Percent Of Fly Ash Research Articles

Alkali-Activated Mortars with Recycled Fines and Hemp as a Sand.

Nowadays, effective and eco-friendly ways of using waste materials that could replace natural resources (for example, sand) in the production of concrete composites are highly sought. The article presents the results of research on geopolymer composites produced from two types of waste materials—hemp and fine fractions recovered from recycled cement concrete, which were both used as a replacement for standard sand. A total of two research experiments were conducted. In the first experiment, geopolymer mortars were made using the standard sand, which was substituted with recycled fines, from 0% to 30% by weight. In the second study, geopolymers containing organic filler were designed, where the variables were (i) the amount of hemp and the percent of sand by volume (0%, 2.5%, and 5%) and(ii) the amount of hydrated lime and the percent of fly ash (by weight) (0%, 2%, and 4%) that were prepared. In both cases, the basic properties of the prepared composites were determined, including their flexural strength, compressive strength, volume density in a dry and saturated state, and water absorption by weight. Observations of the microstructure of the geopolymers using an electron and optical microscope were also conducted. The test results show that both materials (hemp and recycled fines) and the appropriate selection of the proportions of mortar components and can produce composites with better physical and mechanical properties compared to mortars made of only natural sand. The detailed results show that recycled fines (RF) can be a valuable substitute for natural sand. The presence of 30% recycled fines (by weight) as a replacement for natural sand in the alkali-activated mortar increased its compressive strength by 26% and its flexural strength by 9% compared to control composites (compared to composites made entirely of sand without its alternatives). The good dispersion of both materials in the geopolymer matrix probably contributed to filling of the pores and reducing the water absorption of the composites. The use of hemp as a sand substitute generally caused a decrease in the strength properties of geopolymer mortar, but satisfactory results were achieved with the substitution of 2.5% hemp (by volume) as a replacement for standard sand (40 MPa for compressive strength, and 6.3MPa for flexural strength). Both of these waste materials could be used as a substitute for natural sand and are examples of an eco-friendly and sustainable substitution to save natural, non-renewable resources.

Flyash and carbon fibers reinforced aluminum-based matrix composite for structural applications

Aluminum alloy and its composite showed excellent physical and mechanical properties. But still, there is a scope in improving the mechanical properties of the composite for the structural, automobile, and aerospace industry. The composites have been prepared to reach the needs of the industry. In this present work, micro-fillers such as fly ash, and carbon fiber reinforcements were added to the base AA7076 matrix and fabricated the composite using a motorized stir casting technique. AA7076/fly ash and AA7076/carbon fiber composites were prepared by varying wt.% percent of fly ash and carbon fiber reinforcements (0.5, 0.75, 1, and 1.25 wt.%) and results were compared. The SEM micrographs revealed the homogeneous distribution of fly ash and carbon fiber reinforcements along the grain boundaries of the AA7076 matrix material. The composites with 1 wt.% of micro-fillers showed superior hardness and tensile strength as compared to other reinforcement composite and base matrix. The experimental test results revealed that the addition of fly ash and carbon fiber reinforcements improved the mechanical properties of the AA7076/fly ash and AA7076/carbon fiber composites as compared to the AA7076 matrix material. Among them, the comparative study revealed that the AA7076/carbon fiber composite has showed homogeneous distribution of reinforcements and improved mechanical properties.

Effect of Grinding Methods on the Performance of Ground Fly Ash

In this study, coarse fly ash was ground with laboratory ball mill, vibration mill and jet mill respectively. The powder characteristic of ground fly ash was tested by laser particle size analyzer and scanning electron microscope. And the performance of cement containing different ground fly ash was also studied. It was observed that the characteristic value of fly ash ground by ball mill, vibration mill and jet mill was 13.543 μm, 13.403 μm and 17.344 μm, respectively, when average particle size was about 25μm. And the uniformity coefficient of fly ash ground by ball mill, vibration mill, and jet mill was 1.26, 1.24 and 1.38, respectively. Specially, the mortar strength was increased when 10 to 20 percent of ground fly ash was added. And the highest fluidity of mortar was obtained when 30 percent of fly ash ground by jet mill was added.

Preparation and Properties of Sintered Copper–Tin Composites Containing Copper Coated or Uncoated Fly Ash

Copper–5%tin–fly ash mixtures containing 0–16 wt% fly ash with or without copper coating were prepared. Small cylindrical specimens of 9 mm diameter and 10.5 mm length were fabricated at 300 MPa using single action die compaction at ambient temperature. These compacts were sintered in argon atmosphere for a period of 45 min at 700°, 740°, and 780°C, respectively. The green and sintered properties of the compacts were determined as a function of fly ash weight percent. The results indicated that density, hardness, and compression strength of the green compacts were improved by the electroless copper coating on fly ash reinforcement. It was also observed that coated green compacts exhibited lower spring back and higher ejection pressures compared to uncoated compacts. Sintering resulted in increase in density and decrease in volume of green compacts. Sintered density of the composites was found to decrease with increasing weight percent of fly ash. It was further observed that sintering of coated composites resulted in higher densification, hardness and, compressive yield strength than uncoated composites. Dry sliding wear behavior of the sintered coated and uncoated fly ash composites was also carried out at room temperature using a pin-on-disc machine. Copper coated fly ash compacts exhibited better wear resistance than the matrix and uncoated fly ash compacts within the range investigated.

The Line Method for Petrographic Determination of the Quantity of Fly Ash and Ground-granulated Blast Furnace Slag in Hardened Concrete and Blended Cement

Abstract Research was undertaken using thin sections and immersion mounts with the objective of using a modified line count procedure for the quantitative petrographic determination of fly ash and ground-granulated blast furnace slag (GGBFS) in hardened concrete and blended cements. The line method used in this study is a variation of standard microscopic point count methods and yields an average number frequency that is a linear function of the weight percent of fly ash or GGBFS of total cementitious materials. Multiple traverses were counted on thin sections of concrete over areas of paste only and in immersion slides of blended cements containing known amounts of fly ash and GGBFS. The average number of particles in a traverse was computed, the traverse length being equal to the width of the field of view of the petrographic microscope. For hardened concrete, only pozzolan particles were counted. For blended cements, all particles were counted and the ratio of pozzolan particles to total particles was determined. A linear relationship between the average number of pozzolan particles for a traverse line and the weight percent of pozzolan makes it possible to estimate the fly ash and GGBFS content of unknowns. Results of the research indicate that the line method is a rapid and accurate method for petrographic determination of fly ash and GGBFS in hardened concrete and blended cements. This technique and variations of it have been used by other researchers and it has the potential to be a standard test procedure.

Adsorption-desorption studies of selected herbicides in soil-Fly ash mixtures.

Fly ash and soil mixtures with a range of fly ash content from 0 to 100% were used to study the adsorption and desorption of herbicides atrazine, propazine, prometryne, propanil, and molinate in batch experiments. The isotherms shapes according to Giles classification (Giles et al., 1960) were S, L, and H as the substrate changed from sandy clay loam (SCL) to fly ash, depending on the percent of fly ash in the mixture. The adsorption isotherms fit the Freundlich equation x/m = K(f) C(1/)(n)(). The K(f) values increase with the increase of the fly ash content. The mean percent amounts of herbicides, for a range of concentration 1-20 mg L(-)(1), adsorbed on the soil were 21.9% for atrazine, 50.7% for propazine, 29.04% for prometryne, 43.14% for molinate, 31.35% for propachlor, and 46.34% for propanil. Mass balance estimations show that the adsorbed amounts of the herbicides increase along with the fly ash content in the sorbent mixture and reach the 99% in the "pure" fly ash. In contrast, the amounts desorbed with water decrease as the fly ash content increases. The n values ranged from 0.82 to 3.05 indicating that the carbon content of fly ash plays a significant role during the sorption process and an increase of heterogenity of solid substrate. The increase of the amounts desorbed with acetone indicates that the sorption of organic compounds onto fly ash is believed to occur principally via the weak induction forces of London or dispersion forces which are characteristic of the physical adsorption process. The results of this research demonstrate that the fly ash shows a significant capacity for adsorption of organic compounds from aqueous solution.

Empirical Correlations from Waste Grout Formulation Data

Data correlations have demonstrated systematic relationships between important variables in hydrofracture grout formulation. The data are taken from an investigation to determine conditions for eliminating drainable water from the grout system. The two most important variables affecting drainable water are the amounts of Attapulgite-150 clay in the dry-solids blends and the ratios in which the blends are mixed with the waste. Empirical equations were developed relating (a) volume percent of drainable water, (b) time for free water adsorption, (c) weight percent of clay, (d) dry-blend liquid-waste mix ratio, (e) compressive strength, (f) weight percent of fly ash, and (g) pumping flow rate required for turbulent flow through 51-mm-i.d. pipe. The equations allow predictions of properties within the compositional range of the investigation from which the data were obtained. They also provide a relatively simple method that can be used to improve future test design, eliminate superfluous testing, decrease costs, and increase overall efficiency of individual investigations.