Conventional Fly Ash Research Articles

Properties of geopolymers from conventional fly ash activated at increased temperature with sodium hydroxide containing glass powder obtained from the recycling of waste glass

This paper presents test results of the physical and mechanical properties of geopolymers based on conventional fly ash activated at increased temperature with sodium hydroxide, containing glass powder obtained from the recycling of waste glass. Tests were performed on mortars of a geopolymer binder containing glass powder of various levels of fineness, at quantities ranging from 5 to 95% of the mass of the conventional fly ash. The properties of the geopolymer binder with and without the content of glass powder were determined on the basis of the heat of hydration. The suitability of the application of glass powder in geopolymers was confirmed by results of testing the following parameters using a scanning electron microscope (SEM) and analysis of micro areas (EDS) in geopolymer materials: particle size distribution, density, porosity, X-ray diffraction (XRD). Testing of the compressive strength of the geopolymer mortars was performed after: 1, 7, 14 and 28 days of curing in air-dry conditions. Results of microstructure tests confirm that the glass powder coming from recycled waste glass in presence of the geopolymer binder undergoes reactions of alkaline activation at increased temperature, the products of which are zeolite minerals and sodium silicate gel. On the basis of test results of physical and mechanical properties of the geopolymers, it was proven that the content of glass powder had a beneficial effect on the utility parameters of the obtained material. The aforementioned research confirms the possibility of using waste glass for the production of geopolymer materials applied in the construction industry.

Experimental studies on flexural behaviour of self compact concrete beam

Self-compacting concrete is a liquid flow for pouring in structures with clogged support without vibration. Self-compacting solid improvement must guarantee a decent harmony among deformability and steadiness. Self-compacting concrete (SCC) is a creative solid that doesn't require vibration for setting and compaction. It can stream under its own weight, totally filling formwork and accomplishing full compaction, even within the sight of clogged fortification. The solidified cement is thick, homogeneous and has indistinguishable building properties and strength from customary vibrated concrete. So to addition to this new technique. I have aimed at creating a more cost effective SCC by partial replacement of aggregates with powdered coconut husk, burned coconut husk, powdered coconut shell and burned coconut shell. Thus increasing strength and also decreasing the cost of production. I had tried differently with coconut husk powder as the filler material instead of conventional fly ash. Because coconut husk is 100% natural and renewable resource, easily available. Moreover it is a non-degradable and also it reduces fungus growth. So considering its characteristics had chosen the coconut husk. Therefore this concrete will be economical than that of the conventional concrete. Our concrete grade is M50 in this I adding the two types of admixtures. Conplast sp430 used as a strengthening agent and Glenium B233 used as viscosity modification agent. Finally our motive is to check out the flexural behavior of self compacting concrete beam of 1 m × 0.23 m × 0.23 m having 2 nos of 8 mm bar in both the compression and in tension zone with 6 mm dia vertical stirrups at 150 mm c/c in single and two point load test.

Comparative investigation of reactivity of different kinds of fly ash in alkaline media

Comparison of the influence of temperature and different alkali activators on the reactivity of two types of fly ash (conventional, fluidized) was presented. The main emphasis was put on fluidized fly ash as potential component of binding mixtures containing low amount of cement. Conventional fly ash was used as a reference. It was found that for these materials the key differences affecting products of activation are: availability of calcium and sulfate ions as well as structure of fly ash grains influencing dissolution of aluminate and silicate species. Fluidized fly ash, contrary to conventional fly ash, undergoes reaction in 0.1 M solutions of hydroxides forming mainly ettringite. In the case of 4 M hydroxides, both fly ashes undergo hydration processes. Conventional fly ash formed mainly amorphous aluminosilicate gel, while fluidized fly ash may create zeolitic products especially in the case of elevated temperature of early hydration. Sulfate and alkali ions can be incorporated into aluminosilicate structure of new formed products; however, this process depends strictly on the type of used hydroxide and its concentration. The presence of Ca(OH)2, carbonates and alkali sulfates was also registered in the case of hydrated fluidized fly ash.

Comparison of Strength Between Conventional Paver Block and Fly Ash Paver Block

Comparison of Strength Between Conventional Paver Block and Fly Ash Paver Block

Effect of alternative walling material on indoor temperature

This paper demonstrates the effect of an alternative walling element on the indoor temperature through a case study of a slum house. Using locally available biobriquette ash (BFA), cellular lightweight (CLW) bricks were developed and compared with conventional fly ash (FA) bricks. Two double-storey representative models (FA bricks and BFA-CLW bricks) were constructed in Trnsys software to analyse the indoor temperature. The estimated peak temperature reductions for the ground and first floors of the BFA-CLW model are 4·2 and 1·9%, respectively. Reductions in the area under the curve of the BFA-CLW model are 2·6 and 1% (year) and 20 and 9% (summer) for the ground and first floors compared to those of the FA model. The cost comparison for BFA-CLW brickwork showed 28% reduction compared to that for FA brickwork, while the embodied energy of the brickwork is equivalent. The application of the proposed bricks shows advantages over FA brick and, thus, can be adopted for sustainable construction practices.

Ternary binder made of CFBC fly ash, conventional fly ash, and calcium hydroxide: Phase and strength evolution

Coal combustion products present a source of aluminosilicate materials for further utilization. The ternary binder studied here is such an example, consisting of circulating fluidized bed combustion (CFBC) fly ash, conventional fly ash and Ca(OH)2 activator. The paste yields a compressive strength of 32 MPa after 28 days of standard sealed curing. Volumetric evolution of crystalline and amorphous phases during hydration is quantified using XRD analysis, differential thermal gravimetry, porosimetry and electron microscopy. A micromechanical model is applied to interpret the evolution of compressive strength due to the growing proportions of C-S-H and ettringite in the system. This opens the way for further optimization and utilization of this ternary binder.

Cement-fly ash mortars durability, with fly ash from fluidized bed boilers and conventional combustion, exposed to aggressive environment influence

The study shows results of research on the aggressive environment impact (1, 3 and 5% HCl solution) on durability of cement mortars with fraction from 30 to 45% by mass of fly ashes from the fluidized bed combustion (FBC fly ash) and conventional fly ashes used separately and in the form of a mixture. The impact of aggressive environments on durability of cement and ash mortars was tested for aperiod of 365 days, by testing the compressive strength, linear changes, mass loss and porosity. It was demonstrated that mortars with the content of FBC fly ashes, after 365 days of tests showed the higher resistance to aggressive environment impact. It is confirmed by e.g. their higher compressive strength, and thus the reduced total porosity. Reduction of total porosity content (<50 nm) was accompanied by the increased compressive strength, which in the aqueous environment was in favour of cement mortars, and in the aggressive environment in favour of cement and ash mortars. It was demonstrated that the content of pores < 200 nm was lower for mortars with FBC fly ashes and mixtures of ashes regardless of environment the mortars were stored in. A beneficial impact of FBC fly ashes was found on physical properties of mortars, i.e. reduction of the shrinkage, lower mass loss and reduced destruction of mortars in the acid corrosion environment. That effect was especially beneficial for the mortar with higher (45% by mass) content of FBC fly ashes, regardless of aggressive character of the environment.

Strategy to control indoor temperature for redevelopment of slum dwellings

The present paper focuses on developing a strategy to control the indoor temperature in slum dwellings under redevelopment. The proposed framework aims at improving the building planning and appropriate selection of construction materials along with controlled cost with respect to currently adopted practices. The proposed strategy is elaborated with a case study in Nagpur, India. A single storey, four-room model was planned as per the National Building Code of India. The performance of the model building was evaluated by using energy simulation software TRNSYS. The cellular light-weight bricks used in the construction were made with bio briquette ash (BBA), which is a locally available waste material. Instead of using the conventional reinforced cement concrete (RCC) roof, aluminium and sawdust were suggested as a reflecting-cum-insulating material. To improve the temperature control in model homes, installation of a reflecting-cum-insulating material was conducted, consisting of aluminium and sawdust, over the conventional RCC roof. The model building constructed with these new materials was compared with that built with conventional fly ash bricks and RCC roof. Results show that the proposed model building improved the efficiency of indoor temperature control by 23% and, at the same time, reduced the cost by 13%. The present concept will contribute to the redevelopment of slum dwellings to deliver cost-effective dwelling units that provide occupants with acceptable thermal comfort.

Mechanical properties and adiabatic temperature rise of low heat concrete using ternary blended cement

This study examined the mechanical properties and adiabatic temperature rise of low-heat concrete developed based on ternary blended cement using ASTM type IV (LHC) cement, ground fly ash (GFA) and limestone powder (LSP). To enhance reactivity of fly ash, especially at an early age, the grassy membrane was scratched through the additional vibrator milling process. The targeted 28-day strength of concrete was selected to be 42 MPa for application to high-strength mass concrete including nuclear plant structures. The concrete mixes prepared were cured under the isothermal conditions of , , and . Most concrete specimens gained a relatively high strength exceeding 10 MPa at an early age, achieving the targeted 28-day strength. All concrete specimens had higher moduli of elasticity and rupture than the predictions using ACI 318-11 equations, regardless of the curing temperature. The peak temperature rise and the ascending rate of the adiabatic temperature curve measured from the prepared concrete mixes were lower by 12% and 32%, respectively, in average than those of the control specimen made using 80% ordinary Portland cement and 20% conventional fly ash.

Comparative Investigations of some Properties Related to Durability of Cement Concretes Containing Different Fly Ashes

The results of research of mechanical properties and selected other characteristics influencing durability of cement concretes containing cement substitutes were presented. Cement concretes performed with conventional fly ash, fluidised fly ash and their mixture were investigated. The obtained results were compared with findings registered for two types of concrete performed without cement replacements and with cement concrete containing silica fume. The results have shown that cement concrete with predetermined 28-day compressive strength of about 50 MPa and good workability may be obtained using different cement replacements. Generally, these cement concretes exhibited also favorable properties related to concrete durability, i.e. low permeability and sorptivity, and significant reduction of chloride migration coefficient. Favourable results were obtained for cement concrete containing mix of conventional and fluidised fly ashes: good workability, compressive strength after 28th day exceeding 50 MPa, low permeability of water, and low sorptivity, as well as low coefficient of chloride migration. These features were similar as for cement concrete containing silica fume.

Influence of Storage Conditions on Quality of Fly Ashes

The presented paper deals with the issue of influence of storage conditions on the quality of conventional fly ashes which are produced by combustion of lignite. These ashes were stockpiled for long time. A borehole for sampling was made in the fly ash stock-pile. Total depth of the borehole was 20 m. Samples of fly ashes taken from every single meter were analyzed and next mechanical properties and the volume stability of materials containing these fly ashes were tested. The quality of fly ashes especially with respect to the possibility to use them as components of pastes, mortars and concretes as pozzolanic admixture or fine filler was evaluated.

Comparison of innovative nano fly ash with conventional fly ash and nano-silica

This report is an experimental study on the nano-powdering of fly ash and the improvement of cement performance by nano fly ash. Mortars with nano fly ash or nano-silica produced by a physical method are compared with mortar without a nano-binder. Mortar with nano-silica showed rapid setting. However, mortar with fly ash or nano fly ash exhibited delayed setting. The smaller the particle sizes, the higher is the compressive strength, demonstrating that mortar with nano fly ash shows superior performance with higher compressive strength from the beginning. Durability assessments revealed that chloride penetration resistance increased by 70% for mortar with nano fly ash or nano-silica. This shows that mortar with a smaller particle binder has excellent carbonation resistance. Nano-powdering effectively enhances the activation of a pozzolanic reaction and provides densely charged effects. These changes solve the problem of initial strength reduction — the greatest weakness of fly ash.

Comparing the performance of fine fly ash and silica fume in enhancing the properties of concretes containing fly ash

Fine fly ash which is obtained by classification of conventional fly ash has become available to concrete industry in recent years. In the current research the possibility of using fine fly ash in binary and ternary mixes with the aim of overcoming the rather slow rate of strength development in concretes containing conventional fly ashes or enhancing their durability was investigated.The results show that the rate of pozzolanic reaction of fine fly ash is only moderately higher than conventional fly ash and the water demand is slightly reduced. The results of ternary mixes show that fine fly ash is not an effective material for increasing the rate of development of properties in concretes containing slow reacting pozzolans such as conventional fly ashes. The results of tests assessing durability of concrete against chloride ingress such as RCPT, RCMT and electrical resistivity indicate that the use of this material does not improve concrete durability over that which can be achieved by conventional fly ash at equal replacement levels.

Surface Scaling Resistance of Concrete with Fly Ash From Co-Combustion of Coal and Biomass

The co-combustion of coal and biomass is connected with enforcing EU regulations concerning the application of renewable sources of energy. The more widely and efficiently that fuel is utilized the better this fact affects the ecology as well as the economy. The combustion of biomass and coal in thermal power stations gives a lot of benefits in comparison to coal burning only. The properties of fly ash from combustion of fuel mix including 80% of biomass and 20% of bituminous coal were described. Because of significant differences between fly ash tested and conventional fly ash, the ways of its application cannot be indicated without the risk of decrease in durability of concrete due to freezing and thawing. The results of frost resistance test of concrete with fly ash (fab) from co-combustion were presented. The frost resistance was evaluated based on the mass of scaled material related to the concrete surface subjected to 112 cycles of freezing and thawing in the presence of 3% NaCl solution. The statistical analysis of test results indicates that the introduction up to 25% of ground fly ash from co-combustion of biomass and coal to concrete, considering the air-entraining agent and proper curing conditions allows obtaining the durable concrete for structures subjected to external environmental influences

Effects of olive residue biomass fly ash as filler in self-compacting concrete

Fine materials, such as fly ash from coal combustion, have been used to reduce the amount of superplasticizer and to manufacture concrete with standard properties. Because of the pozzolanic contribution of conventional fly ash concrete, fly ash can also be used as a partial substitute for cement. However, no results have ever been published on the use of fly ash as filler. This paper presents the results on the use of fly ash from the combustion of agricultural olive residue pellets as filler in self-compacting concrete. This study analyzed the characteristics of biomass fly ash, which was then used to manufacture specimens and obtain the optimal fly-ash dosage for the concrete. The properties of the reference concrete made with conventional filler and the biomass fly ash concrete were compared, as well as their compressive strength after 3, 7, and 28days. The laboratory tests showed that the biomass fly ash concrete had a compressive strength that was equal to or greater than that of the reference concrete. These results clearly indicate that biomass fly ash can be used to manufacture high-quality self-compacting concrete.

Flowable Fill Using Flue Gas Desulfurization Material

Abstract Flowable fills are an effective and practical alternative to commonly used compacted earth backfills. Flowable fill is a cementious material, commonly a blend of cement, fly ash, sand, and water, that does not require compaction, may be self-leveling at time of placement, may harden quickly within a few hours, and can be excavated in the future if need be. Many flue gas desulfurization (FGD) materials have low unit weight and good shear strength characteristics and thus hold promise for flowable fill applications. This paper focuses on the potential of using two types of FGD materials (spray dryer and wet fixated FGD material) in flowable fill as a replacement for conventional fly ash. Several design mixes were considered. The design mixes consisted of varying amounts of FGD material, cement, lime, and water. The mixes were tested in the laboratory for flowability, unit weight, moisture content, unconfined compressive strength, erodibility, set-time, penetration, and long-term strength characteristics. Tests were conducted for up to 90 d of curing. Without any additives, the FGD material was observed to be as good as a regular (normal set) flowable fill in terms of placeability, unconfined compressive strength, and diggability. FGD material flowable fill with additives and admixtures compares favorably with the characteristics of conventional quick set flowable fills.

Cementitious materials based on fluidised bed coal combustion ashes

This paper summarises work aimed at developing cementitious materials based on fluidised bed coal combustion ashes. It was found that such ashes, unlike most conventional fly ashes, exhibit distinct hydraulic properties and – if mixed with appropriate amounts of water – set and harden spontaneously at ambient temperature, yielding a C—S—H phase and ettringite as main products of hydration. Under hydrothermal conditions the hydrogarnet phase is formed as the main reaction product, together with tobermorite and anhydrite. Depending on the composition of the ashes, the strength of the hardened material can be enhanced by the addition of some other cementitious constituents, particularly blast furnace slag. Due to the favourable strength-to-bulk density ratio, the hardened material may be considered a lightweight cementitious product.

Cementitious materials based on fluidised bed coal combustion ashes

This paper summarises work aimed at developing cementitious materials based on fluidised bed coal combustion ashes. It was found that such ashes, unlike most conventional fly ashes, exhibit distinct hydraulic properties and – if mixed with appropriate amounts of water – set and harden spontaneously at ambient temperature, yielding a C—S—H phase and ettringite as main products of hydration. Under hydrothermal conditions the hydrogarnet phase is formed as the main reaction product, together with tobermorite and anhydrite. Depending on the composition of the ashes, the strength of the hardened material can be enhanced by the addition of some other cementitious constituents, particularly blast furnace slag. Due to the favourable strength-to-bulk density ratio, the hardened material may be considered a lightweight cementitious product.

Evaluation of a dry FGD material as a flowable fill

Many flue gas desulfurization (FGD) materials have low unit weight and good shear strength characteristics and thus hold promise for flowable fill applications. This paper focuses on the potential of using spray dryer FGD ash in flowable fill as a replacement for conventional fly ash. Several design mixes were considered. The design mixes consisted of varying amounts of FGD, cement, lime, admixture, and water. The mixes were tested in the laboratory for flowability, unit weight, moisture content, unconfined compressive strength (UCS), erodibility, set time, penetration, and long-term strength characteristics. Tests were conducted for up to 90 days of curing. The FGD flowable fill without any additives was observed to be comparable to regular (normal set) flowable fill in terms of placeability, UCS, and ‘diggability’. FGD flowable fill with additives and admixtures compared favorably with the characteristics of conventional quick-set flowable fills.

Possibilities of Utilizing Solid Residues from Pressured Fluidized Bed Coal Combustion (PSBC) for the Production of Blended Cements

Solid residues produced in pressurized fluidized bed combustion differ in their chemical and phase composition from those produced under atmospheric pressure and even more from conventional fly ashes. They usually exhibit distinct hydraulic/pozzolanic properties and thus may be used, in combination with Portland clinker, as constituents of blended cements. Due to their high SO 3 content, the addition of gypsum to such binders has to be adjusted accordingly.