Use of Fly Ashes from Municipal Sewage Sludge Combustion In

Construction and Building Materials 188 (2018) 874–883

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Construction and Building Materials

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Use of ﬂy ashes from municipal sewage sludge combustion in production of ash concretes ⇑ Gabriela Rutkowska a, , Piotr Wichowski a, Joanna Fronczyk a, Małgorzata Franus b, Marek Chalecki a

a Faculty of Civil and Environmental Engineering, Warsaw University of Life Sciences—SGGW, Nowoursynowska 159, Warsaw 02-776, Poland b Civil Engineering and Architecture Faculty, Lublin University of Technology, Nadbystrzycka 40, 20-618 Lublin, Poland

highlights graphical abstract

Combustion ﬂy ashes of municipal sewage sludge party replacing cement. Impact of municipal sewage sludge on the strength and frost resistance of concrete. The results compared with those of concrete containing siliceous and calcareous ﬂy ashes. Assessment of heavy metals leachability.

article info abstract

Article history: Application of fly ashes from combustion of municipal sewage sludge (FAMSS) in the concrete technology Received 12 March 2018 realizes assumptions concerning the European Union’s waste management proposal. This study investi- Received in revised form 11 August 2018 gates the influence that a partial replacement of the Portland cement by these ashes would exercise on Accepted 25 August 2018 the strength parameters of concrete if compared to a reference concrete and concretes containing conventional admixtures in their composition, such as siliceous and calcareous fly ashes. Potential environmental impact of FAMSS application was investigated through the determination of heavy metals Keywords: leachability. Results conveyed that the concretes containing fly ashes from combustion of municipal sew- Concrete additive age sludge improved strength parameters and frost resistance as well as satisfied the environmental Fly ash Frost resistance requirements imposed on leaching of heavy metals. Heavy metals leaching Ó 2018 Elsevier Ltd. All rights reserved.

1. Introduction the earth’s surface or in underground mines [5]. In Europe, siliceous fly ashes produced in the combustion of hard coal are widely The idea to apply fly ashes in production of ordinary concrete is applied in the cement technology and even more so in concrete not new. Originally, it was used in the USA in 1930s [1–4]. Various technology. The re-use of this material allows the use of reduced sorts of coal and technologies related to its combustion or co- quantities of cement clinker, natural raw materials and mineral combustion recall formation of various fly ashes, like siliceous, fuels as well as the reduction of environmental pollution and emis- silica-calcareous or calcareous ashes. The combustion by- sion of carbon dioxide [6–8]. The clinker production process is

products in the professional power industry were disposed on associated with high emission of carbon dioxide (1 kg CO2 per 1 kg of produced clinker) as well as with high energy consumption needed for clinker roasting at the temperature of 1450 °C [9]. The ⇑ Corresponding author. carbon dioxide emission limits, imposed by the European Union E-mail addresses: [email protected] (G. Rutkowska), piotr_wichows- [10], prompt research on materials of new generation, containing [email protected] (P. Wichowski), [email protected] (J. Fronczyk), m.franus@ pollub.pl (M. Franus), [email protected] (M. Chalecki). lower quantities of clinker.

Wide application of fly ashes from coal combustion in the build- 2. Materials and methods ing construction is chiefly a result of: high fineness, close to that of cement; chemical constitution and phase composition; and reac- 2.1. Characteristics of fly ashes from municipal sewage sludge combustion tivity, in particular pozzolanic activity. Simultaneously, the fly The test procedures were based on the directives contained in the binding reg- ashes have a positive effect on some features of concrete, like com- ulations and EU standards. The investigations of FAMSS were carried out to identify pressive and bending strength [11–13]. These factors cause the their physical and chemical properties as this material is not currently widely used production of ash concretes to be attractive both for producers in the cement production. The grain size distribution analysis was carried out on the base of a laser diffrac- and for final consumers [14,15]. Concrete production in the EU in tion phenomenon in deionized water and in the presence of an ultrasonic probe, 6 3 2015 amounted to 266.9Á10 m . To produce such quantities of using the Mastersizer 3000 analyzer (Malvern Instruments). Grains with equivalent concrete, 128.1Á106 tons of cement and 7.86Á106 tons of admixtures diameters from the range 0.1Ä 1000 lm were analyzed. The morphology and were used. The most popular concrete was of class C25/30 – chemical composition were determined with use of the scanning electron micro- C30/37 (55.4%) and of thick-plastic (S2) to semi-liquid (S4) consis- scope SEM Quanta 250 FEG (FEI), equipped with an Energy Dispersive X-Ray Spec- troscopy (EDAX). À tency 74%. [16]. The oxide composition of the investigated fly ash was established with the In recent years, many investigations have been conducted method of energy dispersive X-ray fluorescence (XRF) on the Epsilon-3 spectrome- focusing on possibilities of application of fly ashes from combus- ter (Panalytical) with the Rh X-ray tube (9 W, 50 kV, 1 mA), 4096-channel spectrum tion of municipal sewage sludge (FAMSS) in the concrete technol- analyzer, 6 measuring filters (Cu-500, Cu-300, Ti, Al-50, Al-200, Ag) and the high- resolution solid state SDD detector (50 lm thick beryllium window), cooled with ogy [17–20]. Neutralization and recycling of sewage sludge, a Peltier’s cell. Powdered X-ray diffraction (XRD) test was carried out using a Pan- formed in sewage treatment plants, is a serious ecological problem. alytical X’pertPRO MPD X-ray diffractometer with the PW 3020 goniometer. As an The legal, binding regulations in Poland legislate the problem of X-ray radiation source, the copper tube was used (CuKa radiation, k = 1.54178 Å). the sewage sludge disposal on overfilled landfills more and more The data handling was performed with the help of the X’Pert Highscore software. severely and have introduced a ban on the disposal of wastes char- The identification of mineral phases was based on the PDF-2 Release 2010 database, formalized by JCPDS-ICDD. acterized by high calorific value, exceeding 6 MJ per one kilogram of dry mass [21]. Hence it seems that a target direction of the neu- 2.2. Preparation of concrete specimens tralization of sewage sludge in Poland is determined mainly by thermal methods of neutralization, considered to be ecologically The investigated concrete samples were designed as an ordinary concrete safe and economically justified [22,23]. Despite a significant reduc- according to European standards [37]. To perform the tests, concrete mixes of class tion in volume, up to 90%, of municipal sewage sludge, these meth- C20/25 and thick-plastic consistency F2 were designed. Constant granulometric composition of fine aggregates, selected in a sieve analysis, as well as of coarse ods have not yet been commonly applied to combustion of other aggregates, selected by consecutive iterations (Table 1), were maintained in all wastes [24–27]. One of possibilities of recycling the formed ashes samples. Composition of the mix was designed using the method of three equations is their use in the production of building materials, such as ordi- by Bukowski [38]. To prepare the concrete samples, a natural aggregate was used nary concrete [28], which generally increases the waste recycling with graining 0.125 Ä 16 mm, the CEM I 32.5 Portland cement as well as admix- – a more environmental friendly option of waste treatment than tures. As the mineral admixtures for the concrete mix, fly ashes from the fluidal combustion of municipal sewage sludge in the ‘‘Czajka” sewage treatment plant disposal [25,29]. (Warsaw) were used. The combustion was carried out in spring, in temperatures However, there are no implementations using ashes formed dur- above 850 °C. As reference materials, conventional siliceous fly ashes from hard coal ing sewage sludge combustion. The mass of sewage sludge pro- combustion in the ‘‘Siekierki” power plant (Warsaw) as well as calcareous fly ashes duced per annum in the 28 European member states decreased from brown coal combustion in the ‘‘Bełchatów” power plant were used. The temperature of coal combustion in the power plants did not exceed 550 °C. The fly from approximately 8.5 Mt dry mass in 2012 to 3.5 Mt dry mass ashes from the coal co-combustion met the requirements given by European stan- in 2015 [30]. According to the data of the Eurostat [30], the percent- dards [39]. To compare features of traditionally produced ordinary concretes and age of thermally conversed sewage sludge in EU took values of 25% features of the concretes containing combustion by-products in form of fly ashes and 37%, respectively. Application of this method of sewage sludge – siliceous and calcareous ones as well as ones formed in thermal conversion of disposal results in the production of significant quantities of fly municipal sewage sludge – four types of concrete samples were prepared: ashes, classified as waste code 19 01 14 [31], which should be 1. Concrete without admixtures – CON, appropriately recycled. According to the regulations binding in 2. Siliceous fly ash admixtured concrete – FAS, Poland [32], implementing the directive of the European Council 3. Calcareous fly ash admixtured concrete – FAC, [33] within their scope, insofar as the ashes produced during the 4. Concrete admixtured with fly ashes from combustion of municipal sewage sludge – FAMSS. combustion of sewage sludge satisfies defined requirements, they can be used to prepare concrete mixes for building construction, In the individual samples admixtured with fly ashes, 5%, 10% or 15% of a defined 3 excluding buildings designated for permanent residence of humans cement mass was replaced by the ashes. The concrete mix recipe per 1 m was established to comply with the assumption of ordinary concrete mix with use of or animals as well as for food production or storage. Recent exper- the method of three equations. Proportions of the concrete mix tested in the study imental studies suggest that the application of ashes from munici- are shown in Table 2. After forming, the samples were cured by immersion in tap pal sewage sludge combustion allows the obtaining of concrete water at 18 ± 2 °C [37]. parameters comparable to those for concrete produced on the basis of fly ashes from combustion or co-combustion of coal [34–36,27]. 2.3. Characteristics of concrete Standards and directives concerning the application of ashes In order to characterize properties of the obtained concrete mixes, the following from thermally conversed municipal sewage sludge as a mineral tests were performed: bulk density test (measurements of mass and volume), [40] raw material for production of building materials (concrete) on consistency test (concrete slump test) [41] and air content test (pressure method) the basis of cement have not been worked out so far. Due to a small [42]. The compressive strength tests were performed according to the guidelines number of studies and practical applications using such ashes, fur- contained in European standards [43]. The samples were tested after 28 and ther information on possibilities of their application is essential. 56 days of curing. The frost resistance test was performed with use of the direct method [44]. All tests were performed on the samples of the size The main objective of the performed investigations was the assess- 150 Â 150 Â 150 mm. The compressive strength tests were performed in the ment of possibilities of re-using ashes from municipal sewage H011 Matest hydraulic test machine, and the frost resistance tests in the Toropol sludge combustion, based on a comparative analysis of properties cold chamber. of a concrete mix and hardened concrete containing FAMSS as well The leaching tests were performed for three analysed fly ashes and for the concrete sample without admixtures (CON). In addition, the tests were performed for as siliceous and calcareous fly ashes, currently widely used in the three concrete samples admixtured with fly ashes where 15% of the cement mass concrete production. The obtained results were compared to the was replaced by individual types of fly ashes. The tests were performed for the sam- sample, not containing any fly ashes in its composition. ples with the highest percentage of fly ashes because it had been assumed that the 876 G. Rutkowska et al. / Construction and Building Materials 188 (2018) 874–883

Table 1 Composition of the aggregates selected by iterations in percentages.

Fraction Fraction mixing percentage ratio (for sand and gravel) Grain composition of I stage II stage III stage sand gravel 0.0–0.125 38 0.93 0.35 0.0125–0.25 17.82 6.77 0.025–0.50 39.62 15.06 0.50–1.0 34.32 13.04 1.0–2.0 7.31 2.78 2.0–4.0 32 62 19.84 4.0–8.0 45 68 18.97 8.0–16.0 55 23.19

Table 2 Concrete mix proportions by weight.

Specification Mass of concrete ingredients [kg/m3] Water Aggregate Cement Fly ash Concrete without admixtures 166.42 1900.74 360.58 0 Concrete admixtured with 5% of fly ash 166.42 1900.74 342.55 18.03 Concrete admixtured with 10% of fly ash 166.42 1900.74 324.52 36.06 Concrete admixtured with 15% of fly ash 166.42 1900.74 307.41 54.25

highest content of heavy metals in an eluate can be observed in these samples. In 20 Ä 50 mm (30.73% of the volume) and 50 Ä 100 mm (34.24%). addition, the concrete samples were mechanically crushed after the strength tests. For comparison, the content of finer particles (0.25 mm) in SSA, The obtained material was sieved to separate a fraction with graining under 4 mm. This granulate was dried to a constant mass and then was tested for heavy metals investigated by Kosior-Kazberuk [20], amounted to approximately 3 leachability according to the European standards [45]. Redistilled water (pH = 6.7, 7%. The FAMSS specific density amounted 1.826 kg/dm and the EC = 0.0286 mS/cm) was added to the granulate to obtain the liquid/solid phase bulk density 0.9457 kg/dm3. According Joshi and Lohtia [3], the proportion (L/S) = 100 ml per 10 g of solid. The samples were shaken in Elpin grain diameter fluctuates between 1 and 150 lm and is close to + water bath shaker type 357 for a period of 24 h with a speed of 200 rpm. The tests that of the cement grains. were performed in three repetitions in the temperature of 20 ± 2 °C. The obtained liquid was filtered through a 0.45 mm membrane filter and then the heavy metals Fig. 2 shows the scanning electron microscopy micrographs of content was determined (Cd, Cr, Cu, Ni, Pb, Zn, As, Sb, Se, Ba, Hg and Mo) with the FAMSS. It can be seen that the fly ash samples are predomi- use of the method of inductively coupled plasma atomic emission spectrometry nated by irregular grains with variable size and a strongly devel- in the ICP-AES Thermo Scientific iCAAP 6500 spectrometer (USA). The pH was mea- oped surface, showing a loose and rough structure of the sured with use of the CyberScan pH-510 pH-meter (Eutech Instruments), whereas electrical conductivity was measured with use of the CyberScan Con-510 conduc- material with high porosity. This may lead to higher water absorp- tometer (Eutech Instruments). Colour was determined with use of the DR 400 spec- tion connected to increased water demand of concrete containing trofotometer (Hach), turbidity with the 2100N IS turbidimeter, and salinity and dry SSA [19]. This finding is consistent to that of Alonso and Wesche mass content with the Sension 156 ionometer (Hach). Alkalinity, hardness and the [46], who state that the ash grains with the diameter over content of chlorides and sulphates were determined by titration with use of chem- 125 lm are highly porous and the Blaine number (SSA) of these ical reagents and digital burettes (Jencons Digitrate) with the accuracy ±0.01 ml. Ä 2 COD was determined in the Quick COD analyser (LAR). materials falls into the range 250 550 m /kg. As Malhotra and Ramezanianpour [4] demonstrated, the grain size and SSA of fly ashes is not associated with the source of its formation. Spherical 3. Results and discussion and cuboidal forms were very rare. Grains of fly ashes produced in coal combustion are usually spherical, but they also can be irreg- 3.1. Morphology and mineralogical analysis of FAMSS ular or angular [47]. Chemical micro-range analyses (SEM-EDS) showed diversification of the elementary composition. Grains con- The particle size distribution of the investigated fly ashes is taining silicon, aluminum, phosphorus and calcium were prevail- monomodal, with a maximum value of 100 mm(Fig. 1a). Grains ing (Fig. 3a), apart from them, grains containing silicon and with the diameter of 2 Ä 250 lm constitute over 91% of the total aluminum that also occurred (Fig. 3b). They are typical volume (Fig. 1b). The dominant grain fractions in this range are components of fly ashes, but significantly differing in morphology

Fig. 1. Particle size distribution curve and volume distribution of individual particle fractions in FAMSS. G. Rutkowska et al. / Construction and Building Materials 188 (2018) 874–883 877

Fig. 2. SEM images of ﬂy ashes from sewage sludge combustion magniﬁed 100 times (a) and 800 times (b).

Fig. 3. SEM images of FAMSS (a) along with EDS analysis (b).

(no spheroid shapes). Other components – sodium, magnesium, lower than that of the siliceous and calcareous fly ashes. The highest potassium, iron and titanium – occurred in minor quantities. percentage in the samples of the fly ashes from municipal sewage Results of the analysis on oxide composition and losses of igni- sludge combustion as well as the calcareous fly ashes concerned tion of the fly ashes from municipal sewage sludge combustion as the silica, aluminum dioxide and calcium oxide, whereas in the silic- well as the comparative materials – the siliceous and calcareous eous fly ash sample – silica and aluminum dioxide. Moreover, the

fly ashes – are presented in Table 3. The loss in ignition of the fly total content of the silica (SiO2), aluminum dioxide (Al2O3) and iron ashes from municipal sewage sludge combustion, expressed as oxide (Fe2O3) in the sewage sludge fly ashes was approximately two quantity of flammable substances in the sample, was significantly times lower than in conventional ashes and did not satisfy the 878 G. Rutkowska et al. / Construction and Building Materials 188 (2018) 874–883

Table 3 Oxide composition and losses in ignition for ﬂy ashes.

Component being determined Content [%] FAS FAC FAMSS Limit values for individual result [21] Loss in ignition 8.3 2.1 0.50 7% of category A, 9% of category B

SiO2 49.3 42.8 17.80 –

Fe2O3 5.2 4.4 6.50 –

Al2O3 27.8 20.5 11.10 – total 2 Ä 4 82.32 67.7 35.40 total min. 65% CaO 2.0 22.52 18.88 – MgO 1.6 0.9 2.44 max. 4.0%

TiO2 2.1 1.3 0.80 –

SO3 0.4 4.3 3.10 max. 3.5%

Na2O 0.6 0.1 0.32 max. 5%

K2O 0.2 0.2 1.21 –

P2O5 0.5 0.2 18.21 –

requirements contained in the standards [39] which, on the other The XRD pattern of the FAMSS is shown in Fig. 4. Quartz and hand, concern siliceous fly ashes produced in combustion of coal anhydrite are predominant in the mineral composition of these or co-combustion of coal and other wastes. The pozzolanic activity fly ashes; they were recognized by characteristic interplanar dis- of fly ashes depends on the content of SiO2,Al2O3 and CaO tances dhkl (4.25; 3.34; 2.23; 2.04 Å for quartz and 3.49; 2.84; [46,22,48], while according to Camões, reduction of quantity of 2.33; 2.21 Å for anhydrite). However, the content of SO3 (Table 3) these ingredients does not worsen features of concrete mix and is relatively low, so the high intensity of some anhydrite peaks hardened concrete [2]. The siliceous fly ashes can be applied in may be a consequence of the phenomenon of coincidence con- the concrete production only if the requirements given in the indus- nected with apatite and fluoroapatite lines. The mineral composi- try standard [39] are satisfied. According to these requirements, the tion of these ashes is supplemented by phosphates occurring in total content of SiO2,Fe2O3 and Al2O3 should not fall below 65% by form of apatite and fluorapatite. The first one can be recognized weight, including the content of the reactive SiO2 higher than 25% by the highest peaks dhkl = 3.40; 2.77; 2.69; 2.61 Å, whereas the by weight. The content of the reactive CaO should not exceed 10%, second one – by the peaks dhkl = 3.43; 2.81; 2.77; 2.70 Å. These MgO À 4%, and the total content of alkalis, calculated as the content mineral phases are mainly solid supports of P2O5, existing in higher of Na2O (equivalent) should not exceed 5% by weight. The content of quantities than in conventional ashes. the soluble phosphate (P2O5) should not exceed 100 mg/kg. It was also observed that the content of phosphates was several 3.2. Physical properties of concrete mixes times higher than it is in conventional ashes. This is due to the fact that the phosphorus is removed from sewage which cumulates in Based on the performed investigations of the concrete mix den- sewage sludge. Fly ashes from municipal sewage sludge combus- sity, it has been stated that the values for individual samples were tion, rich in phosphorus compounds, were also investigated by close to each other and fell into the range of 2310 Ä 2376 kg/m3, Tarko and Gorazda [49]. As stated by Williams [50], losses in igni- analogically to standard results for ordinary concretes tion and P2O5 content can affect concrete strength development (2000 Ä 2600 kg/m3). The consistency determined in the concrete dynamics. It is supposed that the presence of phosphate ions can slump test was classified as thick-plastic for all samples containing cause a slow increase of strength of the concretes containing fly fly ashes. The highest air content, equal to 3.8%, was noticed in the ashes from co-combustion due to delay in a cement hydration pro- FAMSS mix, whereas the lowest, equal to 2.4% was in the FAS mix. cess, however, a diversified chemical composition of fly ashes However, the European standards [37] do not place any demands (Table 3) allows the production of ash concretes that satisfy stan- on minimum or maximum air content for the concrete with X0 dard strength requirements. exposition class. Monzo et al. [51] described the influence of fly

Fig. 4. XRD pattern of FAMSS. G. Rutkowska et al. / Construction and Building Materials 188 (2018) 874–883 879 ashes from sewage sludge combustion on the workability of fresh if no more than 15% of cement is replaced by the fly ashes from mortar, tested on the base of changes in spreading. They stated thermal conversion of sewage sludge, it does not affect the mortar that if cement is partially replaced by fly ashes then the mortar strength negatively. In the application of additional measures, for workability decreases. This can be explained by an irregular form example, wet grinding of ash before its introduction into a mortar of ash grains and a high water demand of particles with developed or curing of samples at a higher temperature, the ash content can area. In practical applications, it is suggested to use be increased to 30% of a binder mass [34]. Moreover, according superplasticizers. to Fontes and Barbosa [34], fly ashes from sewage sludge can be According to Baeza- Brotons, the FAMSS showed lower poz- successfully applied as an active agent in a raw material blend zolanic activity (ca. 92%) than the coal fly ash (97%). Nevertheless, for the cement production. The chemical composition (silica, iron, they reached the required values (75%) that allowed them to be calcium, aluminum, magnesium, phosphorus and oxygen), as well classified as an active mineral agent. The FAMSS inhibit the binding as hydraulic and pozzolanic properties of these ashes, used as a process and hardening of cement composites, whereas the mineral substitute of the Portland cement in concretes, show analogies agent allows maintaining the initial fluid consistency of fresh mor- with traditional mineral agents [35]. Monzó et al. [51] showed that tar for a significantly longer time as compared to the cement mor- a mortar containing 15% of fly ashes was characterized by a com- tars [52]. Application of ash as a partial substitute of cement in a pressive strength comparable to that of a conventional mortar, concrete requires an elongated curing time, advised in certain whereas the content no higher than 30% caused the increase of dif- applications, or in the introduction of binding catalysts. The ability ferences in hydraulic properties of the mortar. Chang et al. [53] also to maintain initial features of fresh mortar for a longer time can be confirmed in their investigations that an addition of fly ashes from used in works organization (increase in the distance over which sewage sludge affects the increase of water absorbability of build- the mix can be transported to a construction site). ing materials. Addition of fly ashes caused the decrease of workability and compressive strength of the obtained material. The 3.3. Mechanical properties of concrete most advantageous results were obtained by 10% of ash introduced in a mix. Similar results were obtained in the authors’ own inves- 3.3.1. Compressive strength tigations, in which the compressive strength of the concrete with Measurements of average compressive strength of the concrete 10% addition of fly ashes from sewage sludge (FAMSS 10%) samples with variable fly ash content are show in Fig. 5, where the achieved higher values than for the samples containing 5% and standard deviations and variability coefficients are also marked. 15% of these ashes. Moreover, the compressive strength of this The highest compressive strength after 28 days of curing, equal sample was lower relative to the strength of the sample with to 47.4 MPa, was obtained by the concrete samples where 15% of 15% of cement replaced by the siliceous fly ash. According to infor- cement was replaced by the siliceous fly ash (FAS 15%), whereas mation given by other authors, the optimum content of fly ashes the lowest, equal to 35.4 MPa – by the samples where 5% of cement from sewage sludge in cement materials amounts from 5% to was replaced by the calcareous fly ash (FAC 5%). If compared to the 20% [54,55]. Chen et al. [17] analyzed the possibilities of applica- reference concrete, the increase in strength for the FAS 15% tion of ashes as a substitute of cement and/or sand in building amounted to 14.8%, whereas the decrease for the FAC 5% amounted materials, taking both technical and environmental criteria into to 14.3%. The highest compressive strength after 56 days of curing consideration. The mortar and concrete produced by partial was obtained by the concrete samples with the siliceous fly ash replacement of cement and sand by ashes showed lower bending (FAS 15%), whereas the lowest was obtained by the samples with and compressive strength than that of traditional hollow bricks. the calcareous fly ash (FAC 15%). The exchange of cement for the It was also confirmed that a mortar containing 10% of ash has com- FAMSS affected the increase in compressive strength in compar- pressive strength similar to conventional mortars. It must be noted ison to the reference concrete. The results of compressive strength that variability of composition and graining hinders common tests for the concretes after 28 and 56 days of curing presented low application of ashes as active concrete agents. The presence of variability coefficients, amounting to less than 5% for all tested ashes equal to 25% of cement mass causes a delay in binding of a samples. cement slurry, and causes slow increase of compressive strength The majority of investigations presented in the literature con- of mortars and concretes in comparison to composites made only cern the influence of the addition of fly ashes on strength proper- with use of the Portland cement. However, by extending the curing ties, which are the basic features determining their technical time, it is possible to achieve the strength required for constructive usefulness [51,52], of mortars and concretes. It has been stated that concretes [20].

Fig. 5. Compressive strength after 28 and 56 days of curing. 880 G. Rutkowska et al. / Construction and Building Materials 188 (2018) 874–883

Table 4 Average decrease in strength and average loss in mass of samples subjected to freezing.

Sample Average compressive strength Extended uncertainty for samples Average strength Average mass Average Up decrease of frozen loss in samples mass of reference after 150 freeze– of reference after 150 freeze– before after 150 freeze– sample thaw cycles sample thaw cycles freezing thaw cycles [MPa] [MPa] [MPa] [MPa] [%] [g] [g] [%] CON 41.3 42.5 1.2 1.0 +2.90 2366 2362 0.169 FAS 5% 45.8 39.6 1.1 1.0 À13.53 2416 2409 0.289 FAS 10% 47.7 36.1 2.0 1.9 À24.31 2361 2342 0.804 FAS 15% 50.0 35.1 1.9 2.0 À29.80 2329 2331 0.086 FAC 5% 41.2 36.7 1.6 1.4 À10.92 2378 2372 0.252 FAC 10% 41.8 40.2 1.5 1.9 À3.83 2363 2357 0.254 FAC 15% 47.4 45.1 1.7 2.0 À4.85 2345 2342 0.128 FAMSS 5% 42.5 39.0 1.6 2.0 À8.23 2405 2397 0.333 FAMSS 10% 43.4 42.6 1.8 2.0 À1.84 2395 2390 0.209 FAMSS 15% 50.0 49.1 2.3 1.5 À1.80 2352 2350 0.085

3.3.2. Frost resistance were compared to the permissible values of leachability constitut- Frost resistance tests determine how low compressive strength ing a criterion passing wastes as fit for storage on dumps of a given falls in a frozen sample relative to a non-frozen one. The compres- type [21,60]. sive strength decrease should not be greater than 20%. According to According to the binding regulations in Poland [32], imple- the Polish standards [56], frozen samples cannot have cracks and menting the EU directive [33], FAMSS can be used to prepare con- loss in mass cannot exceed 5%. Table 4 presents the compressive crete mixes if a heavy metal concentration in water eluates from strength results for the reference samples and the samples sub- tests of elution for concrete samples does not exceed 10 mg/l in jected to 150 freeze-thaw cycles. total, after conversion into mass of elements. The total concentra- In case of the reference samples, the highest compressive tion of heavy metals in eluate estimated for siliceous fly ash was strength characterized the FAS 15% and FAMSS 15% concretes. The equal to 1.736 mg/l, for calcareous fly ash, 1.580 mg/L and for fly average compressive strength amounted 50.0 MPa, whereas the ash from sewage sludge fly ash, and 0.587 mg/L, whereas for lowest strength (41.2 MPa) was observed in the FAC 15% concrete. CON 15%, 1.206 mg/l, for FAS 15%, 0.789 mg/l, for FAC 15%, Considering the compressive strength after 150 freeze–thaw cycles, 0.497 mg/l and for FAMSS 15%, 1.167 mg/l were estimated. If a one can notice that the highest compressive strength was observed metal concentration was under the determination limit, then min- in the samples that contained 15% ashes from combustion of imum determinable value was assumed for calculation of total municipal sewage sludge (FAMSS 15%), as in the case of the refer- values. The concentration in any sample did not exceed the per- ence sample. The average compressive strength here amounted to missible value. 49.1 MPa. The lowest compressive strength after 150 freeze–thaw Based on the list, one can state that, in the case of the siliceous cycles was observed for the concrete that contained 15% siliceous and calcareous ashes, the heavy metals leachability was signifi- ash (FAS 15%) – 35.1 MPa. The average loss in strength of the sam- cantly higher than the leachability for concrete samples containing ples subjected to freezing in any case did not exceed 20%. The low- these ashes. For the ashes from thermal conversion of municipal est loss in strength was observed for the FAMSS sample that sewage sludge, the leachability for the ash was lower than for con- contained 15% ashes from combustion of municipal sewage sludge, crete samples containing this ash but did not exceed the limit val- whereas the highest – for the FAS 15% sample that contained 15% ues assumed for inert wastes. For the three types of the analyzed siliceous ash. The values amounted to 1.80% and 29.80%, respec- ashes, the content of Cr, Cu and Ba in eluate was measured, in addi- tively. In the case of the reference concrete, the strength increase tion to the content of Mo for the calcareous ash. In all cases, the was observed after 150 freeze–thaw cycles. The average loss in leachability for the ash concrete samples is comparable to or lower mass after 150 freeze–thaw cycles was minor and varied from than this for the samples without ash. The lowest leachability of 0.085% for the FAS 15% sample to 0.333% for the FAMSS 15% sample. heavy metals was observed for the siliceous ash. For the two The samples used in this test were subjected to 150 freeze–thaw remaining ash types, the leachabilities of the majority of metals cycles as well as exposed water action, thus they can be assigned were comparable. Some exceptions include Sb and Se, whose con- the frost resistance level F150. The ash concretes containing the centration in the eluate from the ashes from municipal sewage fly ashes from thermal conversion of municipal sewage sludge were sludge was higher, as well as Cr and Ba, whose leachability was characterized by the highest frost resistance. higher for the calcareous ash. Moreover, the concentrations of The concrete compressive strength plays an essential role in the analyzed heavy metals in the eluates for all three ashes were design, workmanship and exploitation of constructions. High qual- lower than the limit values for inert wastes. The study of leachability of results obtained in the aforementioned tests are important ity of trace elements for hardened mortars and concretes con- for a proper evaluation. ducted by Monzó and Paya [51] also showed that the ash According to PN-EN ISO/IEC 17025 and the ISO procedure, a non- recycling consisting replacement of 30% of Portland cement by scaled sclerometric method of evaluation of extended (total) uncer- ashes did not threaten the safety of the natural environment. Chen tainty of measurement results up was applied for the obtained et al. [17] demonstrated that among potential pollutants only Mo results [57–59]. For the samples being tested, high heterogeneity and Se were eluted in concentrations exceeding limit values. On was obtained, varying1.0 MPa for the reference concrete samples the other hand, the leachability tests performed on monolithic con- (CON) and 2.3 MPa for the FAMSS 15% concrete samples. cretes showed that the concentration of pollutants, including Mo and Se, did not exceed the limits imposed by the US Environmental 3.4. Leachability Protection Agency. Hence, taking technical specification and environmental standards into consideration, one can state that the Tables 5 and 6 show the results of chemical analysis of eluates application of ashes from sewage sludge in building materials of the analyzed ashes and concrete samples. The obtained results seems to be possible [17]. G. Rutkowska et al. / Construction and Building Materials 188 (2018) 874–883 881

Table 5 Comparison of elution values of heavy metals with the values required for storage at landﬁll of a given type.

Sample Heavy metals [mg/l] Cd Cr Cu Ni Pb Zn As Sb Se Ba Hg Mo CON: C1 <0.002 0.013 0.013 <0.005 <0.003 <0.030 <0.010 <0.010 <0.010 1.18 <0.005 <0.010 SD2 0.003 0.004 0.26 U3 0.003 0.004 0.23 FAS: C <0.002 <0.01 0.004 <0.005 <0.003 <0.030 <0.010 <0.010 <0.010 1.71 <0.005 0.022 SD 0.001 0.25 0.008 U 0.001 0.23 0.007 FAC: C <0.002 0.012 0.008 <0.005 <0.003 <0.030 <0.010 <0.010 <0.010 1.52 <0.005 0.04 SD 0.002 0.003 0.230.210 0.008 U 0.002 0.003 0.007 FAMSS C <0.002 <0.010 0.008 <0.005 <0.003 <0.030 <0.010 0.02 0.047 0.112 <0.005 0.4 SD 0.005 0.006 0.009 0.029 0.097 U 0.004 0.005 0.008 0.026 0.087 FAS %: C <0.002 0.018 0.008 <0.005 <0.003 <0.030 <0.010 <0.010 <0.010 0.76 <0.005 <0.010 SD 0.006 0.002 0.15 U 0.005 0.002 0.13 FAC %: C <0.002 0.017 0.011 <0.005 <0.003 <0.030 <0.010 <0.010 <0.010 0.45 <0.005 0.023 SD 0,005 0.003 0.06 0.007 U 0.005 0.003 0.05 0.007 FAMSS %: C <0.002 0.016 0.011 <0.005 <0.003 <0.030 <0.010 <0.010 <0.010 1.14 <0.005 <0.010 SD 0.005 0.003 0.12 U 0.004 0.002 0.11 Limit of elution by passing wastes as ﬁt for storage [26,58] Inert waste 0.04 0.5 2 0.4 0.5 4 0.5 0.06 0.1 20 0.01 0.5 Other waste than inert and hazardous 1 10 50 10 10 50 2 0.7 0.5 100 0.2 10 Hazardous waste 5 70 100 40 50 200 25.00. 5 7 300 2 30

1C – concentration, 2 SD – standard deviation, 3U – external uncertainty, the uncertainty of the method was deﬁned as extended uncertainty. Expansion factor k = 2, conﬁdence level – 95%.

The results of chemical and physical tests of the eluates are 4. Conclusions gathered in Table 6. The eluates of all analyzed materials were characterized by high pH values, which is possibly related to Trends in treatment of municipal sewage sludge in Europe indi- the presence of oxides in the samples content. The lowest pH cate that thermal neutralization is increasingly applied. Despite a was observed for the sample containing the FAMSS. This is prob- significant reduction of the volume of waste being produced for ably due to the lower silica content in these ashes [61]. More- this process, it is necessary to work out methods of recycling. Fly over, this material showed the lowest values of remaining ashes from combustion of municipal sewage sludge can constitute physical and chemical parameters as well. The results of analysis a quality component used in concrete production. Based on the of COD in the eluates are different from those obtained by Bar- obtained results, one can state that the concrete containing these bosa et al. [62], who showed that the COD in eluates from the fly ashes is characterized by a comparable compressive strength ash from combustion of municipal sewage sludge assumed relative to the siliceous ash concrete and higher than the strength higher values. The observed differences can result from applied of the reference concrete and calcareous ash concrete. The content incineration technologies, the first of which being temperature, of the fly ashes from combustion of municipal sewage sludge, not as well as sewage sludge content. The highest values of electrical exceeding 10%, has resulted in an increase of the compressive conductivity, chloride concentration, color, turbidity, phenolph- strength, related to the reference concrete. The increase of the con- thalein alkalinity, TDS-hardness, salinity and COD were observed tent of this ash to 15% resulted in slight reduction of this parame- in the siliceous ash eluate, whereas total alkalinity and sulfides ter, however the compressive strength was still higher than that of content were observed in the calcareous ash eluate. The the sample without ash. The tests also showed that the analyzed exchange of the 15% of Portland cement by ashes did not affect concretes are frost-resistant. The concrete containing the ash from the pH of the eluate, but increased color, turbidity, total alkalin- municipal sewage sludge has achieved the best strength parame- ity and COD as well as reduced phenolphthalein alkalinity and ters after 150 freeze-thaw cycles. Along with increase of the con- hardness. Moreover, lower values of salinity, electrical conduc- tent of ashes from municipal sewage sludge within the range of tivity and TDS-hardness were observed in all eluates, despite 5–15%, lower reductions in compressive strength were observed. the fact that the chloride concentration in the FAC 15% and For the samples being tested, high non-homogeneity was FAMSS 15% samples as well as the sulfide concentration in the obtained, falling into the range between 1.0 MPa (for the reference FAMSS 15% samples increased. concrete samples – CON) and 2.3 MPa (for the FAMSS 15% concrete 882 G. Rutkowska et al. / Construction and Building Materials 188 (2018) 874–883

Table 6 Chemical and physical parameters of eluates.

Parameter FAS FAC FAMSS CON FAS 15% FAC 15% FAMSS 15% pH Value 12.17 12.17 9.75 12.29 12.26 12.25 12.19 SD1 0.05 0.05 0.08 0.12 0.03 0.04 0.04 U2 0.05 0.05 0.07 0.11 0.03 0.04 0.04 Conductivity [mS/cm] Value 5.08 4.54 2.33 7.86 7.34 6.69 6.61 SD 0.11 0.23 0.14 0.23 0.22 0.28 0.15 U 0.1 0.2 0.13 0.21 0.2 0.25 0.13 Chlorides [mg/l] Value 90.6 48.1 7.8 61.4 49.8 72.4 76.8 SD 2.92 1.36 1.4 3.02 2.39 2.46 2.81 U 2.61 1.22 1.25 2.7 2.14 2.2 2.51 Sulﬁdes [mg/l] Value nd3 6ndndndnd7 SD 1.14 0.83 U 1.02 0.75 Color [mgPt] Value 143 138 24.3 17.5 24.95 32.2 36 SD 7.07 6.44 1.84 1.49 2.96 1.87 1.2 U 6.32 5.76 1.65 1.33 2.64 1.67 1.08 Turbidity [NTU] Value 50.8 24.8 15.97 3.42 5.55 4.76 6.73 SD 3.13 2.88 1.56 0.49 0.4 0.26 0.69 U 2.8 2.57 1.4 0.44 0.35 0.23 0.62 Total alkalinity [mval/l] Value 1.24 2.52 1.76 1.4 1.92 2.36 1.64 SD 0.17 0.24 0.15 0.15 0.31 0.29 0.25 U 0.15 0.22 0.13 0.13 0.27 0.26 0.22 Phenolphtalein alkalinity Value 26.52 22.96 1.08 39.24 37.48 34.04 33.12 SD 2.71 2.92 0.19 1.65 2.02 2.78 2.14 U 2.42 2.61 0.17 1.48 1.81 2.49 1.91 Hardness [oT] Value 36.26 52.04 4264 70.42 41.06 54.5 49.24 SD 2.5 2.91 2.65 4.96 3.4 3.51 2.65 U 2.24 2.61 2.37 4.44 3.04 3.14 2.37 Dry mass – TDS [g/l] Value 2.44 2.19 1.09 3.9 3.55 3.26 3.18 SD 0.43 0.34 0.15 0.36 0.28 0.28 0.24 U 0.38 0.31 0.13 0.32 0.25 0.25 0.21 Salinity (sal) [%] Value 2.6 2.35 1.1 4.25 3.95 3.55 3.45 SD 0.33 0.33 0.29 0.19 0.26 0.36 0.32 U 0.3 0.29 0.26 0.17 0.24 0.33 0.29

COD [ mgO2/l] Value 23.9 20 17 33.5 37.3 133 40 SD 0.49 0.99 1.64 0.85 2.88 3.15 3.61 U 0.44 0.89 1.47 0.76 2.57 2.82 3.23

1SD – standard deviation, 2U – external uncertainty, the uncertainty of the method was defined as extended uncertainty. Expansion factor k = 2, confidence level – 95%, 3nd – not detected. samples). Moreover, the tests have shown different chemical com- References position of the ashes from thermal conversion of sewage sludge in relation to the siliceous and calcareous ashes. Nevertheless, there [1] A.C.I. Committee, 232, Use of Fly Ash in Concrete ACI 232.2R- 03, American Concrete Institute, Farmington Hills, Michigan, 1996. are no regulations which would limit the possibility of application [2] A. Comões, High performance concrete incorporating fly ash (PhD Thesis), of these ashes in the concrete production concerning chemical and University of Minho, Portugal, 2002 (in Portuguese). physical properties of ashes produced in the combustion of sewage [3] R.C. Joshi, R.P. Lohtia, Fly ash in concrete – Production, properties and uses, sludge. The total concentration of heavy metals eluted from the Gordon and Breach, Amsterdam, 1997. [4] V.M. Malhotra, A.A. Ramezanianpour, Fly Ash in Concrete, second ed., CANMET FAMSS as well as from the concrete samples containing these ashes Natural Resources, Canada, Ottawa, 1994. shows the possibility of its application in the concrete production [5] E. Koda, P. Osin´ ski, Slope erosion control with the use of fly-ash and sewage from an environmental point of view. However, it is associated sludge Land Reclam, Ann. Warsaw Univ. Life Sci. – SGGW 43 (2) (2011) 101– 111, https://doi.org/10.2478/v10060-008-0096-0. with higher concentrations obtained for the concrete samples con- [6] J. Deja, B. Antosiak, Degree of progress of the fly ash reaction in alkali-activated taining the siliceous and calcareous ashes. fly-ash binders, Cem. Lime Concr. 17 (79) (2012) 67–76. [7] S. Yadav, S. Agnihotri, S. Gupta, R.K. Tripathi, Incorporation of STP sludge and fly ash in brick manufacturing: an attempt to save the environment, IJOART 3 Conflict of interest (5) (2014) 138–144. [8] P. Wichowski, G. Rutkowska, P. Nowak, Elution of selected heavy metals from concretes containing ashes produced in thermal conversion of sludge, Acta Sci. None. G. Rutkowska et al. / Construction and Building Materials 188 (2018) 874–883 883

Pol. Architectura 16 (1) (2017) 43–51. https://doi.org/10.22630/ASPA.2017.16. [34] C.M.A. Fontes, M.C. Barbosa, R.D. Toledo Filho, J.P. Goncalves, Potentiality of 1.05. sewage sludge ash as mineral additive in cement mortar and high performance [9] T. Markiv, K. Sobol, M. Franus, W. Franus, Mechanical and durability properties concrete, in: Intern. RILEM Confe. on the Use of Recycled Materials in Buildings of concretes incorporating natural zeolite, Arch. Civ. Mech. Eng. 16 (2016) 554– and Structures, 2004, pp. 797–806. 562, https://doi.org/10.1016/j.acme.2016.03.013. [35] R.O. Yusur, Z.Z. Noor, M.D.F.M.D. Din, A.H. Abba, Use of sewage sludge ash [10] W. Ke˛pys, R. Pomykała, J. Pietrzyk, Properties of fly ash from thermal (SSA) in the production of cement and concrete-a review, IJGEnvI 12 (2) (2012) conversion of municipal sewage sludge, J. Polish Mineral Eng. Soc. 14 (1) 214–228, https://doi.org/10.1504/IJGENVI.2012.049382. (2013) 11–18. [36] G. Rutkowska, P. Wichowski, K. S´wigon´ , P. Sobieski, Properties of concrete with [11] S.M. Gupta, Support vector machines based modelling of concrete strength. fly ash addition from sewage sludge thermal treatment, Cem. Lime Concr. 2 Engineering and technology, Int. J. Intell. Technol. 3 (1) (2007) 12–18. (2017) 113–119. [12] J.I. Kim, D.K. Kim, M.Q. Feng, F. Yazdani, Application of neural networks for [37] EN 206+A1:2016-12 Concrete. Part 1. Requirements, Properties, estimation of concrete strength, J Mater. Civ. Eng. 16 (3) (2004) 257–264. Manufacturing and Conformity. 10.1061(ASCE)0899-1561. [38] Z. Jamrozy,_ Concrete and its Technologies, PWN, Warsaw, 2015 (in Polish). [13] S. Lai, M. Serra, Concrete strength prediction by means of neural network, [39] EN 450-1: 2012, Fly-ashes for concrete. Part1: Definitions, specifications and Constr. Build. Mater. 11 (2) (1997) 93–98, https://doi.org/10.1016/S0950-0618 conformity criteria. (97)00007-X. [40] EN 12350-6:2011, Testing of fresh concrete. Part 6: Density. [14] M. Saridemir, Prediction of compressive strength of concretes containing [41] EN 12350-2:2011, Testing of fresh concrete. Part 2. Slump test. metakaolin and silica fume by artificial neural networks, Adv. Eng. Software 40 [42] EN 12350-7:2011, Testing of fresh concrete. Part 7: Air content - pressure (2009) 350–355, https://doi.org/10.1016/j.advengsoft.2008.05.002. method. [15] I.B. Topcu, M. Saridemir, Prediction of compressive strength of concrete [43] EN 12390-3:2011, Testing of hardened concrete. Part 3. Compressive strength containing fly ash using artificial neural networks and fuzzy logic, Comput. of test specimens. Mater. Sci. 41 (2008) 305–311, https://doi.org/10.1016/ [44] PN-B-06265:2004, Polish National Supplement PN-EN 206-1:2003 ‘‘Concrete. j.commatsci.2007.04.009. Part 1. Requirements, Properties, Manufacturing and Conformity. [16] Ready-mixed concrete industry statistics, year 2015 – ERMCO, draft 2016. [45] EN 12457-2: 2006, Characterization of waste – Leaching – Compliance test for [17] M. Chen, D. Blanc, M. Gautier, J. Mehu, R. Gourdon, Environmental and leaching of granular waste materials and sludges – Part 2: One stage batch test technical assessments of the potential utilization of sewage sludge ashes at a liquid to solid ratio of 10 l/kg for materials with particle size below 4 mm (SSAs) as secondary raw materials in construction, Waste Manage. (Oxford) 33 (without or with size reduction). (5) (2013) 1268–1275, https://doi.org/10.1016/j.wasman.2013.01.004. [46] J.L. Alonso, K. Wesche, Characterization of Fly Ash. Fly ash in concrete: [18] Z. Chen, C.S. Poon, Comparative studies on the effects of sewage sludge ash and Properties and Performance Rilem Report 7, E&FN Spon, London, 1991. fly ash on cement hydration and properties of cement mortars, Constr. Build. [47] P. Kunecki, R. Panek, M. Wdowin, W. Franus, Synthesis of Faujasite (FAU) and Mater. 154 (2017) 791–803, https://doi.org/10.1016/ Tschernichite (LTA) type zeolites as a potential direction of the development of j.conbuildmat.2017.08.003. lime class C fly ash, Int. J. Miner. Process. 166 (2017) 69–78, https://doi.org/ [19] C.J. Lynn, R.K. Dhir, G.S. Ghataora, R.P. West, Sewage sludge ash characteristics 10.1016/j.minpro.2017.07.007. and potential for use in concrete, Constr. Build. Mater. 98 (2015) 767–779, [48] A.J. Tenza-Abril, J.M. Saval, A. Cuenca, Using sewage-sludge ash as filler in https://doi.org/10.1016/j.conbuildmat.2015.08.122. bituminous mixes, J. Mater. Civ. Eng. 27 (4) (2014) 1–9, https://doi.org/ [20] M. Kosior-Kazberuk, Application of SSA as partial replacement of aggregate in 10.1061/(ASCE)MT.1943-5533.0001087. concrete, Pol. J. Environ. Stud. 20 (2011) 365–370. [49] B. Tarko, K. Gorazda, Z. Wzorek, A.K. Nowak, Z. Kowalski, J. Kulczycka, A. [21] EC/2003/33 Council Decision of 19 December 2002 establishing criteria and Henclik, Recovery of phosphorus from industrial sewage sludge ashes, Przem. procedures for the acceptance of waste at landfills pursuant to Article 16 of Chem. 93 (6) (2014) 1041–1044, https://doi.org/10.12916/ Annex II to Directive 1999/31/EC (Special edition in Polish: Chapter 15 Volume przemchem.2014.1041. 007 P.314-336). [50] P.T. Williams, Waste Treatment and Disposal, second ed., John Wiley & Sons, [22] Kosior-Kazberuk, New mineral additions for concrete, Civ. Environ. Eng. 2 (1) Chichester, 2005. (2011) 47–55. [51] J. Monzó, J. Paya, M.V. Borrachero, I. Girbes, Reuse of sewage sludge ashes (SSA) [23] K. S´roda, A. Kijo-Kleczkowska, H. Otwinowski, Thermal disposal of sewage in cement mixtures: the effect of SSA on the workability of cement mortars, sludge, Ecol. Ing. 28 (2012) 67–81 (in Polish). Waste Manage. (Oxford) 23 (4) (2003) 373–381, https://doi.org/10.1016/ [24] E. Agbor, X. Zhang, A. Kumar, A review of biomass co-firing in Nirth America, S0956-053X(03)00034-5. Renew. Sustain. Energy Rev. 40 (2014) 930–943, https://doi.org/10.1016/j. [52] F. Baeza-Brotons, P. Garces, J. Paya, J.M. Saval, Portland cement systems with rser.2014.07.195. addition of sewage sludge ash. Application in concretes for the manufacture of [25] Z. Chen, J.S. Li, C.S. Poon, Combined use of sewage sludge ash and recycled blocks, J. Clean. Prod. 82 (2014) 112–124, https://doi.org/10.1016/j. glass cullet for the production of concrete blocks, J. Clean. Prod. 171 (2018) jclepro.2014.06.072. 1447–1459, https://doi.org/10.1016/j.jclepro.2017.10.140. [53] F. Chang, J. Lin, C. Tsai, K. Wang, Study on cement mortar and concrete made [26] A. Magdziarz, M. Wilk, M. Gajek, D. Nowak-Wozńy, D. Kopia, I. Kalemba-Rec, J. with sewage sludge ash, Water Sci. Technol. 62 (7) (2010) 1689–1693, https:// A. Kozin´ ski, Properties of ash generated during sewage sludge combustion: a doi.org/10.2166/wst.2010.459. multifaceted analysis, Energy 113 (2016) 85–94, https://doi.org/10.1016/j. [54] C. Ferreira, A. Ribeiro, L. Ottosen, Possible applications for municipal solid energy.2016.07.029. waste fly ash, J. Hazar. Mater. 96 (2) (2003) 201–216, https://doi.org/10.1016/ [27] P. Wichowski, T. Rozbicki, Investigations of re-hydration increase of dried S0304-3894(02)00201-7. sludge Land Reclam, Ann. Warsaw Univ. Life Sci. – SGGW 25 (2) (2013) 227– [55] L. Yenc, D.H. Tseng, T.T. Lin, Characterization of eco-cement paste produced 234, https://doi.org/10.2478/sggw-2013-0019. from waste sludges, Chemosphere 84 (2) (2011) 220–226, https://doi.org/ [28] G. Rutkowska, K. Wisńiewski, M. Chalecki, M. Górecka, M. Miłosek, Influence of 10.1016/j.chemosphere.2011.04.050. fly-ashes on properties of ordinary concretes Land Reclam, Ann. Warsaw Univ. [56] PN-88/B-06250: Ordinary concrete. Life Sci. – SGGW 48 (1) (2016) 79–94, https://doi.org/10.1515/sggw-2016- [57] EN ISO/IEC 17025:2005, General requirements for the competence of testing 0007. and calibration laboratories. [29] M. Franus, G. Józefaciuk, L. Bandura, K. Lamorski, M. Hajnos, W. Franus, [58] Guide to the Expression of Uncertainty Measurement, ISO 1993 À in Polish Modification of lightweight aggregates’ microstructure by used motor oil Translation, GUM, Warsaw, 1995. addition, Materials 9 (2016) 845, https://doi.org/10.3390/ma9100845. [59] L. Brunarski, M. Dohojda, An approach to in-situ compressive strength of [30] Eurostat, Eurostat Database: sewage sludge production and disposal from concrete, Bull. Polish Acad. Sci. – Tech. Sci. 64 (4) (2016) 687–695, https://doi. urban wastewater, http://ec.europa.eu/eurostat/tgm/table.do?tab=table& org/10.1515/bpasts-2016-0078. plugin=1&language=en&pcode=ten00030, 2018 (accessed 21.06.2018). [60] Dz. U. 2015, 1277, Regulation of the Minister of Economy of 16 July 2015 on [31] EU/2014/955 Commission Decision of 18 December 2014 amending Decision the acceptance of waste for landfills, Jour. of Laws of the Rep. of Poland 2015, 2000/532/EC on the list of waste pursuant to Directive 2008/98/EC of the pos.1277, (in Polish). European Parliament and of the Council. [61] W. Ke˛pys, R. Pomykała, J. Pietrzyk, Properties of fly ash from thermal [32] Regulation of the Minister of Development of 21 January 2016 on the conversion of municipal sewage sludge, J. Polish Mineral Eng. Soc. 1 (31) requirements for conducting the process of thermal treatment of waste and (2013) 11–18. methods of dealing with waste resulting from this process, Jour. of Laws of the [62] R. Barbosa, N. Lapa, D. Boavida, H. Lopes, I. Gulyurtlu, B. Mendes, Co- Rep. of Poland 2016, pos.108, (in Polish). combustion of coal and sewage sludge: chemical and ecotoxicological [33] EU/2010/75 – Directive 2010/75/EU of the European Parliament and the properties of ashes, J. Hazard. Mater. 170 (2009) 902–909, https://doi.org/ Council of 24 November 2010 on industrial emissions (integrated pollution 10.1016/j.jhazmat.2009.05.053. prevention and control).