Materiales de Construcción

76 (361), January-March 2026, e405

ISSN-L: 0465-2746, eISSN: 1988-3226

https://doi.org/10.3989/mc.2026.407325

ARTICLE

The effect of replacing aggregates with oyster shell powder on the performance of asphalt concrete

Efecto de la sustitución de áridos por polvo de concha de ostra en el rendimiento del hormigón asfáltico

J.R. Chang

Graduate Institute of Architecture and Sustainable Planning, National Ilan University, (Yilan, Taiwan)

Corresponding author: , https://orcid.org/0000-0001-8313-7325

Y.Y. Lo

Graduate Institute of Architecture and Sustainable Planning, National Ilan University, (Yilan, Taiwan)

https://orcid.org/0009-0000-4030-3549

ABSTRACT

In response to the global trend towards achieving net zero emissions, various industries are actively promoting the circular economy. Central to this goal is the strategic utilization of alternative materials to replace virgin materials, thereby reducing carbon emissions during the production and manufacturing processes. This study uses the maximum density line in the FHWA 0.45 power curve to determine the oyster shell powder (OSP) as a substitute for 6% of the fine aggregate and filler in dense-graded asphalt concrete (DGAC). With properties similar to calcium carbonate (CaCO3) and hydrated lime, the inclusion of OSP was expected to enhance the performance of DGAC. For the Experimental Group, 6% of the fine aggregate and filler were replaced with OSP in the DGAC. The control groups used natural aggregate without hydrated lime anti-strip additive (Control Group A) and with hydrated lime anti-strip additive (Control Group B) in the DGAC. The aim was to assess the impact of replacing partial fine aggregate and filler with OSP on the performance of AC. The results indicated that while the Marshall stability, Marshall flow, and indirect tensile strength test values of the Experimental Group were lower than those of Control Group B, they were consistent with the results of Control Group A and complied with AI MS-2 7th. Subsequent evaluations, including the boil test, immersion-compression test, and tensile strength ratio, were conducted to assess moisture damage resistance. This revealed that the Experimental Group and Control Group B exhibited comparable and superior moisture damage resistance compared to Control Group A. Additionally, the Experimental Group outperforms the Control Groups in the Cantabro abrasion test. In summary, the OSP as a substitute for 6% of the fine aggregate and filler enhances the performance of AC, providing effects similar to hydrated lime anti-strip additives and increases moisture damage resistance. This study confirms that using recycled materials such as OSP to replace aggregates in AC, contributing to the goals of energy-saving and carbon reduction in road engineering.

Keywords: Oyster shell powder; Dense-graded asphalt concrete; Fine aggregate; Mineral filler; Moisture damage resistance; Pavements.

RESUMEN

En respuesta a la tendencia global hacia el logro de cero emisiones netas, varias industrias están promoviendo activamente la economía circular. Un elemento central de este objetivo es la utilización estratégica de materiales alternativos para reemplazar materiales naturales, reduciendo así las emisiones de carbono durante los procesos de producción y fabricación. Este estudio utiliza la línea de densidad máxima en la curva de potencia FHWA 0.45 para determinar el polvo de concha de ostra (OSP) como sustituto del 6% del árido fino y el filler en el hormigón asfáltico de granulometría densa (DGAC). Con propiedades similares al carbonato de calcio (CaCO3) y la cal hidratada, se esperaba que la inclusión de OSP mejorara el rendimiento del DGAC. Para el Grupo Experimental, el 6% del árido fino y el filler se reemplazó con OSP en el DGAC. Los grupos de control utilizaron árido natural sin aditivo antidesprendimiento de cal hidratada (Grupo de Control A) y con aditivo antidesprendimiento de cal hidratada (Grupo de Control B) en el DGAC. El objetivo fue evaluar el impacto del reemplazo parcial del árido fino y el filler con OSP en el rendimiento del AC. Los resultados indicaron que, si bien los valores de estabilidad Marshall, flujo Marshall y resistencia a la tracción indirecta del Grupo Experimental fueron inferiores a los del Grupo de Control B, fueron consistentes con los resultados del Grupo de Control A y cumplieron con AI MS-2 7.ª edición. Se realizaron evaluaciones posteriores, incluyendo la prueba de ebullición, la prueba de inmersión-compresión y la relación de resistencia a la tracción, para evaluar la resistencia al daño por humedad. Esto reveló que el Grupo Experimental y el Grupo de Control B exhibieron una resistencia al daño por humedad comparable y superior respecto al Grupo de Control A. Además, el Grupo Experimental supera a los Grupos de Control en la prueba de abrasión de Cantabro. En resumen, el OSP como sustituto del 6% del árido fino y el filler mejora el rendimiento del AC, proporcionando efectos similares a los aditivos antidesprendimiento de cal hidratada y aumentando la resistencia al daño por humedad. Este estudio confirma que el uso de materiales reciclados como el OSP para reemplazar áridos en AC contribuye a los objetivos de ahorro de energía y reducción de carbono en la ingeniería vial.

Palabras clave: Polvo de concha de ostra; Hormigón asfáltico de granulometría densa; Árido fino; Filler mineral; Resistencia a los daños por humedad; Pavimentos.

Received: 20-01-2025 / Accepted: 26-12-2025 / Published: 29-06-2026

Citation: Chang JR, Lo YY. 2026. The effect of replacing aggregates with oyster shell powder on the performance of asphalt concrete. Mater. Construcc. 76(361):e405. https://doi.org/10.3989/mc.2026.407325

Copyright: ©2026 CSIC. This is Diamond Open Access content distributed under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License.

Supplementary information ↓

Content

1. INTRODUCTION

2. LITERATURE REVIEW

2.1. Oyster shell powder (OSP)

2.2. Moisture damage in asphalt concrete pavement

2.3. Mineral filler and anti-strip additive in asphalt concrete

3. EXPERIMENTAL DESIGN

3.1. Materials

3.2. Experimental configuration

3.3. Determining the gradation curve and aggregate blending ratio

3.3.1. OSP replacement ratio

3.3.2. Blended percentages of aggregates for each experimental configuration

3.4. Marshall method of mix design

3.5. Performance testing

4. RESULTS AND ANALYSIS

4.1. Basic properties testing

4.1.1. Sieve analysis

4.1.2. Physical properties

4.1.3. Asphalt binder

4.2. Scanning electron microscope (SEM) and visual observations

4.3. PERFORMANCE TESTING RESULTS

4.3.1. Marshall stability test

4.3.2. Marshall flow test

4.3.3. Immersion–compression test

4.3.4. Indirect tensile strength test

4.3.5. Tensile strength ratio (TSR)

4.3.6. Boil test

4.3.7. Cantabro abrasion test (4545. EN. 2017. EN 12697-17. Bituminous mixtures: test methods. Part 17: particle loss of porous asphalt specimens. https://standards.iteh.ai/catalog/standards/cen/6be521b4-d355-458b-83bb-11c90a00df2e/en-12697-17-2017)

4.3.8. Asphalt content

5. CONCLUSIONS AND FUTURE WORK

REFERENCES

1. INTRODUCTION ↑

With a trend towards achieving net zero carbon emissions and implementation of carbon border adjustment mechanisms (CBAM), there is a concerted effort to reduce reliance on virgin materials in engineering. People are actively utilizing by-products and waste from various industries as alternative materials to decrease the use of virgin materials. Studies that have explored different approaches for adding recycled materials to asphalt concrete have shown the potential in reducing the need for virgin aggregate and have been linked to changes in the aggregate-binder interfacial properties (11. Hoy M, Samrandee V, Samrandee W, Suddeepong A, Phummiphan I, Horpibulsuk S, Buritatum A, Arulrajah A, Yeanyong C. 2023. Evaluation of asphalt pavement maintenance using recycled asphalt pavement with asphalt binders. Constr Build Mater. 406:133425. https://doi.org/10.1016/j.conbuildmat.2023.133425, 22. Hoy M, Suddeepong A, Horpibulsuk S, Akkharawongthattana K, Arulrajah A, Buritatum A, Horpibulsuk J, Rashid ASA. 2023. Improved performance of natural rubber latex–modified asphalt concretes with various types of aggregates. J Mater Civ Eng. 36(1):04023495. https://doi.org/10.1061/JMCEE7.MTENG-16274).

Shell waste, such as oyster shells, mussel shells, and scallop shells, originating from the fishing industry, are abundant in certain regions but are often disposed of or landfilled without being reused. According to the Food and Agriculture Organization of the United Nations (FAO), the annual global oyster production is about 5.5 to 6 million metric tons. Oysters mainly come from Asian countries such as China, Japan, South Korea and Taiwan. These oyster shells are often discarded or buried everywhere, causing environmental problems. Oyster shells are typically hard and corrosion-resistant. Previous studies have confirmed their beneficial effects when incorporated into both cement concrete and asphalt concrete (33. Ruslan HN, Muthusamy K, Mohsin SMS, Jose R, Omar R. 2022. Oyster shell waste as a concrete ingredient: a review. Mater Today Proc. 48(4):713–719. https://doi.org/10.1016/j.matpr.2021.02.208).

The drastic temperature fluctuations from extreme weather conditions, erosion caused by abundant rainfall, and excessive traffic loads contribute to an increased susceptibility of asphalt concrete pavement to damages such as rutting and stripping, consequently reducing service life. Adding anti-strip additives such as hydrated lime and cement to asphalt concrete is a good approach to stop rutting and stripping. This strategy seeks to improve asphalt concrete’s stiffness, ductility at low temperatures, resistance to moisture damage, and aging of the asphalt binder (44. Abuawad IMA, Al-Qadi IL, Trepanier JS. 2015. Mitigation of moisture damage in asphalt concrete: testing techniques and additives/modifiers effectiveness. Constr Build Mater. 84:437–443. https://doi.org/10.1016/j.conbuildmat.2015.03.001). However, the extraction of virgin materials for hydrated lime and cement production contributes to environmental degradation, while the manufacturing process also increases the emission of carbon dioxide and greenhouse gases.

In many countries, oyster shell powder (OSP) is commonly utilized in applications such as animal feed, composting, and seedling cultivation. Taiwan generates over 190,000 metric tons of oyster shells as a waste product annually. In recent years, some companies, such as Taiwan Sugar Corporation in Taiwan (one of the largest enterprises in Taiwan’s agricultural industry), have actively recycled waste oyster shells and reused them in medical, biotechnology, building materials, fertilizer, feed and other fields. However, too many waste oyster shells still pose an environmental burden to Taiwan, which is a small and densely populated country. There is no literature regarding the use of OSP to replace fine aggregates in asphalt concrete. Also, there is no comparison of the performance between asphalt concrete with OSP replacing fine aggregates and asphalt concrete using natural aggregates with added anti-strip additives. This study proposes the utilization of OSP to replace a portion of the fine aggregate in asphalt concrete and to serve as a substitute for hydrated lime or cement typically used as anti-strip additives in asphalt concrete. This approach aims to reduce reliance on river sand and gravel, which are used extensively due to rapid economic development. Additionally, this provides a sustainable outlet for waste oyster shells and enhances moisture damage resistance, thereby improving the quality of asphalt concrete pavement.

2. LITERATURE REVIEW ↑

2.1. Oyster shell powder (OSP) ↑

Due to variations in the marine environments that oysters inhabit, the size and composition of their shells can differ; however, their primary component is calcium carbonate (CaCO₃), typically comprising over 95% of the overall composition, classifying them as a natural calcium-based material (55. Fishery Bulletin. 1962. Chapter II: morphology and structure of shell. Fish Bull. 64:43–44. https://spo.nmfs.noaa.gov/sites/default/files/pdf-content/fish-bull/ch2.pdf). The processing of waste oyster shells can be categorized into calcined and uncalcined forms. After cleaning and coarse crushing, the shells may be subjected to high-temperature calcination, during which the main chemical component transforms into calcium oxide (CaO) (66. Lee CJ. 2005. A study on the application of oyster powder as a cementitious material. Master thesis. National Taiwan Ocean University, Taiwan. https://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/ccd=zcn_Dw/record?r1=2&h1=0, 77. Hsu QW, Chen JT. 2013. Reuse of oyster shells in engineering materials. Fish Ext. 321:6–9. https://www.fa.gov.tw/redirect_file.php?theme=Fisheries_Promotion_Monthly&id=1549), as shown in Table 1. If not calcined, the shells retain their original calcium carbonate (CaCO₃) composition (55. Fishery Bulletin. 1962. Chapter II: morphology and structure of shell. Fish Bull. 64:43–44. https://spo.nmfs.noaa.gov/sites/default/files/pdf-content/fish-bull/ch2.pdf).

Table 1. Chemical composition of OSP.

Chemical composition (%)

Fishery Bulletin (55. Fishery Bulletin. 1962. Chapter II: morphology and structure of shell. Fish Bull. 64:43–44. https://spo.nmfs.noaa.gov/sites/default/files/pdf-content/fish-bull/ch2.pdf)

Lee (66. Lee CJ. 2005. A study on the application of oyster powder as a cementitious material. Master thesis. National Taiwan Ocean University, Taiwan. https://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/ccd=zcn_Dw/record?r1=2&h1=0)

Hsu and Chen (77. Hsu QW, Chen JT. 2013. Reuse of oyster shells in engineering materials. Fish Ext. 321:6–9. https://www.fa.gov.tw/redirect_file.php?theme=Fisheries_Promotion_Monthly&id=1549)

SiO2

0.16

2.17

29.78

Al₂O₃

---

1.10

5.58

Fe₂O₃

---

0.33

1.34

CaO

54.6

54.30

57.87

MgO

0.33

0.75

0.02

SO₃

0.16

0.45

0.05

K₂O

---

---

0.09

CO2

43.5

---

---

Na2O

0.32

---

---

SrO

0.12

---

0.12

H2O

0.58

---

---

Basicity

---

---

2.13

Ignition loss

---

37.62

---

Shu et al. (8)8. Shu X, Huang B, Vukosavljevic D. 2008. Laboratory evaluation of fatigue characteristics of recycled asphalt mixture. Constr Build Mater. 22(7):1323–1330. https://doi.org/10.1016/j.conbuildmat.2007.04.019 stated that seashell powder is thought to enhance the performance of flexible pavement against all types of damage, including the three major distresses of rutting, fatigue cracking, and low-temperature cracking.

According to García et al. (9)9. García I, Heras E, Puertas F, Oteiza I, Martín-Consuegra F, Legarra JJ. 2009. Tests on mortars and concrete made with seashells as aggregate: case study in Mauritania. Proc 11th Int Conf Non-conventional Mater Technol (NOCMAT 2009). Bath (UK). https://www.researchgate.net/publication/282808178_tests_on_mortars_and_concrete_made_with_seashells_as_aggregate_case_study_in_mauritania, seashells are utilized as the aggregate in concrete, but there has been no research yet on their use in hot mix asphalt (HMA). The use of seashells as aggregates in concrete and mortar has been assessed. According to test results, seashell cannot be regarded as aggregate because its qualities do not match those of coarse aggregates. As a result, it was tested as a mortar. However, because the mixture containing the seashells was intended to be utilized as structural concrete, the results were compared with the specifications. In order to ensure that seashells are used properly, the purpose of the study was to discover more about their mechanical, chemical, and physical characteristics.

Seashells of molluscs were used as filler aggregates in an experimental study conducted by Bezerra et al.(10)10. Bezerra UT, Almeida FLP, Silva LB, Barbosa NP, Passos TA, Cavalcante DGL. 2011. Production of filler aggregate from waste of bivalves mollusks shells. J Civ Eng Arch. 5(4):363–367. https://doi.org/10.17265/1934-7359/2011.04.008. Mortar specimens with mass additions of 0%, 5%, 10%, 15%, 20%, and 30% to Portland cement were prepared. After being ground, the seashells passed through the 325-mesh sieve (0.044 mm). X-ray fluorescence and X-ray diffraction (XRD) were used to characterize the material. Seashell powder in two different states were examined: raw and burned. The results confirmed the effect of the filler material, indicating that it might be used as a partial replacement for cement.

Kuo et al. (11)11. Kuo WT, Wang HY, Shu CY, Su DS. 2013. Engineering properties of controlled low-strength materials containing waste oyster shells. Constr Build Mater. 46:128–133. https://doi.org/10.1016/j.conbuildmat.2013.04.020 substituted 5, 10, 15, and 20% waste oyster shells for fine aggregates and 20% fly ash for cement in order to assess the practical usage of waste oyster shells as controlled low-strength materials (CLSM). The findings showed that replacing sand with 20% waste oyster shells did not significantly lower the compressive strength. Waste oyster shells can be a good substitute for sand and a source of pure calcareous materials in CLSM with the proper application.

Arabani et al.(12)12. Arabani M, Babamohammadi S, Azarhoosh AR. 2014. Experimental investigation of seashells used as filler in hot mix asphalt. Int J Pavement Eng. 16(6):502–509. https://doi.org/10.1080/10298436.2014.943132 evaluated the usage of seashell as a replacement of virgin filler in HMA. Indirect tensile fatigue, indirect tensile strength, and permanent deformation tests were used to evaluate the properties of HMA mixtures. The findings showed that the fatigue life and permanent deformation of HMA at various temperatures were improved by the use of seashells as a mineral filler. Additionally, it was shown that the mixtures with seashells showed lower moisture susceptibility than conventional HMA. The study showed that seashell dust might be utilized as a filler material in HMA when available.

Mo et al.(13)13. Mo KH, Alengaram UJ, Jumaat MZ, Lee SC, Goh WI, Yuen CW. 2018. Recycling of seashell waste in concrete: a review. Constr Build Mater. 162:751–764. https://doi.org/10.1016/j.conbuildmat.2017.12.009 examined the properties of different types of seashell waste and how integration affects the both fresh and hardened properties of concrete. Given the significant calcium oxide content, seashell waste may be an inert substance, much like limestone. Seashell waste might still be used as a partial aggregate at a replacement level of up to 20% for concrete used for non-structural purposes.

Nciri et al. (14)14. Nciri N, Shin T, Lee H, Cho N. 2018. Potential of waste oyster shells as a novel biofiller for hot-mix asphalt. Appl Sci. 8(3):415. https://doi.org/10.3390/app8030415 examined the impacts of various OSP fractions (such as 0, 5, 10, and 15 weight percent) on bitumen performance. Fourier transform-infrared spectroscopy, X-ray diffraction, thin layer chromatography–ionization detection, and scanning electron microscopy (SEM) were used to investigate the chemical characteristics of unfilled and OSP-filled asphalts. In comparison to plain asphalt, the results presented that a higher dose of OSP changed the binder’s morphology, while lower and intermediate doses increased thermal stability and improved low-temperature, fatigue, and rutting performance. These findings confirm those of Arabani et al. (12)12. Arabani M, Babamohammadi S, Azarhoosh AR. 2014. Experimental investigation of seashells used as filler in hot mix asphalt. Int J Pavement Eng. 16(6):502–509. https://doi.org/10.1080/10298436.2014.943132.

Ruiz et al.(15)15. Ruiz G, Chávez F, Santamaría S, Araujo W, Timaná J, Schmitt R. 2020. Laboratory evaluation of seashells used as fine aggregate in hot mix asphalt. Int J Pavement Eng. 21(5):620–628. https://doi.org/10.1080/10298436.2018.1502435 performed permanent deformation, indirect tensile strength, and moisture susceptibility tests – all common in Perú – to examine the characteristics of HMA mixtures with seashells. According to the findings, seashells can be added as a fine aggregate to HMA to increase its permanent deformation and indirect tensile strength. When compared to traditional HMA, seashells in decreased moisture susceptibility and raised the tensile strength ratio (TSR) by 22–262%.

In open-graded asphalt mixtures, Alharthai et al. (16)16. Alharthai M, Lu Q, Elnihum A, Elmagarhe A. 2021. Laboratory evaluation of the use of Florida washed shell in open-graded asphalt mixtures. Materials. 14(22):7060. https://doi.org/10.3390/ma14227060 examined the replacement of conventional aggregate with a Florida washed shell and assessed the optimal percentage of substitution in aggregate gradations of different nominal maximum aggregate sizes (NMASs), such as 4.75, 9.5, and 12.5 mm. The Florida washed shell was used in laboratory experiments on specimens at different percentages (0, 15, 30, 45, and 100%) to substitute coarse aggregate with sizes ranging from 2.36 to 12.5 mm. The findings demonstrated that substituting Florida washed shell for the coarse aggregates had no significant effect on the indirect tensile strength and Marshall stability.

Wang et al. (17)17. Wang X, Guo Y, Ji G, Zhang Y, Zhao J, Su H. 2021. Effect of biowaste on the high- and low-temperature rheological properties of asphalt binders. Adv Civ Eng. 2021:1–14. https://doi.org/10.1155/2021/5516546 used a modified asphalt material with waste oyster shells to prepare an asphalt binder of waste OSP. SEM analysis was used to examine the microstructure of OSP. FT-IR spectroscopy was used to determine the asphalt binder’s chemical composition. The findings showed that the waste OSP was a biomass with an irregular, porous petal shape, and when it was mixed with asphalt, no new, distinctive absorption peaks appeared. Additionally, the thermal stability, viscosity, and temperature-sensitive properties of asphalt were enhanced by the addition of waste OSP.

Bamigboye et al. (18)18. Bamigboye GO, Okechukwu UE, Olukanni DO, Bassey DE, Okorie UE, Adebesin J, Jolayemi KJ. 2022. Effective economic combination of waste seashell and river sand as fine aggregate in green concrete. Sustainability. 14(19):12822. https://doi.org/10.3390/su141912822 used a water/cement ratio of 0.5, a concrete mix ratio of 1:2:4, and different proportions of granite 20 mm as coarse aggregates, 4.75 mm river sand as fine aggregates, and 2.5 mm seashells as fine aggregates to assess the eco-friendly concrete. Compressive strength had a substantial correlation with splitting tensile strength and a large negative correlation with seashell percentage, according to correlation and regression analysis.

Utilizing high-speed shear equipment, Fan et al. (19)19. Fan G, Liu H, Liu C, Xue Y, Ju Z, Ding S, Zhang Y, Li Y. 2022. Analysis of the influence of waste seashell as modified materials on asphalt pavement performance. Materials. 15(19):6788. https://doi.org/10.3390/ma15196788 prepared 10, 20, and 30% seashell powder-modified asphalt (SPMA) and stratum corneum-exfoliated seashell powder-modified asphalt (SCESPMA) accordingly utilizing seashell powder and SCESP. The findings demonstrated that the primary component of seashell powder and SCESP, CaCO3, is physically miscible with asphalt and that they are both rough and porous. The complex shear modulus (G*) and phase angle (δ) of SPMA and SCESPMA rise and fall, respectively, when the loading frequency falls between 0.1 and 10 Hz.

Ajah and Mbadike (20)20. Ajah UC, Mbadike EM. 2023. Influence of oyster shell ash filler on the Marshall properties of asphalt concrete. Scholars J Eng Technol. 11(8):163–171. https://saspublishers.com/article/17235 found that adding oyster shell ash improved the asphalt concrete’s flow and stability. While the content of oyster shell ash rose, so did void in mineral aggregate (VMA) and void filled with asphalt (VFA); conversely, while asphalt content rose, void in the mixture decreased and VFA increased. In comparison to the sample without oyster shell ash, the investigation also demonstrated that the asphalt concrete with oyster shell ash-filled increased in stiffness and stability. The results demonstrated the potential of oyster shell ash as an economical and environmentally friendly filler for asphalt concrete.

Hu et al. (21)21. Hu C, Zhong D, Li S. 2023. A study on effect of oyster shell powder on mechanical properties of asphalt and multiple degrees of modification mechanism. Case Stud Constr Mater. 18:e01786. https://doi.org/10.1016/j.cscm.2022.e01786 created OSP modified asphalt by adding 40 mesh OSP to matrix asphalt up to 3, 6, 9, 12, 15, and 18% in order to investigate the impact of OSP on the mechanical properties of asphalt and the mechanism of OSP modification on asphalt. The findings demonstrated that OSP significantly affects asphalt’s mechanical characteristics and that adding OSP improves asphalt’s technical performance. According to the research, an OSP content of 12% had the best modification effect and the most impact on asphalt’s mechanical properties. These findings confirm those of Arabani et al. (12)12. Arabani M, Babamohammadi S, Azarhoosh AR. 2014. Experimental investigation of seashells used as filler in hot mix asphalt. Int J Pavement Eng. 16(6):502–509. https://doi.org/10.1080/10298436.2014.943132.

The additive materials, like High Density Polyethylene (HDPE) waste and oyster shell ash, are able to increase the stability of porous asphalt. The chemical properties of oyster shell ash, which are comparable to those of calcium and silica, increase durability and lock the aggregate and pavement. HDPE is a binder that can enhance the bond between the aggregate and oyster shell ash, reinforcing the porous asphalt mix. Rani et al. (22)22. Rani HA, Syammaun T, Adamy A, Zulaiha Z. 2023. Marshall stability of porous asphalt with oyster shell ash filler substitution and high density polyethylene. Teras J. 13(1):183–192. https://doi.org/10.29103/tj.v13i1.855 analyzed the ideal percentage of oyster shell ash filler and HDPE waste as replacement in asphalt pen 60/70.

2.2. Moisture damage in asphalt concrete pavement ↑

Coarse aggregate, fine aggregate, mineral filler, and asphalt binder are compacted in the proper amounts to create DGAC. Despite its superior waterproofing capabilities and low permeability, repeated traffic loads and exposure to wet, humid weather can weaken the adhesive bond between the aggregate and the asphalt binder film, greatly raising the risk of stripping (2323. Omar HA, Yusoff NIM, Mubaraki M, Ceylan H. 2020. Effects of moisture damage on asphalt mixtures. J Traffic Transp Eng (Engl Ed). 7(5):600–628. https://doi.org/10.1016/j.jtte.2020.07.001, 2424. Gao J, Liu P, Wu Y, Xu Y, Lu H. 2021. Moisture damage of asphalt mixture and its evaluation under the long-term soaked duration. Int J Pavement Res Technol. 14(5):607–614. https://doi.org/10.1007/s42947-020-0176-z). Evaluation of moisture susceptibility in asphalt concrete primarily involves qualitative methods such as the boil test (2525. ASTM. 2005. ASTM D3625. Standard practice for effect of water on bituminous-coated aggregate using boiling water. ASTM Int. https://store.astm.org/d3625-96r05.html) and quantitative methods such as the immersion–compression test. The boil test provides a rapid assessment of the susceptibility of asphalt concrete to stripping when exposed to water but may be influenced by operational factors. The immersion–compression index is the ratio between the Marshall stability values of dry and wet specimens. Xiao et al. (26)26. Xiao R, Polaczyk P, Wang Y, Ma Y, Lu H, Huang B. 2022. Measuring moisture damage of hot-mix asphalt (HMA) by digital imaging-assisted modified boiling test (ASTM D3625). Constr Build Mater. 350:128855. https://doi.org/10.1016/j.conbuildmat.2022.128855 proposed ways to improve the boil test (2525. ASTM. 2005. ASTM D3625. Standard practice for effect of water on bituminous-coated aggregate using boiling water. ASTM Int. https://store.astm.org/d3625-96r05.html) for evaluating water-induced damage to asphalt concrete using digital imagery. In addition to the qualitative and quantitative methods, AI MS-2 7th (2727. Asphalt Institute. 2014. Asphalt mix design methods. Manual Series No. 02 (MS-2). 7th ed. USA. https://my.asphaltinstitute.org/Shop/Product-Catalog/Product-Details?productid=98AFF5B0-351B-E811-80F2-000D3A011CEC) incorporates two evaluation methods: the TSR test (2828. AASHTO. 2014. AASHTO T 283. Standard method of test for resistance of compacted asphalt mixtures to moisture-induced damage. https://standards.globalspec.com/std/13053352/aashto-t-283) and the Hamburg wheel-tracking test (2929. AASHTO. 2019. AASHTO T 324. Standard method of test for Hamburg wheel-track testing of compacted asphalt mixtures. https://standards.globalspec.com/std/13399758/aashto-t-324).

2.3. Mineral filler and anti-strip additive in asphalt concrete ↑

In asphalt concrete, a typical mineral filler completely passes a 1.18 mm (No. 16) sieve, with at least 70% of the particles passing the 0.075 mm (No. 200) sieve (3030. Public Construction Commission. 2019. Construction specifications for public works. Chapter 02741: asphalt concrete general rules. Taiwan. https://pcic.pcc.gov.tw/pwc-web/service/tec0301/, 3131. ASTM. 2019. ASTM D242. Standard specification for mineral filler for asphalt mixtures. ASTM Int. https://store.astm.org/d0242_d0242m-19.html). Air voids within asphalt mixtures are filled with filler. The filler strengthens the stiffness of asphalt mixtures by forming asphalt mastics with enhanced hardness and reduced temperature susceptibility when mixed with asphalt binder (3232. Chen Y, Xu S, Tebaldi G, Romeo E. 2022. Role of mineral filler in asphalt mixture. Road Mater Pavement Des. 23(2):247–286. https://doi.org/10.1080/14680629.2020.1826351). Mineral filler shall consist of finely divided mineral matter such as rock dust, slag dust, hydrated lime, hydraulic cement, fly ash, loess, or other suitable mineral matter (3131. ASTM. 2019. ASTM D242. Standard specification for mineral filler for asphalt mixtures. ASTM Int. https://store.astm.org/d0242_d0242m-19.html). Hydrated lime, which is mostly made of CaO, has potent adsorption properties that make it easier for it to bind with the asphalt binder when it is adhered to aggregate surfaces. As an anti-strip additive, 1% hydrated lime is usually added to asphalt concrete to enhance its stiffness, increase resistance to moisture damage, and improve durability and resistance to rutting (3333. Xing B, Du Y, Fang C, Sun H, Lyu Y, Fan W. 2022. Particle morphology of mineral filler and its effects on the asphalt binder–filler interfacial interaction. Constr Build Mater. 321:126292. https://doi.org/10.1016/j.conbuildmat.2021.126292). Furthermore, recycled fines obtained from dust collection equipment in asphalt plants are most commonly used as filler.

In conclusion, it is evident from the literature that in humid and rainy environments, rainwater is a primary factor causing damage to asphalt concrete pavement. Adding anti-strip additives such as hydrated lime or cement to asphalt concrete can reduce the surface tension between the asphalt binder and the aggregates, allowing the asphalt binder to fully coat the aggregates and enhance the adhesive bond between them. This effectively increases the moisture damage resistance of asphalt mixtures and improves pavement performance. Additionally, the literature suggests that the use of the boil test, immersion–compression test, and TSR test could effectively assess the moisture susceptibility of asphalt concrete.

In Taiwan, the processing of waste oyster shells into OSP is highly developed. OSP is widely used in commercial products such as soil stabilizers and animal feed additives. Relevant literature has explored the use of finely ground OSP as modifiers in asphalt binder by pre-mixing with the asphalt binder to alter the rheological properties, thereby enhancing the performance of asphalt mixtures. Additionally, oyster shells have been used as coarse aggregates in open-graded hot-mix asphalt concrete to improve asphalt concrete strength, moisture damage resistance, cracking resistance, and moisture susceptibility. However, there is no literature regarding the use of OSP to replace fine aggregates in asphalt concrete. Also, there is no comparison of the performance between asphalt concrete with OSP replacing fine aggregates and asphalt concrete using natural aggregates with added anti-strip additives. This study focuses on DGAC and aims to investigate the impact of replacing a portion of the fine aggregate and filler with OSP on the performance of asphalt concrete.

3. EXPERIMENTAL DESIGN ↑

3.1. Materials ↑

This study conducted performance comparisons using DGAC specimens with a 19.0 mm (3/4-inch) NMAS. The materials used are described as follows:

  1. Natural coarse and fine aggregates: Natural river sand and gravel provided by an asphalt plant were used as natural coarse and fine aggregates.
  2. Filler and anti-strip additive in asphalt concrete: The term of “filler” in this study refers to materials passing the 0.075 mm sieve, including both conventional mineral filler such as hydrated lime and recycled fines obtained from dust collection equipment in asphalt plants. Hence, recycled fines from an asphalt plant were used as filler. Additionally, hydrated lime purchased from a building materials supplier was added to the asphalt concrete of the Control Group as an anti-strip additive.
  3. OSP: According to the product information provided by the OSP manufacturer used in this study, the waste oyster shells are collected in a dry state, eliminating the need for wastewater treatment. The collected waste oyster shells undergo coarse crushing and screening, followed by high-temperature calcination in a rotary kiln. The increased surface area resulting from coarse crushing enhances the efficiency of calcination. To reduce energy consumption, the calcination temperature is maintained below 300°C, allowing simultaneous drying and sterilization. The calcined shells are then finely ground, and the particle size of the resulting OSP is controlled through the adjustment of grinder speed and sieve aperture. Further pulverization and sieving are performed based on specific application requirements, yielding approximately 20 kg per bag and resulting in the OSP used in this study. This production process reflects standard industrial practices for OSP manufacturing. In 2024, OSP sells for about USD 0.32~0.47/kg in Taiwan, which is more economical than the price of hydrated lime which is USD 0.63~0.95/kg. It is noted that temperature, dissolved oxygen saturation, suspended matter and other conditions in different sea areas will cause differences in the composition of OSP. The properties of OSP from different sources should be evaluated before the reuse of OSP.

    According to the product information provided by the OSP manufacturer used in this study, its chemical composition is mainly CaCO₃, with small amounts of MgO, SiO₂, and Al₂O₃. This is consistent with the findings reported in the relevant literature (1010. Bezerra UT, Almeida FLP, Silva LB, Barbosa NP, Passos TA, Cavalcante DGL. 2011. Production of filler aggregate from waste of bivalves mollusks shells. J Civ Eng Arch. 5(4):363–367. https://doi.org/10.17265/1934-7359/2011.04.008, 1212. Arabani M, Babamohammadi S, Azarhoosh AR. 2014. Experimental investigation of seashells used as filler in hot mix asphalt. Int J Pavement Eng. 16(6):502–509. https://doi.org/10.1080/10298436.2014.943132).
  4. Asphalt binder: Following the recommendations from the Thickness Design - Asphalt Pavements for Highways and Streets (AI MS-1) (3434. Asphalt Institute. 1999. Thickness design: asphalt pavements for highways and streets. Manual Series No. 01 (MS-1). 9th ed. USA. https://my.asphaltinstitute.org/Shop/Product-Details?productid=F63D527F-351B-E811-80F4-000D3A01109B) and considering Taiwan’s average temperature of approximately 24.3°C in 2023, the asphalt binder grad of AC-20 was used for the experiment.

3.2. Experimental configuration ↑

Recycled fines is commonly mixed in asphalt concrete as filler and to enhance moisture damage resistance. Anti-strip additives such as hydrated lime are often added. The experimental setup is listed in Table 2. The Experimental Group involves replacing a portion of the fine aggregates and the entire mineral filler required in the mix design with OSP. Control Group A consisted of asphalt concrete using natural aggregates without added hydrated lime as an anti-strip additive. Control Group B consisted of asphalt concrete using natural aggregates with added hydrated lime as an anti-strip additive. DGAC specimens were prepared for each group and their performances were evaluated.

Table 2. Experimental configuration.

Group

Detail

Experimental Group

Using OSP to replace 6% of the fine aggregates and the entire filler required in the mix design; recycled fines and hydrated lime are not included.

Control Group A

Natural aggregates without hydrated lime anti-strip additive; 2.8% recycled fines are included as filler.

Control Group B

Natural aggregates with 2.8% of hydrated lime anti-strip additive; recycled fines are not included.

3.3. Determining the gradation curve and aggregate blending ratio ↑

Aggregate gradation is a crucial factor to the performance of asphalt concrete. In the early 1960s, the Bureau of Public Roads (today’s FHWA) introduced a gradation chart which is an especially useful tool in evaluating aggregate gradations. The chart uses a horizontal scale, which represents sieve size openings in inches (millimeters) raised to the 0.45 power, and a vertical scale that represents percent passing. An important feature of the 0.45 power chart is the maximum density line. The maximum density line plots as a straight line from the maximum aggregate size to the origin of the chart. As part of the mix design process, the aggregate gradation can be plotted on the 0.45 power gradation chart. Based on the results of sieve analysis, this study utilized the maximum density line to determine the optimal replacement level of OSP, thereby obtaining the best mixture ratio of OSP to aggregates.

In addition, according to AI MS-2 7th, the gradation and blending operations normally result in an aggregate size distribution based on percentage of mass. Volumetric properties such as air voids and VMA are directly impacted by the amount and size of aggregate particles and the resulting packing characteristics in the final mixture. A gradation can give insight to the final volumetric properties in a particular mixture. However, when the specific gravities of the individual aggregates differ or vary significantly (by 0.20 or more), the blended gradation, based on the mass of the aggregates, may have different volumetric characteristics when compared to an equivalent gradation of materials with similar specific gravities. Therefore, when blending asphalt concrete, if the difference in the specific gravities between different aggregates is equal to or greater than 0.2, it is necessary to adjust the percent passing.

3.3.1. OSP replacement ratio ↑

The study initially attempted a 10% substitution of fine aggregate and entire filler with OSP. However, at this substitution rate, the gradation curve deviated from the maximum density line. Using a trial-and-error method, the substitution rate was gradually reduced by 2% increments down to 6%. The aggregate size distribution curve closely aligns with the maximum density line as shown in Figure 1. Moreover, due to the significant difference in specific gravity between OSP and natural coarse and fine aggregates exceeding 0.2, adjustments were made to the percent passing, as indicated in Table 3. Subsequent research procedures were based on the adjusted percent passing.

Figure 1. The aggregate size distribution curves for different OSP replacement ratios.

Table 3. Adjustment of the percent passing.

Material

Percent passing before adjustment (%)

Specific gravity

Weight (g)

Percent passing after adjustment (%)

3/4”

20

2.618

52.36

20.1

3/8”

26

2.599

67.57

26.0

1/4”

15

2.607

39.11

15.0

Sand

33

2.620

86.46

33.3

OSP

6

2.407

14.44

5.6

Total

100

259.94

100

3.3.2. Blended percentages of aggregates for each experimental configuration ↑

Typically, multiple stockpiles of aggregate are blended to meet the final specified requirements. To avoid the influence of different gradations on the performance of asphalt concrete, the study used the gradation with 6% replacement of OSP to configure the blended percentages of aggregates for the Experimental Group, Control Group A, and Control Group B, as shown in Table 4. It is noted that the 6% of OSP was used to replace the partial fine aggregates and the entire filler required in the mix design. Recycled fines and hydrated lime were not used in the Experimental Group.

Table 4. The blended percentages of aggregates in each experimental configuration.

Material

Group name

3/4”

3/8”

1/4”

Sand

OSP

Recycled fines

Hydrated lime

Experimental Group

20%

26%

15%

33%

6%

-

-

Control Group A

20%

26%

15%

36.2%

-

2.8%

-

Control Group B

20%

26%

15%

36.2%

-

-

2.8%

3.4. Marshall method of mix design ↑

Marshall Method of Mix Design has been developed for many years and is widely used due to its simplicity, low cost, and few instrument requirements. The study employed AC-20 asphalt binder for the Marshall Method of Mix Design conducted on the Experimental Group, Control Group A, and Control Group B to determine the optimum asphalt content. The aggregate gradation and recommended asphalt content for each group were determined as shown in Figure 2. The curve of 6% replacement ratio in Figure 1 is the curve of the Experimental Group in Figure 2. The curves of Control Group A and Control Group B are the same and overlap in Figure 2.

In the equiviscous method, the viscosity of the asphalt binder is determined at two test temperatures, establishing a relationship between temperature and viscosity as the mixing and compaction temperature chart. Compaction temperatures are determined where the viscosity-temperature line crosses the compaction viscosity range of 0.28 ± 0.03 Pa-s. Mixing temperatures are determined where the viscosity-temperature line crosses the mixing viscosity range of 0.17 ± 0.02 Pa-s (2727. Asphalt Institute. 2014. Asphalt mix design methods. Manual Series No. 02 (MS-2). 7th ed. USA. https://my.asphaltinstitute.org/Shop/Product-Catalog/Product-Details?productid=98AFF5B0-351B-E811-80F2-000D3A011CEC). According to AI MS-2 (2727. Asphalt Institute. 2014. Asphalt mix design methods. Manual Series No. 02 (MS-2). 7th ed. USA. https://my.asphaltinstitute.org/Shop/Product-Catalog/Product-Details?productid=98AFF5B0-351B-E811-80F2-000D3A011CEC), the compaction temperature range of 141 to 145°C and the mixing temperature range of 151 to 157°C are determined in this study, as shown in Figure 3.

Figure 2. The aggregate size distribution curve of each experimental configuration.

Figure 3. Mixing and compaction temperature chart.

3.5. Performance testing ↑

To understand the impact of replacing a portion of the fine aggregates and filler in asphalt concrete with OSP, the study followed the Marshall Method of Mix Design to prepare asphalt concrete specimens for the Experimental Group and two Control Groups. The specimens were subjected to Marshall stability, Marshall flow, immersion–compression, indirect tensile strength, TSR, boil, and Cantabro abrasion tests. By comparing the Experimental Group and the two Control Groups, the study aimed to evaluate the effects of adding OSP on the performance of asphalt concrete.

4. RESULTS AND ANALYSIS ↑

4.1. Basic properties testing ↑

4.1.1. Sieve analysis ↑

The aggregates used in this study included 3/4”, 3/8”, 1/4”, sand, and OSP. Sieve analysis tests revealed that 43.2% of the OSP passed the No. 200 (0.075 mm) sieve, with a fineness modulus of 0.73. This indicates that the particle size was sufficiently fine to replace both the fine aggregates and the entire filler in asphalt concrete.

During the treatment process, OSP was crushed and sieved. Sieve analysis conducted in this study confirmed that its particle size meets the requirements for mineral filler in asphalt mixtures (2727. Asphalt Institute. 2014. Asphalt mix design methods. Manual Series No. 02 (MS-2). 7th ed. USA. https://my.asphaltinstitute.org/Shop/Product-Catalog/Product-Details?productid=98AFF5B0-351B-E811-80F2-000D3A011CEC).

4.1.2. Physical properties ↑

The physical properties of the coarse aggregates, fine aggregates, OSP, recycled fines, and hydrated lime (anti-strip additive) used in this study all met the specifications. However, it is important to note that the maximum specific gravity among the aggregates was 2.620 for sand, while the minimum was 2.407 for OSP, resulting in a difference of 0.253, which exceeded the acceptable limit of 0.2. Therefore, adjustments to the percent passing during aggregate blending were necessary. The test results shown in Table 5.

Table 5. Physical properties.

Material

Test item

Aggregates

OSP

Recycled fines

Hydrated lime

3/4”

3/8”

1/4”

Sand

Specific gravity

2.618

2.599

2.607

2.620

2.407

2.492

2.334

Water absorption rate (%)

0.44

0.54

1.04

1.13

---

---

---

4.1.3. Asphalt binder ↑

The basic properties of the AC-20 asphalt binder grade used in this study, as shown in Table 6, all met the requirements for AC-20 in ASTM D3381 (3535. ASTM. 2009. ASTM D3381. Standard specification for viscosity-graded asphalt cement for use in pavement construction. ASTM Int. https://store.astm.org/standards/d3381).

Table 6. Basic properties of AC-20 asphalt binder.

Test

Test value

Requirements for AC-20 (3535. ASTM. 2009. ASTM D3381. Standard specification for viscosity-graded asphalt cement for use in pavement construction. ASTM Int. https://store.astm.org/standards/d3381)

Penetration (25°C), 100 g, 5 s

60

≧ 40

Flash point, Cleveland open cup (ºC)

>230

≧ 232

Viscosity (60ºC, poise)

2250

2000 ± 400

Viscosity (135ºC, poise)

435

≧ 210

Viscosity (60°C, poise) (Tests on residue from thin-film oven test)

3860

≦ 10,000

Ductility (25°C), 5 cm/min, (cm) (Tests on residue from thin-film oven test)

75+

≧20

Specific gravity

1.033

-

4.2. Scanning electron microscope (SEM) and visual observations ↑

To address the differences in particle morphology, this study performed its analysis with SEM imaging and visual observations in Figure 4 and Figure 5, respectively. The results of SEM are as follows:

1. OSP

2. Recycled fines

3. Hydrated lime

Figure 4. SEM: OSP (100x) (left); recycled fines (100x) (middle); hydrated lime (400x) (right).

The results of visual observations are as follows:

1. OSP

2. Recycled fines

3. Hydrated lime

Figure 5. Visual observations (cm): OSP (left); recycled fines (middle); hydrated lime (right).

The OSP particles exhibited rough surfaces and irregular shapes; recycled fines were more uniform and exhibit high fineness, appearing as very fine powder; while hydrated lime particles were even finer and tend to be spherical. These differences in particle morphology affected packing density and the coating behavior of the asphalt binder, which in turn influenced the deformation resistance of the asphalt mixtures (3333. Xing B, Du Y, Fang C, Sun H, Lyu Y, Fan W. 2022. Particle morphology of mineral filler and its effects on the asphalt binder–filler interfacial interaction. Constr Build Mater. 321:126292. https://doi.org/10.1016/j.conbuildmat.2021.126292). Moreover, OSP particles have rough surfaces and relatively high porosity, which facilitate the distribution and coating of asphalt binder and thereby improve the interfacial adhesion of the asphalt mixture (1414. Nciri N, Shin T, Lee H, Cho N. 2018. Potential of waste oyster shells as a novel biofiller for hot-mix asphalt. Appl Sci. 8(3):415. https://doi.org/10.3390/app8030415, 2121. Hu C, Zhong D, Li S. 2023. A study on effect of oyster shell powder on mechanical properties of asphalt and multiple degrees of modification mechanism. Case Stud Constr Mater. 18:e01786. https://doi.org/10.1016/j.cscm.2022.e01786).

4.3. PERFORMANCE TESTING RESULTS ↑

In order to minimize possible experimental errors, for each performance test, the study produces three specimens for the Experimental Group, Control Group A and Control Group B respectively, and calculates the average of the three specimens as the results of each group for comparison.

4.3.1. Marshall stability test ↑

Marshall stability is the peak resistance load obtained during a constant rate of deformation. Marshall stability represents the asphalt concrete’s resistance to failure, and the test results are shown in Figure 6(a). The reference value of Marshall stability is ≥ 8006 N (816 kgf) (2727. Asphalt Institute. 2014. Asphalt mix design methods. Manual Series No. 02 (MS-2). 7th ed. USA. https://my.asphaltinstitute.org/Shop/Product-Catalog/Product-Details?productid=98AFF5B0-351B-E811-80F2-000D3A011CEC). The results indicate that the asphalt concrete of Control Group B exhibited the highest stability, while the Experimental Group and Control Group A showed similar stability values. The stability values for all groups met the requirements of AI MS-2 7th.

The similarity in Marshall stability among the three groups can be attributed to the control of gradation using the maximum density line, ensuring sufficient compaction of the aggregates and promoting interlocking effects between them. However, OSP likely has a lower crushing strength than natural aggregate, which reduces the asphalt mixture’s resistance to load (1414. Nciri N, Shin T, Lee H, Cho N. 2018. Potential of waste oyster shells as a novel biofiller for hot-mix asphalt. Appl Sci. 8(3):415. https://doi.org/10.3390/app8030415, 2020. Ajah UC, Mbadike EM. 2023. Influence of oyster shell ash filler on the Marshall properties of asphalt concrete. Scholars J Eng Technol. 11(8):163–171. https://saspublishers.com/article/17235). This may explain the slightly lower stability of the Experimental Group compared to Control Group A and Control Group B. Nevertheless, the reduction in Marshall stability remains within the limits specified by the standards, indicating that OSP as a substitute has only a limited impact on the overall structural strength of the pavement. Additionally, the addition of hydrated lime to asphalt binder contributes to stiffening, resulting in the superior performance of Control Group B in terms of stability.

4.3.2. Marshall flow test ↑

Marshall flow is a measure of the deformation (elastic plus plastic) of the asphalt concrete specimen determined during the stability test. A high flow value indicates that the asphalt concrete is susceptible to permanent deformation under traffic loads, while a low value suggests a propensity for cracking. The reference value of Marshall flow is 8–14 (0.25 mm) (2727. Asphalt Institute. 2014. Asphalt mix design methods. Manual Series No. 02 (MS-2). 7th ed. USA. https://my.asphaltinstitute.org/Shop/Product-Catalog/Product-Details?productid=98AFF5B0-351B-E811-80F2-000D3A011CEC). The test results, as depicted in Figure 6(b), indicate that the Experimental Group and Control Group A had higher flow values compared to Control Group B. This may be because OSP likely has a lower crushing strength than natural aggregate in Experimental Group. Control group B has the lowest flow value due to the stiffening when adding hydrated lime to the asphalt binder. This implies that when using OSP as a substitute for aggregates, caution should be exercised to avoid excessive traffic loads. However, the average flow values of all three groups met specifications.

Previous literature has indicated that OSP possesses a lower crushing strength than natural aggregates, primarily due to its porous structure (1414. Nciri N, Shin T, Lee H, Cho N. 2018. Potential of waste oyster shells as a novel biofiller for hot-mix asphalt. Appl Sci. 8(3):415. https://doi.org/10.3390/app8030415, 2020. Ajah UC, Mbadike EM. 2023. Influence of oyster shell ash filler on the Marshall properties of asphalt concrete. Scholars J Eng Technol. 11(8):163–171. https://saspublishers.com/article/17235). This characteristic reasonably explains why the Experimental Group exhibited lower Marshall stability (Figure 6(a)) and higher Marshall flow (Figure 6(b)) than Control Groups A and B. Additionally, the replacement levels of OSP and filler (Table 4), as determined by the maximum density line, may also influence the results of Marshall stability and Marshall flow.

4.3.3. Immersion–compression test ↑

The ratio between the stability of the conditioned subset of specimens and the unconditioned subset of specimens is the index of retained stability. The retained stability index is used to assess the moisture damage resistance between asphalt binder and aggregates. The reference value of immersion–compression test is ≥ 75% (3636. AASHTO. 2002. AASHTO T 165. Standard method of test for effect of water on compressive strength of compacted bituminous mixtures. https://standards.globalspec.com/std/1020795/aashto-t-165). The test results, depicted in Figure 6(c), indicate that the Experimental Group and Control Group B demonstrated comparable and superior moisture damage resistance, respectively, compared to Control Group A. This suggests that OSP enhances the bonding between asphalt binder and aggregates, thereby improving the moisture damage resistance of the asphalt concrete.

4.3.4. Indirect tensile strength test ↑

Indirect tensile strength test is used to analyze mixtures to assess their low temperature cracking performance. The indirect tensile strength test is also utilized to assess the bonding condition and tensile resistance under moisture damage. Mixture with indirect tensile strength less than 200 kPa was defined to have poor rut resistance, while with indirect tensile strength greater than 320 kPa was defined to have good rut resistance properties (3737. Christensen DW, Bonaquist R, Jack DP. 2000. Evaluation of triaxial strength as a simple test for asphalt concrete rut resistance. Pennsylvania Transportation Institute.-3939. ASTM. 2025. ASTM D6931. Standard test method for indirect tensile (IDT) strength of asphalt mixtures. ASTM Int. https://store.astm.org/d6931-17.html).

The test results, illustrated in Figure 6(d), indicate that Control Group B exhibited the highest indirect tensile strength, followed by the Experimental Group. This suggests that adding hydrated lime anti-strip additive to asphalt concrete or using OSP to replace a portion of the fine aggregate and entire filler can effectively enhance the material’s resistance to tensile failure. Conversely, Control Group A showed the lowest indirect tensile strength.

4.3.5. Tensile strength ratio (TSR) ↑

TSR compares the average indirect tensile strength of wet specimens to that of dry specimens. It assesses the degree of stripping between asphalt binder and aggregates caused by pore water pressure. TSR is calculated by dividing the average indirect tensile strength of the three conditioned (wet) specimens by the average indirect tensile strength of the three unconditioned (dry) specimens. According to AASHTO T 283 test (2828. AASHTO. 2014. AASHTO T 283. Standard method of test for resistance of compacted asphalt mixtures to moisture-induced damage. https://standards.globalspec.com/std/13053352/aashto-t-283, 4040. Iowa Department of Transportation. 2008. Section 2303: hot mix asphalt mixtures.), the moisture sensitivity evaluation on mixtures without anit-strip agent indicates the minimum requirements for moisture sensitivity of 80% TSR with visual confirmation. Furthermore, the contractor’s TSR result is verified if the TSR result is above 0.80 (4141. Federal Highway Administration. 2025. Section 402: asphalt concrete pavement by Hveem or Marshall mix design method. FP-24 CFL library of supplemental specifications. https://highways.dot.gov/federal-lands/specs/cfl-los/fp-24-library/402-fp24.docx). Most agencies use a minimum value of TSR = 80% in the moisture sensitivity test (4242. Tayebali AA, Guddati M, Yadav S, LaCroix A. 2019. Use of moisture induced stress tester (M.i.S.T) to determine moisture sensitivity of asphalt mixtures. NCDOT Project 2017-01. https://connect.ncdot.gov/projects/research/RNAProjDocs/2017-01Final%20Report.pdf). In addition, the target minimum value for TSR is 75%. Mixes with a TSR value meeting the target minimum are considered suitable for mix production and will not require the use of a liquid anti-strip additive (4343. Ministry of Transportation and Economic Corridors. 2025. Subsection 3.50.3.2: requirements for mix design. Specification AMC_S262. Alberta, Canada. http://www.transportation.alberta.ca/Content/docType29/production/AMC_S262(Sec_3-50).pdf).

In this study, three specimens were prepared for the Experimental Group and two control groups to determine the average TSR values. As depicted in Figure 6(e), the TSR values for the Experimental Group and Control Group B were both above 80%, indicating that both OSP and hydrated lime anti-strip additive could reduce the stripping effects of pore water pressure. OSP effectively improves the adhesion between aggregates and asphalt binder. This is attributed to its rough surface texture and the main component of OSP after calcination, CaO, with strong adsorption properties, which enhances adhesion. When CaO adheres to aggregates, it can reduce the surface tensile strength between asphalt binder and aggregates, allowing the asphalt binder to fully wrap aggregates. However, the TSR value for Control Group A was above 80%, at about 80.7%. This suggests that asphalt concrete using natural aggregates without hydrated lime anti-strip additive has a relatively lower indirect tensile strength under moisture exposure.

Existing literature has demonstrated that fillers rich in CaO exhibit stronger adsorption capabilities. This enhances the adhesion between aggregates and asphalt binder and reduces moisture susceptibility. Abuawad et al. (4)4. Abuawad IMA, Al-Qadi IL, Trepanier JS. 2015. Mitigation of moisture damage in asphalt concrete: testing techniques and additives/modifiers effectiveness. Constr Build Mater. 84:437–443. https://doi.org/10.1016/j.conbuildmat.2015.03.001 and Arabani et al.(12)12. Arabani M, Babamohammadi S, Azarhoosh AR. 2014. Experimental investigation of seashells used as filler in hot mix asphalt. Int J Pavement Eng. 16(6):502–509. https://doi.org/10.1080/10298436.2014.943132 suggested that the addition of OSP can increase the asphalt mixture’s resistance to moisture damage, improve interfacial bonding characteristics, and thereby enhance durability, which explains the superior moisture damage resistance observed in the Experimental Group (Figure 6 (c) and Figure 6 (e)).

4.3.6. Boil test ↑

The boil test is a quick and easy visual indication of chemical incompatibility between the asphalt binder and aggregate. The specimens are produced manually using mixing facility in the laboratory to prepare each group of 2,000 g loose asphalt mixture. A specimen of loose asphalt mixture is placed in boiling water for 10 minutes and then removed. The extent of retained asphalt coating on the aggregate is then evaluated relative to a nonconditioned specimen. The boil test is an example of a loose mix test that is used to characterize the bonding between the asphalt and aggregate (adhesion). When the aggregates are mixed in the laboratory with the designated grade of asphalt, the coating area shall be greater than 95% (4444. Washington State Department of Transportation. 2023. General special provisions 4-05: permeable asphalt treated base. https://wsdot.wa.gov/publications/fulltext/localprograms/APWA-GSPs/4-SA2.rtf). The test results depicted in Figure 6 (f) indicate that the Experimental Group and Control Group B exhibited minimal stripping after boiling, with the asphalt mixture retaining its glossy appearance. This demonstrates that OSP could enhance the moisture damage resistance of asphalt concrete. In contrast, Control Group A showed more stripping, particularly at the location marked by a red circle in Figure 6 (g).

Figure 6. Performance testing.

4.3.7. Cantabro abrasion test (4545. EN. 2017. EN 12697-17. Bituminous mixtures: test methods. Part 17: particle loss of porous asphalt specimens. https://standards.iteh.ai/catalog/standards/cen/6be521b4-d355-458b-83bb-11c90a00df2e/en-12697-17-2017) ↑

The Cantabro abrasion test determines the particle loss of the laboratory-compacted cylindrical specimens of asphalt mixtures after completion of a specified number of revolutions. The particle loss is assessed by the loss of mass of asphalt samples after turns in the Los Angeles machine. The results are expressed as retained mass (%). According to EN 12697-17 (4545. EN. 2017. EN 12697-17. Bituminous mixtures: test methods. Part 17: particle loss of porous asphalt specimens. https://standards.iteh.ai/catalog/standards/cen/6be521b4-d355-458b-83bb-11c90a00df2e/en-12697-17-2017), the recommended maximum mass loss is 20%, which corresponds to a retained mass of at least 80%. Therefore, the acceptance threshold is indicated at 80%. This test enables the estimation of the abrasion resistance of asphalt mixtures under traffic loads and friction.

The percent of weight loss is said to be an indication of durability and is related to the quantity and quality of binder utilized. The results, as shown in Figure 6 (h), indicate that the Experimental Group exhibited the best performance in resisting aggregate abrasion. This is likely attributed to the addition of OSP. In order to meet mix design requirements, a slightly higher asphalt content was used, which provided more asphalt binder to coat the aggregate. Moreover, the rougher surface and greater porosity of OSP particles facilitated the distribution and coating of asphalt binder (2121. Hu C, Zhong D, Li S. 2023. A study on effect of oyster shell powder on mechanical properties of asphalt and multiple degrees of modification mechanism. Case Stud Constr Mater. 18:e01786. https://doi.org/10.1016/j.cscm.2022.e01786), which enhances the bonding between asphalt binder and aggregates, thereby improving the bonding between aggregates and enhancing their resistance to abrasion. This not only reduced the abrasion of the asphalt mixture but also confirmed the capacity of OSP to improve the distribution and coating of asphalt binder.

4.3.8. Asphalt content ↑

Due to the rough and highly absorptive surface of OSP particles, a higher asphalt content is required (1212. Arabani M, Babamohammadi S, Azarhoosh AR. 2014. Experimental investigation of seashells used as filler in hot mix asphalt. Int J Pavement Eng. 16(6):502–509. https://doi.org/10.1080/10298436.2014.943132). Therefore, to meet the requirements for mix design, the Experimental Group was formulated with a slightly higher asphalt content. The increased asphalt content not only improved the coating and adhesion between aggregates and asphalt binder but also enhanced the abrasion resistance in the Cantabro abrasion test (Figure 6 (h)). These findings are consistent with the results of Hu et al. (21)21. Hu C, Zhong D, Li S. 2023. A study on effect of oyster shell powder on mechanical properties of asphalt and multiple degrees of modification mechanism. Case Stud Constr Mater. 18:e01786. https://doi.org/10.1016/j.cscm.2022.e01786, who reported that increasing asphalt content improved the durability of OSP-modified asphalt mixtures.

5. CONCLUSIONS AND FUTURE WORK ↑

To understand the effect of the addition of OSP on asphalt concrete performance, this study replaced 6% of the fine aggregate and entire mineral filler required in the mix design with OSP in the Experimental Group. Control Group A consisted of asphalt concrete with natural aggregates without hydrated lime anti-strip additive, while Control Group B included asphalt concrete with natural aggregates and hydrated lime anti-strip additive. Various performance tests were conducted on specimens from each group, yielding the following findings:

Supplementary information ↑

Funding sources

This research was completed with no funding supports.

Supplementary material

Not applicable.

Data availability

Not applicable.

Acknowledgements

Not applicable.

Authorship contribution statement

FJia-Ruey Chang: Conceptualization, Data curation, Formal analysis, Funding acquisition, Methodology, Project administration, Resources, Supervision, Validation, Writing - review & editing.

Yi-Yu Lo: Conceptualization, Formal analysis, Investigation, Methodology, Visualization, Writing - original draft.

Competing interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper

Statement on the use of Artificial Intelligence

Not applicable.

REFERENCES ↑

1. Hoy M, Samrandee V, Samrandee W, Suddeepong A, Phummiphan I, Horpibulsuk S, Buritatum A, Arulrajah A, Yeanyong C. 2023. Evaluation of asphalt pavement maintenance using recycled asphalt pavement with asphalt binders. Constr Build Mater. 406:133425. https://doi.org/10.1016/j.conbuildmat.2023.133425

2. Hoy M, Suddeepong A, Horpibulsuk S, Akkharawongthattana K, Arulrajah A, Buritatum A, Horpibulsuk J, Rashid ASA. 2023. Improved performance of natural rubber latex–modified asphalt concretes with various types of aggregates. J Mater Civ Eng. 36(1):04023495. https://doi.org/10.1061/JMCEE7.MTENG-16274

3. Ruslan HN, Muthusamy K, Mohsin SMS, Jose R, Omar R. 2022. Oyster shell waste as a concrete ingredient: a review. Mater Today Proc. 48(4):713–719. https://doi.org/10.1016/j.matpr.2021.02.208

4. Abuawad IMA, Al-Qadi IL, Trepanier JS. 2015. Mitigation of moisture damage in asphalt concrete: testing techniques and additives/modifiers effectiveness. Constr Build Mater. 84:437–443. https://doi.org/10.1016/j.conbuildmat.2015.03.001

5. Fishery Bulletin. 1962. Chapter II: morphology and structure of shell. Fish Bull. 64:43–44. https://spo.nmfs.noaa.gov/sites/default/files/pdf-content/fish-bull/ch2.pdf

6. Lee CJ. 2005. A study on the application of oyster powder as a cementitious material. Master thesis. National Taiwan Ocean University, Taiwan. https://ndltd.ncl.edu.tw/cgi-bin/gs32/gsweb.cgi/ccd=zcn_Dw/record?r1=2&h1=0

7. Hsu QW, Chen JT. 2013. Reuse of oyster shells in engineering materials. Fish Ext. 321:6–9. https://www.fa.gov.tw/redirect_file.php?theme=Fisheries_Promotion_Monthly&id=1549

8. Shu X, Huang B, Vukosavljevic D. 2008. Laboratory evaluation of fatigue characteristics of recycled asphalt mixture. Constr Build Mater. 22(7):1323–1330. https://doi.org/10.1016/j.conbuildmat.2007.04.019

9. García I, Heras E, Puertas F, Oteiza I, Martín-Consuegra F, Legarra JJ. 2009. Tests on mortars and concrete made with seashells as aggregate: case study in Mauritania. Proc 11th Int Conf Non-conventional Mater Technol (NOCMAT 2009). Bath (UK). https://www.researchgate.net/publication/282808178_tests_on_mortars_and_concrete_made_with_seashells_as_aggregate_case_study_in_mauritania

10. Bezerra UT, Almeida FLP, Silva LB, Barbosa NP, Passos TA, Cavalcante DGL. 2011. Production of filler aggregate from waste of bivalves mollusks shells. J Civ Eng Arch. 5(4):363–367. https://doi.org/10.17265/1934-7359/2011.04.008

11. Kuo WT, Wang HY, Shu CY, Su DS. 2013. Engineering properties of controlled low-strength materials containing waste oyster shells. Constr Build Mater. 46:128–133. https://doi.org/10.1016/j.conbuildmat.2013.04.020

12. Arabani M, Babamohammadi S, Azarhoosh AR. 2014. Experimental investigation of seashells used as filler in hot mix asphalt. Int J Pavement Eng. 16(6):502–509. https://doi.org/10.1080/10298436.2014.943132

13. Mo KH, Alengaram UJ, Jumaat MZ, Lee SC, Goh WI, Yuen CW. 2018. Recycling of seashell waste in concrete: a review. Constr Build Mater. 162:751–764. https://doi.org/10.1016/j.conbuildmat.2017.12.009

14. Nciri N, Shin T, Lee H, Cho N. 2018. Potential of waste oyster shells as a novel biofiller for hot-mix asphalt. Appl Sci. 8(3):415. https://doi.org/10.3390/app8030415

15. Ruiz G, Chávez F, Santamaría S, Araujo W, Timaná J, Schmitt R. 2020. Laboratory evaluation of seashells used as fine aggregate in hot mix asphalt. Int J Pavement Eng. 21(5):620–628. https://doi.org/10.1080/10298436.2018.1502435

16. Alharthai M, Lu Q, Elnihum A, Elmagarhe A. 2021. Laboratory evaluation of the use of Florida washed shell in open-graded asphalt mixtures. Materials. 14(22):7060. https://doi.org/10.3390/ma14227060

17. Wang X, Guo Y, Ji G, Zhang Y, Zhao J, Su H. 2021. Effect of biowaste on the high- and low-temperature rheological properties of asphalt binders. Adv Civ Eng. 2021:1–14. https://doi.org/10.1155/2021/5516546

18. Bamigboye GO, Okechukwu UE, Olukanni DO, Bassey DE, Okorie UE, Adebesin J, Jolayemi KJ. 2022. Effective economic combination of waste seashell and river sand as fine aggregate in green concrete. Sustainability. 14(19):12822. https://doi.org/10.3390/su141912822

19. Fan G, Liu H, Liu C, Xue Y, Ju Z, Ding S, Zhang Y, Li Y. 2022. Analysis of the influence of waste seashell as modified materials on asphalt pavement performance. Materials. 15(19):6788. https://doi.org/10.3390/ma15196788

20. Ajah UC, Mbadike EM. 2023. Influence of oyster shell ash filler on the Marshall properties of asphalt concrete. Scholars J Eng Technol. 11(8):163–171. https://saspublishers.com/article/17235

21. Hu C, Zhong D, Li S. 2023. A study on effect of oyster shell powder on mechanical properties of asphalt and multiple degrees of modification mechanism. Case Stud Constr Mater. 18:e01786. https://doi.org/10.1016/j.cscm.2022.e01786

22. Rani HA, Syammaun T, Adamy A, Zulaiha Z. 2023. Marshall stability of porous asphalt with oyster shell ash filler substitution and high density polyethylene. Teras J. 13(1):183–192. https://doi.org/10.29103/tj.v13i1.855

23. Omar HA, Yusoff NIM, Mubaraki M, Ceylan H. 2020. Effects of moisture damage on asphalt mixtures. J Traffic Transp Eng (Engl Ed). 7(5):600–628. https://doi.org/10.1016/j.jtte.2020.07.001

24. Gao J, Liu P, Wu Y, Xu Y, Lu H. 2021. Moisture damage of asphalt mixture and its evaluation under the long-term soaked duration. Int J Pavement Res Technol. 14(5):607–614. https://doi.org/10.1007/s42947-020-0176-z

25. ASTM. 2005. ASTM D3625. Standard practice for effect of water on bituminous-coated aggregate using boiling water. ASTM Int. https://store.astm.org/d3625-96r05.html

26. Xiao R, Polaczyk P, Wang Y, Ma Y, Lu H, Huang B. 2022. Measuring moisture damage of hot-mix asphalt (HMA) by digital imaging-assisted modified boiling test (ASTM D3625). Constr Build Mater. 350:128855. https://doi.org/10.1016/j.conbuildmat.2022.128855

27. Asphalt Institute. 2014. Asphalt mix design methods. Manual Series No. 02 (MS-2). 7th ed. USA. https://my.asphaltinstitute.org/Shop/Product-Catalog/Product-Details?productid=98AFF5B0-351B-E811-80F2-000D3A011CEC

28. AASHTO. 2014. AASHTO T 283. Standard method of test for resistance of compacted asphalt mixtures to moisture-induced damage. https://standards.globalspec.com/std/13053352/aashto-t-283

29. AASHTO. 2019. AASHTO T 324. Standard method of test for Hamburg wheel-track testing of compacted asphalt mixtures. https://standards.globalspec.com/std/13399758/aashto-t-324

30. Public Construction Commission. 2019. Construction specifications for public works. Chapter 02741: asphalt concrete general rules. Taiwan. https://pcic.pcc.gov.tw/pwc-web/service/tec0301/

31. ASTM. 2019. ASTM D242. Standard specification for mineral filler for asphalt mixtures. ASTM Int. https://store.astm.org/d0242_d0242m-19.html

32. Chen Y, Xu S, Tebaldi G, Romeo E. 2022. Role of mineral filler in asphalt mixture. Road Mater Pavement Des. 23(2):247–286. https://doi.org/10.1080/14680629.2020.1826351

33. Xing B, Du Y, Fang C, Sun H, Lyu Y, Fan W. 2022. Particle morphology of mineral filler and its effects on the asphalt binder–filler interfacial interaction. Constr Build Mater. 321:126292. https://doi.org/10.1016/j.conbuildmat.2021.126292

34. Asphalt Institute. 1999. Thickness design: asphalt pavements for highways and streets. Manual Series No. 01 (MS-1). 9th ed. USA. https://my.asphaltinstitute.org/Shop/Product-Details?productid=F63D527F-351B-E811-80F4-000D3A01109B

35. ASTM. 2009. ASTM D3381. Standard specification for viscosity-graded asphalt cement for use in pavement construction. ASTM Int. https://store.astm.org/standards/d3381

36. AASHTO. 2002. AASHTO T 165. Standard method of test for effect of water on compressive strength of compacted bituminous mixtures. https://standards.globalspec.com/std/1020795/aashto-t-165

37. Christensen DW, Bonaquist R, Jack DP. 2000. Evaluation of triaxial strength as a simple test for asphalt concrete rut resistance. Pennsylvania Transportation Institute.

38. Brown ER, Kandhal PS, Zhang J. 2001. Performance testing for hot mix asphalt. NCAT Rep 01-05. National Center for Asphalt Technology, Auburn (USA). https://eng.auburn.edu/research/centers/ncat/files/technical-reports/rep01-05.pdf

39. ASTM. 2025. ASTM D6931. Standard test method for indirect tensile (IDT) strength of asphalt mixtures. ASTM Int. https://store.astm.org/d6931-17.html

40. Iowa Department of Transportation. 2008. Section 2303: hot mix asphalt mixtures.

41. Federal Highway Administration. 2025. Section 402: asphalt concrete pavement by Hveem or Marshall mix design method. FP-24 CFL library of supplemental specifications. https://highways.dot.gov/federal-lands/specs/cfl-los/fp-24-library/402-fp24.docx

42. Tayebali AA, Guddati M, Yadav S, LaCroix A. 2019. Use of moisture induced stress tester (M.i.S.T) to determine moisture sensitivity of asphalt mixtures. NCDOT Project 2017-01. https://connect.ncdot.gov/projects/research/RNAProjDocs/2017-01Final%20Report.pdf

43. Ministry of Transportation and Economic Corridors. 2025. Subsection 3.50.3.2: requirements for mix design. Specification AMC_S262. Alberta, Canada. http://www.transportation.alberta.ca/Content/docType29/production/AMC_S262(Sec_3-50).pdf

44. Washington State Department of Transportation. 2023. General special provisions 4-05: permeable asphalt treated base. https://wsdot.wa.gov/publications/fulltext/localprograms/APWA-GSPs/4-SA2.rtf

45. EN. 2017. EN 12697-17. Bituminous mixtures: test methods. Part 17: particle loss of porous asphalt specimens. https://standards.iteh.ai/catalog/standards/cen/6be521b4-d355-458b-83bb-11c90a00df2e/en-12697-17-2017