Fresh Properties and Early Compressive Strength of Alkali-Activated High Calcium Fly Ash Paste

Gomaa, Eslam; Sargon, Simon; Kashosi, Cedric; ElGawady, Mohamed A.

doi:10.1007/978-981-10-6713-6_49

Cited by 4 publications

(5 citation statements)

References 19 publications

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“…As observed, the addition of µ-limestone could undoubtedly modify the mechanical responses of slag-based alkali-activated binders. As communicated in the literature, the mechanisms promoted by limestone that are favorable to the resistance development of slag-based paste are: (i) producing nucleation sites [ 69 , 70 , 71 ], (ii) increasing slag dissolution [ 72 , 73 , 74 ], (iii) improving pore refinement [ 69 , 71 , 72 , 75 , 76 ], (iv) reaching higher packing density [ 70 ], (v) enhancing reaction degree [ 73 , 75 ], and (vi) gel products’ intensification [ 73 ]. As was shown, the slag-based alkali-activated pastes exhibited compressive resistance higher than that of fly ash-based alkali-activated pastes provided by the C-A-S-H- or C-S-H-type gels [ 77 , 78 ].…”

Section: Resultsmentioning

confidence: 99%

“…The acceleration and intensification of reaction in slag-based alkali-activated pastes responds to the action of µ-limestone grains acting as nucleation sites that induce the formation of reaction products [ 69 , 70 , 73 , 74 ]. The nucleation sites ease the precipitation and increment of reaction products, meaning that limestone can add apparent physical modifications and minor chemical effects.…”

Section: Resultsmentioning

confidence: 99%

“…The acceleration and intensification of reaction in slag-based alkali-activated pastes responds to the action of µ-limestone grains acting as nucleation sites that induce the formation of reaction products [69,70,73,74]. The nucleation sites ease the precipitation and In addition, there was a tendency where µ-limestone added to the pastes accelerated the reactions at 7 days, reaching early mechanical strength increments similar to those attained at 28 days.…”

Section: Summary Discussion Of Limestone's Effect On Mechanical Prope...mentioning

confidence: 99%

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Microstructural and Mechanical Characteristics of Alkali-Activated Binders Composed of Milled Fly Ash and Granulated Blast Furnace Slag with µ-Limestone Addition

Vázquez-Rodríguez,

Elizondo,

Montes-González

et al. 2023

Materials

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Concrete is the most used construction material, needing large quantities of Portland cement. Unfortunately, Ordinary Portland Cement production is one of the main generators of CO2, which pollutes the atmosphere. Today, geopolymers are an emerging building material generated by the chemical activity of inorganic molecules without the Portland Cement addition. The most common alternative cementitious agents used in the cement industry are blast-furnace slag and fly ash. In the present work, the effect of 5 wt.% µ-limestone in mixtures of granulated blast-furnace slag and fly ash activated with sodium hydroxide (NaOH) at different concentrations was studied to evaluate the physical properties in the fresh and hardened states. The effect of µ-limestone was explored through XRD, SEM-EDS, atomic absorption, etc. The addition of µ-limestone increased the compressive strength reported values from 20 to 45 MPa at 28 days. It was found by atomic absorption that the CaCO3 of the μ-limestone dissolved in NaOH, precipitating Ca(OH)2 as the reaction product. SEM-EDS analysis showed a chemical interaction between C-A-S-H- and N-A-S-H-type gels with Ca(OH)2, forming (N, C)A-S-H- and C-(N)-A-S-H-type gels, improving mechanical performance and microstructural properties. The addition of μ-limestone appeared like a promising and cheap alternative for enhancing the properties of low-molarity alkaline cement since it helped exceed the 20 MPa strength recommended by current regulations for conventional cement.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

“…The acceleration and intensification of reaction in slag-based alkali-activated pastes responds to the action of µ-limestone grains acting as nucleation sites that induce the formation of reaction products [69,70,73,74]. The nucleation sites ease the precipitation and In addition, there was a tendency where µ-limestone added to the pastes accelerated the reactions at 7 days, reaching early mechanical strength increments similar to those attained at 28 days.…”

Section: Summary Discussion Of Limestone's Effect On Mechanical Prope...mentioning

confidence: 99%

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Microstructural and Mechanical Characteristics of Alkali-Activated Binders Composed of Milled Fly Ash and Granulated Blast Furnace Slag with µ-Limestone Addition

Vázquez-Rodríguez,

Elizondo,

Montes-González

et al. 2023

Materials

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“…The water used to calculate the W/FA included both water in the alkaline activators and the extra water added during the mixing. The range of W/FA was selected to present a range of relatively stiff and flowable AAMs for different applications, and the Alk/FA and SS/SH ranges were selected as they displayed acceptable setting times and compressive strengths for AAM (44)(45)(46).…”

Section: Materials Propertiesmentioning

confidence: 99%

“…Increasing the Alk/FA from 0.250 to 0.300 increased the compressive strength of the tested specimens from 19.4 to 34.7 MPa. This trend was caused by increasing the alkali activators, which increased the solubility of the silica, alumina, and the Na 2 O and SiO 2 content which resulted in a higher rate of geopolymerization (i.e., better reactivity), resulting in denser microstructure and subsequently higher compressive strength (25,44,46,54,(62)(63)(64).…”

Section: Effect Of the Loading Direction On The Compressive Strengthmentioning

confidence: 99%

Developing Mix Proportions for Class C Fly Ash-Based Alkali-Activated 3D-Printed Concrete Mixtures

Abudawaba

Gomaa

Gheni

et al. 2021

Transportation Research Record

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This study investigated the use of class C fly ash (FA) as a precursor for alkali-activated mortar (AAM) for 3D-printed concrete (3DPC). AAMs with different water-to-FA (W/FA), alkaline activator-to-FA (Alk/FA), and sodium silicate-to-sodium hydroxide (SS/SH) ratios were examined to develop mixtures that can be tailored for different structural applications of 3DPC. The fresh properties, including extrudability and buildability, were evaluated through the open time (OT) and immediate deformation tests, respectively. Different cycle times (CTs) were applied to achieve a strain limit state necessary to maintain the printed shape. The strength of AAMs in different directions at different CTs was examined. Scanning electron microscopy (SEM) was carried out on AAM specimens having different CTs for a better understanding of the bond area. OTs ranging from 2.5 min to 31 min and axial strains ranging from 0.17% to 11.2% were achieved depending on the proportions of the AAMs and CT, which offers flexibility in optimizing the speed of printing and strength of concrete for different projects. The 3DPC specimens displayed anisotropic behavior compared with full-height specimens, where the compressive strength of full-height specimens was higher by 0.2% to 18% and 0.9% to 28% than 3DPC specimens when tested parallel and normal to the printing directions, respectively. SEM images and line scan indicated an approximately even intensity of the element concentration at the interfacial zones of AAMs having short CTs, which explained the relatively high compressive strength of those specimens. For AAMs having long CTs, there was a significant change in the intensity of the element concentration at the interfacial bond zone, and voids were observed resulting in low compressive strength of those specimens.

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Properties of high-calcium fly ash-based geopolymer concretes improved with high-silica sources

Sevinç

Durgun

2020

Construction and Building Materials

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Fresh Properties and Early Compressive Strength of Alkali-Activated High Calcium Fly Ash Paste

Cited by 4 publications

References 19 publications

Microstructural and Mechanical Characteristics of Alkali-Activated Binders Composed of Milled Fly Ash and Granulated Blast Furnace Slag with µ-Limestone Addition

Microstructural and Mechanical Characteristics of Alkali-Activated Binders Composed of Milled Fly Ash and Granulated Blast Furnace Slag with µ-Limestone Addition

Developing Mix Proportions for Class C Fly Ash-Based Alkali-Activated 3D-Printed Concrete Mixtures

Properties of high-calcium fly ash-based geopolymer concretes improved with high-silica sources

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