Self-sensing performance of metakaolin geopolymer with carbon nanotubes subjected to repeated compressive loading

Alkaline activated binders showing enhanced piezoresistive properties have recently attracted increased interest in research of their application in smart self-sensing components. This study is focused on metakaolin geopolymer mortar doped with 0.05 and 0.10% carbon nanotubes, a conductive filler that effectively increases electrical conductivity without considerable deterioration of mechanical properties. Self-sensing performance of composites incorporated with electrodes and attached strain gauge was tested during different regimes of compressive loading cycles with continuous monitoring of strain and resistivity. Although the differences in sensitivity and repeatability were observed, all samples including the reference material have shown good response to applied loading.

Synthesis and Thermal Treatment of Lithium- and Magnesium-Containing Geopolymers

<p>Geopolymers are a class of cementitious aluminosilicate materials that are receiving an increasing amount of attention due to their potential applications in toxic waste remediation and as construction materials. They are composed of a network of crosslinked silicate and aluminate tetrahedra with charge-balancing alkali cations and are therefore similar in composition to alkali aluminosilicate zeolites. They are, however, x-ray amorphous.¹⁻⁴ They are formed by the dissolution of a solid aluminosilicate in a solution of alkali hydroxide or alkali silicate to form aluminosilicate ions which subsequently polymerise. The effects of adding magnesium to metakaolin geopolymer systems was examined. Magnesium was added as soluble magnesium salts and as magnesium oxide and hydroxide. When added as a soluble salt, an amorphous magnesium (alumino)silicate with a lower degree of silicate polymerisation than a geopolymer is formed. When added as the oxide or hydroxide, hydrotalcite is formed. In both cases, the product is produced alongside a separate geopolymer phase. A magnesiumcontaining geopolymer phase was not found in either. When heated to 1200°C, geopolymers with magnesium oxide added bloated to form lightweight foams. Lithium analogues of conventional metakaolin geopolymer systems with a range of lithium, aluminium, silicon and water contents were examined. Systems with molar ratios similar to those of commonly studied sodium and potassium metakaolin geopolymers produce self-pelletised lithium zeolites. The zeolite formed was Li-EDI, the lithium analogue of zeolite F. This is the first reported synthesis directly from metakaolin. True lithium geopolymers are found not to form in the systems examined. The zeolite bodies react to form β-eucryptite and β-spodumene at temperatures from 800 – 1350°C. The use of aluminium hydroxide and amorphoud silica rather than aluminosilicates as raw materials for the formation of potassium geopolymers was found to produce geopolymers with embedded grains of unreacted silica and aluminium hydroxide.</p>

Synthesis and Thermal Treatment of Lithium- and Magnesium-Containing Geopolymers

<p>Geopolymers are a class of cementitious aluminosilicate materials that are receiving an increasing amount of attention due to their potential applications in toxic waste remediation and as construction materials. They are composed of a network of crosslinked silicate and aluminate tetrahedra with charge-balancing alkali cations and are therefore similar in composition to alkali aluminosilicate zeolites. They are, however, x-ray amorphous.¹⁻⁴ They are formed by the dissolution of a solid aluminosilicate in a solution of alkali hydroxide or alkali silicate to form aluminosilicate ions which subsequently polymerise. The effects of adding magnesium to metakaolin geopolymer systems was examined. Magnesium was added as soluble magnesium salts and as magnesium oxide and hydroxide. When added as a soluble salt, an amorphous magnesium (alumino)silicate with a lower degree of silicate polymerisation than a geopolymer is formed. When added as the oxide or hydroxide, hydrotalcite is formed. In both cases, the product is produced alongside a separate geopolymer phase. A magnesiumcontaining geopolymer phase was not found in either. When heated to 1200°C, geopolymers with magnesium oxide added bloated to form lightweight foams. Lithium analogues of conventional metakaolin geopolymer systems with a range of lithium, aluminium, silicon and water contents were examined. Systems with molar ratios similar to those of commonly studied sodium and potassium metakaolin geopolymers produce self-pelletised lithium zeolites. The zeolite formed was Li-EDI, the lithium analogue of zeolite F. This is the first reported synthesis directly from metakaolin. True lithium geopolymers are found not to form in the systems examined. The zeolite bodies react to form β-eucryptite and β-spodumene at temperatures from 800 – 1350°C. The use of aluminium hydroxide and amorphoud silica rather than aluminosilicates as raw materials for the formation of potassium geopolymers was found to produce geopolymers with embedded grains of unreacted silica and aluminium hydroxide.</p>

Thermal, X-ray Diffraction and Oedometric Analyses of Silt-Waste/NaOH-Activated Metakaolin Geopolymer Composite

The present research investigates the possibility to create a silt-waste reinforced composite through a NaOH-activated, metakaolin-based geopolymerization process. In this regard, we used thermal exo–endo analysis, X-ray diffraction (XRD), and oedometric mechanical tests to characterize the produced composites. In our experimental conditions, the tested material mixtures presented exothermic peaks with maximum temperatures of about 100 °C during the studied geopolymerization process. In general, the XRD analyses showed the formation of amorphous components and new mineral phases of hydrated sodalite, natrite, thermonatrite and trona. From oedometric tests, we observed a different behavior of vertical deformation related to pressure (at RT) for the various produced composites. The present work indicated that the proposed geopolymerization process to recycle silt-waste produced composite materials with various and extended mineralogy and chemical–physical properties, largely depending on both the precursors and the specific alkaline-activating solution. Thermal analysis, XRD, and oedometric mechanical tests proved to be fundamental to characterize and understand the behavior of the newly formed composite material.

An Investigation of Different Factors On Durability of Metakaolin Geopolymer Cement Mortar

In the preliminary part of this research, orthogonal experiments were conducted to identify metakaolin admixture and activator content as the two main influencing factors through four factors that mainly affected the basic properties of metakaolin geopolymer specimens. It is crucial to study the durability of construction materials under harsh environments. Therefore, this experiment mainly tested the anti-permeability, sulfate corrosion resistance, and freezing-thawing resistance of metakaolin geopolymer pastes with different ratio of metakaolin admixture and alkali activators content.The results indicated that with the changes of metakaolin and activator content,both of two anti-permeability curves increased firstly and then decreased.The sulfate corrosion resistance showed that both weight loss curves firstly decreased and then increased trend.Corrosion resistance curves increased first and then decreased in different curing time.Freezing-thawing resistance tests indicated that weight loss rate and strength loss rate declined and then ascended.Moreover,the microscopic SEM and FT-IR experiments were used to more directly reflect the patterns of durability changes.