The road of experimental pavement structures: experience of five years operation/ Eksperimentiniu dangu konstrukciju bandomasis ruozas: penkeriu metu eksploatacijos patirtis/ Cels ar eksperimentalu segas konstrukciju: piecu gadu ekspluatacijas pieredze/ Eksperimentaalsete katseloikudega tee: viieaastane kasutuskogemus.
Vaitkus, Audrius ; Laurinavicius, Alfredas ; Oginskas, Rolandas 等
1. Introduction
Over the years, a significant amount of effort has been spent on
developing methods to objectively evaluate the condition of pavements
(Nejad, Zakeri 2011). The use of asphalt pavement is connected with
various operation characteristics, which are becoming the main object of
contemporary scientific research. The most common problems in the field
of road pavement operation are the formation of ruts, fatigue, as well
as thermal cracking, deterioration, aging and water susceptibility
(Navarro 2002). To increase the reliability of asphalt pavement, to
avoid premature failure of asphalt pavement, researches should be
strengthened to further study environmental influence in order to
improve the quality of asphalt pavement, and enhance the ability of
asphalt pavement (Yang, Ning 2011).
Surface cracking in pavements has long been regarded as the main
cause of deterioration of roads because surface water penetration
reduces the strength of subbase layers and results in broader cracks and
potholes. Thus, surface cracking has a direct effect on pavement's
quality and service life, which attracts more and more attention in
recent years (Xu et al. 2011). Asphalt pavement is subjected to many
distresses during its service life. One of the main distresses is
rutting. Recently, rutting in asphalt pavements has become one of the
major distress forms with the increase in traffic volume, tire pressure
and axial load. It often happens within the first few years after
opening to traffic. The rut is formed because of the shear stress in
asphalt layer which causes large plastic deformations, so the part of
the asphalt layer is imprinted into the ridge at the edges of wheel roll
zone (Oscarsson 2011; Xu, Huang 2012).
Stiffness of asphalt pavement layers, as well as deflections
measured by the Falling Weight Deflectometer (FWD) and the calculated
equivalent stiffness modulus [E.sub.0] values depend on pavement
temperature. Temperature is one of the main factors affecting road
design, construction and maintenance. Therefore,
Jukneviciute-Zilinskiene (2010) suggested a climatic zoning of the
territory of the Republic of Lithuania from the point of view of road
construction. Motiej?nas et al. (2010) made an assessment of temperature
distribution in the different layers of asphalt pavement dependent on
environmental temperature as well as the influence of the temperature
variation on the stiffness of asphalt layers.
Asphalt mixture is a heterogeneous complex composite material of
air, binder and aggregates used in modern pavement construction (Xu
2012). Modification of asphalt mix with polymer or other additives
increases durability of asphalt pavement and decreases rutting
(Kamaruddin et al. 2010; Moghaddam et al. 2011). Vaitkus et al. (2009)
ascertained that the use of particular supplements in warm mix asphalt
increases stiffness of the binder and at the same time improves
resistance to rutting. The material used and the thickness of frost
blanket course must not only ensure the required resistance to frost of
road pavement structure but also to increase bearing capacity of the
structure, to distribute and reduce pressure to the subgrade surface.
Vaitkus et al. (2012) suggested the materials for a frost blanket course
and recommended that when laying a frost blanket course to take into
consideration bulk density and Proctor density of the material used, as
well as transportation costs.
2. Main characteristics of the road of experimental pavement
structures
In 2007, near Vilnius City in Pagiriai settlement the road of
experimental pavement structures was constructed. Parameters of the road
of experimental pavement structures according to STR 2.06.03:2001
Statybos techninis reglamentas "Automobiliu keliai"
[Construction Technical Regulation "Motor roads"] corresponds
to the road category III (2 traffic lanes, pavement width--7 m, roadside
width--1 m) and the pavement structure class III (ESAL's of 100 kN
= (0.8-3.0) mln). The road of experimental pavement structures, which is
710 m long, consists of 23 sections 30 m long and one section 20 m long.
Three sections are additionally divided into 15 m sections. Pavement
structures of various kinds were constructed at these sections. The
experimental road was constructed on the way to the gravel quarry where
the empty heavy vehicles go in and the loaded go out. In this case, one
traffic lane of the experimental road is loaded much more than the other
(Cygas et al. 2008).
Various materials were used for constructing every layer of
experimental road section. The frost blanket course was built from sand
(0/4, 0/11); the base course--from crushed dolomite and granite (0/56,
0/32), the mix of 50% crushed granite and 50% sand and gravel, crushed
gravel mix, gravel and sand mix and the reclaimed asphalt. The asphalt
base course was built from 0/32-C (AC 11 PS) crushed dolomite, gravel,
100% crushed gravel, 50% crushed dolomite and 50% crushed gravel;
asphalt binder course: 0/16-A (AC 16 AS), 0/16-[A.sub.PMB] (AC 16 AS
PMB) crushed granite 11/16 + crushed dolomite 5/8 + (crushed dolomite
and crushed granite 8/11, 50% and 50%); crushed granite 8/11 and 11/16 +
crushed gravel (rest of aggregates); crushed dolomite 8/11 and 11/16 +
crushed gravel (rest of aggregates); 50% crushed granite + 50% sand;
100% crushed granite; 100% crushed gravel. Asphalt surface layer: 0/11
S-V (AC 11 VS), 0/11 S-M (SMA 11 S), 0/11 [S-M.sub.PMB] (SMA 11 S PMB),
Confalt (Vaitkus et al. 2010).
The thickness and materials of every pavement structure were chosen
according to the reference pavement structure which was built from
asphalt surface layer 0/11 S-V (AC 11 VS); asphalt binder course 0/16-A
(AC 16 AS); asphalt base course 0/32-C (AC 32 PS); base course--crushed
dolomite 0/56; frost blanket course--sand 0/11 (Fig. 1) (Laurinavicius
et al. 2009).
[FIGURE 1 OMITTED]
Every year at the experimental road section the following
measurements are taken:
--measurement of traffic flow,
--measurement of temperature and moisture in different layers of
pavement structure,
--measurement of rutting,
--visual assessment of pavement distress,
--measurement of pavement roughness,
--measurement of pavement skid resistance,
--measurement of pavement equivalent stiffness modulus [E.sub.0]
with FWD,
--measurement of pavement deflection with Benkelman Beam.
During the year the traffic volume changes (Cygas et al. 2011). The
increase in the traffic volume and loads leads to pavement deterioration
and, consequently, to the failure (Khedra, Breakahb 2011).
Investigations of the test road section are performed in parallel with
the determination of traffic flow. The traffic flow is recorded
constantly after the opening of the road for traffic. For the
classification of traffic flow the induction loops are installed into
the road pavement. The volume of traffic on the experimental road test
section is measured every day and data is collected week by week.
Traffic flow distribution in the loaded traffic lane in 2008-2012 is
presented in Fig. 2.
The assessment of the loaded traffic lane enables to define the
highest traffic volume which dominates from summer to the beginning of
autumn, and the lowest--in winter. When analysing the traffic volume of
2008-2012 it was determined that the highest traffic volume was in 2008.
Heavy vehicles in 2008 made 23%, in 2009--17.5%, in 2010--16.5%, in
2011--21.8% of the total traffic volume (Cygas et al. 2011).
All the vehicles were rated according to [ESAL's.sub.100] =
100 kN. [ESAL's.sub.100] distribution at the time of the operation
of experimental section is presented in Fig. 2. The experimental road is
used by 70 000 [ESAL's.sub.100] in average annually, the total
amount of [ESAL's.sub.100] from the beginning of road use to May,
2012 was 320 000. Distribution of [ESAL's.sub.100] of the
experimental pavement structures is presented in Fig. 3.
[FIGURE 2 OMITTED]
3. Results of annual measurements
3.1. Temperature and moisture of pavement structure
Periodical investigations of strength indices and analysis of the
obtained results encouraged to install temperature and moisture sensors
in one of pavement structures where in 2009 seven temperature sensors of
12-Bit Temperature Smart Sensor type were installed: temperature sensor
T1 was installed at the surface of the asphalt surface layer; T2--in the
asphalt surface layer (at a 2 cm depth from pavement surface); T3--at
the interface of the asphalt surface and base course (at a 4 cm depth
from pavement surface); T4--at the interface of the asphalt base course
and road base (at a 8 cm depth from pavement surface), T5 in the asphalt
road base (at a 10 cm depth from pavement surface); T6--at the interface
of the asphalt road base and the crushed dolomite subbase layer (at a 18
cm depth from pavement surface) and temperature sensor T7 was erected in
the subgrade (at a 125 cm depth from pavement surface).
Analysing the highest temperature distribution in structural
pavement layers in 2010-2011 the highest temperatures were found on the
17th of July at the asphalt pavement surface (+52.75[degrees]C); in the
asphalt surface layer (+52.20[degrees]C); at the interface of the
asphalt surface and base courses (+49.41[degrees]C); at the interface of
the asphalt binder and asphalt base courses (+46.13[degrees]C); in the
asphalt base course (+44.72[degrees]C); at the interface of the asphalt
base course and road base from crushed dolomite mix (+39.21[degrees]C)
and in the subgrade (+27.65[degrees]C) on the 18th of August. Analysing
the lowest temperature distribution in pavement structure layers in
2010-2011, the lowest temperatures are found on the 25th of January at
the asphalt pavement surface (-21.87[degrees]C); in the asphalt surface
layer (-21.77[degrees]C); at the interface of the asphalt surface and
base courses (-20.93[degrees]C); at the interface of the asphalt binder
and asphalt base courses (-19.79[degrees]C); in the asphalt base course
(-18.88[degrees]C); at the interface of the asphalt base course and road
base from crushed dolomite mix (-16.28[degrees]C) and in the subgrade
(-3.75[degrees]C) on the 30th of January. The highest and the lowest
temperatures of pavement structure are presented in Fig. 4.
The temperature in the surface layer of the asphalt pavement
structure changes during the year from -21.77[degrees]C to
+52.75[degrees]C, thus, the difference is more than 70[degrees]C. It is
obvious that such huge changes in the temperature of asphalt layer
negatively influence the asphalt characteristics and lead to the early
pavement distress. The similar situation is in asphalt binder layers.
The suggestion is to use the polymer modified binders for asphalt
surface and binder layers of asphalt pavement for the pavement
structures of classes SV and I-III.
3.2. Bearing capacity of pavement structures
The bearing capacity of pavement structures was evaluated by two
non-destructive methods--measuring pavement response with Benkelman Beam
and pavement deflections with FWD.
[FIGURE 4 OMITTED]
[FIGURE 5 OMITTED]
Benkelman Beam measures the max pavement deflection and response
caused by static load of dual wheels. Measurements with Benkelman Beam
are carried out two times a year in spring and autumn. Measurements are
taken in 3 points of each section in the rut of the right wheel (2
points) and between the ruts (1 point). The highest mean values of
equivalent stiffness modulus E measured in the rut (vary from 877 MPa to
519 MPa) at [ESAL's.sub.100] = 180 000 (2010). The lowest mean
values of equivalent stiffness modulus E (vary from 591 MPa to 397 MPa)
at ESAL's100 = 40 000 (2008). The distribution of equivalent
stiffness modulus E of pavement structures after different number of
ESAL's is presented in Fig. 5.
When measuring with FWD the pavement structure deflections from the
dynamic loading are registered.
Measurements are taken in 4 points of each section in the rut of
the right wheel and between the ruts. The mean of the rut in the right
wheel is taken by 3 values. The highest mean values of equivalent
stiffness modulus [E.sub.0] (vary from 1080 MPa to 753 MPa) at
[ESAL's.sub.100] = 320 000 (2012). The lowest mean values of
equivalent stiffness modulus [E.sub.0] (vary from 823 MPa to 612 MPa) at
[ESAL's.sub.100] = 120 000 (2009). The highest bearing capacity in
the loaded traffic lane at [ESAL's.sub.100] = 320 000 (2012) was
represented by the pavement structures: 5, 9, 3, 17, 16, 20th--1080 MPa
(asphalt surface layer AC 11 VS, asphalt binder course AC 16 AS, asphalt
base course AC 32 PS, base course--reclaimed asphalt pavement and
crushed dolomite 0/32, frost blanket course--sand 0/11); 9th--1056 MPa
(asphalt surface layer--Confalt, asphalt binder course--AC 16 AS,
asphalt base course--AC 32 PS, base course--crushed dolomite 0/56, frost
blanket course--sand 0/11); 3th--980 MPa (asphalt surface layer AC 11
VS, asphalt binder course--AC 16 AS, asphalt base course AC 32 PS, base
course crushed dolomite 0/56, frost blanket course--sand 0/4); the
lowest bearing capacity was represented by the following pavement
structures: 17th--753 MPa (asphalt surface layer AC 11 VS, asphalt
binder highest bearing capacity AC 16 AS (100% granite), asphalt base
highest bearing capacity AC 32 PS, base highest bearing
capacity--crushed dolomite 0/56, frost blanket highest bearing capacity
sand 0/11); 16th--764 MPa (asphalt surface highest bearing capacity AC
11 VS, asphalt binder highest bearing capacity AC 16 AS (50% crushed
granite + 50% sand), asphalt base highest bearing capacity AC 32 PS,
base highest bearing capacity--crushed dolomite 0/56, frost blanket
highest bearing capacity--sand 0/11); 20th--769 MPa (asphalt surface
highest bearing capacity AC 11 VS, asphalt binder highest bearing
capacity AC 16 AS, asphalt base highest bearing capacity AC 32 PS, base
highest bearing capacity crushed dolomite 0/56, frost blanket highest
bearing capacity--sand 0/11). The distribution of equivalent stiffness
modulus [E.sub.0] of pavement structures after different number of
ESAL's is presented in Fig. 6.
[FIGURE 6 OMITTED]
The analysis of results of the bearing capacity of pavement
structure shows that the highest values are obtained in pavement
structures where the thicker (30 cm) base highest bearing capacity of
crushed dolomite was used, also where the base highest bearing capacity
was constructed with reclaimed asphalt 10 cm plus crushed dolomite 10
cm. The pavement structure with semi rigid surface highest bearing
capacity also showed high result. The lowest bearing capacity values
were obtained in pavement structures with crushed granite and sand mix
asphalt binder highest bearing capacity and also pavement structure with
geosynthetics at the bottom of asphalt binder highest bearing capacity.
It should be stated that the measurements by using different methods to
evaluate the bearing capacity of asphalt pavement structure showed
different results.
3.3. Roughness of pavement structures
Roughness of asphalt pavement structures of experimental road is
measured in both traffic lanes--loaded and unloaded. Measurements are
taken by the mobile road research laboratory RST-28. Roughness expressed
by the international roughness index IRI, m/km, is presented as the mean
value of 30 m taken from each pavement structure. Distribution of
roughness in different pavement structures depending on the number of
ESAL's is presented in Fig. 7.
Analysis of roughness is more concentrated on the changes of IRI in
each pavement structure depending on the time of its operation and the
number of ESAL's. Differences between the IRI of pavement
structures are influenced by construction and are independent of the
type of pavement structure. The collected results showed that roughness
decreased after five years of road operation and after 320 000 of
ESAL's, though the decrease is not sufficient, changing max 0.3
m/km.
3.4. Rutting of pavement structures
The rut depth of asphalt pavement structure of the experimental
road is measured in both traffic lanes--loaded and unloaded.
Measurements are carried out by the mobile road research laboratory
RST-28. The rut depth is measured using laser sensors which measure
transverse road profile in certain intervals and ensure sufficient
reliability for the definition of rut depth.
Measurements of the rut depth are taken every meter, totally 30
values for each pavement structure. The average depth of the right rut,
the left rut and the max clearance was counted of every pavement
structure. To increase the accuracy of measurements and to get the
reliable analysis results the additional statistical analysis was made.
The analysis showed that the most relevant statistical index is Median
(Vaitkus et al. 2012). Distribution of the right rut depth of different
pavement structure dependent on the number of ESAL's is presented
in Fig. 8.
[FIGURE 7 OMITTED]
[FIGURE 8 OMITTED]
At first the measurements of the loaded traffic lane right rut
depth were taken by the mean values in 2008 and 2009. Since 2010 the
assessment of rut depth measurements, i. e. comparing the differences
between the min and max values, the average of rut depth in 30 m and 20
m sections, the average of rut depth at 30 m, median and mode at
different number of [ESAL's.sub.100], were taken by the median.
Fig. 8 showed that the highest rut depth values are defined at
[ESAL's.sub.100] = 320 000 in the 22th--5.7 mm (asphalt surface
layer AC 11 VS, asphalt binder course AC 16 AS, asphalt base course AC
32 PS, base course--crushed dolomite 0/56, frost blanket course--sand
0/11); 27th--5.7 mm (asphalt surface layer AC 11 VS, asphalt binder
layer AC 16 AS, asphalt base course AC 32 PS (50% crushed dolomite + 50%
crushed gravel), base course--crushed dolomite 0/56, frost blanket
course--sand 0/11); 20th--5.6 mm (asphalt surface layer AC 11 VS,
asphalt binder course AC 16 AS, asphalt base course AC 32 PS, base
course--crushed dolomite 0/56, frost blanket course--sand 0/11); the
lowest rut depth--in the 1st--3.6 mm (asphalt surface layer AC 11 VS,
asphalt binder course AC 16 AS, asphalt base course AC 32 PS, base
course--gravel-sand mix 0/32, frost blanket course--sand 0/11);
12th--3.7 mm (asphalt surface layer SMA 11 S, asphalt binder course AC
16 AS, asphalt base course AC 32 PS, base course--crushed dolomite 0/56,
frost blanket course--sand 0/11); 11th--3.7 mm (asphalt surface layer
SMA 11 S, asphalt binder course AC 16 [AS.sub.PMB], asphalt base course
AC 32 PS, base course--crushed dolomite 0/56; frost blanket course--sand
0/11). Comparing the measured values with the limit values, the rut
depth does not exceed the limit value which is 2.5 cm for regional
roads.
The measurements of rutting showed that the max rut depths vary
from 3.5 mm to 5.5 mm dependent on pavement structure type. The min
distressed pavement structures are those with semi rigid surface layer,
also the pavement structures with stone mastic asphalt (SMA) surface
layer (with PMB and without) and pavement structure with asphalt binder
course with polymer modified bitumen (PMB). The max distressed pavement
structures are those with geosynthetics between asphalt binder and
asphalt base course, also with geosynthetics between base and subbase
course. The pavement structure with the base course from crushed
dolomite and crushed gravel mix also showed uncomplimentary results.
[FIGURE 9 OMITTED]
[FIGURE 10 OMITTED]
3.5. Distress of pavement structures
Every year the distress of pavement structures was measured on the
test road section. Measurements of pavement structure distress were
carried out in spring and autumn. During 5 years of experimental road
operation only longitudinal and transverse cracks were identified (Figs
9-10). Longitudinal cracks are running parallel to the pavement center
lane, while transverse cracks extend across the center lane. The
cracking mostly appears in the pavement structure with semi rigid
surface layer. Longitudinal cracks are caused by the violations of
construction technology, and transverse cracks are attributed to the
temperature cracks caused by temperature fluctuations and freeze.
4. Conclusions
The road of experimental pavement structures in Lithuania was built
to expand experimental investigations of the separate structural
pavement layers under the real conditions. Analysis of the results of 5
years experimental research of the test road section showed that all 27
pavement structures still have perfect operational characteristics.
Assessment of the loaded traffic lane enabled to define the highest
traffic volume which dominates from summer to the beginning of autumn,
and the lowest--in winter. When analysing the traffic volume in the
period 2008-2012 it was determined that the highest traffic volume was
in 2008. The heavy vehicles in 2008 made 23%, in 2009--17.5%, in
2010--16.5%, in 2011--21.8% of the total traffic flow.
The difference of temperature in the surface layer of the asphalt
pavement structure changes during the year from -21.77[degrees]C to
+52.75[degrees]C, the difference is more than 70[degrees]C. It is
obvious that such huge changes of temperature in asphalt layer
negatively influence asphalt characteristics and lead to the early
pavement distress. The similar situation is in asphalt binder course.
The suggestion is to use the polymer modified binders for asphalt
surface and binder layers of asphalt pavement for the pavement
structures of classes SV and I-III.
Analysis of the results of pavement structure bearing capacity
shows that the highest values are obtained in pavement structures where
the thicker (30 cm) base course of crushed dolomite was used, also where
the base course was constructed with reclaimed asphalt 10 cm plus
crushed dolomite 10 cm. The pavement structure with semi rigid surface
layer also showed high result. The lowest bearing capacity values were
obtained in pavement structures with crushed granite and sand mix
asphalt binder course, and also in pavement structure with geosynthetics
at the bottom of asphalt binder course.
Analysis of roughness is more concentrated on the changes of IRI in
each pavement structure depending on the time of its operation and the
number of ESAL's. Differences between the IRI of pavement
structures are influenced by construction and are independent of the
type of pavement structure. The collected results showed that roughness
decreased after five years of road operation and after 320 000 of
ESAL's, though the decrease is not sufficient, changing max 0.3
m/km.
The measurements of rutting showed that the max rut depths vary
from 3.5 mm to 5.5 mm dependent on pavement structure type. The min
distressed pavement structures are those with semi rigid surface layer,
also the pavement structures with SMA surface layer (with PMB and
without) and pavement structure with asphalt binder course with PMB. The
max distressed pavement structures are those with geosynthetics between
asphalt binder and asphalt base course, also with geosynthetics between
base and subbase course. The pavement structure with the base course
from crushed dolomite and crushed gravel mix also showed uncomplimentary
results.
The cracking mostly appears in the pavement structure with semi
rigid surface layer. Longitudinal cracks are caused by the violations of
construction technology.
Recommendations
Pavement distresses after five years of road operation emerged not
only due to the environmental conditions and traffic flow but also due
to the materials of pavement structure. It is recommended to proceed the
research of experimental pavement structures and to evaluate the
distress of pavement structures with regard to the changes in moisture
and temperature of base course and subgrade.
It is recommended to use the accelerated testing methods, such as
heavy vehicle simulator, to speed up the experimental research and to
get the results more quickly.
doi: 10.3846/bjrbe.2012.30
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Received 14 November 2011; accepted 22 August 2012
Audrius Vaitkus (1) [mail], Alfredas Laurinavicius (2), Rolandas
Oginskas (3), Algirdas Motiejunas (4), Migle Paliukaite (5), Oksana
Barvidiene (6)
(1,4, 5) Road Research Institute, Vilnius Gediminas Technical
University, Linkmenu g. 28, 08217 Vilnius, Lithuania (2,3) Dept of
Roads, Vilnius Gediminas Technical University, Sauletekio al. 11, 10223
Vilnius, Lithuania (6) Dept of Hydrology, Vilnius Gediminas Technical
University, Sauletekio al. 11, 10223 Vilnius, Lithuania E-mails: (1)
audrius.vaitkus@vgtu.lt; (2) alfredas.laurinavicius@vgtu.lt; (3)
rolandas.oginskas@vgtu.lt; (4) algirdas.motiejunas@vgtu.lt; (5)
migle.paliukaite@vgtu.lt; (6) oksana.barvidiene@vgtu.lt
Fig. 3. Distribution of [ESAL's.sub.100] of the experimental
pavement structures
ESAL's of the year ESAL's total
2008 80 000 100 000
2009 60 000 160 000
2010 70 000 230 000
2011 70 000 300 000
2012-05 20 000 320 000
Note: Table made from line graph.