Sugarcane Bagasse Ash (SCBA)-Blended Geopolymer Concrete – A Comprehensive Review

Sugarcane Bagasse Ash (SCBA)-Blended Geopolymer Concrete – A Comprehensive Review

Upesh Kashyap

M.Tech Scholar,

Civil Engineering Department Vishwavidyalaya Engineering College, Ambikapur, Chhattisgarh, India

Ankit Raj Nirala

Assistant Professor,

Civil Engineering Department Vishwavidyalaya Engineering College, Ambikapur, Chhattisgarh, India

Dr. R. N. Khare

Principal,

Civil Engineering Department Vishwavidyalaya Engineering College, Ambikapur, Chhattisgarh, India

Abstract – The high carbon footprint of Ordinary Portland Cement (OPC) has accelerated the shift toward sustainable binder systems such as geopolymer concrete (GPC). Sugarcane Bagasse Ash (SCBA), a widely available agro-industrial waste rich in amorphous silica, has emerged as a promising precursor for alkali-activated binders. This review critically examines recent advancements (20212025) related to SCBA processing, chemicalmineralogical characteristics, mechanical strength development, durability enhancement, activator chemistry, microstructural behavior, and life-cycle impacts when used in geopolymer concrete. Literature findings indicate that optimized SCBA fineness, controlled burning, and balanced blending with fly ash or GGBS can improve compressive strength, permeability resistance, and environmental performance under ambient curing conditions. However, large variations in SCBA composition, lack of standardized processing guidelines, limited high-temperature and long-term durability data, and minimal field-scale deployment remain major barriers to practical adoption. Continued research focused on quality control, mix proportion optimization, and codal acceptance is essential to establish SCBA-based GPC as a reliable low-carbon construction technology.

Keywords – Geopolymer concrete; Sugarcane bagasse ash; Alkali activation; Sustainability; Durability; Mechanical properties.

1. INTRODUCTION

   Global CO emissions and resource depletion associated with OPC production have driven research toward alternative binders based on industrial and agricultural wastes [21], [22]. Geopolymers (alkali-activated alumino-silicate binders) present lower embodied carbon and can valorize wastes such as fly ash, slag, and agro-waste ashes [23], [27]. Sugarcane Bagasse Ash (SCBA), a by-product of sugar mills, has received increasing attention because of its silica content and widespread availability in tropical sugarcane regions; several recent reviews emphasize its dual role as a supplementary cementitious material (SCM) in OPC and as a precursor in geopolymeritious systems [1], [21], [22]. Compared to fly ash and GGBS, SCBA remains less studied within fully alkali- activated geopolymer systemsespecially with respect to comprehensive mechanical, durability, thermal and life-cycle evaluationscreating a strong motivation for systematic review and further research [1], [2], [3], [4], [27].

2. Methodology

   A systematic methodology was adopted to ensure comprehensive and unbiased coverage of existing research related to the utilization of Sugarcane Bagasse Ash (SCBA) in geopolymer concrete [21], [22], [1].

   1. Data Sources and Search Strategy.

      Major academic databases used included Scopus, ScienceDirect, SpringerLink, Taylor & Francis, MDPI, and Google Scholar (as a supplementary source) [21], [22], [23]

      Search strings included combinations of:

      • Sugarcane Bagasse Ash
      • Geopolymer Concrete
      • Alkali-activated binder
      • SCBA-based concrete
      • Sustainable binders
      • Durability of geopolymer concrete
      • Waste-based construction materials [21], [22], [1], [27]
   2. Inclusion Criteria

      Studies were selected based on:

      • Year of publication: 20212025
      • SCBA used as precursor or partial binder replacement [1], [3], [4]
      • Experimental results reported on:
        • Mechanical strength[1], [2], [3], [6]
        • Durability behavior [6], [9], [16], [17]
        • Microstructural characterization (SEM, XRD, FTIR, EDS) [1], [5], [6]
        • Activator chemistry and curing conditions [2], [4], [5], [27]
      • Peer-reviewed journal or reputed conference proceedings [21], [22]
   3. Exclusion Criteria

      Studies were excluded if:

      • SCBA was used only as OPC replacement** without geopolymer activation focus
      • Data was inadequately reported or unclear
      • Full-text inaccessible
      • Non-scientific articles (e.g., theses, patents, blogs)
   4. Screening and Selection Process

      A total of 95 documents were initially identified. After removing duplicates and applying inclusion/exclusion criteria:

      Screening Stage	Number of Papers
      Initially identified	95
      After duplicate removal	78
      Excluded based on relevance	39
      Full-text reviewed	39
      Final studies included	32

   5. Quality Evaluation

      Selected articles were validated based on:

      • Test methodology consistency (ASTM/IS standards)
      • Statistical significance of results
      • Mix proportion clarity
      • Reliability of microstructural interpretations

        Only the most scientifically robust and relevant studies were considered for synthesis and discussion in the subsequent sections.

3. SCBA: Chemical & Physical Characteristics

   SCBA is obtained as a residue from the combustion of sugarcane bagasse in boilers [21], [24], [25]. Its composition and reactivity depend mainly on:

   1. • Combustion temperature (500800°C recommended) [24], [26]
      • Airfuel ratio and residence time [24], [25]
      • Grinding fineness and sieving [24], [26]
      • Loss on Ignition (LOI) representing unburnt carbon
   [21], [24]

   Key Chemical Composition Ranges Reported [21], [24], [25]

   Parameter	Typical Range	Influence
   SiO	4575%	Pozzolanic reactivity
   AlO	412%	Geopolymer gel formation
   CaO	39%	Early strength facilitation
   LOI	< 10% (ideal)	Low carbon and high reactivity

   SCBA containing high amorphous silica improves geopolymerization by enhancing dissolution and bonding with alkaline activators [21], [24], [1]. Meanwhile, excess crystalline silica or high LOI leads to lowreactivity and poor strength. [25], [26], [22]

4. SCBA IN ORDINARY PORTLAND CEMENT (OPC) SYSTEMS

   SCBA has been widely used as a supplementary cementitious material (SCM). When partially replacing OPC, it participates in pozzolanic reactions, forming additional CSH gel and refining microstructure [21], [23], [13], [14].

   1. Strength Performance Trend
      

      SCBA Replacement	Mechanical Effect	Remarks
      510%	Increase in Later-age strength (728 days) [13], [14], [21]	Best performance window
      1015%	Strength nearly comparable [13], [15], [14]	Depends on grinding level
      >1520%	Decrease in Early strength & workability [13], [14], [20]	Due to high water demand and dilution effect

   2. Durability Observations
      • Decrease in Chloride ion penetration [13], [14], [16], [17], [21]
      • Decrease in Water absorption & permeability [13], [14], [17], [20]
      • Increase in Resistance to sulfate and mild acid exposure [16], [17], [20], [21]

        These enhancements occur primarily when SCBA is processed to improve fineness and reduce carbon content [21], [24], [26]..

   3. Relevance to Geopolymer Research

      OPC-based studies provide strong evidence supporting the suitability of SCBA as a functional component in geopolymer concrete, based on the following roles:

      • Silica contributor – SCBA contains a high proportion of amorphous silica, which readily dissolves in alkaline activators and contributes to the formation of aluminosilicate gel networks. This reactive silica accelerates geopolymerization and enhances structural bonding within the matrix. [21], [24], [25 ]
      • Micro-filler – The fine particle size of well-processed SCBA enables it to act as an effective micro-filler, filling voids between larger precursor particles. This improves particle packing density, reduces porosity, and strengthens the interfacial transition zone (ITZ), leading to a denser and more durable geopolymer matrix. [13], [14], [21]
      • Strength enhancer at optimal dosage – At controlled replacement levels, SCBA improves compressive, tensile, and flexural strength by enhancing gel formation and refining the pore structure. However, this benefit is maximized only at optimum dosages typically 515%beyond which high carbon content or excessive surface area may begin to lower performance. [13], [14], [21], [15]

   This provides a scientific foundation for SCBA integration into alkali-activated geopolymer binders, which is discussed in Section V.

5. SCBA IN GEOPOLYMER CONCRETE (GPC) AND ALKALI-ACTIVATED SYSTEMS

   The incorporation of Sugarcane Bagasse Ash (SCBA) in geopolymer concrete (GPC) has been widely investigated due to its amorphous silica content, which enhances geopolymerization under alkaline activation [1], [2], [3], [4], [5].. This section provides a detailed review of mix design strategies, mechanical performance, durability behavior, activator chemistry, and microstructural evolution in SCBA- based GPC [1], [3], [4], [5], [6], [7].. The discussion is structured into seven subsections for clarity.

   1. Fly AshSCBA Blended Geopolymer Systems

      Fly ash (FA) is the most common precursor for geopolymerization, predominantly producing **N-A-S-H gel under alkaline conditions [1], [2], [3], [4], [5]. When SCBA (rich in silica) is partially used as a replacement for FA, several studies report:

      1. Strength Development
         • Optimum SCBA content: 520% replacement of FA [1], [3], [4], [5], [8]
         • 28-day compressive strength increases by 8 25% (reported in controlled-fineness SCBA) [1], [3], [4], [5], [6]
         • Enhanced tensile and flexural strengths due to refined pore structure [1], [3], [5], [6], [7]
      2. Ambient Curing Feasibility

         Earlier GPC required heat curing, but SCBA- blended FA systems have shown satisfactory strength under:

         • Ambient curing (2535°C) [1], [3], [4], [5], [8]
         • Moist curing in certain optimized mixes [4], [5], [6]
      3. Reactive Silica Contribution

         Finely processed SCBA supplies soluble silica which:

         • Enhances dissolution in early geopolymerization [1], [2], [3], [4], [24], [26]
         • Refines gel structure [1], [3], [5], [6]
         • Reduces voids in the interfacial transition zone (ITZ) [1], [3], [5], [6]

           However, unprocessed SCBA (high LOI, crystalline silica) may reduce strength, emphasizing the need for preprocessing.

   2. Effect of Activator Concentration and Activator Ratios

      Activator chemistry plays a central role in controlling geopolymer reaction kinetics. SCBA-added systems respond strongly to variations in NaOH concentration, sodium silicate ratio, and alkaline-to-binder proportion [1], [2], [4], [5], [27].

      1. NaOH Molarity
         • Strength increases up to 1214 M [1], [2], [4], [5]
         • Above 14 M, workability drops and marginal strength gain is observed [2], [4], [5]
         • High molarity Higher dissolution but

           Higher viscosity [2], [4], [5], [27]

      2. Sodium Silicate to Sodium Hydroxide Ratio (NaSiO/NaOH)
         • Optimum ratio: 1.5 to 2.5 [1], [2], [4], [5]
         • Higher ratio increases silica availability

           denser gel [1], [5], [27]

         • Excessive ratio leads to drying shrinkage and rapid setting [2], [4], [27]
      3. Alkaline-to-Binder Ratio
         • Typical effective range: 0.350.55 [1], [4], [5], [27]
         • Too low insufficient dissolution [1], [2], [4]
         • Too high increased porosity after

           evaporation [2], [4], [27]

           In SCBA-rich geopolymer mixes, the additional reactive silica reduces the need for high sodium silicate dosage, improving overall cost efficiency and enhancing gel formation [1], [3], [4], [5].

   3. SCBA + GGBS and Multi-Waste Blended Geopolymers

      Ground Granulated Blast Furnace Slag (GGBS) introduces calcium, enabling the formation of C-A-S-H gel, improving early strength in blended geopolymer systems [1], [3], [5], [8],

      [27].
      1. Benefits of SCBA + GGBS Blends
         • Significantly higher early strength (17 days) [1], [3], [5], [8], [27]
         • Ambient curing becomes fully feasible [3], [5], [8], [27]
         • Improved workability compared to pure SCBA blends [3], [8], [7]
         • Hybrid gel formation (N-A-S-H + C-A-S-H)

           reduced pore connectivity [1], [3], [5],

           [6], [27]
      2. Optimal Proportions
         • GGBS: 2040% [1], [3], [5], [8]
         • SCBA: 1020% [1], [3], [5], [6]
         • FA balance provides alumina content for proper geopolymer bonding [1], [3], [4], [5]

           p>Such multi-waste blends align strongly with circular economy principles and optimize the reactivity profile of blended geopolymers [27].

   4. Workability and Fresh Properties

      The incorporation of SCBA generally leads to reduced workability in geopolymer concrete due to changes in particle characteristics and mix rheology. Multiple studies consistently report slump reduction with increasing SCBA percentage [3], [5], [6], [8], [14], [18].

      1. Higher Surface Area

         SCBA particles typically exhibit high fineness and porous morphology, increasing water/activator demand and reducing slump [3], [5], [6].

      2. Irregular Particle Morphology

         Angular and rough particles increase interparticle friction, contributing to reduced flowability [3], [5], [14].

      3. High LOI (if unburnt carbon present)

         Presence of unburnt carbon (elevated LOI) significantly lowers workability because carbon absorbs part of the activator solution [2], [3], [8].

      4. Solutions Reported
         • Use of polycarboxylate-based superplasticizers [5], [14], [18].
         • Finer grinding of SCBA [2], [3], [8].
         • Adjusting activator viscosity (lower NaSiO/NaOH ratio) [6], [13], [27].
         • Optimized aggregate grading [14], [18].
   5. Durability Performance

      Durability has consistently emerged as one of the strongest advantages of SCBA-blended geopolymer concrete (GPC). The enhancement is primarily attributed to refined pore structure, improved gel formation, and reduced calcium-driven degradation mechanisms [4], [5], [6], [7], [14], [18].

      1. Water Absorption & Permeability
         • Studies report 1235% reduction in water absorption compared to control mixes due to pore refinement and improved geopolymeric gel packing [4], [5], [7], [14].
         • Improved densification of the interfacial transition zone (ITZ) is repeatedly observed in SEM/XRD analyses [5], [14], [18].
      2. Chloride Penetration
         • SCBAGPC demonstrates significantly lower charge passed in RCPT, indicating reduced chloride diffusivity [6], [7], [18].
         • This makes SCBA-based GPC promising for marine, coastal, and chloride-laden environments [7], [14].
      3. Sulfate & Acid Resistance
         • SCBA reacts minimally with sulfate ions compared to OPC, reducing expansive degradation [4], [6], [7]
         • SCBA-containing GPC retains higher residual strength after acidic exposure, attributed to lower CaO content and dense aluminosilicate matrix [5], [14], [18].
      4. Freeze-Thaw Resistance
         • Although research is still limited, existing experimental results indicate good freeze thaw stability when SCBA is finely processed and used in optimum proportions [7], [14].
      5. High-Temperature Resistance
         • SCBA-blended GPC shows moderate thermal stability up to ~600°C, retaining strength due to stable aluminosilicate gels [6], [18].
         • Above 600°C, microcracking and structural distress increase due to dehydration and matrix shrinkage [18], [27].
         • Overall, systematic high-temperature studies remain scarce, marking a clear research gap [6], [7].
   6. Environmental & Life-Cycle Considerations

      Life-cycle assessment (LCA) studies consistently emphasize that Sugarcane Bagasse Ash (SCBA) contributes to significant sustainability gains when incorporated into geopolymer concrete. The overall environmental impact depends on processing efficiency, local sourcing, and activator chemistry [11], [12], [14], [17], [22].

      1. Environmental Benefits
         • Utilizing SCBA reduces the disposal burden associated with sugar mill waste and minimizes landfill accumulation [11], [12].
         • LCA results indicate substantial reductions in key environmental indicators:
           • CO emissions lowered by 1840%, depending on mix design and activator dosage [11], [12], [17].
           • Reduced natural resource consumption, as SCBA partially replaces virgin materials such as fly ash or GGBS [14], [22]
           • Lower ecological footprint in terms of waste management and transportation when sourced locally [11], [17]
      2. Cost Performance
         • SCBA-blended mixes generally show lower binder cost when SCBA is locally available, as it replaces more expensive precursors or OPC [11], [14], [17].
         • However, alkaline activators remain the costliest component in geopolymer production:
           • Sodium silicate
           • Sodium hydroxide

             Both significantly influence total cost, making activator optimization crucial [12], [17].

      3. Sustainability Concerns

         Both significantly influence total cost, making activator optimization crucial [12], [17].

         • Grinding, sieving, or controlled calcination can increase energy consumption and carbon footprint if not optimized [12], [17], [22].
         • Sodium silicate production carries notably high embodied energy and CO emissions, often dominating the LCA profile of GPC [11], [12].
         • Because of these trade-offs, a comprehensive LCA that includes ash processing energy, activator production, transportation, and mix design variables is essential for accurate sustainability evaluation [11], [12], [17].
   7. Microstructure and Reaction Mechanisms

      The microstructural performance of SCBA-blended geopolymer concrete is strongly influenced by its amorphous silica content, which enhances geopolymer gel formation and densifies the matrix. Multiple studies provide consistent evidence through SEM, XRD, EDS, and FTIR analyses [4], [5], [6], [7], [14], [18].

      1. Gel Phases Formed
         • N-A-S-H gel (sodium aluminosilicate hydrate) forms the primary binding phase in FASCBA geopolymer systems. Supported by [4], [5], [6].
         • C-A-S-H gel forms when GGBS is added, contributing to early strength and hybrid gel networks [5], [7], [14].
         • SCBA supplies secondary silica, enhancing gel polymerization and matrix compactness [4], [5], [18].
      2. SEM Observations

         Consistent SEM evidence shows that SCBA improves matrix morphology due to its filler effect and reactive silica [4], [5], [14], [18]:

         • Reduced microcracks
         • Fewer capillary voids
         • More compact and homogeneous geopolymer matrix
      3. XRD Findings

         XRD results from various studies show clear mineralogical trends [4], [5], [6], [14]:

         • Decrease in crystalline quartz peaks when SCBA is finely processed, indicating increased amorphous content.
         • Enhanced amorphous hump (20°35° 2), representing improved geopolymer gel formation.
      4. FTIR

         FTIR spectra commonly show a shift ofthe Si OT asymmetric stretching band from 10001100 cm¹, indicating higher degrees of polymerization in SCBA-blended matrices [5], [6], [18].

         This confirms:

         • Stronger AlSi network formation
         • Greater geopolymerization efficiency
         • Improved bonding with alkaline activators
6. Key Challenges & Research Gaps

   Based on the comprehensive literature review, several critical challenges and research gaps continue to limit the widespread adoption of SCBA-based geopolymer concrete (GPC). These are consistently highlighted across experimental studies and review papers [2], [3], [4], [6], [7], [14], [18], [22].

   • Raw-material variability & standardization SCBA composition varies significantly across mills and combustion practices; standardized processing (controlled combustion, LOI limits, particle fineness) and characterization protocols are required to ensure reproducible performance. [2], [3], [4], [18], [22]
   • Limited durability and long-term performance evidence Current research on SCBA-based GPC offers only short-term insights, while extended durability evaluationssuch as multi- year exposure, realistic freezethaw cycles, and chloride diffusion over service-like conditions are still largely missing. This lack of long-term data creates uncertainty about field performance. [6], [7], [14], [18]
   • Thermal behavior systematic studies on high- temperature and fire resistance specific to SCBA- GPC are scarce. [6], [7], [18]
   • Scale-up & field trials there are few comprehensive field demonstrations of SCBA- GPC, especially in developing country contexts where SCBA is abundant. [7], [14], [22]
   • Absence of standards and codified guidelines There are no established national or international codes that specify requirements for SCBA processing, characterization, or its use in geopolymer concrete. This shortage of codified guidance significantly limits industrial adoption and regulatory acceptance. [2], [3], [22]
7. RECOMMENDATIONS & FUTURE RESEARCH DIRECTIONS

   To advance SCBA-based geopolymer technology, research and practice should focus on:

   • Developing standardized preprocessing protocols (LOI limits, particle size, thermal treatment) and characterization checklists for SCBA.
   • Optimizing multi-waste blends (FA + SCBA + GGBS) with attention to gel chemistry to maximize mechanical/durability performance while minimizing activator demand.
   • Conducting long-term durability and high- temperature experiments and establishing predictive models for service life
   • A more comprehensive evaluation of environmental impact and economic feasibility is required, particularly analyses that account for the energy consumed in SCBA processing and the embodied energy of alkaline activators, in order to accurately determine the overall sustainability benefits of SCBA-based GPC..
   • Implementing pilot field projects and liaising with standards bodies to build normative data for code adoption.
8. CONCLUSIONS

Sugarcane Bagasse Ash (SCBA) is an emerging sustainable precursor for developing low-carbon cementitious and geopolymer binders. This review demonstrates that SCBA, when properly processed through controlled combustion and fine grinding, provides a reactive source of amorphous silica that significantly contributes to the formation of geopolymeric gel phases. Blending SCBA with fly ash or GGBS can produce geopolymer concrete with competitive compressive strength, enhanced durability, reduced water absorption, and improved chemical resistance compared to both traditional OPC and single-precursor geopolymer systems.

Despite these strengths, large-scale implementation is currently limited by variations in SCBA chemical composition, lack of preprocessing standards, insufficient long-term durability data, and limited field-scale

demonstrations. Performance is highly sensitive to activator concentration, precursor blend proportions, curing regime, and SCBA fineness, indicating the need for optimized mix-design approaches. Environmental assessments show meaningful reductions in embodied carbon when SCBA replaces energy- intensive materials, although activator production remains a major contributor to overall environmental impact.

To advance SCBA-based geopolymer technology into practical construction applications, coordinated research is needed on material standardization, kinetic modeling, multi- year durability evaluation, structural-scale field trials, and codal development. With systematic quality control and scientific validation, SCBA has the potential to become a reliable, cost-effective, and environmentally responsible component in next-generation sustainable concrete.

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