Scholarly article on topic 'Lime Activated Fly Ash Paste in the Presence of Metakaolin'

Lime Activated Fly Ash Paste in the Presence of Metakaolin Academic research paper on "Materials engineering"

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Procedia Engineering
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{"Fly ash" / Geopolymer / "High LOI fly ash" / Lime / Metakaolin / Paste}

Abstract of research paper on Materials engineering, author of scientific article — Jamal M. Khatib, Rafat Siddique, C. Halliday, S. Khatib

Abstract The strength and ultrasonic pulse velocity of fly ash paste activated by lime and metakaolin is presented in this paper. Two fly ash pastes were prepared, one without metakaolin and one with 25% of metakaolin to replace the fly ash. Chemical activation was implemented by adding 10% lime (by weight of fly ash and metakaolin) to both pastes. The water-to-binder materials were maintained at a constant of 0.6 for both pastes. The binder consists of fly ash, metakaolin, and fly ash. There is strength enhancement for the paste containing metakaolin compared with the paste without metakaolin. The same trend was obtained for the ultrasonic pulse velocity values.

Academic research paper on topic "Lime Activated Fly Ash Paste in the Presence of Metakaolin"

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Procedía Engineering 95 (2014) 415 - 418

Procedía Engineering

www.elsevier.com/locate/proeedia

2nd International Conference on Sustainable Civil Engineering Structures and Construction

Materials 2014 (SCESCM 2014)

Lime activated fly ash paste in the presence of metakaolin

Jamal M. Khatiba*, Rafat Siddiqueb , C. Hallidaya, S. Khatibc

a Faculty of Science and Engineering, University of Wolverhampton, Wolverhampton, WV1 1LY, UK b Civil Engineering, Thapar University, Patiala, India c College of Engineering, Swansea University, UK

Abstract

The strength and ultrasonic pulse velocity of fly ash paste activated by lime and metakaolin is presented in this paper. Two fly ash pastes were prepared, one without metakaolin and one with 25% of metakaolin to replace the fly ash. Chemical activation was implemented by adding 10% lime (by weight of fly ash and metakaolin) to both pastes. The water-to-binder materials were maintained at a constant of 0.6 for both pastes. The binder consists of fly ash, metakaolin, and fly ash. There is strength enhancement for the paste containing metakaolin compared with the paste without metakaolin. The same trend was obtained for the ultrasonic pulse velocity values.

Crown Copyright© 2014PublishedbyElsevierLtd.This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

Peer-review underresponsibility oforganizingcommittee of the 2nd International Conference on Sustainable Civil Engineering Structures and Construction Materials 2014

Keywords: Fly ash; Geopolymer; High LOI fly ash; Lime; Metakaolin; Paste

1. Introduction

The quest for a new and less energy cement such as the use of geopolymers or activated alumina-silicate materials as potential construction materials has seen interests in recent years [1]. Cement manufacturing is responsible for about 10% of the global carbon dioxide emission; this may be due to the need of reducing the energy intensive cement in construction applications. Alumino-silicate materials include pozzolanic materials such as fly ash and metakaolin. These materials can be activated by using alkali based materials such as sodium silicates,

* Corresponding author. Tel: +44 1902 32 8588 E-mail address: j.m.khatib@wlv.ac.uk

1877-7058 Crown Copyright © 2014 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).

Peer-review under responsibility of organizing committee of the 2nd International Conference on Sustainable Civil Engineering Structures and Construction Materials 2014 doi: 10.1016/j.proeng.2014.12.200

sodium hydroxide (NaOH), potassium hydroxide (KOH), and lime Ca(OH)2 [2]. The properties and characteristics of the final products, such as strength, length change, and durability such as chemical attack, would depend on the raw material used, composition, age of curing, and curing temperature.

Khatib and Clay [3] and Chao Li et al. [4] reported that the use of metakaolin as partial substitution to cement is reported to increase the strength of the paste. This was attributed to the high surface area and the platy shape of metakaolin particles. There is not too much work on activating a combination of more than one pozzolanic material. In this work, fly ash and metakaolin were combined and activated with lime to study their properties. Metakaolin was chosen due to its fineness whereas the fly ash was used because it is a waste pozzolanic material. The properties investigated were compressive strength and ultrasonic pulse velocity.

2. Experimental

The materials used in this work were fly ash (FA), metakaolin (MK), lime (L), and water. The fly ash was unprocessed fly ash with high loss on ignition (LOI). The metakaolin (MK) used was calcined at 800oC with a surface area of 12,000 m2/kg. Two pastes were used, details of which are given in Table 1. The water-to-binder ratio was kept constant at 0.6. The binder consisted of all dry materials (FA+MK+L).

Table 1: Details of pastes.

Paste No. Paste Code Binder (B1) - % by FA1 MK2 weight L3 W5/B

P1 100FA0MK10L 100 0 10

P2 75FA25MK10L 75 25 10

'Binder (consists of FA +MK+L), 2 Fly ash, 3Metakaolin, 4 Lime(% addition by weight of FA+MK)

5 Water

The dry materials (FA, MK and L) were blended thoroughly. Water was then added slowly and proper mixing was conducted until the mix was homogenous. The pastes were cast in steel moulds of 50mm in size. After 24 hours, the specimens were demoulded and the specimens were placed in bags at 21o ± 1oC to avoid any loss or gain in moisture until testing. Testing for compressive strength and ultrasonic pulse velocity (UPV) was conducted at day 1, 7, 28, and 56.

3. Result and discussion

Fig. 1 shows the strength development of lime activated pastes with and without metakaolin. The strength of the pastes is low compared with a traditional control paste made at the same water-to-cement ratio. The lime activated fly ash paste show much lower strength than the paste containing metakaolin. However, the strength shows a noticeable increase after 28 days of curing compared with a traditional cement paste. Using 25% metakaolin as fly ash replacement causes a strength increase beyond the first day of curing. The strength continues to increase beyond the 28 days period. It is good to note that the strength on the 1st day of curing is the same for both pastes. The relative strength of the paste with respect to its strength during the time span of 28 days is plotted in Fig. 2. The relative strength of the paste containing metakaolin is either similar or slightly lower than the paste without metakaolin. The lime fly ash paste shows more strength development after 28 days of curing. The enhancement in compressive strength with curing age is consistent with results obtained by Badoginnis [5], Wild et al. [6] and Khatib and Hibbert [7].

Fig. 1. Strength development of lime activated fly ash paste with and without metakaolin.

Age (days)

Fig. 2. Relative strength to that of 28 days of lime activated fly ash paste with and without metakaolin.

Fig. 3 shows the ultrasonic pulse velocity (UPV) of all mixes at different ages. The trend is similar to those of compressive strength up to the age of 28 days. After 28 days of curing, the UPV does not seem to increase. Generally an increase in strength is associated with an increase in UPV.

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Fig. 3. Ultrasonic pulse velocity (UPV) profile for the pastes.

4. Conclusion

It can be deduced from this preliminary experimental research, that the compressive strength development and ultrasonic pulse velocity is dependent on the metakaolin content in the mix and curing age. As the curing age increases the compressive strength increases at a higher rate after 28 days of curing for lime activated paste with and without metakaolin. The incorporation of metakaolin leads to further increase in strength.

Acknowledgements

The authors would like to thank the Technical staff Mr G Cooper and Mr R Bradley in the Faculty of Science and Engineering, University of Wolverhampton for their assistance.

References

[1] Davidovits, J. (1994) Properties of Geopolymer Cements: P.V. Krivenko (Ed.), Proceedings of First International Conference on Alkaline Cements and Concretes, Kiev, Ukraine, 1, pp. 131-149.

[2] Fernandez-Jimenez, A., Palomo, A. (2003) Fuel 82 journal, pp.2259-2265.

[3] Khatib, J. M., Clay, R. M. (2003) Absorption characteristics of metakaolin concrete. Journal of Cement and Concrete Research, 34, pp.19 - 29.

[4] Chao, L., Henghu, Sun., Longtu, Li. (2010) A review: The comparison between alkali-activated slag (Si+Ca) and metakaolin (Si+Al) cements. Journal of Cement and Concrete Research, 40, pp. 1341-1349.

[5] Badogiannis, E., Kakali , G., Dimopoulou , G., Chaniotakis ,E., Tsivilis, S.,(2005). Metakaolin as a main cement constituent. Exploitation of poor Greek kaolins..Journal oof Cement & Concrete Composites, 27, pp. 197-203

[6] Wild, S., Khatib, J.M., and Jones, A. (1996).Relative strength, pozzolanic activity and cement hydration in super plasticised metakaolin concrete Journal of Cement and Concrete Research, 26, pp.1537-44.

[7] Khatib, J.M., Hibbert, J. J.(2005)Selected engineering properties of concrete incorporating slag and Metakaolin. Journal of Construction and Building Materials 19, pp. 460-472.

[8] Ambroise J, Maxmilien S, Pera J.(1994) Properties of metakaolin blended cement, Journal oof Advanced Cement Based Material;1: pp.161-8.

[9] Batis, G., Pantazopoulou, P., Tsivilis, S., &Badogiannis, E.(2005)The effect of metakaolin on the corrosion behaviour of cement mortars. Journal of Cement and Concrete Composites, 27, pp.125—130.

[10] Demirboga, R., Turkmen, I., Karakoc, M. B. (2004) Relationship between ultrasonic velocity and compressive strength for high-volume mineral-admixtured concrete Journal oof Cement and Concrete Research, 34, pp. 2329-2336.

[11] Palomo, A., Blanco-Varela, M.T., Granizo, M.L. Puertas, F. Vazquez, T. Grutzeck, M.W.(1999) Chemical stability of cementitious materials based on metakaolin. Journal Cement and Concrete Research, 29, pp. 997—1004.

[12] Ye, G., Lura, P., Van Breugel, K., Fraaij, A.L.A. (2004) Study on the development of the microstructure in cement-based materials by means of numerical simulation and ultrasonic pulse velocity measurement. Journal of Cement & Concrete Composites, 26, pp. 491-497.