Microstructure studies on Portland cement pastes obtained in highly alkaline environments

Martínez-Ramírez, S.; Palomo, A.

doi:10.1016/s0008-8846(01)00603-2

Cited by 41 publications

(21 citation statements)

References 4 publications

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“…However, compressive strength is inversely proportional to the concentration of NaOH at 10-14 M. This could be due to the presence of excess hydroxide ion concentration [25] and excess Na + ions in the framework [22,26], which precipitates aluminosilicate gel during the early stages of the reaction, thus preventing geopolymerization, culminating in lower compressive strengths. The higher the alkalinity of the hydration water, the slower the rate of the hydration [27].…”

Section: Curing Time Effectmentioning

confidence: 99%

Development of Green Geopolymer Using Agricultural and Industrial Waste Materials with High Water Absorbency

et al. 2017

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Abstract:Geopolymer is a promising porous material that can be used for evaporative cooling applications. Developing a greener geopolymer using agricultural and industrial wastes is a promising research area. In this study, we utilize rice husk (RH), rice husk ash (RHA), metakaolin (MK), ground granulated blast furnace slag (GGBS), and palm oil fuel ash (POFA) to prepare geopolymer pastes, with alkali liquid as an activator. Many geopolymer samples have been prepared as per the Design of Experimental software (DOE), and its corresponding response surface mode and central composite design and later they were characterized. The samples were cured in an oven for 2 h at 80 • C, and thereafter stored at room temperature (~25-30 • C) prior to being tested for its water absorption and compressive strength. The effect of the different composition of precursors on water absorption, density, porosity, and the compressive strength of the prepared geopolymers have been investigated. The results showed that the compressive strength of geopolymers is directly proportional to the ratio of the alkali liquid. Post-optimization, the best geopolymer paste mixture was confirmed to contain 10% of RH, 15% RHA, 35% MK, 10% POFA and 30% of GGBS, with 72% desirability for maximum water absorption (~38%) and compressive strength (4.9 MPa). The results confirmed its applicability for evaporative cooling.

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Section: Curing Time Effectmentioning

confidence: 99%

Development of Green Geopolymer Using Agricultural and Industrial Waste Materials with High Water Absorbency

et al. 2017

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“…Sustainability 2017, 9, 852 9 of 13 365 days, the values of compressive strengths reached about 11 MPa in both the samples. The lower values of compressive strength of SRM2 and SRM4 mixtures compared to others indicate that the conversion degree to C-S-H gels in composite system is probably too low due to a higher OH − concentration in the system, that causes the shift of equilibrium towards the left side in the hydration process of C3S and C2S [45,47]. C-S-H gels can be formed from precipitated Ca(OH)2 at pH around 12.4 [56].…”

Section: Sediment As a Bindermentioning

confidence: 74%

“…This activator was chosen based on the previous studies [43][44][45][46], which concluded that the inclusion of NaOH as chemical activator into geopolymer matrix increased the compressive strength of the hardened geopolymer concrete. Alkali activators transform the amorphous structure into a skeletal structure that exhibits cementitious properties [47]. Polymeric gel with variable composition is formed in the media of high alkalinity.…”

Section: Preparation Of the Mixturesmentioning

confidence: 99%

“…However, the addition of NaOH caused a higher pH of the fresh mixture (around 13.8) and retarded the process of mixture hydration [57,58]. According to Martinez-Ramirez and Palomo [47] as the alkaline concentration of the hydrating solution increases, the degree of hydration of anhydrous silicates reduces, and for this reason, the compressive strength also gets reduced. The comparison of the compressive strength development for composites with and without NaOH addition (SRM2 vs. SRM1 and SRM4 vs. SRM3) confirm this fact.…”

Section: Sediment As a Bindermentioning

confidence: 99%

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Sustainable Use of Reservoir Sediment through Partial Application in Building Material

Junáková

Junak

2017

Sustainability

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Sediment, often considered a by-product of various activities within river basin management to be disposed of, or a pollutant to be controlled, is increasingly being acknowledged as a resource in need of management. The paper deals with the possibility of reusing sediment from two Slovak reservoirs (Klusov and Ruzin) as an alternative raw material in concrete production. Concrete specimens were prepared by a combination of original reservoir sediment, reservoir sediment mechanically activated by dry milling, reservoir sediment mechanically activated by dry milling together with biomass incinerator fly-ash as a binder. To improve the strength properties of specimens, sodium hydroxide (NaOH) was used as a sediment activator. Mixtures containing 40% of binder replacement by the above-mentioned combinations of original and treated sediments were tested for flexural and compressive strengths after 28, 90 and 365 days of curing. The results showed that the mixtures prepared from sediments milled without and with addition of fly ash as cement replacement satisfied the strength requirements for the compressive strength class C16/20 according to the European standard except the composites prepared with NaOH as the sediment activator. Addition of NaOH into composites in the concentration of 5 M as an activator of sediment indicated the negative impact on compressive and flexural strengths and thus NaOH was not an effective pozzolanic activator for sediments. This study reveals that the sediment may be considered as 40% cement substitution in building materials.

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“…However, significantly lower compression strengths of SRM2 and SRM4-SRM6 composites compared to others indicate that the conversion degree to the C-S-H gels in the composite system is too low due to the high concentration of hydroxyl ions in the system (pH of fresh blended mixtures were 13.8). This causes the shift of equilibrium towards the left side in the hydration process of C 3 S and C 2 S [26][27].…”

Section: Resultsmentioning

confidence: 99%

The effect of sediment treatment on strength and water absorption capacity of sediment based concrete

Junáková

Junak

2018

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract. The paper presents the possibility of the Ružín (Slovakia) reservoir sediments' reuse as a 40% replacement of Portland cement in concrete. Treatment of sediments consists of sediment dry milling, adding of fly ash from local biomass incinerator plant into the dry milling process due to the low CaO sediment content and sediment's mechano-chemical activation using sodium hydroxide in the form of solid and solution as a chemical activator of pozzolanic properties. The results show the possibility of sediment reuse in building materials. However, treatment of sediments with the addition of fly ash doesn't significantly affect the development of compressive strength. Sodium hydroxide is not an effective pozzolanic activator for sediments. The absorptivity of composites increases with the fly ash and sodium hydroxide addition. Also the NaOH application form (as a solid or solution) influences the total absorption water capacity. Pouring the mixture with 5M NaOH increases the absorptivity of the hardened composites.

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Microstructure studies on Portland cement pastes obtained in highly alkaline environments

Cited by 41 publications

References 4 publications

Development of Green Geopolymer Using Agricultural and Industrial Waste Materials with High Water Absorbency

Development of Green Geopolymer Using Agricultural and Industrial Waste Materials with High Water Absorbency

Sustainable Use of Reservoir Sediment through Partial Application in Building Material

The effect of sediment treatment on strength and water absorption capacity of sediment based concrete

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