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Sensors and Materials, Vol. 31, No. 3 (2019) 1071–1081
MYU Tokyo
S & M 1835

Discussion on the Material Factors for Falling of Face Tile
Wei-Ling Hsu,1 Chen-Chung Liu,2 Yan-Chyuan Shiau,3*
Chao-Lung Wang,4 and Wen-Chin Lin5
1

Huaian Key Laboratory of Geographic Information Technology and Applications,
School of Urban and Environmental Science, Huaiyin Normal University,
No. 111, ChangJang West Road, Huai’an City, Jiangsu Province 223300, China
2
Department of Civil Engineering, Chung Hua University, Hsinchu,
No. 707, WuFu Road, Section 2, Hsinchu 30012, Taiwan
3
Department of Landscape Architecture, Chung Hua University, Hsinchu,
No. 707, WuFu Road, Section 2, Hsinchu 30012, Taiwan
4Department of Construction Management, Chung Hua University, Hsinchu,
No. 707, WuFu Road, Section 2, Hsinchu 30012, Taiwan
5Department of Architecture & Urban Planning, Chung Hua University, Hsinchu,
No. 707, WuFu Road, Section 2, Hsinchu 30012, Taiwan(Received November 7, 2018; accepted January 21, 2019)

Keywords: cement mortar, face tile construction materials, cement mortar ratio, pullout intensity,
temperature variation, polymer resin, falling off

Face tile installation materials mainly comprise concrete, cement mortars, an adhesive layer,
face tiles, and a face tile sealing layer. Problems in any of the aforementioned parts result in apoor face tile adhesion quality. In this study, material information relevant to face tile falling
was investigated, tests were planned and conducted to obtain construction variation factors,
advanced sensing instruments were used to detect the health of concrete, and new materials
were added to samples with low pullout values to increase the pullout values of face tiles. The
results showed that the tensile strengths of the tiles were effectively improved. Thus, thismethod may serve as a reference to effectively reduce face tile debonding.

1.

Introduction

1.1

Research backgroundTaiwan is located in the Ring of Fire (a seismically active zone) and at the junction of thePhilippine Sea Plate and the Eurasian Plate; thus, earthquakes are frequent in Taiwan. In
addition, the coastal regions of Taiwan are subject to constant weather changes.(1) Sustainable
construction is the leading reference for the design, construction, and operation of highperformance green buildings.(2) The Life Cycle Assessment has been applied in the construction
sector since the 1990s and is now continuously embedded in European public policies, e.g., forEnvironmental Product Declaration regulation or for building labeling schemes.(3) Since the1999 Jiji earthquake, people have begun to attach considerable attention to the structural safety*

Corresponding author: e-mail: ycshiau@ms22.hinet.net
https://doi.org/10.18494/SAM.2019.2219
ISSN 0914-4935 © MYU K.K.
https://myukk.org/

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Sensors and Materials, Vol. 31, No. 3 (2019)of buildings, and related standards have been formulated and revised to compensate for previous
deficiencies. However, no clear construction and related standards are in place to ensure thequality of decorative face tiles installed on building facades. This regularly results in face tiles
falling off surfaces within a few years after building completion. Advanced material sensors
such as chloride ion analyzers and concrete humidity monitors were applied to measure theconcrete and tile cement materials to master the relevant quality of concrete, cement mortar, andadhesive. The appropriate countermeasures were explored to solve the problem of falling tiles
in this study.
1.2

Literature review

1.2.1 Exploring reasons of falling external wall tiles
Architectural tiles are an important material in building facade design.(4) Partial fill
grouting may cause workmanship defects in tile grouting.(5) An exterior tile cladding can suffer
debonding or adhesive failures as it ages.(6) Damage to external wall face tiles can be divided
into two categories, which are wear-and-tear-led damage and earthquake-led damage. Similarly
to the failure rates of industrial tools, the failure rates of face tiles can be represented by abathtub curve (Fig. 1). The discontinuous nature of the core results in a nonuniform stress fieldunder the in-plane loading of the adhesive layers.(7) Dorokhova et al. have proposed and tested
an energy-conserving technology for shrink-free face materials.(8) In general, external wall
tile damage occurs following project completion, and the causes of such damage are normallyunfavorable designs, unsuitable materials, and poor construction quality. Face tile damage
can be classified into four different types, namely, debonding, flaking, cracks, and stains. Of
the four types of face tile damage, debonding and flaking lead to the most serious pedestrian
injuries. Environmental changes, such as temperature and humidity changes, cause internal
stresses within face tiles installed on walls. When this stress is greater than the adhesion

Fig. 1.

(Color online) Bathtub curve.

Sensors and Materials, Vol. 31, No. 3 (2019)1073

strength between the walls and the tile materials, peeling ensues. Face tile installations
primarily comprise a concrete layer, cement mortars, an adhesive layer, face tiles, and different
interfacial layers; debonding or peeling generally occurs at the interfaces of the different layers.
Debonding may be further divided into the following forms (Fig. 2):(9)A. interfacial debonding that involves cracking in the sealing layer between face tiles;
B. interfacial debonding between face tiles and adhesive;
C. interfacial debonding between adhesive and cement mortars (in the lowest layer);
D. interfacial debonding between cement mortars (in the lowest layer) and concrete.
1.2.2 Adhesion changes in the interface joining concrete and cement mortars
In face tile projects, the adhesive strength between concrete and cement mortars is affectedby various factors, which include (1) interfacial adhesiveness, (2) interlocking effect between
friction and aggregates, and (3) time. The aforementioned factors also mutually affect each other.(10)An overview of the factors is provided as follows:
A. Interfacial adhesiveness: Interfacial adhesiveness is primarily affected by factors such as
the type of adhesive used, material firmness, surface cleanliness, interface humidity, test
specimen age, and surface roughness.
B. Interlocking effect between friction and aggregates: The interlocking effect between friction
and aggregates is mainly affected by aggregate particle size, shape, structure, and surface
conditions.
C. Time: Under normal circumstances, when cement mortars are being coated on or poured
onto buildings, the concrete layer of the cement structure has already reached a contracted
state. Subsequently, new layers of cement mortars poured onto the existent layers exhibit aFig. 2.

(Color online) Face tile interfacial debonding.(12)1074

Sensors and Materials, Vol. 31, No. 3 (2019)plastic shrinkage state. The differential shrinkage between the old and new materials results
in interfacial strain, affecting interfacial adhesiveness.(11)1.3

Research motivation

According to a statistical review released by the Directorate-General of Budget, Accounting,and Statistics on April 17, 2018, as of the year end of 2017, the average house age in Taiwan
was 29.53 years old, a figure that showed an increasing annual trend. The average house age in
Taipei City was 33.1 years, which was the oldest of the six special municipalities and indicatedthat Taipei City had the oldest buildings in Taiwan.
Actual construction cases have shown that, on average, tile adhesion begins to deteriorate
in approximately 15–20 years. This, coupled with frequent earthquakes or large temperature
variations, increases the chances of falling tile accidents. Additionally, the greenhouse effecthas recently created severe climate changes, resulting in external wall tiles falling and injuring
nearby pedestrians. This problem has thus raised social concerns. How to improve the outerwall tile adhesive materials to solve the tile falling problem is an important issue.
1.4

Research objectives

To prevent external wall tiles from falling and injuring pedestrians, in this study, we devised
the following research objectives:
A. Review the literature and real-life cases to investigate the activities engaged in during
the cement mortar pouring and plastering processes that lead to the subsequent falling of
external wall tiles; compile the factors of influence of tile adhesion strength;
B. Conduct tests by varying certain conditions with varying conditions (e.g., changing thematerials, component ratios, and weather conditions) to determine the cement mortar tensile
strength levels under different conditions;C. Add polymer resin materials to samples with low tensile strengths before running pullout
tests. The results are to serve as a reference to construction units to prevent external walltiles from falling.
The remainder of this paper is organized as follows: Sect. 2 outlines the methods, Sect. 3
details the pullout test results, Sect. 4 presents the discussion, and finally, Sect. 5 shows theconclusion.

2.

Methods

2.1

Fabricating compression-resistant cement mortars

The experimental methods and materials used in this study are described as follows. In thisstudy, the cement mortar specimens were fabricated by following the CNS1010 R3032 standard,
which involved combining cement with graded standard sand at a ratio of 1 to 2.75 andcombining water with Portland cement at ratios of 1:0.485. Cement-to-sand ratios of 1:3 and 1:5

Sensors and Materials, Vol. 31, No. 3 (2019)1075

were employed to fabricate cement mortars for the lowest layer. The test specimens measured 5× 5 × 5 cm3 and the amounts of materials used are listed in Table 1.
2.2

Compressive strength test

Before the compressive strength test was administered, all water was wiped from the surfaceof the test specimen; any debris found on the two ends of the test specimen was removed; thebearing plates of the machines were polished with sandpaper. A steel ruler was used to inspect
whether the upper and lower sides of the test specimen were even before the test specimen wasplaced in a compressive strength testing machine. The surface of the test specimen on which
force was applied had to closely match with the surface of the bearing plate, and no padding
was used. The test specimen was placed below the center of the bearing plate in the test
machine. The test specimen was estimated to be able to withstand 1400 kg/cm2 of load; during
the initial stage of the test, the load was increased at a relatively high rate before it reached halfof the maximum load, after which the rate of load increase was reduced. The load margin wasmaintained, and the time during which the load was exerted onto the test specimen was required
to last between 20 and 80 s.
2.3

Compressive strength data analysis

Table 2 shows the cement mortar compressive strength data obtained from the compression
tests. The tests were administered by following the CNS1010 R3032 standard. Test specimensof the same age were utilized and the averages of the results were collected; deviations between
the test data and the averages were required to be 10% or less. For the first phase of the test,
two different sand types (i.e., Taiwanese sand and Chinese sand) and cement mortar ratios
were used, and their 7, 14, and 28 d maximum loads were recorded. For both sand types,

Table 1
Materials used to fabricate the cement mortar test specimens.
Component ratio
Cement (g)Sand (g)Water (mL, water–cement ratio 0.485)

1:3
525
1575
273

1:5
350
1750
273

Table 2
Cement mortar compressive strength test results.
Sand type + curing time (d)Taiwanese sand + 7 d
Chinese sand + 7 d
Taiwanese sand + 14 d
Chinese sand + 14 d
Taiwanese sand + 28 d
Chinese sand + 28 d

1:3
361 kg/cm 2
371 kg/cm 2
444 kg/cm 2427 kg/cm 2
500 kg/cm 2494 kg/cm 2

1:5
158 kg/cm 2
160 kg/cm 2
191 kg/cm 2
182 kg/cm 2
232 kg/cm 2
221 kg/cm 2

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Sensors and Materials, Vol. 31, No. 3 (2019)

test specimens of the same age displayed deviations within the 10% requirement; however,
Chinese sand showed a higher compressive strength in the early stage, whereas Taiwanese sanddemonstrated a superior overall compressive strength in the later stage. A water-to-cement
ratio of 1:5 severely hindered the compressive strengths of the cement mortar, indicating that
construction sites must strictly control the water-to-cement ratios of cement mortars.
2.4

Cement mortar pullout tests

2.4.1 Pullout test setup and schematic diagram
The arrangement of the test specimens used in the cement mortar pullout tests is shown in
Fig. 3 and a schematic diagram of the pullout test is shown in Fig. 4.
2.4.2 Weather factor simulations
In addition to concrete fracture, honeycombing, steel oxidation, holes, and release agentinduced concrete surface grease, any interfacial debonding between a cement mortar layer andconcrete can directly or indirectly cause flaking. In this study, we investigated cement mortar
sand sources and used various component ratios and weather (temperature) changes to facilitate

Fig. 3.

Fig. 4.

Setup of the test specimens.

Pullout test schematic diagram.

Sensors and Materials, Vol. 31, No. 3 (2019)1077

interfacial debonding between the cement mortar layer and the concrete. When the climatic
factors were simulated during the 28 d experiment, the test specimens were taken into closed
rooms and heated using electric heaters to 38 ℃ or higher (i.e., the experiment temperature)whenever the daytime temperature failed to reach the required temperature. Daily temperature
variations were recorded, and daily weather and temperature data provided by the Central
Weather Bureau were compared with the temperatures experienced by the test specimens. For
low-temperature simulations, the test specimens were placed inside refrigerators, in which thetemperature was set at 8–10 ℃ to simulate winter temperatures in Taiwan.
2.4.3 Manufacturing tensile-stress-resistant cement mortar test specimens
Cement mortars used to fabricate tensile-stress-resistant test specimens are divided into
two categories, namely, general cement mortars and cement mortars fortified with polymer
resins. In this study, Chia Hsin cement was selected as the cement and Taiwanese sand (whichcontains more mud) and Chinese sand (which contains less mud) were chosen as sand samples.
Onsite personnel were asked to mix the cement mortars. This study used cement mortar ratios
stipulated by the Public Construction Commission (i.e., Chapter 09220: Cement Mortar Plaster),in which the cement-to-sand ratios of 1:3 and 1:5 were employed to make cement mortars forthe lowest layer. For the cement mortars augmented with polymer resins, the ratio of polymer
resins added was identical to that of concrete; that is, the polymer resin-to-sand ratios were also 1:3
and 1:5.
2.4.4 Administering the pullout tests
In this study, pullout test specimens (i.e., 16 total test specimens divided into four groups)
were cemented with square and round steel plates, and maintained for approximately 1 h before
pullout tests were conducted. At the start of the experiments, the pullout testers were affixedover the square or round blocks (Fig. 5) and manual rotational tests were performed. When thesquare and round steel plates peeled off from the test specimen surfaces, the pullout strengths
were recorded.

3.

Results

In this study, three types of test specimens were used in the cement mortar pullout tests.
The method and result of these types are as follows:
A. Type 1: Uncracked cement mortars
A total of 16 test specimens were used, and relevant information regarding ratios and sandcontent was written on the surfaces of the test specimens. The square and round steel plates
peeled off from the test specimen surfaces (Fig. 6); in the uncracked cement mortar samples,the steel plates peeled off the mortar layer surfaces first when pullouts were performed.
B. Type 2: Cracked cement mortars
Various factors may cause mortars to crack after hardening, which leads to decreased
strengths for deep-layer cement mortar and decreased concrete pullout strengths. To

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Sensors and Materials, Vol. 31, No. 3 (2019)

Fig. 5.

(a)(b)(Color online) Tile pullout experiment.

(c)

(d)

Fig. 6. (Color online) Damage to the test specimens during pullout tests. (a) Test specimen 1, (b) test specimen 2, (c)test specimen 3, and (d) test specimen 4.

simulate a cement mortar that cracks after hardening, this study used handheld grinders to
cut the cement mortar specimens and affix them to square and round steel plates. The test
specimens were maintained for approximately 1 h before pullout tests were conducted; thetest results are shown in Table 3. Table 3 shows that a sufficient cement mortar thickness
created high tensile strengths, whereas an insufficient cement mortar thickness created low
tensile strengths and led to peeling. When other conditions were held constant, temperature
variations created cracks in cement mortars, which severely reduced the cement mortar
tensile strength.
C. Type 3: Cement mortars added with polymer resins
Table 3 shows that Specimens 12, 14, 15, and 16 exhibited the lowest tensile strengths.
However, because two cement mortar groups with a water-to-cement ratio of 1:5 had been
used, 12 were replaced with 15 to represent cement mortars with a water-to-cement ratio of 1:3.
In this experiment, polymer resins were added to the test specimens, which produced tensile
strengths approximately two times greater than those of test specimens without polymer
resins (i.e., Type 2 cement mortars; the water-to-cement ratios were kept constant). The
results are shown in Table 4.

Sensors and Materials, Vol. 31, No. 3 (2019)

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Table 3
Type 2 test results.
No.

Area (cm 2)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

25
25
25
25
25
25
25
25
25
25
25
25
25
25
25
25

Max. pullout
load (kN)
2.6
1.8
2.5
1.7
2.2
1.7
2.1
1.6
1.6
1.4
1.5
1.3
1.5
1.2
1.4
1.1

Note:
Thick(3): cement thickness: 3 cm
Ratio(1:3): cement-to-sand ratio: 1:3
Sand(T): Taiwan sandTemp(Nor): Normal temperature

Pullout resistancestrength (kgf/cm 2)
10.6
7.3
10.2
6.9
9.0
6.9
8.6
6.5
6.5
5.7
6.1
5.3
6.1
4.9
5.7
4.5

Notes
Thick(3), Ratio(1:3), Sand(C), Temp(Nor)Thick(3), Ratio(1:5), Sand(C), Temp(Nor)Thick(3), Ratio(1:3), Sand(T), Temp(Nor)Thick(3), Ratio(1:5), Sand(T), Temp(Nor)Thick(1.5), Ratio(1:3), Sand(C), Temp(Nor)Thick(1.5), Ratio(1:5), Sand(C), Temp(Nor)Thick(1.5), Ratio(1:3), Sand(T), Temp(Nor)Thick(1.5), Ratio(1:5), Sand(T), Temp(Nor)Thick(3), Ratio(1:3), Sand(C), Temp(Chg)Thick(3), Ratio(1:5), Sand(C), Temp(Chg)Thick(3), Ratio(1:3), Sand(T), Temp(Chg)Thick(3), Ratio(1:5), Sand(T), Temp(Chg)Thick(1.5), Ratio(1:3), Sand(C), Temp(Chg)Thick(1.5), Ratio(1:5), Sand(C), Temp(Chg)Thick(1.5), Ratio(1:3), Sand(T), Temp(Chg)Thick(1.5), Ratio(1:5), Sand(T), Temp(Chg)Thick(1.5): cement thickness: 1.5 cm
Ratio(1:5): cement-to-sand ratio: 1:5
Sand(C): Chinese sandTemp(Chg): Changing temperature

Table 4
Type 3 test results.
No.

Area (cm2)

1
2
3

25
25
25

4.

Max. pullout
load (kN)
2.8
3.1
2.7

Pullout resistancestrength (kgf/cm2)
11.4
12.6
11.0

Notes
Thick(1.5), Ratio(1:5), Sand(C), Temp(Chg)Thick(1.5), Ratio(1:3), Sand(T), Temp(Chg)Thick(1.5), Ratio(1:5), Sand(T), Temp(Chg)

Discussion

The average house age in Taiwan is as high as 29.53 years. Owing to earthquakes andtemperature difference, external wall tiles fall out and people are injured. In this paper, we
discuss the causes of the detachment of external wall tiles and produce test samples throughdifferent materials, ratios, weather conditions, and so forth to obtain the tensile strength undereach combination. In this study, polymer resin was added to the adhesive material to improve
the adhesion between the tile and the structure to solve the fallout problem of external wall tiles.

5.

Conclusion

In this study, different materials and methods, such as sand sources, component ratios, andweather factors, were examined to explore the causes of debonding in the interfaces joining
cement mortar layers and concrete specimens. The following conclusions were drawn:1080

Sensors and Materials, Vol. 31, No. 3 (2019)

A. Material ratio control
Most construction workers will follow the stipulated component ratio standards whenmixing cement mortars; however, a few of them will increase the sand content. Therefore,
onsite engineers, supervisors, and quality control personnel should pay close attention to
the amount of all cement mortar-related materials used and ensure that cement mortars are
stirred evenly to prevent unfavorable operations due to reduced cement mortar compressive
strength.
B. Effects of various material factors on tensile strength(a) Chinese sand showed a higher compressive strength in the early stage, whereas
Taiwanese sand demonstrated a superior overall compressive strength in the later stage.
(b) A sufficient cement mortar plastering thickness yields a superior tensile strength,
whereas an insufficient cement mortar plastering thickness creates a poor tensile strength.
Thus, construction workers must be prevented from using insufficient quantities of cement
mortar in an attempt to reduce cost.
(c) Cement mortar specimens that crack due to unfavorable weather conditions experience
severe deterioration in tensile strength. Accordingly, construction workers should implement
appropriate water control and ensure that construction walls are effectively shielded fromstrong sunlight and wind.
(d) Moderate quantities of additives (e.g., the polymer resins used in this study) can improve
the tensile properties of cement mortars and ensure that the tiles are affixed appropriately
and pedestrians are safe from tile falling.
C. Future research directions
This study only tested the compressive and tensile strengths of cement mortars; futurestudies may attempt to investigate the shear strengths of cement mortars.

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About the Authors
Wei-Ling Hsu received his Ph.D. degree in 2014 from the Department ofCivil Engineering and his Master’s degree in architecture in 2009 from Chung
Hua University in Taiwan. From 2009 to 2017, he served as an adjunctassistant professor at Chung Hua University and Minghsin University of
Science and Technology. He is currently serving at the Huaian Key
Laboratory of Geographic Information Technology and Applications, Schoolof Urban and Environmental Science, Huaiyin Normal University, China. His
research expertise includes the application of satellites and unmanned aerial
vehicles in ground-level environmental monitoring, urban traffic, urban andrural planning, and the incorporation of data analysis in fuzzy multiple
criteria decision making for cities and environments.
Chen-Chung Liu received his B.S. and M.S. degrees from Chung Hua
University Taiwan, in 2014 and 2016, respectively. He has been a Ph.D.
student in Chung Hua University, Taiwan since 2016. His research interests
are in reducing working hours, extending building life, and environmental
protection.

Yan-Chyuan Shiau received his B.S. degree from National Taiwan Instituteof Technology, Taiwan, in 1980 and his M.S. and Ph.D. degrees from Texas
A&M University, U.S.A., in 1988 and 1992, respectively. From 2000 to 2012,he was an associate professor at Chung Hua University, Taiwan. Since 2013,
he has been a professor at Chung Hua University, Taiwan. His researchinterests are in ICT, IoT, and smart home.

Chao-Lung Wang received his B.S. degree from Nan Kai University ofTechnology, Taiwan, in 2004. He received his M.S. degree from Chung Hua
University, Taiwan, in 2017. He is currently a site manager in Guan-Jou
Construction Company. His research interests are in constr uction
management and project administration.

Wen-Chin Lin received his M.S. and Ph.D. degrees from the University of
Minnesota, U.S.A., in 1990 and 1996, respectively. He has been an associate
professor at Chung Hua University, Taiwan since 1996. His research interests
are in urban and building disaster prevention, environmental impact
assessment, building energy conservation, and rainwater utilization.