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Development of Lightweight Aggregate Concrete Containing Pulverized Fly Ash and Bottom Ash
Abstract
This study examines the feasibility of using different lightweight aggregates (LA) and bottom ash as coarse and fine aggregates in concrete with fly ash. The lightweight materials were composed of 3 types, namely pumice, cellular lightweight aggregate and MTEC lightweight aggregate. The tests for physical and mechanical properties of lightweight aggregate concretes (LWAC) were conducted in terms of workability, compressive strength, apparent density, abrasion resistance and absorption. Test results showed that compressive strength of LWAC increased with an increase in apparent density, which is mainly depending on the type of aggregate. The replacement of normal weight sand with bottom ash resulted in a decrease both in density of concrete by 180-225 kg/m3 and 28-day compressive strength of concrete by 16-26%. Moreover, the use of bottom ash to replace sand in concrete increased the demand for mixing water due to its porosity and shape and to further obtain the required workability. The type and absorption of LA influenced predominantly the water absorption of LWAC. Total replacement of natural sand by bottom ash increased the absorption of the concrete by 63-90%. With regard to abrasion resistance, the abrasion resistance of lightweight aggregate concrete was mainly dependent on the compressive strength of concrete: the higher the strength, the higher the abrasion resistance of LWAC. In addition, the use of bottom ash as a fine aggregate resulted in a lower abrasion resistance of lightweight aggregate concrete due to its porosity. Of the three types of lightweight materials, MTEC LA had achieved both low density and high compressive strength.
... Whereas ultra-lightweight concrete has often a low material strength below 15 MPa (2,176 psi) (Kim et al. 2012;Sadrmomtazi et al. 2012;Schlaich and Hückler 2012). Only few studies have focused on lightweight concrete in a density range of 1,200 and 1,600 kg/m³ (75 and 100 lb/ft³) and a moderate strength ranged between 15 and 30 MPa (2,176 and 4,351 psi) (Bhatty and Reid 1989;Glenn et al. 1998;Ke et al. 2009;Litsomboon et al. 2009). ...
Using lightweight concrete enables decrease in dead load and thermal conductivity in case of manufacture of concrete walls. With addition of steel fibers to concrete, its properties are altered from brittle to ductile, so the use of additional mesh reinforcement can be avoided. This study is aimed at investigating the effect of change in steel fiber content on the properties of steel fiber reinforced lightweight aggregate concrete (SFRLWAC). Flow table test was conducted to find the workability of fresh concrete mixture regarding the pumpability. Further compressive strength, modulus of elasticity, flexural strength and oven-dry density were tested. Four mixes of SFRLWAC with two different oven-dry densities (< 1,200 kg/m³ and < 1,600 kg/m³ (< 75 lb/ft³ and < 100 lb/ft³)) and two different fiber contents (0.5 % and 1.0 %) were prepared to study the change in its fresh and hardened properties. The results of this study show a possibility to produce a pumpable, high ductile, lightweight concrete suitable for application in load-bearing walls.
An investigation was done into the development of lightweight-aggregate concrete mixes with lower embodied carbon dioxide emissions suitable for structural applications. Production requires the replacement of normal-weight coarse aggregate with a lightweight aggregate. Lytag was considered, which is a good quality lightweight aggregate manufactured from fly ash. Lightweight-aggregate concrete for structural applications usually contains high Cem I content owing to the requirements for workability, pumpability and strength. Consequently, its embodied carbon dioxide emissions are generally higher than that of normal-weight concrete. Mixes of LC30/33 class were developed containing up to 60% of ground granulated blast-furnace slag, as well as limestone powder, and their fresh and mechanical properties were assessed experimentally. It was found that the embodied carbon dioxide of the investigated mix could be reduced by up to 40% when compared to neat CEM I lightweight-aggregate mixes containing Lytag aggregates and to 20% when compared to a mix that would be generally used in current practice in the UK containing 40% slag. It was also possible to reduce the Cem I content in the investigated mixes by approximately 40% compared to what would have been normally used.
The article presents testing results of non-autoclave structural and heat-insulating foam concrete, made on the basis of astringents of different grades and with different fillers. It has been experimentally established that the best filler for foam concrete is microsilica due to its high specific surface area and low bulk density in comparison with the sand. The use of high-quality binders in foam concrete mixtures allows to increase not only the strength of foam concrete, but also the content of microsilica up to 70% with respect to mixtures at lower brands of Portland cement.
Concrete compressive strength decreases significantly with decreasing density and therefore, there are few examples of structural grade concretes with densities below 1,600 kg/m3. Here we show the development of structural lightweight aggregate concrete in the 1,200–1,600 kg/m3 density range. Compressive strengths of up to 36 MPa are obtained at 28 days. By using fibers, mixes with flexural strengths of up to 7 MPa and high ductility in flexure are obtained at 28 days. These results are significantly better than those in existing literature at comparable densities. Compressive strength of lightweight concrete depends on both paste and aggregate properties, while the flexural strength depends mostly on the volume fraction of fibers used.
The medium size fraction (14–40mm) of aged incinerator bottom ash (IBA) obtained from a major UK energy from waste (EfW) plant has been crushed to less than 5mm (CIBA) and thermally treated at 600°C (TCIBA6), 700°C (TCIBA7), 800°C (TCIBA8) and 900°C (TCIBA9). Thermal treatment reduced the organic carbon content and increased the amount of wollastonite (CaSiO3), mayenite (Ca12Al14O33) and gehlenite (Ca2Al2SiO7). The crushed and thermally treated IBA has been mixed with Portland cement (PC) at different water/solid (w/s) ratios and with different proportions of PC and Ca(OH)2. The volume expansion during setting and bulk densities and compressive strengths were determined. Expansion occurred in all mixes contained IBA during curing. A lightweight material (density less than 1.8g/cm3) with 28day compressive strength of higher than 10MPa was prepared by mixing 20wt% PC with 80wt% TCIBA8 at w/s ratio of 0.20. The expansion and associated lightweight properties result from gas evolution during curing due to residual metallic Al in the IBA. The main crystalline hydration products in 28day cured samples were portlandite (Ca(OH)2), calcite (CaCO3) and calcium aluminate carbonate hydrates (Ca4Al2O6(CO3)0.5·12H2O and Ca8Al4O14CO2·24H2O).
This paper presents the experimental investigations carried out to study the effect of use of bottom ash (the coarser material, which falls into furnace bottom in modern large thermal power plants and constitute about 20% of total ash content of the coal fed in the boilers) as a replacement of fine aggregates. The various strength properties studied consist of compressive strength, flexural strength and splitting tensile strength. The strength development for various percentages (0-50%) replacement of fine aggregates with bottom ash can easily be equated to the strength development of normal concrete at various ages.
This Paper examines the possibility of using bottom ash as partial replacement of fine aggregate (FA) in concrete. Super plasticiser is used to increase the workability of concrete with lower water cement ratio. The percentage of bottom ash added by weight was 0,20,30,40 and 50 as replacement of FA used in concrete. Experimental Investigations carried out to a study the effective use of bottom ash which falls into Thermal power plants (Ennore). But in this paper the various strength properties studied consist of compressive strength, split tensile strength, of and flexural strength of concrete were analysed by replacing bottom ash as fine aggregate. The strength development for various percentages (0-50%) of replacement of fine aggregate with bottom ash can easily be equated to the strength development of normal concrete with various ages.
Furnace bottom ash (FBA) is a by-product from thermal power plants. Unlike its companion, pulverised fuel ash (PFA), FBA has coarse particle size, higher water absorption and usually no pozzolanic effect. Therefore, it is dumped in landfill sites. Past rwcycle attempts of FBA have been mainly focused on using it in blocks, highway embankments, subgrades, sub-bases and structural fills. However, this may still be a source of environmental contamination by way of leached trace elements. A previous investigation carried out by the authors has indicated that FBA would be a potential fine aggregate in concrete. The effects of FBA on workability, compressive strength, permeability, depth of carbonation and chloride transport of concrete were further investigated and the results are reported in this paper. The natural sand was replaced with FBA by 0, 30, 50, 70 and 100% by mass, at fixed free water-cement ratios of 0.45 and 0.55 and a cement content of 382 kg/m3. The results indicated that the workability of the concrete increased with an increase in replacement level of natural sand with the FBA. Most of the FBA concrete was lower in compressive strength than the control that was manufactured with the natural sand up to an age of 28 days for both the water-cement ratios, but most of the FBA concretes were comparable with that of the control concrete at 365 days. The air permeability, water absorption and the carbonation rate at the age of 365 days were higher than those of the control concrete. However, the chloride transport coefficient decreased with the increase of the replacement level of natural sand with FBA up to 50% and it increased beyond this replacement level for both the water-cement ratios. Further investigation is required to assess whether properties of concrete could be improved by taking account of the decrease in water demand of the FBA concrete while determining the water-cement ratio of the mix.
In metropolitan areas and highly populated cities the volume of sludge produced by wastewater treatment plants is enormously high. Incineration of sludge is a common practice to reduce its volume, through a burning process that converts it into ash. Still, a considerable amount of ash is produced, which creates a serious disposal problems. Attempts have been made to study the feasibility of suing sludge ash as a substitute for a portion of fine aggregates in concrete. The results indicate that it could be possible to replace up to 30% by weight of fine aggregate by sludge ash in a concrete mix for normal practice.
Incinerator ash was investigated for its potential use as a replacement for sand and cement in cement mortars. The physical and chemical characteristics of the raw materials were determined. Two sets of mixes were prepared. For the first set, cement and water quantities were fixed while incinerator ash was used at 0%, 10%, 20%, 30% and 40% replacement by weight for sand. In the second set, incinerator ash was used at 0%, 10%, 20% and 30% replacement by weight for cement while sand and water quantities were kept constant. The cement, sand and water mixing proportions were 1:3:0.7, respectively. Slump, compressive strength and unit weight tests were performed on all specimens.Results indicate that incinerator ash caused a reduction in slump values when it was used as a replacement for sand while an opposite trend was observed when it was used as a replacement for cement. The replacement of sand by incinerator ash up to 40% exhibited a higher compressive strength than the control mix (0% incinerator ash) for most curing periods. The maximum compressive strength of 36.4 N/mm2 was achieved using 20% incinerator ash after 28 days of curing. Specimens prepared using 20% incinerator ash replacement for cement yielded a higher compressive strength than the control mix after 14 and 28 days of curing. The maximum compressive strength of 27.4N/mm2 was achieved at 28 days curing period.
Basheer: Influence of Furnace Bottom Ash on properties of concrete
- Y Bai