Thermal, Insulation and Fire Resistance Characteristics of Ternary Blend Geopolymers from Philippine Coal and Rice Hull Ashes

Transcription

1 Thermal, Insulation and Fire Resistance Characteristics of Ternary Blend Geopolymers from Philippine Coal and Rice Hull Ashes Kalaw, Martin Ernesto L. 1, Gallardo, Susan 2, and Promentilla, Michael Angelo 3 1 Mechanical Engineering Department, De La Salle University, Philippines. ( martin.kalaw@dlsu.edu.ph) 2 Chemical Engineering Department, De La Salle University, Philippines. ( susan.gallardo@dlsu.edu.ph) 3 Chemical Engineering Department, De La Salle University, Philippines. ( michael.promentilla@dlsu.edu.ph) Gokongwei College of Engineering De La Salle University Manila, Philippines

2 Outline of Presentation I. Some Significant Concerns II. Generation of Coal Ash and Rice Hull Ash III. The Case of OPC IV. Options for Coal Ash and Rice Hull Ash Utilization V. Specimen Preparation VI. Resulting Properties of Geopolymer Samples VII.DTA-TGA, SEM, FTIR and XRD Tests VIII.Conclusions IX. Acknowledgements

3 Some Significant CONCERNS: - increasing generation and accumulation of industrial and agro-industrial wastes such as coal ash and rice hull ash and their by-products - depletion of natural resources used in the production of conventional materials, i.e. OPC

4 - GHG emissions in the production of conventional materials, i.e. OPC environmental impact (surface water, groundwater and soil contamination), health risks, lack of landfill areas, etc

5 Generation of Coal Ash and Rice Hull Ash Table 1. Rice production and coal consumption Country 2014 Paddy rice production * [10], MMT 2012 Coal consumption * [12], MMT Philippines Vietnam Thailand Japan China

6 Duke Eden, NC coal ash spill, February 2014

7 Coal Ash Contaminated Sites and Hazard Dams in the US

8 The Case of OPC Next to water, concrete is the second-most consumed substance on earth; on average, each person uses nearly three tonnes a year. Portland cement, the major component of concrete, is used to bind the materials that make up concrete. The concrete industry uses about 1.6 billion tonnes of Portland cement and produces some 12 billion tonnes of concrete a year. The industry has a large ecological footprint: it uses significant amounts of natural resources such as limestone and sand, and depending on the variety and process, requires kg of fuel oil and 110 kwh of electricity to produce each tonne of cement. In addition, the cement industry is second only to power generation in the production of CO 2. Producing one tonne of Portland cement releases roughly one tonne of CO2 to the atmosphere, and sometimes much more, and the cement industry accounts for 7-8 per cent of the planet s human-produced CO 2 emissions. United Nations Environment Programme (UNEP)

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10 Options for Coal Ash and Rice Hull Ash Utilization Geopolymers inorganic polymer binders formed via alkaline activation of alumino-silicate materials

11 technically viable, economically competitive, and environmentally attractive vis-a-vis ordinary Portland cement (OPC). significantly lower CO 2 emissions more economical for both users and waste materials generators sustainable since can be synthesized from alumina- and silica- rich industrial and agro-industrial wastes

12 Geopolymerization mainly involves the dissolution of the amorphous alumina and silica in highly alkali solutions and the subsequent polycondensation resulting in the formation of a three-dimensional amorphous alumina-silicate network.

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14 Specimen Preparation Dry Components RICE HULL ASH COAL FLY ASH COAL BOTTOM ASH Alkali Activator: NaOH/waterglass solution

15 Range of mass proportions of components Sample CFA % CBA % RHA % A A A A A A A A A A

16 Composition of raw materials Components RHA CBA CFA Al 2 O SiO Fe 2 O K 2 O CaO TiO Na 2 O Others

17 Steps Used in the Preparation of Geopolymer Specimens

18 Mixer and molds used for geopolymer preparation

19 Resulting Properties of Geopolymer Samples Alkali Solution NaOH 12M/WG 20% Sample CFA % CBA % RHA % volumetric weight (kg/m 3 ) compres sive strength (MPa) A A A A A A A A A A

20 CFA CBA RHA vol. wt. comp str 1000 heat resist A A A A A A A A A A

21 ASTM C90 prescribes that light weight, load bearing OPC concrete masonry units must have a compressive strength of at least 11.7 MPa and average density below 1680 kg/m 3. From the results, it can be seen that there are mix proportions of the raw materials that has properties that matched light weight, load bearing OPC concrete.

22 DTA-TGA Tests Geopolymer Samples that Does Not Contain RHA pure CFA geopolymer pure CBA geopolymer CFA-CBA geopolymer - moisture losses associated with drying are from 6% to 8% - no abrupt or rapid reactions within the temperature range of the tests

23 Geopolymer Samples that Contain RHA RHA = 1, CFA = 0, CBA = 0 RHA =2/3, CFA = 1/6, CBA = 1/6 RHA = ½, CFA = ½, CBA = 0 - drying moisture loss is about 44% at RHA = 1, 23% at RHA = 2/3, 22% at RHA = 1/3, and an average of 18% at RHA = 1/6. Thus, as RHA decreases, the associated moisture loss also decreases. - the exothermic reaction that occurs between 350 o C to 450 o C is decreasing as RHA decreases

24 The high water utilization and retention of RHA-containing geopolymers may be attributed to high porosity and high unburned carbon content of the RHA used.

25 Geopolymer Samples after Exposure to 1000 o C for 2 hours - for all samples, moisture loss is below 1% for the entire range of temperature used in the tests - the samples are effectively both chemically and thermally stable after exposure to 1000 o C.

26 SEM Tests RHA x500 Pure RHA geopolymer x500 After exposure to 1000 o C x500 The bigger particles and void spaces as seen in the SEM micrograph of the RHA sample suggests the high porosity of RHA raw material.

27 CFA x1000 Pure CFA geopolymer x1000 After exposure to 1000 o C x1000

28 FTIR Tests RHA raw material Pure RHA geopolymer Frequency of cm -1 indicates O-H bond (water). Frequency of cm -1 indicates C-C bonds (i.e. unburned carbon). Frequency near 1100 cm -1 represents silica. Frequencies from cm -1 include the weaker Si-O- and Al-O- bonds.

29 Geopolymer with Decreasing Amount of RHA RHA = 2/3, CFA = 1/6, CBA = 1/6 RHA = ½, CFA = ½, CBA = 0 RHA = 1/3, CFA = 1/3, CBA = 1/3 - very little shifting of the peaks indicating poor geopolymerization process resulting in high amounts of unreacted silica and low strength (from compression tests). - the poor reaction of silica may be attributed to high amounts of crystalline (quartz) SiO 2 in the RHA, CFA and CBA as seen from XRD tests

30 The low strength of these geopolymer samples may be attributed to high amounts of unreacted silica and low alumina content (thus very high Si/Al ratio), too much water, and incomplete curing.

31 XRD Tests RHA raw material CFA raw material CBA raw material the raw materials may have significant crystalline forms that results in low reactivity

32 Effect of RHA on Geopolymerization, using CFA as reference CFA=1/6 RHA = 2/3 CFA = ½ RHA = ½ CFA = 1/3 RHA = 1/3 CFA = 2/3 RHA = 1/6 CFA = 1 RHA = 0

33 Effect of RHA on Geopolymerization, using CBA as reference CBA=1/6 RHA = 2/3 CBA = ½ RHA = ½ CBA = 1/3 RHA = 1/3 CBA = 2/3 RHA = 1/6 CBA = 1 RHA = 0

34 It has been observed, also using data from the compression tests, that increasing RHA concentration does not improve strength. As RHA concentration increases the Si/Al ratio also increases. And as silica increases, there is also a higher probability of increased unreacted silica which was confirmed from the tests shown.

35 After Exposure to 1000 o C CFA-RHA geopolymer The increased number of peaks indicates the formation of new crystalline structures in the geopolymer.

36 Fire Resistance Tests ASTM E119 Standard Test Methods for Fire Tests of Building Construction and Materials Specimen failure if: temperature of the unexposed surface rises an average of 140 C above its initial temperature Visual cracking is exhibited 5 minutes 538 C 10 minutes 704 C 30 minutes 843 C 1 hour 927 C 2 hours 1010 C

37 Fire Resistance Tests Specimen Geopolymer (95-5 FA RHA) Geopolymer (50-50 FA BA) Geopolymer (100 FA) Geopolymer (100 BA) Geopolymer (85-15 FA BA) Geopolymer ( FA BA RHA) Pure Cement Concrete 1:2:3 (C:S:G) Fire Resistance Rating (50 mm thickness) 64 minutes 67 minutes 77 minutes 58 minutes 71 minutes 65 minutes 35 minutes 31 minutes

38 Specimen Compressive Strength, MPa (Unfired) Compressive Strength, MPa (Fired) % Pure Cement % 100 FA % FA BA %

39 Conclusions Based on the results of this study, the following conclusions are made: 1. Geopolymers from mixtures of CBA, RHA and with NaOH/WGS as activator can be developed with properties suitable for lightweight and moderate strength.

40 2. The resulting geopolymers show better fire and heat properties vis-à-vis OPC. 3. The thermal conductivity can be made comparable to that of OPC based material.

41 4. Based on the raw materials used, RHA does not improve the strength characteristics of geopolymers due to low reactivity. 5. But by exposing the geopolymer to high temperatures the strength can be markedly improved.

42 Thus, the geopolymers, with raw material proportions and characteristics used in this study, show potential as practical building materials for structures that allow lightweight and low to moderate strength materials (i.e. low rise residential buildings) as a supplement to OPC if total replacement is still not supported by the building codes. Such materials also have characteristic fire and heat resistance that are markedly better than conventional OPC.

43 ACKNOWLEDGEMENTS: - DLSU students Alfredo Relucio, Timothy Ngo, Paul Palaypayon and Melvin Lim - Mech Eng, Chem Eng and Civil Eng Depts. of De La Salle University, Manila - Hinode Lab of the Int l Devt Eng Dept. of Tokyo Inst of Technology - JICA and AUN/SEEDNet CRC project Development of Sustainable Solutions to Coal Ash Management in the Asian Region.

44 THANK YOU VERY MUCH!!!