Assessment of geopolymer composites durability at one year age

https://doi.org/10.1016/j.jobe.2020.101453Get rights and content

Highlights

  • Metakaolin and colemanite are suitable for geopolymer production.

  • The highest performance was achieved by adding polyamide fiber at 1% by volume.

  • Wetting-drying curing is a beneficial method for geopolymerization.

  • The geopolymer composites resisted the durability tests performed after 1 year.

Abstract

Geopolymers are important alternative materials for use in support of recycling and sustainability, and one of the most important properties is durability. While many studies perform durability tests 28 days after production, we carried out durability tests on a mixture of geopolymers starting 365 days after production. In this case, other conditions that occur until durability conditions are applied are taken into consideration. The geopolymer mixture consisted of metakaolin (90% by wt.) and boron waste colemanite (10% by wt.). The study investigated heat and wet-dry curing methods and polyolefin and polyamide fibre ratios (0.5, 1.0, and 1.5% by vol.) on durability. Durability issues related to concrete, such as long-term exposure to hydrochloric acid, freeze-thaw cycles, and abrasion were recorded. Results show that polyamide fibres provide better results than polyolefin fibres, the optimum polyamide fibre ratio was 1%, and the wet-dry curing method increased geopolymerisation more than heat curing. The Si-O-Al bonds were found to be stronger after wet-dry curing. All durability studies showed that the compact structure of the geopolymers withstood the durability tests performed one year after production. Scanning electron microscopy (SEM) analysis supports these results.

Introduction

Geopolymers are environmentally-friendly alternatives to traditional Portland cement [1]. Their production uses less energy and emits fewer greenhouse gases than and they are more resistant to common durability issues. Geopolymers are inorganic polymers with three-dimensional Si-O-Al frameworks synthesized from aluminosilicates that can be dissolved in an alkaline medium [2]. When the durability properties were examined, they have been found to have a high rate of resistance to fire and chemicals [3,4]. This suggests that geopolymers may be used as construction material in buildings, refractories, and wastewater treatment facilities [[5], [6], [7], [8]]. While many studies carried out durability tests starting 28 days after production, we conducted tests one year after production to evaluate the long-term durability based under various conditions.

Resistance to hydrochloric acid is a significant durability issue for concrete used in environments with caustic conditions. Concrete structures may be exposed to acids as a result of urban, industrial and agricultural activities [[9], [10], [11], [12], [13]]. The quality and type of concrete, type of acid, and the solution's concentration, pH, and fluidity influence acid resistance [14,15]. Acid attacks increase permeability and porosity, resulting in loss of alkalinity, weight, and strength. Geopolymers have emerged as a promising solution to acid damage due to their ceramic-like microstructure. While many studies have been done on the durability of fly ash and slag based geopolymers, data is needed to determine the acid resistance of metakaolin-based geopolymers [[16], [17], [18], [19]]. Also, there are a limited number of studies on the resistance of geopolymers to the freeze-thaw cycle. Cai et al. [20] performed the freeze-thaw test for a slag based geopolymer concrete. The resistance coefficient was near 90% and the specimens had high resistance. Yunsheng et al. [21] produced polyvinyl alcohol reinforced geopolymer samples for a 20 cycle test; hardness tests and impact strength exhibited no influence on the specimens. The use of polyolefin and polyamide fibres in geopolymer production should also be investigated. When previous studies were examined, it was observed that bending strength and cracks were reduced by these fibres [22,23].

Numerous studies have been conducted on the type and duration of curing in the production of geopolymers. Aygörmez et al. [24] used different temperatures and durations, and found that the most suitable curing condition was 72 h at 60 °C. Arslan et al. [25] applied the wet-dry method as a curing condition with the heat curing method. Improvement in mechanical properties was observed with this treatment. While the hydration reactions of the high calcium compounds are supported during wet curing, the strength of the geopolymerisation products increases and the bonding improves during the dry curing. Also, it was observed that metakaolin and colemanite are suitable for geopolymer production. Uysal et al. [26] substituted up to 40% colemanite with metakaolin and found that 10% of colemanite substitution had positive effects [27].

The main purpose of this study was to start the tests after 365 days to evaluate long term durability. Three different durability tests (hydrochloric acid, freeze-thaw, and abrasion) were selected. A general evaluation was made instead of evaluations by individual tests. Metakaolin and boron waste colemanite were used in a mixture of 90% metakaolin plus 10% boron waste colemanite by weight. Also, three different ratios (0.5, 1.0, and 1.5% by volume) of polyolefin and polyamide fibres were used. Two different curing methods (heat curing and wet-dry curing) were applied. After the freeze-thaw test of 300 cycles and the hydrochloric acid test (10% by volume) for six months, weight loss and strength results were examined. SEM analyses were performed after the durability tests. The abrasion test was applied to the samples twice before and after 500 °C temperature. The effect of the double durability test was investigated by applying the abrasion test together with the high-temperature test. Thus, the abrasion degree after the high temperature was studied. Also, SEM analyses were performed after the durability tests.

Section snippets

Materials

Metakaolin, the main raw material, was obtained from the Kaolin EAD company (Turkey). The Fe2O3+Al2O3+SiO2 ratio of metakaolin was 97.18%. The pozzolanic activity index of the metakaolin additive determined by the supplier was 123.5% for the 7th day and 141.4% for the 28th day. Due to this situation, the metakaolin was determined to have a high pozzolanic activity ratio. Metakaolin is a very fine-grained material that easily reacts to form geopolymeric bonds. It has fine grains because the

Abrasion resistance

The abrasion test results are given in Fig. 1. Better results for weight loss were obtained with the addition of fibres because a durable layer formed [27]. When the results are examined, PA fibres provide better structural performance than PL fibres due to strong bonding within the geopolymeric matrix and high tensile strength properties [27]. When the results were examined after the abrasion test and before 500 °C, the average weight loss ranged from 0.31 g to 0.93 g. After heat treatment,

Conclusions

The results of this study can be summarised as follows:

  • Since polyamide fibres have higher tensile strength than polyolefin fibres, they produced higher results in mechanical properties. The highest results were obtained in polyamide fibres of 1% by volume in all samples, but if the volume was increased, the fibres negatively affected the results. The wet-dry curing method was used in addition to heat curing. Particles that did not react with the heat curing did continue geopolymerisation,

CRediT authorship contribution statement

Yurdakul Aygörmez: Conceptualization, Funding acquisition, Formal analysis, Data curation, Writing - original draft, Writing - review & editing, Validation. Orhan Canpolat: Conceptualization, Funding acquisition, Formal analysis, Data curation, Writing - original draft, Writing - review & editing, Validation. Mukhallad M. Al-mashhadani: Conceptualization, Funding acquisition, Formal analysis, Data curation, Writing - original draft, Writing - review & editing, Validation.

Acknowledgment

This work was supported by the research fund of the Yildiz Technical University, the authors would like to express their sincere gratitude to scientific research coordination unit for their financial support to the project (Project number: FBA-2017-3081).

References (55)

  • Z. Yunsheng et al.

    Impact properties of geopolymer based extrudates incorporated with fly ash and PVA short fiber

    Construct. Build. Mater.

    (2008)
  • T.Y. Han et al.

    Influence of polyolefin fibers on the engineering properties of cement-based composites containing silica fume

    Mater. Des.

    (2012)
  • Z. Deng et al.

    Characterisation of macro polyolefin fibre reinforcement in concrete through round determinate panel test

    Construct. Build. Mater.

    (2016)
  • A.A. Arslan et al.

    Influence of wetting-drying curing system on the performance of fiber reinforced metakaolin-based geopolymer composites

    Construct. Build. Mater.

    (2019)
  • M. Uysal et al.

    Effect of using colemanite waste and silica fume as partial replacement on the performance of metakaolin-based geopolymer mortars

    Construct. Build. Mater.

    (2018)
  • A. Celik et al.

    High-temperature behavior and mechanical characteristics of boron waste additive metakaolin based geopolymer composites reinforced with synthetic fibers

    Construct. Build. Mater.

    (2018)
  • M.M. Al-mashhadani et al.

    Mechanical and microstructural characterization of fiber reinforced fly ash based geopolymer composites

    Construct. Build. Mater.

    (2018)
  • N. Kabay

    Abrasion resistance and fracture energy of concretes with basalt fiber

    Construct. Build. Mater.

    (2014)
  • F. Puertas et al.

    Mechanical and durable behaviour of alkaline cement mortars reinforced with polypropylene fibres

    Cement Concr. Res.

    (2003)
  • Y. Aygörmez et al.

    Elevated temperature, freezing-thawing and wetting-drying effects on polypropylene fiber reinforced metakaolin based geopolymer composites

    Construct. Build. Mater.

    (2020)
  • S. Pilehvar et al.

    Effect of freeze-thaw cycles on the mechanical behavior of geopolymer concrete and Portland cement concrete containing micro-encapsulated phase change materials

    Construct. Build. Mater.

    (2019)
  • A. Allahverdi et al.

    Resistance of chemically-activated high phosphorous slag content cement against freeze–thaw cycles

    Cold Reg. Sci. Technol.

    (2014)
  • L. Basheer et al.

    Assessment of the durability of concrete from its permeation properties: a review

    Construct. Build. Mater.

    (2001)
  • R. Zhao et al.

    Freeze-thaw resistance of Class F fly ash-based geopolymer concrete

    Construct. Build. Mater.

    (2019)
  • J.J. Chang et al.

    Effects of gypsum and phosphoric acid on the properties of sodium silicate-based alkali-activated slag pastes

    Cement Concr. Compos.

    (2005)
  • B. Nematollahi et al.

    Microscale investigation of fiber-matrix interface properties of strain hardening geopolymer composite

    Ceram. Int.

    (2017)
  • R.P. Williams et al.

    Development of alkali activated borosilicate inorganic polymers (AABSIP)

    J. Eur. Ceram. Soc.

    (2011)
  • Cited by (53)

    View all citing articles on Scopus
    View full text