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<p>This laboratory investigation examines the performance and durability of recycled asphalt pavement (RAP) incorporated as coarse aggregate replacement at 0%, 15%, 30%, and 45% by volume of total coarse aggregate in geopolymer roller-compacted concrete (RCC). Fly ash (FA) and ground granulated blast furnace slag (GGBFS) in combination were used as binder materials with a FA: GGBFS ratio of 70:30 by mass (corresponding to a molar SiO₂/Al₂O₃ ratio of 2.10 and a mass-based SiO₂/Al₂O₃ ratio of 2.05). These binders were activated using 12&#xa0;M NaOH and Na₂SiO₃ solutions at an L/B ratio of 0.45. Linear regressions using <i>n</i> = 12 samples showed negative correlations of RAP replacement with physical properties. Optimum moisture content reduced with RAP addition OMC = 11.2 − 0.31R [%], with 95% CI for slope of − 0.35 to − 0.27 and R² = 0.93, and maximum dry density decreased with MDD = 2389 − 1.58R [kg/m³], with 95% CI for slope of − 1.74 to − 1.42 and R² = 0.92, where R = %RAP replacement. Mechanical performance showed early-age 7-day strength ranging from 49.3% (control) to 39.3% (RAP-45) of 90-day strength, with final strength reductions of 6.6%, 14.1%, and 22.9% for RAP-15, RAP-30, and RAP-45, respectively (absolute 90-day strengths of approximately 48.2, 45.0, 41.3, and 37.2&#xa0;MPa). Durability characterization identified: acid resistance following power-law behaviour ML(t) = αt^β (R² = 0.97); chloride penetration following Q = Q₀(1 + 0.009R) (R² = 0.92); and freeze-thaw resistance following DF = DF₀·exp(− kR) (R² = 0.90). These regression equations are provided as descriptive empirical relationships, rather than validated predictive tools because they were developed from only four RAP levels ( <i>n</i> = 12). The proposed indicative ranges based on laboratory performance when subjected to accelerated conditions are: ≤15% RAP for severe exposure (strength &gt; 40&#xa0;MPa, DF &gt; 88); ≤30% RAP for moderate exposure (strength &gt; 35&#xa0;MPa, DF &gt; 83); ≤45% RAP for mild exposure (strength &gt; 30&#xa0;MPa, DF &gt; 76). These values still need confirmation from field observations prior to implementation into design specifications. Preliminary economic and environmental analysis estimates show roughly 18–25% decrease in material costs and 65–75% decrease in CO₂ emissions with 30% RAP as compared to conventional OPC concrete (system boundaries are cradle to gate; cost data is site specific to local market).</p>

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RAP-Incorporated Geopolymer Roller-Compacted Concrete: Regression-Based Performance Models and Environment-Specific Design Thresholds

  • 期刊论文

  • 发表日期：

    2026年7月8日

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  • M. Harish Sagar,
  • H. T. Avinash

摘要

This laboratory investigation examines the performance and durability of recycled asphalt pavement (RAP) incorporated as coarse aggregate replacement at 0%, 15%, 30%, and 45% by volume of total coarse aggregate in geopolymer roller-compacted concrete (RCC). Fly ash (FA) and ground granulated blast furnace slag (GGBFS) in combination were used as binder materials with a FA: GGBFS ratio of 70:30 by mass (corresponding to a molar SiO₂/Al₂O₃ ratio of 2.10 and a mass-based SiO₂/Al₂O₃ ratio of 2.05). These binders were activated using 12 M NaOH and Na₂SiO₃ solutions at an L/B ratio of 0.45. Linear regressions using n = 12 samples showed negative correlations of RAP replacement with physical properties. Optimum moisture content reduced with RAP addition OMC = 11.2 − 0.31R [%], with 95% CI for slope of − 0.35 to − 0.27 and R² = 0.93, and maximum dry density decreased with MDD = 2389 − 1.58R [kg/m³], with 95% CI for slope of − 1.74 to − 1.42 and R² = 0.92, where R = %RAP replacement. Mechanical performance showed early-age 7-day strength ranging from 49.3% (control) to 39.3% (RAP-45) of 90-day strength, with final strength reductions of 6.6%, 14.1%, and 22.9% for RAP-15, RAP-30, and RAP-45, respectively (absolute 90-day strengths of approximately 48.2, 45.0, 41.3, and 37.2 MPa). Durability characterization identified: acid resistance following power-law behaviour ML(t) = αt^β (R² = 0.97); chloride penetration following Q = Q₀(1 + 0.009R) (R² = 0.92); and freeze-thaw resistance following DF = DF₀·exp(− kR) (R² = 0.90). These regression equations are provided as descriptive empirical relationships, rather than validated predictive tools because they were developed from only four RAP levels ( n = 12). The proposed indicative ranges based on laboratory performance when subjected to accelerated conditions are: ≤15% RAP for severe exposure (strength > 40 MPa, DF > 88); ≤30% RAP for moderate exposure (strength > 35 MPa, DF > 83); ≤45% RAP for mild exposure (strength > 30 MPa, DF > 76). These values still need confirmation from field observations prior to implementation into design specifications. Preliminary economic and environmental analysis estimates show roughly 18–25% decrease in material costs and 65–75% decrease in CO₂ emissions with 30% RAP as compared to conventional OPC concrete (system boundaries are cradle to gate; cost data is site specific to local market).