scholarly journals Effect of Vietnamese Fly Ash on Selected Physical Properties, Durability and Probability of Corrosion of Steel in Concrete

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 593 ◽  
Author(s):  
Chinh Van Nguyen ◽  
Paul Lambert ◽  
Quang Hung Tran
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Acid Resistance ◽  
Steel Corrosion ◽  
Strength Loss ◽  
Reinforced Concrete Beams ◽  
Partial Replacement ◽  
Nacl Solution ◽  
Fly Ash Concrete ◽  
Corrosion Of Steel

Vietnamese fly ash was used as a partial replacement for ordinary Portland cement in the proportions of 10%, 20% and 40%, while the water to cementitious ratios were kept constant at 0.42, 0.5 and 0.55, respectively, for three groups. The compressive strengths of all mixes were determined up to 90 days. The acid resistance of fly ash concrete was examined by the mass loss and compressive strength loss of 100 × 100 × 100 mm3 cubes immersed in a 10% H2SO4 solution. The probability of steel corrosion in the fly ash concrete was assessed by measuring the half-cell potentials of steel bars within beams dimensions of 100 × 100 × 500 mm3, and the flexural strengths of these beams after 300 days of immersion in a 5% NaCl solution were determined. The results demonstrate that the compressive strength of fly ash concrete is reduced at an early age but increases as the concrete continues to hydrate. The fly ash increases the sulfuric acid resistance of concrete. Fly ash additions have only a limited effect on reducing the risk of probability of corrosion of steel in the concrete. The load capacities of 10% and 20% fly ash reinforced concrete beams are higher than that of the control beams after 300 days immersed in a 5% NaCl solution.

Experimental Study on Sustainable Concrete with the Mixture of Low Calcium Fly Ash and Lime as a Partial Replacement of Cement

2011 ◽  
Vol 250-253 ◽  
pp. 307-312 ◽  
Author(s):  
Muthuramalingam Jayakumar ◽  
M. Salman Abdullahi
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Water Absorption ◽  
Chloride Ion ◽  
Apparent Volume ◽  
Partial Replacement ◽  
Fly Ash Concrete ◽  
Low Calcium ◽  
Chloride Ion Penetration ◽  
Ion Penetration

Even though the use of fly ash in concrete is nowadays a common practice, its relatively slow pozzolanic reactivity hinders its greater utilization; hence efficient methods of activation are on demand. This study was carried out to evaluate the influence of lime as a chemical activator on the mechanical and durability properties of high strength fly ash concrete. Mixtures were made with 0, 30, 40, and 50% of cement replaced by low calcium fly ash. Corresponding mixtures were also made with the same amount of fly ash and addition of 10% of lime to each mixture. For each concrete mixture, slump, compressive strength, water absorption, sorptivity, apparent volume of permeable voids, and resistance to chloride-ion penetration were measured. The results obtained showed that addition of lime improved the compressive strength significantly at all ages. The strength of all the fly ash mixtures containing lime surpassed that of the corresponding Portland cement mix at 60 days. Addition of lime also improved the sorptivity and resistance to chloride-ion penetration of the fly ash concrete. It however increases the water absorption and the volume of permeable voids of the fly ash concrete.

scholarly journals A Review on Early Age and Long-term Compressive Strength of High-volume Fly Ash Concrete

2018 ◽  
Vol 207 ◽  
pp. 01004
Author(s):  
Mu Li
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
High Volume ◽  
Partial Replacement ◽  
Early Age ◽  
Fly Ash Concrete ◽  
Power Stations ◽  
High Volume Fly Ash ◽  
Curing Age

Fly ash is a by-product of the combustion of the coal-fired electric power stations, and disposal of fly ash has been one of the environmental challenges. Much of the studies have been focused on the mechanical property of fly ash concrete. It is no doubt that the use of high-volume fly ash as a partial replacement of cement is also one of the effect way to utilize fly ash. It is known that the compressive strength of fly ash concrete is lower than that of ordinary concrete at early age, especially for high-volume fly ash concrete. It is urgent for engineers to consider the compressive strength of high-volume fly ash concrete at different curing age. In this review, the compressive strength of high-volume fly ash concrete in various literature was reported and then analyzed. Furthermore, the proposal of the utilization of high-volume fly ash concrete is provided.

Effects of Elevated Temperatures on the Compressive Strength of HFCC

2011 ◽  
Vol 261-263 ◽  
pp. 416-420 ◽  
Author(s):  
Fu Ping Jia ◽  
Heng Lin Lv ◽  
Yi Bing Sun ◽  
Bu Yu Cao ◽  
Shi Ning Ding
Keyword(s):  
Compressive Strength ◽  
Elevated Temperature ◽  
Fly Ash ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Relative Strength ◽  
Ordinary Concrete ◽  
Residual Compressive Strength ◽  
Fly Ash Concrete ◽  
The Relationship

This paper presents the results of elevated temperatures on the compressive of high fly ash content concrete (HFCC). The specimens were prepared with three different replacements of cement by fly ash 30%, 40% and 50% by mass and the residual compressive strength was tested after exposure to elevated temperature 250, 450, 550 and 650°C and room temperature respectively. The results showed that the compressive strength apparently decreased with the elevated temperature increased. The presence of fly ash was effective for improvement of the relative strength, which was the ratio of residual compressive strength after exposure to elevated temperature and ordinary concrete. The relative compressive strength of fly ash concrete was higher than those of ordinary concrete. Based on the experiments results, the alternating simulation formula to determine the relationship among relative strength, elevated temperature and fly ash replacement is developed by using regression of results, which provides the theoretical basis for the evaluation and repair of HFCC after elevated temperature.

The Effect of Substituting Rdf on the Physical and Environmental Properties of Coal Fly Ash

1988 ◽  
Vol 136 ◽  
Author(s):  
Ashaari B. Mohamad ◽  
David L. Gress
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Physical Properties ◽  
Activity Index ◽  
Coal Fly Ash ◽  
Pozzolanic Activity ◽  
Portland Cement Concrete ◽  
Fly Ash Concrete ◽  
Refuse Derived Fuel ◽  
Cadmium And Lead

ABSTRACTRefuse-derived-fuel (RDF) consisting mainly of waste paper and plastics is a viable fuel source for the production of power. An experimental test burn partially substituting coal with RDF was undertaken by the Public Service of New Hampshire at the Merrimack Power Station.Five percent and ten percent RDF were substituted, on a BTU basis, for coal in the test bums. The chemical and physical properties of the resulting fly ash were determined. Twelve test burn days were run with 4 days of 5% RDF and 8 days of 10% RDF. Emphasis was placed on investigating the effect of the RDF fly ash on Portland cement concrete.Most of the chemical and physical properties of the coal-RDF fly ash were found to be comparable with ordinary coal fly ash except for the amount of cadmium and lead, the pozzolanic activity index and the compressive strength of fly ash concrete. Cadmium and lead were at average levels of 5.1 ppm and 102.6 ppm for the 5% RDF, and 7.8 ppm and 198.3 ppm for the 10% RDF, respectively. Although the pozzolanic activity index of coal-RDF fly ash increases over normal coal fly ash, preliminary results show that the 28-day compressive strength of concrete with direct replacement of cement and sand decreases by up to 30%. Leaching tests on crushed concrete were conducted to evaluate the environmental effect of acid rain.

scholarly journals Effect of Fly Ash on the Compressive Strength of Green Concrete

2020 ◽  
Vol 10 (3) ◽  
pp. 5728-5731 ◽  
Author(s):  
S. A. Chandio ◽  
B. A. Memon ◽  
M. Oad ◽  
F. A. Chandio ◽  
M. U. Memon
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Recycled Aggregates ◽  
Waste Materials ◽  
Partial Replacement ◽  
Equal Proportion ◽  
Standard Size ◽  
Green Concrete ◽  
Coarse Aggregates ◽  
Management Issues

This research paper aims at investigating the effects of fly ash as cement replacement in green concrete made with partial replacement of conventional coarse aggregates with coarse aggregates from demolishing waste. Green concrete developed with waste materials is an active area of research as it helps in reducing the waste management issues and protecting the environment. Six concrete mixes were prepared using 1:2:4 ratio and demolishing waste was used in equal proportion with conventional aggregates, whereas fly ash was used from 0%-10% with an increment of 2.5%. The water-cement ratio used was equal to 0.5. Out of these mixes, one mix was prepared with all conventional aggregates and was used as the control, and one mix with 0% fly ash had only conventional and recycled aggregates. The slump test of all mixes was determined. A total of 18 cylinders of standard size were prepared and cured for 28 days. After curing the compressive strength of the specimens was evaluated under gradually increasing load until failure. It is observed that 5% replacement of cement with fly ash and 50% recycled aggregates gives better results. With this level of dosage of two waste materials, the reduction in compressive strength is about 11%.

scholarly journals Influence of Partial Replacement of Micro-Silica by Fly-Ash on Strength Properties of Reactive Powder Concrete

2020 ◽  
Vol 9 (3) ◽  
pp. 2932-2937
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Fly Ash ◽  
Mechanical Performance ◽  
Cementitious Materials ◽  
Partial Replacement ◽  
Reactive Powder Concrete ◽  
Experimental Investigations ◽  
Reactive Powder ◽  
Micro Silica

Reactive powder concrete (RPC) is the ultra-high strength concrete made by cementitious materials like silica fumes, cement etc. The coarse aggregates are completely replaced by quartz sand. Steel fibers which are optional are added to enhance the ductility. Market survey has shown that micro-silica is not so easily available and relatively costly. Therefore an attempt is made to experimentally investigate the reduction of micro-silica content by replacing it with fly-ash and mechanical properties of modified RPC are investigated. Experimental investigations show that compressive strength decreases gradually with addition of the fly ash. With 10 per cent replacement of micro silica, the flexural and tensile strength showed 40 and 46 per cent increase in the respective strength, though the decrease in the compressive strength was observed to be about 20 per cent. For further percentage of replacement, there was substantial drop in compressive, flexural as well as tensile strength. The experimental results thereby indicates that utilisation of fly-ash as a partial replacement to micro silica up to 10 per cent in RPC is feasible and shows quite acceptable mechanical performance with the advantage of utilisation of fly-ash in replacement of micro-silica.

High Volume Slag and Slag-Fly Ash Blended Cement Pastes Containing Nano Silica

2019 ◽  
Vol 967 ◽  
pp. 205-213
Author(s):  
Faiz U.A. Shaikh ◽  
Anwar Hosan
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Cement Paste ◽  
Ordinary Portland Cement ◽  
Blended Cement ◽  
High Volume ◽  
Ash Content ◽  
Partial Replacement ◽  
Nano Silica ◽  
Cement Pastes

This paper presents the effect of nanosilica (NS) on compressive strength and microstructure of cement paste containing high volume slag and high volume slag-fly ash blend as partial replacement of ordinary Portland cement (OPC). Results show that high volume slag (HVS) cement paste containing 60% slag exhibited about 4% higher compressive strength than control cement paste, while the HVS cement paste containing 70% slag maintained the similar compressive strength to control cement paste. However, about 9% and 37% reduction in compressive strength in HVS cement pastes is observed due to use of 80% and 90% slag, respectively. The high volume slag-fly ash (HVSFA) cement pastes containing total slag and fly ash content of 60% exhibited about 5%-16% higher compressive strength than control cement paste. However, significant reduction in compressive strength is observed in higher slag-fly ash blends with increasing in fly ash contents. Results also show that the addition of 1-4% NS improves the compressive strength of HVS cement paste containing 70% slag by about 9-24%. However, at higher slag contents of 80% and 90% this improvement is even higher e.g. 11-29% and 17-41%, respectively. The NS addition also improves the compressive strength by about 1-59% and 5-21% in high volume slag-fly ash cement pastes containing 21% fly ash+49%slag and 24% fly ash+56%slag, respectively. The thermogravimetric analysis (TGA) results confirm the reduction of calcium hydroxide (CH) in HVS/HVSFA pastes containing NS indicating the formation of additional calcium silicate hydrate (CSH) gels in the system. By combining slag, fly ash and NS in high volumes e.g. 70-80%, the carbon footprint of cement paste is reduced by 66-76% while maintains the similar compressive strength of control cement paste. Keywords: high volume slag, nanosilica, compressive strength, TGA, high volume slag-fly ash blend, CO2 emission.

Macroscopic and Microscopic Properties of High Performance Concrete with Partial Replacement of Cement by Fly Ash

2019 ◽  
Vol 292 ◽  
pp. 108-113 ◽  
Author(s):  
Josef Fládr ◽  
Petr Bílý ◽  
Roman Chylík ◽  
Zdeněk Prošek
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Fly Ash ◽  
High Performance ◽  
High Performance Concrete ◽  
Partial Replacement ◽  
Experimental Program ◽  
Second Phase ◽  
Depth Of Penetration ◽  
Cement Replacement

The paper describes an experimental program focused on the research of high performance concrete with partial replacement of cement by fly ash. Four mixtures were investigated: reference mixture and mixtures with 10 %, 20 % and 30 % cement weight replaced by fly ash. In the first stage, the effect of cement replacement was observed. The second phase aimed at the influence of homogenization process for the selected 30% replacement on concrete properties. The analysis of macroscopic properties followed compressive strength, elastic modulus and depth of penetration of water under pressure. Microscopic analysis concentrated on the study of elastic modulus, porosity and mineralogical composition of cement matrix using scanning electron microscopy, spectral analysis and nanoindentation. The macroscopic results showed that the replacement of cement by fly ash notably improved compressive strength of concrete and significantly decreased the depth of penetration of water under pressure, while the improvement rate increased with increasing cement replacement (strength improved by 18 %, depth of penetration by 95 % at 30% replacement). Static elastic modulus was practically unaffected. Microscopic investigation showed impact of fly ash on both structure and phase mechanical performance of the material.

scholarly journals Modification of Ordinary Concrete Using Fly Ash from Combustion of Municipal Sewage Sludge

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 487 ◽  
Author(s):  
Gabriela Rutkowska ◽  
Piotr Wichowski ◽  
Małgorzata Franus ◽  
Michał Mendryk ◽  
Joanna Fronczyk
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Sewage Sludge ◽  
Penetration Depth ◽  
Environmental Benefits ◽  
Municipal Sewage ◽  
Partial Replacement ◽  
Municipal Sewage Sludge ◽  
Water Penetration ◽  
The Impact

This article focuses on the impact of fly ash from the combustion of municipal sewage sludge (FAMSS) as a cement additive in the amounts of 5%, 10%, 15%, 20% and 25% (by mass) on selected concrete properties. In the course of the experimental work, water penetration depth and compressive strength measurements were made at various periods of curing (from 2 to 365 days). In addition, the potential impact of FAMSS on the natural environment was examined by determining the leachability of heavy metals. FAMSS-modified concretes showed small values of water penetration depth (lower than 50 mm), as well as good compressive strength (reaching minimum class C30/37 after 130 days of maturing)—similar to the compressive strength obtained for conventional concrete. In addition, the partial replacement of cement with FAMSS has environmental benefits, expressed as a reduction in CO2 emissions. In addition, study has shown that compliance with environmental requirements is associated with heavy metal leaching.

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