Preparation of new cementitious system using fly ash and dehydrated autoclaved aerated concrete

Abstract

We experimentally studied the interaction between pozzolanic material (fly ash) and dehydrated autoclaved aerated concrete (DAAC). The DAAC powder was obtained by grinding aerated concrete waste to particles finer than 75μm and was then heated to temperatures up to 900 °C. New cementitious material was prepared by proportioning fly ash and DAAC, named as AF. X-ray diffraction (XRD) was employed to identify the crystalline phases of DAAC before and after rehydration. The hydration process of AF was analyzed by the heat of hydration and non-evaporable water content (W _n). The experimental results show that the highest reactivity of DAAC can be obtained by calcining the powder at 700 °C and the dehydrated products are mainly β-C₂S and CaO. The cumulative heat of hydration and W _n was found to be strongly dependent on the replacement level of fly ash, increasing the replacement level of fly ash lowered them in AF. The strength contribution rates on pozzolanic effect of fly ash in AF are always negative, showing a contrary tendency of that of cement-fly ash system.

Keywords

dehydrated autoclaved aerated concrete / pozzolanic reaction / heat of hydration / nonevaporable water content / strength contribution rate

References

[1] Siddique R Waste Materials and By-Products in Concrete[M], 2007

[2] Necille AM Properties of Concrete[M], 1995 England Pearson Education Limited

[3] Mostafa NY Influence of Air-cooled Slag on Physicochemical Properties of Autoclaved Aerated Concrete[J]. Cem. Concr. Res., 2005, 35(7): 1349-1357.

[4] Narayanan N, Ramamurthy K Structure and Properties of Aerated Concrete: a review[J]. Cem. Concr. Compos., 2000, 22(5): 321-329.

[5] Tada S, Nakano S Wittmann FH Microstructural Approach to Properties of Moist Cellular Concrete[C]. Proceedings Autoclaved Aerated Concrete, Moisture and Properties, 1983 Amsterdam Elsevier 71-89.

[6] Advanced Building Technologies-Autoclaved Aerated Concrete, Advanced Building Organization[OL]. http://www.advancedbuildings.org/aercon.html, 1999

[7] Kurama H, Topcu IB, Karakurt C Properties of the Autoclaved Aerated Concrete Produced from Coal Bottom Ash[J]. J. Mater. Process Technol., 2009, 209(2): 767-773.

[8] Mostafa NY Influence of Air-cooled Slag on Physicochemical Properties of Autoclaved Aerated Concrete[J]. Cem. Concr. Res., 2005, 35(7): 1 349-1 357.

[9] Huang XY, Ni W, Cui WH, . Preparation of Autoclaved Aerated Concrete Using Copper Tailings and Blast Furnace Slag[J]. Constr. Build. Mater., 2012, 27(1): 1-5.

[10] Guerrero A, Gonňi S, Macĭas A, . Effect of the Starting Fly Ash on the Microstructure and Mechanical Properties of Fly Ashbelite Cement Mortars[J]. Cem. Concr. Res., 2000, 30(4): 553-559.

[11] Pan GY Investigation on Foundation and Utilization of Cementitious Material About Dehydrated Hydrates Phases (DHP)[D], 1995

[12] Alonso C, Fernandez L Dehydration and Rehydration Processes of Cement Paste Exposed to High Temperature Environments[J]. J. Mater. Sci., 2004, 39(9): 3 015-3 024.

[13] Shui ZH, Xuan DX, Wan HW, . Rehydration Reactivity of Recycled Mortar from Concrete Waste Experienced to Thermal Treatment[J]. Constr. Build. Mater., 2008, 22(8): 1 723-1 729.

[14] Teramura S, Isu N, Inagaki K New Building Material from Waste Concrete by Carbonation[J]. J. Mater. Civ. Eng., 2000, 12(4): 288-293.

[15] Topcu IB, Sarıdemir M Prediction of Properties of Waste AAC Aggregate Concrete Using Artificial Neural Network[J]. Comput. Mater. Sci., 2007, 41(1): 117-125.

[16] Sinica M, Sezemanas G, Mikulskis D, . Investigation of Sorption Properties in Crushed Autoclaved Aerated Concrete Waste[J]. Journal of Environmental Engineering and Landscape Management, 2012, 20(1): 67-75.

[17] Hartmann A, Buhl JC, Lutz W Synthesis and Properties of Zeolites from Autoclaved Aerated Concrete (AAC) Waste[J]. Zeitschrift für anorganische und allgemeine Chemie., 2012, 638(9): 1 297-1 306.

[18] Zhang YM, Sun W, Yan HD Hydration of High-volume Fly Ash Cement Pastes[J]. Cem. Concr. Compos., 2000, 22(6): 445-452.

[19] Atis CD Heat Evolution of High-volume Fly Ash Concrete[J]. Cem. Concr. Res., 2002, 32(5): 751-756.

[20] Snelson DG, Wild S, O’Farrell M Heat of Hydration of Portland Cement-Metakaolin-Fly Ash (PC-MK-PFA) Blends[J]. Cem. Concr. Res., 2008, 38(6): 832-840.

[21] Mehta PK, Gjorv OE Properties of Portland Cement Concrete Containing Fly Ash and Condensed Silica Fume[J]. Cem. Concr. Res., 1982, 12(5): 587-595.

[22] Nocuń-Wczelik W Heat Evolution in Hydrated Cementitious Systems Admixtured with Fly Ash[J]. J. Therm. Anal. Calorim., 2001, 65(2): 613-619.

[23] Pu XC, Liu F, Wang C, . Study on Analytical Methods for the Specific Strength of Pozzolanic Effect of Active Mineral Admixtures in High Performance Concrete[C]. Proceedings of Development of High Performance Concrete and Mineral Admixture Research and Engineering Technology National Conference, 2006 158-164.

[24] Antiohos S, Tsimas S Activation of Fly Ash Cementitious Systems in the Presence of Quicklime: Part I. Compressive Strength and Pozzolanic Reaction Rate[J]. Cem. Concr. Res., 2004, 34(5): 769-779.

[25] Sakai E, Miyahara S, Ohsawa S, . Hydration of Fly Ash Cement[J]. Cem. Concr. Res., 2005, 35(6): 1 135-1 140.

[26] Qian JS, Shi CJ, Wang Z Activation of Blended Cements Containing Fly Ash[J]. Cem. Concr. Res., 2001, 31(8): 1 121-1 127.