Papers by Keyword: Pulverized Fuel Ash

Abstract: Concrete is used as a construction material because of its superior mechanical and durability performance and comparably inexpensive cost when compared to other building materials. However, because of its innate heterogeneity, low tensile strength, and unfavourable service environment, concrete is vulnerable to progression and coalescence in micro-cracks production. This study looked into the self-healing assessment of pre-cracked PFA concrete. PFA cement was utilized to replace 10, 20, and 30% of the weight of cement used. To investigate the strength development of PFA concrete, compressive strength was determined. An ultrasonic pulse velocity (UPV) test was performed to monitor the self-healing progress of the concrete to assess the impact of PFA on autogenous healing concrete. The tests were conducted at 7, 28, 60, and 90 days after being cured in water. The result shows that concrete integrated with 10% of PFA as a cement replacement recorded the highest compressive strength compared to those mixes. It is also revealed that UPV readings increased significantly with the increased curing ages for concrete mixes. The results also revealed that the autogenous healing ability of pre-cracked and PFA concrete progressively improved. Based on RSM analysis, the inclusion of PFA in concrete has a strong relationship with strength and autogenous healing progression. Considering all these test results, it was attained that 10% of PFA in concrete exhibits excellent compressive strength and autogenous healing concrete.

Abstract: Waste materials such as Pulverized Fuel Ash (PFA) is a possible alternative to reduce disposal activities and this study is to investigate suitability of PFA by conducting three laboratory tests namely unconfined compression test (UCT), shear box test (SBT) and plate load test. Both UCT and SBT to determine the optimum configuration of PFA that able to achieve the highest percentage of strength of PFA-cement-sand column, meanwhile plate load test is to study the effectiveness of using PFA-cement-sand column in the aspect of the bearing capacity for soft soil. In this study, it was investigated that by using the right configuration of PFA, cement and sand, it can produce a good product of sand column for the purpose of road construction. The highest shear strength was recorded is 93.51 kPa and the proportion of materials is 12%: 60: 28% (ratio of cement: PFA: sand).

Abstract: Magnesium silicate hydrate (M-S-H) gel can be fabricated via the reaction of MgO with silica fume in the presence of sodium hexametaphosphate (Na-HMP). In this study, in effort to reduce the cost of the M-S-H gel system, pulverized fuel ash (PFA) was utilized as a silica source to replace silica fume. The influence of various PFA quantities on the compression strength and other properties of the M-S-H system were investigated via XRD, SEM, and TG-RTG analysis. Compressive strength was optimal when 35 wt% of silica fume was replaced. The hydration products were relatively more complex when PFA was used, containing hydrated calcium silicate, hydrated magnesium silicate, and carbonate gel, among other products. Magnesium carbonate participated in the hydration reaction process, which generated carbonated gel to form a grid structure and promoted the initial strength of the material. Taken together, the results showed that PFA can be feasibly and effectively used to form M-S-H gel cement systems at low cost.

Abstract: This study reports the findings of an experimental investigation for bamboo fibre (BF) reinforced concrete board. In this research, all specimens were prepared at 0.4 water/binder ratio. There were two series of specimens namely A series and B series. The A group utilizes only ordinary portland cement (OPC) as binder. Meanwhile, series B specimens uses binary binders, which were combination of OPC and pulverized fuel ash (PFA) with PFA to OPC ratio of 0.2. The performance of flat board plates with different percentage of bamboo fiber ranging from 0% to 5% and 20% PFA incorporation of cement weight were tested for bending strength (flexural) and compressive strength in accordance to BS 5669: Part 1 for particleboards. Specimens are cured in water curing tank and tested at 3, 7 and 28 days for compression test. Meanwhile for flexural strength test, the specimens are tested at 28 days. It is found that flexural and compressive strength increases with addition of BF. The optimum compressive and flexural strength at 28 days are recorded with 3% incorporation of BF for both PFA and control samples. Therefore, utilizing natural fibre and waste material for partial substitution of cement content in producing internal wall paneling system could contributes to the economic appeal and promoting sustainable construction approach.

Abstract: Pulverized fuel ash (PFA) can be classified as hazardous Coal Combustion by-Product (CCP), which can contributes to the environmental pollution. According to (ACAA 2009), USA itself has produced approximately 125.5 million tons per annual of CCP which merely 56 million tons of these waste by-products has been successfully employed in applications and others still remain untreated. Disposal of these materials in landfills can deduce ecological. Thus, finding the solutions and methods of recycling these waste materials are needed, as it can be used as one of the materials in construction projects, engineering purpose or stabilizing process. Therefore, a study on direct shear test have been conducted and the data collected from this study were compared and analyzed through various methods to find out how does PFA works on improving geotechnical properties.

Abstract: This paper will conduct a systematic study on method of recovering Ge from pulverized fuel ash in Lincang prefecture, Yunnan province. Details are like this, in view of the fact that Ge contained in pulverized fuel ash is wrapped up by a lot of Silica, Cao, magnesium oxide and is difficult to react with hydrochloric acid, so, first, have the pulverized fuel ash grinded to 200 meshes; then, ammonium fluoride should be put into 85-90°Cdilute sulphuric acid solution to produce hydrogen fluoride so as to destroy silicon dioxide and calcium oxide contained in the pulverized fuel ash. Meanwhile, dilute sulphuric acid solution dissolves magnesium oxide, by doing so, Ge will be released to react with sulfuric acid and produce Sulfuric acid Ge, and Ge will go into the solution；as for low state Ge（e.g,GeO,GeS）contained in the pulverized fuel ash which is difficult to be dissolved by sulfuric acid, sodium chlorate will be used as a kind of oxidant to change bivalence Ge into tetravalence Ge, then dissolve it into the solution, after the liquid-solid separation, sulfuric acid leaching solution rich in Ge will be obtained. Then, tannic acid will be used as precipitant to recover Ge from the leaching solution, and Ge concentrate will be produced through distillation and roasting. After this, put Ge concentrate on hydrochloric acid distillation to get germanium tetrachloride, After going through strenuous evaporation, distillation and hydrolysis, germanium dioxide with high purity will be yield. This paper has conducted conditional tests and discussion on the process parameters which will influence recovery Ge from pulverized fuel ash, including the dosage of Sulfuric acid, ammonium fluoride, sodium chlorate ,tannic acid and extraction time to find out the prior controlling condition of Ge recovery，under this prior condition, Ge leaching rate is as high as 84%，and tannic sinking Ge rate is as high as 98%. The pulverized fuel ash, after recovering Ge, can be used to backfill the mine pit, besides, most of the lixivium after recovering Ge can be recycled, and the rest of it will be released after neutralized up to the standard by lime. This process enjoys the following quality: high Ge recovery rate, less time used during the process ,less consumption of auxiliary material, easier to control the process, avoiding the potential pollution on the environment and lower cost involved in it, therefore, which is a kind of efficient and economic process of recovering Ge from pulverized fuel ash.

Abstract: Owing to the less exothermic pozzolanic reaction of pulverized fuel ash (PFA) compared to cement hydration, the addition of PFA can reduce the heat generation of concrete during its hardening. However, as the water to binder (W/B) ratio would affect the proportions of cement and PFA that could react with water, the conventional practice of determining concrete temperature rise solely based on the cement and PFA contents may not yield accurate estimations. An experimental programme was launched to investigate the adiabatic temperature rise of PFA concrete mixes. Seven concrete mixes without PFA added and 14 concrete mixes with PFA dosages at 20% and 40% were tested with the recently developed semi-adiabatic curing test method. The adiabatic temperature rise was obtained by applying heat loss compensation to the test results. It was found that the incorporation of PFA could suppress the adiabatic temperature rise by 4°C to 14°C. The test results revealed the dependence of adiabatic temperature rise on both PFA dosage and W/B ratio, whose combined effects can be accurately addressed via the prediction formula and design chart developed herein.