The effect of silica availability on the mechanism of geopolymerisation

Hajimohammadi, Ailar; Provis, John L.; Deventer, J.S.J. van

doi:10.1016/j.cemconres.2011.02.001

Cited by 218 publications

(93 citation statements)

References 31 publications

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“…When N came to 2.25, there were significant difference with N = 1.75 or 2. After 3 d curing, the geopolymer gel has not completely solidified, which was attributed to the presence of massive potassium silicate [24]. There were many cracks in the samples surface with N = 2.25, which may be caused by the extrusion in the demoulding process.…”

Section: Characterizationmentioning

confidence: 97%

The Effect of Si/Al on Mechanical Properties and Fracture Behavior of Stainless Steel Mesh/Cr_pReinforced Geopolymer Composites

Yuan

Jia

2017

MATEC Web Conf.

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Abstract. In this study, a series stainless steel mesh/Cr p reinforced geopolymer composites with different Si/Al molar ratio (N) were designed and prepared, where N = 1.75, 2 and 2.25, respectively. The effect of Si/Al molar ratio in the geopolymer matrix on mechanical properties and fracture behavior of the geopolymer composites were investigated. The microstructure of geopolymer became more compact when Si/Al increased from 1.75 to 2, which was beneficial to the improvement of geopolymer's mechanical properties. And continuing to rise to 2.25 for Si/Al, the completely curing of geopolymer composites required more time compared with lower Si/Al, which can be attributed to the different microstructure and chemical composition caused by the different Si/Al. The optimum Si/Al molar ratio was about 2 at which the composites samples present the best mechanical properties with the flexure strength of 115.3 MPa and elastic modulus of 11.0 GPa, respectively. The results of fracture behavior suggested that geopolymer composites with N is 2.25 displayed the behavior characteristics of metal materials, which can be attributed to a poor integrated condition in interface between reinforcements and geopolymer matrix.

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Section: Characterizationmentioning

confidence: 97%

The Effect of Si/Al on Mechanical Properties and Fracture Behavior of Stainless Steel Mesh/Cr_pReinforced Geopolymer Composites

Yuan

Jia

2017

MATEC Web Conf.

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“…S3). The heterogeneous C-A-S-H compositions likely reflect availability of Al 3+ and Si 4+ at gel nucleation sites (34,35), as suggested by formation of calcium-silicate-hydrate (C-S-H) adjacent to relict opal particles and alumina-enriched C-A-S-H adjacent to scoriae perimeters (Table S4). By 90 d, when portlandite is entirely consumed (Fig.…”

Section: Development Of the Cementitious Fabricmentioning

confidence: 99%

Mechanical resilience and cementitious processes in Imperial Roman architectural mortar

Jackson¹,

Landis

Brune

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

178

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The pyroclastic aggregate concrete of Trajan's Markets (110 CE), now Museo Fori Imperiali in Rome, has absorbed energy from seismic ground shaking and long-term foundation settlement for nearly two millenia while remaining largely intact at the structural scale. The scientific basis of this exceptional service record is explored through computed tomography of fracture surfaces and synchroton X-ray microdiffraction analyses of a reproduction of the standardized hydrated lime-volcanic ash mortar that binds decimeter-sized tuff and brick aggregate in the conglomeratic concrete. The mortar reproduction gains fracture toughness over 180 d through progressive coalescence of calcium-aluminum-silicate-hydrate (C-A-S-H) cementing binder with Ca/(Si+Al) ≈ 0.8-0.9 and crystallization of strätlingite and siliceous hydrogarnet (katoite) at ≥90 d, after pozzolanic consumption of hydrated lime was complete. Platey strät-lingite crystals toughen interfacial zones along scoria perimeters and impede macroscale propagation of crack segments. In the 1,900-y-old mortar, C-A-S-H has low Ca/(Si+Al) ≈ 0.45-0.75. Dense clusters of 2-to 30-μm strätlingite plates further reinforce interfacial zones, the weakest link of modern cement-based concrete, and the cementitious matrix. These crystals formed during long-term autogeneous reaction of dissolved calcite from lime and the alkali-rich scoriae groundmass, clay mineral (halloysite), and zeolite (phillipsite and chabazite) surface textures from the Pozzolane Rosse pyroclastic flow, erupted from the nearby Alban Hills volcano. The clastsupported conglomeratic fabric of the concrete presents further resistance to fracture propagation at the structural scale.Roman concrete | volcanic ash mortar | fracture toughness | interfacial zone | strätlingite

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“…While a higher alkalinity (as indicated by a lower M s ) is beneficial at early times to aid in dissolution of the glassy species in slag as shown by the heat release curves shown in Fig. 2a, a higher silica content is ultimately necessary to form the strength imparting C-(A)-S-H gel in the alkaliactivated systems (Hajimohammadi et al 2011;Ravikumar and Neithalath 2012b). The alkali cations could also be incorporated into the C-(A)-S-H gel.…”

Section: Early Age Reaction Response and Compressive Strengthmentioning

confidence: 99%

“…NaOH) has been found to be ideal to produce desired mechanical properties (Fernández-Jiménez et al 1999;Chithiraputhiran and Neithalath 2013;Chang 2003;Altan and Erdogan 2012) even though alkali hydroxides, carbonates, and sulfates also have been reported to be used as activating agents (Shi et al 2006). The nature and type of the activating agent determines the reaction rate and extent, and the reaction products formed, thereby exerting a significant influence on the earlyand later-age properties of alkali-activated binder systems (Chithiraputhiran and Neithalath 2013;Ravikumar and Neithalath 2012a, b;Puertas et al 2004;Hajimohammadi et al 2011). The energy requirement towards the production of activators and the associated environmental impact also plays an important role in determining the sustainability of alkali-activated systems, along with their potential to replace large amounts of OPC.…”

Section: Introductionmentioning

confidence: 99%

Microstructural, Mechanical, and Durability Related Similarities in Concretes Based on OPC and Alkali-Activated Slag Binders

Vance

Aguayo

Dakhane

et al. 2014

Int J Concr Struct Mater

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Alkali-activated slag concretes are being extensively researched because of its potential sustainability-related benefits. For such concretes to be implemented in large scale concrete applications such as infrastructural and building elements, it is essential to understand its early and long-term performance characteristics vis-à-vis conventional ordinary portland cement (OPC) based concretes. This paper presents a comprehensive study of the property and performance features including early-age isothermal calorimetric response, compressive strength development with time, microstructural features such as the pore volume and representative pore size, and accelerated chloride transport resistance of OPC and alkali-activated binder systems. Slag mixtures activated using sodium silicate solution (SiO 2 -to-Na 2 O ratio or M s of 1-2) to provide a total alkalinity of 0.05 (Na 2 O-tobinder ratio) are compared with OPC mixtures with and without partial cement replacement with Class F fly ash (20 % by mass) or silica fume (6 % by mass). Major similarities are noted between these binder systems for: (1) calorimetric response with respect to the presence of features even though the locations and peaks vary based on M s , (2) compressive strength and its development, (3) total porosity and pore size, and (4) rapid chloride permeability and non-steady state migration coefficients. Moreover, electrical impedance based circuit models are used to bring out the microstructural features (resistance of the connected pores, and capacitances of the solid phase and pore-solid interface) that are similar in conventional OPC and alkali-activated slag concretes. This study thus demonstrates that performance-equivalent alkali-activated slag systems that are more sustainable from energy and environmental standpoints can be proportioned.

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The effect of silica availability on the mechanism of geopolymerisation

Cited by 218 publications

References 31 publications

The Effect of Si/Al on Mechanical Properties and Fracture Behavior of Stainless Steel Mesh/Cr_pReinforced Geopolymer Composites

The Effect of Si/Al on Mechanical Properties and Fracture Behavior of Stainless Steel Mesh/Cr_pReinforced Geopolymer Composites

Mechanical resilience and cementitious processes in Imperial Roman architectural mortar

Microstructural, Mechanical, and Durability Related Similarities in Concretes Based on OPC and Alkali-Activated Slag Binders

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The effect of silica availability on the mechanism of geopolymerisation

Cited by 218 publications

References 31 publications

The Effect of Si/Al on Mechanical Properties and Fracture Behavior of Stainless Steel Mesh/CrpReinforced Geopolymer Composites

The Effect of Si/Al on Mechanical Properties and Fracture Behavior of Stainless Steel Mesh/CrpReinforced Geopolymer Composites

Mechanical resilience and cementitious processes in Imperial Roman architectural mortar

Microstructural, Mechanical, and Durability Related Similarities in Concretes Based on OPC and Alkali-Activated Slag Binders

Contact Info

Product

Resources

About

The Effect of Si/Al on Mechanical Properties and Fracture Behavior of Stainless Steel Mesh/Cr_pReinforced Geopolymer Composites

The Effect of Si/Al on Mechanical Properties and Fracture Behavior of Stainless Steel Mesh/Cr_pReinforced Geopolymer Composites