Evaluation of Bagasse Ash as Cement and Sand Replacement for the Production of Engineered Cementitious Composites (ECC)

The objective of this study was to develop novel Engineered Cementitious Composites (ECC) materials implementing sugarcane bagasse ash (SCBA). To this end, the effects on the mechanical and physical properties of ECC materials of: (1) Louisiana raw SCBA (RBA) as a partial and complete replacement of sand (i.e., class S mixtures); (2) Louisiana post-processed SCBA (PBA) as a partial replacement of cement (i.e., class C mixtures); and (3) Ecuador raw SCBA (EBA) as a partial and complete replacement of sand (i.e., class S-E mixtures) were studied. Sand replacement levels with RBA and EBA evaluated were 25, 50, 75, and 100% (by volume), while cement replacement levels with PBA studied were 40, 50, and 60% (by mass). RBA and EBA were subjected to minor processing by drying and sieving to remove moisture and coarse impurities. On the other hand, PBA was produced by further processing of RBA through burning and grinding. RBA and EBA were mainly composed of silica; yet, presented high carbon content and large particle size relative to cement. Conversely, PBA exhibited low carbon content and small particle size. Tests conducted for class S and class C mixtures included compressive strength, uniaxial tensile, surface resistivity, shrinkage, coefficient of thermal expansion, and slant shear tests. In the case of S-E mixtures, tests conducted included compressive strength and flexural strength tests. The use of RBA as sand replacement caused minor reductions in the compressive strength of ECC (up to 11%), yet it produced a dramatic improvement in the tensile ductility (up to 311%). Moreover, the tensile strength of all RBA admixed ECC also improved (up to 22.3%). Implementation of RBA also produced a decrease in surface resistivity and an increase in shrinkage. For class S-E mixtures, the implementation of EBA as sand replacement produced an increase in compressive strength and flexural strength. For class C mixtures, the implementation of PBA as cement replacement produced significant reductions in compressive strength (up to 39.1%) and tensile strength (up to 28.1%). Nevertheless, it increased the tensile ductility of the composites (up to 85%). Furthermore, the surface resistivity and shrinkage of PBA admixed ECC increased with the increment in cement replacement with PBA.本研究旨在开发掺加甘蔗渣灰（sugarcane bagasse ash, SCBA）的新型工程水泥基复合材料（Engineered Cementitious Composites, ECC）。为此，本研究探究了三类因素对ECC材料力学与物理性能的影响：(1) 路易斯安那原生甘蔗渣灰（Louisiana raw SCBA, RBA）部分或完全替代砂（即S类配合比）；(2) 路易斯安那后处理甘蔗渣灰（Louisiana post-processed SCBA, PBA）部分替代水泥（即C类配合比）；以及(3) 厄瓜多尔原生甘蔗渣灰（Ecuador raw SCBA, EBA）部分或完全替代砂（即S-E类配合比）。针对RBA与EBA，评估的砂替代率（体积计）为25%、50%、75%及100%；而针对PBA，研究的水泥替代率（质量计）为40%、50%及60%。RBA与EBA仅经过干燥与筛分的简易处理，以去除水分与粗杂质。与之相对，PBA系通过对RBA进一步煅烧与粉磨制备而成。RBA与EBA的主要成分为二氧化硅，但相较于水泥，其碳含量较高且粒径更大。反之，PBA的碳含量较低且粒径更小。针对S类与C类配合比，测试项目包括抗压强度、单轴拉伸、表面电阻率、收缩率、热膨胀系数及斜剪试验。对于S-E类配合比，测试项目仅涵盖抗压强度与抗折强度试验。采用RBA替代砂会使ECC的抗压强度小幅降低（最大降幅达11%），但可显著提升其拉伸延性（最大提升幅度达311%）。此外，所有掺加RBA的ECC的抗拉强度也有所提升（最大增幅达22.3%）。使用RBA还会降低表面电阻率并增大收缩率。对于S-E类配合比，采用EBA替代砂可提升其抗压强度与抗折强度。对于C类配合比，采用PBA替代水泥会使抗压强度（最大降幅达39.1%）与抗拉强度（最大降幅达28.1%）出现显著降低。不过，这可提升复合材料的拉伸延性（最大提升幅度达85%）。此外，随着PBA替代水泥比例的提升，掺加PBA的ECC的表面电阻率与收缩率均随之升高。