Sintered Fly Ash Aggregate Research Articles

Characterization and behavior of basalt fiber‐reinforced lightweight concrete

AbstractThe improvised construction techniques and utilization of industrial wastes in manufacturing concrete play a major role in sustainability. The artificially manufactured aggregates are gaining importance in the present era. The use of fibers as secondary reinforcement is greatly pronounced. Sintered fly ash aggregate concrete and normal aggregate concrete with and without basalt fiber with 28 days compressive strength of 30 Mpa were cast and tested. The stress–strain curve of the lightweight concrete has a lower modulus of elasticity when compared with the normal aggregate concrete. A simple linear relationship has been developed between the mechanical properties using regression analysis. The water absorption and void ratio had a direct relationship with the sorptivity and ponding of concrete. The strength and durability aspects of the lightweight aggregate concrete had better agreement with the requirements of the structural lightweight concrete. Strict adherence to codal provisions with respect to strength and durability can be made for improvised behavior.

Mechanical characterization of structural lightweight aggregate concrete made with sintered fly ash aggregates and synthetic fibres

This study explores the development of fibre reinforced structural lightweight aggregate concrete (SLWAC) using sintered fly ash aggregate (SFA) as coarse aggregate. SFA is manufactured from fly ash, an industrial by-product, thus making SLWAC a sustainable building material. SLWAC of density 1800 kg/m3 is developed with and without the addition of synthetic polyolefin (macro and micro) fibres to achieve a target compressive strength of 40 MPa. The main objective of this study is to understand the mechanical properties of SLWAC made of SFA and the influence of fibres in improving mechanical properties of SLWAC. The effect of monofilament macro-synthetic fibre dosages of 0.2%, 0.4%, and 0.6%, as well as the fibrillated micro fibres of 0.02% on the mechanical properties of SLWAC is studied. Tests were carried out for understanding the stress-strain behaviour under compression, split tensile strength, and fracture behaviour under flexure. Digital image correlation technique is used to study the crack propagation in fracture and splitting tension tests. A significant improvement in flexural strength, splitting tensile strength and toughness of SLWAC is observed due to the addition of synthetic fibres. Fibres significantly contributed to load resistance by arresting both micro and macro cracks. Thus, with the help of synthetic fibres addition in SLWAC, the desirable mechanical properties for structural applications such as strength and ductility can be achieved at reduced density.

Experimental study on full-volume fly ash geopolymer mortars: Sintered fly ash versus sand as fine aggregates

In this study, the concept of “full-volume fly ash (FVFA) geopolymer mortar” is proposed using FA geopolymer as a binder and sintered fly ash aggregates (FAAs) to fully replace the conventional river sand (by volume), aiming to conserve natural sand resources through further utilizing of FA. The influences of the FAAs, the alkali concentration, and curing regime on the physical, mechanical, microstructure, and mineralogy properties of the FVFA geopolymer mortars were experimentally evaluated. The properties of the conventional river sand control mortars were used as a benchmark reference. The results indicated that both compressive strength and density of the FVFA geopolymer mortars were relatively lower compared to that of the control mortars. The change of alkali concentration and steam-curing duration could generate a wide variant range of the compressive strength and density. Further, the FVFA geopolymer mortars were found to have much higher total porosity relative to the control mortars. The drying shrinkage of the FVFA geopolymer mortars was much lower than that of control mortars due to the internal curing effect of the FAAs. It was challenging to identify the interfacial transition zone (ITZ) between the sintered FAAs and the FA geopolymer binder relative to that between sand and paste in control mortars. It was found that the external layer of the FAAs has reacted with the alkaline solution while the internal core remains relatively stable during the 28 days.

A comparative study on prediction models for strength properties of LWA concrete using artificial neural network

In this study, Artificial Neural Network (ANN) model is constructed to predict the compressive strength, split tensile strength and flexural strength of lightweight aggregate concrete made of sintered fly ash aggregate. An empirical relationship between the compressive strength, split tensile strength, and flexural strength was developed and compared with that of experimental results. The models were formulated based on results obtained from laboratory experiments. The variables considered in the study are the quantity of cement and water-cement ratio. Feed forward neural network and Levenberg-Marquardt back propagation algorithm were used for training algorithm in ANN. Amongst the total data, approximately 70% of the data was considered for training, 15% for testing and the remaining 15% has been considered for validation. The developed models had more accuracy with minimum error and had a higher correlation with the correlation coefficients of 0.916 and 0.955 were obtained for the training and testing data of compressive strength prediction, 0.949 and 0.937 respectively for split tensile strength prediction, 0.926 and 0.928 respectively for prediction of flexural strength. The models were compared with the experimental data’s, and the results were discussed.

Durability and microstructural properties of lightweight concrete manufactured with fly ash cenosphere and sintered fly ash aggregate

This paper addresses the durability and microstructural characteristics of lightweight concrete prepared by using fly ash cenosphere (FAC) and sintered fly ash aggregate (SFA) as replacements of natural fine and coarse aggregate, respectively. To fulfil this objective, sixteen concrete mixes are produced by using FAC and SFA, in various combinations i.e. 0%, 50%, 75% and 100% for each. Properties of concrete, such as compressive strength, resistance to sulphate, acid and chloride attack of concrete are studied. Further, the scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses for these concrete mixes are performed in support of the above strength and durability behaviours. The results of the present study reveal that though the compressive strength decreases with incorporation of FAC/SFA/both of these, appreciable strength is achieved using high volume of FAC and SFA (50% FAC and 75% SFA), which is also comparable to the strength of concrete without FAC and SFA. Further, the above mix achieves the required target strength of M25 grade concrete for which design mix is made as per IS 10262 (2009). It is found from the durability results that on one hand, the strength loss in concrete caused by sulphate attack and acid attack increases with increase in percentages of individual and combined substitution of FAC and SFA and hence, the concrete comprising FAC and SFA is not suitable for the structures exposed to acidic environments. On the other hand, when FAC or SFA or both of these contents increases, the depth of chloride ingress decreases, exhibiting better performance in saline environments than the concrete mix without FAC and SFA. The XRD and SEM analyses confirm the strength and durability characteristics of these mixes.

Experimental Study on Mechanical Properties of Sintered Fly Ash Aggregate in Concrete

Experimental Study on Mechanical Properties of Sintered Fly Ash Aggregate in Concrete

Development of sustainable lightweight concrete using fly ash cenosphere and sintered fly ash aggregate

The present research work explores the use of fly ash cenosphere (FAC) and sintered fly ash aggregate (SFA) as replacements of natural fine aggregate (NFA) and natural coarse aggregate (NCA), respectively, for development of sustainable structural lightweight concrete (LWC). Total sixteen concrete mixes have been prepared by replacing both NFA and NCA with FAC and SFA, respectively, having different combinations i.e. 0%, 50%, 75% and 100% each. The effects on the properties of the concrete mixes like workability, plastic and dry density, compressive, split tensile, flexural and bond strength, water absorption, volume of permeable pores, pulse velocity and rebound number, due to inclusion of FAC and SFA, are experimentally investigated and catalogued. Based on the content of FAC and SFA, the 28 days compressive, split tensile, flexural and bond strength are found to be within the range of 19.35–32.04 MPa, 1.83–3.48 MPa, 1.81–4.27 MPa and 6.95–8.33 MPa, respectively. The density of the above mixes ranges from 1226 kg/m3 to 2048 kg/m3. From this study, it is concluded that the structural LWC can be produced with the use of high volume of waste products, such as FAC and SFA, which minimize the waste disposal problems and preserves the natural resources. It is worth mentioning that out of fifteen concrete mixes with FAC and SFA considered here, all the mixes except two mixes, i.e. concrete mixes with 50% FAC only and 50% SFA only, satisfy the requirements of structural LWC as per ACI 213R-03. In spite of these advantages, the LWC mixes produced using SFA and FAC possess higher water absorption and volume of permeable pores as compared to the normal concrete, which shows the concern on the durability aspects of these LWC mixes. Hence, the durability properties of these concrete mixes are to be investigated in order to find their suitability in the construction. Moreover, the microstructural study needs to be carried out to support the trends of the mechanical properties of the concrete mixes using SFA and FAC observed in the present investigation.

Experimental Investigations on Punching Shear of Flat Slabs Made from Lightweight Aggregate Concrete

Abstract In the paper the results of experimental investigations concerning flat slabs made from reinforced lightweight concrete with sintered fly ash aggregate CERTYD were presented. In the research program 6 models made in a natural scale were included. The main variable parameter was slab longitudinal reinforcement ratio. The aim of investigation was the experimental verification of efficiency of double-headed studs as punching shear reinforcement. In the existing technical approvals such kind of reinforcement was allowed only in normal concrete slabs. It was demonstrated that double-headed studs can be an effective transverse reinforcement of lightweight aggregate concrete slabs. The use of double-headed studs resulted in increase in the ultimate load from 19% to 44%, depending on the slab reinforcement ratio which ranged from 0.5% to 1.2%. The comparative analysis showed that the Eurocode 2 provisions were conservative in relation to the experimental results, which were on average 42% higher than the theoretical ones however with a very low 7% coefficient of variation.

Lightweight self-compacting concrete with sintered fly-ash aggregate

The article presents the results of research assessing the possibility of making LWSCC from the locally produced sintered fly ash aggregate CERTYD. Two methods of preliminary LWA preparation were applied: pre-soaking with water and coating with a film of cement paste. The following properties of fresh LWSCC were evaluated: slump-flow, time T500 and passing ability using L-Box. Partial replacement of natural sand by fine LW sand (0/0.5 mm) improved filling and passing abilities of fresh concrete, reduced slightly the bulk density, but it resulted in compressive strength loss by 12-18%. In terms of both fresh and hardened concrete properties it is more favorable to use only fine LW sand as natural sand replacement. Considering fresh concrete properties paste impregnation of LW aggregate is more efficient than saturation with water.

An Investigation of the Mechanical Properties of Sintered Fly Ash Lightweight Aggregate Concrete (SFLWAC) with Steel Fibers

Abstractthis study investigates the fresh and mechanical performance of concrete incorporating sintered fly ash lightweight aggregates (SFLWA) both with and without steel fibers. Comparative assessments of natural aggregates with sintered fly ash aggregates were evaluated. Mix design was obtained by the IS method for M30 grade concrete, and within the natural aggregates were replaced with 20%, 40%, and 60% amounts of SFLWA. The addition of SFLWA shows an increase in the workability of the concrete. Replacement with SFLWA increases with an increase in slump value, and decreases in strength parameters. Compressive strength of 42.6 MPa was achieved with a 40% replacement of SFLWA with steel fibers. The mechanical properties such as compressive strength, split tensile strength, flexural strength, elastic modulus, and structural efficiency of SFLWAC were examined, both with and without fibers. The incorporation of fibers drastically improved the mechanical properties of the mix.

Influence of type of binder on high-performance sintered fly ash lightweight aggregate concrete

Concrete industry consumes natural resources in a massive manner. As the demand for concrete is growing, one of the effective ways to minimize the harmful effect of concrete is to improve its structural efficiency and durability performance. In the current study, the possibility of making high performance structural lightweight aggregate concrete using sintered flyash aggregate was investigated. The study also identifies the influence of silica fume and metakaolin on the performance of the lightweight aggregate concrete. The mechanical properties, such as compressive strength, splitting tensile, elastic modulus and drying shrinkage, and the durability properties like surface resistivity, chloride migration, carbonation rate and corrosion rate were investigated. All the developed concretes attain the strength required to qualify them as high strength concretes. The results demonstrate that the improvements in mechanical properties are marginal by the inclusion of silica fume and metakaolin, whereas significant enhancement to durability was observed. The carbonation results indicates that carbonation is no longer a concern for the developed concretes. It was also noticed that the mechanical and durability properties enhanced with age of curing.

Flexural Study on Slab Specimens with Partial to Fully Replacement of Natural Coarse aggregate by Sintered Fly Ash Aggregate

Flexural Study on Slab Specimens with Partial to Fully Replacement of Natural Coarse aggregate by Sintered Fly Ash Aggregate

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

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.

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.

Investigation on the Development of Light Weight Concrete with Sintered Fly Ash Aggregate and Activated Fly Ash in Blended Cement

Investigation on the Development of Light Weight Concrete with Sintered Fly Ash Aggregate and Activated Fly Ash in Blended Cement

Accelerated curing effects on the mechanical performance of cold bonded and sintered fly ash aggregate concrete

This study investigates the mechanical performance of concrete incorporating fly ash based light weight aggregates. Comparative assessment on the physical and mechanical properties of cold bonded and sintered fly ash aggregates were evaluated systematically. Design concrete mixes were theoretically arrived using aggregate packing concept with different combinations of two phase system (mortar and fly ash aggregate). Experimental test results indicated favorable mechanical strength improvements of concrete incorporating sintered fly ash aggregates compared to cold bonded aggregates. Test results also demonstrated that the composite strength of concrete was found to be improved when the ratio of volume of coarse aggregate to volume of cement mortar is lower. Most notably, the sintered fly ash aggregate (62%) substituted concrete mixes exhibited a maximum compressive strength of 39.97MPa when subjected to hot water curing. In general, favorable strength gain properties were noted in the case of fly ash aggregate concrete specimens exposed to either accelerated steam or hot water curing. Effects on the strength properties of various fly ash aggregate concretes subjected to various durability tests were also reported in this study.

The Effect of Lightweight Aggregate Water Absorption on the Reduction of Water-cement Ratio in Fresh Concrete

The aim of this paper is to present the problem of water-cement ratio reduction in structural lightweight concrete as a result of mixing water absorption by the lightweight aggregate. The research was carried out on eighteen concrete mixtures made of sintered fly ash aggregate and cement pastes of different nominal water-cement ratios. It has been demonstrated that the rate and the extent of the absorption of mixing water by the aggregate in concrete is dependent not only on its water absorption, but also on its moisture content, moisture state, the procedure of concrete preparation and the concrete composition. Moreover, it has been proved that the standard method for calculation of the so-called effective water-cement ratio is accurate only in the case of high initial moisture content of the lightweight aggregate. When dry sintered fly ash aggregate is used, the standard method gives underestimated values of the ratio as compared to its actual values determined in tests.The effect of mixing water absorption by the lightweight aggregate, revealed in tests of fresh concrete as the reduction of water-cement ratio, was also reflected in hardened state of concrete as the increase of its strength. The strength increase was higher for mixtures with higher content of lightweight aggregate. Although the porous aggregate is the weakest element in structural lightweight concrete, in this case its higher content may be compensated with excess by the stronger cement matrix resulting from the reduction of water-cement ratio.

English

English

Physical characteristics of sintered fly ash aggregate containing clay binders

A comprehensive research has been conducted to explore the influence of sintering on the properties of fly ash aggregate containing clay binders (bentonite and kaolinite). Fly ash aggregate containing clay binders, have been subjected to various sintering temperatures at different durations of 700–1400 °C and 15–120 min, respectively. The variation in aggregate properties, viz strength, water absorption, density and shrinkage during sintering, have been determined and discussed. In addition to these, the uniformity of sintering and rate of water absorption of sintered aggregate were also determined. No significant changes in aggregate properties were observed for aggregate sintered up to 900 °C, due to the insufficient sintering temperature range. However, the aggregate properties substantially enhanced for temperature above 1000 °C, which is attributed to the activation of liquid phase sintering. For temperatures between 1000 and 1300 °C, the aggregate with bentonite shows significant increase in shrinkage (30 %), density (density ratio 0.70), higher ten percent fines value (TPFV) (6.13 tonne), reduction in porosity (35 %), and water absorption of 4 %. However, at 1400 °C, the aggregate properties degraded due to the decomposition of mineral phases in bentonite. For aggregates with kaolinite, highest TPFV of 8.5 tonne with lowest water absorption of 2 % have been observed at 1400 °C. The presence of a higher amount of interconnected pores for aggregates sintered between 700 and 1000 °C leads to a higher rate of water absorption and then reduces to 30 % for temperatures between 1200 and 1300 and 1200 to 1400 °C for bentonite and kaolinite aggregates, respectively. This reduction is due to the reduced interconnected pores. Duration of sintering has no impact on the aggregate properties for temperatures up to 800 and 1000 °C for aggregates with bentonite and kaolinite, respectively. However, between 1000 and 1400 °C, there has been considerable improvement in the aggregate properties for increasing duration up to 60 min. In comparison, during sintering, aggregates with bentonite possessed better properties for temperature less than 1000 °C, whereas aggregates with kaolinite exhibited superior properties between 1100 and 1400 °C.