Effect of fly ash addition on the mechanical properties of tile adhesive

Statistical relationship between various strengths of tile adhesives in which cement or sand was partially replaced with fly ash was studied. A low-lime fly ash was used in five different replacement levels from 5% to 30% by weight of either cement or sand. The tensile adhesion, flexural and compressive strengths of adhesives were determined at 2, 7 and 28 days. In small substitution levels, sand replacement increased the tensile adhesion strength. No strong relationship was found between tensile adhesion strength and flexural or compressive strength of the specimens in which the fly ash was used as sand replacement (r < 0.659). Strong relationship was observed between the same properties when fly ash was used as cement replacement (r > 0.896). Flexural and compressive strength values showed quite strong relationship (r > 0.949). This may be due to the fact that both of these strength values were obtained on the same specimens.     

Lime based steam autoclaved fly ash bricks

About 10 million tonnes of fly ash are produced yearly as waste from coal fired thermal power plants in Turkey. Only a small portion of this waste is utilized as a raw material in the production of cement and concrete. In this study, Seyitömer power plant fly ash was investigated in the production of light weight bricks. Fly ash, sand and hydrated lime mixtures were steam autoclaved under different test conditions to produce brick samples. An optimum raw material composition was found to be a mixture of 68% fly ash, 20% sand and 12% hydrated lime. The optimum brick forming pressure was 20 MPa. The optimum autoclaving time and autoclaving pressure were found 6 h and 1.5 MPa, respectively. The compressive strength, unit volume weight, water absorption and thermal conductivity of the fly ash–sand–lime bricks obtained under optimum test conditions are 10.25 MPa, 1.14 g/cm³, 40.5% and 0.34 W  m⁻¹ K⁻¹ respectively. The results of this study suggested that it was possible to produce good quality light weight bricks from the fly ash of Seyitömer power plant.     

Influence of class F fly ash on the abrasion–erosion resistance of high-strength concrete

This study investigates the abrasion–erosion resistance of high-strength concrete (HSC) mixtures in which cement was partially replaced by four kinds of replacements (15%, 20%, 25% and 30%) of class F fly ash. The mixtures containing ordinary Portland cement were designed to have 28 days compressive strength of approximately 40–80 MPa. Specimens were subjected to abrasion–erosion testing in accordance with ASTM C1138. Experimental results show that the abrasion–erosion resistances of fly ash concrete mixtures were improved by increasing compressive strength and decreasing the ratio of water-to-cementitious materials. The abrasion–erosion resistance of concrete with cement replacement up to 15% was comparable to that of control concrete without fly ash. Beyond 15% cement replacement, fly ash concrete showed lower resistance to abrasion–erosion compared to non-fly ash concrete. Equations were established based on effective compressive strengths and effective water-to-cementitious materials ratios, which were modified by cement replacement and developed to predict the 28- and 91-day abrasion–erosion resistance of concretes with compressive strengths ranging from approximately 30–100 MPa. The calculation results are compared favorably with the experimental results.     

Comparison on efficiency factors of F and C types of fly ashes

Fly ashes are obtained from thermal power plants and they are pozzolanic materials, which can act as partial replacement material for both portland cement and fine aggregate. With their economical advantages and potential for improving fresh and hardened concrete performance, they have some benefits for using in concrete industry. In this study, the objective was to find the efficiency factors of Turkish C and F-type fly ashes and to compare their properties. Three different cement dosages were used (260, 320, 400 kg/m³), two different ratios (10% and 17%) of cement reduced from the control concretes and three different ratios (depending on cement reduction ratio) of fly ash were added into the mixtures. At the ages of 28 and 90 days, compressive strength, modulus of elasticity and ultrasound velocity tests were carried out. From the compressive strength results, the k efficiency factors of C and F-type fly ashes were obtained. As a result, it is seen that efficiency factors of the concrete produced by the replacement of F and C type fly ashes with cement increase with the increase in cement dosage and concrete age.     

Effect of W/C ratio on covering depth of fly ash concrete in marine environment

This investigation studied the effect of W/C ratio on covering depth required against the corrosion of embedded steel of fly ash concrete in marine environment up to 4-year exposure. Fly ash was used to partially replace Portland cement type I at 0%, 15%, 25%, 35%, and 50% by weight of cementitious material. Water to cementitious material ratios (W/C) of fly ash concretes were varied at 0.45, 0.55, and 0.65. The 200-mm concrete cube specimens were cast and steel bars with 12-mm diameter and 50 mm in length were inserted in the concrete with the covering depth of 10, 20, 50, and 75 mm. The specimens were cured in water for 28 days, and then placed to the tidal zone of marine environment in the Gulf of Thailand. Subsequently, the concrete specimens were tested for the compressive strength, chloride penetration profile and corrosion of embedded steel bar after being exposed to tidal zone for 2, 3, and 4 years. The results showed that the concrete mixed with Portland cement type I exhibited higher rate of the chloride penetration than the fly ash concrete. The chloride penetration of fly ash concrete was comparatively low and decreased with the increasing of fly ash content. The increase of fly ash replacement and the decrease of W/C ratio could reduce the covering depth required for the initial corrosion of the steel bar. Interestingly, fly ash concretes with 35% and 50% cement replacement and having W/C ratio of 0.65 provided better corrosion resistance at 4-year exposure than the control concrete with W/C ratio of 0.45. In addition, the covering depth of concrete with compressive strength of 30 MPa (W/C ratio of 0.65) could be reduced from 50 to 30 mm by the addition of fly ash up to 50%.     

Hybrid fiber reinforced self-compacting concrete with a high-volume coarse fly ash

This paper presents a study on the fresh and mechanical properties of a fiber reinforced self-compacting concrete incorporating high-volume fly ash that does not meet the fineness requirements of ASTM C 618. A polycarboxylic-based superplasticizer was used in combination with a viscosity modifying admixture. In mixtures containing fly ash, 50% of cement by weight was replaced with fly ash. Two different types of steel fibers were used in combination, keeping the total fiber content constant at 60 kg/m³. Slump flow time and diameter, V-funnel, and air content were performed to assess the fresh properties of the concrete. Compressive strength, splitting tensile strength, and ultrasonic pulse velocity of the concrete were determined for the hardened properties. The results indicated that high-volume coarse fly ash can be used to produce fiber reinforced self-compacting concrete, even though there is some reduction in the concrete strength because of the use of high-volume coarse fly ash.     

Preparation and characterisation of fly ash based geopolymer mortars

Geopolymer mortars with varying levels of sand aggregate were prepared and their physical and mechanical properties studied. The geopolymer binder to sand aggregate weight ratio was varied from 9 to 1. Compressive strength and Young’s modulus of the fly ash based geopolymer paste were 60 MPa and 2.27 GPa and these values did not change significantly with addition of up to 50 wt.% sand aggregate. Geopolymer binder exhibited strong bonding to the sand aggregate. Increasing sand content without increasing the amount of alkaline activator resulted in a decreasing level of geopolymerisation within the binder system.     

Mechanical and durability properties of concretes containing paper-mill residuals and fly ash

The use of paper-mill residuals in concrete formulations was investigated as an alternative to landfill disposal. The mechanical and durability properties of concrete containing paper-mill residuals collected from a wastewater treatment-plant were evaluated. Class F fly ash was used as a replacement for Portland cement (PC) when incorporated into concrete mixtures containing paper-mill residuals and the resulting products were compared to normal concrete. Compressive, splitting tensile, flexural strength and drying shrinkage tests were carried out to evaluate the mechanical properties for up to 90 days. Rapid chloride-permeability tests and initial surface-absorption tests were carried out at 28 days to determine the durability properties. Concrete containing paper-mill residuals showed improvement in the durability test results when PC was replaced with class F fly ash.     

Effects of post-mercury-control fly ash on fresh and hardened concrete properties

Activated carbon injection is the most mature technology for mercury capture from coal burning power plants; however, this technology increases the carbon content and mercury concentration in the fly ash. This, in turn, may reduce the suitability of fly ash for use in concrete and call into question the safety of using fly ash derived from this process. The focus of this paper is to investigate the reuse potential of post-mercury-control fly ash in concrete by examining the influence of three fly ashes derived from the activated carbon injection on the air content, compressive strength, permeability, and resistance to freezing and thawing of concrete mixtures. Laboratory testing confirmed the influence of the carbon on the air content of the concrete. However there was no difficulty in entraining air in activated carbon injection fly ash concretes within the recommended dosage range of the air-entraining admixture. All air-entrained fly ash concretes exhibited excellent characteristics in compressive strength (?32.0 MPa, 4641 psi at 28 days), resistance to chloride-ion penetration (moderate to low at 28 days of age) and freeze–thaw (?90 average durability factor after 300 cycles). The possible leaching of toxic elements including mercury from one fly ash sample used in this study was also evaluated using the US Environmental Protection Agency’s Toxicity Characteristic Leaching Procedure. The test results indicated that the leaching of toxic elements was much lower than the contamination level.     

Utilization of bagasse ash as a pozzolanic material in concrete

The physical properties of concrete containing ground bagasse ash (BA) including compressive strength, water permeability, and heat evolution, were investigated. Bagasse ash from a sugar factory was ground using a ball mill until the particles retained on a No. 325 sieve were less than 5wt%. They were then used as a replacement for Type I Portland cement at 10, 20, and 30wt% of binder. The water to binder (W/B) ratio and binder content of the concrete were held constant at 0.50 and 350 kg/m³, respectively.The results showed that, at the age of 28 days, the concrete samples containing 10–30% ground bagasse ash by weight of binder had greater compressive strengths than the control concrete (concrete without ground bagasse ash), while the water permeability was lower than the control concrete. Concrete containing 20% ground bagasse ash had the highest compressive strength at 113% of the control concrete. The water permeability of concrete decreased as the fractional replacement of ground bagasse ash was increased. For the heat evolution, the maximum temperature rise of concrete containing ground bagasse ash was lower than the control concrete. It was also found that the maximum temperature rise of the concrete was reduced 13, 23, and 33% as compared with the control concrete when the cement was replaced by ground bagasse ash at 10, 20, and 30wt% of binder, respectively. The results indicate that ground bagasse ash can be used as a pozzolanic material in concrete with an acceptable strength, lower heat evolution, and reduced water permeability with respect to the control concrete.     

Properties of fly ash concrete modified with hydrated lime and silica fume

This paper presents the results of an experimental investigation on the properties of fly ash concrete incorporating either hydrated lime or silica fume to improve the early strength of concrete. Test results indicated that the addition of lime and silica fume improved the early age compressive strength of fly ash concrete. The inclusion of silica fume was also found to increase the 28 days strength significantly. The air permeability of concrete containing lime and silica fume either decreased or remained almost the same when compared to the concrete without these. The addition of lime and silica fume also improved the sorptivity of concrete.Through the use of differential scanning calorimetry and thermogravimetric analysis (DSC/TG), it was demonstrated that the addition of hydrated lime increased the Ca(OH)₂ content; whereas the addition of silica fume decreased the Ca(OH)₂ content in the cement paste. The mercury intrusion porosimetry (MIP) data confirmed the beneficial action of hydrated lime and silica fume, towards decreasing the total pore volume of fly ash cement paste.     

Assessment of the effects of rice husk ash particle size on strength,water permeability and workability of binary blended concrete

This study develops the compressive strength, water permeability and workability of concrete by partial replacement of cement with agro-waste rice husk ash. Two types of rice husk ash with average particle size of 5 micron (ultra fine particles) and 95 micron and with four different contents of 5%, 10%, 15% and 20% by weight were used. Replacement of cement up to maximum of 15% and 20% respectively by 95 and 5 μm rice husk ash, produces concrete with improved strength. However, the ultimate strength of concrete was gained at 10% of cement replacement by ultra fine rice husk ash particles. Also the percentage, velocity and coefficient of water absorption significantly decreased with 10% cement replacement by ultra fine rice husk ash. Moreover, the workability of fresh concrete was remarkably improved by increasing the content of rice husk ash especially in the case of coarser size. It is concluded that partial replacement of cement with rice husk ash improves the compressive strength and workability of concrete and decreases its water permeability. In addition, decreasing rice husk ash average particle size provides a positive effect on the compressive strength and water permeability of hardened concrete but indicates adverse effect on the workability of fresh concrete.     

Lightweight concretes of activated metakaolin-fly ash binders,with blast furnace slag aggregates

This work investigated geopolymeric lightweight concretes based on binders composed of metakaolin with 0% and 25% fly ash, activated with 15.2% of Na₂O using sodium silicate of modulus SiO₂/Na₂O = 1.2. Concretes of densities of 1200, 900 and 600 kg/m³ were obtained by aeration by adding aluminium powder, in some formulations lightweight aggregate of blast furnace slag was added at a ratio binder:aggregate 1:1; curing was carried out at 20 and 75 °C. The compressive and flexural strength development was monitored for up to 180 days. The strength diminished with the reduction of the density and high temperature curing accelerated strength development. The use of the slag had a positive effect on strength for 1200 kg/m³ concretes; reducing the amount of binder used. The thermal conductivity diminished from 1.65 to 0.47 W/mK for densities from 1800 to 600 kg/m³. The microstructures revealed dense cementitious matrices conformed of reaction products and unreacted metakaolin and fly ash. Energy dispersive spectroscopy and X-ray diffraction showed the formation of amorphous silicoaluminate reaction products.     

A study of the workability and compressive strength characteristics of corn cob ash blended cement concrete

The study investigated the workability and compressive strength characteristics of corn cob ash (CCA) blended cement concrete. Nine classes of CCA-blended cements were employed with the CCA content ranging from 0% to 25%. The 0% CCA replacement involved the use of normal ordinary Portland cement and it served as the control. The mix proportions of cement:sand:granite used were 1:1½:3, 1:2:4 and 1:3:6 with 0.5, 0.6 and 0.7 water-to-cement ratios, respectively. The concrete cubes were tested at the curing ages of 3, 7, 28, 60, 120, and 180 days. Slump and compacting factor tests were carried out to check the effect of CCA on the workability of concrete. The results showed that the concrete slump and compacting factor decreased as the CCA content increased indicating that concrete becomes less workable (stiff) as the CCA percentage increases. The compressive strength of CCA-blended cement concrete was lower than the control at early ages, but improves significantly, and outperforms the control at later ages (120 days and above). The optimum compressive strength of 57.10 N/mm², 40.30 N/mm² and 28.07 N/mm² for 1:11/2:3, 1:2:4 and 1:3:6 mix proportions, respectively at 180 days were obtained at 8% CCA replacement level. It was concluded that only up to 8% CCA substitution is adequate where the blended cement is to be used for structural concrete.     

Effects of fly ash properties on characteristics of cold-bonded fly ash lightweight aggregates

The study presented herein provides a new insight into the effects of physical and chemical properties of the fly ash on the characteristics of the cold-bonded fly ash lightweight aggregates. LWAs were manufactured through the cold-bonding pelletization of two fly ashes differing in their physical and chemical properties. Moreover, one type of the LWAs was surface treated by water glass. The produced fly ash aggregates were then examined by means of ESEM micrograph, EDX spectrum, and XRD pattern to resolve the microstructural and the mineralogical characteristics of the LWAs. The findings of the study revealed that the fly ash with higher specific surface and with lower CaO content yielded higher strength LWAs. Furthermore, the surface treatment with water glass provided a marked increase in the aggregate strength and a reduction in the water absorption. The LWCs made with such LWAs had a compressive strength of as high as 60 MPa.     

Effect of Granulated Blast Furnace Slag and fly ash addition on the strength properties of lightweight mortars containing waste PET aggregates

In this work, the effect of Granulated Blast Furnace Slag (GBFS) and fly ash (FA) addition on the strength properties of lightweight mortars containing waste Poly-ethylene Terephthalate (PET) bottle aggregates was investigated. Investigation was carried out on three groups of mortar specimens. One made with only Normal Portland cement (NPC) as binder, second made with NPC and GBFS together and, third made with NPC and FA together. The industrial wastes mentioned above were used as the replacement of cement on mass basis at the replacement ratio of 50%. The size of shredded PET granules used as aggregate for the preparation of mortar mixtures were between 0 and 4 mm. The waste lightweight PET aggregate (WPLA)–binder ratio (WPLA/b) was 0.60; the water–binder (w/b) ratios were determined as 0.45 and 0.50. The dry unit weight, compressive and flexural–tensile strengths, carbonation depths and drying shrinkage values were measured and presented. The results have shown that modifying GBFS had positive effects on the compressive strength and drying shrinkage values (after 90 days) of the WPLA mortars. However, FA substitution decreased compressive and flexural–tensile strengths and increased carbonation depths. Nevertheless a visible reduction occurred on the drying shrinkage values of FA modifying specimens more than cement specimens and GBFS modified specimens. The test results indicated that, GBFS has a potential of using as the replacement of cement on the WPLA mortars by taking into consideration the characteristics. But using FA as a binder at the replacement ratio of 50% did not improve the overall strength properties. Although it was thought that, using FA as binder at the replacement ratio of 50% for the aim of production WPLA concrete which has a specific strength, would provide advantages of economical and ecological aspects.     

Filler effect and pozzolanic reaction of ground palm oil fuel ash

This research examines the compressive strength of mortar and how the filler effect and pozzolanic reaction of ground palm oil fuel ash (POFA) contribute to this strength. POFA and river sand were ground to three different particle sizes and used to replace Type I Portland cement at 10–40% by weight of binder to cast the mortar. The compressive strengths of ground POFA and ground river sand mortars were determined at various ages between 7 and 90 days. The results showed that the compressive strength of mortar due to the filler effect of ground river sand was nearly constant during the 7–90 day period for a specified replacement rate of cement. However, the compressive strength of mortar due to the filler effect tended to increase slightly with increased cement replacement. The pozzolanic reaction of ground POFA increased with increasing particle fineness of ground POFA, replacement rate of cement, and age of the mortar. The compressive strength contribution from the pozzolanic reaction of ground POFA was much more pronounced than the contribution from the filler effect when the smallest sizes of both materials were considered.     

粉煤灰影响海水海洋骨料水泥基材料抗压强度试验研究

通过试验测定不同粉煤灰掺量下的海水水泥净浆、海水海砂砂浆以及海水海洋骨料混凝土的抗压强度,研究粉煤灰掺量对海水海洋骨料水泥基材料抗压强度的影响。试验结果表明,随着粉煤灰掺量的增加,海水水泥净浆和海水海砂砂浆的抗压强度逐渐降低,海水海洋骨料混凝土抗压强度表现为先增大后减小。粉煤灰掺量对海水海洋骨料水泥基材料抗压强度的影响规律与粉煤灰掺量对淡水河砂水泥基材料抗压强度的影响规律基本一致,但影响程度略小于淡水河砂水泥基材料。     

Strength and drying shrinkage properties of concrete containing furnace bottom ash as fine aggregate

The strength and drying shrinkage of concretes with the natural sand replaced with furnace bottom ash (FBA) at 0%, 30%, 50%, 70% and 100% by mass, were studied at fixed water–cement ratios (W/C) and fixed slump ranges.The results showed that, at fixed water–cement ratios, the compressive strength and the drying shrinkage decreased with the increase of the FBA sand content. However, at fixed workability, the compressive strength was comparable with that of the control concrete, while the drying shrinkage increased with the increase of the FBA sand content beyond 30% replacement level. Nevertheless, 30% of the natural sand can be beneficially replaced with the FBA sand to produce concrete in the compressive strength range from 40 to 60 N/mm² without detrimentally affecting drying shrinkage properties of the concrete.     

The effect of high temperature on compressive strength and splitting tensile strength of structural lightweight concrete containing fly ash

In this study, the effect of high temperature on compressive and splitting tensile strength of lightweight concrete containing fly ash was investigated experimentally and statistically. The mixes incorporating 0%, 10%, 20% and 30% fly ash were prepared. After being heated to temperatures of 200, 400 and 800 °C, respectively, the compressive and splitting tensile strength of lightweight concrete was tested. This article adopts Taguchi approach with an L₁₆ (4⁵) to reduce the numbers of experiment. Two control factors (percentage of fly ash and heating degree) for this study were used. The level of importance of these parameters on compressive and splitting tensile strength was determined by using analysis of variance (ANOVA) method.