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31 AUGUST - 4 SEPTEMBER 2020 | UNIVERSITY OF SHEFFIELD, SHEFFIELD, UNITED KINGDOM | 1
Novel capsules for asphalt self-healing containing bio-oil from
biomass waste
Jose Norambuena-Contreras1*, Rodrigo Briones2, Luis E. Arteaga-Pérez3, Irene Gonzalez-Torre1
1 LabMAT, Department of Civil and Environmental Engineering, University of Bío-Bío, Concepción, Chile.
2 CIPA, Centro de Investigación de Polímeros Avanzados, Avenida Collao 1202, Edificio de Laboratorios, Concepción, Chile.
3 LPTC, Laboratory on Thermal and Catalytic Processes, Department of Wood Engineering, University of Bío-Bío, Chile.
* Email(s): jnorambuena@ubiobio.cl
ABSTRACT
This paper presents the synthesis and characterization of biopolymeric capsules for asphalt self-healing, where
bio-oil from liquefied agricultural biomass waste was used as an eco-friendly rejuvenating agent for asphalt
materials. Bio-oil polymeric capsules were synthesized using simple dripping technique by syringe pump device,
where the bio-oil was encapsulated by ionic gelation in a polysaccharide polymer matrix of sodium alginate.
Morphology, thermal stability, mechanical and physical-chemical properties of bio-oil capsules and their
components were evaluated. Self-healing efficiency of the bio-oil as rejuvenating agent in cracked bitumen samples
was quantified by fluorescence microscopy techniques. Main results proven that the bio-oil can be diffused in the
bitumen samples reducing their viscosity and consequently healing the open microcracks.
1. INTRODUCTION
Asphalt self-healing by encapsulated rejuvenating
agents is a revolutionary and sustainable technology
for the autonomous crack-healing of asphalt
pavements 0. When damage occurs in an asphalt
material containing embedded capsules, open
microcracks appear and eventually propagate until
they reach and break a capsule releasing the
contained rejuvenating agents, which reduces the
viscosity of aged bitumen by diffusion, allowing it to
flow through the cracks, sealing them autonomously.
Authors have successfully synthetized and proven the
use of numerous encapsulated rejuvenating agents,
such as dense aromatic oil, waste cooking oil, and
sunflower-cooking oil with asphalt self-healing
purposes. This study explores the use of bio-oil from
liquefied agricultural biomass waste as a bio-based
encapsulated rejuvenating agent for asphalt self-
healing 0.
2. MATERIALS AND METHODS
The polymeric structure of the capsules was prepared
of low-viscosity grade sodium alginate and calcium-
chloride dihydrate. Bio-oil (BO) used as a bio-based
rejuvenating agent for asphalt self-healing, and virgin
bitumen were used to quantify the BO healing
efficiency. Bio-oil capsules were prepared by cross-
linking of sodium alginate in the presence of Ca2+ ions
through external ionic gelation process. The
preparation of the BO capsules by pressure pump
method and with an alginate content of 2% w/v of water
consisted of 5 steps described in 0. Additionally, the
morphology of BO capsules was characterized by their
size, surface aspect and internal microstructure by
Optical and Scanning Electron Microscopy,
respectively. The chemical structure of BO capsules
and bio-oil was characterized by Attenuated-Total
Reflection Infrared (ATR-IR) spectroscopy.
Thermogravimetric analysis (TGA-DGT) was carried
out to evaluate the thermal stability of BO capsules and
their components. Compressive strength of the BO
capsules was measured on 10 individual samples
loaded until failure at a loading rate of 0.2 mm/min. The
self-healing efficiency of the bio-oil as rejuvenating
agent of asphalt was quantified in cracked bitumen
samples by fluorescence microscopy 0.
3. RESULTS AND DISCUSSION
BO capsules (Figure 1) showed regular spherical size,
with a dense membrane in their surface, but without
the usual polynuclear formation and internal
multicavity “egg-box” formed by external ionic gelation,
which suggests that bio-oil chemically affects the
encapsulating process increasing the cross-linking
process of the alginate matrix, producing capsules with
a denser and more rigid membrane and polymer
matrix. Regardless the limited microporous structure
showed by capsules, they presented an encapsulation
efficiency of bio-oil of 78±5%. Besides, SEM-EDS
characterization revealed a rough texture on the
capsule surface with an element composition of Ca
(56.43%) and Na (43.57%). BO capsule size can be
fitted to the log-normal probability distribution (P-value
0.922 given by K-S test), with an average size of 1.37
mm (SD = 0.14 mm). The relative density of BO
capsules was 1.499 g/cm3 (SD = 0.007 g/cm3).
Moreover, the chemical characterization by ATR-IR
revealed that the bio-oil obtained by liquefaction of
corn stover residues has strong antioxidant properties
provided by carboxylic acids, phenolics and, in less
extent, ketone functionalities. TGA results of BO
capsules and their components were in concordance
with the bio-oil spectrum FTIR and allow suggesting
that encapsulation process of bio-oil as rejuvenating
agent leads to a thermally stable material with potential
to be used for asphalt self-healing applications.
Additionally, BO capsules presented an elastic-plastic
mechanical behaviour with moderate ductility and
breakage in plastic deformation, recording an average
compressive force of 23.56 N (SD = 8.24 N) and a
displacement of 0.16 mm. Finally, it was proven that
bio-oil has a healing efficiency close to 50% at a time
of 120 min of evaluation, showing a linear evolution
with the healing time. Bio-oil can dissolve the bitumen
on both sides of the crack, increasing the content of
viscous components of asphalts and decreasing the
viscosity of bitumen, which allows it to flow over time
healing its open crack.
31 AUGUST - 4 SEPTEMBER 2020 | UNIVERSITY OF SHEFFIELD, SHEFFIELD, UNITED KINGDOM | 1
Figure 1. BO capsules for asphalt self-healing. (a) Bio-oil from liquefied agricultural biomass waste; (b) Individual bio-oil
capsule; (c) Compressive strength on the BO capsules; and (d) Crack-healing results.
4. CONCLUSIONS
Novel bio-oil capsules presented an adequate
morphology for the asphalt self-healing application,
with a good thermal stability and physical-chemical
properties. It was also proven that the bio-oil can be
diffused in the bitumen samples reducing their
viscosity and consequently healing the open
microcracks.
5. ACKNOWLEDGEMENTS
The authors thank the funding given by the ANID from
Chile through the Project FONDECYT 1190027 and
the testing support given by Dr. Andrea Guadarrama-
Lezama (UAMEX) and Dr. Juan F. Vivanco (UAI).
6. REFERENCES
[1] Gonzalez-Torre I, Norambuena-Contreras J
(2020) Recent advances on self-healing of bituminous
materials by the action of encapsulated rejuvenators.
Constr Build Mater 258, 119568.
https://doi.org/10.1016/j.conbuildmat.2020.119568
[2] Norambuena-Contreras J, Arteaga-Perez LE,
Guadarrama-Lezama AY, Briones R, Vivanco JF,
Gonzalez-Torre I (2020) Microencapsulated bio-based
rejuvenators for the self-healing of bituminous
materials. Materials 13,1446.
https://doi.org/10.3390/ma13061446
.
1 mm
(b)
Bio-oil capsule
(a)
Bio-oil
Compressive
test on capsule
(c)
100 µm
Diffused
bio-oil
µ-crack
Bitumen
120 min
µ-crack
(d)