Introduction

W. Schroeyers *; K. Kovler † ^* Hasselt University, CMK, NuTeC, Diepenbeek, Belgium
† Technion – Israel Institute of Technology, Haifa, Israel

Abstract

This chapter introduces the reader with the book scope, key concepts, contents, and main terminology, such as naturally occurring radioactive materials (NORM), NORM residues, NORM by-products, NORM waste, NORM processing industries, NORM containing building materials, etc.

Terminology is important, since the terms that are used demonstrate the way that the world around us is perceived, but also if the use of specific materials for a given application is deemed to be acceptable or not. Before reading this book, in order to avoid misunderstanding, it is important that the reader understands some of the key concepts (or the perspective of the author(s) on these key concepts) that form the core of this book.

Keywords

Terminology; Perception; NORM; NORM by-products; Construction materials

Guide for the reader: Situating chapter “2”:

Chapter 2 gives an introduction that focuses on finding the appropriate terminology to discuss the use of naturally occurring radioactive materials (NORM) in construction.

The main radiological parameters to be controlled in NORM and NORM containing building materials are discussed in Chapter 3. An in-depth discussion on the legislative aspects regarding natural radioactivity from building materials is given in Chapter 4. The methods for radiological characterization of construction materials are discussed extensively in Chapter 5.

The technical, chemical, and radiological properties of NORM by-products are considered in Chapter 6 with a focus on by-products that can be used in construction. Several applications of the considered NORM by-products in construction materials (cement, concrete, ceramics, and gypsum) are discussed in more detail in Chapter 7. In Chapter 8, an environmental leaching assessment of NORM containing construction materials is given. Nontechnical aspects that determine the reuse of NORM by-products are discussed in Chapter 9. Finally, Chapter 10 gives a general conclusion and outlook.

The depletion of energy resources and primary raw materials leads to the search for alternative pathways to produce construction materials. In the development of new synthetic construction materials, the use of by-products from several industrial sectors becomes more and more a necessity especially in a resource-poor continent such as Europe. By-products, such as slag and bottom ash from coal-fired power plants; unprocessed slag from primary iron production; lead, copper, and tin slags from primary and secondary production; and bauxite residue (red mud) from aluminum production, have interesting properties for use in construction but can in some cases, depending on the activity concentration, be considered as naturally occurring radioactive materials (NORM).

These by-products can be used in cement as alternative raw materials and supplementary cementitious materials (SCMs) or, in the case of by-products with a high caloric value, they can be introduced as an alternative fuel, the remaining ash being typically incorporated in the cement clinker (Guidelines on Co-processing Waste Materials in Cement Production, 2006; Hasanbeigi et al., 2012). In concrete several of these by-products are used or studied for use in increased amounts as SCMs (as partial cement replacement or as mineral additions in concrete) and as aggregates for concrete (Siddique and Khan, 2011). In ceramics, various types of metal slags were used, or investigated for use, as aggregates in for example clay-based ceramics (Pontikes and Angelopoulos, 2009). Alternatively, other types of by-products such as bauxite residue can be used in the bond system of clay ceramics (Pontikes and Angelopoulos, 2009). An emerging field in the construction industry is the development of alkali-activated materials (AAMs). The AAMs can contain calcium silicate or a more aluminosilicate-rich precursor, such as a metallurgical slag, natural pozzolan, fly ash or bottom ash as solid aluminosilicate source (Shi et al., 2006).

The terminology used to label a given material can inhibit or stimulate its application. Using the label “waste” for a given material creates the perception that these materials do not fit any application. Once a material is labeled as a “waste,” then reuse will not be easily accepted any more, both from a public and from a legislative perspective. The IAEA uses in its safety glossary as definition for waste “a material for which no further use is foreseen” (IAEA safety glossary, 2007). By this definition, once an application acceptable from a safety, societal, and engineering point of view is developed, then the material should not be considered (any more) as a waste. Since this book deals with the potential use of materials in construction, the term “waste” will not be further used unless justified from a legislative or safety perspective.

A common misperception, by the general public, is that primary raw materials are considered as “pure” and secondary raw materials as “impure.” The terms “pure” or “impure” should not be used due to the connotation of these terms but what is meant here is that the perception exists that secondary raw materials, when compared with primary raw materials, contain significantly more trace elements that can make them undesired for use in construction materials. When looking from a chemical, mineralogical point of view and comparing primary and secondary raw materials, with suitable properties for construction materials, then the presence of trace elements is strongly dependent on the type of primary raw material (e.g., limestone, clay, marl, or sand) or secondary raw material (e.g., blast-furnace slag, coal fly ash) that is used. It is not necessary true that secondary raw materials contain a higher concentration of trace elements compared with primary raw materials (Table 2.1). When comparing the average composition of clay, one of the oldest building materials on the Earth, to that of blast-furnace slag then it is clear from Table 2.1 that the concentration of trace elements such as As, Co, Cr, Cu, Ni, Pb, V, Zn can be higher in clay.

Table 2.1

Average values (AV) of selected input materials that can be used in cement or concrete (Achternbosch et al., 2005)

Data in ppm		As	Cd	Co	Cr	Cu	Ni	Pb	Sb	Sn	V	Zn
Limestone	AV	3	0.2	3	14	11	18	18	1	4	26	30
Clay	AV	14	0.2	20	85	43	63	25	2	5	130	78
Marl	AV	6	0.3	5	28	12	16	12	4	3	20	48
Sand	AV	11	0.2	11	19	10	13	10	7	3	50	25
Iron works waste	xMin^a	74	29	149	600	1076	254	481	10	81	229	2262
Iron ore	AV	37	6	144	495	1520	331	350	26	25	256	3288
Foundry sand	AV	3	0.3	90	290	28	92	62	0.8	40	150	75
Hard coal	AV	9	1.0	9	14	18	23	27	1	4	39	63
Brown coal	AV	0.8	0.2	1	3.6	1.8	3	3	0.8	4	10	10
Oil coke	AV	0.5	1	2.5	4.3	2.4	263	13	0.6	0.3	758	16
Used tyres	AV	1.6	7	30	137	68	90	125	136	15	19	6100
Waste oil	AV	2.4	0.8	1	12	51	20	151	1	6	2	700
Scrap wood	AV	3.4	1.2	10	27	24	13	222	8	6	3	440
MCIW fuel	AV	3	2.5	4	51	138	25	74	25	20	7	331
Blast-furnace slag	AV	0.8	0.7	4	25	5.2	5	6	2	5	30	38
Coal fly ash	AV	79	2.6	74	172	247	196	257	14	10	345	504

t0010

AV, average; MCIW, fuel, fractions from municipal, commercial, and industrial wastes.

^a Average minimum values (xMin) were used (see Achternbosch et al., 2005).

In addition to the considered chemical trace elements, all materials (ores, minerals) that are extracted from the Earth's crust contain concentrations of natural occurring radionuclides (NOR) that are, due to their long decay times, already present since the birth of the Earth. Since radioactivity is present everywhere there is a need to define what is considered as a radioactive material. One definition used by the IAEA Safety Glossary for a radioactive material is “Material designated in national law or by a regulatory body as being subject to regulatory control because of its radioactivity.” The IAEA Safety Glossary defines NORM as a “Radioactive material containing no significant amounts of radionuclides other than naturally occurring radionuclides” where the exact definition of “significant amounts of naturally occurring radionuclides” would be a regulatory decision. In the IAEA glossary, NORM residue is defined as a “Material that remains from a process and comprises or is contaminated by NORM” and NORM waste is defined as “NORM for which no further use is foreseen” (IAEA safety glossary, 2007).

To establish what is NORM and what is not, the IAEA and Euratom Basic Safety Standards (IAEA- and EU-BSS) have selected a list of industrial sectors of concern (ANNEX VI of the Council Directive 2013/59/EURATOM, 2014). For these “industrial sectors involving NORM” the IAEA- and EU-BSS have defined an activity concentration of 1 kBq/kg of ²³⁸U, ²³²Th (or any of their decay products) and an activity concentration of 10 kBq/kg of ⁴⁰K as significant concentrations of these NOR. In other words, only if an activity concentration of more than 1 kBq/kg of ²³⁸U, ²³²Th (or any of their decay products) or more than 10 kBq/kg of ⁴⁰K is measured for a specific type of material from the industries mentioned in ANNEX VI, then this can be considered as NORM according to the EU- and IAEA-BSS (IAEA, 2014) and Council Directive, 2013/59/EURATOM (2014). It is important to keep in mind that 1 kBq/kg of a given radionuclide represents a relatively low concentration (generally expressed in ppm) as is illustrated in Table 2.2 and that in many cases only radiological methods are sensitive enough to determine the activity concentration of several materials. Considering these aspects then a “NORM residue” is a material that remains from a process, which contains more than 1 kBq/kg of ²³⁸U, ²³²Th (or any of their decay products) or more than 10 kBq/kg of ⁴⁰K.

Table 2.2

Conversion of 1 kBq/kg to ppm

Radionuclide	Activity concentration (kBq/kg)	Concentration (ppm)
²³⁸U	1	81
²³²Th	1	246
⁴⁰K	1	32,300

Modern production processes can be designed in such a way that no materials, or at least no large quantities of materials, remain any more after production. In such a production process all the output streams, or at least all output streams that contain large quantities of materials, are used. In this case, from a chemical point of view, all materials coming out of the process can be considered as the “product” of the reaction/production. From a (simplified) process technical point of view incoming materials can be considered as reagents and outgoing materials as (by-)products. In this terminology even filter dust or other materials that are the result of several emission control steps can be considered as a (by-)product. The term “product” has an economic connotation that indicates a material that can be sold. Modern processes are often designed in such a way with the intention to sell all products depending on the conditions on the market. Considering this discussion than the term “NORM residue” is not suitable in many situation and we could introduce the term “NORM by-product” meaning a by-product from an industrial process, which contains more than 1 kBq/kg of ²³⁸U, ²³²Th (or any of their decay products) or more than 10 kBq/kg of ⁴⁰K.

In this book both the terms “NORM by-product,” which seems to be the most appropriate term, and “NORM residue,” since it is formally defined in the IAEA glossary, are used. The term “NORM residue” can be in particular appropriate to also cover residues that remain from legacy sites. It can also be noted that if industrial processes are designed taking into account the NORM aspects that the term “NORM by-product” could in the future only apply to lower quantities of materials.

The term “NORM industries” will not be used in this book. There are no industries that “willingly” produce NORM, there are, however, industries that produce steel, metals, fertilizer, etc. In this book the terms “NORM processing industries” and “industries invoking NORM” will be used instead but the reader should keep in mind that most of the by-products produced in these industrial sectors are not NORM.

In addition to the NORM-related regulation, the EU-BSS requires the control of selected natural building materials and building materials “incorporating residues from industries processing naturally occurring radioactive material” (listed in annex XIII). For building materials, a reference level of 1 mSv per year is set for indoor external exposure to gamma radiation emitted by building materials, in addition to outdoor external exposure (Council Directive 2013/59/EURATOM, 2014). A term that will be used in this book is “NORM containing building materials,” however, as noted earlier many of the by-products that are discussed are not necessarily NORM. This book focuses on NOR that enter the construction materials via the by-products and not specifically on natural building materials.

Regarding the terms “building materials” and “construction materials,” the book uses both of them. The term “construction”‬ in civil engineering includes a broader perspective than “buildings.” A building is normally some structure used to enclose a space. Construction works is a term that is more general and includes construction of buildings, bridges, roads, railways, harbors, etc. It means that the term “construction materials” is valid not only for materials used in construction of buildings, but also for those used in other types of structures.

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 average annual exposure duration of the building occupants to natural ionizing radiation is 7000 h, while the exposure of the public to radiation from construction materials applied in other types of structures, such as tunnels, bridges, etc., is significantly shorter. Therefore, from the radiological perspective, the construction materials, which are used in building construction, are the focus of the discussion in the book chapters.

Finally, one more remark should be made on the differences between “materials” and “products,” and between “materials” and their “constituents.” The term “building materials” usually includes both “materials,” which are produced and sold, but still do not have a final properties and shape as finished products, and “building products” (or “construction products”), which do have a well-defined geometry and properties (density, strength, thermal and acoustic insulation, etc.). “Construction product” means any product or kit which is produced and placed on the market for incorporation in a permanent manner in construction works or parts thereof and the performance of which has an effect on the performance of the construction works with respect to the basic requirements for construction works (Regulation (EU) No. 305/2011 of the European Parliament and of the Council, 2011).

The examples of building materials of the first type, which are called sometimes as “constituents” of building materials, are cement and concrete aggregates, while concrete, bricks, and tiles serve as examples of building materials of the second type, which are called as “construction products.”

The legislation regulating radiation protection usually addresses “building materials” as a specific case of “construction products” and makes no distinction between “materials” and “products.” For example, Council Directive, 2013/59/EURATOM (2014) states that “building materials emitting radiation should be also regarded as construction products as defined in Regulation (EU) No. 305/2011, in the sense that the Regulation applies to construction works emitting dangerous substances or dangerous radiation.” At the same time, there is a clear division in the norms between building materials of the first type (sometimes called “constituents of building materials”) and those of the second type (finished products). For example, Council Directive, 2013/59/EURATOM (2014) defines the index relating to the gamma radiation dose, in excess of typical outdoor exposure, in a building constructed from a specified building material, while this index applies to the building material, not to its constituents except when those constituents are building materials themselves and are separately assessed as such. For application of the index to such constituents, in particular, residues from industries processing NORM recycled into building materials, Council Directive, 2013/59/EURATOM (2014) requires to apply an appropriate partitioning factor.

It is important to introduce these definitions and the nuances, related to overlapping and differences between the basic terms, that are used throughout the book at the start in order to make reading the book easy and smooth.

The book deals with chemical, technical, and radiological aspects that can influence the use of NORM by-products in building materials:

• First, the main parameters to be controlled are discussed (Chapter 3).

• Second, the legislative aspects are covered (Chapter 4).

• Third, the measurement methods are covered (Chapter 5).

• Then the properties of the by-products themselves are discussed (Chapter 6).

• In the next step construction materials based on NORM by-products are discussed (Chapter 7).

• Consecutively, an environmental leaching assessment of the construction materials is given (Chapter 8).

• Additionally, the nontechnical aspects are evaluated (Chapter 9).

• And finally, the conclusions and outlook are given (Chapter 10).