IGC. 50 th INDIAN GEOTECHNICAL CONFERENCE STABILIZATION OF INDUSTRIAL BY-PRODUCTS USING ALKALI ACTIVATION

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1 5 th IGC 5 th INDIAN GEOTECHNICAL CONFERENCE 7 th 9 th DECEMBER 25, Pune, Maharashtra, India Venue: College of Engineering (Estd. 854), Pune, India STABILIZATION OF INDUSTRIAL BY-PRODUCTS USING ALKALI ACTIVATION S.P.Singh, J. Sahoo 2, S.Samantasinghar 3 ABSTRACT With an increase in the growth of industrialization, proper disposal of wastes is one of the major issues nowadays that have to be handled with seriously. An innovative solution that is efficient and environment friendly is required to tackle this problem of disposal. Research has sprung to full pace in recent years on how to utilize these waste materials in an effective way. Geopolymerization is the latest trend in that path. Geopolymerization is a very favourable innovative technology that can transform useless industrial solid wastes of alumino-silicate composition into useful products competitive with many known civil infrastructure construction materials. They have excellent mechanical properties (e.g., compressive strength and stiffness), low shrinkage potential, excellent adhesion to aggregates, and exceptional high resistance to heat, organic solvents and acids; also they are low cost having low energy consumption and CO 2 emissions during synthesis. The basic requirements for the synthesis of any geopolymer are alkali solution and aluminosilicate material. So the by-products which are rich in silica and alumina can be used as aluminosilicate sources. In the present work, four industrial by-products namely ground granulated blast furnace slag, fly ash, rice husk ash and red mud were taken as raw materials and sodium hydroxide has been used as alkali to activate the alumino-silicate source. All the materials except rice husk ash constitute alumina along with silica. Rice husk ash, being rich in silica, was taken as one of the raw material to investigate the effects of NaOH on it. These four materials were activated by NaOH with varying percentages i.e. 5%, %, 5% of the raw material. Standard proctor compaction tests were conducted for each addition of activator to the raw material. Maximum dry densities of the materials increase with increase in NaOH % while optimum moisture content decreases. This trend is noticed for all the four waste materials. The effect of different percentages of NaOH on the strength of raw materials was investigated by unconfined compressive tests. For each combination of raw material and percentage of NaOH, three samples were prepared at optimum moisture content and maximum dry density and kept for curing at ambient temperature of 27 C for prefixed periods (i.e. day, 7days, and 28 days). The results show that with an Professor, Civil Engineering Department, NIT Rourkela, Odisha, India, spsingh@nitrkl.ac.in 2 M.Tech Student,Civil Engineering Department, NIT Rourkela, India, sushreesangita87@gmail.com 3 Ph.D Student, Department of Civil Engineering, NIT Rourkela, India, 54ce7@nitrkl.ac.in

2 S.P.Singh, J. Sahoo and S.Samantasinghar increase in percentages of NaOH, the strength of granulated blast furnace slag and fly ash increases. But the strength of rice husk ash for seven days of curing decreases from the immediate strength. This may be due to the presence of unburnt carbon in the material. The strength of red mud with 5% NaOH for seven days is higher than the immediate strength and for other percentages, the strength decreases. This shows that there is not enough reactive silica and alumina present in the red mud which can take part in the polymerization process. Moreover addition of more chemicals lubricates the particles and reduces the shearing resistance. The immediate strength of activated slag increase 2.89 and 7.6 times of the virgin slag for 5% and % NaOH respectively. With increase in curing periods, the strength increases and for 28 days curing with % NaOH maximum strength is achieved around 27.5 MPa. It can be concluded from results that reaction between slag and NaOH occurs within 7 days of curing. There is no significant change in strength for 7 days and 28 days. Brittle failure of samples occurs on addition of NaOH. The reaction between alkali and slag is quick which completes with seven days of curing. After 7 days of curing there is no appreciable increase in compressive strength with further curing. Keywords: Industrial solid waste, geopolymer, alkali activation, strength, physico-chemical properties

3 5 th IGC 5 th INDIAN GEOTECHNICAL CONFERENCE 7 th 9 th DECEMBER 25, Pune, Maharashtra, India Venue: College of Engineering (Estd. 854), Pune, India STABILIZATION OF INDUSTRIAL BY-PRODUCTS USING ALKALI ACTIVATION S. P. Singh, Professor, Department of Civil Engineering, NIT Rourkela, Odisha, -spsingh@nitrkl.ac.in J. Sahoo, M.Tech Student, Department of Civil Engineering, NIT Rourkela, -sushreesangita87@gmail.com S. Samantasinghar, Ph.D Student, Department of Civil Engineering, NIT Rourkela, - 54ce7@nitrkl.ac.in ABSTRACT: Utilization of stabilized of waste products in civil engineering construction has gained popularity in recent days. Geo-polymerization of industrial waste products is a recent field of research. In this technique the silica and alumina rich waste products are polymerized using mostly alkali activators. In this study sodium hydroxide is used to activate a number of industrial wastes like rice husk ash, fly ash, blast furnace slag and red mud. The physical, chemical and index properties of these materials are first determined. The compaction characteristics of these materials added with %, 5%, % and 5% of NaOH were determined. It is found that addition of chemical increases the maximum dry density (MDD) whereas the optimum moisture content (OMC) decreases. Further specimens were prepared corresponding to their respective MDD at OMC and cured in a temperature controlled chamber at 27 C for curing periods of 3, 7, 5 and 3 days. All these samples were sealed in order to avoid the moisture loss during curing. The unconfined compressive strength of specimens was determined after specified curing periods. INTRODUCTION With the tremendous growth of industrialization, the production of by-products (such as coal ash, red mud, slag etc.) from the industries also increases. Disposal of waste product is the biggest problem as it requires big expanse of land. Waste products may pollute this land by leaching toxic ingredients as well as pollute the air due to the presence of fine particles in the so called waste products. Many researchers are trying to explore the usability of these waste products by involving latest technologies. One of trending technologies is Geopolymerization. This term Geopolymer was coined by Joseph Davidovits in late 97s. Geopolymerization is a geosynthesis of an inorganic polymer having three dimensional polymeric structure of amorphous to semicrystalline material formed by a chemical heterogeneous exothermic reaction between solid materials rich in alumino-silicate oxides (e.g. fly ash, red mud and slag) and highly alkaline solution under atmospheric pressure and temperatures below C (Giannopoulou et al., 29). In the 98 s Davidovits introduced the sialate nomenclature to describe the aluminosilicate structures. The Si-O-Al was called the sialate bond, and Si-O-Si the siloxo bond. The composition of the geopolymers was hence described by their Si/Al ratio. The different structure were described using the following formula: Mn [-(Si-O 2 )z-al-o]n wh 2 O. Where z(=, 2 or 3) stands for the Si/Al ratio and n is polymerisation degree. There are 3 possible monomeric units which are depicted in Figure 2 are then called for poly(sialate) for z =, poly(sialate-siloxo) for z = 2 and poly(sialatedisiloxo) for z = 3. As per the researches (Davidovits, 982 and Xu, Deventer, 22) done earlier, the synthesis of alkali-alumino silicate material system, the geopolymerization stages can be supposed: () dissolution of alumina and silica from a alumino-silicate material in alkaline

4 S.P.Singh, J. Sahoo and S.Samantasinghar solution results aluminate and silicate species in the liquid phase which are likely to be monomeric; (2) orientation of alumina/silica hydroxyl species and oligomers and diffusion of dissolved ions with formation of small coagulated structures and (3) polycondensation of soluble species forming a three dimensional network of silico-aluminate structures. Depending on the raw material selection and processing conditions, geopolymers can exhibit a wide variety of properties and characteristics, including high compressive strength, low shrinkage, fast or slow setting, acid resistance, fire resistance and low thermal conductivity. LITERATURE REVIEW Mechanical and physico-chemical property Cheng and Chiu (23) tried to fabricate a GGBFS based geopolymer to use in fire resistance purpose. KOH and sodium silicate were used as alkali activator in their research work. GGBFS and metakaolin were taken as raw materials. The samples were cured at 6 o C for 3 hours in an oven and then kept at room temperature for 2 hours before beginning of experiments. With increase in KOH concentration, strength of specimen increases. For N KOH concentration, the strength was achieved maximum of 79 MPa and for concentration more than N, strength got reduced. They also found that with increase in addition of metakaolin, strength increases that are may be due to more availability of Al3 + ions for geopolymeric reaction. Puertas et al. (23) observed strength, mineralogical and microstructural analysis of mortar (comprising activated fly ash/slag mixtures) after cured at different temperatures. Characterization of product is done by X-Ray Diffraction, FTIR, MAS-NMR, Scanning Electron Microscope, EDX, atomic absorption and chromatography. The products found are calcium silicate hydrate rich in aluminium and alkaline aluminium silicate hydrate. Fernandez-Jimenez et al. (25) conducted a study on mechanical strength of alkali activated fly ash mortars with different type of activator. The behavior and microstructure of reaction products were observed. The primary reaction product after activating fly ash was an alkaline aluminosilicate gel. Hydroxyl ion acts as a reaction promoter throughout the geopolymerization, and alkali metal acts as a structure making component. Criado et al. (27) studied the effect of soluble silica on the microstructural development of ashactivator reaction and its effect on mechanical development of material. They concluded major reaction product sodium aluminosilicate gel gives good strength to raw materials. Zeolites are formed as minor products in the reaction. The amount of zeolites rises with curing time for curing temperature of 85 o C. The synthesis parameters like silica content, alkali concentration and solid to liquid ratio affects compressive strength. Mixture of 85% red mud and 5% metakaolin with the aqueous phase (consisting of [SiO 2 ] = 3.5M, [NaOH] = 8M) at S/L ratio 2.9g/mL molded and cured at 6 C for 6 hours and humidity 7% for 66 hours gives compressive strength upto 2.5 MPa, very low cold water absorption (.28%), and excellent water impermeability (cm 3 /cm 2 per day) and the materials demonstrated excellent thermal stability at extremely high temperatures (4 C) (Dimas et al., 29). The RM and RHA based geopolymers vary significantly with finer size of RHA, RHA/RM =.5, and 2M sodium hydroxide solution should have the best mechanical performance. The geopolymers exhibit a compressive strength of MPa, comparable with that of all Portland

5 5 th IGC 5 th INDIAN GEOTECHNICAL CONFERENCE 7 th 9 th DECEMBER 25, Pune, Maharashtra, India Venue: College of Engineering (Estd. 854), Pune, India cement (9-2.7 MPa) except Type III (24. MPa) Portland cement (He and Zhang, 2). MATERIAL Ground Granulated blast furnace slag Ground Granulated Blast Furnace Slag (GGBFS) was collected from Rourkela steel plant. The material was dried in oven to remove the water present in raw material and put in a ball mill to increase the fineness. The material has been sieved through 75 µm was used for the project work. Fly ash Fly ash (FA) for this project work was collected from Adhunik Metaliks Limited, Sudargarh. The material was oven dried and kept in an air tight container for future use. The major constituents of fly ash are silica, alumina and iron. Calcium present in the fly ash is less than 2%. So, according to ASTM specification C (992), this fly ash belongs to a Class F category. Rice husk ash Locally available rice husk ash (RHA) was used to carry out the research work. In this research work, dry RHA were sieved to remove residual bran and clay particles and kept in oven at 5 o C- o C for 24 hours before sample preparation. The rice husk ash used in the present work was collected from the local rice mill. Red mud Red mud (RM) was collected from NALCO, Damanjodi. The material was oven dried and the fineness of the material was increased by putting it in a ball mill. The red mud use in this project work had ph of.2. Sodium hydroxide Sodium hydroxide (NaOH) was used for the alkali activation of the raw materials (i.e. slag, fly ash, rice husk ash, red mud). The sodium hydroxide pellets used for this project were Fisher Scientific brand with 98% purity. The NaOH solution was prepared before 24 hours to ensure proper dissolution of the sodium hydroxide pellets. METHODOLOGY The physical properties if the waste materials were investigated as per relevant Indian Standard (IS 272) specifications as tabulated in Table. The specific gravity of fly ash was determined according to IS: 272 (Part-III, section-) 98 by using pycnometer with distilled water as the solvent. The compaction characteristics of the materials were determined as per IS 272 (Part VII) 98. Four materials were activated by varying percentage of NaOH (i.e. 5%, %, and 5%) of its drying weight. The sodium hydroxide solution was prepared with the starting percentage of water to be added to dry sample for standard proctor test. The solution was kept for 24 hrs. to dissolve the sodium hydroxide pallets properly. As per IS: 272 (Part II) 973 the moisture content of the compacted mixture was determined. From the dry density and moisture content relationship, optimum moisture content (OMC) and maximum dry density (MDD) were determined. For determination of strength of alkali activated raw material at different curing days (day, 7days and 28 days), mm height and 5 mm diameter samples are prepared at OMC and MDD by adding varying percentage of NaOH with oven dried raw material. Unconfined compressive strength tests were conducted as per IS 272 (Part X) 99. The samples were coated with wax and kept for curing at ambient temperature. The UCS tests were conducted on the prefixed curing days. Curing periods for the project work were day, 7 days and 28 days. UCS tests for the determination of immediate strength were conducted within 2hrs after mixing the raw material with alkaline solution.

6 Dry Density (g/cc) Dry Density (g/cc) Dry Density(g/cc) Dry Density(g/cc) S.P.Singh, J. Sahoo and S.Samantasinghar Table. Geo-engineering properties of waste materials Properties FA GGBFS RM RHA Specific gravity, G OMC (%) MDD (g/cc) NaOH % NaOH 5% NaOH % NaOH 5% zav Compressive strength (MPa) RESULT AND DISCUSSION Compaction characteristics Figure to 4 represents the compaction characteristics of slag, fly ash, red mud and rice husk ash with different percentage of NaOH (i.e. %, 5%, %, 5%) respectively. It is observed that with increase in NaOH percentage in the raw material, the optimum moisture content decreases, whereas the maximum dry density increases. This trend is noticed for all the four waste materials. With increase in percentages of NaOH, the materials get more compacted due to the lubricating property of sodium hydroxide gel. The values of the optimum moisture content and maximum dry density for the wastes with NaOH are tabulated in Table Water Content (%) NaOH % NaOH 5% NaOH % Fig. Moisture content-dry density relationship for slag with different % of alkali content zav Water Content(%) Fig. 2 Moisture content- dry density relationship of fly ash at different alkali content NaOH% NaOH5% NaOH% NaOH5% zav Water content(%) Fig. 3 Moisture content- dry density relationship for rice husk ash with different % of alkali content Water Content (%) NaOH % NaOH 5% NaOH % NaOH 5% zav Fig. 4 Moisture content- dry density relationship for red mud with different % of alkali content

7 5 th IGC STRESS(MPa) STRESS(MPa) STRESS(MPa) 5 th INDIAN GEOTECHNICAL CONFERENCE 7 th 9 th DECEMBER 25, Pune, Maharashtra, India Venue: College of Engineering (Estd. 854), Pune, India Table 2. OMC and MDD of raw materials with varying percentages of NaOH Description OMC (%) MDD (g/cc) FA FA+5% NaOH 33.3 FA+% NaOH FA+5% NaOH GGBFS 3.8 GGBFS +5% NaOH GGBFS + % NaOH RM RM +5% NaOH RM +% NaOH 2.86 RM +5% NaOH RHA RHA+ 5% NaOH RHA+ % NaOH RHA+ 5% NaOH Unconfined Compressive Strength Ground granulated blast furnace slag The stress-strain curves for ground granulated blast furnace slag activated with different percentage of activator cured for different period are shown in Figure 5 to Figure 7. The immediate strength of slag with 5% NaOH is 2.89 times more than the strength given by the slag without any activation whereas the strength of the slag sample with % NaOH gives 7.6 times more than raw sample NaOH%D NaOH5%D NaOH%D Fig. 6 Stress- Strain curve of GGBFS with different % NaOH at 7days From the Figure 8, it can be concluded that samples becomes more brittle with curing periods. At 7 days, the strength of samples with 5% NaOH and % NaOH are MPa and MPa respectively which are almost 7 folds of the strength given by the specimens having no chemicals. At 28 days, there are no significance changes in the strength. There was no significance change in development of strength at 28 days curing period NaOH % 7D NaOH 5% 7D NaOH % 7D NaOH%28Days NaOH5%28days NaOH%28days Fig. 5 Stress- Strain curve of GGBFS with different % NaOH at day Fig. 7 Stress- Strain curve of GGBFS with different % NaOH at 28days

8 STRESS (MPa) STRENGTH (MPa) STRESS (MPa) strength (MPa) STRESS(MPa) S.P.Singh, J. Sahoo and S.Samantasinghar % NaOH day 7days 28days Fig. 8 Comparison of strength of GGBFS at different curing periods Fly ash The stress-strain curves for fly ash activated with various percentage of NaOH for different curing period are shown in Figure 9 to Figure. It is observed that, the immediate strength of fly ash with different percentages of NaOH (5%, % and 5%). Strength of samples with 5% NaOH is.55 MPa, which is twice of the strength of raw samples. With increase in curing period, the strength of activated samples increase approximately 2 times compared to raw material. At 28 days curing, the strength achieved with % and 5% NaOH samples is almost same. This indicated that the reactive silica and alumina present in the fly ash sample is consumed with addition of % NaOH and a further increase in NaOH content does not improve the strength NaOH%day NaOH5%day NaOH%day NaOH5%day Fig. 9 Stress- Strain curve of FA ash with different % NaOH at days curing NaOH%7Days NaOH5%7Days NaOH%7Days NaOH5%7Days Fig. Stress- Strain curve of FA with different % NaOH at 7days curing STRAIN 3 (%) Fig. Stress- Strain curve of FA with different % NaOH at 28days curing NaOH%28Days NaOH5%28Days NaOH%28Days NaOH5%28Days 5 5 NaOH % Day 7days 28Days Fig. 2 Comparison of strength of FA at different curing periods Figure 2 shows the comparison of strength gain by specimens at different curing days. From the graph it can be concluded that for 7 days curing, the strength gain by 5% NaOH and % NaOH activated samples are 6 times and 3 times more

9 5 th IGC STRESS (kpa) STRESS (kpa) STRENGTH (KPA) STRESS (kpa) 5 th INDIAN GEOTECHNICAL CONFERENCE 7 th 9 th DECEMBER 25, Pune, Maharashtra, India Venue: College of Engineering (Estd. 854), Pune, India than raw material whereas the gain by 5% NaOH activated samples are 2 folds more. Rice husk ash In case of rice husk ash, the strength of specimens gets reduced after adding NaOH. Ductile failures occur for higher percentages of NaOH as shown in Figure 3 to figure 5. At 28 days curing, the strength of specimen increases as compared to 7 days curing. The specimen gets more bulged during failure NaOH%Day NaOH5%Day NaOH%Day NaOH5%Day Fig. 3 Stress- Strain curve of RHA with different % NaOH at days curing NaOH%7Days NaOH5%7Days NaOH%7Days NaOH5%7Days 5 5 Fig. 4 Stress- Strain curve of RHA with different % NaOH at days curing NaOH%28Days NaOH5%28Days NaOH%28Days NaOH5%28Days Fig. 5 Stress- Strain curve of RHA with different % NaOH at 28 days curing NaOH (%) Day 7days 28Days Fig. 6 Comparison of strength of RHA at different curing periods The change in strength of activated samples with different curing periods is shown in Figure 6. First on the 7 th day of curing, the strength of samples decreases but on the 28th day, it increases slightly. With increase in percentage of NaOH, the strength decreases. Red mud In the case of red mud, the immediate strength of NaOH activated specimen decreases in comparison to non-activated samples. After 7 days of curing period the strength of sample with 5% NaOH increases from the non-activated samples, but for other samples, the strength is not significant. With addition of 5% NaOH, the strength of red mud increases to.8mpa after 7 days curing. For

10 STRESS (MPa) STRESS(MPa) STRESS (MPa)) STRENGTH (MPa) S.P.Singh, J. Sahoo and S.Samantasinghar samples with 5% NaOH, strength decreases with curing periods. The immediate strength of the sample was found to be.2mpa while in case of 28 days curing, it came down to NaOH %Day NaOH5%Day NaOH %Day NaOH5%day NaOH % DAY 7DAYS 28DAYS STRAIN(%) Fig. 7 Stress- Strain curve of RM ash with different % NaOH at days curing NaOH%7Days NaOH5%7Days NaOH%7Days NaOH5%7days STRAIN Fig. 8 Stress- Strain curve of RM with different % NaOH at 7 days curing 'NaOH%28Days' 'NaOH5%28Days' 'NaOH%28Days' NaOH5%28days Fig. 9 Stress- Strain curve of RM with different % NaOH at 28 days curing Fig. 2 Comparison of strength of RM at different curing periods CONCLUSIONS Based on the experimental investigation the following conclusions can be drawn. With increase in percentages of NaOH, the materials get more compacted due to the lubricating property of sodium hydroxide gel. Maximum dry densities of the materials increase with increase in NaOH % while optimum moisture content decreases. For slag, standard proctor test is not feasible for 5% NaOH and the sodium hydroxide solution becomes supersaturated and can t be mixed thoroughly. 2. The immediate strength of activated slag increase 2.89 and 7.6 times of the raw slag for 5% and % NaOH respectively. With increase in curing periods, the strength increases and for 28 days curing with % NaOH maximum strength is achieved around 27.5 MPa. It can be concluded from results that reaction between slag and NaOH occurs within 7 days of curing. There is no significant change in strength for 7 days and 28 days. Brittle failure of samples occurs on addition of NaOH.

11 5 th IGC 5 th INDIAN GEOTECHNICAL CONFERENCE 7 th 9 th DECEMBER 25, Pune, Maharashtra, India Venue: College of Engineering (Estd. 854), Pune, India 3. In case of fly ash, the strength of samples with 5% NaOH is.55 MPa, which is 2 times more than the strength of raw samples. With increase in curing period, the strength of activated samples increase approximately 2 times the non-activated samples. At 28 days curing, for % and 5% NaOH samples, the gain in strength is almost same. 4. Decrease in immediate strength occurs when NaOH is added to Rice husk rice. Strength at 7 days curing is less than the immediate strength due to ongoing reaction between rice husk ash and NaOH. With increase in percentages of NaOH, the specimen bulged more during failure. With increase in curing time, the strength at 28 days increases from 7 days. Presence of carbon i.e. % prohibits the reaction between RHA and NaOH. 5. In case of red mud, increased strength occurs only for 5% NaOH additive at 7 days curing. On the addition of NaOH, the strength declines with curing periods. Decrease in results due to the presence of crystalline phases of material which forbids the reaction between. 6. Sodium hydroxide reacts rapidly with GGBFS than other materials (fly ash, RHA and red mud). The reaction between RHA particles and NaOH is too slow. REFERENCES. Arioz. A, Arioz. O, Kocker. M, An experimental study on the mechanical and microstuctural properties of geopolymer, Procedia Engineering, 42(22), Bakri. AMM, Kamarudin. H, Binhussain. M, Nizar. I, Zarina. Y, Rafiza. AR, The effect of curing temperature on physical and chemical properties of geopolymer, Physics Procedia, 22(2), Cheng. TW, Chiu. JP, Fire-resistant geopolymer produced by granulated blast furnace slag, Minerals Engineering, 6 (23), Criado. M, Fernandez-Jimenez. A, Torre. A, Aranda. M, Palomo, A. An XRD study of the effect of the SiO 2 /Na 2 O ratio on the alkali activation of fly ash, Cement and Concrete Research, 37 (27), Davidovits. J, Properties of geopolymer cements, Proceedings First international conference on Alkali Cements and Concretes, KIEV, Ukraine, 994, Davidovits. J, Geopolymers - chemistry and applications, Institute Geopolymere, Saint- Quentin, Dimas. D, Giannopoulou. I, Panias. D, Polymerization in sodium silicate solutions: a fundamental process in geopolymerization technology, J. Mater Sci., 44 (29), Dimas. D D, Giannopoulou. IP, Panias. D, Utilization of alumina red mud for synthesis of inorganic polymeric materials, Mineral Processing & Extractive Metal. Rev, 3(29), Duxson, P., Fernández-Jiménez, A., Provis, J. L., Lukey, G. C., Palomo, A., & Van Deventer, J. S. J. (27). Geopolymer technology: the current state of the art. Journal of Materials Science, 42(9), Fernandez-Jimenez. A, Palomo. A, and Criado. M, Microstructure development of alkali-activated fly ash cement: a

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