High Volume Fly Ash Concrete Research Articles

An Intelligent Approach for Predicting Mechanical Properties of High-Volume Fly Ash (HVFA) Concrete

Plastic waste (PW) is a major soild waste, which its generation continues to increase globally year in and year out. Proper management of the PW is still a challenge due to its non-biodegradable nature. One of the most convenient ways of managing plastic waste is by using it in concrete as a partial substitute for natural aggregate. However, the main shortcomings of adding plastic waste to concrete are a reduction in strength and durability. Hence, to reduce the undesirable impact of the PW in concrete, highly reactive additives are normally added. In this research, 240 experimental datasets were used to train an artificial neural network (ANN) model using Levenberg Marquadt algorithms for the prediction of the mechanical properties and durability of high-volume fly ash (HVFA) concrete containing fly ash and PW as partial substitutes for cement and coarse aggregate, respectively, and graphene nanoplatlets (GNP) as additives to cementitious materials. The optimized model structure has five input parameters, 17 hidden neurons, and one output layer for each of the physical parameters. The results were analyzed graphically and statistically. The obtained results revealed that the generated network model can forecast with deviations less than 0.48%. The efficiency of the ANN model in predicting concrete properties was compared with that of the SVR (support vector regression) and SWLR (stepwise regression) models. The ANN outperformed SVR and SWLR for all the models by up to 6% and 74% for SVR and SWLR, respectively, in the confirmation stage. The graphical analysis of the results further demonstrates the higher prediction ability of the ANN. Doi: 10.28991/CEJ-2023-09-09-04 Full Text: PDF

Structural Characteristics of High Volume Fly ash Concrete Subjected to Elevated Temperature

Structural Characteristics of High Volume Fly ash Concrete Subjected to Elevated Temperature

Hybridisation effect of steel–polypropylene fibres in high-volume fly ash concrete

The paper presents the results of an investigation conducted to investigate the effects of hybrid fibres (polypropylene (PP) and steel (S) fibres on the workability, compressive strength, flexural strength and flexural toughness of high-volume fly ash concrete (HVFAC). Different combinations of PP and S fibres (PP fibre 0–100% and S fibre 100–0%) were incorporated to a total fibre volume fraction of 1.0%. Three different code methods were used for a comparative evaluation of various properties of the HVFAC (toughness, residual strength, cracking strength, etc.). It was found that the mixes with a higher percentage of PP fibre resulted in lower workability as compared to the mixes made with a higher percentage of S fibres. The HVFAC mix made with 25% PP fibre and 75% S fibre showed the best results of all concrete mixes and this combination is thus considered to be the most appropriate for fibre hybridisation in HVFAC.

Residual load capacity of HVFA reinforced concrete after elevated temperature heating: Experimental and analytical study

High volume fly ash (HVFA) is used as structural concrete's main constituent in the current concrete construction practice. The residual load capacity of HVFA reinforced concrete after elevated temperature heating is needed for retrofitting compression members after fire exposure. In this experimental study, an effort has been made to estimate the axial load capacity of concrete containing HVFA after 28 and 90 days of curing after elevated temperature heating at 200 °C, 400 °C and 600 °C. The 35% and 50% amount of cement was partially replaced by fly ash. The weight loss and crack pattern in reinforced HVFA concrete were also studied. It has been observed that after heating at elevated temperature, the compression behavior of fly ash concrete is better than that of plain concrete. The analytical models are proposed to estimate the residual load capacity of HVFA concrete columns after exposure to elevated temperature. The model predictions are reasonably good. These models can be used to assess the load carrying capacity of columns in concrete buildings containing HVFA after elevated temperature exposure for deciding strengthening schemes.

Mix design of equal strength high volume fly ash concrete with artificial neural network

High volume fly ash concrete (HVFAC) has been widely used, and the mix proportion of HVFAC is usually designed based on the required compressive strength. Therefore, the research of HVFAC under the condition of equal strength has more engineering application value. However, in the current mix proportion design standard, there is no special discussion on the mix proportion design method of HVFAC. In this study, the compressive strength of HVFAC affected by four factors (water-binder ratio, FA content, curing method and curing age) was systematically studied. Based on 594 sets of strength data obtained from experiments, the method to determine the key mix proportion parameters (water-binder ratio and FA content) of equal strength HVFAC was proposed through machine learning algorithms (ML). Two ML methods (i.e., a multiple linear regression (MLR) and an artificial neural networks (ANN)) were developed to predict the HVFAC compressive strength and then their performances were compared. Through comparison, it was found that the mean absolute error and root mean squared error of the ANN model were both lower than the MLR model, and the ANN model has lower error and higher accuracy. In addition, the reliability of the proposed ANN model was verified with data in other literatures, the results showed the errors between the predicted values and the measured values are lower than 25%. The weight contribution rate of each factor to the strength was calculated. Among the four factors, the curing age had the greatest impact on the compressive strength, which contributes up to 60.3%. The influence degree of FA content is greater than that of water-binder ratio. With the development of curing age, the influence degree of FA content and water-binder ratio on the strength gradually decreases while the curing method increases. Finally, according to the ANN prediction results, the key mix parameters design method for equal strength HVFAC under multi-factor conditions was proposed, which provide guidance for concrete preparation in actual engineering.

Sulphate and acid resistance of HVFA concrete incorporating nano silica

High Volume Fly Ash (HVFA) concrete has been shown to be a viable alternative construction material to Portland cement concrete to improve sustainability and durability. In addition, nano silica been found to be a significant contributor towards increasing the early age strength and the durability properties of HVFA concrete. This study reports an investigating of the resistance of HVFA concrete with 65% and 80% replacement of cement, with nano silica and hydrated lime, exposed to acid and sulphate solutions over a 2-year period. The change in physical appearance, mass and length was monitored, together with detailed mechanical, chemical and microscopy analysis at 12 and 24 months. The results indicate that the HVFA concrete mixes provided enhanced resistance compared to Portland cement concrete. The HVFA 80% cement replacement performed better in acid media while, the HVFA concrete mix with 65% cement replacement was superior in sulphate media.

Experimental Study on Properties of High volume GGBFS and High Volume Flyash Concrete

Abstract: Construction industry consumes a huge volume of concrete every year and the demand for concrete as a construction material is on the increase. The main ingredient of concrete is cement and India is the second largest producer of cement in the world. The attention to environmental impacts of cement production has grown faster in recent decades. The cement industry is a significant greenhouse gases emitter mainly due to the calcinations of raw materials and the combustions of fuels. Portland cement production is increasing globally and contributes to greenhouse gas emissions. The current contribution of greenhouse gas emission from Portland cement production is about 1.5 billion tons annually or about 7% of the total greenhouse gas emissions[11].This leads to the utilization of wastes and industrial by-products in order to minimize the Portland cement consumption and also focuses on using eco-friendly concrete. In this experimental study There are 13 trials have been conducted on M40 Concrete in this study. out of 13trials , one trial is with control mix, 6 trials with Flyash at 60,70&75% of OPC replacement and the remaining 6 trials with GGBS at 60,70&75% OPC replacement. The investigations are being conducted for the fresh concrete properties like Workability of concrete, Temperature of concrete, Yield of concrete and Air percentage in concrete.

The Effect of Bottom Ash on the Compressive Strength and Tensile Strength of HVFA Concrete

This paper focuses on the effects of High Volume Fly Ash (HVFA) concrete with high content Bottom Ash (BA) as a fine aggregate. A strength target of 45 MPa with 12 � 2 cm slump concrete was determined as a control. The tests that carried out were compressive strength at the age of 3 to 90 days ages and splitting strength at the age of 28 to 90 days ages, slump test, measurement of heat of hydration, and concrete autogeneous shrinkage. Variations in the concrete mix tested were HVFA without BA with FA content of 50% - 80%, and HVFA with 50% BA as a sand replacement. The In general, the use of high volume BA in the HVFA mixture provided an increase in strength both at the initial age and final in all variations. The internal curing effect provided by BA accelerated the hydration and solidification process at the early age, thus giving the effect of increasing the mechanical properties of concrete. However, the acceleration of solidification was accompanied by the increase in the shrinkage. BA properties which have greater absorption compared to sand also caused the workability decreased.

EFFECT OF ADDITION OF CaO ON COMPRESSIVE STRENGTH OF HIGH-VOLUME FLY ASH CONCRETE

When released into the environment as solid waste, the by-product of coal called fly ash (FA) produced by coal-based electric power plants is detrimental. A further 8% to 10% of the worldwide anthropogenic emissions are produced by cement manufacturers. These issues may be resolved with high-volume fly ash (HVFA) concrete. HVFA concrete technology refers to employing fly ash instead of cement in the concrete mix to reduce the manufacturing of cement. But when the amount of fly ash in the concrete mix increases, the concrete’s compressive strength gradually decreases. The objective of this research is to determine the mechanical properties such as the compressive strength of HVFA concrete and compare it to the strength of the control concrete by adding Calcium Oxide (CaO) as an activator. Besides this, this research has another objective to reduce the use of cement in construction by replacing it with fly ash and making an environmentally friendly form of emission of CO2 while producing cement for the cement industry. In this research, different percentages of FA such as 20, 40, 50, 60, 70, and 80 percent are adopted replacing cement in concrete mixes with and without CaO. For this, cylindrical molds with dimensions of 100 mm × 200 mm were used for preparing concrete specimens. For each percentage of HVFA concrete mixtures, 3 (three) molds were cast without the activator and the same with the activator (2% of the binding material). A total of 117 concrete specimens were cast for the compressive strength test. These molds were cured using the water-curing technique. For determining mechanical properties, the compressive strength tests after 7, 28 and 56 days were conducted. Comparisons were made between the compressive strengths of HVFA concrete with and without the activator. These outcomes were contrasted with the compressive strength of the molds of conventional concrete. The early results for the compressive strength of HVFA concrete are extremely poor. The HVFA concrete’s 28-day compressive strength test results demonstrate a much higher compressive strength than the 7-day strength. However, the HVFA concret’s 56-day compressive strength test results were more satisfactory. According to this research, long-term water curing effectively boosts the compressive strength of HVFA concrete. Additionally, the use of CaO as an activator in HVFA concrete results in a minimum of 2 MPa higher compressive strength compared to HVFA concrete without the use of an activator. This result was therefore satisfactory for concrete with the activator content for up to 60% HVFA.

Compressive strength, flexural strength, and durability of high-volume fly ash concrete

Compressive strength, flexural strength, and durability of high-volume fly ash concrete

Sustainable high volume fly ash concrete with recycled C&D waste and dredged marine sand

Cement is a basic building material, and second largest building material used on earth. Huge production and use of cement has led to more CO2 being released into the atmosphere, worsening global warming and negatively affecting the environment. As a result, adopting a more sustainable strategy and carefully examining the current admixtures used to replace traditional concrete has become essential. In order to achieve the use of sustainable materials in construction, numerous studies have been done on replacing the cement with a maximum (50%) percentage of Fly Ash which has equivalent strength and better durability than traditional concrete. Very little literature has been reported on developing sustainable concrete mixers by replacing the course and fine aggregates using industrial waste materials. In this study, the M25 mixture design of High Volume Fly Ash (HVFA) Concrete is carried out with an optimum amount of Fly ash (50%) as cementitious material with OPC (50%). This mix percentage of the cementitious element is obtained after various trials and errors with 40, 50, and 60 percent of fly ash. Due to the pozzolanic characteristics of the fly ash and the lower w/cm ratios, the HVFA mixes achieved comparable greater long-term compressive strengths. In present investigation, coarse aggregate was replaced with recycled C&D waste (RCA) and fine aggregate with dredged marine sand (DMS) at its optimum percentage of 25% and 10%, respectively, to get the compressive strength of 30 MPa. This optimum percentage of Recycled C&D waste and dredged marine sand was obtained after conducting various trials and errors with each material, respectively. Evaluation of compressive strength test and flexural strength test determines the mechanical properties of HVFA concrete with RCA and DMS aggregate as replacement of coarse and fine aggregates.

Properties of High volume GGBFS and High Volume Flyash Concrete: A Brief Review

Abstract: In India, the annual production of GGBS is 15 million tons and only 55% of GGBS is used in the construction industry. It is therefore important to increase the use of industrial waste on a larger scale for environmental benefits in the concrete industry. Numerous studies have been performed on these SCMs to evaluate the properties of his GGBS-containing concrete in fresh and cured states. Using by-products of the slag industry to higher replacement levels for cement could significantly reduce the price of concrete. Paving economical and environmentally friendly concrete Green house gas (GHG) emissions are effectively reduced by 47.5% by using GGBS as a cement substitute. India is the largest producer of fly ash. In one year he produces more than 112 million tons of fly ash. 60-70% of the fly ash is consumed and the rest is spread over the ground. This is because the government encourages the use of his 100% fly ash to avoid landfills and create a greener environment.

Evaluating the effect of steel fibers on the mechanical performance of high-volume fly ash concrete

The construction sector contributes significantly to environmental degradation by completely depleting energy resources. Cement industry emissions are the most significant contributors to climate change along with global warming. To address this issue, researchers are investigating different materials with cementing properties thereby replacing the cement in concrete either partially or completely. Various materials such as different types of ashes and slags have been effectively utilized as cement substitutes thereby making the concrete sustainable. Partial substitution of cement with fly ash has a positive impact on the overall performance of concrete but the incorporation of fly ash at a higher volume into the concrete reduces its characteristics. The objective of this work was to improve the overall performance of High-Volume Fly-Ash concrete by incorporating steel fibers with varying volume fractions. From this study, it can be inferred that reinforcing with steel fibers up to 1.2% fiber volume has compensated for the negative effect of HVFA by improving the overall properties.

Flexural behaviour and ultimate bending capacity of high-volume fly ash reinforced concrete beams

Large number of studies analyzed physical and mechanical properties of high-volume fly ash concrete, but only a few discussed its structural behavior. Material properties are an important input parameter for structural analysis, but they are insufficient for reliable conclusions to be made. This study analyses flexural behavior of reinforced concrete beams made with 63% of low-calcium class F fly ash in total cementitious materials mass, using experimental method and analyzing current code predictions (EN 1992-1-1). The analysis was done by comparing beams made with two longitudinal reinforcement ratios, made with traditional cement concrete (OPC) and high-volume fly ash concrete (HVFAC), both corresponding to concrete class C30/37. Beams were tested in a four-point bending test measuring vertical displacement, crack development, concrete strains and longitudinal reinforcement strains. According to this research, the flexural performance of HVFAC beams is similar to flexural performance of corresponding OPC beams in terms of ultimate bending capacity. The significant difference was noticed regarding cracking extent that was higher in HVFAC beams. Available ultimate bending moments code predictions can be applied on HVFAC beams with similar precision and variation of results, like for OPC beams. However, this cannot be concluded for parameters depending on the cracking behaviour, like cracking moments or deflections. Results and analysis presented in this study indicate that HVFAC can be used in structural elements subjected dominantly to bending, like beams and slabs. More research regarding structural behavior of HVFAC using full-scale long-term tests is needed to develop larger database for reliability analysis.

Green Concrete: An Eco-Friendly Alternative to the OPC Concrete

The popularity of concrete has resulted in the considerable consumption of natural resources and significant emission of CO2 gas into the atmosphere. The key constituents of the concrete are the cement and the natural aggregates. These major concrete elements are recommended to be replaced with other materials to solve sustainability issues. Hence, by-products like pulverized granular blast-furnace slag, fly ash, rice husk ash, silica fume, recycled coarse aggregates etc., are added to the concrete to utilize the waste products and produce sustainable concrete. Cement manufacturing accounts for 8 to 10% of total global CO2 emissions. The construction industry is progressively adopting green concrete use in buildings because of its inherent benefits and limitations of traditional concrete. Green concrete is available in a variety of forms such as high-volume fly ash concrete, alkali-activated concrete, recycled aggregate concrete, ultra-high performance concrete, geopolymer concrete etc. Green concrete has various environmental, technical, and economic advantages i.e., greater durability, enhanced workability, and pumpability, decreased permeability, controlled bleeding, higher acid resistance, and decreased plastic shrinkage cracking. These properties encourage faster concrete production, shorter curing times, lower construction costs, earlier project completion, lower maintenance costs, and longer service life of construction projects. This review article aims to comprehensively explain the fresh, hardened, and durability properties of green concrete and knowledge gaps in green concrete. The literature revealed that further research is needed to accurately assess the long-term properties, notably creep and shrinkage behaviour of structural or reinforced elements of green concrete.

Frost durability of high-volume fly ash concrete: Relation liquid transport - damage

Transport is central for frost deterioration, though playing different roles before/after starting freeze/thaw. Liquid uptake (LU) during rapid freeze/thaw in water (RF) and frost/salt test (FS) and relations LU-scaling and -internal damage were investigated on non- and air-entrained (AE) concrete (w/b = 0.29–0.45, 50–130 MPa). 8–22 % of the air-voids became waterfilled during water-curing. Absorption during pre-saturation in FS correlated to initial scaling but without general LU - salt scaling correlation. LU (kg/m2) was lower in RF than in FS, indicating different transport/damage mechanisms. In RF, LU correlated to cracking and scaling (especially well-cured concrete). Air entrainment always reduced LU. FS to −52 °C increased both LU and scaling for internally damaged concretes compared to −20 °C but did not affect LU in undamaged well-cured concretes. Modelled and measured LU during RF correlated very well and indicates hydraulic pressure is more important than cryosuction for reducing LU in AE concrete.

Hydration and Mechanical Properties of High-Volume Fly Ash Concrete with Nano-Silica and Silica Fume.

This study investigated the effects of nano-silica (NS) and silica fume (SF) on the hydration reaction of high-volume fly ash cement (HVFC) composites. In order to solve the dispersibility problem caused by the agglomeration of NS powder, NS and NSF solutions were prepared. NS content and SF content were used as main variables, and an HVFC paste was prepared in which 50% of the cement volume was replaced by fly ash (FA). The initial heat of hydration was measured using isothermal calorimetry to analyze the effects of NS and SF on the initial hydration properties of the HVFC. In addition, the compressive strength was analyzed by age. The refinement of the pore structure by the nanomaterial was analyzed using mercury intrusion porosimetry (MIP). The results show that the addition of NS and SF shortened the setting time and induction period by accelerating the initial hydration reaction of HVFC composites and improved the compressive strength during the initial stage of hydration. In addition, the micropore structure was improved by the pozzolanic reaction of NS and SF, thereby increasing the compressive strength during the middle stage of hydration.

Compressive Behavior and Durability Performance of High-Volume Fly-Ash Concrete with Plastic Waste and Graphene Nanoplatelets by Using Response-Surface Methodology

Plastic waste (PW) generation continuously increases every year due to the growing population and demand for plastic materials. This situation poses a challenge to many countries, including developed ones, on how to dispose of PW. Accordingly, PW was utilized in this study to replace coarse aggregates partially in high-volume fly-ash (HVFA) concrete. However, PW decreased the strength and durability of concrete. To address this issue, graphene nanoplatelets (GNPs) were added to mitigate the negative consequences of PW and HVFA on concrete’s properties. The objective of this study is to investigate the influences of PW and GNP contents on the durability and deformation of HVFA concrete. Response-surface methodology (RSM) was used to design and optimize a series of cement mixes to achieve the most desirable properties. Independent variables included PW content as partial replacement for coarse aggregates (0%, 15%, 30%, 45%, and 60% by volume), fly ash as partial substitute for cement (0%, 20%, 40%, 60%, and 80% by volume), and GNPs as additives (0%, 0.075%, 0.15%, 0.225%, and 0.3%). The considered responses were concrete unit weight, modulus of elasticity (MoE), and Cantabro abrasion loss at 300 revolutions. Results showed that PW and HVFA decreased concrete unit weight and MoE but increased Cantabro abrasion loss. By contrast, GNPs increased concrete unit weight and MoE but decreased Cantabro abrasion loss. PW and HVFA also increased the compressive toughness and porosity of concrete, while GNPs increased its stiffness but decreased its compressive toughness and porosity. The mathematical models developed to predict the unit weight, MoE, and abrasion resistance of concrete were significant, with errors of less than 6%. An optimized mix was achieved by partially replacing 12.44% of coarse aggregates with PW and 24.57% of cement with fly ash and adding 0.279% GNPs with a desirability of 100%.

Effect of Proposed Accelerated Curing Method on High Volume Fly Ash Concrete

In the modern construction practice high amounts of fly ash are not accepted by the construction industry due to a slower rate of strength gain at early age. A study has been undertaken to hasten the hydration process by proposed accelerated curing method of high volume fly ash concrete. Large amount of cement (up to 70% by weight) has been replaced by fly ash. The test results of the compressive strength of accelerated cured mixtures gives about (87-100)% strength ratios from itsa28 days compressive strength within one day only. That indicates, the compressive strength at 28 days can be achieved within 1 day only by using proposed accelerated curing. The results of drying shrinkage show that, the drying shrinkage of mixtures under conventional and accelerated curing conditions are comparable and these results add further benefit of this proposed accelerated curing. Key word: accelerated curing, high volume fly ash , curing cycle, drying shrinkage, flow ability.

Performance and life-cycle assessment of high-volume fly ash concrete mixes containing steel slag sand

The present study discusses the performance of high-volume fly ash concrete (HVFAC) mixes containing slag sand which is a solid waste obtained from basic oxygen steel making industry. The design of such mixes was optimized to attain sufficient strength for structural purposes and then cement and natural sand in them were replaced with fly ash and slag sand up to 50%. Other than temperature developments, their fresh and hardened properties like slump, air content, compressive and tensile strengths, elastic modulus, strain softening response under uniaxial compression, shrinkage, water permeation, sorption and absorption, chloride ions diffusion and migration, and bulk electrical resistance at different ages were also studied in detail. The impact of fly ash and slag sand on the sustainability of such mixes were assessed and their co-effects on concrete microstructure were discussed with the results of scanning electron microscopy and Mercury intrusion porosimetry. The HVFAC mixes displayed a slower strength increase at early ages, but they were found to be highly workable, durable, and temperature rise in them was comparatively lower. The strength and durability of these mixes at early ages were found to enhance in the presence of slag sand which is generally capable of strengthening the aggregate-paste interface. India is the second largest producer of cement in the world. Both the fly ash and slag sand possess a lower energy requirement and their inclusions led to the production of eco-friendly concrete which is highly desirable for Indian conditions.