Multiscale micromechanical analysis of alkali-activated fly ash-slag paste

Fang, Guohao; Zhang, Mingzhong

doi:10.1016/j.cemconres.2020.106141

Cited by 128 publications

(30 citation statements)

References 100 publications

(191 reference statements)

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“…MPa, which was increased by 132.1% and 155.8% at 7 and 28 d, respectively. With the increase of PVA fibre content from 1.5 vol% to 2 vol%, the compressive strength of SHGC was improved by 34.7% at 1 d but slightly reduced by 9.7% and 7.3% at 7 and 28 d. The increase of compressive strength with increasing fibre content at early age can be ascribed to the more energy of fracture required to pull fibres out[70]. However, this effect could be altered by the inadequate compaction of SHGC specimens, leading to an increase of porosity and decrease of strength.…”

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confidence: 93%

“…displays the effect of hybrid fibre content on compressive strength of SHGC at 1, 7 and 28 d. In general, the compressive strength of all mixtures increased gradually with increasing curing age due to the geopolymerisation process. SHGC containing 1.5 vol% PVA fibre had a 1-d compressive strength of 13.1 attributed to the high stiffness and hydrophilicity nature of RTS fibre, which can absorb more energy and provide strong fibre-matrix interaction[24,66,70].Regarding the hybrid fibre system of SHGC specimens, the partial RTS fibre replacement of PVA fibre showed various effects on compressive strength at different ages. At the early ages (1 and 7 d), the replacement level of RTS fibre had a marginal effect on compressive strength of SHGC specimens,whereas a clear trend at 28 d indicated that the compressive strength increased with the replacement of RTS fibre.…”

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confidence: 99%

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Engineering properties of strain hardening geopolymer composites with hybrid polyvinyl alcohol and recycled steel fibres

Wang

Chan

Leong

et al. 2020

Construction and Building Materials

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Strain hardening geopolymer composite (SHGC) is an alkali-activated material reinforced with randomly dispersed short fibres, which exhibits high ductility and strain hardening and multiple cracking behaviour. This paper presents an experimental study on the effect of hybrid polyvinyl alcohol (PVA) and recycled tyre steel (RTS) fibres on engineering properties of fly ash-slag based SHGC cured at ambient temperature, including flowability, setting time, drying shrinkage, compressive strength and flexural behaviour in terms of stress-deflection response, first-crack strength and flexural strength, flexural toughness and toughening mechanisms. Four mix proportions of specimens with various volume fractions of hybrid PVA and RTS fibres including 1.5% PVA, 2% PVA, 1.75% PVA + 0.25% RTS and 1.5% PVA + 0.5% RTS were considered. The results indicated that the hybridisation of PVA fibre with RTS fibre led to a significant reduction in flowability, setting time and flexural strength of SHGC. However, the resistance to drying shrinkage and compressive strength of SHGC were greatly improved. Moreover, all specimens exhibited the expected deflection hardening behaviour with multiple stable microcracks formed over the tensile face of specimens under four-point bending. The addition of RTS fibre resulted in reduced crack widths in specimens where over 90% of cracks had a width of smaller than 60 μm. The mixture containing 2.0 vol% PVA fibre can be regarded as the optimal mixture for SHGC considering the strengths and deflection (or strain) hardening behaviour.

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confidence: 93%

mentioning

confidence: 99%

Engineering properties of strain hardening geopolymer composites with hybrid polyvinyl alcohol and recycled steel fibres

Wang

Chan

Leong

et al. 2020

Construction and Building Materials

Self Cite

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“…The wide, low-resolution signals in the right-side area of the spectrum were due primarily to unreacted FA. Q 4 (mAl) (m = 4, 3, 2, 1 or 0) units also found in this zone were attributed to Ca 2 + -low N-A-S-H and (N,C)-A-S-H gels (N-(C)-A-S-H-like gels) [98,102,103], characterized by a highly polymerized aluminosilicate structure in which Si and Al were tetrahedrally coordinated. The signals at around −93 ppm were associated with Q 4 (3Al) signals generated by N-A-S-H gels with reactive and highly polymerized aluminate phases.…”

Section: Samplementioning

confidence: 64%

“…The Q 4 (2Al) units located at around −97 ppm and Q 4 (1Al) units at around −103 ppm were the most stable Si-high N-A-S-H sites. The signals at −105 ppm and −116 ppm were attributed to Q 4 (0Al) units associated with the presence of the crystalline quartz phases in fly ash [86,102,104].…”

Section: Samplementioning

confidence: 99%

Hybrid Cements: Mechanical Properties, Microstructure and Radiological Behavior

et al. 2022

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The use of more eco-efficient cements in concretes is one of the keys to ensuring construction industry sustainability. Such eco-efficient binders often contain large but variable proportions of industrial waste or by-products in their composition, many of which may be naturally occurring radioactive materials (NORMs). This study explored the application of a new gamma spectrometric method for measuring radionuclide activity in hybrid alkali-activated cements from solid 5 cm cubic specimens rather than powder samples. The research involved assessing the effect of significant variables such as the nature of the alkaline activator, reaction time and curing conditions to relate the microstructures identified to the radiological behavior observed. The findings showed that varying the inputs generated pastes with similar reaction products (C-S-H, C-A-S-H and (N,C)-A-S-H) but different microstructures. The new gamma spectrometric method for measuring radioactivity in solid 5 cm cubic specimens in alkaline pastes was found to be valid. The variables involved in hybrid cement activation were shown to have no impact on specimen radioactive content. The powder samples, however, emanated 222Rn (a descendent of 226Ra), possibly due to the deformation taking place in fly ash structure during alkaline activation. Further research would be required to explain that finding.

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“…The soluble silicates in the activator seem to restrict the moisture transportation in the pore structure. The geopolymers activated with sodium silicate generally have more compact pore structures than the geopolymers activated with sodium hydroxide [17][18][19]. This is helpful in slowing down the movement of free alkalis in the matrix.…”

Section: Testing and Characterizationmentioning

confidence: 99%

Relationship between Moisture Transportation, Efflorescence and Structure Degradation in Fly Ash/Slag Geopolymer

Zhou

Zhang

et al. 2020

Materials

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The relationship between moisture transportation and efflorescence in sodium hydroxide- or sodium silicate-activated fly ash/slag geopolymers was investigated. The results show that the efflorescence products are sodium carbonate hydrates, mainly composed of natron, heptahydrate, trona and sodium carbonate. The efflorescence induces compressive strength loss, water absorption increases and pore structure degradation in the geopolymer. When the curved surface of a geopolymer cylinder is covered with plastic film, the moisture transportation drives the free alkalis to the top surface to initiate efflorescence. In comparison, the efflorescence occurring on the curved surface of an uncovered geopolymer cylinder results in a more intensive alkalinity loss. For the uncovered geopolymers prepared with sodium hydroxide activator, efflorescence deposits are formed on the lower half of cylinder. A low capillary absorption capacity developed in the pore structure can only drive the moisture to the middle of cylinder, which is confronted with the drying front. More efflorescence products are formed on the upper half of the uncovered geopolymer cylinder prepared with sodium silicate activator. A relatively higher capillary absorption capacity, developed in the more compact pore structure, transports the moisture from the bottom to the top of cylinder, so no drying line is observed in the cylinder.

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Multiscale micromechanical analysis of alkali-activated fly ash-slag paste

Cited by 128 publications

References 100 publications

Engineering properties of strain hardening geopolymer composites with hybrid polyvinyl alcohol and recycled steel fibres

Engineering properties of strain hardening geopolymer composites with hybrid polyvinyl alcohol and recycled steel fibres

Hybrid Cements: Mechanical Properties, Microstructure and Radiological Behavior

Relationship between Moisture Transportation, Efflorescence and Structure Degradation in Fly Ash/Slag Geopolymer

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