Fly Ash Aggregate Research Articles

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.

On the rheology of using geopolymer for grouting: A comparative study with cement-based grout included fly ash and cold bonded fly ash

A friendly novel material called geopolymer has recently presented some promising uses for enhancement of weak ground through grouting alternative to Portland cement especially for avoiding from large CO2 emissions during cement production. However, research using the geopolymer technology is still insufficient for grouting specifically concerning with rheology. This paper investigates the rheological properties (shear stress, apparent viscosity, shear rate, yield stress, plastic viscosity) of geopolymer grout in comparison with the cement-based grouts included fly ash and cold bonded fly ash (i.e., geopolymer aggregate) at various dosage rates (0%–100%) and water/binder ratios (0.75–1.5). Some alkaline activator solutions (sodium hydroxide, sodium silicate) and some precursor of aluminosilicate sources (fly ash, silica fume) are used for obtaining the geopolymer grout. Rheometer tests are performed for the grout rheology. It is found from the experimental work that most of the grout mixtures lead to dilatant behavior similar to the one of native cement, while some geopolymer grouts result in the pseudoplastic and Bingham behaviors. All rheological responses of grouts decrease with increased water/binder ratios. While the inclusions of fly ash and geopolymer aggregate bring about minor changes in the rheological properties, the geopolymer grouts mostly result in the magnitudes more pronounced. The grout rheology becomes more close to the ones of native cement by the proportions 30%–40% of fly ash and geopolymer aggregate, and using the geopolymer grout in the combinations with 30%–60% silica fume. The plastic viscosity versus yield stress produces moderate correlations for the grouts with fly ash, but strong correlations for the geopolymer grouts and the grouts with geopolymer aggregate. The study indicates that the geopolymer comparatively attempted with fly ash and geopolymer aggregate could offer many choices for experimenters in practice for feasible grouting compared to native cement.

Investigation into low density fly ash aggregate in micro-concrete for lightweight concrete repair

This paper presents the effect of low density aggregate (LDA) made from fly ash on compressive strength, flexure strength, flexure bond strength, drying shrinkage and shrinkage due to raised temperature for accelerated drying of the micro concrete for concrete repair. Sintered fly ash lightweight aggregate were crushed to required sizes and replaced by weight partially to fully; 50, 60, 70 and 100 percent of the natural aggregate to prepare the micro concretes. The results were compared with the normal weight micro concrete. It was observed that the strengths of the light weight micro concrete were comparable with the strength of normal weight micro concrete with less cement content. The drying shrinkage percentage was also within permissible value. The flexure bond strength was higher and the drying shrinkage due to raised temperature for accelerated drying was also lower in the partial replacement of the LDA. The partial replacement of LDA showed encouraging results for the light weight micro concrete mix for the concrete repair particularly under the beam or slab to reduce gravity load on the bonding interface of the substrate concrete and the micro concrete.

Effect of Duration of Heat Curing on the Artificially Produced Fly Ash Aggregates

This paper presents the results of an experimental investigation on the production of artificial fly ash aggregates through the process of pelletization. The alkaline solutions like sodium silicate and sodium hydroxide was used to activate the fly ash. The alkaline solution contains 4.5% of Na2O, Si2O/Na2O ratio of 0.3 and 20% of water content with respect to mass of fly ash were used as binder in the production of fly ash geopolymer aggregates. The experiments were conducted by varying with different parameters. Curing of artificial fly ash aggregates was done with ambient temperature and heat curing (60 to 80 °C). Six levels of duration of heat curing were considered for this study. The optimum temperature and duration of curing is essential in geopolymerization reaction to achieve good characteristics of the produced aggregates. Grey relation analysis was performed to identify the effect of heat curing. Test results and grey relation analysis shows that the characteristics of the artificial produced fly ash aggregates has significantly improved with increase in temperature and duration of oven curing.

Geopolymer Sand as a replacement to Natural Sand in concrete

Geopolymers are highly alkaline binders used as an alternative for the replacement of OPC in the manufacture of concrete. The advantages of using geopolymers are that they impart excellent mechanical strength, help in reducing carbon di-oxide emission and helps in achieving good durability properties. In addition, the increasing demand for river sand, are leading to environmental effects, thus developing an urgent need to replace river sand with an alternative construction material. Geopolymerization of fly ash in 10 M NaOH and Na2SiO3: NaOH= 1.8:1 solution at 100°C for one hour produced geopolymer fly ash aggregate (GFAS) to produce an alternative replacement for river sand. The specific gravity of GFAS was 1.82 indicating that these particles were light weight. The properties of concrete such as compressive strength and flexural strength was also studied by replacing river sand with GFAS in concrete. It was observed that the mechanical strength of the GFAS was nearly same as that of the river sand concrete, thus indicating GFAS can be used as an alternative material to replace river sand in concrete.

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.

Study on characteristic strength of partially replaced natural aggregates by flyash aggregates in concrete

To explore more benefits of flyash in construction industry, a study has conducted on strength characteristics of M30 grade concrete using manufactured flyash coarse aggregate as a partial replacement of natural granite coarse aggregate.

A novel optimised self-learning method for compressive strength prediction of high performance concrete

Concrete strength (CS) is one of the most important performance parameters that are crucial in the design of concrete structure. The reliable prediction of strength can reduce the cost and time in design and avoid the waste of materials caused by a large number of mixture trials. In this study, a novel predictive model is put forward to predict the CS of high performance concrete (HPC) using support vector machine (SVM) approach, which has benefits of nonlinear mapping, high robustness and great generalisation capacity. In the proposed model, the input variables include the contents of water, cement, blast furnace slag, fly ash, super plasticiser, coarse and fine aggregates and curing age, which produces the CS of HPC as the output. In order to improve the model performance, a type of enhanced cat swarm optimisation (ECSO) is adopted to optimise the key parameters of SVM. Finally, the model is trained and evaluated using a total of 1761 data records, which are collected from existing literatures. The results indicate that the proposed SVM-based model exhibits better recognition ability and higher prediction accuracy than other commonly used models, and it can be considered as an effective method to predict the CS property of HPC in infrastructure practice.

Autoclaved Fly-Ash Pellets as Replacement of Coarse Aggregate in Concrete Mixture

Coal, which is a very promising material for a growing country like India produces fly- ash which is creating a great threat to the environment. Fly-ash is mainly used for dumping or as a fine aggregate. The present study is aimed at developing a technique for producing an aggregate with fly-ash using autoclave and use it in the replacement of normal coarse aggregate. The properties of fly-ash were experimentally checked, whether it is of type-C or of type-F by chemical analysis of the fly-ash. Batches of fly-ash aggregates were manufactured using Autoclaved technique using disc pelletilizer. Based on the cursing value, water absorption, and impact value test results of their properties, fly-ash aggregates were selected. Using the fly-ash aggregates prepared from the Autoclaved technique, their properties were tested. These pellets will be light in weight having specific gravity less than that of gravel (2.67) and will have high impact value than that of gravel (20.12). At the same time, they will also address some of the environmental problems such as disposing the industrial waste which is being generated from thermal waste.

Experimental Investigation on Partial Replacement of Coarse Aggregates by Flyash Aggregate in Concrete

Experimental Investigation on Partial Replacement of Coarse Aggregates by Flyash Aggregate in Concrete

Evolution of 112-day drying shrinkage equation of fly ash blended self-compacting concrete

This investigation is mainly focused on the prediction of 112-day drying shrinkage of self-compacting concrete (SCC) and conventional concrete (CC) blended with or without class F fly ash using symbolic regression. Two logical parameters, namely additive factor (AF) and coarse aggregate points (CAP), have been included in the preparation of input parameters to address the influence of fly ash and coarse aggregate on the drying shrinkage of concrete. The experimental data provided by literature and this investigation have been used for symbolic regression. It is evidently revealed that the evolved equation (AF_CAP_Equation) was able to predict the 112-day drying shrinkage of SCC and CC reasonably. Effect of AF and CAP on the drying shrinkage of concrete mixes has also been discussed.

Developing geopolymer concrete by using cold-bonded fly ash aggregate, nano-silica, and steel fiber

This experimental study presents the effect of nano-silica and steel fiber on the transport properties and compressive strength of alkali-activated slag/fly ash concrete incorporated cold-bonded fly ash aggregate. In order to reduce energy consumption and provide environmental impact, the cold-bonded process was used to manufacture cold-bonded fly ash aggregate. Twenty four geopolymer concrete mixtures incorporated cold-bonded fly ash aggregate, nano-silica, and steel fiber were produced with sodium hydroxide concentration of 12 M and cured at ambient temperature. Transport properties of geopolymers were examined through water penetration, water sorptivity, and gas permeability at 28 and 90 days. Results indicate that geopolymer concrete incorporated cold-bonded fly ash aggregate can be produced with compressive strength as high as 28.23 and 36.62 at 28 and 90 days, respectively. However, 2% nano-silica and 1% steel fiber volume fraction were the most significant parameters that caused remarkable improvement of investigated properties. Moreover, the incorporation of waste materials in aggregate and geopolymer concrete production can alleviate environmental problems.

Improvement of Heat-Insulating Properties of Foam Concrete by Means of Mineral Additives

Foam concrete solidifying in natural conditions significantly shrinks, which causes deterioration of the porous structure and thus the increase in the heat conductivity of the material. One of the solutions for this problem is application of mineral modifiers. As the mineral modifiers the authors used the production waste – mineral additives (wollastonite, diopside) at natural dispersive capacity, as well as milled down to 300 and 600 m2/kg of specific surface. The application of perlite microspheres in foam concrete was investigated. The thermal conductivity coefficient was defined by rapid method. The optimal composition of the mixture for manufacturing foam concrete products with mineral additives ensures the decrease in the heat conductivity coefficient by 41-43% compared to the reference composition. At complete replacement of fly-ash aggregate by perlite microspheres the thermal conductivity coefficient decreases down to 0.062 W/ (m×°С). The economic effect of application of the developed foam concrete with the additive of wollastonite and diopside compared with the foam concrete presented on the market is equal to 259 / 388 RUB/m2 of an erected structure at the density of D300/ D400 respectively. Thus, directed regulation of the porous structure of cellular concrete leads to significant improvement of stability of the foam concrete mixture, which makes the prerequisites to the decrease in the thermal conductivity of the material and positive technical and economical results.

Transportation matters – Does it? GIS-based comparative environmental assessment of concrete mixes with cement, fly ash, natural and recycled aggregates

The urban world is expanding and densifying fast. This requires and produces huge amounts of new construction materials and construction and demolition waste (CDW) every year. Concrete is not only the most important construction material in terms of sheer amount but also regarding embodied greenhouse gas emissions. Alternative concrete mixes have been developed by introducing supplementary cementitious materials (e.g. fly ash (FA)) and CDW (e.g. recycled aggregates (RA)). So far, environmental assessments focus mostly on the production of concrete mixes without considering the transportation-related impacts. This paper appraises the importance of transportation-related impacts of raw materials for concrete production and proposes a new method combining Life Cycle Assessment and geospatial analysis of road transportation of materials. Environmental impacts (EI) of different mixes are assessed for the specific locations of concrete plants. Traditional and alternative concrete mixes are compared to choose site-specifically the mix with lower impacts. For that purpose, two Portuguese cities were considered as case studies. The new method uncovers if and how location of supply and demand for concrete production is important. The results show that for traditional concrete and for mixes incorporating low FA ratio and/or RA, transportation does not matter. However, it matters when choosing between already drastically improved mixes: then, distances from raw materials suppliers to concrete plants can tip the scales of total EI. In fact, the distances to FA and recycling plants influence the selection of the most environmental friendly concrete mix. The method can be applied to other case studies and materials.

The Performance of Controlled Low-strength Material Base Supporting a High-volume Asphalt Pavement

A lack of proper base and subbase materials in pavement construction is one of the common problems in the tropical region worldwide. In many countries such as Thailand, cementitious materials are usually used for ground improvement. Controlled Lowstrength Material (CLSM) was considered in this study as a pavement base material. The CLSM mixes were prepared by varying cement, fly ash and fine aggregate content. Each mixed component was studied for their physical and chemical properties. After mixing, properties of the CLSM were investigated based on the standard testing of fresh concrete and cement-treated base material. The flowability, setting time and bleeding were checked to ensure that the CLSM were self-compacting. The mechanical properties of hardened CLSM were determined by means of CBR, unconfined compressive strength and resilient modulus tests. The resilient modulus results were used in the analytical design of flexible pavement with CLSM base. The critical traffic data under high-volume road collected by the Thailand Department of Highway was adopted in this study. Results show that the CLSM base considerably increased the performance as well as design life of asphalt pavement compared with the conventional crush rock base pavement.

Effect of basalt, silica sand and fly ash on the mechanical properties of quaternary polymer concretes

The aim of this study is to manufacture quaternary polymer concretes (PCs) and optimize the weight percentages of the epoxy resin, ultrafine fly ash, silica sand and basalt aggregates. For this, we first manufactured binary PCs of epoxy/basalt, epoxy/silica sand and epoxy/fly ash and then studied the mechanical properties such as compressive, flexural and splitting tensile strength. The mixture design method was used as an approach for design of experiment to reduce the number of tests and optimize the mechanical strength of the PC. The best weight percentages of the PC components were 25 (epoxy), 5 (fly ash), 52.5 (silica sand) and 17.5 (basalt). The compressive, flexural and splitting tensile strength of the quaternary PC were equal to 94.1, 39.0 and 11.8, which were 3.76, 11.1 and 6.5 times higher than those of ordinary Portland cement, respectively. Finally, a scanning electron microscopy test was implemented to study the microstructure of the PC.

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

Parametric study on the compressive strength geopolymer paving block

This paper reported about the investigated of sodium hidroxida concentration, effect of ratio liquid to solid (L/S), temperature and time on the compressive strength of geopolymer paving block using fly ash and fine aggregate as base material and combination of sodium hidroxida and sodium silicate as alkaline activator and the ratio of Na2SiO3/NaOH was 2 and fly ash to aggregate of 1: 3. The experiments were conducted with variation of the sodium hidroxida concentration of (10-16 M) liquid to solid (L/S) 0.1- 0.7 ratio, curing temperature 30-100 °C and curing time (7-28 day). The main evaluation techniques in this experimental were Compressive strength, X-ray diffraction (XRD),and Scaning Electron Microscope (SEM). The result showed that the compressive strength of Geopolymer Paving block has increased with an increasing of concentration, liquid to solid ratio, curing temperature and curing time.