scholarly journals Analysis of Changes in the Microstructure of Geopolymer Mortar after Exposure to High Temperatures

Materials ◽  
2020 ◽  
Vol 13 (19) ◽  
pp. 4263
Author(s):  
Marta Dudek ◽  
Mateusz Sitarz
Keyword(s):  
High Temperature ◽  
Fly Ash ◽  
High Temperatures ◽  
Test Results ◽  
Spectroscopy Analysis ◽  
Granulated Blast Furnace Slag ◽  
Current State ◽  
High Durability ◽  
Digital Microscope ◽  
Microstructure Of The Material

The inorganic structure formed at the stage of setting of the geopolymer binder ensures high durability of the material under high-temperature conditions. However, changes in the microstructure of the material are observed. The purpose of the study was to analyze changes in the structure of geopolymer mortar after exposure to high temperatures T = 200, 400, 600, 800, and 1000 °C. Mortars with a binder based solely on fly ash (FA) and mixed in the 1:1 ratio with a binder containing fly ash and ground granulated blast-furnace slag (GGBFS) were tested. The descriptions of their microstructures were prepared based on digital microscope observations, scanning electron microscope (SEM) observations, EDS (energy dispersive spectroscopy) analysis, and mercury intrusion porosimetry (MIP) porosity test results. Changes in the material due to high temperature were observed. The differences in the microstructure of the samples are also visible in the materials that were not exposed to temperature, which was influenced by the composition of the materials. Porosity increases with increasing annealing temperature. The distribution of individual pores also changes. In both materials, the proportion of pores larger than 1000 nm increases with the temperature increase. Moreover, the number of cracks and their width also increases, reaching 20 µm in the case of GGBFS. Furthermore, the color of geopolymers has changed. The obtained results extend the current state of knowledge in the field of changes in the microstructure of geopolymers subjected to high temperature.

The Use of Recycled Aggregate Sludge for the Preparation of GGBFS and Fly Ash Based Geopolymer

Crystals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1486
Author(s):  
Yi-Chen Chen ◽  
Wei-Hao Lee ◽  
Yung-Chin Ding
Keyword(s):  
Fly Ash ◽  
Environmental Concern ◽  
Waste Product ◽  
Recycled Aggregate ◽  
Test Results ◽  
Granulated Blast Furnace Slag ◽  
Mechanical And Physical Properties ◽  
Preliminary Study ◽  
Solid Liquid ◽  
High Treatment

Aggregate sludge is a waste product produced from crushing, screening, and washing processes at aggregate plants. Because of the large quantity and high treatment cost of this sludge, it cannot be disposed of as landfill, and thus, has caused environmental concern over the years in Taiwan. In this preliminary study, the recycled aggregate sludge was reutilized for construction applications through the geopolymerization process. The ground granulated blast furnace slag (GGBFS) and fly ash (FA) were selected as alkaline activated materials for the fabrication of sludge geopolymer. Several process parameters that may affect the mechanical and physical properties of geopolymer were investigated. These parameters are sludge/GGBFS/FA ratios, solid/liquid (alkali solution) ratio, the molarity of NaOH, and curing time. According to the test results, the compressive strength of geopolymer specimens (70/30 sludge/GGBFS ratios) made with 4 M and 6 M NaOH can reach 39.17 MPa and 43.6 MPa after 28 days of curing. The specimen made with 60/40 sludge/GGBFS ratios has a strength of 61.3 MPa. After replacing GGBFS with 10% fly ash (70/20/10 sludge/GGBFS/FA), the strength of the specimen can also reach 43 MPa. According to the test results obtained in this study, it was found that the higher the NaOH concentration, the higher the strength of the geopolymer, and the GGBFS also can contribute more to the mechanical properties of geopolymer than fly ash. This preliminary study suggests that it is possible to reutilize aggregate sludge for construction applications and solve its environmental disposal problem.

Reviews on the Geopolymer Materials for Coating Application

2012 ◽  
Vol 626 ◽  
pp. 958-962 ◽  
Author(s):  
Yahya Zarina ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
H. Kamarudin ◽  
I. Khairul Nizar ◽  
Rafiza Abd Razak
Keyword(s):  
Blast Furnace ◽  
High Temperature ◽  
Fly Ash ◽  
Blast Furnace Slag ◽  
Coating Application ◽  
Existing Structures ◽  
Granulated Blast Furnace Slag ◽  
Temperature Exposure ◽  
New Applications ◽  
Furnace Slag

The application of geopolymer has been expand in many areas where before this it only used for the production of cement and concrete. One of the new applications of geopolymer is for coating. Metakaolin, fly ash and granulated blast furnace slag has been used as source for the production of geopolymer coating. The result for the geopolymer coating showed that it can prevent corrosion in seawater structure, high bonding strength between existing structures (OPC concrete), lower water permeability and also stable during high temperature exposure.

scholarly journals Effect of Cement Type on the Mechanical Behavior and Permeability of Concrete Subjected to High Temperatures

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3021 ◽  
Author(s):  
Izabela Hager ◽  
Tomasz Tracz ◽  
Marta Choińska ◽  
Katarzyna Mróz
Keyword(s):  
High Temperature ◽  
Modulus Of Elasticity ◽  
Experimental Investigations ◽  
Test Results ◽  
Cement Type ◽  
High Temperature Exposure ◽  
Static Modulus ◽  
Granulated Blast Furnace Slag ◽  
Temperature Exposure ◽  
Static Modulus Of Elasticity

The paper presents experimental investigations concerning the influence of the cement type (CEMI 42.5 R Portland cement and CEMIII/A 42.5 N slag cement—with 53% granulated blast furnace slag) on the mechanical and transport properties of heated concretes. The evolution of properties due to high temperature exposure occurring during a fire was investigated. High temperature exposure produces changes in the transport and mechanical properties of concrete, but the effect of cement type has not been widely studied in the literature. In this paper, concretes were made with two cement types: CEMI and CEMIII, using basalt (B) and riverbed aggregates (RB). The compressive and tensile strength, as well as the static modulus of elasticity and Cembureau permeability, were tested after high temperature exposure to 200, 400, 600, 800, and 1000 °C. The evaluation of damage to the concrete and crack development due to high temperature effects was performed on the basis of the change in the static modulus of elasticity. The test results clearly demonstrated that permeability increases with damage, and it follows an exponential type formula for both types of cement.

Durability of Alkali-Activated Fly Ash/Slag Concrete

2017 ◽  
Vol 904 ◽  
pp. 157-161 ◽  
Author(s):  
Mao Chieh Chi ◽  
Hsian Chen ◽  
Tsai Lung Weng ◽  
Ran Huang ◽  
Yih Chang Wang
Keyword(s):  
Fly Ash ◽  
Total Charge ◽  
Test Results ◽  
Mass Ratio ◽  
Modulus Ratio ◽  
Granulated Blast Furnace Slag ◽  
Alkali Activated Binders ◽  
Furnace Slag ◽  
Alkali Activated ◽  
Better Than

This study investigated the durability of alkali-activated binders based on blends of fly ash (FA) and ground granulated blast furnace slag (GGBFS). Five fly ash-to-slag ratios of 100/0, 75/25, 50/50, 25/75, and 0/100 by mass were selected to produce alkali-activated fly ash/slag (AAFS) concrete. Sodium oxide (Na2O) concentrations of 6% and 8% of binder weight and activator modulus ratios (mass ratio of SiO2 to Na2O) of 0.8, 1.0, and 1.23 were used as alkaline activators. Test results show that the total charge passed of AAFS concrete is between 2500 and 4000 coulombs, higher than the comparable OPC concrete. However, AAFS concrete exposed to sulfate attack performed better than OPC concrete. Based on the results, 100% slag-based AAFS concrete with Na2O concentration of 8% and activator modulus ratio of 1.23 has the superior performances.

scholarly journals Strength and Durability Characteristics of Steel Fibre Reinforced Concrete with Mineral Admixtures

2019 ◽  
Vol 9 (1) ◽  
pp. 3893-3897
Keyword(s):  
Reinforced Concrete ◽  
Fly Ash ◽  
Steel Fibre ◽  
Mineral Admixtures ◽  
Fibre Reinforced Concrete ◽  
Test Results ◽  
Split Tensile Strength ◽  
Steel Fibre Reinforced Concrete ◽  
Granulated Blast Furnace Slag ◽  
Strength And Durability

The present investigation is carried out to study the strength and durability characteristics of steel fibre reinforced concrete, by replacing Ordinary Portland cement with Fly Ash, Ground Granulated Blast Furnace Slag (GGBS) and Metakaolin. In this study, cement is replaced by 30% and 40% with Fly Ash, GGBS and Metakaolin for M30 and M35 grades of concrete. Steel fibres @ 1% by weight of binder is used in all the mixes. Strength characteristics like compressive strength and split tensile strength are tested at 7 days and 28 days age. Additionally, durability tests such as water absorption and Sorptivity tests are conducted after 28days curing. The test results have shown that 30% replacement is optimum for strength criteria. And when metakaolin is used with fly ash, durability properties were improved and workability reduced.

Structural Behaviour of Ferrogeopolymer Slabs under Flexure

2016 ◽  
Vol 866 ◽  
pp. 109-113
Author(s):  
Rathinam Kumutha ◽  
Kanagarajan Vijai ◽  
P. Rajeswaran
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Mild Steel ◽  
Double Layers ◽  
Fine Aggregate ◽  
Test Results ◽  
Structural Behaviour ◽  
Granulated Blast Furnace Slag ◽  
Binder Ratio ◽  
The Individual

The main objective of this paper was to present the results of experimental investigation carried out to study the structural behaviour of ferrogeopolymer elements under flexure. Initially the properties of geopolymeric binder prepared using the source materials such as Fly ash and Ground Granulated Blast Furnace Slag (GGBS) without conventional cement have been investigated. The different parameters considered in this study are the ratio of binder to fine aggregate (1:2 and1:3) and the ratio of Na2SiO3 to NaOH solutions (2.0 and 2.5). The various combinations of Fly ash and GGBS considered are 90% & 10% and 80% & 20%. The alkaline liquid to binder ratio is fixed as 0.45. The individual properties of mortar such as Compressive Strength and Density were determined as per relevant Indian standards. The geopolymer concrete mix that gives the highest compressive strength was used to cast the ferrogeopolymer structural slabs. Four numbers of rectangular slabs of size 800 mm x 300 mm x 25 mm were prepared with two types of meshes such as mild steel and galvanized iron weld mesh with single and double layers. Based on the test results Load-Deflection curves were drawn and the effectiveness of mild steel and galvanized iron weld meshes was compared from the characteristics such as first crack load, ultimate load, energy absorption and ductility.

Durability of Sustainable Self-Consolidating Concrete

2018 ◽  
Vol 765 ◽  
pp. 285-289
Author(s):  
Osama Ahmed Mohamed ◽  
Waddah Al Hawat ◽  
Omar Fawwaz Najm
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Silica Fume ◽  
Cementitious Materials ◽  
Chloride Penetration ◽  
Supplementary Cementitious Materials ◽  
Test Results ◽  
Self Consolidating Concrete ◽  
Human Footprint ◽  
Granulated Blast Furnace Slag

Supplementary cementitious materials such as fly ash, silica fume and ground granulated blast furnace slag (GGBS) have been used widely to partially replace cement in producing self-consolidating concrete (SCC). The production of cement is associated with emission of significant amounts of CO2 and increases the human footprint on the environment. Fly ash, silica fume, and GGBS are recycled industrial by-products that also impart favorable fresh and hardened properties on concrete. This study aims to assess the effect of the amounts of fly ash and silica fume on strength and chloride penetration resistance of concrete. Rapid Chloride Penetration Test (RCPT) was used to assess the ability of SCC to resist ingress of chlorides into concrete. SCC mixes with different dosages of fly ash and silica fume were developed and tested at different curing ages. Test results showed that replacing 20% of cement with fly ash produced the highest compressive strength of 67.96 MPa among all fly ash-cement binary mixes. Results also showed that replacing15% of cement with silica fume produced the highest compressive strength of 95.3 MPa among fly ash-cement binary mixes. Using fly ash and silica fume consistently increased the concrete resistance to chloride penetration at the early ages. Silica fume at all dosages results in low or very low levels of chloride penetration at all curing ages of concrete.

scholarly journals Effects of Combined Usage of Supplementary Cementitious Materials on the Thermal Properties and Microstructure of High-Performance Concrete at High Temperatures

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1833 ◽  
Author(s):  
Dong Lu ◽  
Zhuo Tang ◽  
Liang Zhang ◽  
Jianwei Zhou ◽  
Yue Gong ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
High Temperature ◽  
Fly Ash ◽  
High Temperatures ◽  
High Performance ◽  
High Performance Concrete ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Amorphous Phases ◽  
Micro Cracks

Concrete has low porosity and compact microstructure, and thus can be vulnerable to high temperature, and the increasing application of various types of supplementary cementitious materials (SCMs) in concrete makes its high-temperature resistant behavior more complex. In this study, we investigate the effects of four formulations with typical SCMs combinations of fly ash (FA), ultra-fine fly ash (UFFA) and metakaolin (MK), and study the effects of SCMs combinations on the thermal performance, microstructure, and the crystalline and amorphous phases evolution of concrete subjected to high temperatures. The experimental results showed that at 400 °C, with the addition of 20% FA (wt %), the thermal conductivity of the sample slightly increased to 1.5 W/(m·K). Replacing FA with UFFA can further increase the thermal conductivity to 1.7 W/(m·K). Thermal conductivity of concrete slightly increased at 400 °C and significantly reduced at 800 °C. Further, combined usage of SCMs delayed and reduced micro-cracks of concrete subjected to high temperatures. This study demonstrates the potential of combining the usage of SCMs to promote the high-temperature performance of concrete and explains the micro-mechanism of concrete containing SCMs at high temperatures.

scholarly journals High Temperature Coatings for Protection Against Turbine Deterioration

1993 ◽  
Author(s):  
W. Tabakoff ◽  
M. Metwally ◽  
A. Hamed
Keyword(s):  
High Temperature ◽  
Fly Ash ◽  
High Temperatures ◽  
Erosion Rate ◽  
Wind Erosion ◽  
Protective Coatings ◽  
Impact Angle ◽  
Steam Turbines ◽  
Erosion Behavior ◽  
The Impact

In this research, an investigation was conducted to study the fly ash particles associated with the erosion behavior of alloys and coatings which are widely used in gas and steam turbines. The erosion behavior of many alloys and protective coatings has been investigated experimentally at high temperatures using a specially designed wind erosion tunnel. The erosion results show the effect of velocity, temperature and the impact angle on the erosion rate.

POSSIBILITIES OF DETERMINATION OF OPTIMAL DOSAGE OF POWER PLANT FLY ASH FOR CONCRETE

2016 ◽  
Vol 78 (5-3) ◽  
Author(s):  
Rudolf Hela ◽  
Martin Tazky ◽  
Lenka Bodnarova
Keyword(s):  
High Temperature ◽  
Fly Ash ◽  
Partial Replacement ◽  
Optimal Dosage ◽  
Test Results ◽  
Temperature Combustion ◽  
High Production ◽  
Positive Effect ◽  
High Temperature Combustion

The paper describes possibilities of making use of high temperature combustion fly ash for production of concrete more effective. Efforts for maximal utilization of high temperature combustion fly ash are supported by high production of fly ash worldwide. Use of high temperature fly ash for concrete has to take into account considerably lower speed of hydration reactions compared to pure Portland cement. The paper states results of experimental determination of optimal dosage of fly ash as partial replacement of cement. Dosage of fly ash for production of concrete was optimized. Test results proved positive effect of dosage of fly ash with respect to granulometry of used cement and fly ash. Taking granulometry of fly ash and cement into consideration improves physico-mechanical properties of concrete compared to concrete with fly ash designed standardly without considering granulometry. 

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