Cement Asbestos Research Articles

Characterisation of asbestos-containing wastes by thermal analysis

The study examined building materials containing asbestos, which have been considered hazardous waste for several years. Samples were taken from various places in Poland. The chemical composition was examined using chemical analysis, the mineralogical phases were identified using X-ray diffraction, and the structure was identified using scanning electron microscopy, taking into account energy-dispersive spectroscopy. Thermal tests of the samples were performed using thermal analysis, thermogravimetric measurements and high-temperature microscopy. Additionally, changes that occurred in the microstructure were determined using mercury porosimetry and infrared spectroscopy. All the above research methods were used to characterise the properties of cement–asbestos materials, which were also subjected to isothermal thermal treatment at a temperature of 1100 °C for 4 h. The results proved that the material after thermal treatment undergoes significant structural changes. The thermal decomposition process of cement–asbestos involves dehydration, dehydroxylation and then recrystallisation to new stable crystalline phases but in the context of asbestos, we are dealing here with the so-called phenomenon of pseudomorphosis. Knowledge about the thermal properties of asbestos materials can provide us with data on how the material undergoes significant structural changes, thanks to which it will be possible to use neutralised cement–asbestos waste as possible safe materials.

Structural Characterisation of End-of-Life Cement–Asbestos Materials from Lithuania

Asbestos is a widely used name for natural silicate minerals with fibrous properties. Asbestos minerals were one of the most popular and cheapest raw materials used in the construction industry in the past when they was used in the form of cement–asbestos composite material. Nowadays, we know that asbestos possesses carcinogenic properties. Due to this fact, asbestos was banned in many countries including Lithuania. All asbestos-containing materials are considered waste and stored in special landfills, which causes significant environmental pollution. One of the methods proposed to solve the asbestos problem may be thermal treatment. In the present study, asbestos-containing wastes in the form of cement–asbestos materials were examined. These asbestos-containing materials were characterised via chemical analysis (XRF) connected with mineralogical phase analysis with powder X-ray diffraction (XRD) as well as scanning electron microscopy (SEM). The thermal decomposition of samples was studied via differential thermal analysis (DTA) and thermogravimetric measurements with evolved gas analysis (TG–EGA). It was found that thermal treatment is a possible way to destroy asbestos contained in cement–asbestos wastes and convert it into new mineral phases. The work also compared the obtained characteristics of asbestos waste with the characteristics of waste produced in other countries.

Epoxy Resins for Flooring Applications, an Optimal Host for Recycling Deactivated Cement Asbestos

Cement asbestos slates, commonly known as Eternit® and still abundant in private and public buildings, were deactivated through a thermal process. The resulting deactivated cement asbestos powder (DCAP), a mixture of Ca-Mg-Al silicates and glass, was compounded with Pavatekno Gold 200 (PT) and Pavafloor H200/E (PF), two different epoxy resins (bisphenol A epichlorohydrin) for flooring applications. The addition of the DCAP filler to the PF samples causes a slight but acceptable decrease in the relevant mechanical properties (compressive, tensile, and flexural strengths) upon increasing DCAP content. The addition of the DCAP filler to pure epoxy (PT resin) causes a slight decrease in the tensile and flexural strengths with increasing DCAP content, while the compressive strength is almost unaffected, and the Shore hardness increases. The main mechanical properties of the PT samples are significantly better than those of the filler-bearing sample of normal production. Overall, these results suggest that DCAP can be advantageously used as filler in addition to, or in substitution for, commercial barite. In particular, the sample with 20 wt% of DCAP is the best performing in terms of compressive, tensile, and flexural strengths, whereas the sample with 30 wt% of DCAP shows the highest Shore hardness, which is an important property to be considered in flooring applications.

Synthesis of Ye’elimite from Anthropogenic Waste

Calcium sulphoaluminate cement (CSA) is characterized by a different chemical and mineralogical composition than common cements based mainly on Portland clinker. Its main component is ye’elimite—Ca4(AlO2)6SO4. This cement is characterized by a shorter setting time and a dynamic increase in strength in the early aging process. Currently, CSA cements are gaining more and more popularity due to their favorable ecological aspects, including a reduction in carbon dioxide emissions and negative impacts on the environment. The aim of the study was to determine the possibility of obtaining ye’elimite from waste materials of anthropogenic origin, which in this case were by-products from the aluminum anodizing process and cement–asbestos waste. The results of this preliminary research indicated the possibility of obtaining ye’elimite from secondary raw materials of anthropogenic origin. In each material, the phase of ye’elimite was identified to be the main mineral component, and the obtained materials displayed binding properties after mixing with water.

Recycling detoxified cement asbestos slates in the production of ceramic sanitary wares

The recycling of cement asbestos slates (CASs) thermally treated in air at 1100 °C as secondary raw material in the production of Vitreous China (VC) sanitary wares has been investigated. Deactivated cement asbestos powder (DCAP) has been used in individual substitutions (5 wt%) of quartz and feldspar. The single raw materials, the ceramic technological properties before and after firing, and the phases and microstructure evolution during firing have been investigated with a variety of techniques, including those commonly used for production quality checks and instrumental methods for mineralogical analyses. DCAP acts as flux rather than as inert in the firing process, promoting greification. Although the substituted samples have some critical aspects that need to be addressed before processing, such as the presence of sulphate salts that increase the dispersant demand and the colour of the fired ceramic body, the overall technological properties are comparable to those of normal production, suggesting the possible reuse of DCAP powder in the production of sanitary wares.

Thermal decomposition of cement–asbestos at 1100 °C: how much “safe” is “safe”?

Thermal decomposition of cement–asbestos at 1100 °C: how much “safe” is “safe”?

Recycling of thermally treated cement-asbestos for the production of porcelain stoneware slabs

Abstract The directives of the European Commission Environment on the management of hazardous asbestos-containing materials (ACM) are pointing towards treatment and recycling other than disposal in landfills. KRY·AS is a secondary raw material obtained by the thermal transformation of cement-asbestos (CA) and can be inserted in the production line of e.g. concrete, clay bricks, ceramics, and plastic materials. This being a possible future solution to the huge “CA-emergency” in Italy, additional recycling options are sought. In this work, KRY·AS was used for the production of glass-ceramic frits destined for the manufacturing of porcelain stoneware slabs. Two novel frits were obtained by vitrifying KRY·AS together with minor amounts of natural raw materials as well as glass waste. The resulting frits were added in a ceramic body formulation (0, 1, 3, 5 wt.%). Phase composition, microstructure and technological properties of fired samples were evaluated and the results were compared to those obtained when using a standard commercial frit. According to water absorption tests, the novel products can be classified as BIa-type. Comparable or even improved technological properties were found between the standard body and the frit-bearing ones. More precisely, the addition of 5 wt.% of the novel frits led to better stain resistance as well as higher productivity due to reduction of the linear firing shrinkage. Improved mechanical strength (ca. 75 MPa compared to ca 60 MPa for the standard) was also obtained. The novel recycling route of KRY·AS supports a conclusive solution for the management of hazardous CA in Italy.

Dark fermentation process as pretreatment for a sustainable denaturation of asbestos containing wastes

A cement asbestos compound (CAC) sample was detoxified by a treatment train based on a dark fermentation (DF) process followed by a hydrothermal phase, which led to the complete degradation of the chrysotile fibers. During the biological pretreatment, the glucose was converted in biogas rich in H2 and volatile fatty acids (VFA). The latter caused the dissolution of all the Ca-based compounds and the solubilisation of 50% brucite-like layers of chrysotile fibers contained in the CAC suspended in the bioreactor (5 g/L). XRD analysis of the solids contained in the effluents of the DF process highlighted the disappearance of the chrysotile fiber peaks. However, a complete destruction of all the asbestos fibers is hard to prove and a hydrothermal treatment was carried out to dissolve the “brucite” layers still present in solution. Due to the presence of the VFA produced during the DF, a complete destruction of chrysotile fibers was achieved by a 24 h hydrothermal process performed with a [H2SO4]/[CAC] ratio 50% lower than that adopted in a previous finding. Consequently, the DF pre-treatment can contribute to lower the H2SO4 and the energy consumption of a CAC hydrothermal treatment, due to the production of VFA and H2.

해체·제거 작업 시 석면함유 건축자재에서 발생되는 섬유 및 입자상 물질의 특성

Objectives: This study focused on three aspects: characterizing concentrations of airborne particles by size distributions and asbestos fibers generated by various building materials; analyzing the characteristics of fibers produced by each simulation and asbestos fibers released from ACBMs; and investigating correlations of airborne asbestos fibers and particles generated and association of particle and asbestos concentrations. Methods: We selected three ACBMs including an insulation board, cement asbestos slate and wallboard. We constructed 4 scenarios; a) crushing with a hammer; b) cutting with a industrial knife; c) brushing with a metal brush; and d) tightening & loosening with a hand drill. We implemented one simulation for 30 seconds followed by 30 seconds resting period. We repeated a total of 5 cycles for 5 minutes. Results: The highest concentration of particulate & fibrous matters was from crushing with a hammer in each scenario followed by brushing with a metal brush, cutting with a industrial knife, and tightening & loosening with a hand drill. For ACBMs studied, asbestos concentrations were highest from an insulation board followed by cement asbestos slate, and wallboard. No difference in terms of concentration was found between an insulation board and asbestos slate. Fibers with 5~20 μm in length were included in 76~90% of total fibrous matters. The distribution of the straight form fibers was greater than that of the curl form. About 90% of PMTotal released from ACBMs was consisted of PM10 while only 10% of PMTotal was PM2.5. Particulate matters like PM2.5 was significantly correlated with fibrous matters(R 2 =0.81). Conclusions: We found ACBMs can significantly release asbestos fibers as well as PM2.5. Concentrations of asbestos generated by ACBMs were well correlated with PM2.5.

Study on the thermal decomposition of crocidolite asbestos

The thermal behaviour of two crocidolite asbestos samples was characterized. Infrared spectroscopy (FT-IR), powder X-ray diffraction, scanning electron microscopy and thermal analysis (DTA and TG) with evolved gas analysis were carried out on samples of crocidolite asbestos as received and after heating in order to observe their structural changes and dehydroxylation process. The results show that the dehydroxylation process of crocidolite asbestos occurs at different temperatures and is in the range 400–650 °C. This temperature is dependent on the origin of asbestos samples and may be associated with an increased amount of magnesium in the structure of asbestos. For the sample which comes from the Republic of South Africa, the dehydroxylation process occurs at lower temperature in contrast to Russian crocidolite asbestos sample from cement–asbestos material. However, this temperature range is lower than those reported by some authors, who state that the decomposition temperature of crocidolite should be at least 900 °C. This finding may have a significant influence on thermal utilization of asbestos materials, e.g. cement–asbestos, because the temperature of the heat treatment in the utilization process should be as low as possible.

Raw and thermally treated cement asbestos exerts different cytotoxicity effects on A549 cells in vitro

Raw cement asbestos (RCA) undergoes a complete solid state transformation when heated at high temperatures. The secondary raw material produced, high temperatures-cement asbestos (HT-CA) is composed of newly-formed crystals in place of the asbestos fibers present in RCA. Our previous study showed that HT-CA exerts lower cytotoxic cell damage compared to RCA. Nevertheless further investigations are needed to deepen our understanding of pathogenic pathways involving oxidative and nitrative damage. Our aim is to deepen the understanding of the biological effects on A549 cells of these materials regarding DNA damage related proteins (p53, its isoform p73 and TRAIL) and nitric oxide (NO) production during inducible nitric oxide synthase (iNOS)-mediated inflammation. Increments of p53/p73 expression, iNOS positive cells and NO concentrations were found with RCA, compared to HT-CA and controls mainly at 48h. Interestingly, ferrous iron causing reactive oxygen species (ROS)-mediated DNA damage was found in RCA as a contaminant.HT-CA thermal treatment induces a global recrystallization with iron in a crystal form poorly released in media. HT-CA slightly interferes with genome expression and exerts lower inflammatory potential compared to RCA on biological systems. It could represent a safe approach for storing or recycling asbestos and an environmentally friendly alternative to asbestos waste.

The potential use of cement–asbestos waste in the ceramic masses destined for sintered wall clay brick manufacture

Asbestos fibers are considered to be carcinogenic and to cause cancer, thus elimination of asbestos-containing materials from the environment is necessary. Currently, asbestos materials are stored in special landfills designed for hazardous wastes. However, this procedure is not a final solution to the problem and an alternative might be thermal recycling. This paper reports the results of a study on using asbestos-cement slates as an additive to ceramic masses that are typical in the manufacture of sintered clinker wall bricks. Green compacts containing various amounts (0–10wt%) of asbestos–cement wastes were sintered at temperatures of 1100–1200°C. Subsequently, ceramic product properties such as water absorption, open porosity, apparent density, compressive strength and freeze resistance were determined. The preliminary results of the study indicate that asbestos-containing materials can be used as one of the raw materials in the manufacture of clinker ceramic material, and that the origin of the asbestos–cement used does not have a significant influence on the basic properties of sintered clinker wall bricks. Main ceramic properties, such as water absorption, compressive strength and freeze resistance, comply with national standards and requirements for construction and road clinker ceramic.

Crystal chemistry of cement-asbestos

A study of a representative number of cement-asbestos (CA) samples removed from different localities in Italy has been accomplished with a combination of analytical techniques, including XRF, XRPD, SEM/EDS, micro-Raman, and electron backscattered diffraction (EBSD), to elucidate the mineralogical and chemical variability of this class of building materials on a large scale. We describe a complex mineralogy including phases of cement hydration, residual non-hydrated components, and a relevant fraction attributed to various processes of deterioration. With the aid of the CaO-MgO-SiO2 compositional diagram, three groups of CAs have been identified on the basis of their chemical parameters. This result is important for environmental and waste management issues.

Crystal chemistry of the high temperature product of transformation of cement-asbestos

In this work, the high-temperature inertization product of a representative batch of samples of cement-asbestos (CA) from different localities in Italy have been characterized with a multidisciplinary approach. All the raw CA samples were heated at 1200°C for 15min. After firing, they underwent a series of solid state reactions leading to global structural changes of the matrix. Effects of annealing time and temperature on the crystallization kinetics were thoroughly investigated. Both factors acted in favour of equilibrium. Three classes of CA were identified with the aid of phase diagrams and of specific plots relating chemical and mineralogical parameters. This result was considered of importance in view of the potential use of transformed cement-asbestos as a secondary raw material. In principle, the content of CA packages removed from the environment and their corresponding heat-treated products can be classified simply using XRF. This method allows for the selection of appropriate fractions in function of the most suitable recycling solution adopted. Samples belonging to the class called larnite-rich, turned out to be of great interest as possible candidate for substituting a fraction of cement in many building materials and innovative green cement productions.

In vitro biological effects of raw and thermally treated asbestos-containing materials

Asbestos cement, the main asbestos-containing material (ACM) manufactured in Italy in the past, is a health hazard whose elimination is a priority concern. Asbestos fibers can be transformed into potentially non-hazardous silicates by high-temperature treatment via complete solid-state transformation. In this study human A549 cells were directly exposed to raw cement asbestos (RCA), chrysotile and cement asbestos subjected to an industrial process at 1200 °C (HT-CA) and raw commercial grey cement (GC) for 24 and 48h, or treated with conditioned culture medium up to 96 h. In our previous studies we demonstrated that the final product of heat treatment of cement asbestos was considerably more inert and had lower cytotoxic potential than the original asbestos material. However, to better evaluate the risks of interactions with the materials, further in vitro investigations were performed concerning fiber-cell superficial interactions, immuno-hystochemical expression of cytochines p53, p53 homologue p73, TNF-related apoptosis- inducing ligand (TRAIL), and conditioned medium effects on cell viability. Data showed more severe cytotoxic damage by raw cement-asbestos compared to the heat treated materials and different expressions of cytochines that exert critical role in regulating the cell response to asbestos-induced DNA damage. These data should be taken in consideration for a safe recycling of thermal transformed asbestos materials.

In vitro biodurability of the product of thermal transformation of cement–asbestos

To safely recycle the product of the thermal transformation of cement–asbestos as secondary raw material, its toxicity potential should be assessed by in vitro biodurability tests. In this work, the acellular in vitro biodurability of the products of transformation of cement–asbestos at 1200°C (named KRY·AS) was tested using both inorganic and organic simulated lung fluids at pH 4.5. The dissolution kinetics were followed using chemical, mineralogical and microstructural analyses. The total dissolution time estimated from the experiments with inorganic HCl diluted solution is one order of magnitude higher than that determined from the experiments with buffered Gamble solution (253 days vs. 20 days). The key parameter determining the difference in dissolution rate turns out to be the solidus/liquidus ratio which prompts a fast saturation of the solution with monosilicic acid. The calculated dissolution rate constants showed that the biodurability in vitro of KRY·AS is much lower with respect to that of standard chrysotile asbestos (total estimated dissolution time of 20 days vs. 298 days, respectively). This proves a low potential toxicity of this secondary raw material.

Recycling of the product of thermal inertization of cement–asbestos for the production of concrete

A novel field of research in materials science is the recycling of secondary raw materials for construction and building materials such as concrete. This paper describes the successful recycling of as much as 20 wt% of the product of thermal transformation of cement–asbestos for the formulation of concrete. The main mineralogical phases present in the product of transformation of cement–asbestos are C2S, ferrite, and Al-, Ca-, Mg-rich silicates such as akermanite (ideally Ca 2MgSi 2O 7) and merwinite (ideally Ca 3Mg 2Si 2O 8). The behavior of this secondary raw material, termed KRY·AS, in commercial concrete was investigated using five different mixtures in which various portions (0, 5, 10, 15 and 20 wt%) of cement were substituted by KRY·AS. The results of preliminary technological tests (slump test, compressive strength, flexural strength after 28 days, and depth of penetration of water under pressure after 28 days) were discussed and interpreted with the aid of chemical, mineralogical and SEM analyses. One of the major results is that after 28 days, although all the concrete samples are invariably classified as “ordinary concrete” according to the UNI 6132 tests, those diluted with KRY·AS display a lower resistance to compression with respect to the standard. On the other hand, they recover compressive strength and display values identical to that of the standard after 90 days. The addition of the secondary raw material has the effect to slow down the kinetics of setting/hardening because the main cement phase present in KRY·AS is C2S which has a slower rate of hydration with respect to C3S.

Recycling of the product of thermal inertization of cement–asbestos for various industrial applications

Recycling of secondary raw materials is a priority of waste handling in the countries of the European community. A potentially important secondary raw material is the product of the thermal transformation of cement–asbestos, produced by prolonged annealing at 1200–1300 °C. The product is chemically comparable to a Mg-rich clinker. Previous work has assured the reliability of the transformation process. The current challenge is to find potential applications as secondary raw material. Recycling of thermally treated asbestos-containing material (named KRY·AS) in traditional ceramics has already been studied with successful results. The results presented here are the outcome of a long termed project started in 2005 and devoted to the recycling of this secondary raw materials in various industrial applications. KRY·AS can be added in medium-high percentages (10–40 wt%) to commercial mixtures for the production of clay bricks, rock-wool glasses for insulation as well as Ca-based frits and glass–ceramics for the production of ceramic tiles. The secondary raw material was also used for the synthesis of two ceramic pigments; a green uvarovite-based pigment [Ca 3Cr 2(SiO 4) 3] and a pink malayaite-based pigment [Ca(Sn,Cr)SiO 5]. The latter is especially interesting as a substitute for cadmium-based pigments. This work also shows that KRY·AS can replace standard fillers in polypropylene plastics without altering the properties of the final product. For each application, a description and relevant results are presented and discussed.

Biological effects and comparative cytotoxicity of thermal transformed asbestos-containing materials in a human alveolar epithelial cell line

Asbestos fibres can be transformed into potentially non-hazardous silicates by high-temperature treatment via complete solid-state transformation. A549 cells were exposed to standard concentrations of raw cement asbestos (RCA), chrysotile and cement asbestos subjected to an industrial process at 1200 °C (Cry_1200 and KRY·AS, respectively), raw commercial grey cement (GC). Cell growth rate and viability (MTT test) were detected in vitro. RCA and KRY·AS subjected to comprehensive microstructural study by electron microscopy were further in vitro assayed to compare their cytotoxic potential by morphostructural studies, proliferation index (Ki-67 antigen), apoptosis induction (AO/EB staining) assays and detection of intracellular reactive oxygen species (ROS) with the fluorescent DCFA dye. More severe cytotoxic damage was induced by RCA than by KRY·AS after each incubation period. Exposure to KRY·AS and GC resulted in comparable cell growth rates and cytotoxic effects. Cells incubated with RCA showed greater apoptotic induction and ROS production and a lower cell proliferation index than those exposed to KRY·AS. Chrysotile asbestos and RCA subjected to heat treatment underwent complete microstructure transformation. The final product of heat treatment of cement asbestos, KRY·AS, was considerably more inert and had lower cytotoxic potential than the original asbestos material in all in vitro tests.

A multi-layer capping of a coastal area contaminated with materials dangerous to health

Environmental protection efforts in coastal areas recognise contaminated materials as a critical element of the aquatic ecosystem requiring careful evaluation for their potential remediation. This article considers aspects related to the design of a multi-layer capping for a contaminated coastal area. The area is located just south of the urbanised region of Bari, Puglia Region, along the Adriatic coast of Italy. This area received massive displacement of cement asbestos from residuals of a factory producing concrete pipelines for aqueducts and asbestos boards. The designed reclamation has been proposed in order to allow reuse of the 2.4-km-long coastline for recreational activities. For this purpose, the main objective has been to face aspects related to the problems posed by the design of the adopted capping structure and various constraints related to the natural environment. An extensive numerical study has been carried out to verify the effects of the planned intervention. The local wave climate, wave- and wind-induced circulation, the impact on water quality, and the biological system have been investigated. At present, the intervention is under construction.