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John L Provis - One of the best experts on this subject based on the ideXlab platform.
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uptake of chloride and carbonate by mg al and ca al layered double hydroxides in simulated pore solutions of alkali activated Slag Cement
Cement and Concrete Research, 2017Co-Authors: Susa A Ernal, John L ProvisAbstract:Chloride ingress and carbonation are major causes of degradation of reinforced concrete. To enable prediction of chloride ingress, and thus to improve the durability of structural alkali-activated Slag Cement (AAS) based concretes, it is necessary to understand the ionic interactions taking place between chlorides, carbonates, and the individual solid phases which comprise AAS. This study focused on two layered double hydroxides (LDH) representing those typically identified as reaction products in AAS: an Mg-Al hydrotalcite-like phase, and an AFm structure (stratlingite), in simulated AAS pore solutions. Surface adsorption and interlayer ion-exchange of chlorides occurred in both LDH phases; however, chloride uptake in hydrotalcite-group structures is governed by surface adsorption, while stratlingite shows the formation of a hydrocalumite-like phase and ion exchange. For both Ca-Al and Mg-Al LDHs, decreased chloride uptakes were observed from solutions with increased [CO32−]/[OH−] ratios, due to the formation of carbonate-containing hydrotalcite and decomposition of AFm phases, respectively.
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alkali activated Slag Cements produced with a blended sodium carbonate sodium silicate activator
Advances in Cement Research, 2016Co-Authors: Susan A Bernal, Rackel San Nicolas, Jannie S J Van Deventer, John L ProvisAbstract:An alkali-activated Slag Cement produced with a blend of sodium carbonate/sodium silicate activator was characterised. This binder hardened within 12 h and achieved a compressive strength of 20 MPa...
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alkali activated Slag Cements produced with a blended sodium carbonate sodium silicate activator
Advances in Cement Research, 2016Co-Authors: Susan A Bernal, Rackel San Nicolas, Jannie S J Van Deventer, John L ProvisAbstract:An alkali-activated Slag Cement produced with a blend of sodium carbonate/sodium silicate activator was characterised. This binder hardened within 12 h and achieved a compressive strength of 20 MPa after 24 h of curing under ambient conditions, which is associated with the formation of an aluminium substituted calcium silicate hydrate as the main reaction product. Carbonates including pirssonite, vaterite, aragonite and calcite were identified along with the zeolites hydroxysodalite and analcime at early times of reaction. The partial substitution of sodium carbonate by sodium silicate reduces the concentration of carbonate ions in the pore solution, increasing the alkalinity of the system compared with a solely carbonate-activated paste, accelerating the kinetics of reaction and supplying additional silicate species to react with the calcium dissolving from the Slag as the reaction proceeds. These results demonstrate that this blend of activators can be used effectively for the production of high-strengt...
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structural evolution of an alkali sulfate activated Slag Cement
Journal of Nuclear Materials, 2016Co-Authors: Neda Mobashe, Susa A Ernal, John L ProvisAbstract:Abstract In this study, the effect of sodium sulfate content and curing duration (from fresh paste up to 18 months) on the binder structure of sodium sulfate activated Slag Cements was evaluated. Isothermal calorimetry results showed an induction period spanning the first three days after mixing, followed by an acceleration-deceleration peak corresponding to the formation of bulk reaction products. Ettringite, a calcium aluminium silicate hydrate (C-A-S-H) phase, and a hydrotalcite-like Mg–Al layered double hydroxide have been identified as the main reaction products, independent of the Na 2 SO 4 dose. No changes in the phase assemblage were detected in the samples with curing from 1 month up to 18 months, indicating a stable binder structure. The most significant changes upon curing at advanced ages observed were growth of the AFt phase and an increase in silicate chain length in the C-A-S-H, resulting in higher strength.
Lucas Auer - One of the best experts on this subject based on the ideXlab platform.
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innovative approach to simulating the biodeterioration of industrial Cementitious products in sewer environment part ii validation on cac and bfsc linings
Cement and Concrete Research, 2016Co-Authors: Matthieu Peyre Lavigne, Alexandra Bertron, Lucas Auer, Catherine BotanchAbstract:Abstract The development of a new test method for evaluating the resistance of manufactured Cementitious products to biogenic acid attack, labeled BAC-Test for Biogenic Acid Concrete Test, was reported in Part I of this paper. The performance of the test in terms of sulfur-oxidizing bacteria selection and acid and sulfate production has been validated previously. In this second part, the representativeness of the degradation mechanisms of the Cementitious materials is explored. Two segments of industrial pipes – ductile cast iron coated with Cementitious linings (blast furnace Slag Cement (BFSC) and calcium aluminate Cement (CAC) mortars) – were exposed to the test for 107 days. Then linings were analyzed by SEM coupled with EDS, EPMA, and XRD. Significant differences between BFSC and CAC linings were highlighted. Abundant cracking of the BFSC lining was observed, caused by precipitation of secondary ettringite, while no cracking was observed in the CAC lining. The CAC outer layer was composed mainly of AH 3 gel. The decalcification front was deeper in the BFSC matrix than in the CAC one.
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an innovative approach to reproduce the biodeterioration of industrial Cementitious products in a sewer environment part i test design
Cement and Concrete Research, 2015Co-Authors: Matthieu Peyre Lavigne, Alexandra Bertron, Lucas Auer, Guillermina HernandezraquetAbstract:A test method to evaluate biogenic resistance of Cementitious pipe products intended for sewer networks is presented. It consisted in inoculating pipes with a highly diverse microbial consortium (urban wastewater treatment plant), and trickling a feeding solution containing a safe and soluble reduced sulfur source, thiosulfate, over the inoculated surface in order to select a sulfur-oxidizing activity. Thiosulfate was used in the form of an aqueous solution, which facilitated the monitoring of (i) the bacterial activity by sulfur mass balances in the liquid phase, and thus quantification of acid production, and of (ii) the leaching of Cementitious ions. Cement-based linings made of (i) blast furnace Slag Cement and (ii) calcium aluminates Cement were tested. Results showed the selection of sulfur-oxidizing bacteria and the production of biogenic acid. Differences were shown between the linings in terms of Ca and Al dissolution. Biomass characterization highlighted the influence of the lining composition on colonization.
Matthieu Peyre Lavigne - One of the best experts on this subject based on the ideXlab platform.
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innovative approach to simulating the biodeterioration of industrial Cementitious products in sewer environment part ii validation on cac and bfsc linings
Cement and Concrete Research, 2016Co-Authors: Matthieu Peyre Lavigne, Alexandra Bertron, Lucas Auer, Catherine BotanchAbstract:Abstract The development of a new test method for evaluating the resistance of manufactured Cementitious products to biogenic acid attack, labeled BAC-Test for Biogenic Acid Concrete Test, was reported in Part I of this paper. The performance of the test in terms of sulfur-oxidizing bacteria selection and acid and sulfate production has been validated previously. In this second part, the representativeness of the degradation mechanisms of the Cementitious materials is explored. Two segments of industrial pipes – ductile cast iron coated with Cementitious linings (blast furnace Slag Cement (BFSC) and calcium aluminate Cement (CAC) mortars) – were exposed to the test for 107 days. Then linings were analyzed by SEM coupled with EDS, EPMA, and XRD. Significant differences between BFSC and CAC linings were highlighted. Abundant cracking of the BFSC lining was observed, caused by precipitation of secondary ettringite, while no cracking was observed in the CAC lining. The CAC outer layer was composed mainly of AH 3 gel. The decalcification front was deeper in the BFSC matrix than in the CAC one.
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an innovative approach to reproduce the biodeterioration of industrial Cementitious products in a sewer environment part i test design
Cement and Concrete Research, 2015Co-Authors: Matthieu Peyre Lavigne, Alexandra Bertron, Lucas Auer, Guillermina HernandezraquetAbstract:A test method to evaluate biogenic resistance of Cementitious pipe products intended for sewer networks is presented. It consisted in inoculating pipes with a highly diverse microbial consortium (urban wastewater treatment plant), and trickling a feeding solution containing a safe and soluble reduced sulfur source, thiosulfate, over the inoculated surface in order to select a sulfur-oxidizing activity. Thiosulfate was used in the form of an aqueous solution, which facilitated the monitoring of (i) the bacterial activity by sulfur mass balances in the liquid phase, and thus quantification of acid production, and of (ii) the leaching of Cementitious ions. Cement-based linings made of (i) blast furnace Slag Cement and (ii) calcium aluminates Cement were tested. Results showed the selection of sulfur-oxidizing bacteria and the production of biogenic acid. Differences were shown between the linings in terms of Ca and Al dissolution. Biomass characterization highlighted the influence of the lining composition on colonization.
Miguel Angel Climent - One of the best experts on this subject based on the ideXlab platform.
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performance of sustainable fly ash and Slag Cement mortars exposed to simulated and real in situ mediterranean conditions along 90 warm season days
Materials, 2017Co-Authors: José Marcos Ortega, María Dolores Esteban, Isidro Sanchez, Miguel Angel ClimentAbstract:Nowadays, Cement manufacture is one of the most polluting worldwide industrial sectors. In order to reduce its CO2 emissions, the clinker replaCement by ground granulated blast–furnace Slag and fly ash is becoming increasingly common. Both additions are well-studied when the hardening conditions of Cementitious materials are optimum. Therefore, the main objective of this research was to study the short-term effects of exposure, to both laboratory simulated and real in situ Mediterranean climate environments, on the microstructure and durability-related properties of mortars made using commercial Slag and fly ash Cements, as well as ordinary Portland Cement. The real in situ condition consisted of placing the samples at approximately 100 m away from the Mediterranean Sea. The microstructure was analysed using mercury intrusion porosimetry. The effective porosity, the capillary suction coefficient and the non-steady state chloride migration coefficient were also studied. In view of the results obtained, the non-optimum laboratory simulated Mediterranean environment was a good approach to the real in situ one. Finally, mortars prepared using sustainable Cements with Slag and fly ash exposed to both Mediterranean climate environments, showed adequate service properties in the short-term (90 days), similar to or even better than those in mortars made with ordinary Portland Cement.
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durability related transport properties of opc and Slag Cement mortars hardened under different environmental conditions
Construction and Building Materials, 2012Co-Authors: José Marcos Ortega, Isidro Sanchez, Miguel Angel ClimentAbstract:Abstract In this work, the durability performances of mortars made with an ordinary Portland Cement and a Slag Cement, were tested. These mortars were exposed to four different constant temperature and relative humidity during 365 days. The measured properties of both Cement types are affected by the environment, but the durability of Slag Cement mortars is more influenced by temperature and the durability of OPC mortars is more influenced by the relative humidity. The obtained results show that the Slag Cement mortars hardened under non-optimal environmental conditions have good durability at any hardening age, even better than Portland Cement.
Guillermina Hernandezraquet - One of the best experts on this subject based on the ideXlab platform.
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an innovative approach to reproduce the biodeterioration of industrial Cementitious products in a sewer environment part i test design
Cement and Concrete Research, 2015Co-Authors: Matthieu Peyre Lavigne, Alexandra Bertron, Lucas Auer, Guillermina HernandezraquetAbstract:A test method to evaluate biogenic resistance of Cementitious pipe products intended for sewer networks is presented. It consisted in inoculating pipes with a highly diverse microbial consortium (urban wastewater treatment plant), and trickling a feeding solution containing a safe and soluble reduced sulfur source, thiosulfate, over the inoculated surface in order to select a sulfur-oxidizing activity. Thiosulfate was used in the form of an aqueous solution, which facilitated the monitoring of (i) the bacterial activity by sulfur mass balances in the liquid phase, and thus quantification of acid production, and of (ii) the leaching of Cementitious ions. Cement-based linings made of (i) blast furnace Slag Cement and (ii) calcium aluminates Cement were tested. Results showed the selection of sulfur-oxidizing bacteria and the production of biogenic acid. Differences were shown between the linings in terms of Ca and Al dissolution. Biomass characterization highlighted the influence of the lining composition on colonization.
