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applied
sciences
Article
Sampietrini Stone Pavements: Distress Analysis
Using Pavement Condition Index Method
Pablo Zoccali, Giuseppe Loprencipe * and Andrea Galoni
Department of Civil, Constructional and Environmental Engineering, Sapienza University of Rome,
Via Eudossiana 18, 00184 Rome, Italy; pablo.zoccali@uniroma1.it (P.Z.);
galoni.1395156@studenti.uniroma1.it (A.G.)
*Correspondence: giuseppe.loprencipe@uniroma1.it; Tel.: +39-064-458-5112
Academic Editor: Zhanping You
Received: 1 June 2017; Accepted: 27 June 2017; Published: 29 June 2017
Abstract:
In several Italian cities, it is possible to find historical pavements such as the Sampietrini
pavements, which are mainly located in the center of the city of Rome. The Sampietrini pavement is
a particular road surface paved in natural stone with irregular sharp elements that are assembled
by hand with the evident not plan effect. Because of their peculiarities, they are not suitable for
streets where high speed is allowed. In many cases, high vibration and noise levels due to road traffic
traveling on Sampietrini pavements are caused by inadequate maintenance, which is also affected
by the absence of specific evaluation criteria regarding surface conditions and performances of
Sampietrini pavements. It is not possible, in fact, to adopt common approaches developed to be used
for flexible and rigid pavements, because they present completely different features and distresses.
In this paper, to overpass this problem, a new evaluation criterion based on Pavement Condition
Index (PCI) method established for block pavements is proposed. Furthermore, to fully characterize
this kind of pavements, other analyses, i.e., International Roughness Index (IRI) and comfort level
evaluation based on ISO 2631 standard, were also carried out. The results showed a good correlation
between PCI and IRI approaches (R
2
= 0.82), also highlighting that new or reconstructed Sampietrini
pavements present not negligible roughness level. This aspect was also confirmed estimating the
comfort level perceived by users traveling at several speeds (
≤
50 km/h). Finally, speed related
threshold values to be adopted for PCI and IRI methods are proposed. The proposed method can
be implemented by pavement managers in a PMS ad hoc for stone block paving and thus, it can be
integrated with other equivalents methods of visual inspection based on PCI.
Keywords:
stone pavement; sampietrini; International Roughness Index; Pavement Condition Index;
road pavement distress; ISO 2631
1. Introduction
In order to guarantee the proper maintenance of a road network, it is very important to monitor
the conditions of road pavements along their service life. In this sense, the development of an adequate
Pavement Management System (PMS) is a very useful tool for road agencies, identifying appropriate
intervention thresholds and maintenance strategies for the restoration of the optimal performances, in
terms of grip, bearing and roughness levels. [1–4].
Most PMSs, actually adopted, are related to major roads and airport infrastructures [
5
] but,
nowadays, considering the lack of budget available to administrations, a general attention to the
applications of PMS to urban areas is paid [
5
–
8
]. Many PMSs include both visual and automatic
surveys in their procedure, adopting several indices for the evaluation of road pavement performances.
Among these, two of the most commonly used ones are the Pavement Condition Index (PCI) elaborated
Appl. Sci. 2017,7, 669; doi:10.3390/app7070669 www.mdpi.com/journal/applsci
Appl. Sci. 2017,7, 669 2 of 22
by Shahin [
2
] and the International Roughness Index (IRI), which was elaborated from a World Bank
study in the 1980s [
9
]. The first one provides a global assessment of pavements condition surveying
several distress categories. In particular, it was designed for the assessment of distress related to rigid
and flexible pavements [
10
], which are the most common types that can be found in a generic road
network. IRI, instead, is used worldwide as road roughness evaluation criterion and its calculation
requires the measurement of road profiles using specific devices, also known as profilometers [11].
In recent studies [
12
,
13
], the correlation between IRI and PCI was investigated, with particular
attention to urban roads. In addition, based on IRI and distresses relation, some IRI threshold values
to be used in urban areas are proposed in [14].
In urban networks, however, different kinds of pavement can be found, such as block or modular
pavements, which are defined as pavements composed of pre-formed modular pavers of brick
and concrete, which, generally, have been successfully used worldwide for low volume roads and
pedestrian areas [
15
,
16
]. Considering the peculiar characteristics of these types of pavements, it is not
possible to extend to them distresses and evenness evaluation methods designed for rigid and flexible
pavements. In particular, starting from the PCI method described in [
2
,
10
], some authors developed
specific guidelines to survey and evaluate distresses affecting block pavements [17–19].
In several Italian cities, it is possible to find historical pavements such as the Sampietrini
pavements [
20
], which share similar features with modular block pavements. This kind of pavement
is especially present in the center of Rome and, because of its peculiar characteristics, it is not
possible to apply consolidated survey methods or threshold values commonly adopted for flexible
and rigid pavements.
For this reason, a specific case of study related to the Sampietrini block pavement was performed
in this paper, modifying the PCI method related to block pavement in order to be suitable for this
kind of pavement. Furthermore, for each section the sample surface evenness evaluation was carried
out calculating the corresponding IRI value, investigating also possible correlations between the
proposed PCI method and IRI. In addition, some considerations concerning users’ comfort perception
traveling at different speeds (<50 km/h) along this type of pavement were performed using the
frequency-weighted vertical acceleration (awz) approach described in [21–23].
2. Methodology and Data
2.1. Sampietrini Pavements
In several Italian cities, it is possible to find historical pavements such as the Sampietrini
pavements, which are especially present in the center of the city of Rome. The first documented
use of Sampietrini stones in Rome was during the reign of Pope Pius V (1566–1572). The name derives
from their first use in St. Peter’s Square and later, over the next centuries, the stones were used to pave
all the main streets of Rome, providing a smoother and stronger surface for carriages than bricks. This
kind of pavement is made of beveled stones of black basalt, also simply called Sampietrini, placed one
next to the other. The shape of each block (also called sampietrino) can be approximate by a cubic or a
square-based truncated pyramid solid. Sampietrini blocks of different dimensions can be used. The
largest ones are characterized by a square head of 12 cm
×
12 cm and height of approximately 18 cm;
however, the common height is equal to 6 cm. The smallest and rare ones, which are located in specific
areas of Rome such as Navona Square, present a square head of 6 cm
×
6 cm. In Figure 1, a typical
cross section of this type of pavements is represented, while Figure 2presents the two main geometric
patterns which can generally be realized using Sampietrini blocks. The mechanical properties of
Sampietrini material are reported in Table 1and, as shown by some studies performed by Penta in
the 1950s, the performance of the Sampietrini pavements depends on the resistance of each block
but also on the tile pattern realized, which meaningfully affects the global behavior of this kind of
pavement [20].
Appl. Sci. 2017,7, 669 3 of 22
Appl. Sci. 2017, 7, 669 3 of 22
Figure 1. Typical cross section of a block pavement structure.
(a) (b)
Figure 2. Geometric patterns: (a) herringbone at 45°; (b) arc.
Table 1. Mechanical properties of basalt used for Sampietrini.
Material Property Value
Young’s modulus (GPa) 37–60
Poisson ratio (-) 0.15–0.38
Compressive resistance (MPa) 241–320
Flexural resistance (MPa) 32–75
Tensile resistance (MPa) 18–20
The main problem associated with Sampietrini blocks concerns that they get very slippery when
they are wet, being a hazard above all for two-wheeled vehicles moving in the city. In addition, due
to their irregular shape, traveling on this kind of pavement is very uncomfortable and noisy;
moreover, heavy vehicles passing on it may cause wide vibrations that can damage the surrounding
buildings, with particular attention to historical ones.
Because of their peculiarities, Sampietrini pavements are not suitable for streets where high
speed is allowed, thus, nowadays, Sampietrini were replaced in many roads of Rome but they are
still used in slow traffic areas (speed ≤ 50 km/h), such as the center of Rome such as Trastevere (Figure
3).
Although the percentage of the urban road network characterized by Sampietrini pavement is
pretty low (about 2%), it presents a whole extension equal to about 100 km, which cannot be neglected
in an appropriate and optimized PMS. Furthermore, the aforementioned pavements not only
constitute an important historic heritage of the city of Rome, but they are also located in the most
visited and prestigious areas of Rome, as can be seen in Figure 3.
Figure 1. Typical cross section of a block pavement structure.
Appl. Sci. 2017, 7, 669 3 of 22
Figure 1. Typical cross section of a block pavement structure.
(a) (b)
Figure 2. Geometric patterns: (a) herringbone at 45°; (b) arc.
Table 1. Mechanical properties of basalt used for Sampietrini.
Material Property Value
Young’s modulus (GPa) 37–60
Poisson ratio (-) 0.15–0.38
Compressive resistance (MPa) 241–320
Flexural resistance (MPa) 32–75
Tensile resistance (MPa) 18–20
The main problem associated with Sampietrini blocks concerns that they get very slippery when
they are wet, being a hazard above all for two-wheeled vehicles moving in the city. In addition, due
to their irregular shape, traveling on this kind of pavement is very uncomfortable and noisy;
moreover, heavy vehicles passing on it may cause wide vibrations that can damage the surrounding
buildings, with particular attention to historical ones.
Because of their peculiarities, Sampietrini pavements are not suitable for streets where high
speed is allowed, thus, nowadays, Sampietrini were replaced in many roads of Rome but they are
still used in slow traffic areas (speed ≤ 50 km/h), such as the center of Rome such as Trastevere (Figure
3).
Although the percentage of the urban road network characterized by Sampietrini pavement is
pretty low (about 2%), it presents a whole extension equal to about 100 km, which cannot be neglected
in an appropriate and optimized PMS. Furthermore, the aforementioned pavements not only
constitute an important historic heritage of the city of Rome, but they are also located in the most
visited and prestigious areas of Rome, as can be seen in Figure 3.
Figure 2. Geometric patterns: (a) herringbone at 45◦; (b) arc.
Table 1. Mechanical properties of basalt used for Sampietrini.
Material Property Value
Young’s modulus (GPa) 37–60
Poisson ratio (-) 0.15–0.38
Compressive resistance (MPa) 241–320
Flexural resistance (MPa) 32–75
Tensile resistance (MPa) 18–20
Sampietrini pavement presents some advantages; in fact, it does not completely cover the ground,
leaving small spaces for the water to pass through and can easily adapt to the irregularities of the
ground. Furthermore, being of volcanic basalt, Sampietrini are very strong and resistant.
The main problem associated with Sampietrini blocks concerns that they get very slippery when
they are wet, being a hazard above all for two-wheeled vehicles moving in the city. In addition, due to
their irregular shape, traveling on this kind of pavement is very uncomfortable and noisy; moreover,
heavy vehicles passing on it may cause wide vibrations that can damage the surrounding buildings,
with particular attention to historical ones.
Because of their peculiarities, Sampietrini pavements are not suitable for streets where high speed
is allowed, thus, nowadays, Sampietrini were replaced in many roads of Rome but they are still used
in slow traffic areas (speed ≤50 km/h), such as the center of Rome such as Trastevere (Figure 3).
Appl. Sci. 2017,7, 669 4 of 22
Appl. Sci. 2017, 7, 669 4 of 22
Figure 3. Extension of Sampietrini pavements (in red) within the urban road network of Rome.
In addition to the urban road network of 100 km, several other roads in Sampietrini are located
within the Lazio region and in other towns in Italy, whose extension and the accurate location is
difficult to know with sufficient precision.
The construction of this kind of pavement is very complex (Figure 4) and it requires very skilled
and specialized workers, which are very rare nowadays. In the past, in fact, the knowledge and the
know-how were handed down from father to son.
For this reason, the costs to construct Sampietrini pavements are significantly greater than the
costs required for asphalt concrete pavements. The estimated costs provided by the city of Rome [24],
in fact, indicate a cost equal to about 200 €/m
2
for Sampietrini pavement and about 50 €/m
2
for asphalt
concrete ones. This meaningful gap (ratio of 4:1) further motivates the need to pay particular attention
to identifying distresses’ type and location and selecting the appropriate maintenance actions to fix
them.
Sampietrini pavements need a lot of maintenance since the blocks are not fixed into the ground
with cement or any other bonding agent, but are simply hammered into the sandbed.
In many cases, high vibration and noise levels due to road traffic traveling on Sampietrini
pavements are caused by inadequate maintenance [25], which is also affected by the absence of
specific evaluation criteria regarding surface conditions and performances of Sampietrini pavements.
It is not possible, in fact, to adopt common approaches developed to be used for flexible and rigid
pavements, because they present completely different features and distresses.
Figure 3. Extension of Sampietrini pavements (in red) within the urban road network of Rome.
Although the percentage of the urban road network characterized by Sampietrini pavement is
pretty low (about 2%), it presents a whole extension equal to about 100 km, which cannot be neglected
in an appropriate and optimized PMS. Furthermore, the aforementioned pavements not only constitute
an important historic heritage of the city of Rome, but they are also located in the most visited and
prestigious areas of Rome, as can be seen in Figure 3.
In addition to the urban road network of 100 km, several other roads in Sampietrini are located
within the Lazio region and in other towns in Italy, whose extension and the accurate location is
difficult to know with sufficient precision.
The construction of this kind of pavement is very complex (Figure 4) and it requires very skilled
and specialized workers, which are very rare nowadays. In the past, in fact, the knowledge and the
know-how were handed down from father to son.
Appl. Sci. 2017, 7, 669 5 of 22
Figure 4. The construction phase of a block pavement structure.
In this paper, in order to overpass this problem, a new evaluation criterion based on PCI method
established for block pavements is proposed. In particular, 14 sections belonging to different low
volume roads and located in the center of the city of Rome, were analyzed according to three different
approaches: PCI, IRI and a
wz
. In Figures 5 and 6, two examples of the examined road sections are
depicted.
For all sections, having a length of 80 m and width equal to 3 m (for a total pavement area of
240 m
2
), the two alignments (right and left) were measured using a contact profilometer (i.e., Dipstick).
(a) (b)
Figure 5. Sampietrini pavement Section 01: (a) top-down; (b) street views.
(a) (b)
Figure 6. Sampietrini pavement Section 06: (a) top-down; (b) street views.
Figure 4. The construction phase of a block pavement structure.
Appl. Sci. 2017,7, 669 5 of 22
For this reason, the costs to construct Sampietrini pavements are significantly greater than the
costs required for asphalt concrete pavements. The estimated costs provided by the city of Rome [
24
],
in fact, indicate a cost equal to about 200
€
/m
2
for Sampietrini pavement and about 50
€
/m
2
for
asphalt concrete ones. This meaningful gap (ratio of 4:1) further motivates the need to pay particular
attention to identifying distresses’ type and location and selecting the appropriate maintenance actions
to fix them.
Sampietrini pavements need a lot of maintenance since the blocks are not fixed into the ground
with cement or any other bonding agent, but are simply hammered into the sandbed.
In many cases, high vibration and noise levels due to road traffic traveling on Sampietrini
pavements are caused by inadequate maintenance [
25
], which is also affected by the absence of specific
evaluation criteria regarding surface conditions and performances of Sampietrini pavements. It is not
possible, in fact, to adopt common approaches developed to be used for flexible and rigid pavements,
because they present completely different features and distresses.
In this paper, in order to overpass this problem, a new evaluation criterion based on PCI method
established for block pavements is proposed. In particular, 14 sections belonging to different low
volume roads and located in the center of the city of Rome, were analyzed according to three different
approaches: PCI, IRI and a
wz
. In Figures 5and 6, two examples of the examined road sections
are depicted.
Appl. Sci. 2017, 7, 669 5 of 22
Figure 4. The construction phase of a block pavement structure.
In this paper, in order to overpass this problem, a new evaluation criterion based on PCI method
established for block pavements is proposed. In particular, 14 sections belonging to different low
volume roads and located in the center of the city of Rome, were analyzed according to three different
approaches: PCI, IRI and a
wz
. In Figures 5 and 6, two examples of the examined road sections are
depicted.
For all sections, having a length of 80 m and width equal to 3 m (for a total pavement area of
240 m
2
), the two alignments (right and left) were measured using a contact profilometer (i.e., Dipstick).
(a) (b)
Figure 5. Sampietrini pavement Section 01: (a) top-down; (b) street views.
(a) (b)
Figure 6. Sampietrini pavement Section 06: (a) top-down; (b) street views.
Figure 5. Sampietrini pavement Section 01: (a) top-down; (b) street views.
Appl. Sci. 2017, 7, 669 5 of 22
Figure 4. The construction phase of a block pavement structure.
In this paper, in order to overpass this problem, a new evaluation criterion based on PCI method
established for block pavements is proposed. In particular, 14 sections belonging to different low
volume roads and located in the center of the city of Rome, were analyzed according to three different
approaches: PCI, IRI and a
wz
. In Figures 5 and 6, two examples of the examined road sections are
depicted.
For all sections, having a length of 80 m and width equal to 3 m (for a total pavement area of
240 m
2
), the two alignments (right and left) were measured using a contact profilometer (i.e., Dipstick).
(a) (b)
Figure 5. Sampietrini pavement Section 01: (a) top-down; (b) street views.
(a) (b)
Figure 6. Sampietrini pavement Section 06: (a) top-down; (b) street views.
Figure 6. Sampietrini pavement Section 06: (a) top-down; (b) street views.
For all sections, having a length of 80 m and width equal to 3 m (for a total pavement area of
240 m
2
), the two alignments (right and left) were measured using a contact profilometer (i.e., Dipstick).
Appl. Sci. 2017,7, 669 6 of 22
2.2. Performed Analyses
In order to fully characterized Sampietrini stones pavements, three different approaches were
considered: PCI for global distresses assessment, IRI for evenness evaluation and a
wz
for ride quality
estimation. The aim of the analyses performed using the two latter indices, is trying to define (or
to estimate) the roughness level and the ride comfort related to new or reconstructed Sampietrini
pavements. In the following sections, a brief description of each road evaluation method applied to
the Sampietrini pavements is provided.
2.2.1. Pavement Condition Index (PCI)
The PCI is a numerical indicator, based on the inspection of different distress types affecting
road pavement surface. For each distress, the corresponding severity and quantity are identified and
recorded on specific survey data sheet reported in [
10
]. PCI rating scale (Table 2) varies from 0 (failed
pavement) to 100 (perfect condition).
Table 2. Standard PCI rating scale.
PCI Verbal Rating
86–100 Good
71–85 Satisfactory
56–70 Fair
41–55 Poor
26–40 Very Poor
11–25 Serious
0–10 Failed
As already stated, this method was developed to be used for rigid and flexible pavements [
2
,
10
],
even though some authors have proposed guidelines in order to apply PCI approach to concrete block
pavements [18,19].
Considering the similarities between Sampietrini and concrete block pavements (i.e., they are
both modular pavement, and each block presents homogeneous mechanical characteristics), a specific
distresses catalogue for Sampietrini pavements was established starting from the one reported in [
18
].
In particular, threshold values related to the three severities (low, medium and high) were modified,
taking into account the specific shape size of a single block of Sampietrini pavements.
Therefore, the distress catalogue proposed for Sampietrini pavements includes all the distresses
(Table 3) described in Appendix A, whose descriptions are mostly taken from [
18
]. Compared to distress
catalogue presented in [
18
], horizontal creep distress (distress identified by 107) can be considered
negligible for Sampietrini pavements.
Table 3. List of distresses proposed for Sampietrini pavements.
Distress ID. Description
101 Damaged Sampietrini
102 Depressions
103 Edge restraint
104 Excessive joint width
105 Faulting
106 Heave
108 Joint sand loss/pumping
109 Missing Sampietrini
110 Patching
111 Rutting
Appl. Sci. 2017,7, 669 7 of 22
2.2.2. International Roughness Index (IRI)
The International Roughness Index (IRI) is the worldwide used road roughness evaluation
indicator, elaborated from a World Bank study in the 1980s. It is based on a mathematical model called
quarter-car and developed in order to assess the ride quality on road pavements. The assessment is
performed by a simulation model, calculating the suspension motion on a single profile and dividing
the sum by the distance traveled according to Equation (1):
IRI =1
l
l
v
Z
0
.
zs−.
zu
dt (1)
where lis the length of the profile in km, vis the simulated speed equal to 80 km/h,
.
zs
is the time
derivative of vertical displacement of the sprung mass in meters and
.
zu
is the time derivative of vertical
displacement of the unsprung mass in meters. The result is the IRI value and it is expressed in slope
units (e.g., m/km or mm/m).
In the present work, the IRI calculation was performed by means of a Matlab
©
code, where the
algorithm provided by ASTM E1926 [
26
] standard is implemented. For each analyzed section, two
alignments (right and left) were measured, calculating the corresponding IRI value for both of them.
Finally, the mean value characterizing the whole section was obtained using Equation (2):
IRIsection =I RIle f t +IRIright
2(2)
2.2.3. Frequency-Weighted Vertical Acceleration (awz)
In addition to IRI and PCI methods, a further analysis performed to fully characterize Sampietrini
pavements was the ride quality evaluation carried out adopting the frequency-weighted vertical
acceleration (a
wz
) parameter, described in [
27
]. To determine the frequency-weighted vertical
acceleration on users due to road roughness [
28
], several simulations at different speeds (10–50 km/h)
were performed using the eight degrees of freedom (d.o.f.) full car model developed by Cantisani and
Loprencipe [21] and calibrated in order to represent the behavior of a common passengers’ car.
Starting from the vertical accelerations calculated by this model traveling along the road profiles,
it is possible to determine the root mean square (RMS) accelerations through the evaluation of the
power spectral density (PSD). Acceleration PSD is then calculated in correspondence of the 23 one-third
octaves bands, representative of the frequency range of interest for the human response to vibrations
(0.5–80 Hz), as specified by ISO 2631 standard. The final value for a
wz
index is then obtained using the
following Equation (3):
awz =v
u
u
t
23
∑
i=1
(Wk,i×aiz)2(3)
where W
k,i
are the frequency weightings in one-third octaves bands for seated position, provided
by the standard, and a
iz
is the vertical root mean square (RMS) acceleration for the i-th one-third
octave band.
Then, a
wz
values can be compared with the threshold values proposed by ISO 2631 for public
transport (Table 4) to estimate the corresponding comfort level perceived by users traveling along the
examined road sections.
By means of this analysis, it is possible to estimate the maximum speed at which drivers can
transit on new or reconstructed Sampietrini pavements that cannot present a perfectly smoothed
surface. In this way, the chance of using this type of pavement for certain road categories in the urban
network is also assessed.
Appl. Sci. 2017,7, 669 8 of 22
Table 4. Comfort levels related to awz threshold values proposed by ISO 2631 for public transport.
awz Values (m/s2)Comfort Level
<0.315 Not uncomfortable
0.315–0.63 A little uncomfortable
0.5–1 Fairly uncomfortable
0.8–1.6 Uncomfortable
1.25–2.5 Very uncomfortable
>2 Extremely uncomfortable
3. Results and Discussions
PCI values calculated for the sections examined in this paper, present a good variability going
from 12 to 94, although just one section has PCI <40, corresponding to very poor pavement condition or
worst. More details about the distresses presented in each inspected section are reported in Appendix B.
As can be seen in Figure 7, a good correlation between PCI and IRI was found (R
2
= 0.82). In particular,
it can be noted that for good Sampietrini pavements (PCI > 86), IRI value varies between 6 and 8.
These values, in case of rigid or flexible pavements, might be commonly associated to damaged
pavement [11].
Appl. Sci. 2017, 7, 669 8 of 22
By means of this analysis, it is possible to estimate the maximum speed at which drivers can
transit on new or reconstructed Sampietrini pavements that cannot present a perfectly smoothed
surface. In this way, the chance of using this type of pavement for certain r oad categori es in the urban
network is also assessed.
3. Results and Discussions
PCI values calculated for the sections examined in this paper, present a good variability going
from 12 to 94, although just one section has PCI <40, corresponding to very poor pavement condition
or worst. More details about the distresses presented in each inspected section are reported in
Appendix B. As can be seen in Figure 7, a good correlation between PCI and IRI was found (R2 = 0.82).
In p arti cular, it can be noted t hat f or good Sa mpietrini pa vements (PCI > 86), IRI val ue va ries b etween
6 and 8. These values, in case of rigid or flexible pavements, might be commonly associated to
damaged pavement [11].
Figure 7. Correlation between Pavement Condition Index (PCI) and International Roughness Index
(IRI) for Sampietrini pavements.
The peculiarity of IRI range values found for Sampietrini pavements is better underlined looking
at Figure 8, where the relation between PCI and IRI for different types of pavement is depicted.
Figure 8. Correlation between PCI and IRI for a different type of pavements.
y = -5.94x + 137.12
R² = 0.82
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25
PCI
IRI (m/km)
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25
PCI
IRI (m/km)
Sampietrini - Present work
Asphalt - Arhin et al. 2015
Composite - Arhin et al. 2015
Concrete - Arhin et al. 2015
Asphalt - Park et al. 2007
Figure 7.
Correlation between Pavement Condition Index (PCI) and International Roughness Index
(IRI) for Sampietrini pavements.
The peculiarity of IRI range values found for Sampietrini pavements is better underlined looking
at Figure 8, where the relation between PCI and IRI for different types of pavement is depicted.
Appl. Sci. 2017, 7, 669 8 of 22
By means of this analysis, it is possible to estimate the maximum speed at which drivers can
transit on new or reconstructed Sampietrini pavements that cannot present a perfectly smoothed
surface. In thi s way, the chance of using this type of pavement for cer tain road categories in the urban
network is also assessed.
3. Results and Discussions
PCI values calculated for the sections examined in this paper, present a good variability going
from 12 to 94, although just one section has PCI <40, corresponding to very poor pavement condition
or worst. More details about the distresses presented in each inspected section are reported in
Appendix B. As can be seen in Figure 7, a good correlation between PCI and IRI was found (R2 = 0.82).
In p arti cular, it can be not ed th at for good Sampietr ini pavem ents (PCI > 86), IRI va lue v aries bet ween
6 and 8. These values, in case of rigid or flexible pavements, might be commonly associated to
damaged pavement [11].
Figure 7. Correlation between Pavement Condition Index (PCI) and International Roughness Index
(IRI) for Sampietrini pavements.
The peculiarity of IRI range values found for Sampietrini pavements is better underlined looking
at Figure 8, where the relation between PCI and IRI for different types of pavement is depicted.
Figure 8. Correlation between PCI and IRI for a different type of pavements.
y = -5.94x + 137.12
R² = 0.82
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25
PCI
IRI (m/km)
0
10
20
30
40
50
60
70
80
90
100
0 5 10 15 20 25
PCI
IRI (m/km)
Sampietrini - Present work
Asphalt - Arhin et al. 2015
Composite - Arhin et al. 2015
Concrete - Arhin et al. 2015
Asphalt - Park et al. 2007
Figure 8. Correlation between PCI and IRI for a different type of pavements.
Appl. Sci. 2017,7, 669 9 of 22
In particular, it can be seen that, according to the relations found by Arhin et al. [
12
], regardless of
the type of pavements, IRI values are always lower than 10 m/km, even for PCI close to 0. Considering
the relation found by Park et al. [
29
] for asphalt pavements, instead, for PCI values lower than 40
(corresponding to pavements condition from very poor to failed, see Table 2) very high values of IRI
are found.
In any case, it is clear that different IRI values must be associated to new or reconstructed
Sampietrini pavements, compared to the most common types of pavement (flexible and rigid).
Starting from this result, it was decided to evaluate the ride quality perceived by road users
traveling along Sampietrini pavements at different speeds. As already stated, taking into account
that this type of pavement is present just in urban areas, velocity range between 10 and 50 km/h was
considered. As can be seen in Figure 9, very weak correlations (R
2
= 0.44–0.70) were found between
IRI and awz values at different speeds.
Appl. Sci. 2017, 7, 669 9 of 22
In particular, it can be seen that, according to the relations found by Arhin et al. [12], regardless
of the type of pavements, IRI values are always lower than 10 m/km, even for PCI close to 0.
Considering the relati on found by Park et al. [29] for asphalt pavements, instead, for PCI values lower
than 4 0 (corresp onding to p avem ents condi tion from v ery poor to fail ed, see Table 2) v ery h igh v alues
of IRI are found.
In any case, it is clear that different IRI values must be associated to new or reconstructed
Sampietrini pavements, compared to the most common types of pavement (flexible and rigid).
Starting from this result, it was decided to evaluate the ride quality perceived by road users
traveling along Sampietrini pavements at different speeds. As already stated, taking into account that
this type of pavement is present just in urban areas, velocity range between 10 and 50 km/h was
considered. As can be seen in Figure 9, very weak correlations (R2 = 0.44–0.70) were found between
IRI and awz values at different speeds.
Figure 9. Correlation between IRI and awz at different speeds.
Similar results, in terms of correlation coefficient R2, were obtained comparing PCI and awz
approaches (Figure 10). In fact, as depicted in Figure 11, R2 values at different speeds for IRI-awz and
PCI-awz correlations are very close to each other.
Figure 10. Correlation between PCI and awz at different speeds.
y = 0.12e
0.06x
R² = 0.48
y = 0.19e
0.06x
R² = 0.59
y = 0.26e
0.07x
R² = 0.59
y = 0.30e
0.08x
R² = 0.70
y = 0.40e
0.07x
R² = 0.44
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
0.00 5.00 10.00 15.00 20.00 25.00
a
wz
(m/s
2
)
IRI (m/km)
10 km/h 20 km/h 30 km/h 40 km/h 50 km/h
y = 0.47e
-0.01x
R² = 0.56
y = 0.76e
-0.01x
R² = 0.59
y = 1.21e
-0.01x
R² = 0.56
y = 1.67e
-0.01x
R² = 0.64 y = 1.78e
-0.01x
R² = 0.32
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00
a
wz
(m/s
2
)
PCI
10 km/h 20 km/h 30 km/h 40 km/h 50 km/h
Figure 9. Correlation between IRI and awz at different speeds.
Similar results, in terms of correlation coefficient R
2
, were obtained comparing PCI and a
wz
approaches (Figure 10). In fact, as depicted in Figure 11,R
2
values at different speeds for IRI-a
wz
and
PCI-awz correlations are very close to each other.
Appl. Sci. 2017, 7, 669 9 of 22
In particular, it can be seen that, according to the relations found by Arhin et al. [12], regardless
of the type of pavements, IRI values are always lower than 10 m/km, even for PCI close to 0.
Considering the relati on found by Park et al. [29] for asphalt pavements, instead, for PCI values lower
than 4 0 (corresp onding to p avem ents condi tion from v ery poor to fail ed, see Table 2) v ery h igh v alues
of IRI are found.
In any case, it is clear that different IRI values must be associated to new or reconstructed
Sampietrini pavements, compared to the most common types of pavement (flexible and rigid).
Starting from this result, it was decided to evaluate the ride quality perceived by road users
traveling along Sampietrini pavements at different speeds. As already stated, taking into account that
this type of pavement is present just in urban areas, velocity range between 10 and 50 km/h was
considered. As can be seen in Figure 9, very weak correlations (R2 = 0.44–0.70) were found between
IRI and awz values at different speeds.
Figure 9. Correlation between IRI and awz at different speeds.
Similar results, in terms of correlation coefficient R2, were obtained comparing PCI and awz
approaches (Figure 10). In fact, as depicted in Figure 11, R2 values at different speeds for IRI-awz and
PCI-awz correlations are very close to each other.
Figure 10. Correlation between PCI and awz at different speeds.
y = 0.12e
0.06x
R² = 0.48
y = 0.19e
0.06x
R² = 0.59
y = 0.26e
0.07x
R² = 0.59
y = 0.30e
0.08x
R² = 0.70
y = 0.40e
0.07x
R² = 0.44
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
0.00 5.00 10.00 15.00 20.00 25.00
a
wz
(m/s
2
)
IRI (m/km)
10 km/h 20 km/h 30 km/h 40 km/h 50 km/h
y = 0.47e
-0.01x
R² = 0.56
y = 0.76e
-0.01x
R² = 0.59
y = 1.21e
-0.01x
R² = 0.56
y = 1.67e
-0.01x
R² = 0.64 y = 1.78e
-0.01x
R² = 0.32
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00
a
wz
(m/s
2
)
PCI
10 km/h 20 km/h 30 km/h 40 km/h 50 km/h
Figure 10. Correlation between PCI and awz at different speeds.
Appl. Sci. 2017,7, 669 10 of 22
Appl. Sci. 2017, 7, 669 10 of 22
Figure 11. Correlation coefficient R2 as function of traveling speed used for awz calculation.
Considering for example two sections having PCI >85 (corresponding to a pavement in good
condition), it is possible to evaluate the comfort level induced on road users traveling at different
velocities on new or reconstructed Sampietrini pavements. As can be seen in Figure 12, also moving
at 50 km/h (maximum legal speed allowed on Italian urban roads) the worst comfort level perceived
by drivers is equal to “fairly uncomfortable”. In the same figure, two sections characterized by PCI
values between 41 and 55 (corresponding to poor pavement condition) are also reported. In this case,
at the maximum allowable speed (i.e., 50 km/h), the comfort level was found to be very
uncomfortable. Furthermore, levels equal to fairly uncomfortable/uncomfortable are already reached
at 30 km/h.
The aforementioned results show the chance of using Sampietrini pavements on the urban road
network, allowing a little level of discomfort on users. In order to prevent an excessive decay of level
of service (in terms of comfort), it would be appropriate to adopt comfort and speed related threshold
values for IRI and PCI approaches, as also proposed in [30].
Figure 12. Estimation of ride quality on new or reconstructed Sampietrini pavements (PCI > 85).
Using the correlations previously found, for example, it is possible to determine IRI and PCI
limits, respectively, depicted in Figures 13 and 14.
0
0.2
0.4
0.6
0.8
1
0 102030405060
R
2
Simulation traveling speed (km/h)
PCI-awz IRI-awz
0
10
20
30
40
50
60
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Speed (km/h)
a
wz
(m/s
2
)
PCI=54
PCI=88
PCI=92
PCI=46
Comfortable
Little uncomfortable
Fairly uncomfortable
Uncomfortable
Very uncomfortable
Figure 11. Correlation coefficient R2as function of traveling speed used for awz calculation.
Considering for example two sections having PCI >85 (corresponding to a pavement in good
condition), it is possible to evaluate the comfort level induced on road users traveling at different
velocities on new or reconstructed Sampietrini pavements. As can be seen in Figure 12, also moving at
50 km/h (maximum legal speed allowed on Italian urban roads) the worst comfort level perceived by
drivers is equal to “fairly uncomfortable”. In the same figure, two sections characterized by PCI values
between 41 and 55 (corresponding to poor pavement condition) are also reported. In this case, at the
maximum allowable speed (i.e., 50 km/h), the comfort level was found to be very uncomfortable.
Furthermore, levels equal to fairly uncomfortable/uncomfortable are already reached at 30 km/h.
Appl. Sci. 2017, 7, 669 10 of 22
Figure 11. Correlation coefficient R2 as function of traveling speed used for awz calculation.
Considering for example two sections having PCI >85 (corresponding to a pavement in good
condition), it is possible to evaluate the comfort level induced on road users traveling at different
velocities on new or reconstructed Sampietrini pavements. As can be seen in Figure 12, also moving
at 50 km/h (maximum legal speed allowed on Italian urban roads) the worst comfort level perceived
by drivers is equal to “fairly uncomfortable”. In the same figure, two sections characterized by PCI
values between 41 and 55 (corresponding to poor pavement condition) are also reported. In this case,
at the maximum allowable speed (i.e., 50 km/h), the comfort level was found to be very
uncomfortable. Furthermore, levels equal to fairly uncomfortable/uncomfortable are already reached
at 30 km/h.
The aforementioned results show the chance of using Sampietrini pavements on the urban road
network, allowing a little level of discomfort on users. In order to prevent an excessive decay of level
of service (in terms of comfort), it would be appropriate to adopt comfort and speed related threshold
values for IRI and PCI approaches, as also proposed in [30].
Figure 12. Estimation of ride quality on new or reconstructed Sampietrini pavements (PCI > 85).
Using the correlations previously found, for example, it is possible to determine IRI and PCI
limits, respectively, depicted in Figures 13 and 14.
0
0.2
0.4
0.6
0.8
1
0 102030405060
R
2
Simulation traveling speed (km/h)
PCI-awz IRI-awz
0
10
20
30
40
50
60
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
Speed (km/h)
a
wz
(m/s
2
)
PCI=54
PCI=88
PCI=92
PCI=46
Comfortable
Little uncomfortable
Fairly uncomfortable
Uncomfortable
Very uncomfortable
Figure 12. Estimation of ride quality on new or reconstructed Sampietrini pavements (PCI > 85).
The aforementioned results show the chance of using Sampietrini pavements on the urban road
network, allowing a little level of discomfort on users. In order to prevent an excessive decay of level
of service (in terms of comfort), it would be appropriate to adopt comfort and speed related threshold
values for IRI and PCI approaches, as also proposed in [30].
Appl. Sci. 2017,7, 669 11 of 22
Using the correlations previously found, for example, it is possible to determine IRI and PCI
limits, respectively, depicted in Figures 13 and 14.
Appl. Sci. 2017, 7, 669 11 of 22
Figure 13. Speed related IRI thresholds.
Figure 14. Speed related PCI thresholds.
As already stated, weak correlations were found between the two aforementioned indices and
a
wz
. For this reason, it would be necessary to increase the sample size to better investigate these
correlations, eventually improving them.
4. Conclusions
In this paper, several road pavement evaluation methods were applied to 14 sections of historical
Sampietrini pavements: PCI, IRI, and a
wz
. In particular, starting from the PCI method established for
block pavements, specific severity threshold values for all possible distress types characterizing
Sampietrini pavements were proposed.
A good correlation factor (R
2
= 0.82) was found between PCI and IRI values calculated for the
aforementioned sections. In addition, considering that PCI values greater than 85 correspond to
pavements in excellent conditions, it was confirmed that new or reconstructed Sampietrini
pavements are characterized by not negligible roughness level (IRI = 6–8 m/km). In fact, they cannot
be used for high-speed roads (>50 km/h).
Figure 13. Speed related IRI thresholds.
Appl. Sci. 2017, 7, 669 11 of 22
Figure 13. Speed related IRI thresholds.
Figure 14. Speed related PCI thresholds.
As already stated, weak correlations were found between the two aforementioned indices and
a
wz
. For this reason, it would be necessary to increase the sample size to better investigate these
correlations, eventually improving them.
4. Conclusions
In this paper, several road pavement evaluation methods were applied to 14 sections of historical
Sampietrini pavements: PCI, IRI, and a
wz
. In particular, starting from the PCI method established for
block pavements, specific severity threshold values for all possible distress types characterizing
Sampietrini pavements were proposed.
A good correlation factor (R
2
= 0.82) was found between PCI and IRI values calculated for the
aforementioned sections. In addition, considering that PCI values greater than 85 correspond to
pavements in excellent conditions, it was confirmed that new or reconstructed Sampietrini
pavements are characterized by not negligible roughness level (IRI = 6–8 m/km). In fact, they cannot
be used for high-speed roads (>50 km/h).
Figure 14. Speed related PCI thresholds.
As already stated, weak correlations were found between the two aforementioned indices and a
wz
.
For this reason, it would be necessary to increase the sample size to better investigate these correlations,
eventually improving them.
4. Conclusions
In this paper, several road pavement evaluation methods were applied to 14 sections of historical
Sampietrini pavements: PCI, IRI, and a
wz
. In particular, starting from the PCI method established
for block pavements, specific severity threshold values for all possible distress types characterizing
Sampietrini pavements were proposed.
Appl. Sci. 2017,7, 669 12 of 22
A good correlation factor (R
2
= 0.82) was found between PCI and IRI values calculated for the
aforementioned sections. In addition, considering that PCI values greater than 85 correspond to
pavements in excellent conditions, it was confirmed that new or reconstructed Sampietrini pavements
are characterized by not negligible roughness level (IRI = 6–8 m/km). In fact, they cannot be used for
high-speed roads (>50 km/h).
For a Sampietrini pavement in good condition (PCI = 88–92, good), the values of a
wz
calculated at
velocities within the range from 10 to 50 km/h showed that, for speed equal to 40 and 50 km/h, ride
quality might be little or fairly uncomfortable. When the pavement conditions get worse (PCI = 46–54,
poor), ride comfort also decreases, arriving at a very uncomfortable level at 50 km/h.
Although weak correlations were found between PCI-a
wz
and IRI-a
wz
, to develop an appropriate
Sampietrini management system based on the ride quality perceived by road users, speed related PCI
and IRI thresholds are also proposed.
In this sense, wider and extensive in situ measurements should be performed to improve
the accuracy and the efficiency of the proposed approach for the surface conditions assessment
of Sampietrini pavements.
Acknowledgments:
All sources of funding of the study should be disclosed. Please clearly indicate grants that
you have received in support of your research work. Clearly state if you received funds for covering the costs to
publish in open access.
Author Contributions:
Giuseppe Loprencipe had the original idea. Andrea Galoni performed the pavement
inspection data of Sampietrini pavements in Rome. Giuseppe Loprencipe and Pablo Zoccali carried out the data
and results analyses of the work. Pablo Zoccali wrote the manuscript and was in charge of the overall outline and
editing of the manuscript. Andrea Galoni was involved in the revision and completion of the work. Giuseppe
Loprencipe contributed to the outline as well as to the revision, completion, and editing of the manuscript.
Conflicts of Interest: The authors declare no conflict of interest.
Abbreviations
The following abbreviations are used in this manuscript:
awz Frequency-weighted vertical acceleration
ASTM American Society of Texting and Materials
CDV Corrected Deduct Value
DV Deduct Value
IRI International Roughness Index
ISO International Organization for Standardization
PCI Pavement Condition Index
PMS Pavement Management System
PSD Power Spectral Density
RMS Root Mean Square
Appendix A. Distress Identification Catalogue for Sampietrini Pavements
This appendix includes a list of the distresses defined in the proposed distress Identification Catalogue for
Sampietrini pavements. Besides, it includes guidelines for distress identification and security level assessment
and provides recommendations to conduct the pavement survey.
The Deduct Curves for each distress and the Total Deduct Value/Corrected Deduct Value diagram used in
the PCI calculus are the same as reported in Interlocking Concrete Pavement Distress Manual [
18
] and, for this
reason, they are not reported in this paper.
In this study, new definitions of the severity levels (low, medium and high) were proposed for Sampietrini
pavement; these new definitions for each distress type are reported in the following sections.
Appendix A.1. Damaged Sampietrini
Damaged Sampietrini describes the condition of the paver blocks. Block damage would include paver
distresses such as a chip, crack, or spalls. This kind of distress would be indicative of load related damage, such as
inadequate support causing shear breakage, etc.
Damaged pavers are measured in square meters of surface area. Random individual cracked pavers are not
counted. The severity is evaluated by level of distress (Figure A1), according to indications reported in Table A1.
Appl. Sci. 2017,7, 669 13 of 22
Appl. Sci. 2017, 7, 669 13 of 22
(a) (b) (c)
Figure A1. Damaged Sampietrini severity: (a) low; (b) medium; (c) high.
Table A1. Severity level of damaged Sampietrini distress.
Severity Level Item
Low Individual cracks, separations or alterations
Medium Advanced cracking, separations or alterations
High Blocks are in multiple pieces or are disintegrated
Appendix A.2. Depressions
Depressions are areas of the pavement surface that present lower elevations than the
surrounding areas. Depressions are caused by settlement of the underlying subgrade or granular
base. The settlement is common over utility cuts and adjacent to road hardware. Depressions can
cause roughness in the pavement, and, when filled with water, can cause hydroplaning of vehicles.
Depressions are measured in square meters of surface area and the maximum depth of depression
defines the severity (Figure A2), according to the values reported in Table A2.
(a) (b) (c)
Figure A2. Depressions severity: (a) low; (b) medium; (c) high.
Table A2. Severity level of depressions.
Severity Level Maximum Depth of Depression
Low 15–30 mm
Medium 30–50 mm
High >50 mm
Appendix A.3. Edge Restraint
Edge strips and curbing are forms of restraints that provide lateral support for paver pavements.
Lateral restraint is considered essential to resist lateral movement, minimize loss of joint and bedding
sand, and prevent block rotation. Edge strips/curbs can comprise prefabricated angle supports,
concrete curbs, etc. This distress is accelerated by traffic loading. Loss of edge restraint is measured
Figure A1. Damaged Sampietrini severity: (a) low; (b) medium; (c) high.
Table A1. Severity level of damaged Sampietrini distress.
Severity Level Item
Low Individual cracks, separations or alterations
Medium Advanced cracking, separations or alterations
High Blocks are in multiple pieces or are disintegrated
Appendix A.2. Depressions
Depressions are areas of the pavement surface that present lower elevations than the surrounding areas.
Depressions are caused by settlement of the underlying subgrade or granular base. The settlement is common
over utility cuts and adjacent to road hardware. Depressions can cause roughness in the pavement, and, when
filled with water, can cause hydroplaning of vehicles. Depressions are measured in square meters of surface
area and the maximum depth of depression defines the severity (Figure A2), according to the values reported in
Table A2.
Appl. Sci. 2017, 7, 669 13 of 22
(a) (b) (c)
Figure A1. Damaged Sampietrini severity: (a) low; (b) medium; (c) high.
Table A1. Severity level of damaged Sampietrini distress.
Severity Level Item
Low Individual cracks, separations or alterations
Medium Advanced cracking, separations or alterations
High Blocks are in multiple pieces or are disintegrated
Appendix A.2. Depressions
Depressions are areas of the pavement surface that present lower elevations than the
surrounding areas. Depressions are caused by settlement of the underlying subgrade or granular
base. The settlement is common over utility cuts and adjacent to road hardware. Depressions can
cause roughness in the pavement, and, when filled with water, can cause hydroplaning of vehicles.
Depressions are measured in square meters of surface area and the maximum depth of depression
defines the severity (Figure A2), according to the values reported in Table A2.
(a) (b) (c)
Figure A2. Depressions severity: (a) low; (b) medium; (c) high.
Table A2. Severity level of depressions.
Severity Level Maximum Depth of Depression
Low 15–30 mm
Medium 30–50 mm
High >50 mm
Appendix A.3. Edge Restraint
Edge strips and curbing are forms of restraints that provide lateral support for paver pavements.
Lateral restraint is considered essential to resist lateral movement, minimize loss of joint and bedding
sand, and prevent block rotation. Edge strips/curbs can comprise prefabricated angle supports,
concrete curbs, etc. This distress is accelerated by traffic loading. Loss of edge restraint is measured
Figure A2. Depressions severity: (a) low; (b) medium; (c) high.
Table A2. Severity level of depressions.
Severity Level Maximum Depth of Depression
Low 15–30 mm
Medium 30–50 mm
High >50 mm
Appendix A.3. Edge Restraint
Edge strips and curbing are forms of restraints that provide lateral support for paver pavements. Lateral
restraint is considered essential to resist lateral movement, minimize loss of joint and bedding sand, and prevent
block rotation. Edge strips/curbs can comprise prefabricated angle supports, concrete curbs, etc. This distress is
Appl. Sci. 2017,7, 669 14 of 22
accelerated by traffic loading. Loss of edge restraint is measured in linear meters of pavement edge (measure the
movement of the edge restraint). The corresponding level of severity (Figure A3) is defined according to Table A3.
Appl. Sci. 2017, 7, 669 14 of 22
in linear meters of pavement edge (measure the movement of the edge restraint).
The corresponding level of severity (Figure A3) is defined according to Table A3.
(a) (b) (c)
Figure A3. Edge restraint severity: (a) low; (b) medium; (c) high.
Table A3. Severity level of edge restraint.
Severity Level Description
Low Evidence of increased joint width; (11–15 mm) to no evidence of paver/curb rotation
Medium Increased joint width (16–30 mm), with evidence of paver/curb rotation
High Increased joint width (>30 mm), with noticeable of paver/curb rotation and local
settlement
Appendix A.4. Excessive Joint Width
Excessive joint width is a surface distress feature in which the joints between blocks have
widened. Excessive joint width can occur from a number of factors, including poor initial
construction, lack of joint sand, poor edge restraint, adjacent settlement/heave, etc. As joints get
wider, the block layer becomes less stiff and can lead to overstressing the substructure layers.
Excessive joint width is measured in square meters of surface area and the average joint widening
defines the severity (Figure A4), according to the reference values reported in Table A4.
(a) (b) (c)
Figure A4. Excessive joint width severity: (a) low; (b) medium; (c) high.
Figure A3. Edge restraint severity: (a) low; (b) medium; (c) high.
Table A3. Severity level of edge restraint.
Severity Level Description
Low Evidence of increased joint width; (11–15 mm) to no evidence of paver/curb rotation
Medium Increased joint width (16–30 mm), with evidence of paver/curb rotation
High Increased joint width (>30 mm), with noticeable of paver/curb rotation and local settlement
Appendix A.4. Excessive Joint Width
Excessive joint width is a surface distress feature in which the joints between blocks have widened. Excessive
joint width can occur from a number of factors, including poor initial construction, lack of joint sand, poor edge
restraint, adjacent settlement/heave, etc. As joints get wider, the block layer becomes less stiff and can lead to
overstressing the substructure layers. Excessive joint width is measured in square meters of surface area and the
average joint widening defines the severity (Figure A4), according to the reference values reported in Table A4.
Appl. Sci. 2017, 7, 669 14 of 22
in linear meters of pavement edge (measure the movement of the edge restraint).
The corresponding level of severity (Figure A3) is defined according to Table A3.
(a) (b) (c)
Figure A3. Edge restraint severity: (a) low; (b) medium; (c) high.
Table A3. Severity level of edge restraint.
Severity Level Description
Low Evidence of increased joint width; (11–15 mm) to no evidence of paver/curb rotation
Medium Increased joint width (16–30 mm), with evidence of paver/curb rotation
High Increased joint width (>30 mm), with noticeable of paver/curb rotation and local
settlement
Appendix A.4. Excessive Joint Width
Excessive joint width is a surface distress feature in which the joints between blocks have
widened. Excessive joint width can occur from a number of factors, including poor initial
construction, lack of joint sand, poor edge restraint, adjacent settlement/heave, etc. As joints get
wider, the block layer becomes less stiff and can lead to overstressing the substructure layers.
Excessive joint width is measured in square meters of surface area and the average joint widening
defines the severity (Figure A4), according to the reference values reported in Table A4.
(a) (b) (c)
Figure A4. Excessive joint width severity: (a) low; (b) medium; (c) high.
Figure A4. Excessive joint width severity: (a) low; (b) medium; (c) high.
Appl. Sci. 2017,7, 669 15 of 22
Table A4. Severity level of excessive joint width.
Severity Level Average Joint Width
Low 11–15 mm
Medium 16–45 mm
High >45 mm
Appendix A.5. Faulting
Faulting are areas of the pavement surface where the elevation of adjacent blocks differ or have rotated.
Faulting can be caused by surficial settlement of the bedding sand, poor installation, pumping of the joint or
bedding sand. Local roughness can reduce the ride quality. Faulting can pose a safety hazard for pedestrians.
Faulting can be corrected by resetting the blocks. Faulting is measured in square meters of surface area. The
maximum elevation difference defines the severity (Figure A5), based on threshold values reported in Table A5.
Appl. Sci. 2017, 7, 669 15 of 22
Table A4. Severity level of excessive joint width.
Severity Level Average Joint Width
Low 11–15 mm
Medium 16–45 mm
High >45 mm
Appendix A.5. Faulting
Faulting are areas of the pavement surface where the elevation of adjacent blocks differ or have
rotated. Faulting can be caused by surficial settlement of the bedding sand, poor installation,
pumping of the joint or bedding sand. Local roughness can reduce the ride quality. Faulting can pose
a safety hazard for pedestrians. Faulting can be corrected by resetting the blocks. Faulting is
measured in square meters of surface area. The maximum elevation difference defines the severity
(Figure A5), based on threshold values reported in Table A5.
(a) (b) (c)
Figure A5. Faulting severity: (a) low; (b) medium; (c) high.
Table A5. Severity level of faulting.
Severity Level Elevation Difference
Low 6–10 mm
Medium 11–20 mm
High >20 mm
Appendix A.6. Heave
Heaves are areas of the pavement surface that have elevations that are higher than the
surrounding areas. Heaves are typically caused by differential frost heave of the underlying soils.
Heaves can also occur as a result of subgrade instability and can also occur in conjunction with
settlement/rutting. The most frequent cause of heave is a consequence of the presence of manhole
covers on the pavement. Heaves are measured in square meters of surface area. The maximum height
of heave defines the severity (Figure A6) according to the limits in Table A6.
Figure A5. Faulting severity: (a) low; (b) medium; (c) high.
Table A5. Severity level of faulting.
Severity Level Elevation Difference
Low 6–10 mm
Medium 11–20 mm
High >20 mm
Appendix A.6. Heave
Heaves are areas of the pavement surface that have elevations that are higher than the surrounding areas.
Heaves are typically caused by differential frost heave of the underlying soils. Heaves can also occur as a result of
subgrade instability and can also occur in conjunction with settlement/rutting. The most frequent cause of heave
is a consequence of the presence of manhole covers on the pavement. Heaves are measured in square meters of
surface area. The maximum height of heave defines the severity (Figure A6) according to the limits in Table A6.
Appl. Sci. 2017,7, 669 16 of 22
Appl. Sci. 2017, 7, 669 16 of 22
(a) (b) (c)
Figure A6. Heave severity: (a) low; (b) medium; (c) high.
Table A6. Severity level of heave.
Severity Level Maximum Height of Heave
Low 15–30 mm
Medium 31–50 mm
High >50 mm
Appendix A.7. Joint Sand Loss/Pumping
Joint sand loss/pumping is a distress feature in which the joint has been removed. Joint sand loss
can occur from a number of factors, including heavy rain, sweeping, pressure washing, pumping
under traffic loading, etc. Joint sand is considered essential to provide interlock and stiffness of the
paver course. The corresponding severity is defined by what reported in Table A7. Some examples
of this kind of distress are depicted in Figure A7.
(a) (b) (c)
Figure A7. Joint Sand Loss/Pumping severity: (a) low; (b) medium; (c) high.
Table A7. Severity level of Joint Sand Loss/Pumping.
Severity Level Depth of Sand Loss
Low 10–25 mm
Medium 26–45 mm
High >45 mm
Appendix A.8. Missing Sampietrini
Missing Sampietrini, as the name implies, refers to sections of pavement that are missing
Sampietrini, which may have resulted from removal or disintegration/damage. Missing Sampietrini
can compromise the integrity of the pavement structure and promote surface roughness similar to
potholes in flexible pavements. Missing of Sampietrini is measured in square meters of surface area.
Figure A6. Heave severity: (a) low; (b) medium; (c) high.
Table A6. Severity level of heave.
Severity Level Maximum Height of Heave
Low 15–30 mm
Medium 31–50 mm
High >50 mm
Appendix A.7. Joint Sand Loss/Pumping
Joint sand loss/pumping is a distress feature in which the joint has been removed. Joint sand loss can occur
from a number of factors, including heavy rain, sweeping, pressure washing, pumping under traffic loading,
etc. Joint sand is considered essential to provide interlock and stiffness of the paver course. The corresponding
severity is defined by what reported in Table A7. Some examples of this kind of distress are depicted in Figure A7.
Appl. Sci. 2017, 7, 669 16 of 22
(a) (b) (c)
Figure A6. Heave severity: (a) low; (b) medium; (c) high.
Table A6. Severity level of heave.
Severity Level Maximum Height of Heave
Low 15–30 mm
Medium 31–50 mm
High >50 mm
Appendix A.7. Joint Sand Loss/Pumping
Joint sand loss/pumping is a distress feature in which the joint has been removed. Joint sand loss
can occur from a number of factors, including heavy rain, sweeping, pressure washing, pumping
under traffic loading, etc. Joint sand is considered essential to provide interlock and stiffness of the
paver course. The corresponding severity is defined by what reported in Table A7. Some examples
of this kind of distress are depicted in Figure A7.
(a) (b) (c)
Figure A7. Joint Sand Loss/Pumping severity: (a) low; (b) medium; (c) high.
Table A7. Severity level of Joint Sand Loss/Pumping.
Severity Level Depth of Sand Loss
Low 10–25 mm
Medium 26–45 mm
High >45 mm
Appendix A.8. Missing Sampietrini
Missing Sampietrini, as the name implies, refers to sections of pavement that are missing
Sampietrini, which may have resulted from removal or disintegration/damage. Missing Sampietrini
can compromise the integrity of the pavement structure and promote surface roughness similar to
potholes in flexible pavements. Missing of Sampietrini is measured in square meters of surface area.
Figure A7. Joint Sand Loss/Pumping severity: (a) low; (b) medium; (c) high.
Table A7. Severity level of Joint Sand Loss/Pumping.
Severity Level Depth of Sand Loss
Low 10–25 mm
Medium 26–45 mm
High >45 mm
Appendix A.8. Missing Sampietrini
Missing Sampietrini, as the name implies, refers to sections of pavement that are missing Sampietrini, which
may have resulted from removal or disintegration/damage. Missing Sampietrini can compromise the integrity
Appl. Sci. 2017,7, 669 17 of 22
of the pavement structure and promote surface roughness similar to potholes in flexible pavements. Missing of
Sampietrini is measured in square meters of surface area. The severity is evaluated by level of distress (Figure A8),
according to indications in Table A8. Random individual paver damage would not be counted.
Appl. Sci. 2017, 7, 669 17 of 22
The severity is evaluated by level of distress (Figure A8), according to indications in Table A8.
Random individual paver damage would not be counted.
(a) (b) (c)
Figure A8. Missing Sampietrini severity: (a) low; (b) medium; (c) high.
Table A8. Severity level of missing Sampietrini.
Severity Level Description
Low Random individual missing Sampietrini
Medium Missing 2 or more Sampietrini in one area and ride quality unaffected
High Missing 2 or more Sampietrini in one area and ride quality affected
Appendix A.9. Patching
Patching refers to sections of pavement that are missing pavers and have been reinstated with a
dissimilar material. Patch quality can compromise the integrity of the pavement structure and
promote surface roughness similar to potholes in flexible pavements. Patches are measured in square
meters of surface area. The severity is evaluated by the quality of the patch (Figure A9), according to
indications in Table A9.
(a) (b) (c)
Figure A9. Patching severity: (a) low; (b) medium; (c) high.
Figure A8. Missing Sampietrini severity: (a) low; (b) medium; (c) high.
Table A8. Severity level of missing Sampietrini.
Severity Level Description
Low Random individual missing Sampietrini
Medium Missing 2 or more Sampietrini in one area and ride quality unaffected
High Missing 2 or more Sampietrini in one area and ride quality affected
Appendix A.9. Patching
Patching refers to sections of pavement that are missing pavers and have been reinstated with a dissimilar
material. Patch quality can compromise the integrity of the pavement structure and promote surface roughness
similar to potholes in flexible pavements. Patches are measured in square meters of surface area. The severity is
evaluated by the quality of the patch (Figure A9), according to indications in Table A9.
Appl. Sci. 2017, 7, 669 17 of 22
The severity is evaluated by level of distress (Figure A8), according to indications in Table A8.
Random individual paver damage would not be counted.
(a) (b) (c)
Figure A8. Missing Sampietrini severity: (a) low; (b) medium; (c) high.
Table A8. Severity level of missing Sampietrini.
Severity Level Description
Low Random individual missing Sampietrini
Medium Missing 2 or more Sampietrini in one area and ride quality unaffected
High Missing 2 or more Sampietrini in one area and ride quality affected
Appendix A.9. Patching
Patching refers to sections of pavement that are missing pavers and have been reinstated with a
dissimilar material. Patch quality can compromise the integrity of the pavement structure and
promote surface roughness similar to potholes in flexible pavements. Patches are measured in square
meters of surface area. The severity is evaluated by the quality of the patch (Figure A9), according to
indications in Table A9.
(a) (b) (c)
Figure A9. Patching severity: (a) low; (b) medium; (c) high.
Figure A9. Patching severity: (a) low; (b) medium; (c) high.
Appl. Sci. 2017,7, 669 18 of 22
Table A9. Severity level of patching.
Severity Level Description
Low Patch is in good condition and ride quality is unaffected
Medium Patch is in good to fair condition and ride quality is starting to deteriorate
High Patch is in poor condition and ride quality is affected
Appendix A.10. Rutting
Rutting is a surface depression in the wheel path. Depressions are areas of the pavement surface that have
elevations that are lower than the surrounding areas. Rutting is typically caused by settlement of the underlying
subgrade or granular base under vehicle loading. Depressions can cause roughness in the pavement and, when
filled with water, can cause hydroplaning of vehicles. Rutting is measured in square meters of surface area. The
maximum rut depth defines the severity (Figure A10). To determine the rut depth, a straight edge should be placed
across the rut and the depth measured in millimeters (Table A10). Rut depth measurements should be taken along
the length of the rut. Varying severities of rutting along the length of the rut should be measured individually.
Appl. Sci. 2017, 7, 669 18 of 22
Table A9. Severity level of patching.
Severity Level Description
Low Patch is in good condition and ride quality is unaffected
Medium Patch is in good to fair condition and ride quality is starting to deteriorate
High Patch is in poor condition and ride quality is affected
Appendix A.10. Rutting
Rutting is a surface depression in the wheel path. Depressions are areas of the pavement surface that
have elevations that are lower than the surrounding areas. Rutting is typically caused by settlement of the
underlying subgrade or granular base under vehicle loading. Depressions can cause roughness in the
pavement and, when filled with water, can cause hydroplaning of vehicles. Rutting is measured in square
meters of surface area. The maximum rut depth defines the severity (Figure A10). To determine the rut
depth, a straight edge should be placed across the rut and the depth measured in millimeters (Table A10).
Rut depth measurements should be taken along the length of the rut. Varying severities of rutting along
the length of the rut should be measured individually.
(a) (b) (c)
Figure A10. Rutting severity: (a) low; (b) medium; (c) high.
Table A10. Severity level of rutting.
Severity Level Maximum Depth of Rut
Low 5–15 mm
Medium 15–30 mm
High >30 mm
Appendix B. Distress Identification for All the Inspected Sections
This appendix reports the list of the distresses present in each surveyed section. For each distress,
the severity level, total quantity, density (ratio between total quantity and section area) and the
corresponding Deduct Value (DV) were calculated (Tables A11–A13). In particular, DVs are
calculated from Deduct Curves of each distress type report in [18], as already stated in Appendix A.
All sections areas were equal to 240 m
2
.
Once DV is calculated for each distress type and severity level combination, it is necessary to
combine all the DVs for each section, as reported in [10,18], to determine the correspondent maximum
Corrected Deduct Value (CDV). Finally, the PCI is calculated according to Equation (A1):
=− (A1)
Figure A10. Rutting severity: (a) low; (b) medium; (c) high.
Table A10. Severity level of rutting.
Severity Level Maximum Depth of Rut
Low 5–15 mm
Medium 15–30 mm
High >30 mm
Appendix B. Distress Identification for All the Inspected Sections
This appendix reports the list of the distresses present in each surveyed section. For each distress, the severity
level, total quantity, density (ratio between total quantity and section area) and the corresponding Deduct Value
(DV) were calculated (Tables A11–A13). In particular, DVs are calculated from Deduct Curves of each distress
type report in [18], as already stated in Appendix A. All sections areas were equal to 240 m2.
Once DV is calculated for each distress type and severity level combination, it is necessary to combine all the
DVs for each section, as reported in [
10
,
18
], to determine the correspondent maximum Corrected Deduct Value
(CDV). Finally, the PCI is calculated according to Equation (A1):
PCI =100 −CDVmax (A1)
Appl. Sci. 2017,7, 669 19 of 22
Table A11. Surveyed distresses for Sections 01 to 04.
Section ID Distress ID Severity Quantity Density Deduct Value PCI
Section 01
101 L 7.3 3.0% 1.4
94
105 L 22.1 9.2% 1.4
105 M 5.7 2.4% 2.8
106 M 1.3 0.5% 0.0
110 L 2.5 1.1% 0.0
Section 02
101 L 5.8 2.4% 1.4
74
102 L 2.9 1.2% 4.3
102 M 5.4 2.2% 14.5
105 L 7.6 3.2% 0.4
106 L 5.0 2.1% 4.2
108 L 6.0 2.5% 0.4
108 M 6.0 2.5% 1.4
Section 03
101 L 8.4 3.5% 1.4
12
101 M 1.8 0.8% 1.4
102 L 2.0 0.8% 4.3
102 H 7.0 2.9% 33.3
104 L 10.8 4.5% 6.9
104 M 14.8 6.2% 27.8
105 L 4.1 1.7% 0.1
105 M 2.2 0.9% 1.4
106 L 4.0 1.7% 4.2
106 M 10.9 4.5% 26.4
106 H 10.2 4.3% 44.4
109 H 0.5 0.2% 36.6
110 L 3.2 1.3% 0.3
110 M 6.3 2.6% 0.6
110 H 1.0 0.4% 0.4
Section 04
102 L 3.1 1.3% 4.3
76
102 M 4.7 2.0% 14.5
103 L 1.9 0.8% 2.7
103 M 2.8 1.2% 9.5
108 L 26.9 11.2% 1.4
110 L 1.2 0.5% 0.1
If none or only one individual deduct value is greater than 2, the sum of DVs is used in place of the maximum
CDV in determining the PCI; otherwise, to determine maximum CDV the following procedure must be used.
Individual DVs are listed in descending order and then, the allowable number of deducts (m) is calculated
using Equation (A2):
m=1+(9/98)×(100 −HDV)≤10, (A2)
where HDV is the highest individual deduct value. The number of individual deduct values is reduced to the m
largest deduct values, including the fractional part. If DVs available are less than m, all the DVs are used.
The maximum CDV is then calculated iteratively, following the steps described in [
10
,
18
]: “Determine total
deduct value by summing individual deduct values. The total deduct value is obtained by adding the individual
deduct values. Determine qas the number of deducts with a value greater than 2.0. Determine the CDV from total
deduct value and qby looking up the appropriate correction curve. Reduce the smallest individual deduct value
greater than 2.0 to 2.0 and repeat until q= 1. The maximum CDV is the largest of the CDVs”.
Appl. Sci. 2017,7, 669 20 of 22
Table A12. Surveyed distresses for Sections 05 to 10.
Section ID Distress ID Severity Quantity Density Deduct Value PCI
Section 05
101 L 1.9 0.8% 0.4
51
102 L 1.5 0.6% 4.3
102 M 4.5 1.9% 13.0
104 L 1.8 0.8% 1.4
104 M 3.0 1.3% 8.3
108 L 6.2 2.6% 0.3
108 M 13.3 5.5% 2.8
108 H 3.2 1.4% 1.4
111 L 8.0 3.3% 16.9
111 H 4.8 2.0% 34.0
Section 06
102 L 1.9 0.8% 4.3
88
102 M 1.7 0.7% 10.1
105 M 0.2 0.1% 0.0
Section 07
102 L 6.7 2.8% 7.2
92
105 M 0.8 0.3% 0.3
108 L 0.8 0.4% 0.1
Section 08
102 M 7.0 2.9% 8.0
60
102 H 5.0 2.1% 30.4
104 L 4.8 2.0% 4.2
108 M 4.0 1.7% 1.4
108 H 2.0 0.9% 1.4
110 L 4.0 1.7% 0.3
Section 09
102 L 1.0 0.4% 2.9
60
102 M 3.9 1.6% 13.0
102 H 4.5 1.9% 29.0
105 M 0.6 0.3% 0.4
106 M 1.6 0.7% 11.1
108 L 1.0 0.4% 0.1
108 M 3.0 1.3% 1.1
111 L 2.4 1.0% 7.0
Section 10
102 L 13.5 5.6% 11.6
55
102 M 11.0 4.6% 20.3
104 M 6.0 2.5% 15.3
105 M 4.0 1.7% 1.4
109 L 2.0 0.8% 18.3
110 L 8.4 3.5% 0.4
111 L 3.3 1.4% 9.9
Table A13. Surveyed distresses for Sections 11 to 14.
Section ID Distress ID Severity Quantity Density Deduct Value PCI
Section 11
102 L 6.5 2.7% 7.2
45
102 H 6.0 2.5% 31.9
104 M 5.0 2.1% 12.5
104 H 4.5 1.9% 22.2
105 L 1.5 0.6% 0.1
105 M 10.5 4.4% 2.8
110 L 10.7 4.5% 0.4
110 M 0.3 0.1% 0.0
111 L 6.6 2.8% 15.5
Appl. Sci. 2017,7, 669 21 of 22
Table A13. Cont.
Section ID Distress ID Severity Quantity Density Deduct Value PCI
Section 12
102 L 1.0 0.4% 2.9
45
104 L 7.5 3.1% 5.6
104 M 1.0 0.4% 2.8
105 L 0.5 0.2% 0.1
106 L 2.0 0.8% 2.8
110 L 8.0 3.3% 0.4
110 H 3.1 1.3% 1.4
111 L 10.0 4.2% 46.5
Section 13
102 L 9.0 3.8% 8.7
71
104 M 3.9 1.6% 9.7
106 L 2.4 1.0% 2.8
106 M 9.0 3.8% 23.6
Section 14
101 L 0.8 0.3% 0.4
79
102 L 14.4 6.0% 11.6
102 M 1.5 0.6% 10.1
104 L 9.1 3.8% 5.6
105 L 6.8 2.8% 0.3
105 M 4.1 1.7% 1.4
106 L 9.0 3.8% 5.6
109 L 0.4 0.2% 1.4
110 L 0.2 0.1% 0.0
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2017 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access
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