Super-critical carbonation of glass-fibre reinforced cement. Part 1: mechanical testing and chemical analysis

Purnell, Phil; Short, N. R.; Page, Christopher

doi:10.1016/s1359-835x(01)00019-7

Cited by 40 publications

(48 citation statements)

References 19 publications

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“…This ageing can nullify the positive effects of glass fibers undergoing from a ductile to a brittle material. Different strategies for improving the durability of GRC have been attempted by modifying the fibers and/or by altering the alkalinity of the matrix [7][8][9]. All these improvements have been evaluated by mechanical tests after accelerated ageing.…”

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Nondestructive Monitoring of Ageing of Alkali Resistant Glass Fiber Reinforced Cement (GRC)

et al. 2013

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Glass fiber reinforced cement (GRC) is a composite material made of portland cement mortar and alkali resistant (AR) fibers. AR fibers are added to portland cement to give the material additional flexural strength and toughness.However ageing deteriorates the fibers and as a result the improvement in the mechanical properties resulted from the fiber addition disappears as the structure becomes old. The aim of this paper is monitoring GRC ageing by nondestructive evaluation (NDE) techniques. Two different NDE techniques -1) nonlinear impact resonant acoustic spectroscopy analysis and 2) propagating ultrasonic guided waves -are used for this purpose. Both techniques revealed a reduction of the nonlinear behavior in the GRC material with ageing. Specimens are then loaded to failure to obtain their strength and stiffness. Compared to the un-aged specimens the aged specimens are found to exhibit more linear behavior, have more stiffness but less toughness. Finally, undisturbed fragments on the fracture surface form mechanical tests are inspected under the electron microscope, to understand the fundamental mechanisms that cause the change in the GRC behavior with ageing.Keywords: Glass Fiber Reinforced Cement, Material Ageing, Ultrasonic Guided Waves, Nonlinear Impact Resonant Acoustic Spectroscopy, Nondestructive Evaluation. IntroductionAlkali resistant glass fiber reinforced portland cement is a cement-based composite material that has higher flexural strength and toughness than plain cement [1]. However, GRC undergoes a rapid ageing process especially in humid and alkaline environment (pH>12). This ageing can nullify the positive effects of glass fibers undergoing from a ductile to a brittle material. Different strategies for improving the durability of GRC have been attempted by modifying the fibers and/or by altering the alkalinity of the matrix [7][8][9]. All these improvements have been evaluated by mechanical tests after accelerated ageing. Accelerated ageing tests have been broadly accepted for testing the durability of GRC. They can be classified as i) Deemed to satisfy tests, (EN 1170-8 [10]) where the GRC specimens are exposed to severe conditions, and ii) predictive accelerated ageing tests [11] that are commonly used to predict the service life of the material, in real weather conditions. For example, Purnell et al. [2] established that GRC soaked for 1 day in water at 55ºC, corresponds to 100 days of exposure to the real weather conditions in the United Kingdom. However, it should be noted that the correspondence between the accelerated ageing tests and the real aging conditions is still being investigated, especially when different matrix compositions are to be compared [11][12]. Typically the ageing process has been assessed by mechanical testing or by strand in cement (SIC) tests [13][14]. The aim of this work is to assess the ageing process in GRC by two nondestructive testing techniques -1) resonance frequency tests at different impact energy levels called Nonlinear Impact Resonance Acousti...

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Nondestructive Monitoring of Ageing of Alkali Resistant Glass Fiber Reinforced Cement (GRC)

et al. 2013

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“…TSP is a more useful method for examining the microstructure of a composite than SEM when authoritative identification of phases (eg differentiation between CH and CČ) is required [12,26]. that treated samples were fully carbonated.…”

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“…The carbonation process also alters the microstructure of calcareous based composites, [1,7,8,[11][12][13][14][15]. The molecular volume of calcium carbonate (normally calcite) is 11.2%…”

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“…This reduces the total pore volume, pore size and permeability of the composite [4,6,10] and also enhances the compressive and flexural strength [7,8,10,16,17]. Accordingly, much recent work has focussed on documenting the improvements in the microstructural, mechanical and durability properties of cementitious composites afforded by treatment with scCO 2 [6,[10][11][12][13][14][15][18][19][20]. Some researchers have investigated combination of novel production methods combined with SCC with a view to enabling mass-production of high-value functional and/or structural SCC ceramic composites from a range of starting materials including cement, lime, various aggregates and waste materials (e.g.…”

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“… Pre-conditioning: a partial drying treatment design to optimise moisture levels in the green specimens to promote carbonation [12,13,24]. Samples were dried in a fan oven for 12 h at 25°C to remove ~75% of the free water.…”

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Supercritical carbonation of calcareous composites: Influence of curing

Farahi¹,

Purnell²,

Short³

2013

Cement and Concrete Composites

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This paper reports the effect of curing on the susceptibility of cementitious composites to carbonation using supercritical carbon dioxide. Samples made using a compression moulding technique were cured in water before and/or after carbonation and the effect on porosity, microstructure, solid phase assemblage and flexural strength was determined. In terms of development of mechanical strength, no benefit was gained from any period of pre-or post-carbonation curing regime. Yet samples cured prior to carbonation underwent minimal chemical reaction between supercritical carbon dioxide and calcium hydroxide, unhydrated cement or C-S-H. Thus there was no correlation between chemical degree of reaction and strength development. The effects responsible for the marked strength gain in supercritically carbonated samples must involve subtle changes in the microstructure of the C-S-H gel, not simple pore filling by calcium carbonate as is often postulated.

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Hygrothermal properties of glass fiber reinforced cements subjected to elevated temperature

et al. 2004

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Super-critical carbonation of glass-fibre reinforced cement. Part 1: mechanical testing and chemical analysis

Cited by 40 publications

References 19 publications

Nondestructive Monitoring of Ageing of Alkali Resistant Glass Fiber Reinforced Cement (GRC)

Nondestructive Monitoring of Ageing of Alkali Resistant Glass Fiber Reinforced Cement (GRC)

Supercritical carbonation of calcareous composites: Influence of curing

Hygrothermal properties of glass fiber reinforced cements subjected to elevated temperature

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