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

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 60oC 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 110oC) 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 (23oC). 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

Comparación de Características de Resistencia y Durabilidad de un Geopolímero obtenido a partir de ceniza Volante, Fibra de Vidrio Esmerilado y Polvo de Vidrio

Strength and durability characteristics of geopolymers produced using three precursors, consisting of fly ash, Ground Glass Fiber (GGF), and glass-powder were studied. Combinations of sodium hydroxide and sodium silicate were used as the activator solutions, and the effect of different sodium and silica content of the activators on the workability and compressive strength of geopolymers was investigated. The parameters used in this study were the mass ratio of Na2O-to-binder (for sodium content), and SiO2-to-Na2O of the activator (for silica content). Geopolymer mixtures that achieved the highest compressive strength from each precursor were assessed for their resistance to alkali-silica reaction and compared against the performance of portland cement mixtures. Test results revealed that GGF and fly ash-based geopolymers performed better than glass-powder-based geopolymer mixtures. The resistance of GGF-based and fly ash-based geopolymers to alkali-silica reaction was superior to that of portland cement mixtures, while glass-powder-based geopolymer showed inferior performance.Se estudiaron las características de resistencia y durabilidad de geopolímeros producidos utilizando tres precursores, formados por cenizas volantes, Fibra de Vidrio Esmerilado (FVE) y vidrio en polvo. Se utilizaron combinaciones de soluciones de hidróxido de sodio y silicato de sodio como activadores, y se investigó el efecto del diferente contenido de sodio y sílice de los activadores en la trabajabilidad y resistencia a la compresión de los geopolímeros. Los parámetros utilizados en este estudio fueron la relación de masa de Na2O-a-aglutinante (para el contenido de sodio), y SiO2-a-Na2 O del activador (para el contenido de sílice). Las mezclas de geopolímeros obtenidas a partir de cada precursor que alcanzaron la más alta resistencia a la compresión fueron evaluadas por su resistencia a la reacción álcali-sílice y comparadas con el rendimiento de las mezclas de cemento portland. Los resultados de las pruebas revelaron que la FVE y los geopolímeros a base de ceniza volante se comportaron mejor que las mezclas de geopolímeros a base de vidrio en polvo. La resistencia de los geopolímeros a base de ceniza volante y FVE a la reacción álcali-sílice fue superior que la de las mezclas de cemento portland, mientras que los geopolímeros a base de vidrio en polvo mostraron un rendimiento inferior

A Comparative Study on the Durability of Geopolymer Mortars Produced with Ground Glass Fiber, Fly Ash, and Glass-Powder in Sodium Sulfate Solution

An experimental investigation was conducted to investigate the performance of geopolymers made with three different precursors consisting of fly ash, Ground Glass Fiber (GGF), and Glass-Powder (GLP) exposed to sodium sulfate solution. Precursors were activated using either sodium hydroxide solution or combinations of sodium hydroxide and sodium silicate solution with varying levels of sodium and silica content. Among the mixtures with each of the three precursors, mortar mixtures with the highest compressive strength were selected to test their resistance against exposure to a 5% sodium sulfate solution. Changes in the weight and compressive strength of the specimens were monitored up to 120 days of exposure. In addition, change in the microstructure of geopolymer samples and mineral phases was investigated using SEM-EDX and XRD analyses, respectively. Further, techniques such as mercury intrusion porosimetry (MIP) spectrometry and inductively coupled plasma mass spectrometry (ICP-MS) were used to study the pore structure and the leachability of elements from geopolymers, respectively. Results of this study revealed that the GGF and fly ash-based geopolymers performed significantly better in comparison to the GLP-based geopolymer, when exposed to the sodium sulfate solution. The durability of GGF and Fly ash based geopolymer samples could be related to their stable alumino-silicate gel that develops upon geopolymerisation as well as the low amount of calcium oxide in the geopolymer systems. On the other hand, the poor performance of the GLP-based geopolymer could be related to the less stable geopolymerisation products which result in increased porosity, and the high amount of available alkalis present in the raw GLP

Role of Ground Glass Fiber as a Pozzolan in Portland Cement Concrete

Millions of tons of fiberglass are produced annually for a variety of applications. Because of stringent quality requirements and operational characteristics of the manufacturing plants, a significant quantity of fiberglass that does not meet required specifications of the industry ends up as waste in landfills. This study investigated the use of ground glass fiber (GGF) that had been discarded by plants because it did not meet prescribed standards, as a supplementary cementitious material (SCM) for portland cement. Three replacement levels (10%, 20%, and 30% by mass) for portland cement in paste, mortar, and concrete mixtures were studied. Mechanical and durability properties of the mixtures were compared with two control mixtures: a mixture made up of 100% portland cement and a mixture with 25% Class F fly ash as a cement replacement material. It was observed in these studies that even though replacement of portland cement with GGF did not lead to any significant changes in the mechanical behavior of hardened concrete, there were significant improvements in durability properties at replacement levels up to as high as 20%. The use of GGF was found to improve significantly the resistance of mortar mixtures to alkali–silica reaction and sulfate attack. In addition, the use of GGF as an SCM significantly reduced the chloride ion permeability of concrete. Results of this study show that using GGF as an SCM can result in a better durability performance compared with a mixture with a similar level of Class F fly ash