Mortar damage due to airborne sulfur compounds in a simulation chamber

Zappia, G.; Sabbioni, C.; Pauri, Marco; Gobbi, G.

doi:10.1007/bf02473451

Cited by 41 publications

(25 citation statements)

References 16 publications

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“…6 b) indicates a certain degree of carbonation. Besides, sulfite appears as an intermediate stage previous to the sulfate formation [28][29][30]. In weathering exposure (climatic chamber), after 7 test days, the aerial lime mortars do not withstand the climatic cycles, and a total destruction of the specimens is produced.…”

Section: Discussionmentioning

confidence: 99%

Compositional changes in lime-based mortars exposed to different environments

2005

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Specimens of aerial and hydraulic lime-based mortars to be used in restoration works were prepared, hardened and subjected to different environments to study their compositional changes during setting, hardening and exposure to environment. Outside exposure, weathering cycles in a climatic chamber, SO 2 -rich environment and indoor exposure (as control group) were selected to expose the mortars. XRD, FTIR and TG-DTA analyses were performed at 7, 14, 21 and 28 days to determine the chemical and mineralogical composition, as well as the formation of the degradation products. Outside and SO 2 -chamber exposures and increasing the relative humidity allowed faster carbonation (enhancing CO 2 (g) dissolution) and hydration of hydraulic compounds. In SO 2 -chamber, sulfate attack appears as a surface phenomenon, giving: gypsum in aerial specimens and gypsum and syngenite in hydraulic specimens.

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Section: Discussionmentioning

confidence: 99%

Compositional changes in lime-based mortars exposed to different environments

2005

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“…The extent to which a mortar is affected by these deterioration factors is a function of the mortar's properties, which depend, in turn, on several issues, such as the kind and characteristics of the binder and the aggregate, the binder/aggregate ratio, the amount of mixing water, the mortar's permeability [9][10][11][12], the water absorption capacity through capillarity [10,13], water intake [7,14,15], the presence of admixtures and the curing conditions [16][17][18]. SO 2 exposure is supposed to affect the mortars because gaseous SO 2 has been widely reported to react with calcium carbonate, giving rise to the formation of both calcium sulphite hemihydrate (CaSO 3 .1/2H 2 O) and calcium sulphate dihydrate (CaSO 4 ·2H 2 O) on the mortar's surfaces [6,8,[19][20][21]. Calcium sulphite has been considered to be the most important product obtained under certain circumstances, such as the absence of catalyst [21,22].…”

Section: Introductionmentioning

confidence: 99%

“…SO 2 exposure is supposed to affect the mortars because gaseous SO 2 has been widely reported to react with calcium carbonate, giving rise to the formation of both calcium sulphite hemihydrate (CaSO 3 .1/2H 2 O) and calcium sulphate dihydrate (CaSO 4 ·2H 2 O) on the mortar's surfaces [6,8,[19][20][21]. Calcium sulphite has been considered to be the most important product obtained under certain circumstances, such as the absence of catalyst [21,22]. It also acts as an intermediate product, because its oxidation gives rise to calcium sulphate formation [21,23,24].…”

Section: Introductionmentioning

confidence: 99%

“…Calcium sulphite has been considered to be the most important product obtained under certain circumstances, such as the absence of catalyst [21,22]. It also acts as an intermediate product, because its oxidation gives rise to calcium sulphate formation [21,23,24]. Calcium sulphate dihydrate appears as the most important product of decay in carbonated materials when suitable catalysts are present [23].…”

Section: Introductionmentioning

confidence: 99%

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Ageing of lime mortars with admixtures: Durability and strength assessment

Izaguirre

Lanas²,

Álvarez

2010

Cement and Concrete Research

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Lime-based mortars modified with admixtures were prepared and subjected to different environments such as outdoor and indoor exposures, climatic chamber, SO 2 -chamber, and freezing-thawing cycles. The influence that the different admixtures (water repellents, water retainers, polypropylene fibre and a viscosity modifier) had on the pore size distribution of the hardened specimens was assessed and related to the water absorption capacity, and hence to the durability. Ageing resistance and mechanical strengths improved when additives reduced the water intake and increased the aircontent. High dosages of water repellents were necessary to enhance the durability, sodium oleate being the most effective additive to endure freezing processes. Also the low tested dosage of fibre, a water retainer (guar gum derivative), and a starch proved to be useful. SO 2 deposition caused the formation of calcium sulphite hemihydrate as the main degradation product. A very small amount of calcium sulphate dihydrate was observed. A crystal habit composed of acicular agglomerates of calcium sulphite hemihydrate was detected in SO 2 deposition on calcareous materials.3

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“…From the previous works about the SO 2 and other pollutants deposition, it was unquestionably achieved enough knowledge about the chemical reactions [10], the catalysts in SO 2 oxidation [11,18], the sulfite and sulfate quantification [19] and the black crusts formed by deposition of environmental pollution [20]. However, these facts could have mechanical repercussions, for example: a SO 2 -rich environment causes the formation of gypsum (CaSO 4 ·2H 2 O) on the external layer of the mortar surface [8,11].…”

Section: Introductionmentioning

confidence: 99%

Study of the mechanical behavior of masonry repair lime-based mortars cured and exposed under different conditions

Lanas

Sirera

Álvarez

2006

Cement and Concrete Research

112

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Specimens of aerial and hydraulic lime-based mortars to be used in restoration works were prepared, hardened and subjected to different environments in order to study their mechanical behavior and durability. Outside exposure, weathering cycles in a climatic chamber, SO 2 -rich environment, freezing-thawing cycles and indoor exposure were selected to expose (as control group) the mortars.Flexural and compression strength tests were performed at 7, 14, 21 and 28 days. Porosity values and SEM-EDAX analysis were used to evaluate the microstructural changes.Flexural strength has been strongly influenced by the RH of the environments. Outside exposure improves, in general, the compressive strength, whereas SO 2 -chamber only provides the strength in hydraulic specimens. Porosity reduction has been related with a strength increment.In climatic chamber, the porosity increment matches a gradual higher degree of alteration. A strength reduction has been determined through a fracture mechanism using the cracks of climatic alteration. In SO 2 -chamber, sulfation appears as a surface phenomenon, giving gypsum in aerial specimens and gypsum and syngenite in hydraulic specimens, as SEM/EDAX confirms. Freezing-thawing cycles showed a high destruction capacity. Hydraulic specimens endured better durability tests than aerial specimens: a discussion on the mortar durability was also introduced.

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Mortar damage due to airborne sulfur compounds in a simulation chamber

Cited by 41 publications

References 16 publications

Compositional changes in lime-based mortars exposed to different environments

Compositional changes in lime-based mortars exposed to different environments

Ageing of lime mortars with admixtures: Durability and strength assessment

Study of the mechanical behavior of masonry repair lime-based mortars cured and exposed under different conditions

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