Response of alkali activated fly ash mortars to microwave curing

Somaratna, Jeevaka; Ravikumar, Deepak; Neithalath, Narayanan

doi:10.1016/j.cemconres.2010.08.010

Cited by 89 publications

(30 citation statements)

References 32 publications

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“…Kafry (1993) [15] explains that DEC induces an inverted temperature gradient unlike conventional accelerated curing techniques, and Heritage (2001) [20] observed that with DEC, the maximum temperature during curing is always in the central region of the mixture. With microwave curing, Somaratna et al (2010) [16] also observed an inverse temperature gradient; the highest temperature was observed to be in the centre of the mixture. They explain that the inverted temperature gradient is due to the temperature differential between the mixture and the microwave cavity; this introduces convective and radiative heat loss between the exposed surface of the mixture and the microwave cavity.…”

Section: Other Observationmentioning

confidence: 92%

“…However, mixtures prepared with microwave curing are also prone to thermally induced cracks at high heating rates. Somaratna et al (2010) [16] observed severe cracking and deterioration within a few minutes of alkali-activated fly ash mixtures subjected to too high power levels of microwave curing. Davidovits and Legrand (1977) [17] shows that rapid hardening of a mixture in a matter of minutes is possible.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Confined-Direct Electric Curing of NaOH-activated fly ash based brick mixtures under free drainage conditions: Part 1. Factorial experimental design

Ziolkowski

2017

Construction and Building Materials

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The utilisation of fly ash is a global concern. Under conditions of mass production and rapid turnover in automated plants, a reduction in the curing duration of alkali-activated fly ash based mixtures is sought-after. An alternative accelerated curing technique, confined-DEC (Direct Electric Curing), with the binding mechanism of NaOH activation of fly ash was investigated for the rapid manufacture of fly ash based bricks. This concept is a potentially viable alternative solution for high-volume fly ash utilisation. The investigation revealed that the confined-DEC technique shows great promise in the rapid accelerated curing of NaOH-activated fly ash based brick mixtures. The best induced design conditions, a mixture consisting of 4.1% NaOH, 9% water and 86.9% fly ash by weight, simultaneously subjected to a confining pressure of 10 MPa and a voltage gradient of 0.8 V/mm, obtained a compressive strength of 11.5 MPa in 7 minutes and the mixture continued to increase in compressive strength after the application of confined-DEC, acquiring a compressive strength *Revised Manuscript of 20.1 MPa at 28 days. The investigation also revealed the limitations of confined-DEC under free drainage conditions.

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Section: Other Observationmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Confined-Direct Electric Curing of NaOH-activated fly ash based brick mixtures under free drainage conditions: Part 1. Factorial experimental design

Ziolkowski

2017

Construction and Building Materials

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“…Furthermore, in both thermal oven and microwave curing, a 24-hour room temperature pre-curing regime was adopted, which will not only reduce slurry splashing in microwave curing (Somaratna et al, 2010), but would also enhance the dissolution of silica and alumina from fly ash, leading to better activation (Bakharev, 2005b). The pre-cured samples were cured within steel moulds under room temperature for 24 hours before being exposed to the thermal oven curing up to 24 hours.…”

Section: Preparation Of Samplesmentioning

confidence: 99%

“…The only study reported in the literature was carried out by Somaratna et al (Somaratna et al, 2010) on curing AAFA mortars (5×5×5cm) with a domestic oven. With a delay time of 12 hours, the mortars were cured with different curing durations at varying percentages of full power level.…”

Section: Introductionmentioning

confidence: 99%

Comparative Study of Alkali-Activated Fly Ash Manufactured Under Pulsed Microwave Curing and Thermal Oven Curing

Shi¹,

Bai²,

Li³

et al. 2014

Proceedings of the 4th International Conference on the Durability of Concrete Structures

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This paper compares the alkali-activated fly ash (AAFA) manufactured with thermal oven curing and pulsed microwave curing methods. Fly ash activated by 8M NaOH solution at a liquid to solid ratio of 0.3 was cured by thermal oven at 85°C and domestic microwave oven, respectively. Apart from compressive strength test, the temperature profiles of AAFA samples were captured by thermal camera. Reaction products of AAFA were characterised with XRD, FTIR and TG/DTG, while the microstructure of AAFA was analysed by MIP and SEM. The results showed that with much shorter curing duration, the compressive strength of AAFA samples under microwave curing was comparable to those samples under thermal oven curing. The XRD results demonstrated that different reaction products were generated from thermal oven curing (hydroxysodalite) and microwave curing (chabazite-Na) respectively. The FTIR spectra showed that aluminosilicate with higher degree of polymerization was formed in the sample with microwave curing. MIP indicated equivalent total porosities from both curing methods, while a well-distributed matrix phase under thermal oven curing were found in the SEM results. Overall, the results demonstrate that microwave curing has great potential to be an alternative curing method for manufacturing AAFA.

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“…Although energy sources like microwave and solar radiation have been used for curing AAFA cements and mortars. Somaratna et al (2010) showed that volumetric heating provided by microwave curing results in faster property development of NaOH activated fly ash mortars as compared to conventional heat curing. Chindaprasirt et al (2013) also confirmed that short microwave curing accelerates reaction in AAFA cement resulting in improved compressive strength.…”

Section: Introductionmentioning

confidence: 99%

Direct electric curing of alkali-activated fly ash concretes: a tool for wider utilization of fly ashes

Kovtun

Shekhovtsova

Kearsley

2016

Journal of Cleaner Production

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Utilization of the fly ashes is a major problem in many developing countries and in South Africa only about 7% of the fly ash produced annually by coal-fired power stations, has being utilized. Although, fly ashes can be used as an alternative binder in alkali-activated concretes, strength development of these concretes at room temperature is slow limiting application of the material. Direct electric curing is proposed for heat curing of alkali-activated fly ash concrete which will open new opportunities for in-situ applications of these concretes in the construction industry thus increasing the amount of beneficially utilized fly ash. Alkaliactivated fly ash concretes containing unclassified low calcium fly ash, sodium hydroxide and sodium silicate solutions were cured at 60 ºC by means of direct electric curing. The electric resistivity and compressive strength development of the concretes were investigated. The resistivity strongly depends on the type of activator used. Compressive strength up to 33.8 MPa and 48.5 MPa at 2 and 28 days respectively, can be achieved after a short period of 2 direct electric curing. This opens new opportunities for wider application of alkali-activated fly ash concretes and for more extensive utilization of fly ash.

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Response of alkali activated fly ash mortars to microwave curing

Cited by 89 publications

References 32 publications

Confined-Direct Electric Curing of NaOH-activated fly ash based brick mixtures under free drainage conditions: Part 1. Factorial experimental design

Confined-Direct Electric Curing of NaOH-activated fly ash based brick mixtures under free drainage conditions: Part 1. Factorial experimental design

Comparative Study of Alkali-Activated Fly Ash Manufactured Under Pulsed Microwave Curing and Thermal Oven Curing

Direct electric curing of alkali-activated fly ash concretes: a tool for wider utilization of fly ashes

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