Amount Of Fly Ash Research Articles

Innovative Utilization of Fly Ash in Geotechnical Engineering: An Analytical Review Supported by Extensive Geotechnical Testing

Extensive study has been conducted on the use of fly ash as an additive in soil and geotechnical engineering projects due to its capacity to enhance soil properties and the efficacy of geotechnical structures. Various fly ash samples had distinct elemental compositions; nevertheless, the chemical analysis indicated that Sample 3 possessed the highest silica content (55%), which corresponded with enhanced pozzolanic reactivity. The physical property tests revealed significant disparities; for instance, Sample 2 exhibited the smallest particles at 18 microns, but Sample 5 had the highest specific gravity at 2.5. This indicates that the qualities of the soil may alter when mixing these samples. The maximum dry density climbed to 2050 kg/m³, and the cohesive strength to 25 kPa with higher quantities of fly ash, as shown by geotechnical testing findings, which also revealed trends in shear strength parameters and compaction characteristics with varying fly ash concentrations. These findings underscore the potential of fly ash in geotechnical applications for soil stabilization, compaction enhancement, and load-bearing capacity augmentation. Optimizing soil behavior becomes feasible via the judicious use of fly ash, as shown by the enhancements in soil engineering properties found. Fly ash may be used in a few geotechnical applications, yet proper evaluation of its composition and physical properties, any adverse environmental and structure interaction with time must be made before applying the product. The present research focuses on the fly ash as the soil adding material and the direction of its activating material to the geotechnical built environment contributes significant knowledge of its application.

A study of the shear strength properties of expansive soil treated with fly ash admixture

The behavior of clay minerals in expansive soils causes them to exhibit shrink-swell characteristics, making them unsuitable for engineering purposes in their natural state. To address this problem, researchers conducted direct shear experiments using fly ash as an admixture and black cotton soil as an expanding soil to explore the strength parameter. The experiments were conducted with varying amounts of fly ash ranging from 2% to 20%. Two arrangements of test series were made, and in the principal series, tests were made utilizing five unique densities and comparing dampness contents. The outcomes showed that the point of inside grating and union expanded directly up to the ideal dampness content and most significant dry thickness before diminishing. The subsequent series showed that the end of inward rubbing grew straightly with the expansion of fly debris admixture, yet attachment reduced after 10% admixture. The decrease in shear strength was because of the diminished passion, as the fly debris' cohesionless attributes took over as the admixture rate increased above 10%. Based on these findings, adding fly ash in small quantities to black cotton soil is recommended to avoid weakening it.

Experimental investigation on strength characteristics of autoclave aerated concrete block using natural pozzolanas

In this present study we have studied about the strength enhancement of autoclaved aerated block by using natural pozzolanas. Fly ash has been partially replaced with GGBS. GGBS has been used in place of fly ash at percentages of 6%, 12%, and 18% of the total amount of fly ash plus super plasticizer. GGBS improves resistance to damage from alkali silica reaction. It also reduces the thermal cracking. The role of super plasticizer is to reduce the water content in block.we have used 1% of super plastizer to the 1 litre of water. Each block's compressive strength is measured and computed for varying fly ash and GGBS ratios. It has been observed that replacing GGBS with 12% yields higher compressive strength than replacing it with 6% or 18%.

Reinforced soil retaining wall for ash handling facility Java 9 and 10 coal-fired steam power

The construction of coal ash handling facilities requires a large area to store large amounts of Fly Ash and Bottom Ash (FABA) material. Bund wall is proposed near the facility to be built FABA stockpile up to EL.+80.0. The area of the proposed bund wall is very limited, so a vertical earth retaining wall is proposed to maintain the FABA backfill as well as support the proposed Hauling Road. In this case, Geoforce Segmental Retaining Wall (GSRW) is adopted as one type of soil reinforcement, the construction is a combination of reinforcing elements in the form of geosynthetic strip (GI Strips) that interact with the filling material through friction and provide tensile capacity. The combination works as a gravitational structure capable of withstanding lateral ground pressure. This GI Strip material is produced in Indonesia so that it has a high “Tingkat Komponen Dalam Negeri” (TKDN) value. GSRW works are 820 m long with a height of 19.44 m. The analysis carried out was assisted by the PLAXIS 3D program to understand the deformation in the structure and obtain safety factors according to the requirements in “SNI Persyaratan Perancangan Geoteknik 8460:2017”.

Electrical Discharge Coating of Mild Steel with Fly Ash Suspension

Mild steel is a soft substance that rusts easily. It is easy to wear and corrode when exposed to harsh circumstances, such as in manufacturing sector. As a result, the mild steel surface must be modified to boost its durability and wearability. There are various techniques for coating mild steel and one of them is electrical discharge coating (EDC). In this study, the surface of mild steel was modified using EDC with fly ash suspension. Prior to the experiment, the element content, particle size, and surface morphology of fly ash were investigated. The EDC process was carried out using a Sodick AQ35L die-sinker EDM machine. The effects of varied amounts of fly ash on the features of the coated surface were also investigated. The experimental results revealed that raising the fly ash content increases the micro-hardness of the coated surface. Furthermore, utilising 20 g/l of fly ash powder resulted in the best coated surface finish with the least surface roughness. The concentration of fly ash has a significant impact on the thickness of the coating layer. These findings substantiate the viability of recycling fly ash as an environmentally sustainable coating material for modifying mild steel surfaces through the EDC method.

Efficiency and Mechanism of Surface Reinforcement for Recycled Coarse Aggregates via Magnesium Phosphate Cement.

Recycled aggregate concrete (RAC) exhibits inferior mechanical and durability properties owing to the deterioration of the recycled coarse aggregate (RCA) surface quality. To improve the surface properties of RCA, the reinforcement efficiency of RAC, and the maneuverability of the surface treatment method, this study used magnesium phosphate cement (MPC), a clinker-free low-carbon cement with excellent bonding properties, to precoat RCA under three-day pre-conditioning. Moreover, variable amounts of fly ash (FA) or granulated blast furnace slag (GBFS) were utilized to partly substitute MPC to enhance the compressive strength and chloride ion penetration resistance. Subsequently, FA-MPC and GBFS-MPC hybrid slurries with the best comprehensive performance were selected to coat the RCA for optimal reinforcement. The crushing value and water absorption of RCA, as well as the mechanical strengths and durability of RAC, were investigated, and microstructures around interfaces were studied via BSE-EDS and microhardness analysis to reveal the strengthening mechanism. The results indicated that the comprehensive property of strengthening paste was enhanced significantly through substituting MPC with 10% FA or GBFS. Surface coating resulted in a maximum reduction of 8.15% in the crushing value, while the water absorption barely changed. In addition, modified RAC outperformed untreated RAC regarding compressive strength, splitting tensile strength, and chloride ion penetration resistance with maximum optimization efficiencies of 31.58%, 49.75%, and 43.11%, respectively. It was also evidenced that the improved MPC paste properties enhanced the performance of modified RAC. Microanalysis revealed that MPC pastes exhibited an excellent bond with RCA or new mortar, and the newly formed interfacial transition zone between MPC and the fresh mortar exhibited a dense microstructure and outstanding micro-mechanical properties supported with an increase in the average microhardness value of 30.2-33.4%. Therefore, MPC pastes incorporating an appropriate mineral admixture have enormous potential to be utilized as effective RCA surface treatment materials and improve the operability of RCA application in practice.

The sulfate transfer characteristics in recycled aggregate concrete incorporated with fly ash under percolation theory

Recycled aggregate concrete (RAC) has multiple interface transition zones (ITZs) due to its complex composition, providing convenient ion transfer channels. Therefore, it is significant to explore the changes of the internal pore structure in RAC under ion erosion conditions for quantifying and predicting ion transfer mechanisms. This paper innovatively utilizes the seepage effect for investigating the evolution of pore structures in RAC under sulfate attack. We conduct a systematic experimental study on the transport of sulfate ions in RAC with different fly ash (FA) substitution rates under dry-wet cycles. Combining backscattered electron imaging (BSE), permeation and fractal characteristics, this paper deeply explore the relationship between pore structure feature, sulfate percolation mechanism and the macroscopic properties of RAC incorporated with different amount of FA.

Ultra‐fast curing of benzoxazine with surface modified fly ash‐assisted microwave: Achieving excellent comprehensive performances

AbstractBenzoxazine has aroused a lot of research interest because of its high mechanical performance and excellent thermal stability in polybenzoxazines. However, it suffers from its high curing temperature and long curing time, which necessitate resolution. This study addresses this issue by employing a surface‐modified fly ash‐assisted microwave curing method to achieve ultra‐fast benzoxazine curing within 15 min. The impact strength of the resulting cured product displayed an increasing‐then‐decreasing trend with the addition of fly ash, reaching a maximum impact strength of 18.71 ± 1.20 kJ/m2 at a 3% fly ash content. This value is 113.3% higher than the impact strength of pure PBA‐a. Additionally, when using the same amount of fly ash, the microwave‐cured product exhibited a flexural strength of up to 135.9 MPa and a flexural modulus of up to 6.71 GPa, surpassing those of pure PBA‐a by 28.7% and 33.1%, respectively. Moreover, the glass transition temperature (Tg) increased by 19.56°C. Furthermore, there was a slight improvement in flexural strength compared to the heat‐cured product, and no significant loss in thermal properties was observed. The method demonstrated in this study presents a novel approach for the rapid molding and preparation of benzoxazine in composites.

Effect of Accelerators on High Early Strength Concrete (HESC) Using High Volume Fly Ash

Applying large quantities of fly ash for the production of High Early Strength Concrete (HESC) is a challenge for researchers in the utilization of quality, inexpensive, and environmentally friendly materials. A high volume of fly ash in concrete, however, reduces the initial compressive strength of the concrete. For this reason, it is necessary to use admixture additives in the concrete mixture to get the expected performance. This research seeks to identify the optimal HESC mix design using fly ash 50% of the total cementitious by adding a superplasticizer and accelerator to obtain a high initial compressive strength. Three variations of HESC, namely HESC-12, HESC-14, and HESC-16, were made using a superplasticizer and accelerator with different doses. Each variation uses 12 liters of superplasticizer and different accelerator volumes: 12 liters, 14 liters, and 16 liters. Specimen testing was carried out on fresh and hard concrete. Fresh concrete was subjected to a slump test, whereas hard concrete was subjected to compressive tests at 18 hours, 24 hours, 3 days, and 28 days of age. The average slump flow values for HESC-12, HESC-14, and HESC-16 (cm) were 78, 79.5, and 80, respectively, demonstrating that all HESC samples are classified as self-compacting concrete (SCC). According to the results of density tests conducted on all specimens ranging from 2461 to 2538 kg/m3, all specimens are included in the category of normal-weight concrete. Within the range of 29.8 to 35.3 MPa for the initial compressive strength of HESC at 24 hours of age, it can be concluded that all HESC specimens fulfill the criteria for high early-strength concrete. The addition of the right type and dosage of chemical admixture is a solution to overcome the weakness of applying fly ash in high-early-strength concrete.

Utilization of waste foundry sand and fly ash in the production of steel fibre reinforced concrete

As the main raw materials for concrete preparation, natural sand and cement are in increasing demand. Meanwhile, the large accumulation of waste foundry sand (WFS) and fly ash (FA) seriously pollutes the environment. The research on the application of waste materials in concrete preparation has become a hotspot for scholars. This study attempts to respectively use WFS and FA to substitute natural sand and cement in the preparation of steel fibre reinforced concrete (SFRC). 3-factor, 3-level orthogonal experiment was designed, and the study variables include the WFS substitution rate (20%, 40%, and 60%), FA substitution rate (10%, 20%, and 30%), and SF content (1%, 2%, and 3%). The workability, dry density and mechanical properties of concrete were tested and discussed. Range analysis and variance analysis were used to analyse the effect of various factors on the different properties of concrete. Efficacy coefficient method was used to specifically determine the optimum substitution rate of waste materials for raw materials. Additionally, microanalysis was carried out to investigate the influencing mechanism of waste materials on the properties of concrete. It was observed that the workability of concrete deteriorated with the addition of waste materials, while the change of mechanical properties closely correlated with the content of waste materials. The workability and compressive strength were most significantly affected by the WFS content, while the density, tensile strength, flexural strength and elastic modulus were most significantly affected by the SF content. The mechanical properties of concrete were optimum at 34%, 20% and 2.3% of WFS, FA and SF content respectively. In this case, the compressive strength, split tensile strength, flexural strength and elastic modulus increase by 28.8%, 33.5%, 33.8% and 17.7% respectively compared to the control concrete. Microanalysis proved that moderate amount of WFS and FA could increase the beneficial pores, decrease the harmful pores, and reduce the porosity of concrete, but excessive WFS (60%) and FA (30%) would inhibit the hydration process and enlarge the porosity of concrete. This study demonstrates the feasibility of the application of WFS and FA in SFRC preparation, contributing to overcoming the pollution of waste material accumulation and alleviating the shortage of natural resources.

Effect of Potassium Feldspar Sodium-feldspar Composite Flux on The Sintering Performance of Fly Ash-coal Gangue-phosphogypsum Based Wall Insulation Materials

In this paper, fly ash and coal gangue as the main raw materials, potassium feldspar-albite as the composite flux, phosphogypsum as the bonding agent, the semi-melting method was used to prepare fly ash-coal gangue-phosphogypsum based wall insulation material, the effect of composite flux ratio and the amount of coal gangue added on the melting temperature of wall insulation material was studied. Through the visual of high-temperature deformation analyzer to observe the volume contraction, expansion, passivation, and globalization of different formulations of specimens at high temperatures, and record the corresponding temperatures of the occurrence of various situations, to study the composite flux ratio and gangue addition on the fly ash-gangue-phosphogypsum based wall insulation material melting temperature of the impact, to determine the appropriate ratio of the flux and the gangue addition for the solid waste-based will provide a theoretical basis for the preparation of solid waste-based wall insulation materials. The research results indicate that with the increase of coal gangue content, the initial melting temperature, spheroidization temperature, and passivation temperature of the sample all sharply decrease. With the increase of potassium feldspar: albite, the melting temperature range will significantly increase. When the additional amount of fly ash is 50%, the additional amount of coal gangue is 12%, the additional amount of phosphogypsum is 5%, and the ratio of potassium feldspar to albite is 1:1, the sintering temperature of the fly ash- gangue -phosphogypsum based wall insulation material is the lowest.

Literature Review: High Volume Fly Ash Concrete

The construction industry is experiencing immense pressure for substitutes for traditional building materials in the modern world. In the first half of 2020–2021, just under 57.93 percent of the total amount of fly ash generated in the nation was reused. The remaining material was thrown away of in landfills, spewing toxic substances into the immediate vicinity. Numerous creative proposals have been put forward all around the world that aim to increase the average amount of fly ash utilized during constructing. The most promising domains are geo polymer and high volume fly ash concrete construction. This study encompasses the research undertaken on each of these areas by an assortment of professionals internationally. Their attempts paid off, yielding concrete that exhibited barely any heat accumulation during its hydration process negligible sagging, enhanced versatility, and a modest dense utilizing a a great deal of ash from fly ashes. The outcomes derived from geo polymer concrete construction comprised outstanding durability, acidic obstructions, plus an elevated fly ash content, with characteristics analogous with that from Rcc constituents. Furthermore, the a project-specific strategy prescription is anticipated to be generated

Prediction of compressive strength of nano-silica modified engineering cementitious composites exposed to high temperatures using hybrid deep learning models

This study estimated the compressive strength of nano-silica-modified engineering cementitious composites subjected to high temperatures using innovative hybrid deep learning models. The innovative hybrid models in this study were designed using autoencoder (AE)-decision tree (DT) and autoencoder (AE)-extreme learning machine (ELM). Additionally, ELM, DT, and deep AE models in this study were designed to compare the results of innovative hybrid deep learning models. The sensitivity analysis was used for the statistical assessment of the experimental results. The input variables of the models were selected as the cement amount, fly ash amount, sand amount, water amount, high-range water reducer amount, PVA (polyvinylalcohol) fiber amount, nano-silica amount, and the degree of exposure to high temperatures. The compressive strength was used as the output variable of the models. The mixture ratio in the experimental study was 583 kg/m3 cement, 467 kg/m3 sand, 700 kg/m3 fly ash, 187 kg/ m3 water, PVA fiber (0.5 %, 1 %, 1.5 % and 2 %) and nano silica (0 %, 1 %, 2 %, 3 % and 4 %) were used. The ELM, DT, and deep AE models estimated the compressive strength of nano-silica-modified engineering cementitious composites subjected to high temperatures with 93.86 %, 77.35 %, and 86.5 % accuracy, respectively. Also, the same compressive strength was estimated with 94.28 % and 98 % accuracy using the hybrid deep AE-DT and AE-ELM models. This study found that the innovative hybrid deep AE-ELM model predicted compressive strength with higher accuracy than the deep AE-DT, DT, ELM, and deep AE models. Additionally, the deep AE-DT model predicted compressive strength with higher accuracy than non-hybrid models. Thus, it can be stated that innovative hybrid deep models are more advantageous than other models in estimating the compressive strength of ECC. The sensitivity analysis obtained that the PVA fiber was the most significant variable affecting the compressive strength results of nano-silica-modified engineering cementitious composites subjected to high temperatures.

Computing of temperature-dependent thermal conductivity and viscosity correlation for solar energy and turbulence appliances via artificial neuro network algorithm

The growing popularity of artificial intelligence approaches has led to their application in a wide range of engineering fields. The most widely used artificial intelligence tool, artificial neural networks, can be used to predict data with high accuracy. An artificial neural network approach is being used to predict effective and accurate thermal conductivity and viscosity models for hybrid nanofluid systems. Here, new types of correlations relating to the thermophysical properties of Fly Ash–Cu nanoparticles with diameter sized 15.2[Formula: see text]nm and which are temperature-dependent are developed. The highest thermal conductivity and viscosity values were obtained for hybrid nanofluids with a mixture ratio of 20:80, with maximum amplification exceeding 83.2% and 65%, respectively, over the base fluid. The Fly Ash–Cu/water hybrid nanofluid’s viscosity and thermal conductivity are evaluated for a concentration range of 0–4%. The evaluation of the Fly Ash–Cu/water hybrid nanofluids system at concentrations ranging from 0 to 4% most likely entails a scientific or engineering study aimed at understanding the behavior and properties of this nanofluid mixture. Nanoparticles can agglomerate or settle in the base fluid over time, compromising the stability of the nanofluids. Researchers may be interested in determining how varied quantities of Fly Ash and Cu nanoparticles affect the nanofluid’s stability and sedimentation behavior. The heat transfer potential is examined within the optimistic range of temperatures of 30–80∘C. Many fruitful results for turbulence and solar energy have been drawn. The Mouromtseff number achieved an optimal value for all concentration levels. The heat transfers of turbulent flow and thermal conductivity of hybrid nanofluids increase with the augmented values of concentrations and temperature. Researchers found an increase in thermal conductivity of hybrid nanofluids at 0–4% concentrations, potentially impacting heat transfer applications. The conclusion explores the potential integration of the developed correlations and neural network model into practical engineering or industrial applications involving solar energy and turbulence appliances. In this work, we extend the work of Kanti et al. [Sol. Energy Mater. Sol. Cells 234 (2022) 111423] which is on the properties of water-based fly ash-copper hybrid nanofluid for solar energy applications.

High-strength high-performance concrete incorporating different macro fiber types and contents: Engineering and durability performance

ABSTRACT Generating a synergistic response by combining the advantages of different fiber types in concrete is of current scholarly interest. This study investigated the effects of different hooked-end steel fiber (SF) volume fractions up to 1.6% and three macro fiber types including polypropylene (PP), SF, and typical hybrid fibers (HF: 50% SF + 50% PP) at a fixed dosage of 1.6% on properties of high-strength high-performance concrete (HSHPC). A novel densified mixture design algorithm was used to incorporate a high quantity of fly ash and rice husk ash as an eco-binder. Results showed the specimens with added macro SF exhibited improved mechanical strength, dynamic modulus of elasticity and rigidity, and lower drying shrinkage while the ones with added PP exhibited reductions in compressive strength and dynamic modulus. Interestingly, the incorporation of macro fibers, regardless of fiber type and content, reduced electrical resistivity, ultrasonic pulse velocity and increased the total charge passed in the chloride ion penetration test, resulting in likely underestimation of the reinforcement corrosion resistance, especially for SF specimens. The findings also confirm that HF demonstrating synergistic response may be effective and creative in improving most of the concrete characteristics, contributing to the efficient use of HSHPC in real-world structures.

Comparative analysis of various machine learning algorithms to predict 28-day compressive strength of Self-compacting concrete

Construction industry is indirectly the largest source of CO2 emissions in the atmosphere, due to the use of cement in concrete. These emissions can be reduced by using industrial waste materials in place of cement. Self-Compacting Concrete (SCC) is a promising material to enhance the use of industrial wastes in concrete. However, there are very few methods available for accurate prediction of its strength, therefore, reliable models for estimating 28-day Compressive Strength (C–S) of SCC are developed in current study by using three Machine Learning (ML) algorithms including Multi Expression Programming (MEP), Extreme Gradient Boosting (XGB), and Random Forest (RF). The ML models were meticulously developed using a dataset of 231 points collected from internationally published literature considering seven most influential parameters including cement content, quantities of fly ash and silica fume, water content, coarse aggregate, fine aggregate, and superplasticizer dosage to predict C–S. The developed models were evaluated using different statistical errors including Root Mean Square Error (RMSE), Mean Absolute Error (MAE), coefficient of determination (R2) etc. The results showed that the XGB model outperformed the MEP and RF model in terms of accuracy with a correlation R2 = 0.998 compared to 0.923 for MEP and 0.986 for RF. Similar trend was observed for other error metrices. Thus, XGB is the most accurate model for estimating C–S of SCC. However, it is pertinent to mention here that it does not give its output in the form of an empirical equation like MEP model. The construction of these empirical models will help to efficiently estimate C–S of SCC for practical purposes.

Study of flexural strength of concrete containing mineral admixtures based on machine learning

In this paper, the prediction of flexural strength was investigated using machine learning methods for concrete containing supplementary cementitious materials such as silica fume. First, based on a database of suitable characteristic parameters, the flexural strength prediction was carried out using linear (LR) model, random forest (RF) model, and extreme gradient boosting (XGB) model. Subsequently, the influence of each input parameter on the flexural strength was analyzed using the SHAP model based on the optimal prediction model. The results showed that LR, RF, and XGB enhanced the accuracy of forecasting sequentially. Among the characteristic parameters, the most significant effect on the flexural strength of concrete is the water-binder ratio, and the water-binder ratio shows a negative correlation with flexural strength. The effect of maintenance age on flexural strength is second only to the water-binder ratio, and it shows a positive trend. When the amount of fly ash is less than 40% and the amount of slag or silica fume is less than 30%, the correlation between the amount of supplementary cementitious materials and flexural strength fluctuates and a positive peak in flexural strength is observed. However, at a dosage greater than the above, the supplementary cementitious materials all reduce flexural strength. The interaction interval and the degree of interaction between the supplementary cementitious materials and the cement content also differ in predicting flexural strength.

Use of Flyash and Plastic Waste as a Constituent in Concrete

Cement production gives rise to CO2 emissions generated by calculations of CaCO3 and by fossil, being responsible for about 5% of the CO2 emissions in the world. This can be substantially reduced if cement replacement materials, either partial or complete such as fly ash are used. Presently large amounts of fly ash are generated in thermal industries with an important impact on the environment and humans. In recent years many researchers have established the use of supplementary cementitious materials (SCM) like flyash (FA) not only improves the various properties of concrete both in its fresh and hardened states but also can contribute to economic construction costs. Plastic bags which are commonly used for packing, carrying vegetables, etc create a serious environmental problem. The safe disposal of plastic bags in the environment is the most challenging issue for solid waste management across the globe. These are non-biodegradable and toxic. Every year at least 15% of total plastic waste remains untreated. Concrete is one of the best choices for construction in many countries today. Waste plastic is being tried in the field of construction as a spatial replacement in fine aggregate, coarse aggregate, or as an additive the concrete. In the present study fly ash (FA) is taken as the partial replacement in cement and low-density polyethylene (LDPE) is used as an additive in the concrete. FA was partially replaced in cement at percentages of 10, 20, and 30. Along with the variation of FA, LDPE was also added from 0.2% to 1% in the concrete by volume. Ample number of samples in M20 grade was prepared with a w/c ratio of 0.55 It was found from the result that the optimum compressive strength for 7 days and 28 days were 28.44 N/mm2 and 33.77N/mm2 obtained at 20% percent replacement of FA with 0.4% addition of LDPE Similarly the optimum split tensile strength for 28 days was 2.49 N/mm2 obtained at 20% replacement of FA with 0.8% addition of LDPE. Thus 20% FA with up to 0.4% LDPE can be adopted so that the disposal of waste plastic and fly ash can be done well as well and the efficiency of the concrete can be managed effectively.

Comparative Analysis of the Use of Nanosilica and Fly Ash in Hydraulic Concrete

Context: Nowadays, nanomaterials constitute an innovative alternative for the construction sector. This study evaluates the benefits of adding nanosilica and fly ash to Portland cement concrete in terms of its mechanical strength properties. Methodology: 45 specimens were used to compare the compressive strength and durability of concrete mixtures with nanosilica and fly ash. The specimens were studied after 7, 14, and 21 days to determine their maximum resistance. Results: The addition of small amounts of nanosilica (up to 1%) significantly improved the compressive strength of the concrete. In contrast, a large amount of fly ash (up to 8%) was required for a noticeable effect. Conclusions: Concrete with nanosilica yielded the best results in terms of mechanical strength. The key to improving concrete through nanosilica and fly ash is to reduce the water-to-cement ratio using chemical agents that reduce porosity and increase resistance.

Preparation of foam concrete from solid wastes: Physical properties and foam stability

The method for preparation of foam concrete from solid wastes were proposed in this study, where soda residue (SR), calcium carbide slag (CS), grand granulated blast-furnace slag (GGBS) and fly ash (FA) were used as raw materials for the binder and Al powder was used as the foam agent. The effects of Al powder, stabilisers and FA content on the dry density as well as compressive strength were assessed to determine the optimal mix proportions. Moreover, to understand the foaming process, the influence of stabilisers on the zeta potential and surface tension of the fresh mixes were measured and Low-Field Nuclear Magnetic Resonance (LF-NMR) was employed to qualitatively characterize the pore size distribution. Finally, the hydration products were analyzed by X-Ray Diffraction (XRD), Fourier transform infrared spectrometer (FTIR), Thermogravimetric Analysis-Differential scanning calorimetry (TGA-DSC), Scanning electron microscope-Energy dispersive X-ray spectroscopy (SEM-EDS). The results suggested that the optimal content of Al powder was 1–2%, and the combination of S and P (SP) stabilisers showed better stabilization effect than the single use of S or P, leading to well distributed foam with smaller size. The stabilization effect was attributed to the dissolved negative complex that absorbed on the foam film to increase the repulsion between foams as well as to reduce the surface tension of the fresh mixture. The substitution of GGBS by FA generally resulted in reduced dry density and compressive strength, while the extent varied with the addition of stabilizers, and thus the optimal amount of FA depended on the selection of stabilisers. Overall, our study highlighted the potential of using industrial waste materials for producing sustainable light weight concrete with satisfactory dry density and compressive strength.