Effects of RHA, BA and PSA on void characteristics_
| Filler type | Effect on VIM | Effect on VMA | Effect on VFB | Key considerations | Reference |
|---|---|---|---|---|---|
| Rice Husk Ash | Reduces (optimal) | Reduces (optimal) | Increases | Risk of over-compaction at high content | (Mohajerani et al., 2017), (Shafabakhsh et al., 2018), (Raj et al., 2023), (Mistry & Kumar Roy, 2021) |
| Bagasse Ash | Reduces (if fine) | Reduces (if fine) | Increases | Effectiveness depends on fineness and carbon content | (Yoo et al., 2016),(Kim et al., 2024), (Buritatum et al., 2022) |
| Palm Shell Ash | Most reduction | Most reduction | Most increase | Superior densification; risk of bleeding if excessive | (Ramdhani et al., 2025), (Oktavia et al., 2022), (Doğruyol & Durmaz, 2025) |
Effects of RHA, BA and PSA on stability and flow characteristics_
| Filler type | Effect on Marshall stability | Effect on flow | Key technical notes | Reference |
|---|---|---|---|---|
| Rice Husk Ash (RHA) | Increases stability at optimal content (6–8% by weight); excessive use may induce brittleness and reduce ductility. | Generally, it maintains acceptable flow; excessive content may decrease ductility. | High silica content and angular morphology improve binder-filler interaction; dosage optimization is crucial. | (Arabani & Tahami, 2017b), (Ragab & Abo El-Naga, 2022), (M. N. N. Khan et al., 2015), (Lu et al., 2020), (Fareed et al., 2020), (Rahmouni et al., 2019), (Nava Bravo et al., 2019) |
| Bagasse Ash (BA) | Increases stability via angular particles; varies with fineness and carbon content. | Maintains or slightly improves flow; excessive carbon or coarse particles may reduce homogeneity. | Fineness and residual carbon content are critical for performance; proper processing is needed. | (Zainudin et al., 2016), (Sarir et al., 2025), (Jwaida et al., 2024), (F. de A. Silva et al., 2011), (Liu et al., 2020), (Rahmouni et al., 2019), (Nava Bravo et al., 2019), (Zhang et al., 2020) |
| Palm Shell Ash (PSA) | Yields moderate stability compared to RHA and BA. | Greatly improves flow, enhancing workability and deformation tolerance. | Fine particle size and mineral composition enhance flexibility; suitable for dynamic loading conditions. | (Pelisser et al., 2010), (T.-A. De Silva & Forbes, 2016), (Shi & Reitz, 2010), (Chaudhuri et al., 2018), (Amanda et al., 2025) [23],[24],[25], (Chan et al., 2019), (Patel et al., 2017), (Naqvi et al., 2019) |
Effects of RHA, BA and PSA on Marshall quotient_
| Filler type | Typical optimal content (% by weight of filler) | Effect on Marshall quotient (MQ) | Technical explanation / Key findings | Practical implications | Reference |
|---|---|---|---|---|---|
| Rice Husk Ash (RHA) | 6–8% | Increases MQ up to optimal content; excessive use may reduce flexibility | High silica and angular, porous particles enhance interlocking and stiffness; excessive RHA can cause brittleness and cracking. | Good for rutting resistance; needs dosage optimization | (Damanhuri et al., 2020), (Du et al., 2018), (Guo et al., 2025) |
| Bagasse Ash (BA) | 5–10% | Moderate increase in MQ at optimal dosage | Angularity and rough surface improve binder adhesion and stability; unprocessed BA (with residual carbon) may lower MQ. | Enhances deformation resistance; quality control needed | (Sarir et al., 2022), (Zia & Khan, 2021), (Nava Bravo et al., 2019) |
| Palm Shell Ash (PSA) | 5–10% | Highest MQ among the three fillers | Fine particle size and mineral composition improve particle packing, stability, and stiffness; maintains good workability. | Best for high stiffness and rutting resistance | (Omoremiju et al., 2024) |
Environmental and practical implications of RHA, BA and PSA as asphalt fillers_
| Filler type | Environmental benefits | Practical implications | Key challenges & considerations | Reference |
|---|---|---|---|---|
| Rice Husk Ash (RHA) |
|
|
| (Pachchigar et al., 2024), (Kartini et al., 2012), (Raj et al., 2023) |
| Bagasse Ash (BA) |
|
|
| (Raza et al., 2021), (Adeoti et al., 2025), (Bayapureddy et al., 2024), (Aprianti et al., 2015), (Jain et al., 2024) |
| Palm Shell Ash (PSA) |
|
|
| (Ikumapayi & Akinlabi, 2018), (Inyang et al., 2024), (Torres-Ortega et al., 2024) |
Summary review of RHA, BA and PSA as asphalt fillers_
| Filler type | Optimal content (%) | Effect on stability | Flow | MQ | Notes |
|---|---|---|---|---|---|
| RHA | 6–8 | ↑↑ | ↔ | ↑↑ | High SiO2, best stiffness gain |
| BA | 4–6 | ↑ | ↔ | ↑ | Sensitive to carbon content |
| PSA | 5–7 | ↑ | ↑↑ | ↔ | Enhances flexibility |
Systematic review methodology stages_
| Methodological stage | Activity description | Main output/Result | Reference |
|---|---|---|---|
| Literature identification | Article searches were conducted in Scopus, ScienceDirect, Google Scholar, and Garuda using keywords related to ash-based fillers and asphalt (2010–2024). | Initial collection of relevant studies. | (Putri et al., 2022) |
| Initial screening | Selection based on title and abstract to eliminate irrelevant studies. | List of potentially relevant studies for further review. | (Arabani & Tahami, 2017a) |
| Eligibility assessment | Full-text review ensured studies used RHA, BA, or PSA as fillers and reported Marshall parameters per inclusion criteria. | Studies eligible for analysis. | (Mistry et al., 2019) |
| Data extraction | Collecting primary data from each study (type and source of filler, dosage, Marshall parameters, performance trends). | Structured dataset from selected studies. | (Remisova, 2015), (Putri et al., 2020) |
| Study categorization | Grouping studies based on filler type (RHA, BA, PSA) for focused analysis. | Study categories by type of ash. | (Mistry et al., 2019), (Arabani & Tahami, 2017) |