Properties Of Lightweight Aggregate Research Articles

Effect of microwave radiation temperature and content of different solid waste on the microstructure and physicomechanical properties of lightweight aggregates

Microwave radiation in the production of lightweight aggregates, it has not yet been thoroughly explored. Therefore, the main goal of the research is to analyze the possibility of using various types of waste, such as waste rock (0–30 %) and glass cullet (10 %), fly ash (50–80 %) and waste solution using different microwave temperature (1000, 1050, 1100 °C) in order to obtain lightweight aggregates. Above factors and, chemical and mineral composition of the waste materials, affect the microstructure and physico-mechanical parameters of the aggregates.). The thermophysical behavior (DTG/TG), grain composition, chemical composition (XRF), phase composition (XRD) and microstructure (SEM, μ-CT) were analyzed. The microstructure, as well as the related characteristics of aggregates, i.e. water absorption, density, and compressive strength, depend on the sintering temperature, chemical composition and mineral waste raw material. The best properties were obtained for a raw material mixture containing 80 % coal fly ash, 10 % glass cullet, 10 % clay and 48 g of the waste solution (per 100 g of raw mixture), sintered in the microwave at 1100 °C. The aggregates were characterized by water absorption of 6.96 %, bulk of 1.70 g/cm3, loose bulk density 0.60 g/cm3, and compressive strength 5.95 MPa. Closed porosity determined by micro-CT was 8.41 %, open - 0.24 %, sphericity 0.62. The total porosity depends on the loose bulk density and particle density of lightweight aggregates.Furthermore, washout tests meet environmental requirements. The proposed technology, moreover, enables a short time of thermal processing of raw materials, and thus energy savings and a sustainable approach to the production of green pellets. Thanks to the high strength, the obtained aggregates can replace commercial aggregates.

Environmental and geotechnical properties of lightweight aggregates made of reused solid wastes

This paper presents the environmental and geotechnical characterisation of new synthetic lightweight aggregates (SLAs) composed of reused biomass fly ash and waste plastics, namely high-density and low-density polyethylene (HDPE and LDPE), with a 50:50 fly ash-to-plastic ratio by weight. One-dimensional compressibility, creep properties, compaction features and stress-strain-strength behavior of SLAs were evaluated together with hydraulic conductivity and water absorbability. The fly ash–HDPE aggregate was found to be less compressible upon loading than the companion material made of fly ash and LDPE and similar to traditional natural lightweight expanded clay aggregate. The values of creep coefficient (C αε) were slightly higher than those expected for dense sands, but comparable, or even lower, than those measured for other recycled materials. Peak friction angle (ϕ′) and cohesion intercept (c′), determined by triaxial compression tests, were in the ranges 42.3–46.3° and 1.3–8.6 kPa, respectively with the highest values concerning the fly ash–HDPE aggregate. The hydraulic conductivity (k) was around 3 × 10−4–4 × 10−4 m/s, highlighting favorable permeability properties of both aggregates. Leaching tests and thermal stability analyses proved the sustainability of both aggregates from an environmental point of view. The results obtained in the present study demonstrate the suitability of the investigated aggregates for many geotechnical applications.

Experimental Investigation on Mechanical Properties of Lightweight Aggregate Concrete

Abstract This present research work mainly focusses on an investigation of the workability and strength properties of lightweight aggregates, particularly Palm oil shell and pumice aggregate, used in the production of concrete with (PA) and (POS), which were substituted for conventional Hard Broken Stone (HBG) coarse aggregate. Through the use of lightweight aggregate (POS and PA) in place of some of the coarse aggregate, the properties of a lightweight concrete M30 have been concentrated in this experimental study. The lab tests that were conducted include the compaction factor test, Schmidt Hammer test (rebound hammer test), and compressive strength. A total of 108 numbers of cube specimen were employed of size 2400 kg/m3. As part of a parametric study, the total number of cube specimens was divided into two groups according to various percentages: palm oil shell and pumice aggregate. In order to cast the cube specimens, dry weight of coarse aggregate was substituted for 0, 10 %, 20 %, 30 %, 40 %, and 50 % of POS and PA lightweight aggregate, respectively. A total of 9 cube specimens were cast and tested for 3, 7, and 28 days after successful curing in order to obtain accurate results. Average values were obtained from the test program and are shown in the corresponding Tables. Slump, compaction factor, rebound hammer compressive strength, and compressive strength values with different amounts of light aggregate were used to assess how well concrete performed when coarse aggregate was partially replaced with light aggregate. The test findings revealed that when the amount of conventional aggregates substituted by POS and PA increased, the slump test, compaction factor test, and strength of the lightweight aggregate concrete (LWAC) rapidly diminished. With an increase in the amount of aggregates replaced by POS and PA, the LWAC’s absorption has gradually increased as water. It is stated at the outset that the POS has shown to perform better than the PA when construction is done using structural lightweight concrete.

Enhancing the properties of lightweight aggregates using volcanic rock additive materials

The aim of the research was to investigate the applicability of different volcanic rocks as additives materials in lightweight aggregates (LWA) production. This study explains how the high amorphous content can improve the bloating properties of expandable clays and the properties of the LWAs produced. Ten different expandable clays, suitable for lightweight aggregate production, were collected and tested from clay deposits in Egypt and Hungary. Perlite and rhyolite tuff were used as volcanic rock aggregates. The composition of the samples was investigated by X-ray fluorescence spectroscopy (XRF) and X-ray powder diffraction (XRD, Rietveld method), while their expandability was characterized by heating microscopy (HM). The ideal amount of volcanic rock additives (10 wt%) and the required firing temperatures (1225 °C for the Hungarian clays and 1275 °C for the Egyptian clays) were determined and the LWAs were then produced. The LWAs produced (by hand rolling) by mixing of 90 wt% of expandable clay with 10 wt% of the additive materials (10 wt% perlite or 10 wt% rhyolite tuff) as green pellets then fired for different temperature. The LWAs made by mixing 10 wt% perlite or 10 wt% rhyolite tuff were characterized by their density, compressive strength, mineral composition, and pore structure. All samples had a density of less than 1.2 g/cm3, so they can be used as LWA. The results show that the additives helped some clay samples produce LWA with higher strength but lower density than the reference sample which was used, enabling the construction of lighter but stronger structures. Compositional analysis of the LWAs showed that there is a strong correlation between the amorphous content of the samples and their density, with higher amorphous content resulting in lower density.

Engineering properties and pore structure of lightweight aggregates produced from off-spec fly ash

• High- and low-calcium off-spec fly ash based lightweight aggregate (LWA) was produced. • Engineering properties and pore structure of LWA was characterized. • Small dose of NaOH as fluxing agent can result in off-spec fly ash based LWA with desired engineering properties. This study characterizes the engineering properties of lightweight aggregate (LWA) manufactured from low calcium (F-FA) and high calcium (C-FA) waste fly ash that were designed using a previously-developed thermodynamics-guided process. LWA properties that were characterized include specific gravity, vacuum water absorption, water absorption over time, water desorption, porosity, pore size distribution, and permeability. The LWA studied had a low oven dry specific gravity ranging from 1.22 to 1.45. The vacuum absorption and total open porosity of F-FA LWA decreased as the fluxing agent (NaOH) concentration increased while the values for C-FA LWA varied with increasing amounts of fluxing agent. All LWA passed the ASTM C1761 water absorption/desorption requirements for application to the internal curing of concrete. X-ray computed tomography (XCT) and dynamic vapor sorption analyzer (DVSA) techniques were used to characterize the LWA pore structure. It was found that for F-FA LWA the normalized porosity, counting only pores smaller than 50 nm (gelpores + mesopores), ranged from 4 % to 11.5 %, while for C-FA LWA, this same pore size range had porosity ranging from 1.7 % to 2.8 %. Pore size distribution measurements of F-FA LWA using XCT showed that the pores became larger and the predicted permeability coefficient increased as the fluxing agent concentration increased. For C-FA LWA, the predicted permeability increased with increasing NaOH concentration. Since the pore size distribution had greater variability and did not follow a specific increasing trend, the increase in C-FA permeability could only be due to an increase in pore connectivity.

Comparative study on strength aspects of lightweight concrete by replacing fine aggregate with vermiculite and cement with metakaolin and fly ash

Despite the advantages of using lightweight concrete, its use as a structural elements is relatively small compared to conventional concrete. The density and properties of lightweight aggregates using expanded vermiculite as an alternative to natural river sand in building materials development would improve lightweight concretes. Therefore, the objective of this study is to investigate the strength properties of lightweight concrete M30 with fly ash, metakaolin and vermiculite with natural sand as a partial replacement for cement. In this study, a total of eighteen different concrete mixes were prepared with the replacement of cement with 20% fly ash and fine aggregate with vermiculite proportions from 0 to 25% in 5% increments, and another concrete mix was prepared with the replacement of cement with 10% metakaolin and fine aggregates with vermiculite fractions from 0 to 25% with the addition of 5%. The results were compared with a concrete mix without cement and at various ratios of vermiculite as a replacement for fine aggregate. 54 cubes of dimension 100 mm x 100 mm x 100 mm was cured for 28 days to determine the compressive strength; 54 prisms of dimension 100 mm x 100 mm x 500 mm was cured for 28 days to find flexural strength; and 54 cylinders of 100 mm diameter and height 300 mm was cured for 28 days to determine split tensile strength, all tests were conducted as per applicable Indian standards.

Assessment of the mineral phase and properties of clay-Ca bentonite lightweight aggregates

This study deals with improving the properties of lightweight aggregate by the addition of Ca-bentonite mineral to expandable clays. The addition of bentonite can result in advanced lightweight aggregate materials which meet international standards. Besides bentonite material, twelve different clays (from Egyptian and Hungarian mines) were studied by X-ray fluorescence (XRF), X-ray powder diffraction (XRD, Rietveld method), and a heating microscope (HM). Aggregates were produced and their physical and mechanical properties were measured. The structure and the chemical composition of the clay-Ca bentonite aggregates were studied by scanning electron microscope (SEM) and with energy dispersive spectroscopy (EDAX). The results showed that the addition of 10 wt% bentonite can reduce the bulk density by up to 20%, can increase the compressive strength by up to 180%, and can increase the height of expansion by up to 68% in some samples. It was found that the high kaolinite content of the clay samples was not beneficial for expanding and decreasing the bulk density of aggregates. According to the Rietveld method from XRD and a statistical correlation model shown, the amorphous contents have a reciprocal relationship with the bulk density and a direct relationship with the height expansion. Bentonite, as a natural additive, to some clays, was suitable for producing lightweight aggregates with far better properties, as well as a more economical means of production.

The Properties of Lightweight Aggregates Pre-Coated with Cement Pastes and Their Suitability for Concrete.

One of the biggest technological problems connected with the production of lightweight concretes made of porous aggregates is their much higher water absorption, which may cause on the one hand workability loss, and on the other hand excess water content in concrete. The aim of this research was to assess the effect of impregnation of lightweight aggregates (LWAs) with cement paste on their properties and to verify its effectiveness in concretes. Three types of lightweight aggregates differing in porosity and pore structure (sintered fly ash Lytag, expanded clay: Leca and Liapor) were selected for the tests. The following parameters were taken into consideration in the research program: LWA type and size, LWA initial moisture content, strength, and rheology of cement pastes. The tests of 22 different aggregates, plain and coated with cement paste, included density, crushing strength, and development of water absorption in time. The research program proved that porous aggregates, due to their impregnation with cement pastes, may be effectively sealed and strengthened. All tested LWAs showed a considerable decrease in water absorption by up to 71%. However, only Lytag aggregate showed a visibly enhanced crushing strength. Verification of effectiveness of aggregate sealing on the enhancement of concrete properties showed both a considerable reduction in water absorption of composites (by up to 52%) and a very high increase in their strength (by up to 107%).

Effect of additives on properties and microstructure of lightweight aggregates produced from MSWI bottom ash sludge

ABSTRACT In order to solve problems of land occupation and environment damage resulted from massive municipal solid waste incineration bottom ash sludge (MSWI-BAS), sintered lightweight aggregates (LWA) were prepared from MSWI-BAS. Additives are of great significance for the preparation of high-performance LWA and the utilization of MSWI-BAS resources, so their effect on properties of LWA was investigated. The results showed that when the content of water glass was 20%, compressive strength of LWA reached a maximum of 8.4 MPa, and 1-hr water absorption reached a minimum of 5%. The reason was that the addition of water glass brought a lot of Na+ and Si(OH)4, and the internal crystals of water glass were converted into rod-shaped zeolite crystals, thereby forming a high-density structure. The addition of coal powder led to the formation of gas in LWA, thus reducing the density of LWA. At the same time, it was also conducive to earlier generation of liquid phase in LWA, making its internal structure dense. When the content of coal powder was 5%, 15%, and 20%, the modification effect was better, and compressive strength of LWA was larger, about 4 MPa. Additives are of great significance for the preparation of high-performance LWA and the utilization of MSWI-BAS resources. Implications: In this study, we have prepared LWA with MSWI-BAS. At the same time of X-ray diffractometer (XRD) and FT-IR analysis of raw materials, we also investigated effect of water glass and coal powder on characteristics (particle density, 1-hr water absorption, and compressive strength) of lightweight aggregates, and good results were obtained. For explanations, several characterizations were carried out, such as XRD and SEM. The sludge disposal problem is reduced. It opens up a new way for the utilization of solid waste resources. In addition, it meets with the concept of green development of building materials and makes the production of LWA have a broader development prospect.

EFFECT OF NANOSILICA ON THE STRENGTH OF CONCRETE WITH VOLCANIC PUMICE AS COARSE AGGREGATES

The use of concrete with volcanic pumice as aggregate is limited to masonry. The main reason for its limited utilization is that when volcanic pumice is used as a coarse aggregate in concrete, the result leads to poor performance. Such poor performance is attributed to the weak mechanical properties of volcanic pumice. Past research works show that the use of a stronger mortar counteracts the poor mechanical properties of lightweight aggregate. In this study, the mortar phase of Volcanic Pumice Concrete (VPC) was improvedthrough the incorporation of amorphous nanosilica synthesized from rice hull ash. Nanosilica was admixed in VPC at a concentration of 0.5% by weight of cement. Cylindrical test specimens were prepared, cured for 7, 14, and 28 days, and subjected to compressive and splitting tensile strength tests. Test results show that VPC specimens with 0.5% nanosilica have higher compressive and splitting tensile strength for all cases of 7, 14, and 28 days curing time compared to specimens without nanosilica. The highest percentage increase in compressive and splitting tensile strength was observed in specimens cured for seven days.

Strength, Drying Shrinkage, and Carbonation Characteristic of Amorphous Metallic Fiber-Reinforced Mortar with Artificial Lightweight Aggregate.

This paper investigates the strength, drying shrinkage, and carbonation characteristic of amorphous metallic fiber-reinforced mortar with natural and artificial lightweight aggregates. The use of artificial lightweight aggregates has the advantage of reducing the unit weight of the mortar or concrete, but there is a concern that mechanical properties of concrete such as compressive strength and tensile strength may deteriorate due to the porous properties of lightweight aggregates. In order to improve the mechanical properties of lightweight aggregate mortar, we added 0, 10, 20, and 30 kg/m3 of amorphous metallic fibers to the samples with lightweight aggregate; the same amount of fiber was applied to the samples with natural aggregate for comparison. According to this investigation, the flow of mortar decreased as the amount of amorphous metallic fiber increased, regardless of the aggregate type. The compressive strength of lightweight aggregate mortar with 10 kg/m3 amorphous metallic fiber was similar to that of the LAF0 sample without amorphous metallic fiber after 14 days. In addition, the flexural strength of the samples increased as the amount of amorphous metallic fiber increased. The highest 28-d flexural strength was obtained as approximately 9.28 MPa in the LAF3 sample, which contained 30 kg/m3 amorphous metallic fiber. The drying shrinkage of the samples with amorphous metallic fiber was smaller than that of the sample without amorphous metallic fiber.

Effects of CaO and MgO contents on the properties of lightweight aggregate produced from municipal solid wastes

Sewage sludge (SS) and river sediment (RS) could be used as the raw material for the production of lightweight aggregate (LWA). CaO and MgO are present as the major inorganic oxides in SS and RS, little is known about their influences on the performance of LWA. This study aims to explore the effects of CaO and MgO contents on the properties of LWA. The results indicated that LWA with desired physicochemical quality were obtained with a CaO content range of 3–4% and a MgO range of 2–3%. Anorthite (CaAl2Si2O8), spinel (MgAl2O4) and enstatite (Mg2Si2O6) detected in crystal phase were conducive to enhancing the hardness of LWA. The presences of Ca2+ and Mg2+ contributed to stabilizing the crystal network structure and improving the strength of lightweight aggregate. Nevertheless, excess amount of CaO and MgO, which functioned as crystal network-modifier, were unfavorable to the production of high-strength lightweight aggregate.

Evaluating the effects of nanosilica on the material properties of lightweight and ultra-lightweight concrete using image-based approaches

This work is aimed at characterizing the effects of nanosilica (NS) on the properties of lightweight aggregate concretes with different densities. Lightweight aggregate concrete (LWAC) and ultra-lightweight aggregate concrete (ULWAC) with targeted oven-dry densities of 850 kg/m3 and 450 kg/m3, respectively, were produced. The mixtures were modified by replacing cement with nanosilica, in concentrations of 1, 2, 5 and 10 wt-%. For comparison purposes, control specimens containing either cement alone or cement with silica fume (SF) were also produced. Their mechanical properties, including flexural and compressive strengths and transport characteristics, were evaluated by measuring the water accessible porosity and water absorption coefficients of the concretes. In addition, the thermal conductivity and drying shrinkage, being important parameters of lightweight concrete, were characterized. The pore structure characteristics of the concretes were assessed using 2D and 3D image analysis techniques; namely, using an automated air void analyser and micro-computed tomography (micro-CT), respectively. The experimental results show that NS has a significant effect on improving the mechanical and transport properties of lightweight concretes and that the efficiency of NS is much higher than that of SF. Moreover, depending on dosage, NS was found to have a negligible or decreasing influence on the drying shrinkage of concrete, after 28 days of curing. Microstructural studies confirmed that NS significantly affects the pore characteristics of concretes, thus resulting in concretes with denser and stronger microstructures.

Formulation and characterization of geopolymer and conventional lightweight green concrete by incorporating synthetic lightweight aggregate

The present work was designed to develop green lightweight aggregates (LWA) using; coal fly ash, granulated blast furnace slag and small amount of cement (10–20%). Two types of lightweight concrete (LWC) were formulated using developed synthetic LWAs i.e. (i) geopolymer (GC), and (ii) Portland cement concrete (PC). Physical and mechanical properties of both LWAs and LWCs were examined for their suitability to produce LWC. Test results indicated that, density of LWA was increased and water absorption value was decreased with higher cement percentage in the developed pellet, which were complying with the ASTM requirements for LWA. Mechanical strength of produced LWAs was approximately 50% of the natural coarse aggregate. Considering LWC results, the density of LWCs was less than the threshold value (<2000 kg/m3). The compressive strength, ultrasonic pulse velocity and split tensile strength of GC were higher than PC and they were more for concretes containing LWA with higher cement percentage. Experimental strength was also compared with predicted strength from different empirical models. Overall, the properties of LWA and resulting LWC were appropriately acceptable and can offer sustainable solution to the construction industry, especially for green concrete.

Spent Coffee Grounds in the Production of Lightweight Clay Ceramic Aggregates in View of Urban and Agricultural Sustainable Development.

This paper presents an innovative application for spent coffee grounds (SCGs) used as filler for the formulation of lightweight clay ceramic aggregates (LWA). LWA can be used for urban and agricultural purposes as a sustainable solution. Spent coffee grounds were tested as a pore forming agent partially acting as a replacement for red clay in material formulation before firing. Substitutions of 10, 15, and 20 wt.% of red clay were tested. The properties of lightweight aggregates with 15 wt.% of SCGs were improved using a specifically tailored fertilizer glass due to its low pH and conductivity within the soil tolerance range. Packaging glassy sand, cattle-bone flour ash, and potassium carbonate were mixed and melted in order to obtain this glass, which when added to the clayey batch functionalized the aggregates by phosphorus and potassium nutrients. The results (in particular, porosity and bulk density) show that the lightweight aggregates obtained have interesting properties for possible uses both in urban (e.g., green roofs as a drainage layer) and agricultural purposes. Moreover, pH and conductivity are in line with the Italian Standard regarding soil amendment (D.lgs. 75/2010). In addition, several leaching tests were performed in a solution containing 2 vol.% citric acid (C6H8O7) to evaluate the release capacity not only of nutrients (P and K) but also to check the presence and release of heavy metals, such as lead (Pb), that may come from the glassy precursor. The results obtained showed that nutrients are efficiently released in 21 days (P = 87.73% and K = 25.74% of released percentage) and Pb release is under the standard threshold of 30 ppm.

Mechanical properties of lightweight aggregate concrete at high temperature

Mechanical properties of lightweight aggregate concrete at high temperature

The properties of fly ash derived lightweight aggregates obtained using microwave radiation

This study evaluates the impact of a fly ash chemical composition, beidellitic clay addition and microwave heating time on the properties of lightweight aggregates. F class fly ash and fly ash with high carbon content (38%) were used. A waste solution after zeolite synthesis was used as an agglomerating agent. The analyzes showed differences in the chemical composition, mineral composition, microstructure as well as in physical and mechanical properties of produced aggregates. The presence of carbon in high-carbon fly ash caused an increase in the porosity of aggregates which resulted in lower dry particle density (1.92–2.35 g/cm3), apparent particle density (0.63–0.95 g/cm3), and higher water absorption (12–18%), and lower compressive strength in comparison to the aggregates obtained on the basis of class F fly ash. Longer microwave heating time resulted in higher compressive strength.

Reutilization of dredged harbor sediment and steel slag by sintering as lightweight aggregate

The purpose of this study was to evaluate the feasibility of lightweight aggregate (LWA) made from dredged harbor sediment and basic oxygen furnace (BOF) slag to increase their reutilization. The effects of preheating, sintering and raw materials proportion on the properties of LWA were discussed in term of particle density, water absorption, and compressive strength. Microscopic structure, water-soluble chloride and heavy metals leachability of the LWA were also examined. Results showed that the mixture of the dredged harbor sediment and BOF slag under the manufacturing process with preheating temperature at 500 °C for 10 min and sintering temperature at 1175 °C for 15 min was conducive to be a low water absorption and high strength LWA, which had as low as 1.73 g cm−3 and 3.45% for dry particle density and water absorption respectively. Its compressive strength reached 23.2 MPa when the addition of BOF slag was up to 27%. The LWA prepared in this study also have very low water-soluble chloride and heavy metals leachability, all compliant with Taiwan regulatory standards, thus would be suitable for further civil engineering application. The results of this study provide useful information on co-treating of wastes and recycled resources as LWA.

Experimental Analysis of Light Weight Concrete

Background/Objectives: Lightweight concrete is widely accepted due to its low density. LECA is an artificial lightweight aggregate made of clay having very low specific gravity. It is possible to develop lightweight concrete using LECA with a dry density of 1200 kg/m3 up to 1450 kg/m3. The significance of lightweight concrete is reduced mass and improved thermal and sound insulation properties hile maintaining adequate strength. These properties of lightweight concrete depend on the properties of lightweight aggregate (LECA). For developing lightweight concrete of required strength and properties the different engineering properties of LECA has to be studied. Methods/Statistical analysis: The different special properties mentioned for LECA lightweight concrete opens a wide applicability in the concrete industry and in structural members. For acceptance of concrete as structural concrete, it must possess sufficient resistance to repeated loading (cycling loading) which is predominant during the earthquake. The concrete cubes are casted with the nominal mix, 10%, 20%, 30%, 40% and 50% replacement of coarse aggregate by LECA and the acceptable characteristic strength attaining for the mix is calculated and the slabs are casted with the respective mix. Findings: The cyclic loading can be stimulated in the laboratory using a loading frame and hydraulic jack with sufficient setup. Using such a setup the cyclic behavior of lightweight concrete slabs as well as control composite slabs can be studied. These test results can be used to suggest methods to develop structural lightweight concrete with desirable properties.

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