Fly Ash Aggregate Research Articles

A Brief Study on the Strength Properties of Modified Concrete using Light Expandable Clay Aggregate, Sintered Fly-Ash Aggregate and Tetra Blended Cement along with Pozzolanic & Nano Materials

A Brief Study on the Strength Properties of Modified Concrete using Light Expandable Clay Aggregate, Sintered Fly-Ash Aggregate and Tetra Blended Cement along with Pozzolanic & Nano Materials

Development, engineering properties and potential applications of unfired earth bricks reinforced by coal fly ash, lime and wood aggregates

The current study developed and evaluated the engineering properties of improved low-cost UEBs reinforced with various lime (L)-coal fly ash (F)-wood aggregate (W) mix ratios. The objectives were; (1) to determine the effects of lime-coal fly ash-wood aggregate mixtures on mechanical strength and water resistance properties of UEBs; and (2) to determine the comparative cost of the improved UEBs to that of the control (10% cement). Four UEBs with various lime (L)-coal fly ash (F)-wood aggregates (W) mix ratios (L4%-F16%-W1.5%; L4%-F16%-W3%; L8%-F12%-W3%; L10%-F10%-W1.5%) were fabricated and their engineering properties compared to those of unstabilised (negative control) and 10% cement stabilized (positive control) unfired earth bricks. Dry compressive strength (DCS) of UEBs stabilized by L10%-F10%-W1.5% (8.3 MPa) was significantly higher (p < 0.001) than that of 10% cement stabilized unfired bricks (7 MPa). DCS and dry density of the four UEBs conformed to the British Standards for low-density clay masonry units. DCS increased with lime-fly ash ratio according to a power function (y=−5.41x2+11.18x+2.22; r2 =0.95, p = 0.018), attaining a maximum of 8.3 MPa at a ratio of 1: 1. However, UEBs had low wet strength, but incorporation of 4% cement significantly increased (p < 0.001) the wet compressive strength of UEBs to 0.94 MPa. UEBs stabilized by 10% lime, 10% coal ash, 1.5% wood aggregates and 4% cement (L10%-F10%-W1.5%-C4%) had water absorption (15.8%) similar to that of 10% cement stabilized UEBs. Moreover, unfired earth bricks reinforced by L10%-F10%-W1.5%-C4% conformed to British Standards engineering specifications for low-density clay masonry units, while the cost was 50% lower than that of cement stabilized bricks, demonstrating the low-cost of the UEBs. In summary, the results demonstrate that improved low-cost UEBs can be developed by incorporating lime, coal fly ash and wood aggregates, but a little cement (4%) may be required to increase the wet compressive strength. Potential applications of the UEBs include, (1) internal partitioning; (2) construction of low-cost housing for low-income households in developing countries, and (3) the provision of temporary or short-term low-cost shelter for displaced persons in humanitarian emergencies.

Determination of optimized geopolymerization factors on the properties of pelletized fly ash aggregates

This research investigates the effect of geopolymerization factors on the pelletization in the production of artificial fly ash aggregates. The proportion of pelletized fly ash aggregate mixes was designed through Taguchi’s L9 orthogonal array. The properties of the aggregates produced from the optimal mixes were characterized according to the standard specifications. The effect of geopolymerization factors such as Na2O content, water content, and curing regime on the properties of the pelletized fly ash geopolymer aggregates was determined through response indices at the age of 14, 28 and 56 days. In addition, Grey relation based analysis was performed to identify the most critical parameter for optimization among three geopolymerization factors selected in this investigation, for the production of pelletized fly ash geopolymer aggregates. It is observed from the response indices and Grey relation results that the impact value of the aggregates and crushing strength of individual pellets is governed by heat curing and high water content at the age of 14 and 28 days. However, at the age of 56 days these response indices are significantly governed by the solution curing and high water content. It was also noted that the minimum Na2O content of 3.5–4.5% is adequate for the production of pelletized fly ash aggregates.

Micro-structural behavior of interfacial transition zone of the porous sintered fly ash aggregate

The interfacial transition zone (ITZ) has a significant influence on the hardened concrete behavior. The behavior of ITZ is not well established in the case of sintered fly ash aggregate (SFA) concrete compared to normal aggregate concrete. The present study emphasizes to quantify the characteristics of ITZ of the SFA concrete. To understand the influence of water-cement ratio on the ITZ behavior, various water-cement ratios ranging from 0.25 to 0.75 were employed and the ITZ characteristics were assessed both at 28 and 90 days through various experimental methods such as microhardness test, SEM-EDX and impedance spectroscopy. Also, a comparison is made with the ITZ of the normal granite aggregate concrete. The results indicate that the ITZ formed in the SFA aggregate concrete is denser than the normal aggregate concrete.

Environmental impact and potential use of coal fly ash and sub-economical quarry fine aggregates in concrete

The Israeli quarry industry produces 57 Mt of raw material and ∼4–6Mt of associated sub-economical by-products annually. These sub-economical quarry fines are not used because production and transportation costs considerably exceed their retail value. Therefore these by-products, are stored in large piles of fine grain size particles, create environmental risks to their surrondings.This paper evaluates the possibility of mixing the sub-economical quarry by-products of two Israeli quarries with sub-economical Class F coal fly ash (<20wt.% CaO) to form an economical aggregate sand substitute to be used as a concrete filler product.To study the feasibility of the aggregate as partial substitute to sand in concrete several analyses, including leaching experiements (EN12457-2), analytical techinques (SEM-EDX, ICP-MS, ICP-AES, and XRD), as well as an analysis of the mechanical and chemical properties of the concrete aggregate (strength, workability, and penetration) were performed. Scrubbing quarry waste with coal fly ash was found to be very effective for reducing the leaching rate of potentially harmful trace elements. In addition, adding fly ash with quarry fines as partial substitute to sand enhanced the performance of the concrete mixture and the properties of the fresh and harden concrete.

THE INFLUENCE OF COMPONENT MATERIALS TYPES AND APLICATION ON THE CHLORIDE ION CONTENT IN SELF-COMPACTING CONCRETE

&amp;lt;jats:p&amp;gt;Considering that one of the most common causes of reinforcement corrosion, and consequently degradation of concrete structures, are chloride ions, it is of utmost importance to know their concentration in concrete. This paper presents the limitations of the chloride ions content in concrete and classes according to European regulations, and the experimental research on the magnitude of the influence of applied component materials on the chloride content in various types of self-compacting concrete.The research presented that the dominant influence in respect of the increase of the chloride ions content in concrete, is of cement and then of a recycled concrete aggregate. The application of additions - limestone filler and fly ash and river aggregate results in the reduction of the chloride concentration in the concrete.Through factorial analysis, modeling of the functional dependence of chloride content and application of different types of component materials was performed.&amp;lt;/jats:p&amp;gt;

Porosimetric, Thermal and Strength Tests of Aerated and Nonaerated Concretes

The paper presents the results of porosimetry tests of lightweight concretes, obtained with three research methods. Impact of different porosity structures on the basic thermal and strength properties was also evaluated. Tests were performed, using the pressure gauge method on fresh concrete mixes, as well as using the mercury porosimetry test and optic RapidAir method on specimens prepared from mature composites. The study was conducted on lightweight concretes, based on expanded clay aggregate and fly ash aggregate, in two variants: with non-aerated and aerated cement matrix. In addition, two reference concretes, based on normal aggregate, were prepared, also in two variants of matrix aeration. Changes in thermal conductivity λ and volumetric specific heat cv throughout the first three months of curing of the concretes were examined. Additionally, tests for compressive strength on cubic samples were performed during the first three months of curing. It was found that the pressure gauge method, performed on a fresh mix, gave lowered values of porosity, compared to the other methods. The mercury porosity tests showed high sensitivity in evaluation of pores smaller than 30μm. Unfortunately, this technique is not suitable for analysing pores greater than 300μm. On the other hand, the optical method proves good in evaluation of large pores, greater than 300μm. The paper also presents results of correlation of individual methods of porosity testing. A consolidated graph of the pore structure, derived from both mercury and optical methods, was presented, too. For the all of six tested concretes, differential graphs of porosity, prepared with both methods, show a very broad convergence. The thermal test results indicate usefulness of aeration of the cement matrix of the composites based on lightweight aggregates for the further reduction of the thermal conductivity coefficient λ of the materials. The lowest values of the λ coefficient were obtained for the aerated concretes based of fly ash aggregate. A diminishing influence of aeration on the volumetric heat capacity cv is clearly seen. Simultaneous aeration of the matrix and use of lightweight aggregates brought about also a significant decrease in the average compressive strength fcm of the tested composites.

Phase characterizations, physical properties and strength of environment-friendly cold-bonded fly ash lightweight aggregates

Natural aggregates are non-renewable resources used in excess of 40,000 Mt annually to produce concrete. Artificial aggregates from industrial by-products can be produced as environmentally friendly alternatives. The cold bonding method to produce aggregates uses much less energy compared to the sintering method. This paper reports the results of an experimental investigation on phase characterizations, physical properties and strength of environment-friendly cold-bonded fly ash lightweight aggregates. High calcium fly ash was used as the lightweight material, whereas Portland cement or calcium hydroxide was added as the binder with a small amount in the range of 5–15% by weight to produce lightweight aggregates. Increased density and enhanced crushing strength with low water absorption were found in the fly ash aggregates with the addition of Portland cement or calcium hydroxide. This is due to the occurrence of both hydration and pozzolanic reaction when compared with the fly ash mix. Furthermore, the thermogravimetry results indicate that calcium silicate hydrate, calcium hydroxide, and calcium carbonate phases were observed in all the mixes, while ettringite was also present in fly ash lightweight aggregates incorporated with Portland cement mixes. In this research study, the optimum content of Portland cement and calcium hydroxide were observed to be 10% and 5% by weight respectively. The highest crushing strength was obtained from fly ash lightweight aggregates incorporated with Portland cement at 10% by weight.

Study on Impact Strength of Fly Ash Aggregate Concrete

Study on Impact Strength of Fly Ash Aggregate Concrete

Physicochemical Properties of Individual Airborne Particles in Beijing during Pollution Periods

ABSTRACT Particulate pollution is a serious environmental problem in China and has received much attention from the public. Airborne particles were collected during haze days in Beijing from June 2013 to May 2014. The morphology and elemental composition were investigated with transmission electron microscopy coupled with energy dispersive X-ray spectrometry (TEM-EDX). Six types of individual particles were identified, including sulfate particles (35.1%), mineral particles (26.0%), metal particles (13.5%), fly ash (13.2%), organic particles (5.9%), and soot aggregates (5.7%). Non-carbonaceous particles are mainly “S-rich”, ranging from 37.4% in spring to 56.7% in summer, with certain amount of “Si-rich”, “Ca-rich”, “Fe-rich”, and “K-rich” particles. The relative number percentage of sulfate particles shows a positive correlation with relative humidity (RH), suggesting that high RH might accelerate the sulfation of individual particles. Based on air mass backward trajectories, the high pollution in Beijing might be influenced by local emissions and air masses from adjacent areas south of Beijing. Air masses from Inner Mongolia carry higher concentrations of mineral particles and alleviate the abundance of “S-rich” and other particles.

Possibilities of Lightweight High Strength Concrete Production from Sintered Fly Ash Aggregate

Heat power plants based on coal combustion are produced fly ash as a by-product. Fly ash is not only a by-product. It is due to its pozzolanic activity very useable as a fine additive to concrete in the building industry. It has not only environmental aspect, but also an economic. Potential of use of fly ash in cement concrete technology is only as an additive. But there is a technology of building material production, which use up to 100% of fly ash in the “mixture”. It is sintered artificial aggregate. It can be used for some filter layers, for lightweight flat roof, ceiling or for lightweight concrete composite. There can be made different strength classes of the concrete. It is possible also produce high-strength lightweight concrete reaching strength up to 55 MPa.The paper is about possibilities of different types of fly ash for artificial sintered aggregate to achieve the parameters of lightweight high strength concrete. An interesting aspect of evaluating the quality of the composite is also synergistic interaction of aggregate joined to a cement paste.

A Study on Mechanical and Durability Properties of Concrete with Partial Replacement of Cement with Fly Ash and Fine Aggregate with Waste Glass

A Study on Mechanical and Durability Properties of Concrete with Partial Replacement of Cement with Fly Ash and Fine Aggregate with Waste Glass

Thermal and strength properties of lightweight concretes with the addition of aerogel particles

The aim of this work was to examine the influence of the addition of aerogel particles on the properties of cement composites manufactured using fly ash aggregate. The composites were tested at three different concentrations of water saturation of the coarse aggregate. Moreover, two methods of aerogel particle application were used – plasticising the mix with superplasticiser and aerating with an air-entraining admixture. An assessment of the thermal properties was made during the first 28 d of curing of the composites and compressive strength tests were conducted after 7 and 28 d. For pore structure characterisation, mercury pore structure analysis was carried out on the pure aerogel, the cement composites and the composites with the addition of granulate. The data obtained indicate that adding aerogel particles to concrete composites is an appropriate method of improving thermal parameters: thermal conductivity coefficients were two times smaller compared with control samples without aerogel and, simultaneously, the volumetric specific heat was comparable to that of the control samples. However, the addition of aerogel resulted in a reduction in compressive strength to approximately only 30% of that of the control samples.

Structure formation of aerated concrete containing waste coal combustion products generated in the thermal vortex power units

The results of fly ash research, generated in the process of waste coal combustion in the thermal vortex power units and used as an aggregate in aerated concrete, are provided. It is established that fly ash can be used in the production of cement or concrete with low loss on ignition (LOI). The permitted value of LOI in fly ash, affecting the structure formation and operational properties of aerated concrete, are defined. During non-autoclaved hardening of aerated concrete with fly ash aggregate and LOI not higher than 2%, the formation of acicular crystals of ettringite, reinforcing interporous partitions, takes place.

Mechanical properties of cold bonded quarry dust aggregate concrete subjected to elevated temperature

The use of waste materials such as fly ash and quarry dust in the building construction process is explored in this paper. The coarse aggregate prepared using quarry dust and fly ash by cold bonding process is used for the making of concrete. The mechanical properties of the concrete, namely, compressive strength, splitting tensile strength and modulus of elasticity are determined. The variables considered are aggregate ratio, water binder ratio, temperature ratio and type of aggregate. For cold bonded aggregate concrete, it is found that the strength of the concrete is completely lost when exposed to certain limiting temperature. The limiting temperature is different for fly ash aggregate and quarry dust aggregate concrete. The limiting temperature of fly ash aggregate concrete is 300°C and that of quarry dust aggregate concrete is 400°C. This is due to the variation in the agglomeration process of fly ash and quarry dust in cold bonding process. The scanning electron microgram of spit aggregate on the cracked face of the specimen shows the evidences of formation and expansion of cavities due to the exposure to high temperature. The multiple regression models for the prediction of mechanical properties are developed. The present study gives an insight to the end users regarding the scope of the utilization of cold bonded aggregates in construction exposed to temperature.

Combined Effects of Non-Conforming Fly Ash and Recycled Masonry Aggregates on Mortar Properties.

This work evaluates the effects of using non-conforming fly ash (Nc-FA) generated in a thermoelectric power plant as filler material for mortars made with natural sand (NA) and recycled sand from masonry waste (FRMA). The incorporation of powdered recycled masonry filler (R-MF) is also tested as an alternative to siliceous filler (Si-F). Three families of mortars were designed to study: the effect of replacing Si-F with Nc-FA on mortars made with NA; the effect of replacing Si-F with Nc-FA on mortars made with 50% of NA and 50% of FRMA; and the effect of replacing Si-F with R-MF on mortars made with NA and FRMA. Replacing Si-F with Nc-FA is a viable alternative that increases the mechanical strength, the workability and durability properties and decreases the shrinkage. The use of FRMA and Nc-FA improved the mechanical strength of mortars, and it slightly increased the shrinkage. The replacement of Si-F with R-MF on mortars made with FRMA is not a good alternative, because it has a negative impact on all of the properties tested. This work can help both to reduce cement and natural resources’ consumption and to increase the recycling rate of Nc-FA and FRMA.

Gamma-ray shielding effectiveness of novel light-weight clay-flyash bricks

The radiation shielding parameters of lightweight clay-flyash bricks produced with different flyash aggregate compositions have been investigated by using 241Am (59.4keV), 137Cs (661.6keV), and 60Co (1173.2keV and 1332.5keV) radioactive sources. It was observed that the different percentages of flyash in clay lead to significant variations in these parameters. The elemental compositions of the clay-flyash bricks were analyzed using energy dispersive X-ray fluorescence spectrometry (EDXRF). The obtained results were compared to those pertaining to concrete in order to see the effect of flyash content on the radiation shielding properties. The radiation protection efficiency of the tested clay-flyash bricks demonstrated that multilayer exterior walls built from these bricks could effectively attenuate moderate-energy gamma rays. Bricks using residual flyash could be preferentially used for buildings to address the issues of radiation shielding, cost-effective radioactive waste management and disposal of flyash in a useful manner.

Design and preparation of high elastic modulus self-compacting concrete for pre-stressed mass concrete structures

Requirements of self-compacting concrete (SCC) applied in pre-stressed mass concrete structures include high fluidity, high elastic modulus, low adiabatic temperature rise and low drying shrinkage, which cannot be satisfied by ordinary SCC. In this study, in order to solve the problem, a few principles of SCC design were proposed and the effects of binder amount, fly ash (FA) substitution, aggregate content and gradation on the workability, temperature rise, drying shrinkage and elastic modulus of SCC were investigated. The results and analysis indicate that the primary factor influencing the fluidity was paste content, and the main methods improving the elastic modulusof SCC were a lower sand ratio and an optimized coarse aggregate gradation. Lower adiabatic temperature rise and drying shrinkage were beneficial for decreasing the cement content. Further, based on the optimization of mixture, a C50 grade SCC (with binder amount of only 480 kg/ m3, fly ash substitution of 40%, sand ratio of 51% and proper coarse aggregate gradation (V5-10 mm: V10-16 mm: V16-20 mm= 30%: 30%:40%)) with superior workability was successfully prepared. The temperature rise and drying shrinkage of the prepared SCC were significantly reduced, and the elastic modulus reached 37.6 GPa at 28 d.

Performance enhancement of green concrete

Several factors, such as energy-saving methodologies and techniques and improved use of materials, need to be considered for the development of sustainable construction materials. In the present work, the feasibility of using industrial inorganic polymeric residual wastes as a total (100%) replacement for traditionally used normal concrete materials was examined in the preparation of geopolymer concrete (GPC). In this study’s GPC, the cement was replaced totally by fly ash (class F) and ground granular blast furnace slag (GGBFS), the fine aggregates were replaced totally by bottom ash, the coarse aggregates were replaced totally by water-cured fly ash aggregates (WCFAs), which were prepared by using class C fly ash by adopting the pelletisation technique. The GPC mixes were cast with WCFAs at 0, 10, 20 and 30% replacement of fly ash (class F) by GGBFS with different molar ratios of sodium hydroxide (NaOH) solutions (8, 10, 12 M). The concrete was cured at ambient temperature only to minimise the water during water curing. The physical and mechanical properties of the GPC were studied by using the combination of all the mentioned materials. It was observed that the GPC mixes at 30% GGBFS with 12 M sodium hydroxide attained a maximum compressive strength of 38·94 MPa.

Properties of Pervious Concrete Aiming for LEED Green Building Rating System Credits

Pervious concrete is a special type of concrete with high porosity. The use of pervious concrete may achieve many potential LEED green building rating system credits. The objective of this paper is to investigate the appropriate mix proportion which provides the high LEED points and also the good mechanical properties. Nine mix proportions based on possible LEED points were examined. The replacement of cement by fly ash (20% - 60%) and coarse aggregate by recycled aggregate (20% - 100%) were used. Properties of pervious concrete relating to LEED credits and design values such as permeability, void content, compressive strength and splitting tensile strength were evaluated. It was found that the proposed pervious concrete can achieve the stormwater design-quantity control, recycled content and recycled materials credits. According to the results, the mix proportions which cement was replaced by 40% and 60% of fly ash archived the highest LEED credit points and also provided the sufficient mechanical properties. Therefore, these mix proportions are recommended for green construction.