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Characterization and Evaluation of Ground Glass Fiber as a Cementitious Component in Portland Cement and Geopolymer Concrete Mixtures

机译：硅酸盐玻璃纤维作为硅酸盐水泥和地质聚合物混凝土混合物中胶凝成分的表征和评估

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摘要

A large amount of glass fiber is commercially produced for use in various applications. However, this process generates millions of tons of waste glass fiber annually around the world. This material has an amorphous structure that is rich in silica, alumina and calcium oxides, and if milled into a fine powder, it could potentially be used a supplementary cementitious material (SCM) in portland cement mixtures; or as a source material for production of geopolymer. So, the first objective of this research work, is to evaluate the utilization of ground glass fiber (GGF) as a SCM in portland cement mixtures, and the second objective is to study the mechanical and durability properties of GGF-based geopolymers.;To fulfill the first objective, concrete and mortar mixtures containing different dosage of GGF (i.e. 10, 20 and 30% by mass) were prepared. Fresh and hardened properties of these mixtures were tested and compared with two control mixtures, including: (i) a mixture made from 100% portland cement, and (ii) a mixture having 75% portland cement and 25% class F fly ash (by mass). It was observed that utilization of GGF up to 30% (as a cement replacement) did not influence the mechanical properties of the concrete and mortar mixtures significantly compared to control mixtures; however, the use of GGF as SCM resulted in a remarkable improvement in the durability of the mixtures. It was also seen that the utilization of GGF at the 30% replacement level, successfully mitigated the ASR-related expansion of mortar and concrete mixtures containing the crushed glass aggregate.;For the second objective, the possibility of producing geopolymer from GGF was investigated. To activate GGF, different dosage and combinations of sodium hydroxide solution (NaOH) and sodium silicate solution were used, and specimens were cured at 60°C for 24 h. Fresh and hardened properties of geopolymer mixtures made from GGF as the precursor, were studied and compared to glass-powder (GLP) and fly ash-based geopolymer mixtures. The effect of change in the Na2O-to-binder ratio (alkali content of the activator solution) and the SiO2/Na2O (silica content of the solution) ratio on the workability of and compressive strength of the mortar mixtures was monitored and compared to the GLP and fly ash-based geopolymers. It was seen that the strength gain in GGF-based geopolymers does not depend on the presence of sodium silicate in the activator solution; and a high compressive strength (as high as 80 MPa) can be achieved in three days, only by using sodium hydroxide solution alone.;Furthermore, to better understand parameters affecting the activation of GGF-based geopolymers, effect of temperature (from ambient to 110°C) and duration of heat-curing on the compressive strength and micro-structure of GGF-based geopolymers was studied. The temperature of heat curing was seen to affect the early-age (i.e. 3 to 7 days) compressive strength of the GGF-based samples but had no significant effect on the later-age (i.e. 28 to 56 days) strength. Finally, it was concluded that GGF has a good potential to be used as a precursor to produce high strength geopolymers even at ambient temperature (23°C).;Based on the results obtained from the compressive strength experiments, mixtures with the highest compressive strength were selected from each precursor to be used for the durability experiments. Durability aspects of GGF-based geopolymer such as resistance against sodium sulfate solution and magnesium sulfate solution, alkali silica reaction, drying shrinkage and corrosion of steel rebar were investigated and were compared to fly ash and GLP-based geopolymer, and an ordinary portland cement mixture (OPC). Based on this investigation it was found that GGF and fly ash-based geopolymers showed superior performance against ASR-related deterioration in comparison to GLP-based geopolymer and the OPC mixture. It was also observed that despite the fluctuation in properties at early ages, immersion in the sodium sulfate (Na2SO4) solution and magnesium sulfate (MgSO4) solution did not lead to a significant mass or strength loss of GGF-based geopolymer at the later ages.;In conclusion, it can be stated that a high compressive strength GGF-based geopolymers could be produced by using an activator solution that is comprised of only NaOH. Durability experiments conducted on GGF-based geopolymer mixtures showed good performance in resisting ASR and sulfate solution exposure. Based on preliminary results it was observed that drying shrinkage of GGF and fly ash-based geopolymer was similar to the OPC mixture while the drying shrinkage of GLP-based geopolymer was significantly higher. Findings from basic experiments conducted in this study showed that factors such as: (i) the low amount of CH in the structure, (ii) low porosity, and (iii) the durable structure of the geopolymer gel in the GGF-based geopolymers, which remains stable under the aggressive conditions such as, exposure to sulfate solutions, are responsible for the superior durability performance of GGF-based geopolymer.
机译：商业生产大量的玻璃纤维用于各种应用。但是，此过程每年在世界范围内都会产生数百万吨的废玻璃纤维。这种材料具有无定形结构，富含二氧化硅，氧化铝和氧化钙，如果将其研磨成细粉，则有可能在硅酸盐水泥混合物中用作辅助胶结材料（SCM）；或作为生产地质聚合物的原料。因此，这项研究工作的第一个目标是评估磨碎玻璃纤维（GGF）作为硅酸盐水泥混合物中的SCM的用途，第二个目标是研究GGF基地质聚合物的机械性能和耐久性能。为了达到第一个目的，制备了含有不同剂量GGF（即10、20和30质量％）的混凝土和砂浆混合物。测试了这些混合物的新鲜和硬化性能，并与两种对照混合物进行了比较，包括：（i）由100％硅酸盐水泥制成的混合物，和（ii）具有75％硅酸盐水泥和25％F类粉煤灰的混合物（按质量）。观察到，与对照混合物相比，使用高达30％的GGF（作为水泥替代品）不会显着影响混凝土和砂浆混合物的机械性能。但是，将GGF用作SCM可以显着提高混合物的耐久性。还可以看出，以30％的替代水平使用GGF，成功地减轻了含有碎玻璃骨料的砂浆和混凝土混合物与ASR相关的膨胀。第二个目标是研究由GGF生产地聚合物的可能性。为了激活GGF，使用了不同剂量的氢氧化钠溶液（NaOH）和硅酸钠溶液并混合使用，然后在60°C下将样品固化24小时。研究了以GGF为前体的地聚合物混合物的新鲜和硬化性能，并将其与玻璃粉（GLP）和粉煤灰基地聚合物混合物进行了比较。监测Na2O与粘结剂的比率（活化剂溶液的碱含量）和SiO2 / Na2O（溶液的二氧化硅含量）比率变化对砂浆混合物的可加工性和抗压强度的影响，并将其与GLP和粉煤灰基地质聚合物。可以看出，基于GGF的地质聚合物的强度增加并不取决于活化剂溶液中硅酸钠的存在。仅通过使用氢氧化钠溶液就可以在三天内获得高抗压强度（高达80 MPa）。此外，为了更好地了解影响基于GGF的地质聚合物活化的参数，温度的影响（从环境温度到室温）。研究了110°C）和热固化时间对GGF基地质聚合物的抗压强度和微观结构的影响。可以看出热固化温度会影响基于GGF的样品的早期（即3至7天）抗压强度，但对后期（即28至56天）强度无明显影响。最后得出的结论是，即使在环境温度（23°C）下，GGF也有可能用作生产高强度地质聚合物的前体。;基于抗压强度实验的结果，具有最高抗压强度的混合物从每种前体中选择一种用于耐久性实验。研究了基于GGF的地质聚合物的耐久性，例如耐硫酸钠溶液和硫酸镁溶液，碱二氧化硅反应，干燥收缩和钢筋的腐蚀，并与粉煤灰和GLP地质聚合物以及普通硅酸盐水泥混合物进行了比较（OPC）。基于该调查，发现与基于GLP的地质聚合物和OPC混合物相比，基于GGF和粉煤灰的地质聚合物表现出优异的抗ASR相关劣化的性能。还观察到，尽管在早期老化时性能发生了变化，但将其浸入硫酸钠（Na2SO4）溶液和硫酸镁（MgSO4）溶液中并不会导致后来老化的基于GGF的地质聚合物的质量或强度损失。综上所述，可以说，通过使用仅包含NaOH的活化剂溶液，可以生产出高抗压强度的GGF基地质聚合物。对基于GGF的地质聚合物混合物进行的耐久性试验显示出良好的抗ASR和硫酸盐溶液暴露性能。根据初步结果，可以观察到GGF和粉煤灰基地质聚合物的干燥收缩率与OPC混合物相似，而GLP基地质聚合物的干燥收缩率则明显更高。这项研究进行的基础实验发现，这些因素包括：（i）结构中CH含量低，（ii）低孔隙率和（iii）GGF基地质聚合物中地质聚合物凝胶的持久结构，在诸如以下的恶劣条件下保持稳定暴露于硫酸盐溶液中，是基于GGF的地质聚合物优异的耐久性能的原因。

著录项

  • 作者

    Dezfouli, Hassan Rashidian.;

  • 作者单位

    Clemson University.;

  • 授予单位 Clemson University.;
  • 学科 Civil engineering.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 361 p.
  • 总页数 361
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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