Waste glass as partial mineral precursor in alkali-activated slag/fly ash system

Zhang, Shizhe; Keulen, A Arno; Arbi, K.; Ye, Guang

doi:10.1016/j.cemconres.2017.08.012

Cited by 196 publications

(75 citation statements)

References 61 publications

(73 reference statements)

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“…After 20% of waste glass powder was introduced in the slag-fly ash binder, the Si-O-T peaks in all waste glass mixtures exhibits a shift to higher wavenumbers. The addition of waste glass powder introduced an additional Si source to the reaction system; as a consequence, more Si could be incorporated into the gel network to form a Si rich structure [40], which can generate a higher polymerziation degree of reaction products.…”

Section: Xrd and Ftir Analysismentioning

confidence: 99%

Waste glass as binder in alkali activated slag–fly ash mortars

2019

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This paper illustrates the application of waste glass powder as part of the binder in slag-fly ash systems activated by NaOH and NaOH/Na 2 CO 3 activators. To evaluate the reaction kinetics, reaction products, mechanical properties, and durability performance of glass powder modified alkali activated slag-fly ash systems, calorimetry test, X-ray diffraction, FTIR, strength test, drying shrinkage tests, and carbonation test were conducted. From the isothermal calorimeter results, glass powder shows a higher reactivity compared to fly ash but still lower than slag. The reaction products of glass power modified samples exhibit an enhancement of polymerization degree of Si-O-T, observed in FTIR. As a consequence, higher drying shrinkage exists in glass modified mortars. The mechanical performance of different samples is mostly controlled by the Ca/Si of dry mixtures and activator type. After the slag-fly ash binder system was modified by the waste glass, a significant enhancement of resistance to carbonation was identified, especially for NaOH/Na 2 CO 3 activated mortars, which show an increase of 300% on the carbonation resistance ability compared to the reference sample. The Na/(Si ? Al) ratio of dry mixtures exhibits a positive correlation with carbonation resistance.

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Section: Xrd and Ftir Analysismentioning

confidence: 99%

Waste glass as binder in alkali activated slag–fly ash mortars

2019

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“…To activate the raw materials, two alkali solutions were used, i.e., sodium hydroxide (NaOH) and combined sodium hydroxide and sodium silicate (NaOH + Na 2 SiO 3 ). The NaOH solution was prepared by dissolving NaOH pellets (assay 97%) in distilled water to obtain a concentration of 4 M. It is optimal to use this considering the hardening of high-calcium composites, i.e., class-C FA and GGBS [27][28][29]. Additionally, at low hydroxyl concentration, the dissolving of Ca 2+ increases, leading to the maximum formation of C-S-H in the matrix [30].…”

Section: Introductionmentioning

confidence: 99%

“…To prepare the NaOH + Na 2 SiO 3 , the synthetically produced Na 2 SiO 3 (molecular weight 122.06; assay: 9%-10% Na 2 O, 28%-30% SiO 2 ) was used and mixed with a freshly made NaOH (4M) solution then cooled to room temperature for 24 h. The optimal ratio of Na 2 SiO 3 /NaOH = 1.5 was used in this study to avoid the excessive silicates in mixture, which may negatively affect the geopolymeric structure formation, as well as water evaporation [31,32]. concentration of 4 M. It is optimal to use this considering the hardening of high-calcium composites, i.e., class-C FA and GGBS [27][28][29]. Additionally, at low hydroxyl concentration, the dissolving of Ca 2+ increases, leading to the maximum formation of C-S-H in the matrix [30].…”

Section: Introductionmentioning

confidence: 99%

Strength and Microstructure of Class-C Fly Ash and GGBS Blend Geopolymer Activated in NaOH & NaOH + Na2SiO3

et al. 2019

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In this paper, class-C fly ash (FA) and ground granulated blast-furnace slag (GGBS)-based geopolymer activated in NaOH and NaOH + Na 2 SiO 3 was studied regarding setting time, compressive strength, porosity, microstructure, and formation of crystalline phases. When comparing the effects of alkali type on the FA and GGBS geopolymer composites, results revealed that NaOH has a lesser effect in developing strength and denser microstructure than does NaOH + Na 2 SiO 3, since the addition of Na 2 SiO 3 provides the silica source to develop more compact structure. Incorporation of Na 2 SiO 3 reduced the crystallinity and the paste was more amorphous compared to NaOH activated pastes. The class-C FA and GGBS blends resulted in prolonged setting time, reduced strength, and loose matrix with the increase in fly ash content. The un-reactivity of calcium in blends was observed with increasing fly ash content, leading to strength loss. It is evident from XRD patterns that calcium in fly ash did not contribute in forming C-S-H bond, but formation of crystalline calcite was observed. Furthermore, XRD analyses revealed that the reduction in fly ash leads to the reduction in crystallinity, and SEM micrographs showed the unreactive fly ash particles, which hinder the formation of a denser matrix.Materials 2020, 13, 59 2 of 15 is also formed in Portland cement. Its formation leads to short setting time, reduced porosity, and increased compressive strength [9,10].Fly ash has been investigated as a precursor material in geopolymer mortar. The mechanical properties of fly ash-based geopolymer depends on the chemical composition of fly ash. As explored by Davidovits, Izquierdo [11] in their study, the fly ash containing low calcium (class-F) produced a workable geopolymer; however, the high calcium in fly ash did not contribute in producing the suitable geopolymer due to flash setting time. The flash setting time in the high-calcium fly ash was confirmed in studies [12,13] where they used borax in the mixture to delay the setting time. However, regardless of this problem, the class-C fly ash has been found to help improve the strength properties due the presence of adequate calcium content, which may forms C-S-H gel in the matrix [14].Ground granulated blast-furnace slag (GGBS) is another by-product material rich in amorphous calcium, silica, and alumina, which makes it suitable to be used as a binder in the construction industry [15]. Formerly, GGBS as a precursor material in geopolymer has been investigated. It is worth mentioning that the GGBS activated in alkali solution possess a high strength and good resistance to the chemicals compared to Portland cement. However, the reduced setting time makes it susceptible to high shrinkage and develops micro cracks, which increases the porosity leading to the strength loss [16]. Since the GGBS is rich in calcium, the main reaction product is C-S-H gel, which may coexist with the geopolymer gel depending on the chemical composition of the GGBS, alkali type, and alkali amount [4,17,18].The ...

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“…Due to its chemistry and its availability, waste glass is therefore a good candidate for the production of AAB. Some recent studies describe its utilisation as total or partial replacement of usual precursors, suggesting that satisfactory strength can be achieved by activation of 100% waste glass fibres with NaOH only [23] or by substituting up to 60% of fly ash in blended fly ash-ground granulated blast furnace slag (GGBS) system [24].…”

Section: Introductionmentioning

confidence: 99%

Production of sodium silicate powder from waste glass cullet for alkali activation of alternative binders

Vinai

Soutsos

2019

Cement and Concrete Research

197

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A simple process to produce sodium silicate powder from glass cullet has been developed. A mixture of glass powder, sodium hydroxide powder, and water was heated at temperatures of 150 to 330 °C. The effects of glass to NaOH ratio, temperature and duration, inclusion of water and fineness of NaOH were investigated. Fly ash and fly ash/GGBS blends were the precursors for alkali activated binder (AAB) mortars produced with this sodium silicate. Compressive strengths were similar to or better than those obtained with commercially available sodium silicate and sodium hydroxide solutions. FT-IR tests suggested that the reactivity of the glass derived sodium silicate powder was related to the number of non-bridging oxygen atoms in the silicate structure. Cost comparison between AAB and Portland cement concretes gave similar results for normal strength concretes (35 MPa). AAB concretes with higher strengths (50 and 70 MPa) can be cheaper than equivalent traditional concrete.

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Waste glass as partial mineral precursor in alkali-activated slag/fly ash system

Cited by 196 publications

References 61 publications

Waste glass as binder in alkali activated slag–fly ash mortars

Waste glass as binder in alkali activated slag–fly ash mortars

Strength and Microstructure of Class-C Fly Ash and GGBS Blend Geopolymer Activated in NaOH & NaOH + Na2SiO3

Production of sodium silicate powder from waste glass cullet for alkali activation of alternative binders

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