Strength Of Fly Ash Research Articles

Effect of Crushing Process Parameters on Quality of Fly Ash Aggregates Produced After Crushing High Strength Fly ash Blocks: A Laboratory Investigation

Effect of Crushing Process Parameters on Quality of Fly Ash Aggregates Produced After Crushing High Strength Fly ash Blocks: A Laboratory Investigation

Density, load and fly ash effect on stabilization of high plasticity soil with lime

The reuse recycling materials or industrial waste materials with aims to reduce pollution and environmental pollution, strongly supports concept of green building. Fly Ash is result of combustion pulverized system coal at the PLTU Tenayan, is no longer included in the B3 waste category. The usage of Fly Ash usage as building material, mine restoration, roads in this decade, is to replace cement or lime. The fly ash composition is mixed with lime for sub-base, will applied on high plasticity soils. A fix-mixture of soil and lime 5%, mixed with fly ash up to 30% of the mixture. The samples test was made at Optimum Moisture Content, with density values around Maximum Dry Density i.e. under compacted (under MDD) and over compacted (above MDD). Consolidated testing was performed with and without curing. Changes of load are represented by load increment ratio (LIR). The selected LIR value is 1.0; 1,5; and 2.0. The results showed that the higher of density, the volume of void is lower. The soil compression index value is the same for all density values, if the soil structure has not destroyed. or fatigue yet. In samples with crushed/broken soil structures, the value of the compressibility index decreased sharply. Curing successfully decreased the void ratio and compressibility of the soil. The strength of fly ash will decrease when reacting with water, so if soil burdened, the void ratio decreases drastically. The formation of strong molecular bonds between Fly ash and lime takes time. So, the compressibility value of the sample by curing 28 days is better than without curing. The composition levels between fly ash and lime also affects the compressibility index of the mixture. The optimum combination occurs in samples with a fly ash content of 25%.

A non-fired ceramsite construction material with enhanced lightweight high strength properties

The combustion of low calorific value coal in circulating fluidized bed boilers produces a large amount of fly ash with low activity and utilization. In this paper, the lightweight high strength ceramsite was prepared by a non-fired method using low-activity circulating fluidized bed fly ash (CFBFA) as raw material. And the effects of reinforcing agent and foaming agent on the properties of ceramsite were studied. The dosages of cement, quicklime, desulfurization gypsum and hydrogen peroxide were 15.0 wt%, 6.0 wt%, 6.0 wt% and 2.0 wt%, respectively. The hydration reaction in the system can be maximized by steam curing at 70 ℃ for 12 h. The bulk density and cylinder compressive strength of the obtained ceramsite were 695.34 kg/m3 and 5.5 MPa, respectively, which belonged to 700 grade high strength fly ash ceramsite. The corresponding apparent density and apparent porosity of the products were 1091.88 kg/m3 and 51.86 %, respectively. The admixture of cement, quicklime and desulfurization gypsum can all promote the hydration reaction in the system to produce denser needle-like and flocculent CSH. In addition, the admixture of hydrogen peroxide only enhanced the porosity of ceramsite and had no effect on the phase. The experimental process was simple, green and energy saving. In particular, the total solid waste utilization was up to 79 %.

Flexural Behavior of Low Calcium Fly Ash Based Geopolymer Reinforced Concrete Beam

Pioneering studies have been conducted on alternative cementitious material in the manufacturing of conventional concrete to reduce carbon emission and improve the overall efficacy. However, there are limited studies on eco-friendly materials with low calcium fly ash. This study aims to examine the strength fly ash geopolymer concrete and reduce carbon emission. In this investigation, flexural test is done for conventional and geopolymer concrete (GPC) beam samples after the fulfillment of rest period and 24 h steam curing at 60 °C. The experimental results prove that the initial characteristics of both specimens are almost similar. When GPC specimens reached the service, yield, and failure stages, the load carrying capacity, deflection increased up to 21.5 and 8.75%, respectively and better load bearing capacity, moment resistance, and crack propagation were observed more than in conventional cement. Fresh property test results indicated the achievement of standard workability without the addition of any admixture. Our study show that low calcium based geopolymer can be used as an efficient material for the alternate of cement in cement-based industries with eco-friendly nature.

Prediction of the Compressive Strength of Fly Ash Geopolymer Concrete by an Optimised Neural Network Model.

This article presents a regression tool for predicting the compressive strength of fly ash (FA) geopolymer concrete based on a process of optimising the Matlab code of a feedforward layered neural network (FLNN). From the literature, 189 samples of different FA geopolymer concrete mix-designs were collected and analysed according to ten input variables (all relevant mix-design parameters) and the output variable (cylindrical compressive strength). The developed optimal FLNN model proved to be a powerful tool for predicting the compressive strength of FA geopolymer concrete with a small range of mean squared error (MSE = 10.4 and 15.0), a high correlation coefficient with the actual values (R = 96.0 and 97.5) and a relatively small root mean squared error (RMSE = 3.22 and 3.87 MPa) for the training and testing data, respectively. Based on the optimised model, a powerful design chart for determining the mix-design parameters of FA geopolymer concretes was generated. It is applicable for both one- and two-part geopolymer concretes, as it takes a wide range of mix-design parameters into account. The design chart (with its relatively small error) will ensure cost- and time-efficient geopolymer production in future applications.

Effect of superplasticizer on the strength of fly ash based geopolymer concrete

In this research, the effect of a polycarboxylate based superplasticizer on the strength of Geopolymer Concrete (GPC) was investigated. A fixed amount of superplasticizer (1.5 % of Fly Ash weight) was utilized along with alkali activators Sodium Hydroxide (NaOH) and Sodium Silicate (Na2SiO3). The Ultrasonic Pulse Velocity Test determined the strength development of concrete. The quality of the GPC improved when a higher concentration of alkali activator was applied based on the Concrete Quality Designation. In detecting the color development of GPC, samples were put through MATLAB and specimens became lighter as time passes due to dehydration (a process where water escapes from the sample). Stress strain diagrams were generated which generally indicate that GPC specimens are ductile. The researchers were able to assess the workability of the mix designs using a rating from 1 to 5, with 1 being the least workable and 5 being the most workable.

Effects of waste glass sand on the thermal behavior and strength of fly ash and GGBS based alkali activated mortar exposed to elevated temperature

This study investigated the thermal behavior of a series of alkali activated mortars (AAm) based on blends of fly ash (FA) and ground granulated blast furnace slag (GGBS) precursors with waste glass (WG) and natural sand (NS) as fine aggregate. Results revealed that with increasing GGBS content, the AAms deteriorate after exposure to elevated temperature owing to dehydration causing mass loss, and weakening binder- aggregate bonding, which in turn decreased residual compressive strength. The efficacy of WG on the thermal behavior and mechanical strength depends on the binder type as well as on the temperature to which the AAms were exposed. In FA rich AAms, increasing WG showed good resistance to elevated temperature (200 –800 °C). Increasing WG in GGBS rich AAms, only showed acceptable performance for AAms exposed to 600 °C and 800 °C as the melted WG formed strong bonds with the matrix. However, for samples with 100 wt% WG and 100 wt% GGBS, surface spalling occurred at 200 °C, 400 °C and 600 °C and explosive spalling at 800 °C mainly caused by the high stresses induced on the expansion of both WG and matrix during exposure to elevated temperature.

Influence of curing method on characteristics of environment-friendly angular shaped cold bonded fly ash aggregates

A large quantity of natural aggregate is being used for the construction of roads, buildings, and mega-structures that affect the environment. It is also noticed that the scarcity of good quality aggregate in some regions of the country leads to an increase in the cost of aggregates. Some efforts have been made to find out a substitute for natural coarse aggregates. Several processes for the production of fly ash aggregates have been developed in the past and some of these were commercialized. These processes are very costly and time-consuming resulting in the non-use of these aggregates on a large scale in civil engineering applications. It is also found that the pelletization process manufactures round-shaped aggregates that have negligible interlocking properties leading to lower load-bearing capacity. In this study, the effect of various curing methods on the strength of fly ash-lime mixes are investigated through the unconfined compressive strength, aggregate impact value, X-ray Diffraction pattern, and scanning electron microscope images. From this study, the hot water curing method has been found as more effective for the hardening of the fly ash aggregates and suggested for further study. Secondly, the rapid and economical four-step process for the production of angular shaped high strength fly ash aggregate has been proposed in the paper. This method for producing fly ash aggregate comprises simple four steps of mixing, compaction, curing, and crushing. The aggregates made with the said process have dense structure, angular in shape for better interlocking, excellent mechanical properties such as toughness and hardness, and high durability. These aggregates also fulfill the Indian specifications for road aggregate and the requirement of structural concrete aggregates. The bulk utilization of this fly ash aggregates in the civil infrastructures can solve two problems with one effort: (a) Fly ash disposal problem and (b) Provision of needed construction aggregates, thus protecting natural diminishing resources of aggregates.

Experimental study on the effect of fly ash content in cemented paste backfill on its anti-sulfate erosion

ABSTRACT In order to study the effect of fly ash content in cemented paste backfill (CPB) on its anti-sulfate erosion, the apparent phenomenon, strength development, and hydration products change the law of CPB with different fly ash content under long-term soaking of 5% sodium sulfate solution were studied by the macrotest and microanalysis, in addition, the mechanism of CPB anti-sulfate attack was analyzed by combining with a scanning electron microscope (SEM). The results indicated that the effect of sulfate environment on the strength of fly ash cemented paste backfill (FCPB) was mainly determined by the hydration products in the FCPB at different soaking times. In the early soaking stage, the formation of ettringite (AFt) in FCPB could improve its compactness, which was conducive to improving the strength of FCPB. In the late soaking stage, there were ettringite-type erosion damage and gypsum erosion-type damage internal of the FCPB with low content fly ash, resulting in microfracture, cracking of the FCPB, and reducing the strength. CPB with an appropriate content of fly ash could improve the internal structure of the FCPB to achieve the purpose of anti-sulfate erosion.

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Strength Prediction Model of High Strength Fly Ash Concrete Based On Mixed Kernel Function

In this paper, the proportion of fly ash in cementitious material, the amount of cementitious material and the ratio of water to cement are selected, and the rough set theory is used to process the data. A mixed kernel function support vector machine prediction model with conditional attribute as input and decision attribute as output is established to explore the influence of three factors on the strength of high strength fly ash concrete. The prediction model with high prediction accuracy is selected for optimization. According to the existing test data, the variation law of concrete strength with proportioning parameters is summarized.

The Effect of Activator to Binder Ratio on the Compressive Strength of Fly Ash Based Geopolymer Mortar in Sulphate Environment

One of the significant characteristic material needed to consider is durability. Sulphate ion contained in soil is one of aggressive agents that could cause degradation of concrete members which led to loss of compressive strength. The current research is to elaborate the effect of activator to binder ratio on the compressive strength of the fly ash based geopolymer mortar in the sulphate environment. Two different types of geopolymer mortar were casted i. e. mortar made of 100% fly ash and mortar contained 95% fly ash + 5% slaked lime. The fly ash used in this research is classified as F fly ash from the Mpanau power plant the variation of activator to binder ratio of 0. 40; 0. 50; and 0. 60, and water/solid ratio variations of 0. 32, 0. 34 and 0. 36. The composition of sulfuric acid was by 5% of the sample volume. Geopolymers mortar compressive strength test is conducted on the immersed samples in a solution of 5% sulfuric acid with age of 0, 7, 14, 28, 56, and 84 days, respectively. The compressive strength test results showed that the highest compressive strength of geopolymers mortar (resistant to sulfuric acid attack) was geopolymers mortar made from fly ash with activator to binder ratio 0. 60, water / solid ratio 0. 32, and percentage of lime to binder 5% at the age of 84 days.

Effect of Sulphuric Acid on Compressive Strength of Fly Ash based Geopolymer Concrete

Effect of Sulphuric Acid on Compressive Strength of Fly Ash based Geopolymer Concrete

The effects of steel fiber waste tyre on properties of high strength fly ash concrete

The utilization of steel fiber from waste tyres can be an alternative to reduce waste tyres due to the increase of tyre production in Indonesia annually. Steel fiber from waste tyre can be added to concrete mix to improve the concrete properties. In this study, the effects of steel fiber waste tyre (SFWT) on high strength concrete containing fly ash was investigated experimentally. The content of fly ash in the high strength concrete is 30% of being partially replaced the cement weight. Steel fiber waste tyres are obtained from extracting the steel wire of the waste tyres and then cut into 4 cm long. The addition of SFWT on the high strength fly ash concrete is 0.5%, 1.0%, 1.5%, and 2% by concrete volume. The mechanical properties of concrete such as compressive strength, tensile strength, and flexural strength are tested at day 28. The test results show that the addition of 2 % SFWT on high strength fly ash concrete increase the compressive strength, tensile strength, and flexural strength of the concrete by around 9.99 %, 63.75 %, 18.18 %, respectively.

Improvement the Properties of High Strength Fly Ash Based Geopolymer Concrete by Using Cement

Geopolymer concrete was introduced to decrease the consumption of Portland cement, reduce the emission of CO2 and produce alternative binders by applying by-products materials such as fly ash. This study the effect of steel fiber on the fresh and hardened properties of geopolymer concrete and also aimed to improve the properties of this type of concrete by replacing the fly ash by Portland cement by 5, 10, 15, 20 and 25% by weight. The results demonstrated that the use of steel fiber leads to improve compressive, splitting tensile and flexural strengths and reduce the flowability and drying shrinkage. The results also showed that the compressive strength of geopolymer concrete increased with increasing the replacement level up to 25%, the increase reached to 40.24 and 34.66% at 7 and 28 days respectively. Splitting tensile strength and flexural strength also increased with the replacement level of fly ash by cement. The results also revealed that the drying shrinkage of fly ash geopolymer concrete increased with cement replacement level.

Investigation of Strength Parameters of PVA Fiber-Reinforced Fly Ash-Soil Mixtures in Large-Scale Direct Shear Apparatus

Soil reinforcement is an old and still efficient technique in improving soil strength and stiffness properties. Current paper aims at quantifying the effects of different inclusions on mechanical behavior of fiber-reinforced cemented soil. An experimental program was conducted to study simultaneous effects of randomly oriented fiber inclusions and cement stabilization on the geotechnical characteristics of fly ash-soil mixtures. Chamkhaleh sand, polyvinyl alcohol (PVA) fiber, cement and fly ash with some water were mixed and compacted into large scale direct shear apparatus with three equal layers. PVA fibers were randomly distributed in three compacted layers at predetermined weight contents. Direct shear tests were carried out on fly ash-soil specimens prepared with different cement, fly ash and polyvinyl alcohol contents, and 7 different curing periods. Results show that cement increases the strength of the raw fly ash-soil specimens. The fiber inclusion further increases the strength of the cemented and uncemented soil specimens and transforms their brittle behavior to ductile behavior. The fiber reinforcement and distribution throughout the entire specimen results in a significant increase in the strength of fly ash -soil- cement mixtures.

Investigation of engineering properties of normal and high strength fly ash based geopolymer and alkali-activated slag concrete compared to ordinary Portland cement concrete

Fly ash-based geopolymer (FAGP) and alkali-activated slag (AAS) concrete are produced by mixing alkaline solutions with aluminosilicate materials. As the FAGP and AAS concrete are free of Portland cement, they have a low carbon footprint and consume low energy during the production process. This paper compares the engineering properties of normal strength and high strength FAGP and AAS concrete with OPC concrete. The engineering properties considered in this study included workability, dry density, ultrasonic pulse velocity (UPV), compressive strength, indirect tensile strength, flexural strength, direct tensile strength, and stress-strain behaviour in compression and direct tension. Microstructural observations using scanning electronic microscopy (SEM) are also presented. It was found that the dry density and UPV of FAGP and AAS concrete were lower than those of OPC concrete of similar compressive strength. The tensile strength of FAGP and AAS concrete was comparable to the tensile strength of OPC concrete when the compressive strength of the concrete was about 35 MPa (normal strength concrete). However, the tensile strength of FAGP and AAS concrete was higher than the tensile strength of OPC concrete when the compressive strength of concrete was about 65 MPa (high strength concrete). The modulus of elasticity of FAGP and AAS concrete in compression and direct tension was lower than the modulus of elasticity of OPC concrete of similar compressive strength. The SEM results indicated that the microstructures of FAGP and AAS concrete were more compact and homogeneous than the microstructures of OPC concrete at 7 days, but less compact and homogeneous than the microstructures of OPC concrete at 28 days for the concrete of similar compressive strength.

Correlation of microstructural and mechanical properties of geopolymers produced from fly ash and slag at room temperature

High strength fly ash (FA)-based geopolymer pastes containing slag were characterized by means of X-ray diffraction (XRD), thermogravimetry (TGA), and environmental scanning electron microscopy (ESEM). Various ratios of FA were replaced with ground granulated blast furnace slag (GGBS) to enhance the early strength development of the geopolymers cured at room temperature. Compressive and flexural strength tests were conducted to determine the mechanical properties, and mercury intrusion porosimetry (MIP) measurements were carried out to investigate the microstructure of the hardened geopolymers. A new pre-conditioning drying method for MIP investigations was applied and its effects on the GPs’ microstructure were evaluated. The comparison of results showed that freeze-drying by using liquid nitrogen could be a great alternative to the conventional drying methods for geopolymers. The compressive and flexural strengths of geopolymers containing slag reached up to around 100 MPa and 10 MPa, respectively. The decreasing porosity of the geopolymers correlated well with the obtained increasing values of the compressive strength. However, neither of them noticeably improved when over 50% of FA was replaced by GGBS, while a further increase in the flexural strength was observed.

PRODUCTION OF FLY ASH BASED GEOPOLYMERS USING ACTIVATOR SOLUTION WITH DIFFERENT Na2O AND Na2SiO3 COMPOSITIONS

In this work, samples of geopolymers were produced by the activation of fly ash with different alkaline solutions (NaOH and NaOH + Na2SiO3). The mechanical strength and microstructural characterization were employed to study the influence of the geopolymerization process in the final proprieties of the binder material. The results showed that the geopolymers have high mechanical strength in the first 24 hours of curing (28 MPa) increasing to 48 MPa after 28 days. The physical proprieties such as water absorption, apparent porosity, and density changed when different solutions were used. The SEM images showed a denser morphology with aluminosilicate gel formation on the surface which is responsible by an increase of mechanical strength of fly ash based geopolymers.

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