scholarly journals Influence of the fly ash and the prior freezing and thawing on the sulphate resistance of cement mortars

2018 ◽  
Vol 174 ◽  
pp. 02004
Author(s):  
Julia Marczewska
Keyword(s):  
Fly Ash ◽  
Cement Composites ◽  
Sulphate Attack ◽  
Freezing And Thawing ◽  
Natural Conditions ◽  
Air Voids ◽  
Cement Mortars ◽  
Reduction Of Energy Consumption ◽  
Reduction Of Co2 ◽  
By Products

The use of fly ash for the production of cement is a typical example of the utilization of by-products (waste) from various fields of production in construction, a significant reduction of CO2 emissions and reduction of energy consumption. However, in order to be able to determine the suitability of this additive in construction, it is necessary to examine the durability of cement composites with fly ash in various, often complicated, destructive environments. There are known publications regarding the durability of concretes with fly ash in individual environments. However, in natural conditions, several destructive environments are common at the same time. The article presents an attempt to reproduce natural conditions. This paper presents the results of sulphate expansion tests of air-entrained (AE) and non-air-entrained (nAE) Portland and fly ash cement mortars subjected to prior freezing and thawing. Despite significant strains experienced during freeze-thaw cycles, unlike the non-air-entrained Portland cement mortars, the non-air-entrained mortars made of fly ash cement did not exhibit any significant expansion when exposed to Na2SO4. For 17 months no expansion was found in the air-entrained mortars made of either of the cement types when immersed in Na2SO4solution after freezethaw cycles. The results of the SEM and EDS analyses showed that gypsum and ettringite were the sulphate attack products in all the mortars. The highest amounts of ettringite were found in air voids.

scholarly journals The Influence of Cement Substitution by Biomass Fly Ash on the Polymer–Cement Composites Properties

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3079
Author(s):  
Beata Jaworska ◽  
Dominika Stańczak ◽  
Joanna Tarańska ◽  
Jerzy Jaworski
Keyword(s):  
Fly Ash ◽  
Building Materials ◽  
Raw Materials ◽  
Combustion Process ◽  
Biomass Combustion ◽  
Cement Composites ◽  
Cement Mortars ◽  
Mineral Additive ◽  
Biomass Fly Ash

The generation of energy for the needs of the population is currently a problem. In consideration of that, the biomass combustion process has started to be implemented as a new source of energy. The dynamic increase in the use of biomass for energy generation also resulted in the formation of waste in the form of fly ash. This paper presents an efficient way to manage this troublesome material in the polymer–cement composites (PCC), which have investigated to a lesser extent. The research outlined in this article consists of the characterization of biomass fly ash (BFA) as well as PCC containing this waste. The characteristics of PCC with BFA after 3, 7, 14, and 28 days of curing were analyzed. Our main findings are that biomass fly ash is suitable as a mineral additive in polymer–cement composites. The most interesting result is that the addition of biomass fly ash did not affect the rheological properties of the polymer–cement mortars, but it especially influenced its compressive strength. Most importantly, our findings can help prevent this byproduct from being placed in landfills, prevent the mining of new raw materials, and promote the manufacture of durable building materials.

scholarly journals The Influence of Crystalline Admixtures on the Properties and Microstructure of Mortar Containing By-Products

Buildings ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 146
Author(s):  
Jakub Hodul ◽  
Nikol Žižková ◽  
Ruben Paul Borg
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Chloride Ion ◽  
Capillary Suction ◽  
Chloride Ion Penetration ◽  
Chloride Migration ◽  
Cement Mortars ◽  
Polymer Mortar ◽  
By Products ◽  
Ion Penetration

Crystalline admixtures and industrial by-products can be used in cement-based materials in order to improve their mechanical properties. The research examined long-term curing and the exposure to environmental actions of polymer–cement mortars with crystalline admixture (CA) and different by-products, including Bengħisa fly ash and Globigerina limestone waste filler. The by-products were introduced as a percentage replacement of the cement. A crystallization additive was also added to the mixtures in order to monitor the improvement in durability properties. The mechanical properties of the mortar were assessed, with 20% replacement of cement with fly ash resulting in the highest compressive strength after 540 days. The performance was analyzed with respect to various properties including permeable porosity, capillary suction, rapid chloride ion penetration and chloride migration coefficient. It was noted that the addition of fly ash and crystalline admixture significantly reduced the chloride ion penetration into the structure of the polymer cement mortar, resulting in improved durability. A microstructure investigation was conducted on the samples through Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDS). Crystals forming through the crystalline admixture in the porous structure of the material were clearly observed, contributing to the improved properties of the cement-based polymer mortar.

scholarly journals Influence of Fly Ash From Co-Combustion of Coal and Biomass on Scaling Resistance of Concrete / Wpływ Popiołu Lotnego Ze Współspalania Wegla I Biomasy Na Odpornosc Betonu Na Powierzchniowe Łuszczenie

2010 ◽  
Vol 56 (3) ◽  
pp. 239-254 ◽  
Author(s):  
M. Kosior-Kazberuk ◽  
D. Józwiak-Niedzwiedzka
Keyword(s):  
Fly Ash ◽  
Cost Effective ◽  
Hard Coal ◽  
Freezing And Thawing ◽  
Air Voids ◽  
Freeze Thaw ◽  
Industrial Utilization ◽  
Concrete Production ◽  
Fly Ash Utilization

Abstract Industrial utilization of fly ash from various kinds of fuel plays an important role in the environmentally clean and cost effective power production. The primary market for fly ash utilization is as a pozzolanic addition in concrete production. The paper concerns the concretes containing fly ash called Fly Ash from Biomass (FAB) from co-combustion of hard coal and wood biomass (wood chips). Characterization of the fly ash was carried on by means of X-ray diffractometry and E-SEM/EDS analysis. The results of laboratory studies undertaken to evaluate the influence of FAB on concrete resistance to surface scaling due to cyclic freezing and thawing in the presence of NaCl solution were presented. The tests were carried out for concretes containing up to 25% of fly ash related to cement mass. Additionally, the microstructure of air-voids was described. It was concluded that the FAB has significant effect on concrete freeze/thaw durability. The replacement of cement by fly ash from co-combustion progressively transformed the concrete microstructure into less resistant against freeze/thaw cycles and excessive dosage (over 15%) may dangerously increase the scaling.

scholarly journals Coal ash Portland Cement Mortars Sulphate Resistance

2021 ◽  
Vol 7 (1) ◽  
pp. 98-106
Author(s):  
Esperanza Menéndez ◽  
Cristina Argiz ◽  
Miguel Ángel Sanjuán
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Coal Fly Ash ◽  
Electrical Power ◽  
Bottom Ash ◽  
Coal Ash ◽  
Sodium Sulphate ◽  
Sulphate Attack ◽  
Coal Bottom Ash ◽  
Cement Mortars

Coal fly ash (CFA), coal bottom ash (CBA) are residues produced in thermo-electrical power stations as result of the coal combustion in the same boiler. Therefore, some characteristics of the coal fly ash (CFA) are comparable with those of the coal bottom ash (CBA). Nevertheless, coal bottom ash size is larger than coal fly ash one. Consequently, it was found that it is necessary to grind the coal bottom ash (CBA) to reach a similar size to that one of the CFA. The objective of this paper is to evaluate the performance of Portland cement mortars made with coal fly ash (CFA), coal bottom ash (CBA) or mixes (CFA+CBA), against sulphate attack. The methodology is based on the expansion of slender bars submerged in a sodium sulphate solution (5%) according to the ASTM C-1012/C1012-13 standard. It has been found that mortars elaborated with CEM I 42.5 N (without ashes) presented the largest expansion (0.09%) after a testing period of 330 days. Mortars made with CEM II/A-V exhibited lower expansion (0.03%). Summing up, it can be established that mortar expansion decreases when the coal ash amount increases, independently of the type of coal ash employed. The novelty of this paper relies on the comparison between the performances of Portland cement mortars made with coal fly ash (CFA) or coal bottom ash (CBA) exposed to external sulphate attack. Doi: 10.28991/cej-2021-03091640 Full Text: PDF

scholarly journals Effect of Polymer Addition on Performance of Portland Cement Mortar Exposed to Sulphate Attack

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 71 ◽  
Author(s):  
Paweł Łukowski ◽  
Dominika Dębska
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Chemical Resistance ◽  
Cement Mortar ◽  
Cement Composites ◽  
Distilled Water ◽  
Sulphate Attack ◽  
Polymer Addition ◽  
Cement Mortars ◽  
Time Changes

Resistance to degradation contributes greatly to the durability of materials. The chemical resistance of polymer-cement composites is not yet fully recognized. The goal of the research presented in this paper was to assess the performance of polymer-cement mortars under sulphate aggression, as compared to unmodified cement mortar. Mortars with polymer-to-cement ratios from 0 to 0.20 were stored in either a 5% MgSO4 solution or distilled water for 42 months. During this time, changes in elongation, mass, and compressive strength were determined. The results of these investigations, together with the visual and microscopic observations, allowed us to conclude that polymer–cement composites demonstrated better resistance to the attack of sulphate ions than unmodified cement mortar, even when using Portland cement with enhanced sulphate resistance.

The Influence of the Ash Addition from Thermal Power Plant on the Mechanical, Thermal and Dielectric Characteristics of Mortars

2018 ◽  
Vol 69 (8) ◽  
pp. 2040-2044
Author(s):  
Georgeta Velciu ◽  
Virgil Marinescu ◽  
Adriana Moanta ◽  
Ladislau Radermacher ◽  
Adriana Mariana Bors
Keyword(s):  
Thermal Conductivity ◽  
Fly Ash ◽  
Power Plant ◽  
Cement Mortar ◽  
Thermal Power ◽  
Total Content ◽  
Ash Content ◽  
Dielectric Losses ◽  
Dielectric Characteristics ◽  
Cement Mortars

The influence of fly ash adittion (90 % fraction [ 100 mm) on the cement mortar characteristics was studied. The XRD, XRF, SEM and FTIR determinations indicated that fly ash used has a hollow microstructure of microsphere and cenosphere whose total content in SiO2, Al2O3 and Fe2O3 is 88.63 % and that of CaO and MgO of 8.55 %. The mechanical, thermal and dielectric determinations made on mortar samples with content of fly ash in the 0-40 % range have highlighted fact that the mechanical strength of cement mortars is maximal at 20 %, the increase in fly ash content leads to a decrease in relative density and thermal conductivity as well as and to increased dielectric losses tgd.

Determination of optimal microwave curing cycle for fly ash mortars

2008 ◽  
Vol 35 (4) ◽  
pp. 349-357 ◽  
Author(s):  
İlker Bekir Topçu ◽  
Mehmet Uğur Toprak ◽  
Devrim Akdağ
Keyword(s):  
Fly Ash ◽  
Processing Parameters ◽  
Microwave Energy ◽  
Strength Prediction ◽  
Strength Development ◽  
Microwave Curing ◽  
Optimal Processing ◽  
Cement Mortars ◽  
Curing Cycle

Microwave energy can accelerate the hydration of cement, which results in the rapid strength development of concrete. In this paper, prediction of later age compressive strength of fly ash cement mortars, based on the accelerated strength of mortars cured with microwave energy, was investigated. To accelerate curing properly, optimal processing parameters of microwave curing (MC) on Portland cement mortars (CM) and fly ash cement mortars (FA) were first determined and then were applied to mortars. The possible early ages for the strength prediction were found to be at 6 and 8 h for CM and FA, respectively. The error percentages for prediction of CM were ±2.22% and 2.91% for 7 and 28 d, respectively. Error percentages for FA, on the other hand, were ±4.36% and 5.20% for 7 and 28 d, respectively.

The Latest Research in Mongolia on the Utilization of Coal Combustion By-Products

2021 ◽  
Vol 323 ◽  
pp. 8-13
Author(s):  
Jadambaa Temuujin ◽  
Damdinsuren Munkhtuvshin ◽  
Claus H. Ruescher
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Coal Combustion ◽  
Power Plants ◽  
Thermal Power ◽  
Thermal Power Plants ◽  
Power Stations ◽  
Thermal Power Stations ◽  
Coal Ashes ◽  
By Products

With a geological reserve of over 170 billion tons, coal is the most abundant energy source in Mongolia with six operating thermal power stations. Moreover, in Ulaanbaatar city over 210000 families live in the Ger district and use over 800000 tons of coal as a fuel. The three thermal power plants in Ulaanbaatar burn about 5 million tons of coal, resulting in more than 500000 tons of coal combustion by-products per year. Globally, the ashes produced by thermal power plants, boilers, and single ovens pose serious environmental problems. The utilization of various types of waste is one of the factors determining the sustainability of cities. Therefore, the processing of wastes for re-use or disposal is a critical topic in waste management and materials research. According to research, the Mongolian capital city's air and soil quality has reached a disastrous level. The main reasons for air pollution in Ulaanbaatar are reported as being coal-fired stoves of the Ger residential district, thermal power stations, small and medium-sized low-pressure furnaces, and motor vehicles. Previously, coal ashes have been used to prepare advanced materials such as glass-ceramics with the hardness of 6.35 GPa, geopolymer concrete with compressive strength of over 30 MPa and zeolite A with a Cr (III) removal capacity of 35.8 mg/g. Here we discuss our latest results on the utilization of fly ash for preparation of a cement stabilized base layer for paved roads, mechanically activated fly ash for use in concrete production, and coal ash from the Ger district for preparation of an adsorbent. An addition of 20% fly ash to 5-8% cement made from a mixture of road base gave a compressive strength of ~ 4MPa, which exceeds the standard. Using coal ashes from Ger district prepared a new type of adsorbent material capable of removing various organic pollutants from tannery water was developed. This ash also showed weak leaching characteristics in water and acidic environment, which opens up an excellent opportunity to utilize.

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