Fly Ash Aggregate Research Articles

Inspection of Thermo-Mechanical Behavior on Sintered Fly Ash Aggregate in Pavement Quality Concrete

Conventional concrete pavement is more efficient towards mechanical load but combing with environmental loads compromises serviceability. This paper mainly focuses on utilizing sintered fly ash (SFA) aggregate to partially replace coarse aggregate in pavement quality concrete. Incorporating SFA aggregate in concrete pavement enhances the thermal behavior of rigid pavement due to higher voids and lower thermal conductivity. Coarse aggregate was partially replaced with SFA aggregate at an interval of 10 % till 40% by volumetric replacement. Pavement quality concrete (PQC) was designed as per Indian standards with a fixed water-cement ratio of 0.36 to achieve a minimum of 40 N/mm2 compressive strength. Compressive, split tensile and flexural strengths were inspected as mechanical behavior and thermal conductivity was examine as thermal behavior of different SFA mixed PQC. It has been observed that there is a slight decrement in mechanical strength by incorporating SFA in PQC but the thermal property of PQC was improved. Overall, it can be concluded that incorporating SFA at a certain level enhances the combined thermo-mechanical properties of PQC.

Assessment of Properties of Structural Lightweight Concrete with Sintered Fly Ash Aggregate in Terms of Its Suitability for Use in Prestressed Members.

The main aim of the paper was to assess whether the lightweight concrete with a new type of sintered fly ash aggregate can be used as a structural material for post-tensioned elements subject to high effort. This purpose was achieved by comparison of the properties of lightweight aggregate concrete with Certyd aggregate (LWAC) and normal-weight concrete with dolomite aggregate (NWAC) of similar strength in terms of their suitability for use in prestressed members. Special emphasis was placed on long-term, relatively rarely performed tests of rheological properties such as shrinkage and creep. The research was conducted on standard specimens as well as on plain and post-tensioned beams of bigger scale, which could reflect better the behavior of the materials in a destined type of structural members. The carried out tests showed that, despite the expected lower density and modulus of elasticity, LWAC revealed comparable tensile strength and lower shrinkage and creep in the whole time of observations (ca 1.5 years) in comparison to NWAC. Moreover, the total loss of prestressing force for beams made of LWAC was slightly lower than for NWAC. Estimations of tensile strength and modulus of elasticity values according to the standard Eurocode EN-1992-1-1 for both concrete types turned out to be satisfactory. However, the rheological properties of the tested lightweight concrete seemed to be considerably overestimated.

Flexural behaviour of fly ash incorporated ferrochrome slag aggregate reinforced concrete beam

The structural behaviour of fly ash integrated ferrochrome slag aggregate concrete (FCSAC) is not widely understood owing to lack of research, although some studies have focused on its mechanical and environmental performance. The real-world use of FCSAC relies on its large-scale structural tests. This research investigates the flexural response of reinforced concrete beams fabricated with fly ash and ferrochrome slag (FCS) aggregate. A total of sixteen full-scale beams were built and tested. The beams were cast using four different concrete compositions: natural aggregate concrete (NAC) without any fly ash and FCS as the reference; FCSAC comprising 100% FCS as coarse aggregate and fly ash as partial substitution of cement at different percentages: 0%, 20% and 30%. The beams were fabricated with two different longitudinal reinforcement ratios of 0.69% and 1.86%. An eco-efficient mix proportioning method based on Particle packing optimization technique (PPOT) was adopted aiming to develop sustainable concrete. The effect of alternate resources (FCS and fly ash) and reinforcement ratios on the flexural response, cracking, ultimate load, failure pattern, ductility and toughness were examined. The experimental outcomes were compared to the predictions derived from the existing code provisions. Results revealed that the flexural performance of the FCSAC with fly ash beams was superior to that of NAC beam, despite having a lower flexural capacity than the FCSAC without fly ash beams. Moreover, the comparative study demonstrated that the fly ash-based FCSAC beams may be designed in accordance with the same guidelines as conventional concrete.

Performance Evaluation of Artificial Angular Fly Ash Aggregate

This experimental study describes the development of the lightweight angular fly ash aggregate (FAA) and consequent comparison of properties of FAA with natural aggregate (gravel). The manufacturing process of these FAA involves blending of fly ash with cement and alkali activators at various proportioning of cement to fly ash and placing the mix in the mould. This is followed by curing of the cubes for 7 days after letting it to dry for 24hrs and crushing them to obtain the aggregate of different sizes. After having the fly ash aggregate, the test are carried out in fresh state and hardened state of the fly ash aggregate concrete and the conventional concrete. Results are compared to see the efficiency level of flyash aggregate concrete.The properties of both angular fly ash aggregates like Specific gravity, water absorption, Impact value, and Abrasion value are compared with the properties of the conventional aggregates (gravel). This study concludes that FAA with proper mix proportioning can be used as a substitute for conventional aggregates for sustainable construction.

A state-of-the-art review - mechanical properties of light weight concrete by utilizing sintered fly ash aggregate

Utilization of concrete increases rapidly which led to depletion of natural resources. In order to resolve problem on scarcity of coarse aggregate, various artificial aggregate material can be partially replaced in coarse aggregate like sintered fly ash aggregate, palm kernel shell or coconut shell can reduce disposal problems. Harmful effect of concrete can be reduced by iterate structural efficiency and its performance characteristics of concrete. Present findings focuses on feasibility of making structural light weight concrete using sintered fly ash aggregate and researches on use of sintered fly ash aggregate and other material as partial replacement of coarse aggregate for producing light weight concrete. According to a literature review, these aggregates are 16–46% lighter and more capable of absorbing water than aggregates of similar weight. The concrete produced using sintered fly ash demonstrated strong mechanical and structural qualities. Sintered fly ash aggregate concrete has compressive strength between 22 and 43 MPa and densities between 1600 and 2000 kg/m3. Concrete made using fly ash aggregate appears to function well in structural applications. Concrete using sintered fly ash aggregate has been considered as a possible structural concrete material.

Experimental and Numerical Investigations of Laced Built-Up Lightweight Concrete Encased Columns Subjected to Cyclic Axial Load

The steel-concrete composite column comprises a steel core and surrounding concrete. The purpose of the system is to provide analysis and design techniques for a newly invented class of laced steel-concrete composite short columns for cyclic axial loads. To minimize the increasing density issues associated with nominal strength concrete and in consideration of the depletion of natural resources required to produce concrete, factory-obtained lightweight sintered fly ash aggregates with and without basalt fiber are employed. The normal-weight concrete containing basalt fiber is shown to be more ductile than any other column. The axial deformation of columns LNA and LSA at failure was found to be 3.5 mm, whereas columns LNAF and LSAF reached an axial shortening of 4.5 mm at failure. The column LSAF was found to have 5.3% more energy absorption than the LSA and 11.5% less than the column LNAF. It was observed that the rigidity of these fabricated components had been enhanced. It was found that the section configuration with a lacing system had improved confinement effects and ductility. Comparing the finite element analysis to the experimental data revealed a strong connection with numerical modeling, with a variance of around 8.77%.

Assessment of the Combined Effect of Silica Fume, Fly Ash, and Steel Slag on the Mechanical Behavior of Concrete

Every ton of cement produced emits half a ton of carbon dioxide, so there is an immediate need to limit cement use. Cementitious materials such as fly ash, silica fume, and steel slag can be substituted for cement in making concrete more rigid and stronger. This research work has been done to analyze the change in compressive strength in concrete, reducing the use of cement and coarse aggregate, in the case of varying percentages of cement replacement circumstances. To get this job done, there’s been conducted a variety of laboratory tests changing the partial cement replacement proportions with silica fume and fly ash and partial aggregate replacement with steel slag in the concrete mix. The test result showed that 15% silica fume, 10% fly ash, and 30% steel slag replacing proportion withstand more compressive load than the normal cement concrete mixture. The SEM test also supports the compressive strength test result by showing the internal bonding between the materials in the replaced binder-aggregate specimens. On the other hand, the flexural strength test came out with the best proportion of 15% cement replacement with fly ash and silica fume along with 10% coarse aggregate replacement with steel slag. The XRD patterns of the materials used also enumerate the standardization and testing procedures. The usage of sustainable cementitious materials like fly ash, silica fume, and steel slag incorporates the motivation behind reducing the industrial byproducts/wastes generated in such an amount that hampers our mother nature. The overall representation of this research will emancipate the initiatives taken toward greener and more sustainable construction.

Triaxial compression failure criterion and constitutive relation of concrete containing multiple solid wastes

This study analyzed the mechanical properties and failure criterion of full-solid waste concrete (SCT) made with slag, fly ash, carbide slag, soda residue, and iron tailings aggregate. SCT showed a higher strength growth rate (25.5–57.7%) compared to natural sand and gravel as aggregate (SCN) (20.7–47.5%), but lower than cement + natural sand and gravel (PCN) (32.0–86.1%), due to the latter's susceptibility to microcracks. The study proposed a parabolic pressure meridian failure criterion equation and an improved power function formulation of the Mohr-Coulomb failure criterion for SCT. The findings suggest that SCT can be used in engineering applications.

Mechanical and Microstructure Properties of Plain and Blended Cement Structural Lightweight Aggregate Concrete Using Sintered Fly Ash Aggregates

Infrastructure and industry have grown dramatically as a result of globalization and urbanization. However, there are certain challenges, such as meeting infrastructural needs that require a large amount of extraction of natural aggregates and disposal of waste generated as a result of industrialization. Both of these challenges have an adverse impact on the environment. Deforestation, erosion, contamination of nearby streams, and increase in noise, dust, and emissions are all consequences of aggregate extraction. The industrial waste can contaminate groundwater, lakes, streams, rivers and coastal waterways and harm the land and neighboring water bodies. Hence these challenges must be addressed as a priority for environmental sustainability. The current study developed structural lightweight aggregate concrete (SLWAC) using sintered fly ash aggregate (SFA). The investigation was done with the use of different binders such as Portland Pozzolana Cement (PPC), Ordinary Portland Cement (OPC), and Micro Fibre Cement (MFC). The present study explores the suitable binder to produce SLWAC at different water-cement ratios of 0.4, a0.44, and 0.48. The performance evaluation of SLWAC was investigated by mechanical behavior like compressive strength, split tensile, flexural strength, and impact test. Microstructure analysis is also included in this study to validate the mechanical experiment results. SLWAC made from OPC shows more mechanical strength than PPC and MFC, due to faster hydration and early strength gain. SLWAC made from microfiber cement, has more strength as compared to PPC. This could be due to fibers in MFC, acting as a reinforcing agent, which reduces micro cracks. The microstructure of SLWAC shows that the wall effect does not exist in SLWAC compared to normal aggregate concrete. It has a uniform and continuous microstructure of hydration products and partially penetrates the SFA. It could be associated with the superior interfacial transition zone having a lower w/c ratio because of the higher absorption of SFA. The findings show that all developed SLWAC can be used in structural members like beams, columns, and slabs.

The effect of fly ash aggregates on the self-healing capacity of bacterial concrete

In concrete structures, crack development is a typical phenomenon, it reduces durability and strength. To solve this issue, an autonomous self-healing mechanism was introduced. This mechanism aids in the repair of cracks by generating the calcium carbonate crystals that seal the concrete's pores and micro-cracks. Bacillus subtilis was used in the concrete mix as an additive. In this work, the coarse aggregate was replaced partially by Fly ash aggregates in different proportions. Total eleven concrete mixes are cast and tested for strength properties, in that seven without bacteria and four with bacteria. The crack healing capacity of the concrete specimens was observed at regular intervals by using Elcometer and Digimizer software. The relation between initial crack width and percentage of crack healing was observed. The concrete mix with 30% of fly ash aggregate replacement showed high increment strength in strength of 61.37% and complete healing of maximum cracks width 0.25 mm.

Application and validation of internally cured concrete strength characteristics by machine learning

Water is a precious resource, and the demand for potable water is high in many regions globally. Potable water is being used in the construction of buildings, and a substantial amount of water is required for curing concrete elements, which can be saved with modern construction practices like internal or self-curing concrete. The properties of concrete are usually identified through physical testing. Experiments become time-consuming, laborious and costly if multiple parameters in small proportions are to be modified and the results are to be predicted. Predicting nominal mix proportions becomes difficult; alternatively, utilising computational and predicting any specific or multiple outputs by analysing multiple input parameters with randomised data is feasible through machine learning. Considering this, an attempt is made to develop self-curing concrete of M30 grade utilising fractional replacement of 30% coarse aggregates with fly-ash aggregate as an internal curing agent. Different algorithms those that are processed in machine learning deal with prediction and validation of concrete characteristic strength parameters; 1) decision tree regression; 2) random forest regression, and 3) multiple layer perception regression analysis. In this study, the comparison found that the utmost successful machine learning strategy for prediction of concrete strength properties is the decision tree regressor method, with the least error fitting the regression curve.

Strength and durability of concrete by partial replacement of cement by fly ash and fine aggregates by granite dust

The building sector is one of the most dynamic and potentially important contributors to national income. It's possible that concrete, as a composite building material, plays a pivotal role in the market. Common concrete calls for the use of natural sand, often known as stream sand. Since river sand is becoming more scarce and prohibitively costly, we have had to go elsewhere for this material. With the ever-increasing need of the construction industries for materials that fulfil their functional, strength, and durability needs, a wide range of novel materials has been produced in the area of concrete technology in recent years.In this investigation, fly ash was substituted for the fine combination of Quarry Dust and cement. Partially substituting Fly Ash for Cement at 0%, 5%, 10%, 15%, 20%, and 25%. The increased moisture electrical resistance and resulting toughness that results from the micro-filling effect gives concretes a leg up on the competition. Compressive and flexural strengths of M40-grade concrete are the primary focus of the experiments. Examine the mechanical and sturdiness characteristics at various ages, including 7 days, 28 days, 56 days, and 90 days. Durability and tensile strength tests, including exposure to acid and chloride for 28 days. The results publicized that by taking 0% to 25% of Fly ash to the weight of cement that specimen when compared with conventional concrete the compressive strength is increased 32.63% by replacement of cement with 10% of Fly Ash for 28 days. Comparing to normal concrete the compressive strength is increased 29.25% with 10% of Fly ash for 56 days. Comparing to conventional concrete the compressive strength is increased 16.93% with 10% of Fly ash for 90 days. SPT values enhanced by 16.67% with 10% of Fly ash at 28 days of curing.

Experimental and numerical studies on flexural behaviour of lightweight and sustainable precast fibre reinforced hollow core slabs

This study reports experimental and numerical studies on the flexural behaviour of sustainable fibre reinforced lightweight hollow core slabs (FR-LWHCS). An innovative and sustainable LWHCS is proposed for structural applications using a lightweight concrete mix of 1800 kg/m3 density, previously developed by authors. Full-scale precast LWHCS specimens are cast and tested under flexure using a four-point loading configuration. A high shear span to depth (a/d) ratio of 10 is chosen to have flexure dominant behavior. FR-LWHCS is made using sintered fly ash aggregate (SFA) as coarse aggregate and monofilament macro synthetic fibres of different volumetric fibre dosages (0.4 % and 0.6 %). A small dosage of micro synthetic fibres of 0.02 % by volume is also added to arrest shrinkage cracks. Two control slabs, one constructed with lightweight concrete and the other with conventional normal density concrete, are tested. The digital image correlation (DIC) technique is used to track the cracks and failure modes. A 3D finite element analysis is performed to supplement the test results. Test results show that FR-LWHCS satisfies all the structural requirements, leading to economy and sustainability. FR-LWHCS with 0.6 % fibre dosage performed better than hollow core slabs made of normal density concrete. Though the addition of fibres did not considerably increase peak load, a minimum dosage of fibre addition is warranted in LWHCS to improve the serviceability performance. Fibre addition significantly improved the strain energy absorption.

Experimental and numerical study on behaviour of fibre reinforced lightweight hollow core slabs under different flexure to shear ratios

The current work explores the behaviour of fibre-reinforced lightweight hollow core slabs (FR-LWHCS) intending to develop sustainable construction solutions. The FR-LWHCS investigated in this work contains sintered fly ash aggregate (SFA) as coarse aggregate. Due to the use of SFA, the behaviour of LWHCS is expected to be different from the hollow core slabs (HCS) constructed using normal density concrete. FR-LWHCS are tested at different shear span to depth (a/d) ratios of 3.5, 7 and 10 to understand the shear and flexure behaviour. Twelve full-scale hollow core slab (HCS) specimens of 3400 mm length, 600 mm width, and 150 mm thickness are tested. FR-LWHCS consists of monofilament macro synthetic fibre dosages of 0.4 %, and 0.6 %, along with fibrillated micro fibre of 0.02 % dosage. The digital image correlation (DIC) technique is adopted to understand the strain profile on the HCS at different levels of loading. The numerical analysis is performed using a commercially available finite element software and is corroborated with experimental findings and parametric studies have been performed. Both LWHCS and normal HCS specimens failed in shear, flexural-shear and flexure modes at a/d ratios of 3.5, 7 and 10, respectively. The addition of fibres increased the peak load by 65 % compared to control LWHCS specimens tested at an a/d ratio of 3.5. The use of fibres increased strain energy absorption and changed the failure to less brittle mode at all a/d ratios. The fibre reinforced specimens have nearly 3.5 times, 2.5 times and 1.3 times the strain energy absorption of the control LWHCS when tested at a/d ratio 3.5, 7 and 10 respectively.

Properties of concrete containing high-calcium fly ash artificial aggregate

The work aims to develop a concrete mixture with cold-bonded fly ash aggregate based on high-calcium fly ash and experimentally study its physical and mechanical properties. The results of experimental studies of concrete with artificial coarse aggregate based on fly ash from Berezovskaya Thermal Power Plant showed compressive strength of 28.92 MPa, flexural strength of 4 MPa, coefficient of linear thermal expansion of 14.5 * 10−6 K−1, modulus of elasticity of 16 *109 Pa, heat of hydration on the 10th day - 340 kJ/kg, shrinkage deformation of −1.8 mm/m. It has been established that heat treatment of fly ash aggregate for 8 hours at a temperature of 80 °C after 7 days of air storage did not positively affect the physical and mechanical properties of concrete. The compressive strength at the age of 28 days and the modulus of elasticity of the specimens with coarse aggregate after heat treatment were lower by 41% than that of the control mixture.

Compressive strength optimization and life cycle assessment of geopolymer concrete using machine learning techniques

Fly ash-based geopolymer concrete is studied in this research work for its compressive strength, life cycle and environmental impact assessment contribution to the construction environment. This is in line with the United Nations’ sustainable development goals SDG9 and SDG11. However, the focus of this research paper is on the sustainability of geopolymer concrete and its overall environmental impact. The metaheuristic machine learning approaches have been deployed to predict the compressive strength (CS) of the GPC based on environmental impact considerations of the concrete constituent materials, which included fly ash, sodium silicate, sodium hydroxide, fine and coarse aggregates. The metaheuristic techniques include the k-Nearest Neighbour (kNN), support vector regression (SVR), and random forest regression (RFR), where all are optimized with the particle swarm (PSO). These metaheuristic techniques have been modified for this research work with new codes to enhance innovation in terms of run time and efficiency. The results of the life cycle assessment (LCA) evaluation of the GPC mixes based on the Ecoinvent 3 available in SimaPro and Eco-indicator 99 and CML 2001 modified in the framework of ReCiPe 2016 recent development show reduced potential of environmental acidification due to increased fly ash (FA) in the GPC mixes compared to previous results. The decisive CS and LCA predictive models, RFR-PSO and SVR-PSO respectively performed optimally above 90% and better than previous models from the literature. Overall, they present an innovative metaheuristic smart technology for the prediction of the GPC infrastructure behavior and performance integrity.

Comparative analysis and performance of light weight concrete with varying water cement ratio using plain and blended cement

Rapid infrastructure growth and industrialization have aided in driving growth, creating job opportunities, and reducing poverty; however, there are some challenges, such as meeting infrastructure needs, large extraction of natural aggregates required to make concrete, and disposal of waste generated by industrialization. Therefore, to promote resilient infrastructure and sustainable industrialization, the present study develops light weight concrete (LWC) from sintered fly ash aggregate (SFA) using plain and blended cement at various water-cement ratios. In the current investigation, binders such as ordinary Portland cement (OPC), Portland Pozzolana Cement (PPC), and Micro fibre cement (MF) were selected to produce LWC at water-cement ratios of 0.40, 0.44, and 0.48. The results show that LWC from OPC gives better results after 28 days, and as the curing days increase, the strength of LWC made from MF and PPC reaches closer to OPC values. LWC made from MF is the least permeable compared to OPC and PPC. Microstructure investigation reveals no distinct interfacial transition zone (ITZ) in LWC, as cement paste seals most of the pores of SFA and creates strong bonds. The findings will aid in the development of LWC with the appropriate binder for specific infrastructure project requirements.

Temperature sensitivity analysis on mechanical properties of phase changing material incorporated rigid pavement

Phase changing materials (PCM) are used to improve thermal performance of rigid pavement. PCM impregnated sintered fly ash aggregate (SFA) were replaced with conventional aggregate to improve the thermal performance of concrete. Rigid pavement needs to be strong and stable at high temperatures for structural reasons. Using PCM in pavement affects the on overall performance of concrete at high temperatures In this study, temperature sensitivity of PCM incorporated concrete were inspected and compared with conventional mixes. Mechanical (compressive, tensile and flexural) strength was inspected and compared to study the effect of PCM incorporated concrete subjected to different temperatures. Arrhenius model taken in accounts to inspect factor of temperature sensitivity related to mechanical strength to estimate temperature dependence of concrete by PCM. Reduction in mechanical strength was observed with increasing the PCM content in concrete. Similarly, reduction in mechanical strength were inspected by increasing temperature of PCM modified concrete. Temperature sensitivity values are increased by increasing the PCM content in concrete pavement. The current research emphasizes the importance of considering temperature sensitivity when incorporating PCM in rigid pavement design.

Use of Lightweight Sintered Fly Ash Aggregates in Concrete at High Temperatures

This study addresses the issue of the resistance to high temperatures of lightweight concrete lightweighted with sintered fly ash aggregate. Lightweight concretes with different amounts of lightweighting and their properties after loading temperatures of 600, 800 and 1000 °C were investigated. In particular, the effect of high temperature on the mechanical properties of the concrete was determined on the test specimens, and the effect on the microstructure was investigated by X-ray diffraction analysis and scanning electron microscopy. It was found that there is an increase in compressive strength between 0 and 21% up to 800 °C, where the increase in strength decreases with increasing degree of lightening. At 1000 °C, the internal structure of the lightweight concrete destabilized, and the compressive strength decreased in the range of 51–65%. After loading at 1000 °C, the scanning electron microscope showed the formation of spherical-shaped neoplasms, which significantly reduced the internal integrity of the cement matrix in the lightweight concrete due to the increase in their volume. It was found that the lightweight concretes with higher lightweighting showed significantly less degradation due to higher temperature.

Comparative study of the efficacy of fly ash and reactive aggregate powders in mitigating alkali-silica reaction

This study investigates the ability of reactive aggregate powders to mitigate alkali-silica reaction (ASR) in comparison with fly ash using the accelerated mortar bar test (AMBT). ASR expansion results confirm that the reactive aggregate powders can mitigate ASR, although fly ash still has better mitigating efficacy. Microstructural characterization post-AMBT shows presence of extensive cracking in the plain OPC mortar, few cracks in the mortar with 25% reactive aggregate powders and negligible cracking in the mortar with 25% fly ash. Elemental analysis shows that the reactive aggregate powders are able to increase the Si/Ca and Al/Si ratio of C–S–H composition similar to fly ash. 25% fly ash replacement however results in much higher Si/Ca and Al/Si ratio which likely explains its better efficacy in mitigation. Thermogravimetric analysis results demonstrate that the reactive aggregate powders are pozzolanic like fly ash and that a reactive aggregate powder with better pozzolanic properties has better efficacy to mitigate ASR. The reactive aggregate powders however unlike fly ash do not contribute to compressive strength development of the mortars.