Airport runway construction

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Runway Pavement Reconstruction with Full Material Recycling: The Case of
the Airport of Treviso
Article in Advanced Materials Research · August 2013
DOI: 10.4028/www.scientific.net/AMR.723.1044
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2. Runway Pavement Reconstruction with Full Material Recycling: The
Case of the Airport of Treviso
BOCCI Maurizio1, a
, MANGANARO Andrea2,b
, STRAMAZZO Virginio3,c
and GRILLI Andrea4,d
1
Università Politecnica delle Marche, Dipartimento di Ingegneria Civile, Edile e Architettura, via
Brecce Bianche, Ancona, Italy
2
SAVE Engineering SpA, Gruppo SAVE, Viale G. Galilei, 30/1, 30173, Venice, Italy
3
SAVE SpA, Gruppo SAVE, Viale G. Galilei, 30/1, 30173, Venice, Italy
4
Università degli Studi della Repubblica di San Marino, Dipartimento di Economia e Tecnologia,
Salita alla Rocca 44, San Marino, Republic of San Marino
a
m.bocci@univpm.it, b
amanganaro@veniceairport.it, c
vstramazzo@veniceairport.it and
d
andrea.grilli@unirsm.sm
Keywords: soil stabilization, milled cement concrete, reclaimed asphalt, C&D concrete.
Abstract. This technical paper shows the innovative approach used in the rehabilitation of the
runway of the airport of Treviso. Treviso is located in North Italy and lies about 40 km far from
Venice. For this reason, the airport of Treviso may be considered the second airport of Venice and
receives the low-cost companies. In order to minimize the environmental impact of the
rehabilitation project, the materials coming from the demolition of the old runway pavement were
completely recycled in the new runway pavement. Several recycling techniques were used such as
the cement stabilization of soil, cement treatment of milled cement concrete and cement-bitumen
treatment of reclaimed asphalt. This paper shows the technical application of scientific knowledge
on pavement recycling developed in Italy in the last decade.
Introduction
The airport of Treviso “Antonio Canova” (ICAO code: LIPH, IATA code: TSF) is classified as
civil airport for national and international traffic. It is located about 3 Km south-west from the city
of Treviso (Italy) and works in synergy with the airport of Venice Tessera. Treviso airport is
managed by AER TRE S.p.A., owned for 80% by the SAVE Group which manages also the airport
of Venice and has fully funded the herein described works. The 2.5 million of passengers per year
rank the Treviso airport as the 16th
Italian airports.
According to 14 ICAO Annex (fifth edition – July 2009), the runway RWY07/25 is classified
with the code 4D and has a length of 2,420 m and a width of 45 m. In details, the paved area was in
hot mix asphalt (HMA) for a length of about 2,000 m with heads in rigid concrete slabs for a length
of 420 m.
The perspective of direct reuse of demolition materials in road construction has been studied for
several years [1, 2, 3, 4, 5]. Considering the amount of recycled materials and the traffic volume,
the rehabilitation of the runway of the Treviso airport raised particular interest. Indeed, the
approach for the rehabilitation project makes the airport of Treviso one of the most extended
application of many recycling techniques, i.e. cement stabilization of soil, recycled materials, reuse
of Reclaimed Asphalt (RA) following different methods.
The overall rehabilitation project also involved the construction of the new connection between
the runway and the apron and the new drainage system.
Project development
Based on preliminary investigations, the old runway pavement consisted of 20 cm of HMA, 80
cm of granular mixture and a subgrade in silty fine sand. While, the two runway heads was in non-
reinforced cement concrete slabs with a thickness of 40 cm laying on a granular foundation of 40
cm.
Advanced Materials Research Vol. 723 (2013) pp 1044-1051
© (2013) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/AMR.723.1044
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP,
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3. The first design proposal for the runway rehabilitation involved the construction of the following
pavement structure (including the new heads):
• wearing course in HMA with SBS modified bitumen: 4 cm;
• binder course in HMA with neat bitumen: 6 cm;
• base course in HMA with neat bitumen: 10 cm;
• sub-base course in stabilized RA with foamed bitumen and cement: 20 cm;
• foundation course in granular mixture: 35 cm;
• subgrade in silty sand characterized by a California bearing ratio (CBR) 9%.
During the first phase of the construction, three key factors led to a new design:
• the discovery of the old military runway that lied under about 2/3 of the old runway (1500 m
length and 45 m width). The old military runway, dating back to the beginning of the last century,
consisted of 20-cm thick of non-reinforced cement concrete and it was placed at a depth of about 40
cm from the surface. The cement slab represented a discontinuity element and interfered with the
constructive techniques considered (Fig. 1);
• the heterogeneity of the subgrade materials, very different from those assumed in the first
design hypothesis, especially around the military runway;
• the larger amount of the reclaimed materials if compared with the amount supposed in the
first design hypothesis.
In order to minimize the environmental impact, the rehabilitation project adopted several
recycling techniques aimed to the full material recycling and considering the construction and
demolition material (C&D) [6, 7, 8] and RA [9, 10].
Fig. 1 Cavities under the cement concrete layer
The combination of above-mentioned factors and the need to maximize the daily production,
forced to seek a new technical alternative using specific recycling techniques.
Exploiting the RA (about 40,000 m3
), the crushed cement concrete (CCC) of the heads of the
(25,000 m3
), the CCC from the old military runway (27,000 m3
), and the granular material of the
foundation (13,600 m3
) the following pavement structure was considered:
• wearing course in HMA with SBS modified bitumen: 4 cm;
• binder course in HMA with SBS modified bitumen: 5 cm;
• base course in HMA with SBS modified bitumen: 8 cm;
• subbase course in stabilized RA with cement and bituminous emulsion: 18 cm;
• foundation course in cement stabilized reclaimed materials (50% of CCC and 50% of RA):
20 cm;
• capping course in cement stabilized sandy gravel: 20 cm;
• subgrade in cement stabilized silty sand: 30 cm.
The verification of the new pavement structure was performed with the FAARFIELD software
[11]. The new design led to an increase of the pavement in-service life of about 10% with huge
benefits in terms of amount of reused materials, time consumption and costs.
Advanced Materials Research Vol. 723 1045

4. In situ soil stabilization for the subgrade
After a preliminary survey, the subgrade resulted very heterogeneous in the whole area and
classified as A4 and A2-4 soil according to the Highway research board (HRB). Since there was no
clay soils, the cement stabilization technique was chosen in order to ensure appropriate and
standardized bearing capacity and stability over time. To obtain a homogeneous bearing capacity
(deformation modulus ≥ 50 MPa at 24 hours after construction) and on the basis of a preliminary
laboratory investigation, two technical solutions were compared.
A trial section was built using the subgrade materials and considering two alternatives:
stabilization (30 cm depth) with 2,5 and 3% of cement.
The results of the mentioned trial section are reported in Table 1.
From the trial section, the stabilization with 3% of cement was selected because it ensured higher
bearing capacity over time.
Table 1 Results of static plate load tests on the trial section for the subgrade stabilization
Deformation modulus [N/mm2
]
Cement dosage [%] Curing period [days]
1 3 4 5 6 7 8 9
2.5 21 39 - - - 64 - 81
3 52 - - 127 128 133 -
Specifications [N/mm2
] > 50
In situ recycling of CCC and RA for the foundation course
For the foundation course the in situ stabilization with cement (II/B-LL 32,5 R, EN 197-1) was
chosen to treat a granular mix of 50% CCC and 50% RA.
The mix design was carried out through a laboratory study and a trial section. The comparison
of laboratory results and in situ survey allowed the determination of reference performance
parameters (density, water content, mechanical performance of the mixture) for the subsequent
monitoring process during construction and the determination of technical phases.
The experimental program in laboratory considered indirect tensile strength test (ITS) complying
with EN 13286-42 and unconfined compressive test (UCS) complying with EN 13286-41 on
specimens compacted by means of a shear gyratory compactor (SGC). The recycled mixture was
stabilized using four dosage of cement: 2, 2.5, 3 and 3.5. Specimens were divided into two series
and subjected to a curing period of 2 and 7 days at 25°C before testing. From Table 2 it can be
asserted that all mixtures allowed the respect of the relative specifications.
Table 2 ITS and UCT values of recycled mixtures for the foundation course
Curing period: 2 days at 25°C Curing period: 7 days at 25°C
Cement dosage [%] ITS [MPa] UCS [MPa] ITS [MPa] UCS [MPa]
2 0.24 2.40 0.26 5.00
2.5 0.26 3.80 0.28 5.20
3 0.27 4.10 0.29 4.50
3.5 0.29 4.50 0.32 6.70
Specifications [MPa] > 0.15 > 1.50 - -
To determine the practical procedure in situ and to validate the design mixture, a trial section
using the same mixtures was built (Fig. 2) and tested in situ by means of plate load test.
Table 3 shows the results obtained from the plate load tests on the trial section.
Considering the results from the laboratory study and the trial section investigation, the mixture
using 50% CCC and 50% RA stabilized with 2.5% of cement satisfied specification requirements
minimizing the costs and was selected as design mixture.
1046 Innovation and Sustainable Technology in Road and Airfield Pavement

5. Fig. 2 Laying and compaction of the recycled stabilized mixtures for foundation course
Table 3 Deformation modulus values of recycled mixtures for the foundation course
Deformation modulus [N/mm2
]
Cement dosage [%] Curing period [days]
1 5 7
2 71 125 159
2.5 82 113 160
3 55 115 133
3.5 68 147 135
Specifications [N/mm2
] > 80 - > 120
In situ recycling of RA for the subbase course
The cement-bitumen treated material (CBTM) for the subbase course was studied through the
monitoring of a trial section and laboratory tests, in order to find the optimal combination of binders
and to fix the construction procedure and the reference performance to be checked in the
construction phase.
The characteristics of the C 60 B 5 bituminous emulsion (EN 13808) are showed in Table 4,
while the cement used was classified as cement type II/B-LL 32,5 R (EN 197-1).
Table 4 Emulsion and extracted bitumen properties
Emulsion characteristics
Water content (EN 1428) 40%
pH value (EN 12850) 3
Settling tendency @ 7 gg (EN 12847) 8%
Breaking value (EN 13075-1) 190 g
Mixing stability with cement (EN 12848) 0.5 g
Application temperature 5÷80°C
Characteristic of the extracted bitumen
Needle penetration (EN 1426) 70 dmm
Softening point (EN 1427) 50°C
Fraass breaking point (EN 12593) -10°C
On the basis of scientific [1, 5, 12] and technical experiences [9, 10, 13, 14], five mixtures were
produced in the trial section using 100% of RA and the following combination of binders:
• 3% of cement, 2.5% of bituminous emulsion, 2% of mineral filler (3C2.5E2F)
• 2% of cement, 3% of bituminous emulsion, 2% of mineral filler (2C3E2F)
• 2% of cement, 3% of bituminous emulsion (2C3E)
• 1.5% of cement, 3.5% of bituminous emulsion, 2% of mineral filler (1.5C3.5E2F)
The optimum water content was fixed for each mixture in a previous study developed in
laboratory.
Advanced Materials Research Vol. 723 1047

6. Sample of CBTM were taken during the construction of the trial section after the mixing phase
carried out by the recycler (samples were taken behind the recycler) and immediately compacted by
means of a SGC.
Specimens were subjected to different curing periods (24, 48 and 72 hours at 40°C) and
conditioned 4 hours at 25°C before testing. The average values of ITS (EN 12697-23) for each
mixture are shown in Table 5.
On the basis of a cost analysis and resistance values, two mixtures were selected for a further
evaluation considering also UCS and indirect tensile stiffness modulus (ITSM, EN 12697-26):
2C3E2F and 2C3E.
Table 5 Mean ITS values for all CBTM series
ITS [N/mm2
]
Mixture Curing period [hours]
24 48 72
3C2.5E2F 0.23 0.27 0.50
2C3E2F 0.24 0.27 0.41
2C3E - - 0.38
1.5C3.5E2F 0.23 0.24 0.36
Specifications [N/mm2
] - - > 0.35
From the results shown in Table 6, it can be affirmed that both mixtures allow the technical
specifications to be satisfied. However, the mixture containing 100% RA treated with 2% of cement
and 3% of bituminous emulsion was the most cost-effective solution and was selected as design
mixture.
Table 6 Mean mechanical characteristics of the selected CBTM series
Mixture UCS [N/mm2
] ITS [N/mm2
] ITSM [MPa]
2C3E2F 2.90 0.37 3700
2C3E 2.44 0.37 3200
Specifications [N/mm2
] - > 0.35 > 3000
The recycling train was made up of a vehicle equipped with volumetric batchers for spreading
cement, a recycler coupled to a tank truck for the addition of water and a tank truck for addition of
bituminous emulsion, a vibrating smooth drum roller, a pneumatic tyre roller and a grader for
shaping and levelling. Excess material was bladed from the road to ensure that final levels were
respected. Mechanical brooms were used for sweeping loose material from the surface prior to
placing the tack coat.
Fig. 3 shows the application of in situ recycling using bituminous emulsion and cement. To seep
up the construction phases two parallel recycling trains were used.
Fig. 3 CBTM production for the subbase course
1048 Innovation and Sustainable Technology in Road and Airfield Pavement

7. In situ verification by means of falling weight deflectomer
The pavement structure was verified by means of non-destructive in-situ measurements with a
falling weight deflectomer (FWD).
FWD measurements were carried out on two longitudinal rows, respectively -5 m and +5 m from
the center line, considering a testing station every 50 m. The FWD survey was performed after 90
days curing period in order to evaluate the definitive performance of the material employed.
The deflection data were statistically analyzed using the cusum technique [15] in order to
determine the homogeneous sub-sections (Fig. 4).
-1400
-1200
-1000
-800
-600
-400
-200
0
0,000 0,500 1,000 1,500 2,000 2,500
Cusum
value
Distance [km]
RWY 07 / 25 : + 5m
Sub-section from [m] to [m]
1 3 149
2 198 398
3 452 754
4 802 2220
-1400
-1200
-1000
-800
-600
-400
-200
0
0,000 0,500 1,000 1,500 2,000 2,500
Cusum
value
Distance [km]
RWY 07 / 25 : -5 m
Sub-section from [m] to [m]
1 25 374
2 422 1074
3 1119 1275
4 1328 2220
Fig. 4 Determination of the homogeneous sub-section using the cusum technique
The backcalculation was performed through the BAKFAA software [15]. For bituminous
mixtures, the calculated moduli, referring to the field temperature during testing (32°C), were
shifted at the reference temperature of 20°C using temperature dependent laws:
( )
2
00007404
.
0
006447
.
0
53658
.
6
10
:
]
17
[ T
T
HMA
E
HMA
for ⋅
−
⋅
−
= (1)
[ ] ( ) ( ) ( )
0
0082
.
0
0
10
:
1 T
T
CBTM
CBTM
T
E
T
E
CBTM
for −
⋅
⋅
= (2)
where EHMA is the elastic modulus of HMA at the temperature T, E(T0)CBTM is the elastic modulus
of CBTM at the reference temperature T0 (20°C), E(T)CBTM is the elastic modulus of CBTM at the
testing temperature T (32°C).
The average values of the elastic modulus for each layer are reported in Table 7.
The overall results complied with the reference values used in the design calculation of the
pavement structure.
Advanced Materials Research Vol. 723 1049

8. Table 7 Average elastic modulus for each layers
RW07/25: +5 m Elastic modulus, 20°C [MPa]
Sub-section from [m] to [m] E1, HMA E2, CBTM E3, subbase E4, foundation E5, subgrade
1 3 149 2705 3940 5685 635 301
2 198 398 4657 3247 6105 1160 300
3 452 754 3760 2471 4520 779 281
4 802 2220 4725 3507 6753 1022 326
RW07/25: -5 m Elastic modulus, 20°C [MPa]
Sub-section from [m] to [m] E1, HMA E2, CBTM E3, subbase E4, foundation E5, subgrade
1 25 374 3295 3049 8003 708 319
2 422 1074 4718 3758 9055 1129 341
3 1119 1275 2903 2270 5631 683 286
4 1328 2220 5057 3847 9618 1022 349
Conclusions
The direct reuse of demolition materials has been studied for several years and, considering
economical, technical and environmental advantages, has became one of the most attractive
alternatives for road construction and rehabilitation.
This paper shows the application in airfield of scientific knowledge and practical experiences on
pavement recycling developed in Italy for road maintenance projects. Indeed, the rehabilitation of
the runway of the Treviso airport involved a huge amount of reclaimed materials, in detail: about
40,000 m3
of RA, 52,000 m3
of CCC and 13,600 m3
of granular material. Several recycling
techniques, such as the cement stabilization of soil, cement treatment of milled cement concrete and
cement-bitumen treatment of reclaimed asphalt, were used. All recycled mixtures were tested in
laboratory, however, the in situ experimentation by mean of trial sections was essential to validate
the mechanical performance of mixtures and to determine the construction phases. The verification
of the overall pavement structure through non-destructive in-situ measurements with FWD
established the definitive compliance to the design parameters.
Acknowledgements
The Authors wish to thank AER TRE S.p.A. and the SAVE Group that allow the publication and
support the rehabilitation project of the Airport of Treviso. Moreover, special thanks go to Davide
Drago for his role of surveillance officer on behalf of Italian Authority for Civil Aviation (ENAC).
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Advanced Materials Research Vol. 723 1051
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