THIS STUDY AIMED TO CHARACTERISE POLYNUCLEAR BIOCAPSULES CONTAINING LOW-COST REJUVENATING AGENTS FOR ASPHALT SELF-HEALING. CAPSULES CONSISTED OF A BIOPOLYMERIC MATRIX OF CALCIUM ALGINATE CONTAINING COOKING OIL AND MINERAL OIL AS REJUVENATING AGENTS, BEING SYNTHESISED USING IONIC GELATION THROUGH THE PUMPING DRIPPING TECHNIQUE. THE PHYSICAL-CHEMICAL PROPERTIES OF THE OIL-IN-BIOPOLYMER EMULSIONS AND THEIR STABILITY OVER TIME WERE STUDIED. THE MORPHOLOGICAL AND THERMOPHYSICAL PROPERTIES OF THE BIOCAPSULES, AS WELL AS THE ENCAPSULATION EFFICIENCY OF THE REJUVENATING AGENTS, WERE QUANTIFIED AND CHARACTERISED BY MICROSCOPIC TECHNIQUES AND LABORATORY TESTS. MAIN RESULTS SHOWED THAT EMULSIONS SHOULD BE USED FOR ENCAPSULATION PURPOSES WITHIN A PERIOD NO LONGER THAN 3H, REDUCING THE EFFECT OF INSTABILITY PHENOMENA. BESIDES, THE BIOPOLYMER-BASED POLYNUCLEAR CAPSULES PRESENTED UNIFORM SIZE, INTERNAL MULTICAVITY MICROSTRUCTURE RESULTING IN HIGH ENCAPSULATION EFFICIENCIES AND THERMAL STABILITY AT HIGH TEMPERATURES, PROVING THAT COOKING OIL AND MINERAL OIL CAN BE POTENTIALLY USED AS LOW-COST REJUVENATING AGENTS AND THERMALLY STABLE ADDITIVES FOR ASPHALT SELF-HEALING PURPOSES.

THIS STUDY EVALUATED THE EFFECT OF TWO ENCAPSULATION METHODS (I.E., DROPPING FUNNEL AND SYRINGE PUMP), TWO CONCENTRATIONS OF THE ALGINATE-BASED ENCAPSULATING MATERIAL (2%, AND 3%), AND THREE OILS AS BITUMEN REJUVENATORS (VIRGIN SUNFLOWER OIL, WASTE COOKING OIL, AND VIRGIN ENGINE OIL) ON THE MORPHOLOGICAL, PHYSICAL, CHEMICAL, THERMAL, AND MECHANICAL PROPERTIES OF ENCAPSULATED REJUVENATORS FOR ASPHALT SELF-HEALING PURPOSES. A GENERAL FACTORIAL DESIGN 2 × 2 × 3 WAS PROPOSED TO DESIGN 12 DIFFERENT CA-ALGINATE CAPSULES. SIGNIFICANT DIFFERENCES ON THE MORPHOLOGICAL, PHYSICAL, AND MECHANICAL PROPERTIES OF THE CAPSULES WERE ANALYSED BY THREE-WAY ANOVA AND TUKEY HSD POST HOC ANALYSES. THE EFFECT OF THE TYPE OF OIL ON THE SELF-HEALING CAPACITY OF CRACKED BITUMEN SAMPLES WAS ALSO EVALUATED. THE MAIN RESULTS SHOWED THAT THE DESIGN PARAMETERS AND THEIR INTERACTIONS SIGNIFICANTLY AFFECTED THE MORPHOLOGICAL, PHYSICAL, AND MECHANICAL PROPERTIES OF THE CAPSULES. CAPSULES SYNTHESISED VIA SYRINGE PUMP METHOD, WITH VIRGIN COOKING OIL AND 2% ALGINATE WAS THE MOST APPROPRIATE FOR ASPHALT SELF-HEALING PURPOSES SINCE ITS UNIFORM MORPHOLOGY, ENCAPSULATION EFFICIENCY UP TO 80%, THERMAL DEGRADATION BELOW 5% WT., AND COMPRESSIVE STRENGTH ABOVE THE REFERENCE ASPHALT COMPACTION LOAD OF 10 N. FINALLY, THE HEALING TESTS SHOWED THAT VIRGIN COOKING OIL CAN BE POTENTIALLY USED AS A REJUVENATOR TO PROMOTE ASPHALT CRACK-HEALING.

A SYSTEMATIC STUDY ON THE USE OF NOBLE METALS (PD, PT, AU) SUPPORTED ON TITANATE NANOTUBES (NT-TI) FOR SELECTIVELY PRODUCING BTX AND P-CYMENE FROM WASTE TIRE PYROLYSIS IS PROVIDED HERE. ALL THE MATERIALS WERE CHARACTERIZED FOR CHEMICAL, TEXTURAL AND STRUCTURAL PROPERTIES USING A RANGE OF ANALYTICAL TECHNIQUES. THE M/NT-TI (M: PD, PT, OR AU) CATALYSTS EXHIBIT LOW NANOPARTICLE SIZES (1.8 SUPPORT > NON-CATALYST. THE PY-GC/MS SUGGEST THAT THE CATALYSTS PARTICIPATE IN THE SECONDARY REACTIONS OF DEALKYLATION, DEHYDROGENATION, ISOMERIZATION, AROMATIZATION, AND CYCLIZATION LEADING TO A HIGHER FORMATION OF BTX THAN THE UNCATALYZED REACTION. FINALLY, A COMPREHENSIVE REACTION PATHWAY DESCRIBING THE CATALYTIC PYROLYSIS OF WT OVER PD/NT-TI WAS PROPOSED BY STUDYING THE CATALYTIC PYROLYSIS OF INDIVIDUAL POLYMERS CONSTITUTING THE WASTE TIRES, AND D,L-LIMONENE.

ENCAPSULATED REJUVENATING AGENTS FOR SELF-HEALING OF BITUMINOUS MATERIALS HAVE GAINED SIGNIFICANT INTEREST WITHIN THE ROAD SCIENTIFIC COMMUNITY, TURNING THESE ENHANCED MATERIALS INTO A HOT TOPIC. IN THIS STUDY, VIRGIN COOKING OIL, WASTE COOKING OIL, AND VIRGIN ENGINE OIL WERE USED AS ENCAPSULATED REJUVENATORS TO RESTORE PROPERTIES OF AGED BITUMEN AND THEIR CAPACITY FOR ASPHALT SELF-HEALING. THE ALGINATE-BASED CAPSULES AND THEIR COMPONENTS WERE CHARACTERISED BY CHEMICAL, PHYSICAL, MORPHOLOGICAL, THERMAL STABILITY, AND MECHANICAL TESTS. SELF-HEALING RECOVERY TESTS OF CRACKED LONG-TERM AGED BITUMEN BY THE EFFECT OF OIL RELEASE WERE ALSO PERFORMED. MAIN RESULTS SHOWED THAT ALL REJUVENATING OILS PRESENTED FUNCTIONAL GROUPS CONTRIBUTING TO THE CHEMICAL RESTORATION OF AGED BITUMEN. ENCAPSULATION OF STABLE O/W EMULSIONS WAS ACHIEVED. CAPSULES PRESENTED UNIFORM SIZE, MULTICAVITY MICROSTRUCTURE, HIGH ENCAPSULATION EFFICIENCY, THERMAL AND MECHANICAL STABILITY. FINALLY, ALL REJUVENATING OILS WERE SUCCESSFULLY DIFFUSED INTO AN AGED BITUMEN, ALTHOUGH VIRGIN COOKING OIL PRESENTED THE HIGHEST HEALING CAPACITY.

THIS PAPER AIMS TO EVALUATE THE INFLUENCE OF THE MICROWAVE HEATING TIME ON THE SELF-HEALING PROPERTIES OF FIBRE-REINFORCED ASPHALT MIXTURES. TO THIS PURPOSE, SELF-HEALING PROPERTIES OF DENSE ASPHALT MIXTURES WITH FOUR DIFFERENT PERCENTAGES OF STEEL WOOL FIBRES WERE EVALUATED AS THE THREE-POINT BENDING STRENGTH BEFORE AND AFTER HEALING VIA MICROWAVE HEATING AT FOUR DIFFERENT HEATING TIMES. FURTHERMORE, THE THERMAL BEHAVIOUR OF ASPHALT MIXTURES DURING MICROWAVE HEATING WAS ALSO EVALUATED. WITH THE AIM OF QUANTIFYING THE EFFICIENCY OF THE REPAIR PROCESS, TEN DAMAGE-HEALING CYCLES WERE DONE IN THE TEST SAMPLES. IN ADDITION, SELF-HEALING RESULTS WERE COMPARED WITH THE FIBRE SPATIAL DISTRIBUTION INSIDE ASPHALT SAMPLES EVALUATED BY CT-SCANS. CRACK-SIZE CHANGE ON ASPHALT SAMPLES DURING HEALING CYCLES WAS ALSO EVALUATED THROUGH OPTICAL MICROSCOPY. IT WAS FOUND THAT THE HEATING TIME IS THE MOST INFLUENTIAL VARIABLE ON THE HEALING LEVEL REACHED BY THE ASPHALT MIXTURES TESTED BY MICROWAVE RADIATION. CT-SCANS RESULTS PROVED THAT FIBRE SPATIAL DISTRIBUTION INTO THE ASPHALT MIXTURES PLAY AN IMPORTANT ROLE IN THE ASPHALT HEALING LEVEL. FINALLY, IT WAS CONCLUDED THAT 40 S WAS THE OPTIMUM HEATING TIME TO REACH THE HIGHEST HEALING LEVELS WITH THE LOWEST DAMAGE ON THE ASPHALT SAMPLES, AND THAT HEATING TIMES OVER 30 S CAN SEAL THE CRACKS, THUS ACHIEVING THE SELF-HEALING OF ASPHALT MIXTURES VIA MICROWAVE HEATING.

ASPHALT SELF-HEALING BY ENCAPSULATED REJUVENATING AGENTS IS CONSIDERED A REVOLUTIONARY TECHNOLOGY FOR THE AUTONOMIC CRACK-HEALING OF AGED ASPHALT PAVEMENTS. THIS PAPER AIMS TO EXPLORE THE USE OF BIO-OIL (BO) OBTAINED FROM LIQUEFIED AGRICULTURAL BIOMASS WASTE AS A BIO-BASED ENCAPSULATED REJUVENATING AGENT FOR SELF-HEALING OF BITUMINOUS MATERIALS. NOVEL BO CAPSULES WERE SYNTHESIZED USING TWO SIMPLE DRIPPING METHODS THROUGH DROPPING FUNNEL AND SYRINGE PUMP DEVICES, WHERE THE BO AGENT WAS MICROENCAPSULATED BY EXTERNAL IONIC GELATION IN A BIOPOLYMER MATRIX OF SODIUM ALGINATE. SIZE, SURFACE ASPECT, AND ELEMENTAL COMPOSITION OF THE BO CAPSULES WERE CHARACTERIZED BY OPTICAL AND SCANNING ELECTRON MICROSCOPY AND ENERGY-DISPERSIVE X-RAY SPECTROSCOPY. THERMAL STABILITY AND CHEMICAL PROPERTIES OF BO CAPSULES AND THEIR COMPONENTS WERE ASSESSED THROUGH THERMOGRAVIMETRIC ANALYSIS (TGA-DTG) AND FOURIER-TRANSFORM INFRARED SPECTROSCOPY (FTIR-ATR). THE MECHANICAL BEHAVIOR OF THE CAPSULES WAS EVALUATED BY COMPRESSIVE AND LOW-LOAD MICRO-INDENTATION TESTS. THE SELF-HEALING EFFICIENCY OVER TIME OF BO AS A REJUVENATING AGENT IN CRACKED BITUMEN SAMPLES WAS QUANTIFIED BY FLUORESCENCE MICROSCOPY. MAIN RESULTS SHOWED THAT THE BO CAPSULES PRESENTED AN ADEQUATE MORPHOLOGY FOR THE ASPHALT SELF-HEALING APPLICATION, WITH GOOD THERMAL STABILITY AND PHYSICAL-CHEMICAL PROPERTIES. IT WAS ALSO PROVEN THAT THE BO CAN DIFFUSE IN THE BITUMEN REDUCING THE VISCOSITY AND CONSEQUENTLY SELF-HEALING THE OPEN MICROCRACKS.

EXTRINSIC SELF-HEALING OF BITUMINOUS MATERIALS USING ENCAPSULATED REJUVENATORS IS A HOT TOPIC WITHIN ROAD MATERIALS. BASED ON A CIRCULAR ECONOMY VISION FOR MORE SUSTAINABLE AND RESILIENT ASPHALT PAVEMENTS, THIS STUDY EXPLORES FOR THE FIRST TIME THE USE OF PYROLYTIC OIL FROM WASTE TYRES AS A PROMISING ENCAPSULATED REJUVENATOR TO PROMOTE THE EXTRINSIC SELF-HEALING IN BITUMINOUS MATERIALS. PYROLYTIC OIL-IN-WATER EMULSIONS, AND CAPSULES AND THEIR COMPONENTS WERE PRODUCED AND CHARACTERISED THROUGH GAS CHROMATOGRAPHY-MASS SPECTROMETRY (GC/MS) AND SARA FRACTIONS ANALYSIS, FLUORESCENCE MICROSCOPY METHODS, CREAMING INDEX, THERMOGRAVIMETRIC ANALYSIS (TGA-DGT), OPTICAL AND SCANNING ELECTRON MICROSCOPY (SEM), ENCAPSULATION EFFICIENCY AND MECHANICAL PROPERTIES. MAIN RESULTS SHOWED THAT THE PYROLYTIC OIL CAPSULES PRESENTED AN ADEQUATE MORPHOLOGY FOR THE SELF-HEALING ASPHALT, WITH A GOOD THERMAL STABILITY, PHYSICAL?CHEMICAL AND MECHANICAL PROPERTIES. OVERALL, IT WAS ALSO PROVEN THAT THE PYROLYTIC OIL IS A REJUVENATOR THAT CAN DIFFUSE IN THE AGED BITUMEN REDUCING ITS VISCOSITY TO PROMOTE THE SELF-HEALING OF THE MICROCRACKS.

SELF-HEALING OF BITUMINOUS MATERIALS REPRESENTS NOWADAYS A PROMISING APPROACH TO INCREASING THE LIFESPAN OF ASPHALT PAVEMENTS. DURING THE LAST DECADE, DIFFERENT TECHNIQUES HAVE BEEN USED BY RESEARCHERS TO PROMOTE THE SELF-HEALING CAPABILITY OF BITUMINOUS MATERIALS: CRACK-HEALING BY EXTERNALLY TRIGGERED HEATING USING MAGNETIC FIELD TECHNOLOGIES, SUCH AS INDUCTION HEATING AND MICROWAVE RADIATION, AND, MORE RECENTLY, THE USE OF EMBEDDED ENCAPSULATED REJUVENATORS TO ACTIVATE CRACK-HEALING THROUGH THE RECOVERY OF THE ORIGINAL PROPERTIES OF BITUMEN. DURING RECENT YEARS, RESEARCHERS HAVE MAINLY FOCUSED THEIR EFFORTS ON PROMOTING THE AUTONOMIC HEALING OF BITUMINOUS MATERIALS BY THE ACTION OF ENCAPSULATED REJUVENATING AGENTS. THIS ARTICLE PRESENTS AN EXTENSIVE AND CRITICAL LITERATURE REVIEW OF THE PROCESSES OF AGEING, RECOVERING AND SELF-HEALING OF BITUMINOUS MATERIALS, FOCUSING ON THE USE OF REJUVENATING AGENTS TO EXTEND THE LIFE OF PAVEMENTS. THEREFORE, THE DIFFERENT TYPES AND TECHNIQUES TO ENCAPSULATE REJUVENATORS, THEIR EVOLUTION OVER THE YEARS, AND THEIR MAIN APPLICATIONS IN BITUMINOUS MATERIALS WERE ANALYSED FROM A MULTISCALE APPROACH. FINALLY, BASED ON THE CURRENT TRENDS IN MATERIALS ENGINEERING, THIS ARTICLE PROPOSES ADVANCES AND INNOVATIONS TO IMPROVE THE FUTURE RESEARCH IN THE FIELD OF ENCAPSULATED REJUVENATORS TO PROMOTE ASPHALT SELF-HEALING, FROM A MORE SUSTAINABLE POINT OF VIEW.

THIS PAPER PRESENTS THE SYNTHESIS AND CHARACTERISATION OF BIOPOLYMERIC CAPSULES FOR ASPHALT SELF-HEALING. A SODIUM ALGINATE BIOPOLYMER EXTRACTED FROM THE CELL WALL OF BROWN ALGAE WAS USED AS THE ENCAPSULATING MATERIAL TO CONTAIN WASTE COOKING OIL (WCO) AS A POTENTIAL ENCAPSULATED REJUVENATING AGENT FOR AGED BITUMEN. POLYNUCLEAR CAPSULES WERE SYNTHESISED BY IONIC GELATION. THE SIZE, SURFACE ASPECT AND INTERNAL STRUCTURE OF THE WCO CAPSULES WERE EVALUATED USING OPTICAL AND SCANNING ELECTRON MICROSCOPY. THE PHYSICAL-CHEMICAL PROPERTIES AND THERMAL STABILITY OF THE WCO CAPSULES AND THEIR COMPONENTS WERE ALSO EVALUATED. MOREOVER, THE DIFFUSION PROCESS AND SELF-HEALING CAPABILITY OF THE RELEASED WCO ON CRACKED BITUMEN TEST SAMPLES WERE DETERMINED BY IMAGE ANALYSIS THROUGH FLUORESCENCE MICROSCOPY. THE MAIN RESULTS OF THIS STUDY SHOWED THAT THE WCO CAPSULES PRESENTED A SUITABLE MORPHOLOGY TO BE MIXED IN ASPHALT MIXTURES. WCO CAPSULES AND THEIR COMPONENTS PRESENTED MECHANICAL AND THERMAL STABILITY AND PHYSICAL-CHEMICAL PROPERTIES WHICH SUGGEST THEIR FEASIBILITY FOR SELF-HEALING APPLICATIONS. IT WAS PROVEN THAT THE ENCAPSULATED WCO CAN DIFFUSE IN THE AGED BITUMEN, REDUCING ITS VISCOSITY AND PROMOTING THE SELF-HEALING OF MICROCRACKS.