Showing 6 results for Geopolymer
A. Allahverdi, E. Najafi Kani,
Volume 6, Issue 2 (6-2009)
Abstract
geopolymer cement (inorganic polymeric binder) based on natural pozzolan are investigated. SiO
of activator and total molar ratios of Nacomposition exhibiting the highest 28-day compressive strength. Mixtures exhibiting the highest compressive strength were studied for their molecular structure using laboratory technique of Fourier transform infrared spectroscopy.Results obtained confirm that changes in chemical composition and curing condition can result in variations in degree of silicon substitution by aluminum in the second coordination sphere. Hydrothermal curing affects the molecular structure so that by increasing the hydrothermal curing temperatures, a lower degree of silicon substitution by aluminum in the second coordination sphere is observed. The molecular structure of the studied inorganic polymeric binde is composed of Si-O-Si chains bonded to Al-O and Si-O units creating two and three dimensional networks.
In this paper, the effects of chemical composition and curing conditions on molecular structure of2/Na2O molar ratio2O/Al2O3, and H2O/Al2O3 were changed to determine the optimum chemical
E. Najafi Kani, A. Allahverdi,
Volume 8, Issue 3 (9-2011)
Abstract
Shrinkage behavior of a geopolymer cement paste prepared from pumice-type natural pozzolan was studied
by changing parameters of chemical composition including SiO2/Na2O molar ratio of activator and total molar ratios
of Na2O/Al2O3, and H2O/Al2O3. For investigating the effect of curing conditions on shrinkage, hydrothermal curing
was also applied. The obtained results clearly revealed the governing effect of chemical composition on shrinkage.
Mixes with different Na2O/Al2O3 molar ratios exhibited different shrinkage behavior due to variations made in
SiO2/Na2O molar ratio. Application of hydrothermal curing after a 7-day period of precuring in humid atmosphere
also showed strong effect on shrinkage reduction.
M. A. Soleimani, R. Naghizadeh, A. R. Mirhabibi, F. Golestanifard ,
Volume 9, Issue 4 (12-2012)
Abstract
Metakaolinite-based geopolymer has been synthesized at about 25 °C from metakaolin which has been calcined in different temperatures (600-900 °C) and different Na2O/SiO2 ratio activator (0.3-1.1). Compressive strength and microstructure of cement pastes after 7-28 days curing at ambient temperature were measured. Compressive strength tests on the samples showed that the sample made with calcined kaolin at 700 °C and molar ratio of 0.6 has highest average compressive strength of 32 MPa after 28 days of curing. Evaluation of infrared spectroscopy (FTIR) and microstructure showed that geopolymer cement developed and new molecular structure established
A. Nogueira, S. de Barros, L. Alves,
Volume 17, Issue 3 (9-2020)
Abstract
The construction sector is responsible for relevant environmental impacts and one of its most crucial points is the use of concrete. Geopolymers represent the most promising green and ecological alternative for common Portland cement and cementitious materials, due to its proven durability, mechanical and thermal properties. This work presents an experimental and comparative study of adhesion at the fiber-matrix interface between glass fibers and carbon fibers added to the geopolymer matrix. This analysis was performed by pull-out test, whereby it was found that the greatest efficiency was obtained by reinforcing with the glass fibers, incorporated at 2 mm in the geopolymer matrix. As results, the adhesion between the fibers and the geopolymer structure can be assessed, as well as the optimum length of application.
R.s Krishna, J. Mishra, A. Adeniji, Sh. Das, S. Mohammed Mustakim,
Volume 17, Issue 4 (12-2020)
Abstract
The field of nanomaterial has greatly advanced in the last decade following a wider range of applications in the fields of electronics, automobiles, construction, and healthcare due to its extraordinary and ever-evolving properties. Synthesis of the nanomaterial plays a crucial role in redefining the current engineering and science field. At the same time, procuring an environment-friendly end product through eco-friendly solutions and sustainable processes is the key to many global problems. Green synthesis of nanomaterials like graphene and its derivatives involves mild reaction conditions and nontoxic precursors because it is simple, cost-effective, relatively reproducible, and often results in more stable materials. This paper primarily focuses on the green synthesis of graphene and its derivatives (graphene oxide & reduced graphene oxide) and geopolymers; a green technology for preparing graphene reinforced geopolymer composites. Various methods used globally for green synthesis of graphene and geopolymer are briefly discussed and this paper tries to integrate these two areas for a green end product. Possible applications of these green composites are also discussed to provide insights on the current growth and developments.
Ekaterina Dmitrieva, Ivan Korchunov, Ekaterina Potapova, Sergey Sivkov, Alexander Morozov,
Volume 19, Issue 4 (12-2022)
Abstract
The article discusses the effect of calcined clays on the properties of Portland cement. An optimal method for calcining clays is proposed, which makes it possible to reduce the proportion of Portland cement clinker in cement to 60% and increase the strength characteristics from 55 MPa to 79 MPa. The study of the composition and structure of clays made it possible to select the optimal heat treatment parameters, at which the calcination products are characterized by the highest pozzolanic activity. It is shown that the use of alkali-activated calcined clays significantly increases the strength and durability of hardened cement binders compared to the composition without additives. In addition, calcined clays increase the frost resistance of cement in a 5% NaCl solution. The obtained experimental data are confirmed by thermodynamic calculations and the results of scanning electron microscopy.
