Implications of Israeli Standard 5098 on uses of coal fly ash in the local construction industry

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1 Workshop on Environmental and Health Aspects of Coal Ash Utilization International workshop 23 rd 24 th November 2005 Tel-Aviv, Israel Implications of Israeli Standard 5098 on uses of coal fly ash in the local construction industry Konstantin Kovler National Building Research Institute Faculty of Civil and Environmental Engineering, Technion Israel Institute of Technology, Haifa 32000, Israel The building industry uses large amounts of waste products from other industries. In resent years there is a growing tendency to use new recycled materials with technologically enhanced levels of radioactivity. Israel has recently joined the countries producing a significant amount of industrial by-products, including those containing slightly elevated amounts of radioactive impurities. The most known example is coal fly ash. Coal, like most earth materials, contains 238 U, the parent element of the uranium decay series, which supports several radioactive decay products including radon. Large quantities of fly ash are expelled from coal-fired thermal power plants and these may contain enhanced levels of radionuclides along with other toxic elements. Increased interest in measuring radionuclides and radon concentration in fly ash, cement and other components of building products is due to the health hazards and environmental pollution. American scientists admit that research into the problems related to coal fly ash storage and disposal should become a priority because about 100 million metric tons of fly ash are produced each year in the United States alone [1]. In Israel, about a hundred per cent of fly ash is being utilized in different ways. About 1,000,000 tones are utilized now in building industry: manufacture of pozzolanic cement, as cement additive and sand substitute in concrete production. The rest of fly ash is being used in the ceramics industry, in road embankment and for agricultural purposes. In view of these numbers, the situation with re-use of coal fly ash in the country looks favorable. Private organizations too have been making their own efforts. Companies like IEC (Israel Electric Company Ltd.), Nesher (Portland cement manufacturer) and ready-mix concrete producers, for instance, came up with innovative technologies, for the commercial utilization of fly ash and its disposal, respectively. This progress could not be achieved without significant efforts of National Building Research Institute, Israeli Institute of Standards, National Coal Ash Board (NCAB) and other governmental and public institutions, which studied, standardized and promoted various applications of coal ash in construction and other industries. Several years ago Israel faced a serious problem of utilization of the coal fly ash. According to NCAB, its yield in 2004 year amounted to 1,199 thousand tones and the forecast for 2012 was 1,440 thousand tones (Table 1). At present the situation has changed, with the industrial demand for the ash increasing every year. On one hand, this is a remarkable achievement which solves the utilization problem (including those of storage and screening). On the other hand, the increased demand (1,330 thousand

2 2 tones forecast for building industry in 2012) means higher radionuclide levels in building materials, with the corresponding increase in radiation exposure of the population, mainly to gamma doses. In view of this, there was a need of introducing national standard regulating the content of radionuclides in building materials. Table 1: Coal ash utilization forecast balance-sheet in Israel, offer and demand (thousand tones) Scenario 2004 Actual Feasible Fly ash Bottom ash Fly ash Bottom ash Cement Concrete Concrete products 100 Masonry blocks Infrastructure Agriculture Industry Export 200 Total demand Produced As can be seen from Table 2 adapted from [2], radioactivity concentrations found in fly ash and some other industrial by-products are often significantly higher in comparison with most common building materials. Table 2: Typical and maximum activity concentrations in common building materials and industrial by-products used for building materials in the EU [2] Material Typical activity concentration (Bq/kg) Maximum activity concentration (Bq/kg) 226 Ra 232 Th 40 K Radium equivalent 226 Ra 232 Th 40 K Radium equivalent Most common building materials (may include by-products) Concrete Aerated and lightweight concrete Clay (red) bricks Sand-lime bricks Natural building stones Natural gypsum Most common industrial by-products used in building materials Phosphogypsum Blast furnace slag Coal fly ash The European Basic Safety Standards Directive (BSS) sets down a framework for controlling exposures to natural radiation sources arising from work activities. Title VII of the directive applies to work activities within which the presence of natural radiation sources leads to a significant increase in the exposure of workers or of members of the public. Amongst the activities identified in the BSS as potentially of

3 3 concern are those which lead to the production of residues which contain naturally occurring radionuclides causing significant increase in the exposure of members of the public. Such materials may include coal ash from power stations, by-product gypsum and certain slags which are produced in large volumes and which may potentially be used as building materials. The purpose of setting controls on the radioactivity of building materials is to limit the radiation exposure due to materials with enhanced or elevated levels of natural radionuclides. The recently published document Radiation Protection 112 [2] provides guidance for setting controls on the radioactivity of building materials in European countries. This guidance is relevant for newly produced building materials and not intended to be applied to existing buildings. In particular, the document [2] assumes that: Within the European Union, doses exceeding 1 msv/year should be taken into account from the radiation protection point of view. Higher doses should be accepted only in some very exceptional cases were materials are used locally; Controls can be based on a lower dose criterion if it is judged that this is desirable and will not lead to impractical controls. It is therefore recommended that controls should be based on a dose in the range msv/year. This is the excess gamma dose to that received outdoors; The criterion of meeting the standard is the value of so called activity concentration index taking into account the total effect of three main natural radionuclides, which can present in building materials (I = 226 Ra/ Th/ K/3000, concentrations are given in Bq/kg); The activity concentration index I shall not exceed the following values depending on the dose criterion and the way and the amount the material is used in a building (Table 4): Table 3: Dose criterion recommended by EU [2] Dose criterion msv/year msv/year Materials used in bulk amounts, e.g. concrete I 0.5 I 1 Superficial and other materials with restricted use: tiles, boards, etc. I 2 I 6 The document [2] requires that the activity concentration index should be used only as a screening tool for identifying materials which might be of concern. Any actual decision on restricting the use of a material should be based on a separate dose assessment. Such assessment should be based on scenarios where the material is used in a typical way for the type of material in question. Scenarios resulting in theoretical, most unlikely maximum doses should be avoided. The purpose of controls is to restrict the highest individual doses. Therefore, the dose criterion used for national controls should be chosen in a way that the majority of normal building materials on the market fulfill the requirements. Usually measurements of activity concentrations are needed only in case where there is a specific reason to suspect that the dose criterion for controls might be exceeded. At the same time, Member States should require, as a minimum, the measurement of types of materials which are generically suspected. Finally, the use of industrial by-products containing natural radionuclides in building materials, which could result in activity concentration indices exceeding the values

4 4 specified in Table 3 should be justified on a case by case basis by Member States. It is expected that such justification would include non-radiological criteria. For example, some traditionally used natural building materials contain natural radionuclides at levels such that the annual dose of 1 msv might be exceeded. Some of such materials may have been used already for decades or centuries. In these cases, the detriments and costs of giving up the use of such materials should be analyzed and should include financial and social costs. Recently Finland and Denmark issued their national regulations based on the EU guidelines [2]. Danish document [3] seems to be especially interesting, because the natural radioactivity background in this country is also low, similarly to that in Israel. As calculations show, preventing an exposure of the Israeli population to each 0.1 msv/year would be equivalent to the increase of personal income by ~2%, i.e. costs about 140 million USD for the national budget. In other words, the tendency of making the environmental standards stricter should be supported by funding from the national budget. Otherwise strict standards are not applicable. As an example of the complicated and confused situation with applying standards, which do not take into account these financial and social costs, is a recent publication of the first national standard No regulating the content of radionuclides in building products in Israel [4]. This standard is the strictest one among different national and international standards regulating the content of radionuclides in building materials. As calculations show, even regular building products, such as ordinary Portland cement concrete, some types of ceramic tiles, granite tiles and slabs, lightweight masonry blocks and some other products, hardly meet the standard criterion. For example, radioactivity index of 12 concrete mixes made with local sand and coarse aggregates, with and without coal fly ash, which was determined by the laboratory ESC - Environmental Services Company Ltd., according to Israeli Standard 5098 (SI-5098) [4] and EU guidelines [2], is shown in Fig Radioactivity Index VD-0 VK-0 HR-0 HC-0 VD-150 VK-150 HR-150 HC-150 VD- RP-112 SI-5098 VK- HR- HC- Figure 1: Radioactivity index of 12 concrete mixes made with local fine and coarse aggregates, according to Israeli Standard 5098 (SI-5098) [4] and EU guidelines [2]; the letters in the mix code are for coarse aggregate type, the numbers 0 and 150 show the fly ash content in kg/m 3 ; cement content in the mixes was 450 kg/m 3, except for

5 5 the mixes VD- and VK- (270 kg/m 3 ), and HR- and HC- (230 kg/m 3 ). Concrete mixes were made of fine and coarse aggregates representing ~50% of the local quarries serving the concrete industry. It can be seen that the radioactivity index of 4 concrete mixes containing 150 kg/m 3 of coal fly ash (VD-150, VK-150, HR-150 and HC-150) is higher by ~20% than that of the reference mixes without fly ash, in average. This result is supported by calculations of the expected radioactivity concentrations in concrete, knowing the specific radioactivity concentrations and contents of the concrete components. It should be emphasized that almost all the mixes, even without addition of fly ash, do not meet the Israeli standard (the index is higher than 1). At the same time, they meet easily the requirements in Europe, even those based on the strictest value of the allowable dose (0.3 msv/year), such as Danish regulations [3] 1. Concrete is the main building material in the region. Therefore, this situation is absurd and contradicts the principles [2] stating, in particular, that the dose criterion used for national controls should be chosen in a way that the majority of normal building materials on the market fulfill the requirements. Unjustified strictness makes the standard inapplicable for many types of building materials, and some of them are excluded, one by one, from the standard scope. At the moment the standard [4] deals with light-weight masonry blocks only, instead of dealing with all mineral building products used in Israel as declared in its title. The situation with the new standard is widely discussed nowadays by public. To solve this problem, the ways based on adapting the principles formulated in the EU guidelines have been suggested. CONCLUSIONS In recent years there is a growing tendency to use new recycled materials with technologically enhanced levels of radioactivity. Coal fly ash is valuable industrial by-product having a potential to be re-used in construction, however the problem of its contaminants has to be addressed. In view of this, there is a need in introducing environmentally safe and economically reasonable standard regulations, which should be based on justified radiological, social and economical legislation concepts. ACKNOWLEDGEMENTS The author is thankful to Mr. G. Irus, Mr. N. Lavi, Mr. O. Lulav and Mr. Y. Sikuler for their help with sampling and testing concrete mixes, and also for discussion of the experimental part of the study. REFERENCES [1] [2] 'Radiological Protection Principles Concerning the Natural Radioactivity of Building Materials', Radiation Protection 112 (European Commission, Directorate-General, Environment, Nuclear Safety and Civil Protection, 1999). [3] 'Bekendtgørelse om undtagelsesregler fra lov om brug m.v. af radioaktive stoffer', Bekendtgørelse nr. 192 af 2., April 2002 (in Danish). [4] 'Content of radioactive elements in building materials', Israeli Standard 5098, The Standards Institution of Israel, November 2002 (in Hebrew). 1 According to [3], concrete made of local Danish aggregates is exempted from controls.