Introduction

Today, rapid increases in population, the rapid consumption of energy resources, and waste disposal problems have led scientists to seek new solutions. By considering waste as a raw material source, reusing used raw materials has gained great importance and has led countries to effectively use and improve energy (Brooks and Cetin 2012; Yilmaz 2012; Cetin 2013a, b, 2015a, b; Kaya et al. 2018). The problem of rapid consumption of natural resources (raw materials and energy) brings significant pollution problems. Many countries and international organizations are trying to minimize these losses and reuse wastes under new regulations (Bilgin 2010; Cetin et al. 2012a, b; Cetin 2016; Cetin 2017; Varol et al. 2019; Cetin et al. 2018). Considering all these problems, waste materials that create storage problems can be reused, and thus, environmental protection will be achieved while decreasing the production costs of related products (Brooks and Cetin 2012; Yiğiter 2014; Cetin 2013a, b, 2015a, b; Kaya et al. 2018). Recycling is a long-term economic investment. Economic problems can increase with decreased raw materials and the rapid consumption of natural resources. The recycling process has positive effects on the economy in this case. Reducing the consumption of energy and natural resources is of great importance for national economies as well (Özden 2015; Cetin 2013a, b, 2015a, b; Kaya et al. 2018; Cetin et al. 2012a, b; Cetin 2016, 2017; Varol et al. 2019; Cetin et al. 2018).

Fly ash (FA) is a byproduct of thermal power plants in which coal is burned and is produced by means of electro filters before cooling during the melting of inorganic substances in the furnace and expulsion from the chimneys (Türker et al. 2009). Coal has two classes, F and C, according to the American Society for Testing Materials (ASTM) standard C618-17a (ASTM C618-17a, 2017), depending on the chemical composition, which is a result of the combustion type. F-class ashes are produced by burning anthracite or bituminous coal (SiO2 + Al2O3 + Fe2O3 ≥ %70), and C-class ashes are produced by burning low-bituminous coal (SiO2 + Al2O3 + Fe2O3 ≥ %50). C-class ash, also called high-calcareous fly ash, has a CaO content greater than 10% and has partial binding features in addition to low pozzolanic characteristics (Ghosh and Singh 2013; Tan et al. 1997; Pogrzeba et al. 2015; Xenidis et al. 2002; Türker et al. 2009).

Blast furnace slag (BFS) is defined as a byproduct that is formed when metals or metal-containing ores are melted and is a complex of oxides and silicates that are lighter than metal and accumulate on the surface due to density differences (Unal et al. 2014).

BFS is widely used as a binding material in concrete or cement to obtain environmental and economic benefits as well as to provide high durability. Slag is the result of metallurgical processes such as the production of metals or purification of pure metals. BFS, which is produced as a result of iron ore production in blast furnaces, results from the use of 12 lime-based inorganic ions to remove impurities from the solidified metals. This slag, which is formed as a liquid layer floating above the liquid iron at a temperature of 1300–1600 °C, enters the furnace with iron ore, coke, and limestone (Öz 2017). FA and BFS, which are the subjects of this study, are environmental wastes that occur in significant amounts in Turkey and cannot be reused to obtain economic benefits. The usefulness of these wastes as additives in cement is very important in terms of minimizing environmental hazards and contributing economically.

Since radioactivity harms human health, numerous studies have been carried out in recent years (Binici et al. 2012a). Radiation beams decrease in intensity when passed through a substance. This reduction depends on the thickness of the material, the elements contained therein and the concentrations of elements in the substance. To absorb X- and γ-rays, materials made of heavy elements are used. Lead is the most important radiation shielding substance used in industry. For this purpose, walls and doors in places working with radiation are covered with lead plates. Lead is a heavy element because of its specific gravity. Therefore, as an alternative to lead, it is important to identify other materials with high radiation absorption characteristics for use in industry (Sevinc 2011). The usage of radiation shielding basic materials in construction is important in terms of creating healthier living environments and allowing construction to proceed without any extra work or load (Sevinc 2011).

In this study, the reusability of FA and BFS from industrial waste materials at a construction site was investigated. These two waste materials were added to Portland cement together and separately in different amounts, and the radiation absorption properties of the mixtures were investigated, as well as their physical and mechanical properties under the influence of high temperature. The results reveal the possibility of economically using these environmentally harmful wastes as well as how they affect the quality and radiation permeability of cement produced by using these wastes as additives.

Materials and methods

Materials

Cement

In this study, PC 42.5R (CEM I) cement was used. The chemical and physical properties of the cement are given in Table 1.

Table 1 Chemical and physical properties of PC 42.5 cement
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Fly ash and blast furnace slag

FA and BFS were used as additives in the experimental study. The FA and BFS used in the experiments were milled to be finer than the Portland cement. The chemical composition and physical properties of the FA and BFS are given in Table 2.

Table 2 Chemical composition and physical properties of FA and BFS
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Methods

Production of cements and cement experiments

Cement was produced by using FA, BFS, and FABFS via the substitution method at 5%, 10%, 15%, and 20% ratios. The mortars were produced in 40 × 40 × 160 mm dimensions (ASTM 2002). The amount of water required in each mixture was determined by flow table tests according to the flow diameter specified in ASTM standards C230, C109, and C1437 (Bayraktar et al. 2019c). The produced samples were stored at 20 ± 2 °C at a relative humidity of 95%.

Production of cement mortars and mortar experiments

The chemical composition and physical properties of the PC 42.5, FA and FABFS that were used in the production of PC 42.5, FA, BFS, and FABFS blended cements were determined. The experimental methods were performed by using triple steel mortar molds with dimensions of 40 × 40 × 160 mm (Bayraktar et al. 2019c). Three types of mortar samples (FA, BFS, and FABFS) prepared with CEN standard sand were subjected to flexional and compressive strength tests at two different ages (28 and 90 days). Mortar samples were produced in the form of mortar prisms with dimensions of 40 × 40 × 160 mm. Samples were removed from the molds after 24 h and kept in a laboratory with 95% relative humidity at 20 ± 2 °C until the experiments on the 28th and 90th days. The mixture ratios used in the experiments were determined by calculations considering the flow rates. The mortar sample with cement binding was named PC 42.5; the mortar samples bonded with cement and FA at 5, 10, 15, and 20% ratios were named FA5, FA10, FA15, and FA20, respectively; the mortar samples bonded with cement and BFS at 5, 10, 15, and 20% ratios were named BFS5, BFS10, BFS15, and BFS20, respectively; the mortar samples bonded with cement and a mixture of FA and BFS at 5, 10, 15, and 20% ratios were named FABFS5, FABFS10, FABFS15, and FABFS20, respectively.

High-temperature treatment

The application of high temperature was carried out in accordance with the requirements of standard BS EN 13501-1 (BS EN 13501-1 2007). After curing periods of 28 and 90 days, the mortar samples were stored in an oven (105 ± 5 °C) for 24 h before exposure to high temperature. The mortar samples, which were dried in the oven, were placed in a high-temperature oven to determine the effect of high temperature. During the heat treatment phase, the samples were heated at 6 °C/min in the high-temperature oven at 150, 300, 700 and 900 °C for 2 h (Bayraktar et al. 2019c). Reference mortar samples at 20 °C were not exposed to high temperature.

Cooling process

The samples that were kept at 150, 300, 700, and 900 °C for 2 h for high-temperature treatment were cooled in air (20 ± 2 °C in the laboratory). Flexural strength and compressive strength tests were performed on the mortar samples after the cooling process. The air-cooled mortar samples were kept in the laboratory for 30–180 min, depending on the cooling speed, until reaching a temperature of 20 °C.

Compressive strength and flexural strength experiments

The compressive strength and flexural strength values were determined by subjecting 3 samples representing each high-temperature exposure group to compressive strength and flexural strength tests 1 day after beginning cooling (Bayraktar et al. 2019c; Ünal and Uygunoglu 2004).

Determination of linear absorption coefficients

The radiation permeability of the samples was tested at 59.6 keV, 26 keV, 17.3 keV, and 5.9 keV energy levels. In this study, a Si (Li) solid-state detector with a resolution of 155 keV at 5.9 keV was used. When a radiation beam passes through an absorber, its intensity decreases. Fe-55 and Am-241 radioisotope sources were used as radiation sources in this study. The sample thicknesses were 3 cm. A Si (Li) solid-state detector with 155 keV resolution was used at 59.60 keV. The count spectra were evaluated with the help of an S100 card. The radioactive permeability of the samples was determined by calculating the percentage of the passed and absorbed radioactive rays at different energies (Binici et al. 2015).

The radioactive permeability was calculated from the following correlation (Eq. 1):

$$ \mu =\ln\ \left(I\mathrm{o}/I\mathrm{x}\right)/(X) $$
(1)

whereIo is the intensity of the measured rays in the absence of a sample;Ix is the intensity of rays passing through a sample of thickness X;X is the sample thickness.

Experimental findings and discussion

Physical properties of produced cement

The produced cement samples were tested for density, Blaine area, initial and final setting time, and fineness (% retained at 40 μm and % retained at 90 μm), and the results are given in Table 3.

Table 3 The physical properties of various cement types
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The lowest Blaine values of the produced samples were obtained for BFS5, and the highest values were found in FABFS20. The lowest density was found in FABFS20, and the highest density was that of BFS5. The initial and final setting times of the produced cements fell within specified limits (Bayraktar et al. 2019c).

Flexural strength of FA and BFS mixed mortars

Table 4 shows the flexural strength test results for the FA, BFS, and FABFS cement mortar prisms on the 28th and 90th days. The results were evaluated in accordance with the substitution rate of FA and BFS in the cement and mixing water, and the mechanical properties of the cement mortar were evaluated with respect to high-temperature treatment.

Table 4 Flexural strength of mortar samples
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Table 4 indicates that the flexural strengths of 28-day-old FA5, FA10, FABFS10, FABFS15, and FABFS20 were greater than those of additive-free PC 42.5 cement at 20 °C (ref.) and 150 °C; the flexural strengths of FA15, FA20, BFS5, BFS10, and BFS15 were close to those of additive-free PC 42.5 cement at 20 °C (ref.) and 150 °C.

The flexural strengths of 90-day-old FA5, FA10, FA15, BFS5, FABFS5, FABFS10, FABFS15, and FABFS20 were greater than those of additive-free PC 42.5 cement at 20 °C (ref.) and 150 °C; the flexural strength of the FA20 sample was close to that of additive-free PC 42.5 cement at 20 °C (ref.) and 150 °C.

There was a difference between the 28th and 90th days according to the type of blended mortar sample: the flexural strength decreased with temperature from 300–900 °C. A comparison of the produced mortar samples after 28 and 90 days of air cooling revealed that the highest and lowest flexural strength values were obtained at 150 and 900 °C, respectively.

Compressive strength of FA and BFS blended mortars

The compressive strength test results of the 28- and 90-day-old FA, BFS, and FABFS blended cement mortar prisms are given in Table 5. The substitution rates of FA and BFS in cement were evaluated in accordance with the mixing water, and the effect of cement mortar on the mechanical properties at high temperature was investigated.

Table 5 Compressive strength of mortar samples
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Table 5 shows that the compressive strengths of 28-day-old BFS20 samples were greater than the values obtained for pure PC 42.5 cement at 20 (ref.), 150, 300, and 700 °C; the compressive strengths of FA5, BFS5, BFS10, BFS15, FABFS5, and FABFS10 were greater than the values obtained for pure PC 42.5 cement at 20 (ref.), 150, 300, 700, and 900 °C; the compressive strengths of FA10, FABFS15, and FABFS20 were close to the values obtained for pure PC 42.5 cement at 20 (ref.), 150, and 300 °C.

The compressive strengths of 90-day-old FA20, BFS5, BFS10, BFS15, BFS20, FABFS5, FABFS10, FABFS15, and FABFS20 were greater than the values obtained for pure PC 42.5 cement at 20 (ref.), 150, 300, 700, and 900 °C; the compressive strengths of FA5, FA10, and FA15 were quite close to the values obtained for pure PC 42.5 cement at 20 (ref.), 150, 300, 700, and 900 °C.

Comparison of the produced mortar samples after 28 and 90 days of air cooling revealed the highest and lowest resistances for the mortar samples at 150 and 900 °C, respectively.

Determination of linear absorption coefficients

The radiation permeability of the samples at 59.6 keV, 26 keV, 17.3 keV, and 5.9 keV was examined; the samples absorbed all radiation at 17.3 keV and 5.9 keV, so the I values were zero at these energy levels. The values obtained at 26 keV and 59.6 keV are given in Table 6.

Table 6 Intensity values for samples at 26 keV and 59.6 keV energy
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The linear absorption coefficient indicates the radiation absorption value of a material. The higher the μ value is, the higher the radiation absorption capacity. Table 6 shows that the FABFS samples absorbed the most radiation at 26 keV. The FABFS samples transmitted six per thousand of 26 keV energy rays. The BFS sample transmitted the most radiation, 2.2% of the rays. These results indicate that the FABFS sample can be easily used as a radiation-absorbing material in places with 26 keV energy. The BFS sample transmitted 45% of the 59.6 keV rays, but 39% of the rays passed the FA sample. Here, the FABFS sample absorbed the most radiation at 59.6 keV, but this absorption ratio of these mortars at this energy level is not sufficient. At this level of energy, it would be necessary to increase the thickness of the FABFS sample to be able to use this material in industry. The FABFS sample can be used as a radiation-absorbing material. Those who use lead vests in medicine and work with radiation can reduce the effect of radiation by using this material. The proposed material can also be used as a wall covering in medical buildings. Thus, the negative effects of high-energy radiation can be reduced (Binici et al. 2012b).

Results and discussion

The flexural strength and compressive strength at all temperatures above 150 °C decreased on days 28 and 90. This result may have occurred because the mineral additives used in this research reduce the number of pores in mortar samples. In addition, the amount of Ca(OH)2 decreases in the system due to the pozzolanic reaction occurring between the reactive silica (SiO2) in the mineral additives and the Ca(OH)2 in the cement (Demirel and Kelestemur 2011). Mixtures containing a certain proportion of mineral additives substituted in the cement contain less calcium hydroxide than pure PC cement, which may also be the reason for the increase in strength at temperatures up to 150 °C.

Today, cement is the most widely used binding material in the construction sector. The energy involved in cement use has also revealed economic and environmental problems. Approximately 7% of the total CO2 emissions in the world are caused by cement production. Therefore, producing alternative cements for portland cement is a current research topic (Binici et al. 2012a). Since the additives used to produce cement are industrial wastes that damage the environment, it is important to avoid the environmental pollution caused by the use of these materials in mortar and to reduce the costs of the samples produced. Additive cements are important in terms of sustainable concrete technology, in addition to providing environmental gains.

The mortar experiments indicated that the density, flexural strength, and compressive strength of the additive mortar samples at all ages decreased in proportion to the amount of FA and BFS. The initial and final setting times of the FA5 and FA10 blended mortar samples were lower than those of the BFS5 and BFS10 blended mortar samples; however, the initial and final setting times of FA20 were higher than those of BFS20 among the 28-day samples. The mortar samples blended with FA demonstrated strengths similar to those of the control mortar samples, while the BFS blended mortars and FABFS5 and FABFS10, which are double additive samples, presented higher compressive strengths than the FA-blended mortar samples.

On the 90th day, the samples with FA as an additive had compressive strengths close to that of the PC 42.5 control cement at all temperatures; the FA20 sample gave a greater strength than the control cement; all samples with BFS and double additives gave higher strengths than the control cement; and all the samples with BFS as an additive gave higher strengths than the samples with FA as an additive. From these data, it was concluded that BFS was more effective than FA in terms of the strength of advanced-age cement due to its pozzolanic activity.

On the 28th day, at all temperatures, the compressive strengths of the FABFS5 and FABFS10 blended samples were higher than those of samples blended with FA; on the 90th day, all the samples blended with FABFS gave higher compressive strengths at all temperatures than the FA-blended mortar samples.

The detrimental effect of high temperature was more pronounced on bending strength than compressive strength. Comparing the reference cement with the FA- and BFS-blended cements indicated that the most suitable additive ratio is 20% in terms of strength, physical properties, and usability. The sample with the highest linear absorption coefficient was the mortar sample produced with FABFS as an additive. In other words, the sample with the highest linear absorption coefficient was that with the least radioactive permeability.

In the microstructures of sections taken from mortar samples treated at high temperature, aggregate distribution, crack development, and pore structure could not be distinguished well up to 300 °C, but at higher temperatures, the cracks between aggregate grains of binder grew. The increase in flexural strength and compressive strength of the mortar samples from 100 to 300 °C and the water vapor formed at high temperature caused high pressures in the blended mortar samples (Bayraktar 2016). This process creates internal balance.

The strength increase up to 300 °C was caused by the gel layers in the matrix shifting closer to each other as a result of the evaporation of free water, increasing the attraction due to the greater van der Waals forces (Khoury 1992; Hossain 2006). This situation was especially observed in the 90-day-old samples. According to previous studies, calcium hydroxide and calcium silicates are completely decomposed at 500 °C and 900 °C, respectively (Bayraktar 2016). In the experimental study herein, some experimental results for samples at 700 and 900 °C indicated low strengths.

According to the experimental results, it was determined that concrete with high strength can be produced by using BFS and FA in combination, especially at advanced ages. Microstructure investigations demonstrated that the internal structure of the 90-day-old blended cements became more filled with CSH gels resulting from the pozzolanic reaction. As a result of cement hydration, Ca(OH)2, formed as a hydration product, starts to react with pozzolans. The result is an increase in the amount of CSH gels, which give strength to concrete. In this way, the increase in compressive strength on the 28th and 90th days can be attributed to the amount of pozzolan.

The most important parameter for the use of BFS in cement and concrete is the amount of glassy phase it contains. The chemical composition is also important. For example, the amount of CaO+SiO2+MgO is expected to be at least 67% (Tokyay 2013). The total CaO+SiO2+MgO content of the BFS used in this study was 81.62% (Table 2). According to ASTM C 618, the total amount of SiO2+Al2O3+Fe2O3 in FA is expected to be at least 70% by weight (Tokyay 2013). The sum of SiO2+Al2O3+Fe2O3 in the FA used here was 82.98%, and the two pozzolans were above the boundary conditions (Table 2). Therefore, the FA and BFS used in this study are suitable for use in cement and concrete.

Studies on the use of different substitutes in cement are very important in terms of both waste disposal and cost reduction. Therefore, many studies have been carried out on this subject. Tang and Lo (2009) concluded that BFS additives perform better in terms of mechanical properties than other pozzolan-added concretes or additive-free concretes at high temperature. This study demonstrated that the BFS additive contributed positively to durability and strength. The use of mineral additives as binary mixtures solved the deficiencies caused by the use of mineral additives alone. In other words, the mineral additives in the FABFS mixture complemented each other, allowing the material properties to be closer to those of the reference sample and resulting in a more homogenous material at an early age while reducing the amount of cavities and ettringites. Another important point is that the contributions to the environment and economy achieved by the use of binary mixtures can provide significant benefits.

Kabeer and Vyas (2018) used marble dust (MD), a waste product formed during the cutting and shaping of marble blocks, to replace traditional river sand in cement mortars. The results of their study indicated that mortars blended with river sand and MD at a 20% ratio can be used for masonry and processing purposes. Khodabakhshian et al. (2018) added silica fume (0%, 2.5%, 5%, and 10%) and waste MD (0%, 5%, 10%, and 20%) to portland cement at different proportions and found that the durability and strength of the concrete containing waste MD tended to decrease at proportions over 10% but satisfactory results were obtained below this level. Yildiz et al. (2017) investigated the mechanical and physical properties of waste MD- and glass fiber-added cement mortars exposed to sulfate attack and concluded that the use of up to 40% (by volume) MD in glass fiber-reinforced mortar samples to increase tensile strength could provide positive gains in terms of both economy and sulfate resistance.

Kara and Yazicioglu (2016) determined that as the carbonation depth increased in concrete samples produced by substituting different amounts of MD waste and 10% silica fume, the ultrasound velocity increased, the capillarity coefficient decreased, the amount of wear decreased and the compressive strength increased.

Açikgenc et al. (2013) stated that, instead of cement, Elaziğ region limestone powder and waste brick powder could be used as mineral additives in mortar at low substitution rates by the substitution method. Nežerka et al. (2014) studied nine different paste sets with metakaolin and brick dust and showed that metakaolin exhibited a much stronger pozzolanic activity than brick dust and did not necessarily increase the mechanical properties of pastes with the addition of pozzolan.

Kaya and Yazicioglu (2015) investigated the effect of high temperature on the mechanical and physical properties of calcined mortar and concluded that the lowest resistance losses before and after high-temperature exposure were obtained from the reference sample at 500 °C and from 10% bentonite-added samples at 750 and 1000 °C. Gökcer et al. (2013) added waste MD to mortar samples reinforced with different amounts of glass fiber by displacing the filling material at 10%, 20%, and 30% by weight. They stated that the use of waste MD in the glass fiber-blended mortar samples yielded a denser structure and thus caused less strength loss in high-temperature mortar samples.

Öz (2017) stated in his study that mineral additives such as waste glass dust and BFS improve the basic mechanical properties, such as compressive strength and flexural strength, of self-compacting mortars, and that while the compressive strength of the produced mortars varied between 26.54 and 80.4 MPa, the flexural strength of the samples ranged from 5.8 to 10.2 MPa. He concluded that generally lower values than those of the control mortar were obtained from BFS15 and subsequent mortar samples. In his study, the compressive strength of the produced mortars ranged from 10.6 to 75.4 MPa, while the flexural strength varied between 0.4 and 11.9 MPa. This change shows that the maximum values were similar, but the difference in the minimum values was due to the high-temperature effect. The values obtained for FABFS20 on the 28th day were lower than but close to those for the control mortar. Therefore, he concluded that the most appropriate additive rate was 20%.

Binici et al. (2012c) concluded in their study that light construction materials produced from cotton waste, FA and adhesive resin could be used for heat and sound insulation and that the radioactive permeability of barite lightweight building materials was low. Binici et al. (2012d) stated in another study that the sample with the highest linear absorption coefficient was a geopolymer obtained from BFS and that this material with low radioactive permeability could be used in structures exposed to radiation effects. Binici et al. (2015) reported that the use of egg shells as an additive to increase the radiation absorption properties of mortars reduces the radioactive permeability and therefore can be used in structures exposed to radiation effects. Ling et al. (2013) studied the X-ray radiation protection properties of cement mortars prepared with six different aggregate types and found that mortars prepared with recycled CRT funnels with barite or lead loaded with glass had increased radiation protection ability as well as an increased mortar density. In particular, they concluded that barite mortar could be used as plaster.

New trends in environmental regulations seek to make use of industrial byproduct wastes such as BFS and FA as partial substitutes in the production of mortar and concrete instead of cement and aggregates (Saridemir 2016). By making use of these wastes as raw materials, environmental pollution can be prevented, and the wastes can be supplied to the economy as construction materials (Bayraktar 2016, Bayraktar et al. 2018; Bayraktar et al. 2019a, b; Merkit et al. 2018; Yilmaz 2014; Akyildiz et al. 2017; Köse and Akyildiz 2017; Subasi et al. 2017; Binici et al. 2012c). By using these wastes, raw materials must be obtained by using the wastes alone or mixing them with other materials to produce new materials that are appropriate according to the standards in use (Bilgin 2010). CO2 emissions can be minimized by the use of industrial wastes such as FA, BFS, and silica fume in cement-based systems (such as plaster, mortar, and concrete), reducing the need for natural resources and energy (Tangüler et al. 2015).

Fire is a phenomenon that occurs when solid, liquid, or gaseous substances burn out of control. Uncontrolled fire is often seen as a catastrophe that causes significant loss of life and property. This situation has revealed the importance of active measures in fire protection (Baradan et al. 2010). It has been observed that concrete is more resistant to high temperatures and fire than many building materials. Concrete is defined as a material with high fire resistance because it does not cause significant damage for a certain period of time and does not produce toxic fumes (Neville 2000). However, this durability is valid only for certain times and temperatures (Baradan et al. 2010). For example, in normal-strength concrete produced with silica-based aggregates, the strength loss at 600 °C is approximately 50% (Neville 2000). Events causing a loss in compressive strength at high temperatures have been explained by a thermal mismatch between the cement paste and aggregate, connections in the aggregate cement interface, the pressure of evaporating water at high temperature, and changes in the chemical structure of the cement paste and aggregate (Cülfik 2001). According to the above studies, a number of differences and advantages have been observed (Table 7).

Table 7 Differences and advantages according to the above studies
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Suggestions

This study has demonstrated that industrial wastes such as FA and BFS can be used in cement production at different rates both separately and together. Because these materials are waste materials, their use in mortar is important to prevent the environmental pollution caused by these materials and to reduce the costs of the samples produced. At this point, it is important to know how the quality of concrete changes depending on the proportion of materials used. According to the results obtained in this study, the use of FA5 and FA10 cements is more suitable for concrete production conditions where early strength is important and weather conditions are cold.

The compressive strength of 28-day-old samples with FA as an additive was close to the control mortar strength at all temperatures; the samples with BFS as an additive and the binary mixtures FABFS5 and FABFS10 had higher compressive strengths than the control mortar; and the samples with BFS as an additive and binary additives of FABFS5 and FABFS10 had higher strengths than the samples with FA as an additive.

At all temperatures, on the 28th day, the compressive strengths of the FABFS5 and FABFS10 blended samples were higher than those of samples blended with FA; on the 90th day, all the samples blended with FABFS had higher compressive strengths at all temperatures than the blended FA mortar samples. In consideration of these results, it will be beneficial to determine the mixture ratios in cement production.

On the 90th day, at all temperatures, the compressive strength of the samples with FA as an additive was close to the control mortar strength; the samples with FA20 had higher strength than the control mortar; the samples with BFS as an additive and all the binary blended samples had higher strengths than the control mortar; and all the samples with BFS as an additive and the binary blended samples had higher strengths than the samples with FA as an additive.

Therefore, the most suitable additive for fire resistance is BFS, but FABFS is the most suitable additive when considering not only fire but also multidimensional (economic and environmental) aspects. The cement production results in this study allow the selection of additive rates that do not make significant concessions in cases where exposure to high temperature in concrete design may occur. For example, the compressive strengths of FABFS15 and FABFS20 after 28 days were quite close to that of the PC 42.5 mortar. The 90th day compressive strengths of the FA and BFS additive samples were close to or higher than that of the PC 42.5 mortar, and all the binary mixtures had higher strengths than the PC 42.5 mortar, proving that by using these two industrial wastes in cement production, it is possible to produce more environmentally friendly and economic cement.

High temperature is an important factor in sustainability and causes significant losses in concrete design and mechanics. In concrete structures, high-temperature exposure situations such as fire, explosion, and combustion must always be taken into consideration. Cement mortars would be less damaged less by high temperatures when using FA and BFS as substitutes. Higher temperature ranges can be applied in further studies. Thus, potential accidents can be minimized in structures that may be exposed to high temperatures.

Today, persistence is an important parameter in addition to strength in the production of sustainable structures. It could be beneficial to examine the additive mortars considered in this study (with regard to physical and mechanical compatibility) in terms of persistence in further studies. The positive effects of additive cements on concrete permanence will enable the resulting structures to serve without problems for years.

According to the experimental results, concrete with high strength can be produced by using BFS and FA in combination, especially at advanced ages. In addition to the pozzolan features of the slag, thanks to the microfiller features, the amount of fine aggregates can be reduced, and the thinness of the pozzolan is estimated to be increased.

These results indicate that FABFS samples can be easily used as radiation-absorbing materials in places with 26 keV energy. While the BFS sample transmitted 45% of 59.6 keV rays, 39% of the rays passed the FA sample. Here, the FABFS sample absorbed the most radiation at 59.6 keV, but the absorption ratios of these mortars at this energy level are not sufficient. At this level of energy, it is necessary to increase the thickness of the FABFS sample to be able to use the material in industry. The FABFS sample can be used as a radiation-absorbing material. Those who use lead vests in medicine and work with radiation can reduce the effect of radiation by using this material. FABFS can also be used as a wall covering in medical buildings. Thus, the negative effects of high-energy radiation can be reduced.

Environmental factors should be considered in sustainable concrete design. By reducing the carbon dioxide (CO2) and greenhouse gasses emitted in cement production, it is possible to prevent the destruction of nature and environmental pollution to some extent. Today, from the perspective of sustainable architecture, the technical and economic potential of the cement production process should be reconsidered in order to provide environmental benefits to national economies and further benefits to the construction industry. Thus, environmental, economic and, most importantly, significant human life benefits can be provided.