Calcined Diatomite Research Articles

Design, preparation, and performance of marine resource-based alkali-activated cementitious materials

The construction of islands and reefs and marine engineering cannot depend on cementitious materials, and how to utilize marine resources to prepare cementitious materials is the key to realizing the convenient construction of marine engineering. In this paper, starting from the necessary composition for the formation of gels, the effects of different activation methods on their activities were investigated by utilizing coral and diatomite as calcium and silicon sources, respectively. The study results show that using calcined coral to activate calcined diatomite resulted in a 28 days strength of up to 2.89 MPa, but it was not processable. The precursor with volcanic ash can be prepared by co-calcining coral and diatomite under lower temperature conditions, and its calcination temperature needs to be no less than 800 °C. In addition, characterization by XRD, FTIR, SEM and BET showed that increasing the calcination temperature helps to form more active substances with volcanic ash, such as CaO, CaSiO3, and Ca2SiO4, which can improve the compressive strength of alkali-activated materials prepared from them. The highest strength growth rate of 3.03 % and 28 days compressive strength of 10.80 MPa were obtained when the co-calcined temperature was 850 °C. The results of this study can provide some reference for the development of marine resource-based cementitious materials.

Geology, mineralogy, geochemistry and genesis of volcano-sedimentary hosted Lake Abiyata diatomite in central main Ethiopian Rift

The Abiyata Diatomite deposit is located in the Main Ethiopian Rift, which is characterized by strong extensional tectonics. The deposit is mostly made up of diatomaceous earth, which is a sedimentary rock made up of the fossilized remnants of diatoms, which are tiny algae. Diatomite's geological, geochemical, and mineralogical features, as well as its formation, are discussed in this research. To characterize diatomite from Abiyata, chemical, mineralogical, technological, and micro paleontological examinations were conducted on samples collected from outcrops and stream sections. The XRD characteristic peaks of diatomite demonstrate that it is primarily made up of Opal A silica, however certain crystalline phases were discovered in adequate amounts. Quartz and feldspar were the predominant crystalline phases, with lesser amounts of Calcite, Cristobalite, Illite, Mordinite, Wairakite, Halloysite, Clinoaptilolite, Adularia, and Tridymite. From SEM photomicrographs diatomites are primarily formed of benthic freshwater diatom species such as Staurosirella pinnata, Staurosira construens, Pseudostaurosira brevistriata, Epithemia Sorex and surirella pinnata. Diatom species, sedimentary profile sections and mineralogical data suggest that diatomite was deposited in lacustrine-type freshwater shallow lake environment. Chemical data obtained from 10 diatomite samples show that while silica is the bodybuilding material for diatomite. i.e., Silica (SiO2), 76.9 %; Alumina (Al2O3), 3.49 %; Sodium Oxide (Na2O), 1.52 %; Potassium Oxide (K2O), 1.107 %; Iron Oxide (Fe2O3), 1.1 %; Loss on ignition (LOI) 13.7 and other oxides are below 1 %. Studies from technological properties like physical tests, chemistry, and mineralogy and micropaleontology of Abiyata diatomite suggest that calcined diatomite can be used for waste treatment processes in the filter aid industry and as filler material.

Effect of aging on the mechanical properties of woven fabric-reinforced calcined diatomite substituted cement-based composites

The mechanical characteristics of polyester and flax woven fabric-reinforced, diatomite-substituted, cement-based composites have been examined at different ages within the scope of this study. The use of calcined diatomite in combination with a cement-based matrix aims to improve the mechanical performance within the composite as well as reduce carbon emissions. The consistency of cement-based and diatomite-substituted matrices with water-to-binder proportions of 0.28 and 0.45 was maintained at a fixed flow diameter of 235 mm with the adjusted use of a superplasticizer. The stress–strain graphs of the composites were obtained using an axial tensile testing machine and Linear Variable Differential Transformers (LVDT). The tensile strength, ductility, toughness development, and multi-crack performance of WFRC were obtained as a function of fabric type and aging. The effects of aging on tensile properties are discussed separately for each fabric type. Polyester woven fabric-reinforced composites were found to be superior to flax WFRC in terms of several mechanical properties at all ages. The substitution of diatomite further improved the tensile performance of the polyester woven fabric-reinforced composites. The fabric-matrix interface densification role of diatomite was determined by SEM/EDS line analysis. Evidence of a pozzolanic reaction between portlandite and diatomite was obtained through microstructure studies. Carbon emission analysis revealed that equivalent CO2 emissions could be reduced using diatomite in woven fabric reinforced composites. However, diatomite substitution caused a cost increasing effect.

Influence of Calcined Diatoms on the Properties of Conventional Concrete

Today, the construction industry has expressed its preference for the use of sustainable materials due to the significant impact they have on the environment. Although concrete is widely used in construction due to its diverse properties, one of its main components, known as clinker, is a major contributor to CO2 pollution. Therefore, the feasibility of partially replacing this material with alternatives is being investigated. Among them, calcined diatoms are presented as a promising option. These are an extremely fine and highly porous material, composed mainly of silica, which has a large specific surface area. The abundant presence of active silica improves the properties of concrete, such as its strength, while the ultrafine particles of diatoms densify the concrete structure, thus achieving a concrete with greater durability. The objective of this study was to evaluate the properties of conventional concrete, both fresh and hardened, by adding calcined diatomite in proportions of 5%, 10% and 15%, with the purpose of determining the optimum percentage of calcined diatomiteto achieve adequate concrete development. Test specimens were elaborated without the addition of calcined diatoms and with the addition of calcined diatoms, then immersed in water for 7d, 14d and 28d. Tests were carried out in the fresh state to obtain workability, bleeding, setting time, air content, temperature, and unit weight. In the hardened state, tests were carried out to obtain compressive strength, static modulus of elasticity and permeability. It was found that with a lower addition of calcined diatomaceous earth, the concrete can develop as a normal concrete, and improvements in compression were obtained, increasing with respect to the control concrete. However, by increasing the percentage of calcined diatomite, the workability is reduced and in general, the properties do not show an improvement. Concrete with the addition of calcined diatomite can be used as a thermal insulator, since it presents very fine particles that perform a filling effect, densifying the concrete matrix, and it can also be used for lightweight concrete since it reduces 17kg/m3. On the other hand, the compressive strength with 5% calcined diatomite increased by 9% with respect to the standard, due to its high pozzolanic activity.In addition, a lower permeability was found with the addition of 5% calcined diatomite. In general, calcined diatomite in lower proportions can generate resistant and durable concrete.

Hydrothermal modification of calcined diatomite with CaO: Effect of NaOH pretreatment

The development and application of high-adsorptive calcined diatomite (C-D) can provide a cost-effective solution for the filter aid industry, which remains a challenge in this field. Herein, an alkali (NaOH) pretreatment was introduced before the calcium oxide (CaO)-mediated hydrothermal activation of C-D. The adsorption performance of the alkali-modified samples (modified calcined diatomite: M-D) was significantly improved. The methylene blue trihydrate (MB) adsorption capacity of the optimal M-D sample reached 45.76 mg/g, which was 2.73 times higher than that of the sample prepared without the alkali treatment. The substantial enhancement in adsorption performance of M-D was mainly attributed to the abundant SiO32− species which was primarily generated during the NaOH pretreatment. SiO32− species are helpful for generating silicate substances with a larger specific surface area. By regulating the amount of NaOH, it was feasible to control the morphology/nanostructure and composition of the final materials. Well-developed flower-like nanoclusters was synthesized on the surface of C-D, resulting in higher specific surface area and adsorption capacity. This work paves the way to the value-added application of natural diatomite resources via providing an efficient modification method to optimize the properties of C-D.

A Novel Flux That Determines the Physico-Chemical Properties of Calcined Diatomite in Its Industrial Use as a Filler and Filter Aid: Thenardite (Na2SO4)

Diatomite needs to go through the flux-calcination process in order to increase its functionality in some specific applications such as filter aids. In this study, the effects of the thenardite, which was used for the first time as a flux in the calcination of diatomite, and widely used soda ash on the industrially important physico-chemical properties of diatomite were investigated. Samples taken from two diatomite deposits in the Aegean region of Turkey (Seydiler diatomite from Afyon and Sarayköy diatomite from Denizli) were used in this study. In raw and calcined diatomite samples, geochemical and mineralogical composition and parameters such as colour, grain size, morphology, specific surface area, permeability and wet cake density were characterized. It was found that thenardite was more effective than traditionally used soda ash in improving whiteness (L* = 98.20) and filtrate clarity (wet cake density = 0.378 g/cm3). However, higher permeability (k), i.e., higher filtration rate, was obtained in diatomite calcined with soda ash (k = 0.97 µm2). Fluxes had different effects on different diatomite species. The necessity of choosing flux type depending on the application area and the desired properties from diatomite was demonstrated.

Shear-thickening behavior of sustainable cement paste — Controlling physical parameters of new sources of supplementary cementitious materials

Cement is the main constituent of concrete and the world cement market represents more than 2 billion tons per year. However, the cement industry as a whole is the source of around 8% of global CO2footprint and therefore any reduction in the cement content can have a significant impact on reducing global CO2emissions. In terms of sustainability concept, Supplementary Cementitious Materials (SCMs) is one of the most common solutions given its great technical advantages for modern concrete, such as, rheological parameters adjustment, strength gain and full life durability, in addition to economical energy and low environmental impacts.In order to provide updated information for sustainable concrete design and preparation parallel with new sources of SCMs and on the other hand, the relationship between cement paste rheology and flow parameters of concrete. This present study investigates the shear thickening of sustainable cement paste (SCP) under control of some physical parameters of new sources of SCMs such as calcined diatomite (CD), calcined bentonite (CB) and silica fume (SF), respectively. Taking into consideration water-to-binder ratio (w/b) and high-range water-reducer (HRWR) based (PCE and PNS). It was observed that the shear thickening easily occurred when suspensions have a high anhydrous grains concentration, irregular shape, circular shape, high grains sizes (few tens of micrometers) and deflocculated grains state. Regardless of HRWR type and w/b ratios, flow index (n) of SCP substituted by CD is also larger than SCP with CB and SF with unvarying of SCMs level (10%). The intensity sequences of shear thickening of SCP under the influence of SCMs are CD, CB and SF, respectively.

Mechanical Properties of Vitrified Micro Bubbles Recycled Concrete Mixed with Calcined Diatomite

In order to prepare vitrified micro bubbles recycled concrete that meets the requirements of strength, the basic mechanical properties of recycled concrete with different vitrified micro bubbles were tested by adding calcined diatomite. The results show that: Calcined diatomite can fill the macroscopic cracks existing in the recycled coarse aggregate and effectively improve the performance of concrete and enhance the compressive strength of recycled concrete; With the increase of the amount of vitrified micro bubbles, the apparent density, compressive strength, splitting tensile strength and elastic modulus of recycled concrete all show a downward trend. When the amount of vitrified micro bubbles is 100% and the amount of calcined diatomite is 3%, the cubic compressive strength of recycled concrete can reach 32.36Mpa and the apparent density is only 1945kg/m3. Based on the experimental analysis, a linear relationship between cubic compressive strength fcu and axial compressive strength fc of vitrified micro bubbles recycled concrete is presented.

Influence of calcined diatomite content and elevated temperatures on the properties of high strength mortars produced with basalt sand

AbstractIn this paper, the effect of calcined diatomite (CDT) content on the mechanical, microstructural, and mineralogical properties of high strength mortars (HSMs) exposed to 25, 400, 600, 800, and 1,000°C temperatures is investigated. The percentages of CDT that replace Portland cement (PC) in this work are 0, 5, 10, 15, and 20%, by weight. The researched properties of the HSMs are the unit weight (Uw), ultrasonic pulse velocity (Upv), flexural strength (fs), compressive strength (fc) and the analyses of X‐ray powder diffraction, polarized light microscopy, and scanning electron microscopy/energy dispersive spectroscopy. The experimental results show that the CDT has a potential to be successfully employed as a partial replacement of PC in the HSMs exposed to elevated temperatures. The optimal replacement level of PC by CDT is determined as 15% from strength tests. Besides, the Uw, Upv, fs, and fc values progressively reduce as the temperatures subjected to the HSMs increase. The CDT has a positive effect on the fs and fc values the HSMs after exposure to elevated temperatures.

The structure and phase composition of nano-silicon as a function of calcination conditions of diatomaceous earth

The powder characteristics of nanostructured silicon produced via Magnesiothermic Reduction Reaction (MRR) of raw (amorphous) and calcined (crystalline) diatomite powders were studied. Magnesiothermic reduction reaction of diatomaceous earth samples was carried out in an argon-filled electric furnace at 700 °C for 2.5 h. Both X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) analysis of calcined diatomite powders confirmed the crystallization of opal to cristobalite and the preservation of the nano-scale morphology of natural diatomite after calcination at 1200 °C for 4 h. Raw and calcined diatomite after MRR contained product nanostructured silicon, unreacted silica, and by-product MgO. Silicon with nano-scale morphology was obtained after etching the reduced powder with 1.0 M HCl and 5% HF severally. Among the different grades of nanostructured Si produced via different routes, the one obtained from the diatomite powder calcined under argon flow showed nano-scale morphology identical to that of the precursor powder. X-ray diffraction analysis and Raman spectroscopy confirmed the prevalence of nanostructured silicon. All samples showed intense Raman signals with variations in peak positions confirming a difference in crystallinity between the silicon types. This work provides insights into the effects of different calcination conditions on the final structure of product silicon.

Growth of metastable phases during brick firing: Mineralogical and microtextural changes induced by the composition of the raw material and the presence of additives

This paper studies the mineralogical and textural changes that take place during the firing in an electric kiln at 800, 950 and 1100 °C of brick samples made with or without additives. Samples were made with a clayey raw material which was mixed with either halite or calcined diatomite sludge and then fired. These samples were then compared with control samples made without additives. Different analytical techniques (X-ray fluorescence, thermogravimetric and differential scanning calorimetric analyses, X-ray diffraction, polarized optical microscopy and scanning electron microscopy) were used to reconstruct the changes that took place inside the bricks from a mineralogical and textural point of view, changes that are similar to those that take place in nature during pyrometamorphism. The carbonates decomposed and reacted with silicates to form gehlenite, diopside and wollastonite; the plagioclase was enriched in calcium and the quartz concentration fell; the clay minerals favoured the melting of the matrix and the appearance of mullite, and K-feldspar changed from microcline to sanidine. The extent of vitrification increased in line with the increase in the firing temperature. When halite was added, new silicates appeared earlier at lower firing temperatures and molysite was formed, while the most important mineralogical difference in the bricks made with added calcined diatomite sludge was the presence of cristobalite, a component of the sludge. It is interesting to observe that the newly-formed phases contain certain chemical elements that are not normally found in their standard chemical composition.

Innovative polyetherimide and diatomite based composites: influence of the diatomite kind and treatment

In this work innovative composites were developed, using as polymeric matrix polyetherimide (PEI), a high performance thermoplastic, and as natural filler two different kinds of diatomaceous earth, i.e. uncalcined and calcined. The uncalcined powder was amino-functionalised to improve its chemical compatibility with the matrix, whereas the calcined one was submitted to a purification treatment with HCl to remove possible contaminants.Mechanical tests and microstructural characterisation were carried out to evaluate the influence of the filler kind, of its content (i.e. 1–10wt.%) and of its amino-functionalisation or purification in the case of uncalcined and calcined diatomite, respectively, on the composites performance. The collected results show an increase of Young's modulus with the filler content, particularly in the case of amino-functionalised diatomite, suggesting a good chemical compatibility between filler and matrix. This is substantiated by the scanning electron microscopy (SEM) observation of the fracture surface of samples after tensile test.

Separation of aflatoxin B1 from synthetic physiological fluids using talc and diatomite: Kinetic and isotherm aspects.

The objective of the study was to examine adsorption of the aflatoxin B1 from synthetic gastric fluid and synthetic intestinal fluid by talc, raw and calcined diatomite. The kinetic and equilibrium adsorption processes were studied in the batch adsorption experiments applying high performance liquid chromatography for the aflatoxin B1 determination. The kinetic study showed a very fast adsorption of the aflatoxin B1 onto the selected adsorbents from the both physiological fluids with reaching equilibrium within 1-15min. The aflatoxin B1 was almost completely adsorbed in initial linear step of the kinetic process that can be described well by the zero-order kinetics model. The experimental data of the equilibrium adsorption were characterized using the Langmuir and Freundlich isotherm models. The high adsorption effectiveness was found in a range of 90%-100% and 60%-100% for the diatomite samples and the talc respectively at the initial concentrations of the aflatoxin B1 as 31-300ng/mL. The possible mechanisms of the aflatoxin adsorption onto the used mineral adsorbents are also discussed in the work.

Absorbent materials in waterproofing barriers, analysis of the role of diatomaceous earth

This paper presents recent development in experimental assessment of the capillarity involving the effect of diatomaceous earth in water proofing barriers (1940s and 1950s solutions). The introduction of diatomite in hydraulic lime mortars as a waterproofing barrier was firstly reported in licensed architectural plans after 1945 in the central region of Portugal. This was the period of Modernist buildings, a recent heritage to preserve and widely disseminated worldwide, recognised as the 20th century heritage. A methodology was presented to test these types of solutions considering the calcined and not calcined diatomite. Experiments reveal that two aspects need to take into account: (1) the presence of not calcined diatomite tends to have a better behaviour in relation to calcined diatomite; (2) the type of diatomite—calcined or not calcined—has influence in the capacity of retaining water in the barrier, as well as the variation of volumetric dosage of the components.

Processing and characterization of diatom nanoparticles and microparticles as potential source of silicon for bone tissue engineering

Silicon plays an important role in bone formation and maintenance, improving osteoblast cell function and inducing mineralization. Often, bone deformation and long bone abnormalities have been associated with silica/silicon deficiency. Diatomite, a natural deposit of diatom skeleton, is a cheap and abundant source of biogenic silica. The aim of the present study is to validate the potential of diatom particles derived from diatom skeletons as silicon-donor materials for bone tissue engineering applications. Raw diatomite (RD) and calcined diatomite (CD) powders were purified by acid treatments, and diatom microparticles (MPs) and nanoparticles (NPs) were produced by fragmentation of purified diatoms under alkaline conditions. The influence of processing on the surface chemical composition of purified diatomites was evaluated by X-ray photoelectron spectroscopy (XPS). Diatoms NPs were also characterized in terms of morphology and size distribution by transmission electron microscopy (TEM) and Dynamic light scattering (DLS), while diatom MPs morphology was analyzed by scanning electron microscopy (SEM). Surface area and microporosity of the diatom particles were evaluated by nitrogen physisorption methods. Release of silicon ions from diatom-derived particles was demonstrated using inductively coupled plasma optical emission spectrometry (ICP/OES); furthermore, silicon release kinetic was found to be influenced by diatomite purification method and particle size. Diatom-derived microparticles (MPs) and nanoparticles (NPs) showed limited or no cytotoxic effect in vitro depending on the administration conditions.

Diatomite releases silica during spirit filtration

The purpose of this study was to ascertain whether diatomite is an inert filter aid during spirit filtration. Surely, any compound with a negative effect on the spirit composition or the consumer’s health could be dissolved. In this study different diatomites were treated with 36% vol. ethanol/water mixtures and the amounts and structures of the extracted compounds were determined. Furthermore, Brandy de Jerez was diatomite- and membrane-filtered at different temperatures and the silicon content was analysed. It was found that up to 0.36% by weight of diatomite dissolved in the aqueous ethanol and amorphous silica, in the form of hollow spherical microparticles, was the most abundant component. Silicon concentrations in Brandy de Jerez increased by up to 163.0% after contact with diatomite and these changes were more marked for calcined diatomite. In contrast, reductions of more than 30% in silicon concentrations were achieved after membrane filtration at low temperatures.

The Influence of Diatomite Types and Compatibilizer Content on Properties of Diatomite-Wood Flour/Polypropylene Composites

Based on diatomite as modifier, maleic anhydride grafted polypropylene as compatibilizer, wood flour as reinforcing material, through single screw extruder, diatomite based wood plastic composite was prepared. The results show that: compared with one-grade-diatomite (OGD) and two-grade-diatomite (TGD), mechanical properties of the composites prepared by calcined diatomite (CD) are better, tensile strength and impact strength reached 46.9MPa and 20.1MPa. With respect to the diatomite types, it is more significant for the effects of MAPP mass on the mechanical properties of composites. The amount of MAPP was controlled in 4%, the mechanical properties of composites are better. The study of rheological properties showed that, the flow property of composites produced by calcined diatomite is better; the interface of the composite components is closer and more superior processability.

Preparation and thermal energy storage properties of paraffin/calcined diatomite composites as form-stable phase change materials

A composite paraffin-based phase change material (PCM) was prepared by blending composite paraffin and calcined diatomite through the fusion adsorption method. In this study, raw diatomite was purified by thermal treatment in order to improve the adsorption capacity of diatomite, which acted as a carrier material to prepare shape-stabilized PCMs. Two forms of paraffin (paraffin waxes and liquid paraffin) with different melting points were blended together by the fusion method, and the optimum mixed proportion with a suitable phase-transition temperature was obtained through differential scanning calorimetry (DSC) analysis. Then the prepared composite paraffin was adsorbed in calcined diatomite. The prepared paraffin/calcined diatomite composites were characterized by the scanning electron microscope (SEM) and Fourier transformation infrared (FT-IR) analysis techniques. Thermal energy storage properties of the composite PCMs were determined by DSC method. DSC results showed that there was an optimum adsorption ratio between composite paraffin and calcined diatomite and the phase-transition temperature and the latent heat of the composite PCMs were 33.04°C and 89.54J/g, respectively. Thermal cycling test of composite PCMs showed that the prepared material is thermally reliable and chemically stable. The obtained paraffin/calcined diatomite composites have proper latent heat and melting temperatures, and show practical significance and good potential application value.

Environmental and depositional characteristics of diatomite deposit, Alayunt Neogene Basin (Kutahya), West Anatolia, Turkey

This paper describes the geological-depositional and environmental characteristics of diatomite. The diatomite deposit is situated in the southern part of the Alayunt (Kutahya) Basin. Samples of 18 diatomites and 12 host rocks were collected from four sedimentary profiles in the spring season. Basement rocks are Paleozoic-aged metamorphic rocks (schist, phyllite, quartzite, etc.) and Mesozoic-aged ophiolitic and complex rocks. Host rocks are rhyodacitic–rhyolitic tuffite, volcanic glass. Diatomite is composed of Upper Miocene–Upper Pliocene-aged diatom species. Diatomite shows layer morphology and lies on volcanic glass layer. XRD characteristic peaks of diatomite show that it comprises dominantly of Opal-A silica, whereas volcanic glass has Opal-CT constituent. SEM and NPM photomicrographs indicate that diatomites are dominantly composed of benthic freshwater diatom species, such as Pinnularia microstauron, Pinnularia lundii, Pinnulariasubrostrata, Pinnularia brevicostata, Pinnularia tenuis, Pinnularia sp., Navicula eligensis, Fragilaria construens, Mastogloia braunii Grunow, Melosira varians Agardh, Surirellacapronii Brebisson, Cymbella lanceoloata, Amphora venata, Gomphonema germainii, Gomphonema angustatum and Rhapalodia gibba. These species are general indicators of shallow paleolake environment and cool climate conditions. Due to the fluvial currents and climatic conditions; lake water levels, temperature and nutrient content fluctuated through the time. Chemical data obtained from 18 diatomite samples show that while silica is the bodybuilding material for diatomite (over 89 % SiO2), Al, Mg and Fe contents of diatomite samples might be derived from clastic materials. The concentration of Al, Mg and Fe decreases toward the lake center. Diatom genera, sedimentary profile sections and mineralogic data suggest that diatomite deposited in lacustrine-type freshwater shallow lake is associated with Upper Miocene-aged extension tectonics. Physical and filtration tests along with environmental characteristics of diatomite suggest that calcined diatomite can be used for waste treatment processes in the filter aid industry.

The use of raw and calcined diatomite in cement production

In this research, the use of raw and calcined diatomite which is in amorphous and porous nature was investigated in cement production . The physical, chemical, mineralogical, micro-structural and mechanical tests of the mortars, prepared by mixing Portland cement clinkers with 5%, 10% and 20% raw and calcined diatomite (w/w) and gypsum were carried out. According to the test results, raw diatomite blended cements have produced comparable strength values with respect to the reference cement (OPC) up to 10% addition; increased additions resulted in decreases in the strength due to the higher water demand related to the porosity while Blaine values and reactive SiO 2 content were increased. Calcination changed the porous structure of diatomite and eased the grindability as well as providing it to be used as a cement addition at a higher rate of 20%.