Decalcification resistance of alkali-activated slag

Komljenović, Miroslav; Baščarević, Zvezdana; Marjanović, Nataša; Nikolić, Violeta N.

doi:10.1016/j.jhazmat.2012.06.063

Cited by 58 publications

(23 citation statements)

References 64 publications

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“…This is likely due to decalcification of the main binder gel which leaves a more polymerised gel with lower calcium content in the case of GP samples [55]. In the case of PC the decalcification of C-S-H results in dissolution of calcium, leaving behind a porous corroded layer [56]. Bernal et al (2013) [26] reported that the extent of the structural damage to the binding gel can be identified by the extent of the shift to higher wavenumbers and by the change in intensity of the bands.…”

Section: Mass Lossmentioning

confidence: 99%

Resistance of geopolymer and Portland cement based systems to silage effluent attack

Aiken

Sha

Kwasny

et al. 2017

Cement and Concrete Research

109

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Abstract:Traditional Portland cement (PC) concrete has been used for many years in the agricultural industry for the construction of silos and silage effluent storage facilities. However, the acidic nature of the silage effluent produced by silage has led to severe degradation of PC concrete which in turn has significant environmental and financial implications. This study compares the resistance of PC and geopolymer (GP) mortars and pastes to silage effluent over 12 months. The GP samples displayed increased resistance to silage effluent in terms of mass and strength loss. Analysis of microstructure suggests that the increased stability of the reaction products is the main factor behind increased silage effluent resistance when compared with PC. It was also found that pulverised fuel ash (PFA) and ground granulated blast furnace slag (GGBS) blends with a higher PFA content may offer increased long term silage effluent resistance due to the nature of the main binder gel produced in PFA dominant systems.

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Section: Mass Lossmentioning

confidence: 99%

Resistance of geopolymer and Portland cement based systems to silage effluent attack

Aiken

Sha

Kwasny

et al. 2017

Cement and Concrete Research

109

View full text Add to dashboard Cite

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“…The area with a smooth surface had a low Ca/Si atomic ratio (~1.3) due to the decalcification of C-S-H, resulting in the coexistence of silica gel or M-S-H with C-S-H gel. The decreased Ca/Si atomic ratio explained the decrease in strength (Komljenović et al 2012), which led to a more smooth surface than the fresh paste.…”

Section: Microstructural Analysismentioning

confidence: 98%

“…Portlandite starts to decompose when the pH is below 12 (Shi and Stegemann 2000). As the pH drops, C-S-H could continuously release Ca 2+ ion until most of the Ca 2+ is released when the pH is below 9 (Komljenović et al 2012;Shi and Stegemann 2000). In terms of reaction products, Brown (Brown 1981) noticed that ettringite was stable at a pH of 11.5, unstable at a pH of 10 and highly unstable at a pH of 6.…”

Section: Ph Of Sulfate Solutionsmentioning

confidence: 99%

Evaluation of Sulfate Resistance of Calcined Dolomite Activated Ground Granulated Blast Furnace Slag

Jin

Al‐Tabbaa

et al. 2016

J. Mater. Civ. Eng.

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Aggressive environments significantly influence the durability and serviceability of hardened cement and concrete. This paper presents an evaluation of the resistance of ground granulated blastfurnace slag (GGBS) activated with calcined dolomite, as a novel alkali activator, to 5% sodium sulfate attack and 5% magnesium sulfate attack. Two calcined dolomites, D800 and D1000, were prepared in the laboratory at 800 °C and 1000 °C respectively. The results demonstrated the good potential of using calcined dolomite activated slag in resisting sulfate attack. Immersion in Na 2 SO 4 (aq) led to an increase in strength in both the D800 (D800S) and the Portland cement CEM I 52.5N (PCS) activated slag, with a more pronounced effect in the former, while a decrease in the D1000 (D1000S) activated slag. On the Manuscript Click here to download Manuscript: Manuscript_revised.docx other hand, calcined dolomite activated slag had less strength loss than PCS after MgSO 4 attack. The products of sulfate attack and the deterioration processes are also analyzed by a range of tests including pH, weight change, corroded depth, XRD, TGA and SEM/EDS. After Na 2 SO 4 attack, the main product on D800S and D1000S was gypsum with a larger amount in the later. Gypsum, thaumasite and M-S-H were the main products of D800S and D1000S after MgSO 4 attack. The better resistance of D800S to sulfate attack was attributed to the absence of portlandite in the hydrated paste. On the other hand, the presence of portlandite in D1000S led to the inhomogeneous sulfate ions inward progression hence the severe deterioration of sample was observed.

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“…When exposed to the saline solutions, the UCS of the specimens decreased significantly by about 40%. The strength reduction in saline solutions may be explained as follows: Firstly, the large amount of Na + in the leachates potentially replaces the Ca 2+ in C-S-H, which lowered the Ca/Si ratio and resulted in strength reduction of C-S-H [44][45][46]. Secondly, as mentioned above, disruptive pressures generated by recrystallized saline (NaCl and Na 2 SO 4 ) in pores resulted in the development of microcracks.…”

Section: Strength Evolutionmentioning

confidence: 99%

Durability Evaluation of Phosphogypsum-Based Cemented Backfill Through Drying-Wetting Cycles

Zhou

et al. 2019

Minerals

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In this study, the durability of phosphogypsum (PG)-based cemented backfill was investigated by drying-wetting cycles to explore deterioration of its strength and the release of impurities. The leachates in this test were composed of deionized water, 5% Na2SO4 solution, 5% NaCl solution, and a range of sulfuric acid solutions with pH values of 1.5, 3, and 5. After drying-wetting cycles, unconfined compressive strength (UCS), visual deterioration, porosity, microstructure and concentrations of phosphate and fluoride in the leachates were measured. The results showed that both saline and acidic solutions could lead to strength reduction of PG-based cemented backfill under different deterioration mechanisms. The mechanical damage of salinity was caused by micro-cracking and degradation of C–S–H. However, the H+ broke the backfill by dissolving hydration products, leaving the conjunctures between PG particles weakened. Furthermore, the environmental impact was investigated by measuring the concentration of phosphate and fluoride in the leachates. In acidic solutions, the release of phosphate and fluoride was greatly enhanced by H+. Compared to the great strength deterioration in saline leachates, the concentration of phosphate and fluoride were similar to that of deionized water, indicating that saline solutions had little impact on the release of hazardous impurities.

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Decalcification resistance of alkali-activated slag

Cited by 58 publications

References 64 publications

Resistance of geopolymer and Portland cement based systems to silage effluent attack

Resistance of geopolymer and Portland cement based systems to silage effluent attack

Evaluation of Sulfate Resistance of Calcined Dolomite Activated Ground Granulated Blast Furnace Slag

Durability Evaluation of Phosphogypsum-Based Cemented Backfill Through Drying-Wetting Cycles

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