Matching Items (4)
Filtering by
- All Subjects: Aluminum silicates
- Creators: Rajan, Subramaniam D.
Description
The increased emphasis on the detrimental effects of the production of construction materials such as ordinary portland cement (OPC) have driven studies of the alkali activation of aluminosilicate materials as binder systems derived from industrial byproducts. They have been extensively studied due to the advantages they offer in terms of enhanced material properties, while increasing sustainability by the reuse of industrial waste and reducing the adverse impacts of OPC production. Ground granulated blast furnace slag is one of the commonly used materials for their content of calcium and silica species. Alkaline activators such as silicates, aluminates etc. are generally used. These materials undergo dissolution, polymerization with the alkali, condensation on particle surfaces and solidification under the influence of alkaline activators. Exhaustive studies exploring the effects of sodium silicate as an activator however there is a significant lack of work on exploring the effect of the cation and the effect of liquid and powder activators. The focus of this thesis is hence segmented into two topics: (i) influence of liquid Na and K silicate activators to explore the effect of silicate and hydroxide addition and (ii) influence of powder Na and K Silicate activators to explore the effect of cation, concentration and silicates. Isothermal calorimetric studies have been performed to evaluate the early hydration process, and to understand the reaction kinetics of the liquid and powder alkali activated systems. The reaction kinetics had an impact on the early age behavior of these binders which can be explained by the compressive strength results. It was noticed that the concentration and silica modulus of the activator had a greater influence than the cation over the compressive strength. Quantification of the hydration products resultant from these systems was performed via thermo gravimetric analysis (TGA). The difference in the reaction products formed with varying cation and silicate addition in these alkali activated systems is brought out. Fourier transform infrared (FTIR) spectroscopy was used to investigate the degree of polymerization achieved in these systems. This is indicative of silica and alumina bonds in the system. Differences in the behavior of the cation are attributable to size of the hydration sphere and polarizing effect of the cation which are summarized at the end of the study.
ContributorsDakhane, Akash (Author) / Neithalath, Narayanan (Thesis advisor) / Subramaniam, Dharmarajan (Committee member) / Mobashar, Barzin (Committee member) / Arizona State University (Publisher)
Created2013
Description
The studies on aluminosilicate materials to replace traditional construction materials such as ordinary Portland cement(OPC) to reduce the effects caused has been an important research area for the past decades. Many properties like strength have already been studied and the primary focus is to learn about the reaction mechanism and the effect of the parameters on the formed products. The aim of this research was to explore the structural changes and reaction product analysis of geopolymers (Slag & Fly Ash) using Fourier transform infrared spectroscopy (FTIR) and deconvolution
techniques. Spectroscopic techniques give valuable information at a molecular level but not all methods are economic and simple. To understand the mechanisms of alkali activated aluminosilicate materials, attenuated total reflectance (ATR) FTIR has been used where the effect of the parameters on the reaction products have been analyzed. To analyze complex systems like geopolymers using FTIR, deconvolution techniques help to obtain the properties of a particular peak attributed to a certain molecular vibration.
Time and temperature dependent analysis were done on slag pastes to understand the polymerization of reactive silica in the system with time and temperature variance. For time dependent analysis slag has been activated with sodium and potassium silicates using two different `n'values and three different silica modulus [Ms- (SiO2 /M2O)] values. The temperature dependent analysis was done by curing the samples at 60C and 80C. Similarly fly ash has been studied by activating with alkali hydroxides and alkali silicates. Under the same curing conditions the fly ash samples were evaluated to analyze the effects of added silicates for alkali activation.
The peak shifts in the FTIR explains the changes in the structural nature of the matrix and can be identified using the deconvolution technique. A strong correlation is found between the concentrations of silicate monomer in the activating position of the main Si-O-T (where T is Al/Si) stretching band in the FTIR spectrum, which
gives an indication of the relative changes in the Si/Al ratio. Also, the effect of the cation and silicate concentration in the activating solution has been discussed using the Fourier self deconvolution technique.
techniques. Spectroscopic techniques give valuable information at a molecular level but not all methods are economic and simple. To understand the mechanisms of alkali activated aluminosilicate materials, attenuated total reflectance (ATR) FTIR has been used where the effect of the parameters on the reaction products have been analyzed. To analyze complex systems like geopolymers using FTIR, deconvolution techniques help to obtain the properties of a particular peak attributed to a certain molecular vibration.
Time and temperature dependent analysis were done on slag pastes to understand the polymerization of reactive silica in the system with time and temperature variance. For time dependent analysis slag has been activated with sodium and potassium silicates using two different `n'values and three different silica modulus [Ms- (SiO2 /M2O)] values. The temperature dependent analysis was done by curing the samples at 60C and 80C. Similarly fly ash has been studied by activating with alkali hydroxides and alkali silicates. Under the same curing conditions the fly ash samples were evaluated to analyze the effects of added silicates for alkali activation.
The peak shifts in the FTIR explains the changes in the structural nature of the matrix and can be identified using the deconvolution technique. A strong correlation is found between the concentrations of silicate monomer in the activating position of the main Si-O-T (where T is Al/Si) stretching band in the FTIR spectrum, which
gives an indication of the relative changes in the Si/Al ratio. Also, the effect of the cation and silicate concentration in the activating solution has been discussed using the Fourier self deconvolution technique.
ContributorsMadavarapu, Sateesh Babu (Author) / Neithalath, Narayanan (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Marzke, Robert (Committee member) / Arizona State University (Publisher)
Created2014
Description
Sustainable materials and methods have achieved a pivotal role in the research plethora of the new age due to global warming. Cement production is responsible in contributing to 5% of global CO2 emissions. Complete replacement of cement by alkaline activation of aluminosilicate waste materials such as slag and fly ash is a major advancement towards reducing the adverse impacts of cement production. Comprehensive research has been done, to understand the optimized composition and hydration products. The focus of this dissertation is to understand the multiscale behavior ranging from early age properties, fundamental material structure, fracture and crack resistance properties, durability responses and alternative activation methods to existing process.
The utilization of these materials has relied primarily on the dual benefits of reduced presence in landfills and cost. These have also proven to yield a higher service life as opposed to conventional ordinary portland cement (OPC) concrete due to an enhanced microstructure. The use of such materials however has not been readily acceptable due to detrimental early age behavior. The influence of design factors is studied to understand the reaction mechanism. Silicon polymerization at the molecular level is studied to understand the aluminosilicate interactions which are responsible for prevention of any leaching of ions. A comparative study between fly ash and slag binders is carried out to evaluate the stable states of sodium, aluminum and silicon in both these binders, since the likelihood of the sodium ions leaching out is high.
Compressive and flexural strength have been reported in previous literature, but the impact of crack resistance was unevaluated from an approach of characterizing the fracture process zone. Alternative routes of activation are explored with an intent to reduce the high alkalinity by use of neutral salts such as sodium sulfate. High volume OPC replacement by both class C and F fly ash is performed to evaluate the differences in hydration phase formation responsible for its pore refinement and strength. Spectroscopic studies have also allowed to study the fundamental material structure. Durability studies are also performed on these samples to understand the probability external sulfate attacks as opposed to OPC mixes.
The utilization of these materials has relied primarily on the dual benefits of reduced presence in landfills and cost. These have also proven to yield a higher service life as opposed to conventional ordinary portland cement (OPC) concrete due to an enhanced microstructure. The use of such materials however has not been readily acceptable due to detrimental early age behavior. The influence of design factors is studied to understand the reaction mechanism. Silicon polymerization at the molecular level is studied to understand the aluminosilicate interactions which are responsible for prevention of any leaching of ions. A comparative study between fly ash and slag binders is carried out to evaluate the stable states of sodium, aluminum and silicon in both these binders, since the likelihood of the sodium ions leaching out is high.
Compressive and flexural strength have been reported in previous literature, but the impact of crack resistance was unevaluated from an approach of characterizing the fracture process zone. Alternative routes of activation are explored with an intent to reduce the high alkalinity by use of neutral salts such as sodium sulfate. High volume OPC replacement by both class C and F fly ash is performed to evaluate the differences in hydration phase formation responsible for its pore refinement and strength. Spectroscopic studies have also allowed to study the fundamental material structure. Durability studies are also performed on these samples to understand the probability external sulfate attacks as opposed to OPC mixes.
ContributorsDakhane, Akash (Author) / Neithalath, Narayanan (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Mobasher, Barzin (Committee member) / Marzke, Robert (Committee member) / Das, Sumanta (Committee member) / Arizona State University (Publisher)
Created2016
Description
This dissertation aims at developing novel materials and processing routes using alkali activated aluminosilicate binders for porous (lightweight) geopolymer matrices and 3D-printing concrete applications. The major research objectives are executed in different stages. Stage 1 includes developing synthesis routes, microstructural characterization, and performance characterization of a family of economical, multifunctional porous ceramics developed through geopolymerization of an abundant volcanic tuff (aluminosilicate mineral) as the primary source material. Metakaolin, silica fume, alumina powder, and pure silicon powder are also used as additional ingredients when necessary and activated by potassium-based alkaline agents. In Stage 2, a processing route was developed to synthesize lightweight geopolymer matrices from fly ash through carbonate-based activation. Sodium carbonate (Na2CO3) was used in this study to produce controlled pores through the release of CO2 during the low-temperature decomposition of Na2CO3. Stage 3 focuses on 3D printing of binders using geopolymeric binders along with several OPC-based 3D printable binders. In Stage 4, synthesis and characterization of 3D-printable foamed fly ash-based geopolymer matrices for thermal insulation is the focus. A surfactant-based foaming process, multi-step mixing that ensures foam jamming transition and thus a dry foam, and microstructural packing to ensure adequate skeletal density are implemented to develop foamed suspensions amenable to 3D-printing. The last stage of this research develops 3D-printable alkali-activated ground granulated blast furnace slag mixture. Slag is used as the source of aluminosilicate and shows excellent mechanical properties when activated by highly alkaline activator (NaOH + sodium silicate solution). However, alkali activated slag sets and hardens rapidly which is undesirable for 3D printing. Thus, a novel mixing procedure is developed to significantly extend the setting time of slag activated with an alkaline activator to suit 3D printing applications without the use of any retarding admixtures. This dissertation, thus advances the field of sustainable and 3D-printable matrices and opens up a new avenue for faster and economical construction using specialized materials.
ContributorsAlghamdi, Hussam Suhail G (Author) / Neithalath, Narayanan (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Mobasher, Barzin (Committee member) / Abbaszadegan, Morteza (Committee member) / Bhate, Dhruv (Committee member) / Arizona State University (Publisher)
Created2019