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Mineral filler characteristics and non-Newtonian viscosity of asphalt mastic at high temperature: A response surface methodology approach
(2026-12-01)
Chamwon, Suwaphit
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Hutabarat, Multazam
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Chaturabong, Preeda
Asphalt mastic—composed of asphalt binder and mineral filler—strongly governs the high-temperature viscosity of asphalt concrete during mixing and compaction. This study investigates the effects of four mineral fillers (granite, limestone, shale, and pumice) on the viscosity and flow behavior of asphalt mastics at elevated temperatures (130–170 °C). Comprehensive filler characterization was performed, encompassing morphological analysis by scanning electron microscopy (SEM), physical property evaluation (particle density, specific surface area, and Rigden voids), hydrophilic coefficient determination, particle size distribution by laser diffraction, and mineralogical identification by X-ray diffraction (XRD). Response surface methodology (RSM) with a central composite design (CCD) was employed to model the combined effects of temperature (130–170 °C), filler content (5–30% by volume), and rotational speed (10–30 RPM) on apparent viscosity measured by a Brookfield rotational viscometer. The non-Newtonian index, derived from the power-law (Ostwald–de Waele) model, was used to classify flow behavior. Results demonstrate that temperature and filler content are the dominant parameters governing viscosity, while rotational speed controls the degree of non-Newtonian behavior in a filler-dependent manner. A critical transition from quasi-Newtonian to pronounced non-Newtonian flow was identified at 15–20% filler content by volume, coinciding with a sharp increase in the effective solid volume fraction that approaches the colloidal packing threshold (φ* ≈ 32–34%). Pumice exhibited the strongest shear-thickening (n up to 1.22) while granite showed consistent shear-thinning (n ≈ 0.88–0.94), with limestone and shale showing mixed behavior. Pumice and shale produced the strongest viscosity stiffening, consistent with greater binder immobilization due to their higher Rigden voids. AASHTO T316 workability analysis indicates that under base-binder conditions, the maximum filler content within practical mixing limits at 160 °C is approximately 30% for granite and limestone but only ∼22% for pumice. The validated quadratic RSM models (R² = 0.84–0.96) provide a practical framework for optimizing filler selection and processing temperatures in asphalt mixture design.
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Rheological, adhesive, and chemical characterization of asphalt mastic modified with spent coffee grounds: A comparative study with limestone filler
(2026-06-01)
Thairueng, Manita
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Chamwon, Suwaphit
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Hutabarat, Multazam
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Chaturabong, Preeda
Spent coffee grounds (SCG) were evaluated as an organic filler in asphalt mastic at 10 %, 15 %, and 20 % by volume, benchmarked against limestone (LM). The experimental program combined DSR temperature sweeps, pull-off adhesion tests on basalt, granite, and marble substrates, SARA fractionation, and SEM, performed under fresh, RTFOT-aged, and PAV-aged conditions. At 20 wt% replacement, SCG reduced the complex shear modulus G* from 3637 to 2885 kPa at 16 °C (−21 %) and lowered the isostiffness temperature from 31.22 °C to 25.43 °C after PAV aging (−5.79 °C), while limestone at 20 wt% raised G* to 6461 kPa (+78 %). The rutting factor G*/sinδ decreased by 19–23 % with SCG and increased by 71–80 % with LM at 64 °C, whereas the fatigue factor G*sinδ at 25 °C dropped by 18–22 % with SCG, indicating improved fatigue resistance potential. Limestone mastics exhibited 25–83 % higher pull-off force than SCG ( p < 0.05, all 18 comparisons, Benjamini–Hochberg-corrected), yet SCG mastics maintained moisture retention of 83–97 % on basalt, comparable to LM (75–97 %). Failure mode analysis showed all mastics cohesive under dry conditions, with SCG transitioning to adhesive failure under moisture exposure (notably at 15–20 % SCG on marble and granite after PAV aging). SARA analysis confirmed aromatics rose from 60.6 % to 65.7 % and asphaltenes fell from 10.7 % to 8.2 % with increasing SCG, yielding an Instability Colloidal Index decrease from 0.187 to 0.154. These results establish SCG not as a direct limestone substitute but as a complementary modifier suited to fatigue-prone warm-climate binder courses and hybrid SCG–LM filler blends, offering environmental benefits through agricultural waste valorization.
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Rheological Performance of Asphalt Mastics Incorporating Shale and Pumice as Alternative Mineral Fillers
(2026-05-01)
Chamwon, Suwaphit
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Hutabarat, Multazam
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Chaturabong, Preeda
This study investigates the hypothesis that mineral fillers with distinct surface characteristics, mineralogical compositions, and morphologies exhibit different reinforcement mechanisms in asphalt mastics. Shale and pumice were evaluated as alternative mineral fillers and compared with conventional granite and limestone at 20% and 30% filler-to-asphalt (F/A) ratios by volume. Filler characterization included X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), specific surface area (SSA), and hydrophilicity coefficient (HC) measurements. Rheological characterization was performed using dynamic shear rheometer, including temperature sweep, frequency sweep master curves, multiple stress creep recovery (MSCR), linear amplitude sweep (LAS), and Glover–Rowe (G–R) analyses. Pumice, dominated by amorphous volcanic glass with the highest SSA (59.18 m²/g), exhibited rutting-dominant modification with the highest complex modulus enhancement (7.3–9.4 times at 30% F/A) and lowest non-recoverable creep compliance. Shale, composed primarily of quartz and kaolinite with layered morphology and moderate SSA (43.00 m²/g), demonstrated balanced rheological response and achieved the longest fatigue life (Nf,5% = 45,200 cycles at 20% F/A). These findings demonstrate that filler-specific reinforcement mechanisms are governed by mineralogical composition and morphology, supporting performance-based filler selection tailored to climatic and loading conditions.
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Advanced characterization of bio-rejuvenated asphalt systems using agricultural waste pyrolytic oils: Integrated assessment of chemical composition, rheological, and aging performance
(2026-04-04)
Hutabarat, Multazam
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Chamwon, Suwaphit
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Chaturabong, Preeda
Reclaimed asphalt pavement (RAP) requires rejuvenation to restore binder flexibility lost due to oxidative aging. This study evaluated sugarcane bagasse oil (SBO) and rice straw oil (RSO) as bio-rejuvenators using an integrated chemical (GC–MS, FTIR), rheological (master curves), and mechanical (LAS fatigue) framework. GC–MS confirmed distinct feedstock chemistries—SBO enriched with methoxy-phenolics and aromatics, and RSO dominated by catechol, nitrogenous species, and oxygenated sugars—suggesting different rejuvenation pathways. FTIR results showed reduced sulfoxide index (SI) in fresh rejuvenated binders, indicating dilution of S O groups; however, changes in carbonyl index (CI) largely reflected the inherent bio-oil composition rather than true oxidative reversal. Several FTIR indicators therefore contrasted with rheological and fatigue behavior, demonstrating that chemical indices alone cannot fully describe rejuvenation or aging progression. Rheological master curves and LAS testing provided the decisive evidence of performance. Fresh rejuvenated binders exhibited substantial stiffness reduction and improved relaxation, with optimum dosages of ≈ 15% SBO and 10–15% RSO achieving 2–5 × higher fatigue life than aged binder at moderate to high strains. Following secondary aging (P-series), rejuvenation benefits were substantially diminished, with fatigue performance returning to aged-binder levels at most strain ranges. Only minimal-dosage formulations (5% SBO) demonstrated statistically significant protection against unprotected secondary aging (2AB, p < 0.05), while moderate-to-high dosages (10–20%) showed equivalent or inferior performance. FTIR indices revealed reduced sulfoxide formation in all P-series binders compared to 2AB, suggesting partial oxidation mitigation through alternative carbonyl-forming pathways, though this chemical protection did not translate to sustained mechanical performance. Thus, while hypotheses on feedstock-dependent chemistry and dose–response behavior were validated, sustained antioxidant protection from phenolics was only partially supported. In conclusion, chemical findings indicate potential rejuvenation mechanisms, but performance tests ultimately govern evaluation, and long-term durability will require hybrid formulations incorporating stabilizing additives.
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Decoupling Chemical Composition from Viscoelastic Recovery in Rejuvenated Asphalt Binders
(2026-04-01)
Hutabarat, Multazam
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Chamwon, Suwaphit
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Chaturabong, Preeda
This study investigates the decoupling between bulk chemical composition and high-temperature viscoelastic recovery in rejuvenated asphalt binders. A pressurized aging vessel (PAV)-aged binder (AC60/70) was rejuvenated using pyrolytic bio-oils from sugarcane bagasse (SBO) and rice straw (RSO) at 5–20 wt% dosages. SARA fractionation, colloidal instability index (Ic), penetration, and multiple stress creep recovery (MSCR) testing at 0.1 and 3.2 kPa were conducted before and after a rolling thin film oven (RTFO) aging. Both bio-oils restored SARA fractions to nearly identical levels (Ic = 0.541– 0.572), yet penetration diverged substantially (79 vs. 36 dmm at 20% for SBO and RSO, respectively). After RTFO aging, MSCR responses converged across all formulations regardless of pre-aging differences, yielding identical an Equivalent Single Axle Load (ESAL) classification. This convergence is attributed to selective volatilization of low-molecular-weight bio-oil components during thermal conditioning, consistent with findings from a companion rheological–fatigue study. The results reveal a fundamental decoupling: bulk chemical indices, while useful for compositional assessment, do not correspond to stress-dependent viscoelastic recovery mechanisms governing rutting resistance. Performance-based rheological testing is therefore essential for reliable evaluation of rejuvenated binders under field-relevant conditions.

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