Ph.D. Thesis presentation
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Development of sustainable building materials using volcanic ash and sodium silicate by geopolymerization technique
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Ph.D. Thesis presentation
- 1. Welcome to the PhD defense of Mr. Djobo Yankwa Jean Noël Please switch off your phones 1
- 2. Synthesis factors, characteristics and durability of volcanic ash based geopolymer cements Jean Noël Y. Djobo PhD candidate Department of Inorganic Chemistry University of Yaoundé I, Cameroon 2 17-11-2017
- 3. 3 Outline Conclusion Recommendation for future works I II III IV V VI VII VIII
- 4. 4 Volcanic eruption and its disasters and impacts (Cai et al. 2016) State of the art: Volcanic ash Origin of volcanic ash Minerals contents Magmatic : quartz, etc Non-magmatic: Feldspar; Magnetite; Amphibole, Mica and Clay; Gypsum, etc. Chemical contents SiO2: 40-100% Al2O3: 9-17% Fe2O3: 1-15% CaO: 0-10% MgO: 0-10% Chemistry and mineralogy
- 5. 5 Construction and buildings - Lightweight aggregate in concrete - Pozzolana in blended cements - Geopolymer Uses of volcanic ash - Agriculture - Adsorbent - Ceramics State of the art: Volcanic ash - Filter media - Fillers (In rubber, paints and plastics)
- 6. 6 Geopolymer State of the art: geopolymer A chemical compound or a mixture of compounds consisting of repeating units of silico-oxide (Si-O-Si), silico-aluminate (Si-O-Al-O-), ferro-silico- aluminate (-Fe-O-Si-O-Al-O-), or alumino-phosphate (-Al-O-P-O-), created through a process of geopolymerization in an alkaline medium or phosphoric acid (Davidovits, 2008). Factors affecting geopolymerization and final properties The reactivity of the aluminosilicate material • Mineralogy Heat treatment Mechanical activation • Chemistry (molar ratio SiO2/Al2O3) Mineral additives (metakaolin, amorphous alumina, slag, etc.) The synthesis conditions • Curing conditions Curing temperature and time Autoclave Hydrothermal • The composition of the alkaline solution NaOH or KOH concentration Silica modulus (molar ratio SiO2/Na2O or SiO2/k2O) Water content (H2O/Na2O or H2O/K2O)
- 7. 7 Significance of the research Understand the underlying chemical reactions of geopolymerization of volcanic ash Master their effects on final properties of volcanic ash-based geopolymer cements/concretes High volume utilization of volcanic ash in construction Overcome the scarcity of construction materials in all the country Create employments in areas all around volcanic ash deposits
- 8. 8 Research questions • What is the correlation among synthesis conditions, reactivity of volcanic ash, reaction kinetic and gel composition? • How the Ca-modification of the chemistry of volcanic ash and different synthesis conditions affect the gel chemistry of resulting geopolymer? • What can be the effect of mechanical activation of volcanic ash on its reactivity and properties of resulting geopolymer? • What are the long-term mechanical properties and durability performance of volcanic ash based geopolymer mortar?
- 9. 12 Objective Understanding of the effects of synthesis factors on geopolymerization of volcanic ash, microstructural characteristics and long-tern durability of resulting geopolymer cements/mortars.
- 11. Map of Cameroon showing volcanic rocks deposits 11 Experimental methods: Solid materials - Oyster shell Mouanko (Littoral region, Cameroon) Alkaline solutions - NaOH: 8, 12 and 15M - NaOH+Na2SiO3:Ms (silica modulus) = 1.40, 1.5 and 1.66 Djoungo (Littoral Region of Cameroon) Loum (Littoral Region of Cameroon) Galim West Region of Cameroon - Volcanic ash Analytical techniques XRD, FTIR, 27Al and 29Si MAS-NMR, TGA, FESEM-EDX PSD, XRF, ICC
- 12. 12 Part I: synthesis conditions, reactivity and microstructure Part II: Gel composition, oyster shell-volcanic ash and synthesis conditions Part III: Mechanical activation of volcanic ash for geopolymer synthesis Part IV: Mechanical properties and durability Experimental methods: synthesis process and conditions - Reactivity (leaching in NaOH solution: 8, 10, 12M) - Ms (silica modulus) = 1.40, 1.5 and 1.66 - Curing temperatures: 27, 60 and 80 oC - 20 wt.% oyster shell addition - NaOH concentration: 8, 12 and 15M - Curing temperatures: 60 and 80 oC - Milling time: 0, 30, 60, 90 and 120 min - Ms (silica modulus) = 1.40 - Curing temperatures: 27, 45 and 60 oC - Curing temperature: 27 and 80 oC - Ms (silica modulus) = 1.40 - Acid resistance: 5wt.%sulfuric acid - Wet/dry cycle
- 13. 13 Results and discussion Part I • Synthesis conditions, reactivity and microstructure Part II • Gel composition, oyster shell-volcanic ash and synthesis conditions Part III • Mechanical activation of volcanic ash, geopolymerization Part IV • Mechanical properties and durability
- 14. 14 Part I: synthesis conditions, reactivity and microstructure Oxides SiO2 Al2O3 Fe2O3 CaO MgO Na2O TiO2 K2O Wt.% 46.28 15.41 13.32 9.07 6.74 3.88 2.84 1.42 Table: Chemical composition of volcanic ash Temperature NaOH concentration Concentration (ppm) Si Al Fe 27oC 8M 19.04 9.19 1.16 10M 18.74 8.76 1.58 12M 467.84 15.03 1.71 60oC 12M 520.40 175.68 2.04 80oC 12M 695.08 181.74 1.66 Reactivity: ICP-OES results of leached species
- 15. 15 Part I: synthesis conditions, reactivity and microstructure XRD patterns and IR spectra of RVA and volcanic ash-based geopolymers obtained with Ms = 1.4 at different curing temperatures
- 16. 16 Part I: synthesis conditions, reactivity and microstructure DTG of volcanic ash-based geopolymers obtained with Ms = 1.4 at different curing temperatures 2.67%%wt. 3.16 %wt. 4.07 %%wt.
- 17. 17 Part I: synthesis conditions, reactivity and microstructure FESEM micrographs and elemental maps of volcanic ash-based geopolymers obtained with Ms = 1.40 at different curing temperatures.
- 18. 18 Part I: synthesis conditions, reactivity and microstructure Relationship between Ca/Si and Na/Si; Fe/Si and Al/Si ratios of volcanic ash- based geopolymers obtained with Ms = 1.40 at different curing temperatures. Charge-balancing cations: Ca2+, Mg2+, and Na+ Poly (ferro-sialate-siloxo), Si/Al =2 Poly (ferro-sialate-disiloxo), Si/Al =3 Poly (ferro-sialate-multisiloxo), Si/Al >5
- 19. 19 Part I: synthesis conditions, reactivity and microstructure Volcanic ash is weakly reactive in alkaline solution The curing temperature is the main factor affecting the geopolymerization The dissolution behavior of Si is influenced by NaOH concentration, while Al is more sensitive to temperature Regardless the synthesis conditions the binder is of type Poly (ferro- sialate-siloxo), Poly (ferro-sialate-disiloxo), Poly (ferro-sialate-multisiloxo), with Ca2+, Mg2+, and Na+ as Charge-balancing cations Conclusion
- 20. 20 Oxide VA (wt. %) OS (wt. %) SiO2 41.36 0.30 Al2O3 15.41 0.19 Fe2O3 12.88 0.10 TiO2 3.04 - MnO 0.2 - MgO 6.45 - CaO 7.88 74.73 K2O 0.90 - Na2O 2.22 0.57 SO3 - 0.11 LOI 9.31 23.23 Chemical and mineralogical compositions of volcanic ash (VA) and oyster shell (OS) Part II: gel composition, oyster shell-volcanic ash, strength
- 21. 21 Part II: gel composition, oyster shell-volcanic ash, strength XRD patterns of alkali-activated oyster shell-volcanic ash C = calcite NH = sodium hydrogen silicate hydrate NS = sodium aluminosilicate hydrate D = diopside F = Faujasite- Na CH = Calcium silicate hydrate
- 22. 22 Part II: gel composition, oyster shell-volcanic ash, strength IR spectra of alkali-activated oyster shell-volcanic ash Carbonate group Calcium silicate hydrate
- 23. 23 Part II: gel composition, oyster shell-volcanic ash, strength Ternary diagram of alkali-activated oyster shell-volcanic ash plotted from EDS results.
- 24. 24 DTG of alkali-activated oyster shell-volcanic ash Part II: gel composition, oyster shell-volcanic ash, strength
- 25. 25 Part II: gel composition, oyster shell-volcanic ash, strength Dry (a = 60°C; c = 80°C) and wet (b = 60°C; d = 80°C) compressive strength of alkali-activated oyster shell-volcanic ash
- 26. 26 NaOH concentration is the main parameter affecting the gel composition of oyster shell- Volcanic ash (N, C)–A–S–H gel has been identified as the main phase in all samples with a C–S–H gel as a secondary phase in samples activated with NaOH, 15M The presence of CaO in raw Volcanic ash would have contributed to the formation of C–S–H gel in the presence of oyster shell The compressive strength is influenced by curing temperature and increases considerably with time Conclusion Part II: gel composition, oyster shell-volcanic ash, strength
- 27. 5 Effect of mechanical activation on particle size Part III: Mechanical activation of volcanic ash, geopolymerization
- 28. 28 Morphology and particles size changes of volcanic ash with milling time Part III: Mechanical activation of volcanic ash, geopolymerization
- 29. 29 XRD patterns of initial (0 min), 90 min and 120 min milled volcanic ash. 60.36% 38.29% 60.17% Part III: Mechanical activation of volcanic ash, geopolymerization Ano = Anorthite; F = Feldspar-Na; A = Augite; H = Hematite; Ds =Diopside sodian; Da =Diopside aluminian; Fs = Forsterite syn; Q =Quartz.
- 30. 30 IR spectra of initial 0 min, 90 min and 120 min milled volcanic ash Part III: Mechanical activation of volcanic ash, geopolymerization
- 31. 31 Heat released during geopolymerization reaction at 27°C of milled volcanic ash Part III: Mechanical activation of volcanic ash, geopolymerization
- 32. 32 Curing temperature Milling time Compressive strength (MPa) Setting time (min) 7d 28d 90d Initial Final 27 oC 30 min 0 0 13.1 600< - 60 min 11.2 15.8 32.1 150 180 90 min 15 21.7 37 15 23 120 min 15 22.2 45.8 22 32 45 oC 30 min 0 0 9.3 - 60 min 13.4 15.8 34.5 90 min 21 32.2 52.5 120 min 21 25.9 53.6 60 oC 30 min 0 0 6.6 - 60 min 15 17.2 29.4 90 min 35 37.4 48.3 120 min 32.1 34.5 46.8 Table: Physical and mechanical properties of mechanically activated volcanic ash based geopolymers Part III: Mechanical activation of volcanic ash, geopolymerization
- 33. 33 Part III: Mechanical activation of volcanic ash, geopolymerization Changes on morphology, size and distribution of particles Changes on the degree of crystallinity and mineralogical composition with the formation of quartz after 120 min. Chemical changes on the surface of volcanic ash grains, due to the mechanochemical reaction of volcanic ash grains with atmospheric CO2 MA reduced the setting time for more than 95% from 60 min of milling. 60 min is the least milling time requires to induce structural changes for non-reactive volcanic ash and achieve higher compressive strength . Conclusion
- 34. 34 Part IV: Mechanical properties and durability Water absorption and apparent porosity
- 35. 35 Part IV: Mechanical properties and durability Compressive strength evolution of volcanic ash based geopolymer mortars cured at 27 and 80 oC
- 36. 36 Part IV: Mechanical properties and durability Residual compressive strength evolution of volcanic ash-based geopolymer mortars during wet and dry cycles
- 37. 37 Part IV: Mechanical properties and durability Residual compressive strength and weight loss evolution of volcanic ash- based geopolymer mortars after exposure to 5 wt% sulfuric acid
- 38. 38 Part IV: Mechanical properties and durability Visual aspect of the core of volcanic ash-based geopolymer mortars after 90 (a) and 180 (b) days of exposure to 5% sulfuric acid 5 mm 10 mm
- 39. 39 Part IV: Mechanical properties and durability Micrographs and EDX spectra of volcanic ash-based geopolymer mortars cured at 27oC, after 180 days of exposure to 5% sulfuric acid Geopolymer binder embedded with Gypsum Sand
- 40. 40 Part IV: Mechanical properties and durability Micrographs and EDX spectra of volcanic ash-based geopolymer mortars cured at 80oC, after 180 days of exposure to 5% sulfuric acid Crack 1 2 80oC Geopolymer binder embedded with Gypsum Gypsum
- 41. 41 Part IV: Mechanical properties and durability Conclusion The geopolymer specimens have low water absorption and apparent porosity The maximum strength is achieved after 180 (25 Mpa) and 90 (37.9 Mpa) days for specimens cured at 27 and 80 oC respectively Specimens performed well in wetting and drying conditions with a maximum strength decrease of 24% and 14% for specimens cured at 27 and 80 oC respectively Geopolymer specimens obtained at 27 oC developed a better resistance to 5% sulfuric acid than the ones cured at 80 oC. The pore structure and permeability prone the formation of gypsum as a secondary phase, they are the key factors affecting the durability of volcanic ash based geopolymer mortars
- 42. 42 General Conclusion Volcanic ash is weakly reactive in alkaline solution The secondary elements such as iron (Fe), Calcium (Ca) and Magnesium (Mg) present in volcanic ash take part to the geopolymerization reaction and do not have any negative effect in the final product Mechanical activation is a suitable route to enhance reactivity of volcanic ash. Volcanic ash based geopolymers binder is of type: poly (ferro- sialate-siloxo), poly (ferro-sialate-disiloxo) and poly (ferro- sialate-multisiloxo) with Ca2+, Mg2+, and Na+ as charge balancing cations. Volcanic ash based geopolymer mortars developed a good performance to the durability tests assessed (wet/dry cycle, acid resistance)
- 43. 43 Recommendations for future study Study the effect of rising temperature on kinetic of geopolymerization of volcanic ash using other analytical techniques Investigate other durability tests such as: carbonation, alkali- silica-reaction, rapid chloride permeability, water and gas (CO2) permeability.
- 44. 44 Résumé: conditions de synthèses, réactivité et microstructure Réactivité Température ConcentrationNaOH Température Modulesilicique,Ms Microstructure: type de liant Cations compensateurs: Ca2+, Mg2+, et Na+ Poly (ferro- sialate-siloxo), Si/Al =2 Poly (ferro-sialate-disiloxo), Si/Al =3 Poly (ferro-sialate-multisiloxo), Si/Al >5
- 45. 45 Résumé: Activation alkaline coquille d’huitre- scorie volcanique Température ConcentrationNaOH 12M N,C-A-S-H C-S-H N-(C)-A-S-H C-(N)-A-S-H N,C-A-S-H Gel composition ConcentrationNaOH Température Résistance à la compression Temps
- 46. 46 Résumé: Activation mécanique et géopolymérisation
- 47. 47 Résumé: Propriétés mécaniques et durabilités des mortiers géopolymères Na-riche gel - Pourcentage d’absorption deau: 6-7% - Porosité apparente: 13-15% - Masse volumique: 2049-2186 Kg/m3 - Résistance à la compression: 20-38 MPa Gypse Avant Après Compositionmicrostructural Temps Diminution de la résistance a la compression: 24-60 % - Les échantillons traités à la temperature ambiante on une méilleure resistance a l’acide que ceux traités a 80 oC. - Les échantillons géopolymères ont montré une meilleure résistance au cycle chaud/humide avec une perte de resistance de 14-24 % après 25 cycles.Phases géopolymères Phases géopolymères
- 48. Published papers 48 1. Djobo et al. (2016) Reactivity of volcanic ash in alkaline medium, microstructural and strength characteristics of resulting geopolymers under different synthesis conditions. Journal of Material Sciences, 51:10301–10317. 2. Djobo et al. (2016) Gel composition and strength properties of alkali-activated oyster shell-volcanic ash: Effect of synthesis conditions, Journal of the American Ceramic Society, 99 (9), 3159–3166. 3. Djobo et al. (2016) Mechanical activation of volcanic ash for geopolymer synthesis: effect on reaction kinetics, gel characteristics, physical and mechanical properties. RSC Advances, 6(45), 39106 – 39117. 4. Djobo et al. (2016) Mechanical properties and durability of volcanic ash based geopolymer mortars. Construction and Building Materials. 124: 606-614. 5. Djobo et al. (2017) Volcanic ash-based geopolymer cements/concretes: the current state of the art and perspectives. Environmental Science and Pollution Research. 24:4433 – 4446 International peer-reviewed Journals
- 49. 49 Acknowledgments Council of Science and Industrial Research National Metallurgical Laboratory The Third World Academic of Science University of Yaoundé I
- 50. 50
Editor's Notes
- Good afternoon everybody. I’m here to share with you the keys findings of my PhD works, with the title: “Synthesis factors, characteristics and durability of volcanic ash based geopolymer cements”
- The main points to be discuss along this talk involve the following.
- Volcanic ashes are fragments of pulverized rocks, minerals and volcanic glass produced during volcanic eruption and whose particles have diameters less than 2 mm. This natural process has some environmental impact and cause many damages as presented in this figure. These include the pollution of water supply systems, interruption of power supplies, destruction of communication systems, damage on human life and properties. The chemistry of volcanic ash includes silica, alumina and iron as major elements….. Their mineralogical content is classified as magmatic and non-magmatic minerals
- Volcanic ash has many uses that range from their uses as fertilizer in agriculture to raw material for preparation of abrasives, building-blocks cement, concrete, geopolymer etc. A brief review in the use of volcanic ash these last 10 years shows that the research is mainly directed towards its use in making building materials. For these last decades, there have been emerging research area on cement/concretes, named geopolymer science for which increasing interest in the utilization of volcanic ash is visible. The following Figure shows that after 2012, the main investigation of their uses shifted in the synthesis of geopolymers.
- now let’s talk about geopolymer which is defined as a chemical compound……. That geopolymerization depend on many factors. The first one is the reactivity of aluminosilicate which includes The chemical composition mostly the molar ratio SiO2/Al2O3. For materials with low content in these elements adjustment are generally made by adding Al or Si rich mineral in order to achieve a good geopolymerization reaction. Another parameter is the mineralogy of the aluminosilicate. It must be pointed out that this is the most important parameter, as the materials should be mostly amorphous to be reactive. So for crystallized materials it has been suggested some processes such as heat treatment and mechanical activation to alter the mineralogy of aluminosilicate and enhance its reactivity. The second factor are the synthesis conditions which involve Curing conditions and the composition of the alkaline solution as well as Liquid to solid ratio.
- the significance of carrying out research on VA uses in geopolymerization is that it is helpful for…
- the major questions that drawn our attention when reviewing the existence literature on volcanic based geopolymer include among other: …………
- We will attempt to answer these questions by……..
- to achieve that objective some experiments has been carried out and the results discussed. This part of my talk present briefly all the materials, experiment and equipment used. It is divided in 4 major parts in respect to the research question that we are trying to answer.
- the three volcanic ash used here have been collected in Cameroon. One was harvested in west region around the mount Bamboutos, and the other in Littoral region around the mount manengumba and mount koupe. Oyster shell has also been used as calcium source and collected in Littoral region. Two types of alkaline solution have been used The analytical techniques to characterize our samples include the following
- in respect to the research questions that we are trying to answer. The experiments were divided in 4 major parts as shown here. The different synthesis and nalytical processes are also described as follow…..
- Dear mr president of jury, honorable member of the jury let me now present the keys results and detailed discussions of the investigations described in previous section. This part is also divided into 4 subsection as shown here.
- In this part we will discuss on the effect of concentration of alkaline solution and temperature on reactivity of volcanic ash, geopolymerization and microstructure of geopolymers. The volcanic ash used in this part has the following chemical composition. As it can be seen the major elements are silica, alumina and iron. The results of the leaching behavior of reactive elements of volcanic ash in different NaOH concentrations and temperature are reported in this table As it can be seen only Si, Al and Fe are detectable in the filtrate. Compared to other elements, the dissolution of Si is mostly influenced by concentration between 10 and 12M at room temperature, whereas when the temperature rises the dissolution of Si keeps increasing but much less than the one of Al. the latter corresponds to an increase of the amount of dissolved species from 2 to 22% in respect to the total amount of Al initially present. So, reactivity of volcanic ash is most affected by the temperature than concentration.
- Les resusltats issus de ces travaux ont faits l’objet de plusieurs articles scientifiques publies dans les revues internationals a comite de lectures dont les references sont presente ici.