Development of low-pH cementitious materials based on CAC for HLW repositories: Long-term hydration and resistance against groundwater aggression

Calvo, José Luis García; Alonso, C.; Hidalgo, Antonio Vásquez; Luco, Luis Fernández; Flor-Laguna, V.

doi:10.1016/j.cemconres.2013.04.008

Cited by 25 publications

(5 citation statements)

References 22 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For instance, the use of calcium aluminate cement (CAC) to safely encapsulate hazardous materials has been recognized to be highly effective . The relatively low pH of this kind of cement matrix (10.5-11.5), in comparison with the OPC system, has been highlighted as a favourable property for high and intermediate level waste (HLW and ILW) repositories because of its acidic chemical attack resistance (García-Calvo et al, 2013;Swift et al, 2013a). Furthermore, the high early strength, abrasion endurance, and the possibility of low ambient temperature application, have been reported as other advantages related to using CAC (Ukrainczyk et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Treatment of toxic metal aqueous solutions: Encapsulation in a phosphate-calcium aluminate matrix

Fernández

Navarro-Blasco

Durán

et al. 2014

Journal of Environmental Management

View full text Add to dashboard Cite

Polyphosphate-modified calcium aluminate cement matrices were prepared by using aqueous solutions polluted with toxic metals as mixing water to obtain wastecontaining solid blocks with improved management and disposal. Synthetically contaminated waters containing either Pb or Cu or Zn were incorporated into phosphoaluminate cement mortars and the effects of the metal's presence on setting time and mechanical performance were assessed. Sorption and leaching tests were also executed and both retention and release patterns were investigated. For all three metals, high uptake capacities as well as percentages of retention larger than 99.9% were measured. Both Pb and Cu were seen to be largely compatible with this cementitious matrix, rendering the obtained blocks suitable for landfilling or for building purposes. However, Zn spoilt the compressive strength values because of its reaction with hydrogen phosphate anions, hindering the development of the binding matrix.

show abstract

Section: Introductionmentioning

confidence: 99%

Treatment of toxic metal aqueous solutions: Encapsulation in a phosphate-calcium aluminate matrix

Fernández

Navarro-Blasco

Durán

et al. 2014

Journal of Environmental Management

View full text Add to dashboard Cite

show abstract

“…According to the microstructural changes observed within the cracks, not only the appearance but also the chemical composition of the precipitates differed from XA-CA to XA-CA+ANF and XA-CA+CNC, these being ettringite and calcite respectively. Ettringite formation is observed, although the delayed ettringite formation is a known expansion problem that can promote microcracking (26,51,52). Over the period evaluated, calcium sulphoaluminate phases grew in the crack, and clear profiles of sulphate and chlorides were detected in the uncracked region (Figure 10 and Figure 11), which confirm penetration into the matrix and the corresponding decrease in the leaching media with no microcracking associated with their formation.…”

Section: Crack Microstructurementioning

confidence: 79%

Durability of UHPFRC functionalised with nanoadditives due to synergies in the action of sulphate and chloride in cracked and uncracked states

et al. 2021

Self Cite

View full text Add to dashboard Cite

This paper studies the durability of Ultra High Performance Fibre Reinforced Concrete (UHPFRC) with high Blast Furnace Slag content (BFS) and nanoadditives such as crystalline admixture (CA), alumina nanofibres (ANF) and cellulose nanocrystals (CNC), exposed to different aggressive environmental conditions: 1) three aggressive media: a) deionized water (dw), b) sulphate rich solution (ss) and c) simulated geothermal water (sgw) containing sulphate and chloride; 2) two water interaction conditions: a) static and b) dynamic (water impact); and 3) with and without the presence of cracks. Durability was analysed over 24 months, measuring several physical and chemical parameters of the system, recording changes in both the aggressive media and the concrete. All UHPFRC types demonstrate good durability, showing high resistance to expansion and deformation in the sulphate-rich media. A leaching process occurs in all water interaction systems, the dynamic interaction in sgw being the most aggressive. The interaction of sgw inside the crack favours the formation of solid phases such as calcium carbonates and ettringite, while the presence of nanoadditives affects the response of both the matrix and the formation of precipitates within the crack.

show abstract

“…Among others, formation of magnesium silicates has been observed in the alkaline reaction zone, at the interface between concrete and clay (Dauzères et al, 2014). This issue became more important when low-pH cementititous materials started to be considered in order to minimize the geochemical interactions with the clay barriers (Calvo et al, 2013;Calvo et al, 2010). High-pH cementitious materials exhibit a low content in Mg, but the addition of supplementary cementitious materials such as fly ash and blast furnace slag in the formulation of low-pH concrete compositions, increase the content of available Al and Mg.…”

Section: Introductionmentioning

confidence: 99%

Geochemical conditions for the formation of Mg silicates phases in bentonite and implications for radioactive waste disposal

Fernández

González-Santamaría

Angulo

et al. 2018

Applied Geochemistry

View full text Add to dashboard Cite

The present study evaluates the formation of magnesium silicates phases as a result of the alkaline alteration of FEBEX bentonite in long-term experiments. The results are relevant in the context of radioactive waste disposal since the bentonite barrier will partly change its original mineralogy and condition its long-term geochemical behavior. Bentonite samples from an in situ experiment of interaction with a CEM-II-type concrete performed for 13 years in a rock gallery and a laboratory experiment of interaction with a CEM-Itype concrete performed for 10 years provide some experimental evidences on the mineralogical alteration.Results required multiple analytical techniques to resolve the nature of the Mg silicates. X-ray diffraction, thermogravimetric analyses, scanning electron microscopy, infrared spectroscopy and 27 Al and 29 Si nuclear magnetic resonance have been used. The mineralogical alteration is complex since several Mg silicates may coexist in the same region not only with themselves but also with carbonates and calcium (aluminium) silicate hydrates. Brucite intercalation in the interlayer of smectite, previously reported as a chlorite-like phase in a former study, is observed. In addition, a serpentine-type mineral phase was better observed in the in situ samples, at least by XRD, and a 2:1 trioctahedral phyllosilicates was better observed in the laboratory samples. Formation of Mg silicates in the bentonite barrier may buffer the Ca alkaline front originated in concrete and may decrease the porosity at the concrete-bentonite interface.

show abstract

Development of low-pH cementitious materials based on CAC for HLW repositories: Long-term hydration and resistance against groundwater aggression

Cited by 25 publications

References 22 publications

Treatment of toxic metal aqueous solutions: Encapsulation in a phosphate-calcium aluminate matrix

Treatment of toxic metal aqueous solutions: Encapsulation in a phosphate-calcium aluminate matrix

Durability of UHPFRC functionalised with nanoadditives due to synergies in the action of sulphate and chloride in cracked and uncracked states

Geochemical conditions for the formation of Mg silicates phases in bentonite and implications for radioactive waste disposal

Contact Info

Product

Resources

About