Production Of Lightweight Aggregates Research Articles

Comparative Appraisal of Tunisian and Portuguese Smectitic Clays as Raw Materials for the Production of Light Weight Aggregates

Comparative Appraisal of Tunisian and Portuguese Smectitic Clays as Raw Materials for the Production of Light Weight Aggregates

Engineering properties of lightweight aggregate concrete made from dredged silt

Abstract Silt dredged from reservoirs can be hydrated and sintered into lightweight aggregate for producing lightweight aggregate concrete (LWAC). The densified mixture design algorithm (DMDA) was employed to manufacture LWAC using 150 kg/m3 of water at different water-to-binder ratios (w/b = 0.28, 0.32 and 0.4) using lightweight aggregates of different particle densities (800, 1100 and 1500 kg/m3). The engineering properties of the LWAC thus obtained were examined. Results show that the fresh concrete meets the design requirement of having slump of 250 ± 20 mm and slump flow of 600 ± 100 mm. With respect to hardened properties, the compressive strength, ultrasonic pulse velocity and thermal conductivity were found to decrease with increasing w/b ratio but increase with increasing aggregate density. Moreover, higher aggregate density also resulted in less shrinkage. The surface resistivity exceeding 20 kΩ-cm also matched the design objective. The experimental results prove that LWAC made from dredged silt can help enhance durability of concrete.

Lightweight Aggregates from Industrial Sludge–Marine Clay Mixes

Waste disposal problems are often the result of rapid industrial and economic developments in land-scarce municipalities. Waste utilization could be a viable choice to alleviate the problems by transforming wastes into useful products while conserving natural resources. Previous studies by the writers indicated that in the process of thermal conversion of industrial sludge and dredged marine clay mixes into concrete aggregates, pyro-expansion and bloating were often exhibited by the aggregates. The expansion and bloating mechanisms, however, have not been looked into in greater detail. This research examines the petrology of sintered industrial sludge–marine clay aggregates in order to better understand the mechanisms leading to pyro-expansion and bloating of the aggregates. The study would enable development of an efficient and cost-effective bloating methodology for lightweight aggregate production. Main factors investigated were sludge–clay mix proportions, firing temperatures, and salt additives. The investigation revealed that firing at temperatures of 1,200 and 1,300°C produced aggregates of lower specific gravity in the range of 0.5–1.6. The highest aggregate porosity can be achieved at 1,200°C with a clay content of 50%. Scanning electron microscope images indicated that the intrinsic lightweight characteristic of the aggregates could be attributed to large pores within a dense surrounding matrix. The effect of lightweight structures may be ascribed to the release of volatile substances at each respective peak endothermic transitions during firing. The release of substances in vapor form required a large amount of energy, which resulted in the peak endothermic transitions that correspond to the formation of the porous lightweight structures. The results suggested that it is possible to promote pores formation in the production of aggregates possessing lightweight characteristics through careful control of temperature and the selection of sludge–clay proportion.

Neapolitan Yellow Tuff as raw material for lightweight aggregates in lightweight structural concrete production

The possibility of using Italian zeolitized volcanoclastites for the production of lightweight aggregates in the building industry has been tested. The present paper definitely demonstrates the good attitude of the Neapolitan Yellow Tuff (NYT) for the production of lightweight expanded aggregates (LEA) with bulk densities ranging between 0.9 and 1.1 g/cm 3. LEAs showing these features, usually manufactured with clays, are mainly used in the production of lightweight structural concretes (LSC). The physical characterization of LEAs was carried out by means of: grain size analysis, loose weight, mean density of the single grain, water absorption after 30 min and 24 h, and strength of particles (UNI-7549). Afterwards, LEAs were mixed with sand, cement and water to prepare cubic concrete blocks following the UNI specifications (UNI-7549-12). On these specimens, the unit weight and uniaxial compressive strength after 28 days were determined. The investigated parameters measured both on LEAs and concretes, are comparable with those measured on materials commonly traded in Italy. The obtained results foresee interesting potential applications of a raw material characterized by a low exploitation cost and a widespread availability on the Italian territory.

Characterization of lightweight aggregates produced with clayey diatomite rocks originating from Greece

A clayey diatomite rock originating from Greece, mainly composed of opal-A, smectite and vermiculite was tested for the production of lightweight aggregates (LWAs) by mixing the raw material with 2–5% sawdust. The mixtures were pelletized, dried at 100 °C and burnt to 1100 °C. The laboratory LWA had strength and density similar to commercial LWAs originating from Germany and Denmark. The porosity of their mantle was lower than that of the inner part. Pores were abundant ranging from irregular to spherical and from 2 to 500 μm in size, resulting in low apparent density values. The texture of the Greek and German LWA was clearly amorphous, whereas subhedral crystal assemblages were detected in the interior of the Danish LWAs. LWA produced by the Greek clayey diatomite rocks can be utilized for the production of LWA on an industrial scale.

Zeolitic Tuffs as Raw Materials for Lightweight Aggregates

The aim of this research is to assess the possible use of Italian zeolitic rocks for the production of lightweight aggregates. In particular, both the expansion at high temperature and the technological features of fired products were investigated. Fifteen zeolite-bearing volcanoclastites from Northern Sardinia and three zeolitized tuffs from Campania and Tuscany (Sorano and Campanian ignimbrites and Neapolitan Yellow Tuff) were taken into account. The firing expansion turned out to be mainly dependent on the chemical composition (especially SiO 2 and fluxing oxides such as Fe 2 O 3 , Na 2 O, K 2 O, MgO and CaO) and the water content (largely related to the zeolite amount) of the raw materials. Other relevant parameters were the temperature of maximum expansion (ranging between 1350 and 1500 °C, without additives) and soaking time (between 2 and 5 min). Some products are highly impervious to water (water absorption below 1%) and exhibit a considerable firing expansion (> 100% in volume), a low bulk density (0.5–0.7 g•cm −3 ) and fair technical properties (loose weight and strength of particles). These encouraging results make some of the investigated tuffs interesting raw materials for the production of lightweight aggregates.

Zeolitic tuffs as raw materials for lightweight aggregates

The aim of this research is to assess the possible use of Italian zeolitic rocks for the production of lightweight aggregates. In particular, both the expansion at high temperature and the technological features of fired products were investigated. Fifteen zeolite-bearing volcanoclastites from Northern Sardinia and three zeolitized tuffs from Campania and Tuscany (Sorano and Campanian ignimbrites and Neapolitan Yellow Tuff) were taken into account. The firing expansion turned out to be mainly dependent on the chemical composition (especially SiO 2 and fluxing oxides such as Fe 2O 3, Na 2O, K 2O, MgO and CaO) and the water content (largely related to the zeolite amount) of the raw materials. Other relevant parameters were the temperature of maximum expansion (ranging between 1350 and 1500 °C, without additives) and soaking time (between 2 and 5 min). Some products are highly impervious to water (water absorption below 1%) and exhibit a considerable firing expansion (>100% in volume), a low bulk density (0.5–0.7 g·cm −3) and fair technical properties (loose weight and strength of particles). These encouraging results make some of the investigated tuffs interesting raw materials for the production of lightweight aggregates.

Light Weight Aggregates made from Dredged Harbour Sediments

Goal Annually, 400.000 m3 harbour sediments are dredged to maintain the water depth in the harbours of Bremen and Bremerhaven. The sediment contains organic and inorganic pollutants and hence is deposited on a landfill. Because of the limited capacity of that landfill alternative treatment techniques are investigated. This study aims to evaluate the production of Light Weight Aggregates (LWA) from harbour sediments with respect to the product quality and environmental aspects of the use of the LWA.

Properties of high-performance LWAC for precast structures with Brazilian lightweight aggregates

An experimental study was carried out to examine five mixtures made with selected Brazilian lightweight aggregates in order to produce lightweight aggregate concrete (LWAC) for slim precast components. Flow (initial and after 2 h), air content, compressive strength, tensile strength (flexural and splitting), modulus of elasticity and deformation were studied. The 7-day compressive strength and the dry concrete density varied from 39.7 to 51.9 MPa and from 1460 to 1605 kg/m 3, respectively. The results of this pilot study suggest that there are possibilities of producing slim precast components using high-performance lightweight concrete with Brazilian lightweight aggregates.

Lightweight aggregate based on waste glass and its alkali–silica reactivity

The possible use of waste glass for the production of lightweight aggregate has been studied. The aggregate, in the form of highly porous granules, was produced by mixing together finely ground waste glass and an expansive agent and firing this mixture at a selected temperature. The expansive agent was chosen on the basis of the results of DTA/TGA experiments, which were carried out on some selected agents and confirmed by using a hot-stage microscope, where the temperature interval of the expansion was also determined. Pilot production of about 0.5 m 3 of the aggregate was performed in a rotary kiln, and the water absorption and bulk density of the aggregate so obtained were determined. Special emphasis was placed on the determination of the alkali–silica reactivity of the aggregate, and the results of initial tests for alkali–aggregate reaction were encouraging, given the high potential reactivity of the material. However, before such aggregate can be considered safe for general use in concrete, longer-term concrete prism tests need to be carried out, which would cover the range of mixes in which the aggregate is likely to be used.

Method of Aggregate Production from Power Plant Ashes by Sintering in the Shaft Furnace: Economic Aspects

Solid waste management is a very important issue because of the increasing amount of different residues that have hazardous impacts on the human environment. Power generation is one of the biggest sources of various pollutants, fly ash being one. Damping of this material is limited due to the limited area that can be used by the power industry, and more effective and efficient methods must be developed to solve the problem of fly ash generated by power stations. The original technology of fly ash sintering to produce lightweight aggregate is presented. This technology provides a useful product and eliminates the need for discharge of fly ash into the environment. Selected components of the costs of aggregate production using this technology are described, and a cost comparison with other methods, such as Megran and Pollytag, has been performed.

Regional geologic environs and natural resources of Badia Sector, Jordan

This paper summarizes the information on the geology and natural resources of the Jordan Badia Research and Development Programme. The research focused on the issue of the environment in arid lands as an aid to provide practical options for sustainable development. This paper presents results of field studies in the following areas related to the sustainable development of the Safawi area in the northern Jordan Badia; geomorphology, including landform, soil, lands, processes and hazards, geology and physical resources and surface water hydrology. Tertiary-Quaternary continental basalt flows and tuffs cover approximately 11 000 km2, the majority of the Safawi area. In addition to extensive basalt lava flows, the programme area includes a variety of geological outcrops and potential sources of economic products that include the following: Tuff/Scoria, Zeolite/Olivine, Porcellanite, potential sources of aggregate/construction materials, ornamental stone, building stone, basalt for manufacturing of rock wool, and materials suitable for producing lightweight aggregate. The whole of the eastern Badia exhibits major fault systems, many of which were identified from Landsat TM images. The system of wadis which drains the Badia is extensive, with the general flow from the north to the south and south-west. A noticeable geomorphic surficial deposit occuring throughout much of the Badia is fine-grained, water-lain sediments that vary in size and character. The local designation for the fine sediment deposits is Qaa. An MSS scene for the area under consideration has been studied. Twelve major geomorphic subdivisions or zones can be identified. Individual land system units have been identified by traversing the programme area. Key sites have been visited based on Landsat TM image interpretation. To a large extent, key areas were subdivided after their initial identification on the Landsat scene and corroboration in the field. The surface drainage of the Badia region can be broadly divided into wadi systems, areas of distinct channelized flow, and Qaa, predominantly fine-grained sedimentary basins of low relief. Spatial variability in infiltration rates across the wadi-Qaa system were determined from field experiments. Infiltration rates were found to be medium-high in the wadi channels but decrease rapidly for the Qaa materials. Apparently runoff from wadi side slopes will be high, and water storage occurs along the wadi channels while ponding occurs in the Qaa areas.

Opencast coal mining: a unique opportunity for Clee Hill Quarry

Abstract Clee Hill Quarry is an active hardstone (dolerite) quarry located 5 miles to the east of Ludlow, Shropshire. The quarry is in Carboniferous Coal Measures which have been intruded by a thick ( c. 60m) conformable fine-grained olivine-dolerite sill. The whole sequence is now folded into a broad synclinal structure and is extensively faulted. The area is blanketed by glacial deposits, 2–12m thick. Historically, quarrying operations have been closely allied to the geological structure being confined to the margins of the syncline where the dolerite is devoid of overlying Coal Measures. In 1973 a programme was undertaken to assess the viability of using Coal Measures material for the production of lightweight aggregate. This programme was initiated because virtually all remaining, albeit substantial, planned reserves of dolerite were overlain by considerable thicknesses of Coal Measures and glacial deposits. While initial results from a technical viewpoint were encouraging, the project was abandoned for commercial reasons. The Coal Measures sequence overlying the dolerite sill comprises in excess of 30 m of mudstones, siltstones and sandstones as well as four recognized coal seams. Piecemeal mining of this coal had taken place on the Clee Hills for centuries, and in the area for future quarrying abundant evidence was available at surface of former bell-pit workings. In the early 1980s a decision was taken to evaluate the coal deposits at Clee Hill Quarry. The area for detailed assessment was defined using existing borehole data and evidence from old workings identified from site survey and aerial photographs. Exploration in two separate phases comprised the drilling of 44 open holes with spot coring and borehole geophysical logging. Coal quality was determined by analysing all relevant borehole core samples. Although coal reserve estimates assumed a high degree of past shallow mining activity, the economic viability of working the coal seams by opencast methods was established. In 1986 a planning application was submitted to Shropshire County Council to work and remove all coal overlying the dolerite, over a 3 year period. The proposal would allow exploitation of a valuable mineral asset, release substantial reserves of hardstone (dolerite) and allow restoration at an early date of large areas of former mining and quarrying dereliction. Planning permission was obtained in August 1988. Negotiations with the Opencast Executive of British Coal culminated in the granting of a licence to work both British Coal (vested) and ARC (alienated) coal. Coal mining was commenced in October 1988. Predictions of seam thickness and faulting were consistently accurate and vindicated the site investigation programme. In two aspects more detailed/accurate information would have been useful. Firstly, with regard to coal quality, borehole core samples did not accurately reflect in situ moisture content. Secondly, the extent of old workings in the upper coal seams was significantly overestimated. Neither aspect significantly affected the viability of the project. The mining phase including the major restoration works was completed in July 1992.

Reuse of Wastewater Sludge in Manufacturing Non-Conventional Construction Materals - An Innovative Approach to Ultimate Sludge Disposal

The increased requirements for the treatment of wastewater, coupled with industrial growth, have created a need to treat and dispose of an over-proportional sludge volume. At the same time increasingly stringent regulations have resulted in limitations on the ultimate sludge disposal options. In highly urbanized municipalities, scarcity of landfill sites and increasing environmental awareness pose major public concern on the disposal of sludge. This situation has prompted the interest in recycling and reuse of sludge into building and construction materials as means of alleviating sludge disposal problems. This paper presents the results of the use of wastewater sludge to produce lightweight aggregates and cementitious binder as non-conventional construction materials. Lightweight coarse aggregates were produced from the incineration of sludge-clay mixture. Test results of porosity, specific gravity, bulk density, ten percent fines, water absorption and concrete strength, indicate that clay-blended sludge could be used to produce lightweight aggregates. The feasibility of using dried sludge mixed with lime as a cementitious binder after incineration was also studied. Evaluation of the mortar cube strengths shows that it is possible to produce masonry binder from sludge that will satisfy the strength requirements in the ASTM standard for masonry cement.

Clay‐Blended Sludge as Lightweight Aggregate Concrete Material

Sludge disposal is a nuisance for municipal wastewater treatment plants. Increasingly stringent environmental control regulations have resulted in limitations on sludge disposal options, and hence there has been a resulting increase of interest in disposal by incineration. In this study the potential of using dewatered sludge mixed with clay as lightweight coarse aggregate after incineration was examined, and the properties of the aggregate as well as the resulting concrete were investigated. From the tests conducted on 10% fines, bulk density, specific gravity, porosity, water absorption, and compressive strength, it was found that clay-blended sludge could be used to produce lightweight aggregates.

マンガン団塊浸出残渣の軽量骨材化に関する基礎的研究

マンガン団塊浸出残渣の軽量骨材化に関する基礎的研究

Development of Light-Weight Aggregate Production Process from Coal Ash with a Shaft Kiln (Part 2)

Development of Light-Weight Aggregate Production Process from Coal Ash with a Shaft Kiln (Part 2)

Development of Light-Weight Aggregate Production Process from Coal Ash with a Shaft Kiln (Part 3)

One t/d test plant facilities of the shaft kiln for calcination of coal ash pellets is designed and constructed. Experimental studies are carried out with this test plant to examine the relationship between reactor behavior and product properties and to clarify the technical problems of the shaft kiln necessary to attain the stable operation. It is found that the most important factor is smooth movement of the pellets supllied from the top of the kiln. Steady and smooth discharge of the pellets could be achieved by applying a forced discharger like a ram feeder. The maximum temperature level of the moving bed in the shaft kiln is governed by not only operational conditions but green pellet composition such as carbon and moisture content. The position of the maximum temperature is affected by an air flow rate as well as discharge rate. The calcined pellets are tested according to JIS A 5002 (Light-weight concrete for structure) and Anouncement No. 13 of Environmental Agency (Industrial Waste Disposal Regulation) and tested properties satisfy the specification and regulation values. Especially, the compressive concrete strength shows 550kgf/cm2 which is about 40% stronger than that of JIS value. Conceptual design of a 50t/d pilot plant and cost estimation of the developed process are performed based on the studies conducted up to now. In case of a 1000t/d plant, production cost is estimated under 3000yen/m3.

Development of Light-Weight Aggregate Production Process from Coal Fly Ash with a Shaft Kiln

Development of Light-Weight Aggregate Production Process from Coal Fly Ash with a Shaft Kiln

The Production of Light Weight Aggregates from Municipal Refuses

The Production of Light Weight Aggregates from Municipal Refuses