest porosity increase related to the initial sample. Its value was influenced mainly by macropores share increase in the diameter range over 100000nm. In the zone of gravel band after 10 years of exposition the porosity of clinker is close to the initial sample. Also macropore share is comparable. The contact of the wall with humus caused microstructure changes in form of porosity decrease comparing to initial sample as well as other sets.
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Table 2. Basic parameters of tested clinker sample microstructure from masonry on CEM I mortar Microstructure Parameters
Original Samples
plant soil
10-year of environment exposition concrete band gravel layer
Mercury intrusion, mL/g
0.1040
0.095
0.1077
0.1036
Mean volume pore size, nm
3474.3
5938.7
6714.0
2537.0
Volume density, g/mL
2.0760
2.0873
2.0511
2.0681
Specific weight, g/mL
2.6474
2.6037
2.6326
2.6223
Porosity. %
21.5827
19.8336
22.0904
21.4348
Mesopores 2-50nm, %
21.56
19.8196
21.9432
21.1475
Macropores > 50nm, %
0.02
0.104
0,1472
0.2873
Table 3. Basic parameters of tested clinker sample microstructure from masonry on CEM I with plasticizer mortar Microstructure Parameters
Original samples
plant soil
10-year of environment exposition concrete band gravel layer
Mercury intrusion, mL/g
0,1040
0.0909
0.1158
0.1041
Mean volume pore size, nm
3474.3
4261.9
7494.9
4232.6
Volume density, g/mL
2.0760
2.1193
1.9676
2.0406
Specific weight, g/mL
2.6474
2.6249
2.5480
2.5908
Porosity. %
21.5827
19.2629
22.7777
21.2349
Mesopores 2-50nm, %
21.56
19.1687
22.6993
21.1306
Macropores > 50nm, %
0.02
0.9420
0.0784
0.1043
Table 4. Basic parameters of tested clinker sample microstructure from masonry on cement-lime mortar Microstructure Parameters
Original samples
plant soil
10-year of environment exposition concrete band gravel layer
Mercury intrusion, mL/g
0.1040
0.1161
0.1169
0.0866
Mean volume pore size, nm
3474.3
3165.8
4916.7
3965.9
Volume density, g/mL
2.0760
2.0163
2.0075
2.1457
Specific weight, g/mL
2.6474
2.6328
2.6260
2.6353
Porosity, %
21.5827
23.4157
23.4653
21.5807
Mesopores 2-50nm, %
21.56
23.2666
23.3357
21.4522
Macropores > 50nm, %
0.02
0.1491
0.1296
0.1215
4. Conclusions In this paper, changes were analyzed in clinker with different solutions of wall contact with subsoil around it under influence of multi-year exposition to external environment. The tests were performed on three tests walls made with mortar of Portland cement CEM I, Portland cement CEM I with plasticizer and cement-lime one. The analysis included changes of microstructure of clinker brick after ten years of exploitation.
Maria Wesołowska and Anna Kaczmarek / Procedia Engineering 193 (2017) 192 – 197
Based on Mercury Intrusion Porosimetry it was stated that ten years exploitation of a wall covered with efflorescence caused changes in microstructure of the face layer. The changes observed are the effect of humidity and soluble mineral salts interactions. Due to variable climate parameters salts crystallize in subsurface layers filling a part of pores. Crystals growing inside pores act on skeleton sides, causing appearance of additional tensile stresses which effect in porosity increase. The three selected types of substrate analysed in the study indicate that a gravel filtration layer offers the most favourable solution. It reduces the possibility of water capillary rise from the ground and minimized the reach of splashed water.
Acknowledgements The work was done using apparatuses within the frame of „Realization of 2nd Stage of Regional Centre of Innovation” project, co-financed from means of the European Fund for Regional Development within the frame of Regional Operational Program of the Kujawsko – Pomorskie Voievodship for years 2007 – 2013.
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