Environmentally Friendly Pervious Concrete for Treating Deicer-Laden Stormwater: Phase II

In Phase I of this project, graphene oxide (GO)-modified pervious concrete was developed using coal fly ash as the sole binder. The primary objectives of Phase II of this project were (1) to evaluate the stormwater infiltration capacity of GO-modified fly ash pervious concrete; (2) to evaluate the durability performance of GO-modified fly ash pervious concrete using freeze/thaw and salt resistance testing methods; and (3) to use advanced analytical tools to fully characterize the GO-modified fly ash binder. Test results indicate different degrees of reduction in concentrations of possible pollutants in stormwater—copper, zinc, sulphate, chloride, ammonia, nitrate, and total phosphate. The incorporation of GO significantly improved the resistance of pervious concrete to freeze/thaw cycles and ambient-temperature salt attack. The specimens were examined using X-ray diffraction, which revealed that the mineralogy and the chemical composition of fly ash pastes differ considerably from those of cement pastes. Nuclear magnetic resonance was used to study the chemical structure and ordering of different hydrates, and provided enhanced understanding of the freeze/thaw and salt scaling resistance of fly ash pervious concrete and the role of GO

Development of methods for preparing fly ash for separation by activation

Purpose. Isolation of the aluminosilicate fraction from fly ash, study of physical and mechanical properties of binders obtained from TPP wastes. Methods. Ash, carbon concentrate (underburn), ash concentrate and products of their treatment with reagents were tested by optical methods. The morphology of the particles of the subjects of inquiry was studied with the scanning electron microscope REM-100. The composition of the ash phases was investigated using the X-ray diffractometer DRON-2. Findings. The technology of sorbents based on coal combustion products through a variety of methods was researched. It is shown that these sorbents are distinctive because their structure has non-localized pi-electrons of the graphite-like networks of crystallites of carbon. This circumstance determines not only the uniqueness of electro-physical properties of coal but also adsorption, redox, chemisorption processes on the border of coalslurry. The listed circumstances allow you to use the original methods of chemical and mechanochemical modification of the surface chemical and coal, due to introducing desired donor and acceptor atoms in carbon frame, which increases the absorption capacity and selectivity carbon sorbents. Practical implications. The article presents the results of receipt of binders based on TPP ash. It has been shown that a component of the fly ash is aluminosilicate spheres that can be used in the production of lightweight concrete. It is proved that the result of mechanochemical activation mixture consisting of alumino-silicates, resulting lightweight concrete has high strength 7-8 MPa, which allows, while maintaining the technical characteristics save from 20 to 30 % of binder. Concrete obtained based on aluminosilicate spheres separated from fly ash may be used to prepare the outer wall construction, small building blocks, as well as monolithic housing. In comparison with known compositions keramsit compositions comprising TPP waste

Environmentally Friendly Pervious Concrete for Treating Deicer-Laden Stormwater: Phase I

A graphene oxide-modified pervious concrete was developed by using low-reactivity, high-calcium fly ash as sole binder and chemical activators and other admixtures. The density, void ratio, mechanical strength, infiltration rate, Young’s modulus, freeze-deicer salt scaling, and degradation resistance of this pervious concrete were measured against three control groups. The test results indicate that graphene oxide modified fly ash pervious concrete is comparable to Portland cement pervious concrete. While the addition of 0.03% graphene oxide (by weight of fly ash) noticeably increased the compressive strength, split tensile strength, Young’s modulus, freeze-deicer salt scaling, and degradation resistance of fly ash pervious concrete, it reduced the void ratio and infiltration rate. The fly ash pervious concrete also showed unfavorable high initial loss during the freeze-deicer salt scaling test, which may be attributed to the low hydration degree of fly ash at early age. It is recommended that durability tests for fly ash concrete be performed at a later age

Feasilibilty of coal combustion by-products inertization for carbon capture and storage: the case for high-Ca fly ashes

High Calcium Fly Ashes are reactive materials that often do not meet the limits of the standards. Therefore, most of the quantity produced annually in the world, due to lignite burning, remains unexploited and charges the environment. Actually, a low percentage of the materials is absorbed at a permanent basis from the cement industry and huge amounts are rejected or used for reclamation of mining areas. However, investigation on these materials has shown which are the weak points and how they could be overcome by using advances in materials technology

Analysis and optimization of material flow inside the system of rotary coolers and intake pipeline via discrete element method modelling

There is hardly any industry that does not use transport, storage, and processing of particulate solids in its production process. In the past, all device designs were based on empirical relationships or the designer's experience. In the field of particulate solids, however, the discrete element method (DEM) has been increasingly used in recent years. This study shows how this simulation tool can be used in practice. More specifically, in dealing with operating problems with a rotary cooler which ensures the transport and cooling of the hot fly ash generated by combustion in fluidized bed boilers. For the given operating conditions, an analysis of the current cooling design was carried out, consisting of a non-standard intake pipeline, which divides and supplies the material to two rotary coolers. The study revealed shortcomings in both the pipeline design and the cooler design. The material was unevenly dispensed between the two coolers, which combined with the limited transport capacity of the coolers, led to overflowing and congestion of the whole system. Therefore, after visualization of the material flow and export of the necessary data using DEM design measures to mitigate these unwanted phenomena were carried out.Web of Science117art. no. 184

Correlation between microstructure, phase composition and mechanical properties of thermo-insulation bonding agents based on waste material

Konstrukcioni kompoziti - termo-izolaciona i/ili visoko-temperaturna veziva u kojima je leteći pepeo, kao potencijalno štetna materija za okolinu, kombinovan sa običnim i vatrostalnim cementom predstavlja jednu sasvim novu mogućnost za reaplikaciju ovog otpadnog materijala. U ovoj studiji, ispitivana su veziva spravljena na bazi dve vrste letećeg pepela dobijenog procesom sagorevanja uglja i dve vrste cementa - obični Portland cement i visoko-aluminatni cement. Promena u mineralnom sastavu kompozita uslovljena povećanjem temperature je analizirana pomoću XRD metode. Mikrostrukturne promene ispitivanih kompozita su utvrđene na osnovu rezultata skening-elektronske mikroskopije (SEM). Makro performanse - mehanička svojstva ispitivanih veziva su povezana sa promenama koje se dešavaju u mikrostrukturi materijala. Ispitivana veziva imaju odlične vrednosti pritisne čvrsoće, a SEM i XRD analiza je ukazala i na potencijalno dobra termo-izolaciona i vatrostalna svojstva ovih materijala.Building composites - thermo-insulating and/or high-temperature resistant bonding agents in which fly ash, as potentially environmentally harmful waste material, is combined with ordinary and refractory cement is new option for reapplication of this waste material. In this study, investigated bonding agents were based on two types of fly ashes from coal combustion process and cements - ordinary Portland cement and highaluminate cement. Change of mineral phase composition of the composites with increasing temperature was analyzed by means of XRD method. Microstructural changes within investigated composites were investigated by means of scanning electron microscopy (SEM). Macro-performance - mechanical properties of the investigated bonding agents was finally correlated with its microstructure. The investigated bonding agents showed excellent compressive strength, while SEM and XRD analysis indicated its valuable refractory and thermo-insulation properties

Thermal and Structural Characterization of Macro-Encapsulated Phase Change Material Integrated Into Concrete Cubes

High-energy consumption in buildings is a research issue of great importance today, with solid-liquid phase change materials (PCMs) proving an excellent candidate for passive means to reduce energy consumption. In the current research, a novel protective coating was developed from geopolymer to encapsulate a PCM to prevent leakage in the liquidous phase. The PCM was characterized using a customized temperature history method (THM) and standard differential scanning calorimetry (DSC). Two different porous materials, polyurethane foam and lightweight expanded clay aggregate (LECA), were selected to hold the PCM and act as a matrix in which to develop PCM capsules. Ingredients of the coating were characterized using X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Initially, liquid PCM was absorbed into foam and LECA by direct immersion and vacuum impregnation, respectively, until maximal absorption was achieved. A geopolymer coating was developed and applied to spherical foam and LECA matrices containing PCM at low temperatures to produce leak-proof PCM capsules, thus yielding geopolymer coated PCM capsules in matrix of foam (GP-F-PCM) and geopolymer coated PCM capsules in the matrix of LECA (GP-L-PCM). Efficacy of the produced capsules was tested by exposure to harsh outdoor conditions and application of rapid thermal cycles above and below the melting point of the PCM while leak proofing efficiency was examined using diffusion-ooze circle (DOC) test. Alkali-activated geopolymer concrete (GPC) cubes were developed to test thermal performance and compressive strength. Different compositions were developed for each matrix material (foam or LECA) and compared with a reference sample comprising a cube of GPC (i.e., six experimental samples in total, plus the reference). Samples of GPC were cast with 25%, 50% and 75% volume ratio replacement of their solid contents with either spheres of foam, LECA, or the same ratios of GP-F-PCM and GP-L-PCM capsules. Each composition was tested separately and heated until the achievement of steady-state temperature in a customized indoor set-up. Compression tests were performed after seven days and 28 days of curing. Thermal tests revealed that direct addition of foam into GPC increased the back-surface temperature. Increasing the amount of foam had increased the temperature and for the maximum case of 75% foam addition, this increment was 5.8ºC in comparison to the reference. Addition of GP-F-PCM, LECA, and GP-L-PCM had a positive effect on the temperature drop on the back surface of the cubes. For the best case, a temperature drop of 12.5 °C was obtained at the back surface of cube with 75% GP-F-PCM, with respect to the reference. In comparing the capsules of LECA and foam as the matrix, GP-F-PCM produced more pronounced results because of higher PCM absorption in foam. Heat transmission effect was validated measuring U-values of all the sample cubes. It was observed that U-value for the reference cube was 2.04 W/m2K, which increased to 2.072 W/m2K for 75% foam. The U-value decreased to the levels of 1.092 W/m2K, 1.6 W/m2K and 0.9 W/m2K for 75% GP-F-PCM, 75% LECA and 75% GPL- PCM respectively. In terms of compression strength, the addition of foam had slightly positive effect (+6.3%) but the addition of GP-F-PCM, LECA, and GP-LPCM reduced strength significantly. Compression strength was 9.9 MPa, 10.1 MPa and 10.9 MPa for 75% GP-F-PCM, 75% LECA and 75% GP-L-PCM, which can be attributed to the fragile PCM and weak LECA structure. However, thermally responsive geopolymer concrete is promising and suitable for the construction of building facades, partitioning walls and roofing membranes

The effects of physical and chemical properties of fly ash on the manufacture of geopolymer foam concretes

The development of sustainable construction and building materials with reduced environmental footprint in both manufacturing and operational phases of the material lifecycle is attracting increased interest in the housing and construction industry worldwide. Recent innovations have led to the development of geopolymer foam concretes (GFCs), which combine the performance benefits and operational energy savings achievable through the use of lightweight foam concrete, with the cradle-to-gate emissions reductions obtained through the use of a geopolymer binder derived from fly ash. Fly ash is a by–product of coal fired power stations, and has become a highly promising source material for geopolymer manufacture. Compared to clays, another type of usually used materials, fly ash is probably more technologically suitable as it requires less alkaline activator while providing good workability. However, fly ash particles are substantially heterogeneous in physical and chemical properties. The composition and mineralogy of fly ash have marked effects on the properties of geopolymers, such as setting behaviour. This will affect the pore structure of GFC. Unfortunately, there is very limited specification regarding feedstock utilisation in geopolymer manufacture at present. Understanding the effect of fly ash physics and chemistry on the manufacture of GFC is not only necessary for the development of commercially mature GFC technology but also important for the geopolymer technology as a whole section. Five fly ash samples sourced from different power plants around Australia were used to manufacture geopolymer binders, enabling investigation of the relationship between the physical and chemical properties of fly ash and the mechanical properties of geopolymer products. The results showed that fly ashes from different sources exhibit substantially different physical properties. One important property is the inter-particle volume of fly ash, which largely determines the liquid requirement. The liquid requirement furthermore affects the porosity of hardened binders and their production costs. Another factor is the reaction extent of fly ash, which determines the quantity and composition of gel phases. A general trend obtained is that fly ash with higher network-modifying cations seems to possess higher reactivity. Research by Rietveld quantitative XRD and XRF analysis found that the composition and chemistry of glassy phases play an equally important role as the quantity of these phases in affecting the reactivity of fly ash. In glassy phases, both FeO4 and AlO4 tend to randomly distribute and connect with SiO4 tetrahedra by sharing corners and this is due to the alkali/alkali earth cations, which act as charge compensators. A reactivity index (RI) was proposed in this thesis to quantify the reactivity of fly ash under geopolymerization conditions. If pentacoordinated Fe cations are regarded as network modifiers, in addition to alkali and alkali earth cations, and by considering the contribution of specific surface area, it was found that the RI order of the studied five ashes matched well with their reactivity order. Alkaline dissolution analysis under different liquid/solid ratios supported the RI results. Additionally, dissolution analysis also showed that the crystals such as mullite and quartz were also partially dissolved, particularly in the ‘impure’ fly ashes, which had relatively higher concentration of network modifying cations. The above stages of the works were very useful to understand and to obtain a strong geopolymer binder by selecting a reactive fly ash. However, GFC manufacture in the laboratory conditions showed that a fly ash suitable for making high strength solid geopolymers was not necessarily suitable for GFC manufacture. It appeared that fly ash physical properties played a more important role than fly ash chemistry in affecting the engineering performances of GFCs. Those fly ashes with lower particle density and irregular particle shape appeared best suited for the manufacture of foam geopolymers. For a foamed paste derived from a specific fly ash, quick setting was a key property to achieve fine pore size and a homogeneous microstructure. The orthogonal array study conducted showed that slag addition was an effective method to control, and shorten the setting time of the foamed paste. The pore structure and porosity were also changed significantly and contributed to an increase in compressive strength. Research of the characteristics of pore structure of a series of GFCs showed that the pore size distribution in GFC affected the compressive strength to a large extent, particularly for the large pores. Based on the statistical fitting and modelling, a new model was developed, called the ‘large void model’, which treated the porosity of critical size pores (>100 m) and total porosity separately. Two mathematical models relating the measured thermal conductivity with porosity and dry density were successfully developed. The mathematical models were proven to be able to predict the mechanical and thermal insulation properties precisely

Development and Characterization of Sustainable Geomaterial Using Mining and Industrial Wastes

The rapid growth of infrastructure needs a vast amount of natural resources to be used as an engineering material; on the other, industries and mining sectors are facing difficulty in managing their by-products. Hence, research needs in the alteration of the industrial wastes that can overcome the above challenges with minimum or no adverse effect on the geoenvironment, which especially can be termed as a sustainable material. In the present study attempts have been made to develop sustainable materials, (i) controlled low strength material (CLSM), (ii) biopolymer based cementitious material and (iii) alkali activated material (AAM) from industrial and mining wastes. The controlled low strength materials are developed using (i) less explored industrial waste ferrochrome slag (FS) and (ii) coal mine overburden with fly ash and cement as the binder for both the cases. Experimental investigations like flowability, bleeding, compressive strength, California bearing ratio (CBR), settlement, ultrasonic pulse velocity and slake durability index are made on developed CLSM. Use of optical microscope to characterise the granular material FS in terms of sphericity and workability of the material is another aspect of the present work. The developed CLSM material can be used for different structural fill works with “Low flowability, to “High flowability” with the bleeding value less than 3.5%, with water content varying from 25 to 32%. The 28 days’ density varies from 15.7 kN/m3 to 16.5 kN/m3 with ultrasonic pulse velocity values close to 2000, and the water absorption values less than 3%. The unconfined compressive strength (UCS) value upto 2.75 MPa and CBR value more than 100% was obtained. Biopolymer-based cementitious materials are made using (i) fly ash and (ii) fine fraction of coal mine overburden for wind and water erosion control using three types of biopolymers; xanthan gum (XG), guar gum (GG) and carboxyl methyl cellulose sodium (CMC) salt. The wind erodibility of the materials are studied using water retention, surface resistance and wind tunnel test, similarly pinhole test, cylindrical dispersion tests are conducted to know the water erosion resistance. For water erosion, the CMC is more effective followed by GG and XG for both shale and fly ash. The surface strength of CMC and XG treated shale and fly ash increased with increase in concentration of solution upto 2%, but optimum percentage of GG treated samples observed at 1%. Higher surface strength of CMC and GG showed better wind erosion resistance. The surface strength of biopolymer treated cohesive material shale is more than that of non-cohesive material fly ash, with the denser microstructure of treated samples due to the bonding of particles. The other sustainable material, alkali activated material using mine overburden and mine tailing is discussed in terms of compressive strength after 7 and 28 days of curing under ambient, alkali and sulphate solution to simulate different environmental conditions. Development of CLSM using AAM and use of slake durability index to assess the durability of developed sustainable material are some of the novelty of the present work. The AAM using mine overburdens are found to have 28 days compressive strength varying from 25.58MPa to 59.00 MPa depending upon the curing conditions and the base materials. The slake durability test indicates the developed AAM is “medium-high durable” to “high durable material”, similar to that of sandstone. The leachate analyses on the developed sustainable materials show no adverse effect on the geoenvironment. The scanning electron microscope (SEM), x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), electrical conductivity, zeta potential, etc. are also used for the characterization of basic material and the developed sustainable material to correlate with their macro properties. The present work will help in the possible utilisation of the developed sustainable material in infrastructure. But, the future challenges are (i) development of suitable machinery and equipment for implementation of CLSM process, (ii) pilot project study on the implementation of biopolymers for erosion control at the site and (iii) identification of cost-effective activators, possibly from industrial wastes