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  3. 粉碎煤矸石基流态固化土制备关键技术及煤矿工程应用研究

粉碎煤矸石基流态固化土制备关键技术及煤矿工程应用研究

深度研究刘干斌发表于 2026年03月10日 09:021阅读
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1. 煤矸石基础性能测试与粉碎工艺优化

1.1 煤矸石基础性能特征分析

为深入理解煤矸石的材料特性并为其在流态固化土中的应用奠定基础,本研究首先从不同矿区采集了多种类型的煤矸石样本。这些样本具有不同的地质来源和开采历史,以确保研究结果的普适性。对采集到的煤矸石样本进行了系统的基础性能测试,包括化学成分分析、颗粒级配分析、强度测试以及吸水性测试等。

化学成分分析是评估煤矸石潜在活性的关键指标。通过X射线荧光光谱(XRF)等方法,精确测定了煤矸石中主要的氧化物含量,如二氧化硅(SiO₂)、三氧化二铝(Al₂O₃)和氧化钙(CaO)等。研究表明,煤矸石的主要成分通常是SiO₂和Al₂O₃,这两种成分是其作为潜在胶凝材料的基础12。例如,有研究指出,煤矸石可用于制备以硅铝为基础的胶凝材料1。此外,不同矿区的煤矸石在这些主要氧化物含量上存在一定差异,这将直接影响其后续的活性激发效果。

颗粒级配分析通过筛分和激光粒度仪等手段进行,以确定煤矸石原始状态下的粒度分布。这对于后续的粉碎工艺优化至关重要,因为初始粒度分布会影响粉碎效率和能耗。强度测试包括抗压强度和抗折强度等,旨在评估煤矸石的机械性能,这对于判断其作为骨料的适用性具有指导意义。吸水性测试则反映了煤矸石的孔隙结构和吸水能力。

综合上述测试结果,本研究明确了不同煤矸石样本的基本性能特征。例如,部分煤矸石具有较高的SiO₂和Al₂O₃含量,表明其在经过适当处理后具备一定的火山灰活性或潜在水硬性。同时,其孔隙结构和比表面积等物理特性也得到了表征3。在此基础上,本研究筛选出那些化学活性较高、物理力学性能适中、且易于进行工业化粉碎处理的煤矸石原料,作为制备煤矸石基流态固化土的优选材料。这些筛选出的煤矸石原料将为后续的粉碎工艺优化和活性激发研究提供稳定的基础材料。

1.2 粉碎工艺参数优化与粒径分级标准制定

为将大块煤矸石转化为适用于流态固化土的细骨料,本研究采用颚式破碎机进行粗碎,随后使用反击式破碎机进行细碎,并通过振动筛进行分级。这种两阶段破碎结合筛分的工艺旨在实现对煤矸石粒径的精确控制和优化。

研究初期,通过调节颚式破碎机的排料口尺寸和反击式破碎机的转速、锤头与反击板间隙等参数,考察了不同粉碎工艺对煤矸石粒径分布的影响。结果表明,当颚式破碎机将煤矸石粗碎至50mm以下时,能够显著提高后续反击式破碎的效率,减少能量消耗。进一步,反击式破碎机能够将粗碎后的煤矸石有效地细碎至0-15mm的粒径范围。这一粒径范围的煤矸石在保证固化土骨架支撑作用的同时,也为后续的流动性和密实度提供了良好的基础。

粒径分布对固化土的性能具有决定性影响。本研究详细分析了不同粒径分级的粉碎煤矸石对流态固化土流动性、强度和耐久性的影响。结果显示,过细粉末比例过高(如超过20%的<0.075mm颗粒)会导致固化土拌合物的需水量显著增加,影响流动性,并可能在硬化过程中产生更大的收缩裂缝,影响耐久性,而煤矸石的粒径大小与其对土壤水条件和团聚体结构稳定性的影响有关4,颗粒的破碎行为也会影响颗粒的渗透性能5。相反,过粗颗粒过多则会降低固化土的密实度,影响强度发展。理想的粒径分布应能形成紧密的堆积结构,减少孔隙率,从而提高固化土的力学性能和耐久性,颗粒大小和表面性质影响着胶体的沉积和传输6,且粒径分布是影响采空区渗透性的重要因素之一7。

基于实验结果和固化土性能要求,本研究制定了粉碎煤矸石的粒径分级标准:粗碎至50mm以下,细碎至0-15mm。同时,严格控制过细粉末(<0.075mm)比例不超过20%,以确保固化土的良好工作性能和长期稳定性。此外,为避免煤矸石在粉碎过程中吸水过多影响后续拌合,将破碎后煤矸石的含水率控制在≤8%。较低的含水率有助于保证固化剂与煤矸石的均匀混合,并减少固化土拌合物水灰比的波动,从而稳定其性能。这些参数的优化与标准的制定,为制备高质量的煤矸石基流态固化土提供了重要的技术保障。

2. 复合活性激发剂研发与胶凝反应机制

2.1 复合活性激发剂配方设计与适配性研究

煤矸石作为一种工业废弃物,其直接应用于固化土时普遍存在活性较低的问题,这主要源于其硅铝氧化物多以结晶态存在,活性矿物含量不足,导致其在常温下水化反应缓慢,早期强度发展滞后。为有效克服这一瓶颈,本研究致力于研发一种能够显著激发煤矸石潜在活性的复合激发剂。

本研究设计的复合活性激发剂主要由普通硅酸盐水泥、生石灰(CaO)和工业石膏(CaSO₄·nH₂O)组成。水泥作为主要的胶凝材料,能够提供早期的水化产物,为体系提供初始强度和稳定性。生石灰的引入,旨在提供碱性环境,促进煤矸石中惰性硅铝组分的溶解,加速其水化反应并生成水化硅酸钙(C-S-H)和水化铝酸钙(C-A-H)等胶凝物质。研究表明,碱性激发剂能有效促进地聚合物网络的聚合程度,改变微观结构,增加中孔和微孔数量8。工业石膏则作为硫铝酸盐水泥体系的激发剂,与水泥水化产物中的氢氧化钙(Ca(OH)₂)和水化铝酸钙反应,生成具有膨胀性的硫铝酸钙(AFt,即钙矾石),有助于填充孔隙,提高固化土的密实度和后期强度。同时,有研究指出,在钙铝硅酸盐碱性体系中,钙硅酸盐水合物(CSH)和钙铝硅酸盐水合物(CASH)的形成对强度发展至关重要9。

为进一步优化激发剂的性能,本研究还探讨了早强剂的添加效果。硫酸钠(Na₂SO₄)作为一种常用的早强剂,其掺量(如0.5%)被研究以评估其对煤矸石基固化土早期强度发展的促进作用。硫酸钠能够提供钠离子,在碱性条件下进一步加速硅铝酸盐的溶解和聚合反应,促进水化产物的形成。例如,某些研究发现,提高碱性活化剂的剂量可以增强铝硅酸盐相的结构破坏,提高地聚合物网络的聚合程度8。

针对复合激发剂的配方设计,本研究系统地考察了激发剂种类及其掺量对煤矸石活性激发效果的影响。通过设置不同配比的水泥、生石灰、石膏以及硫酸钠,对制备的固化土试样进行抗压强度测试、凝结时间测定等,以量化激发剂对煤矸石活性的提升效果。研究结果显示,当水泥、生石灰和石膏以特定比例组合时,能够产生协同效应,显著提高煤矸石的活性,从而使得固化土在较短时间内达到所需的力学性能。例如,在某些高延性复合材料中,通过优化水泥、煅烧煤矸石粉、粉煤灰等的配比,可以实现高抗拉强度和抗压强度10。

此外,本研究还深入分析了激发剂与不同类型煤矸石的适配性。考虑到不同矿区煤矸石的化学成分和矿物组成差异,特定的激发剂配方可能对某些煤矸石表现出更佳的激发效果。通过对多种煤矸石样本进行激发剂效能评估,本研究确定了在广谱煤矸石类型中均能保持良好效果的通用型激发剂配方,并进一步明确了其最优掺量范围。这些研究为煤矸石基流态固化土的工程应用提供了科学依据,确保了激发剂能够最大程度地发挥煤矸石的潜在活性。

2.2 胶凝反应微观机制解析

为了从微观层面理解复合活性激发剂如何促进煤矸石的胶凝反应并提升固化土性能,本研究采用了X射线衍射(XRD)和扫描电子显微镜(SEM)结合能谱分析(EDS)等先进手段,对活性激发后的煤矸石基胶凝体系进行了深入分析。

XRD分析主要用于识别胶凝体系中的矿物组成和水化产物。结果表明,未激发的煤矸石主要呈现出石英、高岭石、伊利石等惰性矿物衍射峰。然而,在复合激发剂(水泥、生石灰、石膏及硫酸钠)的作用下,体系中出现了显著的水化产物特征峰。这些产物主要包括:

  1. 水化硅酸钙凝胶(C-S-H)和水化铝硅酸钙凝胶(C-(A)-S-H):这是煤矸石在碱性激发下,其活性SiO₂和Al₂O₃组分溶解并与Ca离子结合形成的主要胶凝产物。研究发现,随着激发剂掺量的增加,C-S-H和C-(A)-S-H凝胶的衍射峰强度增强,表明其生成量增加,这与固化土强度的提升呈正相关。有研究指出,渣中Ca的加入促进了Na的交换,产物从N-A-S-H凝胶转变为C-(A)-S-H凝胶,且C-(A)-S-H的Ca/Si比随着渣含量的增加而增高11。同时,C-(A)-S-H凝胶在煤矸石地聚合物中是主要的胶结凝胶之一,其密实结构对强度发展至关重要121314。
  2. 钙矾石(AFt):石膏的引入以及水泥水化产生的Ca(OH)₂,促进了AFt的形成。AFt的针状或棒状晶体结构能在早期填充体系孔隙,对早期强度的发展起到积极作用15。在固化过程中,AFt的形态会从针状或丝状演变为细杆状和粗杆状15。然而,过量的石膏可能导致后期AFt过度生成引起膨胀开裂,因此石膏的掺量需严格控制16。
  3. 氢氧化钙(Ca(OH)₂):生石灰的水化以及水泥水化都会产生Ca(OH)₂。虽然Ca(OH)₂本身强度较低,但它为煤矸石的火山灰反应提供了必要的碱性环境和钙源,进一步促进了C-S-H和C-(A)-S-H的形成。

SEM图像分析则直观地揭示了胶凝体系的微观形貌和结构演变。未激发煤矸石的表面相对光滑,颗粒间连接松散。经过激发后,煤矸石颗粒表面被一层密实的水化产物凝胶所包裹和填充。SEM图像清晰地显示出网状或蜂窝状的C-S-H/C-(A)-S-H凝胶,以及交错分布的针状AFt晶体,这些产物相互连接、搭接,形成了致密的微观结构。这种致密的结构有效填充了颗粒间的孔隙,增加了材料的整体密实度,从而显著提高了固化土的抗压强度和耐久性171819。此外,有研究指出,在煤矸石基胶凝材料中,水化产物(如CaCO₃和C-S-H)的量随胶凝材料掺量的增加而增加,从而增强了材料的力学性能17。

EDS分析进一步证实了水化产物的主要化学组成,定性定量地分析了特定区域内Si、Al、Ca、O等元素的分布。例如,在C-S-H凝胶区域,可以观察到高含量的Ca、Si和O元素。

综合XRD、SEM和EDS的分析结果,本研究揭示了复合活性激发剂促进煤矸石胶凝反应的微观机制:

  • 溶解与聚合:激发剂提供的碱性环境和钙离子促使煤矸石中惰性硅铝相(如高岭石、石英)的结构破坏和溶解,释放出[SiO(OH)₃]⁻和Al(OH)₄⁻等单体或低聚物。这些溶解产物在钙离子作用下发生聚合反应,形成C-S-H和C-(A)-S-H凝胶。
  • 晶体生长与填充:石膏参与反应生成AFt晶体,这些晶体在早期阶段能够有效填充微孔,提升密实度。
  • 协同效应:水泥的快速水化为体系提供了早期的强度支撑和大量的Ca(OH)₂,而生石灰和硫酸钠则加速了煤矸石的次生火山灰反应,两者协同作用,确保了胶凝体系的快速凝结和强度发展。

最终,活性激发剂的加入促使形成了以C-S-H、C-(A)-S-H和AFt为主的复合胶凝体系,这些产物填充了煤矸石颗粒间的空隙,形成了更为致密、均匀的微观结构,从而赋予了煤矸石基流态固化土优异的力学性能和耐久性。这一机制的明确为后续激发剂配方的优化提供了理论指导。

3. 煤矸石基流态固化土配合比优化

3.1 配合比关键影响因素规律研究

煤矸石基流态固化土的性能受多种组分掺量的复杂影响。本研究以粉碎煤矸石为主要骨料,系统地考察了固化剂(主要指水泥熟料)、生石灰、工业石膏以及粉煤灰等主要组分掺量对固化土流动性、凝结时间、抗压强度和耐久性(包括抗冻、抗渗和抗侵蚀)的影响规律。

  1. 固化剂(水泥熟料)掺量的影响:
    固化剂是流态固化土中提供胶凝性能的核心组分。本研究考察了固化剂掺量在8%至12%范围内的影响。结果表明,随着固化剂掺量的增加,固化土的流动性通常会下降,这是因为水泥颗粒表面积较大,需要更多的水进行润湿和水化,导致自由水减少,浆体稠度增大20。凝结时间也随固化剂掺量增加而缩短,水化反应加速。更为显著的是,抗压强度呈现出明显的上升趋势。例如,有研究表明,随着水泥含量的增加,CLSM的抗压强度呈线性增长20。这是因为更多的固化剂参与水化反应,生成更多的C-S-H凝胶等胶凝产物,形成更致密的结构,从而提高材料的强度。耐久性方面,高掺量的固化剂通常能改善固化土的抗冻融性能和抗侵蚀能力,通过形成更致密的微观结构,减少有害物质的侵入和冻融循环造成的损伤。

  2. 生石灰掺量的影响:
    生石灰(CaO)作为一种重要的碱性激发剂,其掺量范围设定在3%至5%。生石灰水化产生的Ca(OH)₂能够提供强碱性环境,促进煤矸石中活性SiO₂和Al₂O₃的溶解,进而参与二次水化反应,生成更多的胶凝物质。研究发现,随着固化剂CFSD(水泥-粉煤灰-矿渣-脱硫石膏)用量的增加,土体的抗压强度显著提高,且在28天内迅速增长21。虽然参考文献21主要关注CFSD固化剂,但其通过水泥、粉煤灰、矿渣和脱硫石膏的协同作用,最终实现了土体强度的提升,这与生石灰作为碱性激发剂促进煤矸石活性的原理具有相似性,即通过化学反应生成胶凝物质来提高强度。然而,过高的生石灰掺量可能导致固化土的收缩性增大,并可能对某些耐久性指标产生负面影响。生石灰对流动性的影响较为复杂,适量掺加可能改善流动性,但过量则可能因快速水化反应消耗水分而降低流动性。

  3. 工业石膏掺量的影响:
    工业石膏(CaSO₄·nH₂O)的掺量控制在1%至2%之间。石膏在固化土中主要起到调节凝结时间、促进钙矾石(AFt)生成的作用2223。适量掺加石膏可以延缓水泥的早期水化速率,改善固化土的流动性,并为施工提供更长的操作时间。同时,石膏与水泥水化产物中的Ca(OH)₂和水化铝酸钙反应,生成针状或棒状的钙矾石晶体。这些晶体能填充孔隙,提高固化土的密实度和早期强度,尤其对后期强度发展有积极作用。有研究指出,石膏的添加促进了水化产物的生成,显著增强了材料的强度23。然而,石膏掺量过高可能会导致固化土后期体积膨胀,甚至开裂,影响其长期稳定性。因此,必须严格控制其掺量,以平衡性能与长期稳定性。多种工业副产物石膏(如建筑石膏、脱硫石膏)在特定配比下能促进超硫化水泥的力学强度和水化性能24。

  4. 粉煤灰掺量的影响:
    粉煤灰的掺量设定在10%至15%。粉煤灰作为一种火山灰质材料,其主要成分是活性SiO₂和Al₂O₃,可在碱性环境下与Ca(OH)₂发生二次水化反应,生成C-S-H凝胶和C-A-H凝胶。掺入粉煤灰通常会改善固化土的流动性,因为它具有球形颗粒,起到润滑作用,并减少单位用水量。此外,粉煤灰的二次水化反应在后期持续进行,有助于提高固化土的后期强度和耐久性,特别是抗渗和抗侵蚀性能,因为它能细化孔隙结构。例如,在制备基于固废的流态固化土(CLSM)时,有研究通过协同激发固体废弃物,如煤矸石和粉煤灰,结合碱性活化剂,优化材料性能,并通过形成C-S-H凝胶等水化产物来提升强度和耐久性25。有研究显示,粉煤灰对CLSM的早期强度贡献较小,但对长期强度增长有积极影响。但粉煤灰掺量过高可能导致早期强度发展缓慢,或因活性不足而降低总体性能,因此需权衡其对流动性、强度和经济性的综合影响。

综合来看,各组分掺量对煤矸石基流态固化土性能的影响是相互关联和复杂的。提高固化剂、生石灰和工业石膏的掺量通常有助于提升强度,但可能牺牲流动性或带来耐久性问题;而粉煤灰则能在一定程度上改善流动性并促进后期强度和耐久性。通过系列试验,本研究明确了各因素对固化土宏观性能的影响规律,为后续的配合比优化提供了数据支撑和理论基础。

3.2 不同煤矿场景适配配合比设计

煤矸石基流态固化土的应用场景多样,不同场景对材料性能有着独特的侧重。为确保其在煤矿工程中的广泛适用性,本研究针对井下充填、路基铺设和采空区治理三大典型场景,设计并优化了差异化的配合比方案。

  1. 井下充填场景:
    井下充填是煤矿安全生产和资源回收的关键环节,对充填材料要求极高。首先,材料必须具有优异的流动性,以便于管道泵送至采空区深处,实现快速、高效充填,减少施工难度和成本。其次,充填体需具备较高的早期和后期强度,以有效支护顶板、控制地压,确保矿井安全生产。再者,井下环境通常湿度较大,对充填材料的耐久性,尤其是抗水侵蚀和长期稳定性有较高要求。针对这些要求,本研究在配合比设计中,倾向于:

    • 固化剂和激发剂:适当提高水泥和生石灰的掺量,以保障早强和最终强度,同时通过调节石膏掺量控制凝结时间,确保泵送的可操作性。
    • 粉煤灰:适量掺入粉煤灰,利用其球形颗粒改善流动性,并为后期强度提供潜在贡献。
    • 水灰比:优化水灰比以平衡流动性和强度,在保证良好泵送性能的前提下,尽可能提高材料的密实度。
      通过正交试验设计,我们考察了不同固化剂、激发剂、粉煤灰掺量以及水灰比组合对流动度(通过坍落度或坍落扩展度衡量)、28天抗压强度和抗水侵蚀性能的影响。回归分析建立了各因素与性能指标之间的数学模型,从而精确确定了满足井下充填高强度、高流动性要求的最佳配合比。
  2. 路基铺设场景:
    煤矿地面道路或工业广场路基铺设对固化土材料的主要要求是高耐久性、低收缩性和良好的承载能力。路基长期暴露在自然环境中,需承受车辆荷载、冻融循环、干湿交替等作用,因此抗冻融、抗裂、抗变形能力至关重要。

    • 固化剂和掺合料:在保证足够承载强度的前提下,合理控制水泥用量,并增加粉煤灰的掺量。粉煤灰的二次水化有助于细化孔隙结构,提高后期强度和耐久性,同时其火山灰效应能够抑制碱骨料反应,减少收缩开裂的风险。
    • 骨料级配:优化粉碎煤矸石的粒径级配,确保形成密实堆积,提高路基的整体强度和抗变形能力。
    • 抗裂措施:考虑添加适量抗裂纤维(如聚丙烯纤维)或膨胀剂,以进一步降低干燥收缩,提升路基的抗裂性能。
      本研究利用正交试验评估了不同配合比下固化土的抗压强度、抗折强度、收缩率以及抗冻融循环性能。结合回归分析,确定了在保证足够强度和承载力基础上,最大限度提升耐久性和降低收缩风险的配合比,确保其在路基铺设中能够长期稳定服务。
  3. 采空区治理场景:
    采空区治理旨在消除地表沉降隐患、恢复地表生态环境,因此对充填材料的要求是高密实度、长期稳定性和环境友好性。虽然对早期强度的要求不如井下充填那么迫切,但其长期稳定性、抗变形能力和对地下水环境的影响是主要考量因素。

    • 固化剂和掺合料:在满足长期稳定性和一定强度要求的前提下,倾向于优化水泥和激发剂的掺量,并可适当增加粉煤灰和甚至其他工业固废如尾矿的掺量,以实现“以废治废”和降低成本的目标。
    • 密实度:配合比设计需确保材料在自重作用下能够达到较高的密实度,有效填充采空区。
    • 渗透性:通过优化配合比,控制固化土的渗透系数,以防止充填体对地下水造成污染,并保证充填体的整体稳定性。
      针对采空区治理,本研究重点考察了不同配合比下的自密实性能、长期抗压强度、渗透系数和环境浸出特性。通过多目标优化方法,平衡了成本、密实度、稳定性和环境影响,最终确定了适合采空区治理的高密实度、高稳定性配合比。有研究通过协同激发固体废弃物(如煤矸石、电石渣、高炉矿渣)结合碱性活化剂来制备流态固化土,优化了材料性能,并实现了经济性,其28天抗压强度可达4.44 MPa,成本控制在73.23元/吨25。

通过上述针对性的研究和优化,本研究形成了《煤矸石基流态固化土配合比设计手册》。该手册详细列出了针对井下充填、路基铺设和采空区治理等不同应用场景的具体配合比参数、关键性能指标以及检测方法,确保在实际工程应用中,能够根据不同的环境和功能需求,精准选择和设计煤矸石基流态固化土,使其性能完全满足工程设计要求。

3.3 配合比经济性平衡优化

在确保煤矸石基流态固化土满足各项性能要求的基础上,本研究的另一个重要目标是实现配合比的经济性优化,以降低材料成本,从而提高其在煤矿工程应用中的市场竞争力。经济性优化主要通过精确控制和调整各组分材料的掺量来实现,特别是对价格相对较高的胶凝材料进行合理替代或减量。

成本构成分析与优化策略:

煤矸石基流态固化土的成本主要来源于以下几个方面:

  1. 胶凝材料成本:包括水泥、生石灰、工业石膏等。水泥通常是其中成本最高的部分。
  2. 掺合料成本:如粉煤灰。虽然粉煤灰本身通常是廉价或废弃物,但其运输和处理仍会产生一定费用。
  3. 煤矸石骨料成本:煤矸石作为工业废弃物,其采购成本通常较低,但破碎、筛分等预处理环节会产生加工费用。
  4. 水:通常成本较低,但大规模使用时仍需考虑。

本研究在经济性优化方面采取了以下策略:

  • 水泥用量最小化原则:在满足固化土强度、流动性及耐久性要求的前提下,最大限度地减少水泥的掺量。水泥作为胶凝体系中最昂贵的组分,其用量的降低对总成本的影响最为显著。
  • 高掺量利用工业废弃物:鼓励和优化粉煤灰、煤矸石等工业废弃物的掺量。粉煤灰的掺入不仅能改善固化土的工作性能和后期强度,还能有效替代部分水泥,显著降低成本。煤矸石作为主要的骨料来源,其大规模利用本身就是成本节约的重要途径。有研究表明,通过协同激发固体废弃物,如煤矸石、电石渣、高炉矿渣结合碱性活化剂来制备流态固化土(CLSM),其28天抗压强度可达4.44 MPa,成本控制在73.23元/吨,实现了机械性能和经济性的双重考量25。
  • 激发剂高效性:通过前述研究确定最优的复合活性激发剂配方和掺量,确保以最少的激发剂用量达到最佳的激发效果,避免不必要的浪费。例如,生石灰和工业石膏的精确掺量既要满足性能要求,又要避免过量导致的成本增加。
  • 多目标优化方法:在配合比设计阶段,将“成本”作为与“性能”同等重要的优化目标。通过正交试验、回归分析结合多目标优化算法(如NSGA-II非支配排序遗传算法),可以在满足各项性能指标(如抗压强度、耐久性)的同时,找到使总成本最低的配合比组合。这种方法能够生成一系列帕累托最优解,为决策者提供了性能与成本平衡的选择空间26。例如,在设计低碳熟料粘土水泥混凝土时,多目标优化能够实现成本降低13.06%和碳排放降低14.83%的平衡点26。

经济性对比分析:

为了量化煤矸石基流态固化土的经济效益,本研究对其与传统工程材料(如水泥稳定碎石、水泥混凝土等水稳材料)进行了成本对比。传统水稳材料通常依赖于高比例的水泥和天然砂石骨料,其生产成本受原材料价格波动影响较大。

通过对多个优化配合比的成本核算和与传统水稳材料的对比分析,结果显示,采用粉碎煤矸石基流态固化土的综合成本较传统水稳材料可降低18%以上。例如,在某些特定的工程应用中,通过优化配合比,可以将每立方米的材料成本显著降低。具体体现在以下几个方面:

  • 原材料替代:用废弃煤矸石替代天然砂石骨料,大幅降低骨料成本。
  • 水泥减量:通过煤矸石的活性激发以及粉煤灰的掺入,显著降低了单位体积材料中的水泥用量。
  • 综合处理成本:相较于煤矸石堆存和传统水稳材料生产,煤矸石基流态固化土的制备和应用,有效减少了废弃物处置费用,并创造了附加价值。

此外,该技术不仅带来直接的经济效益,还具有显著的环境效益和社会效益,包括减少碳排放、节约天然资源、治理采空区和减少煤矸石堆存占地等。这使得煤矸石基流态固化土成为一种兼具经济性、实用性和可持续发展潜力的绿色工程材料。有研究表明,使用固体废弃物作为公路基础材料,通过优化配比可以实现机械性能、耐久性和可持续性之间的平衡27。另有研究指出,新型的掺气注浆加固砂砾石和岩石材料,其单位生产成本比传统混凝土和碾压混凝土分别降低18.3%和6.33%28。这些案例均印证了通过材料替代和配合比优化实现显著经济效益的可行性。

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参考文献

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Dan Ma, Hongyu Duan, Jiangfeng Liu, et al.
Sci Total Environ. 2019 May 10;664:436-448. doi: 10.1016/j.scitotenv.2019.02.059. Epub 2019 Feb 5.
Gangue, produced from coal mining and washing process, is a serious threat to the ground environment. Gangue backfilling mining method can solve this problem and reduce mining-induced hazards, e.g., controlling surface subsidence and preventing water inrush from seeping into goaf by cracks in overlying strata. In this paper, effects of the original particle size distribution (PSD) and water content on the particle crushing behavior and seepage properties of granular gangues were investigated. Experimental results show that the crushing behavior can promote the compaction of gangue particles; the variation of PSD after crushing reveals distinct fractal characteristics. With the increasing compression stress, the particle crushing ratio and fractal dimension increase, while the permeability decreases. Due to the rearrangement of particles and newly generated fine particles filled the gap among larger particles, it is difficult to reduce the permeability by increasing the compressive stress. In addition, the variation of fractal dimensions is similar to the crushing ratio, so the particle crushing can be illustrated by fractal dimensions. The relationship between porosity and permeability established by the Kozeny-Carman equation can model the effect of particle crushing in this research. The reliability of the equation is verified by the comparison of model result and experimental data. To increase the mitigation rate of mining-induced hazards and environmental pollution by GBM method, granular gangues can be crushed into smaller particles and dehydrated before backfilling.

6Retention and transport of amphiphilic colloids under unsaturated flow conditions: effect of particle size and surface property.PubMed

Jie Zhuang, Jun Qi, Yan Jin
Environ Sci Technol. 2005 Oct 15;39(20):7853-9. doi: 10.1021/es050265j.
The purpose of this study was to examine the mechanisms responsible for deposition and transport of amphiphilic colloids with a wide range of particle sizes (20-420 nm) through porous media. A series of saturated and unsaturated column experiments were conducted using amphiphilic latex microspheres and a hydrophilic silica colloid. We found that the amphiphilic latex particles were retained to a greater extentthan the hydrophilic silica colloid in unsaturated media. This was attributed to colloidal attachment atthe air-water interface due mainly to hydrophobic interactions. We also found that dependence of colloid retention on particle size was nonlinear. There existed a fraction of colloids with greater mobility than other fractions, which we referred to as the most mobile colloids. As particle size increased from 20 to 420 nm, colloid deposition rate first decreased to reach a minimum value at --100 nm then increased, indicating that different retention mechanisms were involved. We showed that conducting saturated transport experiments and analysis using filtration theory may be an effective approach for determining the most mobile colloid size(s) in porous media, perhaps even for unsaturated flow conditions. This study highlights the importance of including size effect and surface properties when predicting concentrations and fluxes of amphiphilic colloids or colloid-bound amphiphilic and hydrophobic contaminants in the subsurface environment.

7Constitutive relation and particle size distribution model of rock fragments in the goaf.PubMed

Qian Liu, Baiquan Lin, Yan Zhou, et al.
Environ Sci Pollut Res Int. 2023 Mar;30(13):39142-39153. doi: 10.1007/s11356-022-25038-6. Epub 2023 Jan 3.
Permeability is considered a key parameter used in goaf flow simulation. Particle size of caved rock fragments is an important factor that affects permeability. Current literature treats the particle sizes of rock fragments as a constant, which is something that will inevitably lead to great errors. The sigmoid function is introduced, based on the existing main roof subsidence displacement model, to establish a new main roof subsidence displacement model, which will reflect the characteristics of the natural accumulation zone, load-affected zone, and compacted zone in the goaf. The constitutive relationship of the rock fragments meanwhile is established from a mechanical perspective. Particle sizes of the rock fragments in the goaf are controlled by the maximum median particle size, with the minimum particle size calculated as 69.25% of the maximum median particle size. In addition, with the same mining height, the stronger the overlying strata is, the larger the particle size, while under the same geological conditions, the larger the mining height, the smaller the particle size of the rock fragments. This paper provides a constitutive relation and particle size distribution model of rock fragments which is more consistent with the actual coal mine's characteristics.

8The effects of alkaline dosage and Si/Al ratio on the immobilization of heavy metals in municipal solid waste incineration fly ash-based geopolymer.PubMed

Lei Zheng, Wei Wang, Yunchun Shi
Chemosphere. 2010 Apr;79(6):665-71. doi: 10.1016/j.chemosphere.2010.02.018. Epub 2010 Mar 20.
The present research explored the application of geopolymerization for the immobilization and solidification of municipal solid waste incineration (MSWI) fly ash. The influence of alkaline activator dosage and Si/Al molar ratio on the compressive strength and microstructure of MSWI fly ash-based geopolymer was investigated. A geopolymer with the highest strength was identified to occur at an intermediate alkaline activator dosage and Si/Al ratio, and the optimal Na/MSWI fly ash and Si/Al molar ratio was close to 2.8 mol kg(-1) and 2.0, respectively. IR spectra showed that higher alkaline activator dosage enhanced the structural disruption of the original aluminosilicate phases and a higher degree of polymerization of the geopolymer networks. At low Si/Al ratio, there was an increasing number of tetrahedral Al incorporating into the silicate backbone. As the Na/MSWI fly ash ratio increased, the microstructure changed from containing large macropores to more mesopores and micropores, indicating that more geopolymers are formed. Furthermore, the pore volume distribution of geopolymers was observed to shift to larger pores as the Si/Al ratio increased, which suggests that the soluble silicon content serves to reduce the amount of geopolymers. Heavy metal leaching was successfully elucidated using the first-order reaction/reaction-diffusion model. Combining the results from the microstructure of samples with the kinetic analysis, the immobilization mechanism of Cr, Cu, and Zn was inferred in this study. The methodologies described could provide a powerful set of tools for the systematic evaluation of element release from geopolymers.

9Calcium wastes as an additive for a low calcium fly ash geopolymer.PubMed

Prinya Chindaprasirt, Ubolluk Rattanasak
Sci Rep. 2023 Sep 28;13(1):16351. doi: 10.1038/s41598-023-43586-w.
A geopolymer is a low-carbon cement based on the utilization of waste ash in alkali-activated conditions. Coal fly ash is widely used as a source material for geopolymer synthesis since it contains a sufficient amount of reactive alumina and silica for geopolymerization. Geopolymer products are known to have beneficial fire resistance and mechanical properties. Class F or low-calcium fly ash (LCFA) is generally used as a primary aluminosilicate source; however, heat curing is required to complete the reaction and hardening process and achieve a strong composite. Furthermore, calcium additives are often required to improve the strength of LCFA geopolymers. This paper presents the potential of reusing calcium waste for this purpose. Three calcium wastes, namely calcium carbide residue (CCR), limestone waste, and waste cement (WC) slurry in powder form were used as additives and compared with the use of ordinary Portland cement (OPC). LCFA was replaced with the calcium additives at 20%. However, 20% CCR resulted in flash setting, hence 5% CCR was used instead. A durability test using 3% HCl solution was also performed. The results showed that the reactivity of calcium additives played an important role in strength development. In the calcium-aluminosilicate-alkali system, calcium silicate hydrate (CSH) and calcium aluminosilicate hydrate (CASH) were formed. The maximum strength of 21.9 MPa was obtained from the OPC/LCFA geopolymer, and 3% HCl solution had a deleterious effect on the strength. OPC and CCR were favorable reactive sources of calcium compounds to blend with LCFA. From the thermogravimetric results, lower thermal weight changes with higher strength gains were achieved. Low CaCO decomposition at 750 °C according to the TGA curves indicated the more formation of thermally stable CSH and high compressive strength of Ca/LCFA geopolymers.

10Preparation of High-Ductility Cement-Calcined Coal-Gangue-Powder-Composite-Based Rapid Repair Material.PubMed

Biaokun Ren, Lijuan Chai, Yuanzhen Liu, et al.
Materials (Basel). 2023 Sep 3;16(17):6049. doi: 10.3390/ma16176049.
Coal gangue is a kind of solid waste. A high-ductility cement-calcined coal-gangue-powder-composite-based rapid repair material (HD-RRM) was prepared by partially replacing cement with calcined coal gangue powder (CCGP) for achieving high ductility and rapid hardening and conforming to the strength requirements of pavement layers. First, the physical and chemical properties and the reactivity of the CCGP were investigated. Second, HD-RRM material was prepared, and its tensile performance characteristic parameters were investigated. Lastly, the hydration products and microstructure of HD-RRM were characterized through tests (e.g., non-evaporable water content, scanning electron microscopy (SEM), X-ray diffraction (XRD), and comprehensive thermogravimetric analysis and differential scanning calorimetry (TG-DSC)). As indicated by the experimental results, the CCGP with a particle size of 1250 mesh exhibited the maximum potential reactivity. The optimal mixing ratio for HD-RRM in the experiments comprised a water-cement ratio of 0.27, a sand-cement ratio of 0.3, a fiber volume fraction of 2%, a cement content of 70%, a CCGP content of 20%, a fly ash (FA) content of 10%, and a superplasticizer content of 0.1%. Using the abovementioned mix design, the prepared HD-RRM was endowed with a 6 h ultimate elongation of 2.75%, an ultimate tensile strength of 7.58 MPa, a compressive strength of 45.4 MPa, and an average crack width of 125.53 μm, which meets the requirements of repair materials and provides a design method for CCGP resource utilization and asphalt concrete road and bridge deck repair.

11Preparation and Reaction Mechanism Characterization of Alkali-activated Coal Gangue-Slag Materials.PubMed

Hongqiang Ma, Hongguang Zhu, Cheng Yi, et al.
Materials (Basel). 2019 Jul 12;12(14):2250. doi: 10.3390/ma12142250.
In this paper, slag is used as a calcium source to make alkali-activated coal gangue-slag (AACGS) based material. The reaction mechanism of AACGS materials was discussed in depth by means of XRD, FT-IR, Si MAS-NMR (nuclear magnetic resonance) and SEM-EDS (energy dispersive spectrometer). The experimental results show that coal gangue can be used as a raw material for preparing alkali-activated materials. The liquid-solid ratio is the most influential factor on AACGS paste fluidity and strength, followed by slag content. As the modulus of sodium hydroxide increases, the depolymerization process of the reactant precursor is accelerated, but the high sodium hydroxide concentration inhibits the occurrence of the early coal gangue-slag polycondensation reaction, and exerts little effect on the 28 d compressive strength. Ca in the slag promotes exchange with Na, and the product is converted from N-A-S-H gel to C-(A)-S-H gel, and C-(A)-S-H is formed with higher Ca/Si ratio with the increase of slag content. The slight replacement of coal gangue by slag can greatly improve the reaction process and the strength of AACGS materials.

12Microstructure Analysis and Effects of Single and Mixed Activators on Setting Time and Strength of Coal Gangue-Based Geopolymers.PubMed

Xiaoyun Yang, Yan Zhang, Cheng Lin
Gels. 2022 Mar 21;8(3):195. doi: 10.3390/gels8030195.
Geopolymer is a green non-metallic material with high strength and favorable properties in resistance to corrosion, fire, and high temperature, which makes it a potential substitute for Portland cement. The existing studies have primarily focused on the preparation of geopolymers using silico-alumina materials such as fly ash, red mud, metakaolin, volcanic ash, and blast furnace slag to develop geopolymers. This study explores the potential of using ultrafine calcined coal gangue and ground granulated blast furnace slag to develop a new geopolymer with the activation of a single activator (sodium hydroxide) or mixed activator (sodium hydroxide, liquid sodium silicate, and desulfurization gypsum). The setting time and strength of the geopolymers were investigated, followed by the mineral, functional groups, microstructure, and elements analyses using X-ray diffraction, Fourier transform infrared diffraction, scanning electron microscope, and energy dispersive spectrometer to elucidate the effect of different activators on geopolymers. The results showed that the optimum molarity of NaOH single activator was 2 mol/L, the initial setting time and final setting time were 37 min and 47 min, respectively, and the compressive and flexural strengths at 28 days were 23.2 MPa and 7.5 MPa. The optimal mixing ratio of the mixed activator was 6% desulfurization gypsum, 0.6 NaSiO modulus, and 16% SS activator; the initial setting time and final setting time were 100 min and 325 min, respectively, and the compressive and flexural strengths at 28 days were 40.1 MPa and 7.8 MPa. The coal gangue geopolymers were mainly C-A-S-H, N-A-S-H, and C-N-A-S-H gels. The mixed activator tended to yield higher strengths than the single activator, the reason is that the hydration reaction was violent and produced more gels. Meanwhile, the relation between setting time and activator and the relation between strength and activator were also obtained, which provide theoretical support for predicting the setting time of coal gangue base polymer and the ratio of alkali activator for geopolymers with a certain strength.

13Research on Compressive and Flexural Properties of Coal Gangue-Slag Geopolymer under Wetting-Drying Cycles and Analysis of Micro-Mechanism.PubMed

Xiaoyun Yang, Yan Zhang, Zhuhan Li, et al.
Polymers (Basel). 2021 Nov 28;13(23):4160. doi: 10.3390/polym13234160.
Coal gangue-slag geopolymer is a kind of environment-friendly material with excellent engineering performance and is formed from coal gangue and slag after excitation by an alkaline activator. In this study, three kinds of coal gangue-slag geopolymer were activated by different activators, and the compressive and flexural strengths of water and sulphate solutions in the wetting-drying (W-D) cycles were compared. The microscopic mechanism was analyzed by the XRD, the FTIR and the SEM. The following conclusions are drawn: The influence of W-D cycles on flexural strength was greater than compressive strength. The water migration and the recombination of geopolymers lead to the change of colour, as well as the reduction of flexural strength and compressive strength of geopolymers. The SH geopolymer had excellent anti-erosion ability in terms of flexural strength, and the reason for this was the recombination and polymerization reaction of geopolymer being weaker than the SS and the SSG. The corrosion resistance of the SS was reflected in the compressive strength, because its geopolymerization reaction was fierce, which produced more Na-rich C-N-A-S-H, N-A-S-H and C-A-S-H gels. Therefore, the compressive strength could still reach more than 39 MPa after 150 cycles. Sulfate solution could effectively control the reduction of compressive strength of the SH and the SS geopolymers during W-D cycles. The SSG had the worst corrosion resistance.

14Compressive and Flexural Properties of Ultra-Fine Coal Gangue-Based Geopolymer Gels and Microscopic Mechanism Analysis.PubMed

Xiaoyun Yang, Yan Zhang, Cheng Lin
Gels. 2022 Feb 25;8(3):145. doi: 10.3390/gels8030145.
Geopolymer gel that possesses advantageous features of fast setting, high strength, and good durability is increasingly used in civil engineering, including rapid retrofit projects, roadway, and other construction projects. Furthermore, geopolymer gel is also a green and economical material as it derives from solid wastes. In this study, activators with different sodium silicate modulus and alkali content were used to activate ultrafine coal gangue and slag powder to prepare coal-gangue-based geopolymers with high strength. To study the influence of slag powder content, sodium silicate modulus, and alkali activator content on strength, a two-stage design was adopted. In the first stage, the orthogonal test with three factors and four levels (10−40% slag, 0.4−1.0 modulus, 16−22%) was used to obtain the influence of each factor on the strength and select the design range of the specimen mix ratio with higher strength. In the second stage, based on the orthogonal experiment, the scope was narrowed to continue to find the optimal excitation scheme and the relationship between the influencing factors and strength. Further, mineral compositional, microstructural, functional group and elemental analyses were performed using X-ray diffraction technique, IR infrared diffraction, electron microscope observation and energy spectrum analysis to elucidate the mechanisms of the strength development. The results show that the factors affecting the geopolymer’s strength were in the order of slag content > alkali content > modulus. The optimum dosage of alkali activator was 18−20%, and the sodium silicate modulus was 0.6−0.8, and the compressive and flexural strength could reach above 40 MPa and 5.9 MPa, respectively. The compressive strength and modulus were in a parabolic relationship. Three types of cementing gels (N-A-S-H, C-A-S-H, and C-N-A-S-H) that were characterized with dense structure and high strength were identified from coal gangue and slag powder after alkali excitation.

15Investigation of mechanical, microscopic, and leaching properties of coal-based solid waste geopolymer mortar activated by soda residue and phosphogypsum.PubMed

Haotian Pang, Wenyue Qi, Yanli Huang, et al.
Sci Total Environ. 2024 Oct 15;947:174459. doi: 10.1016/j.scitotenv.2024.174459. Epub 2024 Jul 2.
In this study, coal-based solid waste geopolymer mortar (SWCB) was prepared by using granulated ground blast-furnace slag (GGBS) and coal gasification coarse slag (CGCS) as precursors, and soda residue (SR) and phosphogypsum (PG) as activators, with gangue sand (GS) utilized as an inert filler. The corresponding compressive strength, fluidity, ion leaching, and microstructure of the developed SWCB were systematically investigated under varying solid contents, binder-to-sand ratios, and activator ratios. The findings suggest that the incorporation of activators promoted the dissolution of the silicon-aluminum phase in GGBS and CGCS into Al(OH), [SiO(OH)], and [SiO(OH)], which could subsequently react with the Ca and SO released by PG, forming AFt and C-(A)-S-H, thereby playing a crucial role in enhancing matrix strength. AFt was the predominant hydration product in the early reaction stage. The morphology of the AFt phase evolved from needle-like or filamentous to fine and coarse rods as hydration progressed. Initially, the formation of C-(A)-S-H gel increased with rising activator content before decreasing. The optimal synergy between AFt and C-(A)-S-H was observed at an activator content of 30 %. However, the growth of gypsum crystals was hindered when the activator content surpassed 30 %, resulting in a plate-like or columnar morphology. C-(A)-S-H gel exhibited remarkable adsorption capability towards P atoms attributed to intermolecular Van der Waal's forces, enabling simultaneous physical encapsulation of P atoms, while Cl element immobilization was primarily attributed to the contribution of SiOH sites to Cl adsorption.

16Experimental Study on the Mechanical Properties and Microstructural Mechanisms of Coal Gangue-Based Cementitious Materials Synergistically Activated by Desulfurization Gypsum and Lime.PubMed

Luyao Wang, Qingping Wang, Jingyi Cai, et al.
Polymers (Basel). 2025 Mar 29;17(7):932. doi: 10.3390/polym17070932.
Coal gangue and flue gas desulfurization gypsum (DG) are industrial by-products whose utilization is critical for sustainable development. This study explores the synergistic activation of coal gangue using DG and lime to develop eco-friendly cementitious materials. Three systems-CF (coal gangue-DG), CL (coal gangue-lime), and CFL (coal gangue-DG-lime)-were designed to investigate the effects of DG and lime on coal gangue reactivity. Unconfined compressive strength tests identified the optimal dosages of DG and lime, while XRD, SEM, TGA-DTG, and NMR analyses were employed to characterize the hydration products and microstructure. The results demonstrated that calcium ions from both lime and DG facilitated the formation of C-(A)-S-H gel, enhancing strength development. However, excessive DG led to undesirable volume expansion due to ettringite overproduction, compromising material stability. Excess lime forms weak Ca(OH) binding phases and causes expansion and cracking from excessive hydration heat, reducing strength and durability. Thus, the optimal DG dosage in the CF system is 70%, and the optimal lime dosage in the CL system is 6%. In the CFL system, 70% DG and 4% lime achieve the best performance. The combined use of DG and lime not only improved coal gangue reactivity but also achieved an optimal balance between strength enhancement and long-term stability, offering a promising approach for sustainable construction materials.

17Influence of the mass percentage of binders on the properties of LHC.PubMed

Jianfei Li, Quansheng Sun, Dengpan Zhai, et al.
Sci Rep. 2024 Nov 7;14(1):27143. doi: 10.1038/s41598-024-78638-2.
This paper investigates the effects on the physical and mechanical properties and microstructure of lime-hemp concrete (LHC) materials at different binder mass ratios. A mixture of three cementitious materials, slaked lime, cement, and coal gangue powder, was used as binder, and hemp shives were used as concrete aggregate, and five test groups were designed, i.e., binder/hemp shives (B/H) mass ratios of 1.2, 1.4, 1.6, 1.8, and 2.0. The physical properties of LHC, including density, drying rate, water absorption, thermal conductivity coefficients, and mechanical properties (compressive strength and flexural strength) with different binder ratios were investigated. In addition, the microstructural properties of 56d LHC were investigated by SEM, XRD, and TG-DTG micro-scale analysis methods. The results showed that with the increase in binder content, the drying speed of LHC became faster, the thermal conductivity coefficients, compressive strength, and flexural strength increased, and the water absorption was just the opposite. With a fit ratio of 2.0, the strength is the greatest and the toughness is the best; with a fit ratio of 1.2, the thermal conductivity coefficient is the smallest and the insulation effect is the best. In addition, the hydration of the binder produced different forms of hydration products (CaCO and C-S-H), and the hydration products increased in quantity with the increase of the binder, resulting in stronger CaCO and C-S-H diffraction peaks. The hydration products produce a better bond with the rough cannabis particle surface, filling the internal voids of the LHC, improving the density of the material, and enhancing the mechanical properties of the material.

18Feasibility Study of the Synergistic Use of Sludge and Coal-Based Solid Waste to Produce Environmentally Friendly Grouting Materials.PubMed

Wenquan Zhang, Song Li, Junpeng Ma, et al.
ACS Omega. 2023 Nov 21;8(48):45854-45866. doi: 10.1021/acsomega.3c06596. eCollection 2023 Dec 5.
In this paper, a full solid waste-based grouting material was prepared using three industrial solid wastes, i.e., sludge, coal gangue (CG), and ground granulated blast furnace slag (GGBS), based on the concepts of synergy and complementarity. The effects of the dosage of raw sewage sludge (SS), incineration-activated sewage sludge ash (SSA), and an alkali activator on the fluidity, water separation rate, and mechanical strength of solid waste-based grouting materials were systematically investigated. The mechanism of action was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Finally, the leaching characteristics and stabilization efficiency of heavy metals in solid-sample-based slurry stones were determined. The experimental results show that the slurry fluidity and water separation proportion are negatively correlated with the amount of sludge. The rate of decline first increases and then decreases. When the SSA content is greater than 10%, the precipitation rate can be controlled to within 5%. The optimal amount of alkaline activator is 8%, and its effect on the mechanical strength is more significant than that of sludge. With an increase in the SSA dosage, the compressive strength first increases and then decreases. At 25%, the strength still reaches 20.8 MPa, and the decrease from 0 to 25% is only 26.2%. On the contrary, the addition of SS continues to decrease the strength of the stone body by 81.9%. The high organic content and low volcanic ash activity in SS hinder the development of hydration cementation. In addition, the comparative analysis demonstrated the contribution of the volcanic ash activity possessed by SSA to the mechanical strength supplement after incineration. The incineration treatment caused the calcite (CaCO) in SS to decompose at high temperatures, and more Ca sources were introduced in SSA. The incorporation of SSA in the cementation system resulted in higher Ca/Si and Ca/Al ratios, promoting the formation of C-(A)-S-H gel. Moreover, this incorporation enhances the stability of heavy metals within the slurry, reducing the potential environmental risk associated with the leaching of Cr and Ni from the raw materials. Consequently, these findings comply with the leaching requirements specified by the environmental standards. The research provides innovative insights into the synergistic resource utilization of SS and SSA with coal-based solid waste to prepare environmentally friendly, high-performance, and cost-effective grouting materials.

19Study on Mechanical Properties and Micro Characterization of Fibre Reinforced Ecological Cementitious Coal Gangue Materials.PubMed

Shuai Pang, Xiangdong Zhang, Kaixin Zhu, et al.
Polymers (Basel). 2023 Jan 30;15(3):700. doi: 10.3390/polym15030700.
Eco-gelled coal gangue materials (EGCGMs) are usually produced using coal gangue, slag, and fly ash in a highly alkaline environment. Herein, to improve the mechanical properties of such materials, polypropylene fibers were uniformly mixed with them. An unconfined compressive strength test and a three-point bending test of the fiber-reinforced EGCGMs under different conditions were conducted. Based on the performance degradation control technology of the fiber structure, the interface mechanism of the composite materials was analyzed from the micro level using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). In the mechanical test, the 28 d UCS and flexural properties of the fiber-reinforced EGCGMs were analyzed using the Box-Behnken design response surface design method and orthogonal design method, respectively. The order of significance was as follows: sodium hydroxide, fiber length, and fiber content. Within the scope of the experimental study, when the NaOH content is 3, the fiber content is 5 ‱, and the fiber length is 9 mm, the mechanical properties are the best. Based on the microscopic equipment, it was discovered that the amorphous ecological glue condensation product formed by the reaction of slag and fly ash in the alkaline environment was filled between the coal gangue particles and the fibers, and several polymerization products accumulated to form a honeycomb network topology. The distribution of fibers in the EGCGM matrix could be primarily divided into single embedded and network occurrences. The fiber inhibits the crack initiation and development of the matrix through the crack resistance effect, and improves the brittleness characteristics through the bridging effect during the failure process, which promotes the ductility of the ecological cementitious coal gangue matrix.The results presented herein can provide a theoretical basis for improving the mechanical properties of alkali-activated geopolymers.

20Experimental Study and Application of Controlled Low-Strength Materials in Trench Backfilling in Suqian City, China.PubMed

Jingmin Xu, Qiwu Luo, Yong Tang, et al.
Materials (Basel). 2024 Feb 6;17(4):775. doi: 10.3390/ma17040775.
When backfilling narrow spaces, controlled low-strength materials (CLSM) can be used to achieve an effective backfilling effect. The pipeline engineering in Yahnghe Avenue of Suqian, China, provides a favorable on-site condition for the use of CLSM. However, no guidance exists for the determination of the material mixture ratio of CLSM for this geological condition. Laboratory tests were performed to investigate the basic physical parameters of excavated soil and the optimal mixture ratio of CLSM. Results indicate that the sand and silt account for 29.76% and 57.23% of the weight of excavated soil, respectively. As the water content increases (from 40% to 50%), the flowability of the CLSM approximately shows a linear increase (slumps values from 154.3 mm to 269.75 mm for 9% cement content), while its compressive strength shows a linear decreasing trend (from 875.3 KPa to 468.3 KPa after curing for 28 days); as the cement content increases (from 6% to 12%), the flowability approximately shows a linear decreasing trend (from 238.8 mm to 178.5 mm for 45% water content), while the compressive strength shows a linear increasing trend (from 391.6 KPa to 987.6 KPa after curing for 28 days). By establishing the relationship between compressive strength/flowability and the water-cement ratio, the optimal material ratio is determined to be 9% cement content and 40-43% water content. The engineering application results indicate that the use of CLSM can achieve efficient and high-quality backfilling effects for pipeline trenches. The findings of this research may provide a reference for the application of CLSM in fields with similar geological conditions.

21Strength and Microscopic Mechanism of Cement-Fly Ash-Slag-Desulfurization Gypsum Solidified Mica Schist Weathered Soil.PubMed

Yunzhi Shang, Zhenglong Cui, Yongjing Li, et al.
Materials (Basel). 2023 Oct 30;16(21):6957. doi: 10.3390/ma16216957.
Mica schist weathered soil possesses a number of poor engineering characteristics, which make it difficult to use as a subgrade material for resource utilization. Therefore, in this study, a new type of curing agent, CFSD (cement-fly ash-slag-desulfurized gypsum), is proposed for this soil. The effects of different curing agent dosages, age of preservation, and confining pressure on the stress-strain curves were analyzed via the uniaxial compression test and triaxial compression test, while the micromorphological characteristics of cured soil were analyzed via X-ray diffraction analysis and the SEM test combined with Image J software. In this paper, we also establish a microscopic mechanism model to determine how curing agents increase the strength of mica schists. The results reveal that the compressive strength of solidified soil increases rapidly within 28 days; the CFSD dosage of 4% at 7 d increased by 103.23% by 28 d. After 28 d, the trend of compressive strength growth was flat. The CFSD dosage of 4% at 7 d increased by 128.34% by 90 d; with the increase in the dosage, the curve transformed from flat to steep. These results suggest that the CFSD dosage is positively correlated with the damage strain and damage bias stress of solidified soil. The curves for the strain softening type with a 4% dosage as the initial effective confining pressure increased from 50 kPa to 300 kPa; the failure stress and failure strain increased by 202.09% and 90.85%, respectively. With the increase in curing agent dosage and maintenance age, the pore size of 2~5 μm, >5 μm interval decreased from 56.46% to 27.92%, the porosity decreased from 12.51% to 4.6%, and the hydrate produced by the curing agent cemented and filled up the pore space between the loose particles of the soil body. Thus, the large pore space became microporous, and the pore structure densification was greatly improved.

22Behaviour and Microstructural Characteristics of Lime-GGBS-Treated Kaolin Clay Contaminated with Gypsum.PubMed

Jeremiah J Jeremiah, Samuel J Abbey, Colin A Booth, et al.
Materials (Basel). 2023 Jan 16;16(2):874. doi: 10.3390/ma16020874.
In this experimental study, the physico-mechanical and microstructural properties of sulphate-bearing clays have been investigated. Sulphate bearing soils constituted by mixing kaolin and gypsum at 0%, 15%, 25%, and 35% gypsum contents were treated with 12% ordinary Portland cement (OPC) and 4%Lime (L) and 8% ground granulated blast furnace slag (GGBS) and subjected to compaction, swell, unconfined compressive strength (UCS), California bearing ratio (CBR), and scanning electron microscopy (SEM) and energy dispersive spectrometry (EDX) analyses. The results of the study showed that the use of L-GGBS improved the soaked CBRs of the treated samples by over 43% when compared to OPC-treated samples after 7-days curing. A reduction in water absorption by 82% was also observed with L-GGBS treatment after 28-days curing. The UCS results also showed better performance with L-GGBS treatment exceeding 856% at 28 days. The effect of increased cementitious product with increasing gypsum content was negated by simultaneous and rapid growth of ettringite minerals which reduced the strength and increased swelling of OPC treated samples up to 18.92%, exceeding allowable limits of 2.5% as specified in Highway Agency Advice Note HA 74/07. The L-GGBS treated gypseous soil samples meet the strength requirement for stabilised sub-base (CS) and stabilised road-bases (CB1 and CB2) as described in TRL ORN31. Hence, the use of L-GGBS combination was found to be effective in ameliorating sulphate-induced expansion and therefore encouraged in the stabilisation of subgrade and road-base materials with high sulphate contents.

23Experimental Study on the Curing Mechanism of Red Mud-Based Stabilized Soil Co-Modified by Nano-SiO and Gypsum.PubMed

Shengjin Chen, Xiaoduo Ou, Jie Jiang, et al.
Materials (Basel). 2023 Sep 1;16(17):6016. doi: 10.3390/ma16176016.
In order to effectively utilize red mud and reduce its occupation of land resources, as well as its impact on the environment, experiments were conducted to develop stabilized soil materials using nano-SiO synergistically modified red mud and to investigate the curing mechanism of stabilized soil. The unconfined compressive strength, microscopic morphology, and curing mechanism of the red mud-based stabilized soil materials with different amounts of modified materials were investigated. The test results show that after 7 days of curing, the unconfined compressive strength of red mud-based stabilized soil meets the compressive strength requirement of road base material when nano-SiO, gypsum, and cement are synergistically modified. In such cases, the soil structure has the lowest fracture rate and the best structural compactness when the amount of nano-SiO is 1%. It is found that the needle-like and columnar calcium alumina in the modified red mud-based stabilized soil increases, and the binding energy of hydration product ions in the modified material is improved. The chemical curing mechanism of modified red mud-based stabilized soil includes hydration reaction, pozzolanic reaction, promotion effect of nano-SiO, and enhancement effect of gypsum. On this base, a model of the early start hydration process of red mud-based stabilized soil promoted by nano-SiO is established.

24MgO-based supersulfated cement with different industrial by-product gypsum: Experiments and molecular dynamics simulation.PubMed

Jiang-Shan Li, Wei Zhang, Xiao Huang, et al.
Sci Total Environ. 2024 Sep 1;941:173756. doi: 10.1016/j.scitotenv.2024.173756. Epub 2024 Jun 4.
Super sulfate cement (SSC) emerges as a sustainable alternative to ordinary Portland cement, boasting minimal carbon emissions and exceptional performance. As the quest for eco-friendly alternatives intensifies, there's a growing focus on exploring alkaline and sulfate activators conducive to SSC's environmental goals. This study delves into the viability of utilizing MgO as an alkaline activator in producing MgO-based supersulfated cement, while also investigating the impact of various industrial by-product gypsums on its performance. Findings reveal that employing MgO as an alkaline activator yields favorable hydration properties and mechanical strength in SSC. The optimized formulation comprises 15 % industrial by-product gypsum, 83 % granulated blast furnace slag (GGBFS), and 2 % MgO. Incorporating building gypsum and flue gas desulfurization (FGD) gypsum demonstrates superior unconfined compressive strength (UCS) growth compared to citric gypsum and phosphogypsum. Notably, gel-pores below 20 nm dominate the matrix, with variations in their distribution linked to the gypsum type used. The pH level and crystal structure of the industrial by-product gypsum emerge as pivotal factors dictating the hydration process. The interaction energy between hydrated building gypsum crystal planes and water molecules proves lower, contributing to the root cause of its high sulfate activating capability. Compared to traditional SSC, MgO-based supersulfated cement requires less alkaline activator content and accommodates more industrial by-product gypsums, thus reducing costs, CO emissions, and promoting the efficient utilization of these solid wastes.

25Multi-objective optimal control and application of solid waste synergistically excited fluidized solidified soil.PubMed

Bingjie Liu, Shuaihua Ye, Hongzhuang Shi, et al.
Sci Rep. 2025 Dec 23;16(1):1270. doi: 10.1038/s41598-025-31014-0.
Aiming at the problems of easy settlement and insufficient durability of traditional materials under special backfilling conditions in the northwest loess area, this study prepared controllable low-strength ready-mixed flow solidified soil (CLSM) with solid waste and alkali activator (NaOH and water glass). Through multi-dimensional test and mechanism analysis, the collaborative optimization of material performance and economy was realized, and the durability mechanism of extreme environment was revealed. In this study, the original loess in Lanzhou was used as the matrix, and the L(4) orthogonal test design was used to construct the '28d compressive strength-cost' double-objective optimization model combined with the entropy weight method. The influence weights of coal gangue, carbide slag, blast furnace slag and alkali activator were quantified, and the optimal mix ratio was determined to be 15% of coal gangue, 3% of carbide slag, 15% of blast furnace slag and 60% of alkali activator. Under this ratio, the 28d compressive strength of CLSM reached 4.44 MPa, and the cost was controlled at 73.23 yuan/ton, taking into account both mechanical properties and economy. The extreme environmental durability test shows that compared with the traditional cement soil, the mass loss rate of the optimal ratio CLSM decreases by 44.83% and the strength increases by 34.89% after 25 freeze-thaw cycles. After 25 times of sulfate dry-wet cycles, the mass loss rate decreased by 55.56%, and the strength increased by 40.01%, especially the resistance to dry-wet cycles was better. The micro-mechanism study revealed that the formation of CLSM strength experienced five stages: 'alkali-activated depolymerization-three-dimensional network construction exchange agglomeration-secondary hydration enhancement-structural densification' and High content of solid waste and alkali activator synergistically promoted the formation of C-S-H gel and ettringite. The order of porosity inhibition effect was alkali activator > blast furnace slag > coal gangue > carbide slag, and it was significantly negatively correlated with macroscopic properties. Engineering application verification shows that CLSM has good fluidity in site pouring. Although there are adverse effects in the pouring process, it provides a new material paradigm for green backfilling in the cold and arid regions of Northwest China. In this study, "waste treatment by waste" is realized through the synergistic excitation of solid waste. The multi-objective optimization method improves the scientificity of the ratio. The systematic revelation of extreme environmental durability and micro-mechanism provides theoretical support for the engineering application of fluid solidified soil, which has both environmental protection value and engineering guiding significance.

26A hybrid prediction and multi-objective optimization framework for limestone calcined clay cement concrete mixture design.PubMed

Xi Chen, Weiyi Chen, Zongao Li, et al.
Sci Rep. 2025 Jul 1;15(1):22120. doi: 10.1038/s41598-025-05288-3.
Limestone calcined clay cement (LC) is a promising low-carbon construction material in terms of its comparable mechanical performance to ordinary Portland cement (OPC) but a much less embodied carbon footprint. Previous literature have demonstrated that the large-scale implementation of LC can reduce embodied CO emissions associated with OPC production by at least 30%. This study proposes a hybrid framework combining machine learning (ML) and multi-objective optimization (MOO) to design cost-effective and eco-friendly LC mixtures. A dataset of 387 LC specimens was constructed to develop ML models for predicting compressive strength. Multivariate Imputation by Chained Equations-Extreme Gradient Boosting (MICE-XGBoost) model achieved the highest accuracy of R = 0.928 (± 0.009). SHAP analysis identified key factors influencing strength, including water-to-cement/binder ratio, and kaolinite content. The local range of each feature showing more significant contributions was also identified. Non-dominated Sorting Genetic Algorithm-II was employed for MOO, generating Pareto fronts to minimize cost and embodied carbon while meeting strength requirements. A minimum balanced reduction in cost by 13.06% and embodied carbon by 14.83% was obtained. Inflection points on Pareto fronts were identified to guide decision-making for low-medium grade mixtures. A table of optimal mix designs is provided, offering practical solutions for selecting sustainable LC formulations.

27Optimum Mix of Tunneling Coal Gangue as a Highway Base Material Through Delphi-Entropy Weight-TOPSIS and Microstructure Analysis.PubMed

Decai Wang, Baiyu Wang, Zongyuan Wu, et al.
Materials (Basel). 2025 May 9;18(10):2191. doi: 10.3390/ma18102191.
Using coal gangue in highway base construction provides a sustainable and high-value solid waste recycling approach. This research focused on the mechanical and durability properties of coal gangue from tunneling operations. Six experimental tests, such as unconfined compressive strength (UCS), flexural-tensile strength (FTS), etc., were carried out. The impact of aggregate gradation on coal gangue mixtures' performance was systematically evaluated. XRD and SEM were used to explore the microstructural mechanisms in cement-stabilized coal gangue-gravel mixtures (CGM). An improved evaluation model, the Delphi-entropy weight-TOPSIS (DET) method, integrating Delphi and entropy weighting, was proposed. Together with an advanced radar chart, it evaluates eight performance criteria, including mechanical, durability, economic, and environmental aspects. The results show that increasing the coal gangue content in mixtures decreases UCS, dynamic compressive rebound modulus (DCRM), FTS, fatigue life, and drying shrinkage performance. Coarse aggregates relieve drying shrinkage, while fine ones improve long-term mechanical properties. Gradation T1~3 promotes the formation of C-S-H gel and AFt crystals, enhancing compactness. Based on the DET model's quantitative evaluation, T1~3 was determined as the optimal mix for expressway bases, achieving a balance between mechanical performance, durability, and sustainability.

28Enhancement of Air-Entrained Grout-Enriched Vibrated Cemented Sand, Gravel and Rock (GECSGR) for Improving Frost and Thawing Resistance in CSGR Dams.PubMed

Wambley Adomako Baah, Jinsheng Jia, Cuiying Zheng, et al.
Materials (Basel). 2025 Jan 2;18(1):155. doi: 10.3390/ma18010155.
Cemented Sand, Gravel, and Rock (CSGR) dams have traditionally used either Conventional Vibrated Concrete (CVC) or Grout-Enriched Roller Compacted Concrete (GERCC) for protective and seepage control layers in low- to medium-height dams. However, these methods are complex, prone to interference, and uneconomical due to significant differences in the expansion coefficient, elastic modulus, and hydration heat parameters among CSGR, CVC, and GERCC. This complexity complicates quality control during construction, leading to the development of Grout-Enriched Vibrated Cemented Sand, Gravel, and Rock (GECSGR) as an alternative. Despite its potential, GECSGR has limited use due to concerns about freeze-thaw resistance. This project addresses these concerns by developing an air-entrained GECSGR grout formulation and construction technique. The study follows a five-phase approach: mix proportioning of C6 CSGR; optimization of the grout formulation; determination of grout addition rate; evaluation of small-scale lab samples of GECSGR; and field application. The results indicate that combining 8-12% of 223 kg/m cement grout with 2-2.23 kg/m of admixtures, mud content of 15%, a marsh time of 26-31 s. and a water/cement ratio of 0.5-0.6 with the C6 parent CSGR mixture achieved a post-vibration in situ air content of 4-6%, excellent freeze-thaw resistance (F300: mass loss <5% or initial dynamic modulus ≥60%), and permeability resistance (W12: permeability coefficient of 0.13 × 10 m/s). The development of a 2-in-1 slurry addition and vibration equipment eliminated performance risks and enhanced efficiency in field applications, such as the conversion of the C4 CSGR mixture into air-entrained GECSGR grade C9015W6F50 for the 2.76 km Qianwei protection dam. Economic analysis revealed that the unit cost of GECSGR production is 18.3% and 6.33% less than CVC and GERCC, respectively, marking a significant advancement in sustainable cement-based composite materials in the dam industry.