Inspection of the exposed concrete façades of Vilanova Artigas, modern Brazilian heritage building with 50 years of service life

_________________________________________________________________________________________
a
Master, Architecture, Institute for Technological Research - IPT, São Paulo, SP, Brazil
b
PHD, Civil Engineering, Faculdade de Arquitetura e Urbanismo - FAU São Paulo, SP, Brazil
c
Master, Architecture, Instituto Federal São Paulo - IFSP, São Paulo, SP, Brazil
d
PHD, Physic - IPT
ICC INTERCORR WCO 2021_102
Copyright 2021, ICC & ABRACO
The work presented during 21st
INTERNATIONAL CORROSION CONGRESS & 8th
INTERNATIONAL
CORROSION MEETING in the month of July of 2021.
The information and opinions contained in this work are of the exclusive right of the author(s).
Inspection of the exposed concrete façades of Vilanova Artigas, modern Brazilian
heritage building with 50 years of service life
Adriana de Araujoa
, Claudia de Andrade Oliveirab
, Tatiana R. da Silva Simãoc
, Zehbour Panossiand
Abstract
The aim of the study is to assess the current condition of the exposed concrete in the outer
façades of the Vilanova Artigas building, one of the most important Brazilian modern
architectural heritage which has recently completed 50 years of service life. The analysis on
the effectiveness of previews interventions, environmental aggressiveness and local
inspections has provided qualified information for conduct physical, chemical and
electrochemical tests. The results indicated that the concrete surface is naturally porous and
irregular and also fragmented by the presence of patch repairs considered to be flawed.
Reinforcement cover is variable and susceptible to corrosion, induced by carbonation,
confirmed in some regions by electrochemical measurements. New intervention and
complementary studies were proposed, considering the importance of preserving the original
aspect of the exposed concrete and the mitigation of the ongoing corrosion.
Keywords: heritage conservation; exposed concrete; carbonation; corrosion; electrochemical
measurements.
Introduction
Samples of the Brazilian heritage in exposed reinforced concrete, built in the second half of
the 20th
century, have been shown pathological manifestations affecting its structural safety
and functionality. The lack of systemic studies on the main degradation mechanism that affect
them, in addition to the lack of understanding of the performance of these buildings, has led to
a series of unsuccessful interventions that de-characterize the architectural surfaces to be
preserved.
The degradation is predominantly the result of the corrosion process of reinforcement, often
due to the reduction of the pH in carbonated concrete, which occurs mainly in structures of
large urban centers such as the city of São Paulo, where a significant part of the examples of
Brazilian heritage of Modern Architecture is concentrated. Corrosion of reinforcement is one
of the main factors in reducing the service life of exposed reinforced concrete structures in
general and has been extensively investigated in recent decades. Despite the scientific and
technological mastery of the mechanisms of corrosion, there are few reports of studies, carried

- 2 -
out in situ, for buildings with 50 years of service, which allow a correct diagnosis and
prognosis for the rehabilitation of cultural heritage.
In this context, the objective of the present study was to present part of the results of research
[1] focused on the documentation, survey and analysis of the current condition of Vilanova
Artigas building´s fabric. The analysis on the effectiveness of past interventions,
environmental aggressiveness and local inspections has provided qualified information for
conduct physical, chemical and electrochemical tests. As the main results, it stands out that
the surfaces of façades are naturally porous, irregular, with concrete segregation and corrosion
product stains; 24 % of the concrete was replaced with localized mortar repairs. The
reinforcement cover ranged from 8 to 33 mm. In repairs areas, the average carbonation depth
ranged from 3 mm to 29 mm, in concrete, it ranged from 15 mm to 30 mm. The visual
examination of the reinforced under the newly fractured repairs showed its active state of
corrosion and also the occurrence of failures in carrying out the repairs. Corrosion potential
maps, with equipotential lines drawn at 50 mV intervals, indicated a concentration of lines
with a variation equal to or greater than 150 mV. The rough surface of the exposed concrete,
the low cover to the depassivated reinforcement and the active corrosion state emphasize the
need for monitoring the façades and the urgency of implementing a preventive maintenance
plan. Therefore, intervention for new repair intervention and complementary studies were
proposed.
Documentation and History
Vilanova Artigas building was built from the end of 1966 to early 1969, at Universidade de
São Paulo (USP) in the metropolitan region of the city of São Paulo. It has 18,600 m2
of built
area distributed in a set of eight floors. The major constructive material is cast-in-place
exposed reinforced concrete. The outer façades, the focus of this study, have modular patterns
of the boards and wood grain texture imprinted on the concrete surface and the pyramidal
outer pillars.
Figure 1a shows the building placement (rectangular block with plan measures of 110.20 m x
66.20 m). Figure 1b shows the partial view of the main outer façade, being seeing some
repairs commented above. The façades are identified according to their orientation. The main
SW (Southwest) façade and the NE (Northeast) façade have a length of 110.20 m; NW
(Northwest) and SE (Southeast) façades, 66.20 m. The walls’ height is 8.15 m, except for the
NE wall, which height is 7.25 m. The thickness of the concrete façade is 200 mm. The
analysis of the available original project indicates cracking control reinforcement with 8 mm
diameter, arranged in orthogonal mesh with an inter-bar spacing of 100 mm or 200 mm, and
10 mm concrete cover. Based on the mixture proportion reconstitution, it was concluded that ,
the average consumption of cement was about 400 kg/m3
and water/cement ratio of 0.50,
consistent whit the values adopted at the building construction time.
There are no records of any preventive maintenance performed on the façades within the four
decades that succeed its inauguration. There are punctual records of repair in 1981 (Pillar P3,
NE façade) and 2000 (Column P48, SW façade). From 2009 to 2010, a water repellent was
applied to inhibit the rain-water penetration. Signs of concrete deterioration by reinforcement
corrosion were reported in 1999. In 2004, Simões [2] performed a visual inspection of the
building and identified several regions of the façades with disaggregation, characterized by

- 3 -
detachment of the concrete cover and the exposure of the corroded reinforcement steel. In
November 2012, an extensive intervention campaign to repair the outer surface of the façades
was initiated as well as in the roof and interior areas of the building. The technical
specification for the execution of the patch repairs was done using industrialized cement-
based mortar modified with the addition of polymers and fibers. The campaign was completed
at the beginning of 2015, with all the surfaces of the concrete being protected by water silane-
siloxane repellent. Figure 2 shows the aspect of the exposed concrete surface of the façades at
the time of the intervention campaign.
(a) (b)
Figure 1 - (a) Building placement with direction of Northeast (NE), Southeast (SE), Southwest
(SO) and Northwest (NO) façades; (b) Partial view of the main façade (SW) in 2021, showing
repairs from intervention carried out in 2012-2015.
(a) (b)
Figure 2 - (a) Partial view of NE façade; (b) Disaggregation and exposure of corroded
reinforcement steel before the intervention in 2012-2015.
According to the previous study on atmospheric corrosivity [3], the building surroundings can
be classified as an urban environment, with a moderate concentration of pollutants. This
environment is defined by ABNT NBR 6118:2014 [4] standard as Class II, moderate
aggressiveness for reinforced concrete structures. The monitoring of the São Paulo
atmospheric air between 2006 and 2017 [5] showed the gradual decrease of the atmospheric
pollutant concentration. The carbon dioxide (CO2) was decreased significantly after a strong
trend of the gradual increase and as well as the sulfur dioxide (SO2), typical gas of industrial
and vehicle emission environments. The atmospheric concentration of SO2 in the metropolitan
region of São Paulo reduced from 16 µg/m3
in 2000 to 3 µg/m3
in 2017 [5].

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The climate in São Paulo state, with tropical characteristics, favors the development of a
corrosion process on concrete structures, as it provides conditions for frequent humidification
of the concrete, reducing its resistance to the flow of the current corrosion. The humidification
condition was verified by the total rainfall in 2017 registered in amounting to 1648.8 mm,
totalizing 187 rainy days, 16.7 % above the average value from previous period registers. The
highest temperature registered in 2017 was 36.1 °C (October) and the lowest one was 5.6 °C
(June). The annual average relative humidity (RH) in 2017 in the USP meteorological station
was 79.5 % RH, slightly above the average value from previous period (81.2 % RH) [6].
Methodology
A preliminary visual inspection (naked eye) was carried out along the whole extension of the
outer façades combined with a review of documents containing results of characterization
tests of the repair areas and of the original concrete. Next, a detailed inspection, using an
articulated lifting platform, was conducted in pré-selected areas on the four façades, including
physical, chemical and electrochemical field tests. They are made in January-February 2017
[7], at the time when the building turned 49 years old.
The selected areas were delimited with a reference grid drawn (about 15 cm x 15 cm
intervals) on the concrete surface. First, a visual examination (naked eye) of the concrete
surface was done and a delamination survey using a geologist’s hammer. A visual
examination of the reinforcement was also made to evaluate the passive or active corrosion
condition. Legal restrictions limited the field activities, the concrete fractured was only done
to expose the rebar in some repair areas. The diameter of the exposed rebar was measured
after mechanical cleaning for the removal of the major part of corrosion products. The
carbonation depth was measured by using the indicator solution of phenolphthalein [8].
Based on the reference grid, the surface moisture content was determined (at 30 mm depth)
using Moist 210B equipment which sends and receives microwaves in the frequency range
from 300 MHz to 300 GHz. Following that, the corrosion potential (Ecorr) of the
reinforcement was determined. Finally, the corrosion rate (icorr) was determined in some
areas, over the rebar position. These electrochemical measurements were carried out with
CorrMap equipment using an Ag/AgCl/KCl 3 mol/L reference electrode - EPCP (209 mV vs.
standard hydrogen electrode), adopting a procedure similar to that used in Araujo et al. [9].
To minimize the interference of the water repellent (applied in 2015), the concrete was
strongly sanded, followed by moistening by tap water sprayed in the concrete for 45 minutes.
Results and discussion
The preliminary visual inspection highlighted the irregularity of the concrete surface and the
presence of several concrete segregation regions, air voids and small areas of corrosion
product stains (corrosion spots) along the façades. The segregation was present mostly along
the printed joint lines of wooden planks (form element for cast-in-place concrete) and the
construction joints. The natural design lines and knots of wood are also printed on the
concrete surface of the façades. Figure 3 shows the original aspect of the concrete surface.
This aspect favors the deposition of particulate material, the penetration of water and the

- 5 -
aggressive agents which can be evidenced by dirt stains and stains of steel corrosion products
present throughout the facades’ extension.
(a) (b)
Figure 3 - (a) Joints lines of wooden planks and its natural design lines and knots printed in the
concrete surface; (b) Detail of regions with concrete segregation, air voids and corrosion spots.
A total area of 727 m2
of patch repairs was estimated which is equivalent to the replacement
of approximately 24 % of the original concrete (3071 m2
). The NE façade had the greatest
percentage of patch repairs (333 m2
), followed by the SW (159 m2
) and the SE (141 m2
)
façades. Although the visual heterogeneity of the concrete is a building characteristic since its
inauguration, the repaired areas cause a severe interference in the external aspect of the
building in terms of texture, chromaticity and brightness. Concrete cover measurements
showed a large variation in all façades, with the predominance of values less than 30 mm
defined in ABNT NBR 6118 [4] for a moderate aggressive environment. Figure 4 shows the
results of cover depth measurements.
Figure 4 - Cover depth measured on the façades.
In the selected areas, the visual examination also revealed the presence of some cracks on the
concrete surface and on the repair surface. In the inspected areas, the hollow sound was
detected which indicates possible corrosion-damaged areas without any signs of damages on
the surface. The fracture at some corrosion stain areas showed that the stains were originated

- 6 -
from steel pins or bars probably used for fastening the concrete form elements. Table 1 [7]
shows the results obtained in the evaluation of some newly exposed reinforcements at repair
areas of the façades.
Table 1. Results of inspection of the newly exposed reinforcement at repair areas of the façades
Description
SW NW RE SE
Repair
1
Repair
2
Repair
3
Repair
1
Repair
2
Repair
1
Repair
2
Repair
1
Repair
2
Reinforcement
Cover
(mm)
Individual
value
29 30 33 14 15 11 12 7 20
29 30 33 15 15 8 12 8 20
29 30 33 17 15 10 12 8 20
Average 29 30 33 15 15 10 12 8 20
Surface color
Brown/
orange
Black/
orange
Brown/
black /
orange
Gray /
orange
Brown/
orange
Gray /
orange
Brown/
orange
Gray /
orange
Gray /
orange
Electrochemic
al state
assigned
Active Active Active Active Active Active Active Active Active
Carbonation
depth
(mm)
Repair
mortar
Individual
value
16 3 30 4 5 3 15 5 9
8 3 34 7 5 15 15 7 10
7 3 24 5 3 10 12 5 8
4 - 27 4 8 7 11 8 8
11 - 28 - 6 - - 10 7
Average 9 3 29 5 5 9 13 7 8
Concrete
Individual
Value
(*)
17 34 33 16
17 (**)
22 (**)
22 (**)
15 (**)
> 26 (***)
15 38 34 19
22 17 26 11
14 32 25 25
Average 17 30 30 18 17 22 22 15 -
(*)
Depth of concrete analyzed beneath the mortar; (**)
Single measurement; (***)
Carbonation front not detected until
26 mm of scarification.
In Table 1, the cover, after the fracturing of the repair, ranged from 8 mm to 33 mm. These
values are compatible with the intervals of the previous survey (Figure 4). In most of the
repairs inspected, the visual examination of newly exposed reinforcement sections indicated
an active corrosion state, checked by the presence of stains with typical colors of steel
corrosion products. The corrosion was induced by the carbonation, although its front was
variable (ranged from 3 mm to 29 mm in the mortar and from 15 mm to 30 mm in the
concrete). These results suggest that the carbonation depth in the façades already reaches
approximately 20 mm. Thus, reinforcement sections with a cover less than 20 mm were
probably in an active corrosion process caused by the pH reduction.
Figure 5a shows an exposed corroded reinforcement in Repair 3 of the SW façade (Table 1).
The reinforcement was not totally surrounded by the mortar in some repair, as showed in
Figure 5a. This is an indication of an execution fail which was performed without following
conventional procedures. The only reinforcement section completely surrounded by mortar
was the one exposed in Repair 2 of the SE façade. However, the mortar of this repair
presented cracks, an anomaly which favors the ingress of aggressive agents and, thus, the
reinforcement corrosion. In Figure 5b, we can observe the carbonation front of the mortar
and of the underlying carbonated concrete.

- 7 -
(a) (b)
Figure 5 - (a) Repair 3 of SW façade and (b) Repair 2 of NW façade.
The concrete moisture was no significant, being the highest ranges from 6 % to 7 % on NW
façade (Figure 6a) and 4 % to 6 % on SW façade (Figure 6b). These measurements showed
that there are not differences between the concrete moisture content and the repair moisture
content and neither any correlation of the moisture content maps vs. corrosion potential maps
shown in Figures 6c and Figures 6d. In both maps, there are repair regions with significant
potential-gradient variation, close to 150 mV vs EPCP [9; 10], which indicates them as the
most subject to corrosion. The subsequent fracture of the repair in the grid areas confirmed
the active state of corrosion of the rebars (Table 1). In Figure 6c and Figure 6d, it is also
possible to observe positive potential values, corroborating with results already obtained in
other structures with carbonated concrete and presented by Elsener et al. [11]. Experiences
show that a comprehensive assessment of the risk of corrosion induced by carbonation of
concrete is fundamental.
Most of the values achieved for the corrosion rate were greater than 1.0 µA/cm2
(section loss
≥ 10 µm/year), indicating severe corrosion [12]. However, it must be considered that values
above 1.0 µA/cm2
are typical of concrete exposed to relative humidity (RH) above 90 %,
which is a condition not verified locally, where the average value from time-series is 81.2 %.
Considering the local RH between 70 % and 90 %, the reinforcement corrosion rate must vary
and may increase significantly only in periods of high relative humidity content or intense and
frequent rainfall.
Mortar
Concrete
Corroded
reinforcement
with accumulate
products in the
interface
Mortar
Concrete
Corroded
reinforcement
Mortar

- 8 -
(a) (b)
(c) (d)
Figure 6 - Moisture content map (%) and corrosion potential map (EPCP electrode, mV) in inspected
areas: (a)(c) on NW façade and (b)(d) on SW façade.
Result analysis
The previews interventions, local conditions, environmental aggressiveness and preliminary
inspection composed the reference basis for result analysis and were essential for deepening
the understanding of the structure performance. Among the techniques, the corrosion potential
mapping can be highlighted. This technique together with reinforcement inspections of
exposed areas evidenced the active corrosion on the rebars. In these areas, it was found that
failures in carrying out repairs for the restoring the integrity of reinforced concrete. They also
added significant variations to the surfaces in terms of texture, chromaticity and brightness of
the exposed concrete, which is inadequate in restoration intervention in a heritage building.
Onsite measurements suggest that the carbonation depth is equal or greater than the concrete
cover, and considering the corrosion history of the building, the current condition fits within
the propagation period, according to Tuuti [13] model. Within this period, the extension of the
residual service life depends on the corrosion rate and its consequences over time. The
corrosion rate is controlled by water and oxygen availability on the reinforcement surface.
Whereas the corrosion rate in carbonated concrete is ruled by the electric resistivity of
concrete, for the structure in question, subject to an intermittent period of wetting, the
moisture content of concrete is the prevailing control parameter of its electric resistivity.
By considering that the active corrosion state of the reinforcement, the environmental
condition and the characteristics of the outer façades investigated, the conservation plan shall
consider a systemic approach focused on the three principles of BSI EN 1504-9 [14] (1)
preservation or restoration of passivity; (2) control of the anodic area, and (3) protection
against penetration /control of humidity.

- 9 -
The first principle is related to the identification of patch repairs that should be redone due to
onsite conditions (carbonation front and active corrosion state), as well as the new repairs,
especially in zones with corrosion stain and hollow sound. The system that combines
industrialized mortar (corrosion inhibiting admixture addition) and anti-corrosion primer
applied on the exposed reinforcement is the proper option. But in this specific case, it would
be beneficial a new approach for the mixed design of repair mortars together in association
with the manufacturers interested in supplying a product custom-made aiming at meeting the
aesthetic requirements [1;7].
The second principle guides the general treatment of the façade surfaces with impregnation of
outer surfaces with migration corrosion inhibitor, compatible with the one adopted in the
repair system. Impregnation shall be made after removal of the residual water repellent. The
application of the corrosion inhibiting agent has the purpose of restricting the natural
electrochemical incompatibility between the repair mortar and the original carbonated
concrete. As the efficiency of the corrosion migration inhibitor depends on the final
concentration of the product around the reinforcement, previous studies are necessary,
considering the assessment of the penetration depth in aged carbonated concrete [1;7].
To meet the third principle, protecting the concrete surface with a high-performance silane-
based water repellent (high solids concentration) was considered the best option to prevent
corrosion or reduce the corrosion rate by controlling the content of concrete moisture. The
method of application of the water repellent and the number of layers must be supported by
specific studies, considering that the impregnation does not offer protection against the
penetration of gases and can contribute to the advancement of the carbonation front. To
minimize the penetration of gases and also the water-repellent effect, we have the option of
applying an additional solution based on alkaline silicate to increase resistance to the
penetration of water on the surface [1;7].
Conclusions
The present paper presented the results of inspections of the outer façades of Vilanova Artigas
building. Since it is an architectural heritage, destructive tests were restricted to predefined
areas, approved by the advisory councils for historic preservation. The visual inspection of the
concrete surfaces evidenced a typical aspect of exposed concrete structures produced in the
Modern Movement, such as surface air voids, segregation and small and variable concrete
cover of the reinforcement. These characteristics associated with the lack of efficient periodic
maintenance were determinants for the establishment of the reinforced corrosion. In the
fractured repaired areas, we observed that the carbonation depth was significant in this mortar.
The corrosion potential map presented significant potential-variation values, indicating the
active corrosion state of the reinforcement. Under the surface intense moistened condition, the
corrosion rate of the reinforcement was high.
The chronological milestone of 50-year service life, completed in 2019, without significant
damage to the structural safety and functionality, provides evidence that the performance of
the concrete/reinforcement system of the building façades under study is acceptable.
However, the rough surface and segregation of the concrete, the low concrete cover to

- 10 -
depassivated reinforcement and the verified active corrosion state of the reinforcement point
out the need for monitoring the façades and the urgency of implementing a preventive
maintenance plan, along with a conservation project in order to preserve the heritage values of
the building.
Bibliographical references
1. M. L. B. Pinheiro et al., “Subsidies for a Conservation Management Plan: Vilanova Artigas
Building”. USP (2017). Available: https://www.getty.edu/foundation/initiatives/current/
keeping _it modern/reportlibrary/Vilanova_artigas.html.
2. J. R. L. Simões, “Patologias – origens e reflexos no desempenho técnico-construtivo de
edifícios: análise das origens das patologias e seus reflexos no desempenho técnico-
construtivo de edifícios universitários da CUASO-USP/SP utilizando-se de edifícios da ISO-
6241 e procedimentos da APU - avaliação pós-uso”. Ph.D. dissertation, Fac. Arquit. Urban.,
Univ. (2004).
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Desenvolvimento Econômico do Estado de São Paulo, São Paulo: (1999) 130 pp.
4. Associação Brasileira de Normas Técnicas. NBR 6118: Projeto de Estruturas de Concreto –
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5. Companhia Ambiental do Estado de São Paulo, “Qualidade do ar no estado de São Paulo
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/28/2018/05/relatorio-qualidade-ar-2017.pdf.
6. Universidade de São Paulo. Instituto de Astronomia Geofísica e Ciências Atmosféricas,
“Boletim climatológico anual da estação meteorológica do IAG/USP”. IAG: (2017).
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repair of concrete structures - test methods - determination of carbonation depth in hardened
concrete by the phenolphthalein method, Berlin (2007) 10 p.
9. A. Araujo et al., "Comportamento eletroquímico do aço-carbono em concreto: potencial de
eletrodo e densidade de corrente elétrica". Téchne, 247 (2017), pp 29-39.
10. Nace International, “Use of reference electrodes for atmospherically exposed reinforced
concrete structures”. (Publication 11100), Houston (2000), 11 p.
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mapping on reinforced concrete structures" Mater. Struct., 36, (2003), pp. 461–471.
12. C. Andrade and C. Alonso. "RILEM TC 154-EMC: Test methods for on-site corrosion
rate measurement of steel reinforcement in concrete by means of the polarization resistance
method". Mater. Struct., 37 (2004), pp. 623-643
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Institute (1982) 469 p.
14. British Standards Institution. BS EN 1504-9: Products and Systems for the Protection and
Repair of Concrete Structures - Part 9: General Principles for the Use of Products and
Systems. (2008), 32 p.

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