Electrical and Mechanical Effects of Carbon Powder in F and C Class Fly Ash Reinforced Mortars

This study was carried out to investigate the effects of carbon powder on the electrical conductivity and mechanical properties of fly ash reinforced mortars used as mineral additives. Samples were created by replacing CEM I 42.5 R cement, water and Cen standard sand with 0.5%, 1%, 3% carbon powder by weight. Class F and Class C fly ash were added separately at the rate of 10% and 20% by weight of cement to the formed carbon dust series. 20 different series were created with the reference sample. Electrical resistivity measurements were made to the oven dry and natural humid conditions of the samples that completed their 7,28 and 56 days curing period. The physical properties of the samples were determined and bending and compressive strength tests were made. The results obtained were evaluated and it was observed that with the increase of the carbon dust ratio compared to the reference sample, the electrical conductivity ratio increased, but the conductivity decreased depending on the time. It has been observed that the F class fly ash combination series are more conductive than the C class combination series. It was observed that the compressive and tensile strength values of F and C class fly ash carbon dust free samples increased with time. Carbon dust has been shown to increase compressive strength in fly ashless series. There was an increase in the 56th day reading in the tensile strength. It was observed that F class increased tensile and compressive strength in fly ash and carbon dust combination series. ash, C class fly ash, Electrical conductivity.

tartaric acid containing organic matter. Stoeckli & Kraehenbuehl (1984). It was used as a decolourizer in the sugar industry in England in 1794. Kodlec, O. (1979). Activated carbon is used in a wide range of areas, including in the industry, purification and refinement of gases, in separation of mixtures, in purification processes in the food industry, in water and wastewater treatment, in carbon additive in the metal industry, in protective clothing in the defence industry, in explosives in the weapon industry and making bombs to silence electronic systems and in the health sector. Currently, it is strategically important for the future of our country, as it has quite suitable areas of use for the defence industry. In summary, activated carbon, which we use for various purposes in daily life, is an indispensable substance. Stoeckli & Kraehenbuehl (1984). Sezer et al.(2019) reported in their work on the production of 3D parts in complex form easier, lower cost and faster than traditional methods with additive manufacturing (IR) technology that the strength of the part can be significantly improved with 6 mm long carbon fibre reinforcement, and the use of reinforcement materials in the form of either powder or short (> 3 mm) fiber as additives increases the mechanical strength to a limited degree in the literature. Boğa, A.R. (2017) searched the effects of steelmaking slag and carbon fibre on the mechanical and electrical conductivity properties of mortars when used together or separately. According to the results obtained, it was observed that electrical conductivity properties improved when steelmaking slag and carbon fibre were used together in mortar samples. Dehghanpour (2019) examined the results by conducting mechanical, electrical and impact tests of electrically conductive concrete. According to the results of the test, samples containing nano carbon black, carbon fibre and steel fibre in different functions improve mechanical properties. The electrical resistances of all electrically conductive concrete samples mixed with carbon fibre are decreased compared to the control sample, and this feature became clearer as the carbon fibre content ratio increased.
Fly ash, which is abundant in our country, is a valuable type of waste derived from coal-fired thermal power plants. The use of mineral additives has increased with the detection that it lowers the cost by reducing the production energy in Portland cement concrete. Subaşı, S. (2009). Due to their fine-grained and pozzolanic reaction, mineral additives improve the mechanical properties of concrete. Aruntaş, H.Y. (2006). This study allowed comparison of F and C Class fly ashes.

Material And Method
2.1. Materials 2.1.1. Cement CEM I 42.5 R Portland cement which is compatible with TS EN 197-1 , with grain density 3.15 g/cm3 and whose specific surface is 3740 cm 2 /g was used in the study.

. Fly Ash
Fly ash is a kind of waste derived from coal-fired thermal power plants. Although there is an average annual production of fly ash of up to 13 million in power plants in our country, it is estimated that this rate will increase in the future, taking into account the energy need.
Several researches have been conducted to take advantage of fly ash like every industrial waste and it is widely used as additive in cement concrete. Türker, P. et al. (2009).

Classification of fly ashes
In the classification of fly ash, ASTM C 618 [19] and TS EN 197-1 standards are mainly taken as a basis in accordance with the percentage of chemical component. According to ASTM C 618 standard, fly ashes are divided into F and C classes.

C class fly ash
Class C fly ashes are the ashes produced from lignite or semi-bituminous coal, with a total SiO2+Al2O3+Fe2O3 amount of more than 50%; and besides the pozzolanic feature they also have binding features as well; since CaO>10%, these ashes are also called high calcareous fly ash. The fly ash from Soma Thermal Power Plant was used as Class C in the mortar samples. Its specific weight is 2.41g/cm 3 ; 90µm sieve residue (%) is 33.7; 45µm sieve balance (%) is 52.6.

.F class fly ash
Class F fly ashes are the ashes produced from lignite or semi-bituminous coal, with a total SiO2+Al2O3+Fe2O3 amount of more than 70% and have pozzolanic feature; since its CaO percentage is below 10% it is also known as low calcareous. The fly ash from Çayırhan was used as Class C in the mortar samples. Its specific weight is 2.36g/cm 3 ; 90µm sieve residue (%) is 6.7; 45µm sieve balance (%) is 24.5.

. Carbon Powder
Activated carbon acquires different chemical activity and physicochemical properties depending on the source from which it is obtained. It can adsorb a wide variety of molecules on its inner surface. Jaroniec & Choma (1986).
In an Ideal activated carbon, the pores are around 0.2-1.0 cm 3 g -1. Although the surface area is in the range of 400-1000 m 2 g -1, This value can be exceeded in special purpose productions. Morgan & Fink (1989). Pore sizes vary from 0.3 to thousands of nanometers.
According to its shape and size, activated carbon is divided into four groups as powder, granular, filamentous and fabric. Küçükgül, E.Y.

Method
In this study, 20 types of samples were created as water, CEM Ι 42,5 R cement as carbon powder reinforced at 0.5%, 1%, 3% by weight of aggregate to the Cen Standard Sand mix and F and C class fly ash combination at rates of 10% and 20% and monocoque as a substitute for cement. In all mixtures, the water/cement ratio was determined to remain in the range of 220mm-230mm in the Spreading Table Test in line with TS EN 12350-5. In order to reduce the margin of error, 3 samples were prepared with dimensions of 4x4x16 cm and for each series. The oven dry and electrical resistivity to natural humid conditions measurements of the samples that completed the 7.28 and 56-days curing time were made and the data obtained are interpreted. Compressive strength and flexural strength of all samples were tested.

Results And Findings 3.1. Electrical Resistivity Measurement Results
According to electrical resistivity measurement, no critical effect was observed in C-Class fly ash and carbon powder combination samples compared to the reference sample. Electrical resistivity increased depending on the time. 56-day samples showed an increase in electrical conductivity due to an increase in the ratio of carbon powder (Table 3.1). The best result has been obtained from a Class C fly ash-free 3% carbon dust sample.  According to the electrical resistivity measurement, an increase in electrical conductivity was observed in F class fly ash and carbon powder combination samples compared to the reference sample (Table 3.2). Electrical resistivity increased depending on the time. The best result was obtained from the sample with 20% F class fly ash and 3% carbon powder. In the electrical resistivity measurements, it was seen that the mortar samples of carbon powder made conductive compared to the reference sample. The best result was obtained from combinations of fly ash with a ratio of 10% and carbon powder with a ratio of 0.5% (Table 3.3). It has been concluded that F Class is more conductive compared to C Class in carbon powder and fly ash combinations. Table 3

3.2.Compressive Strength Test Results
The only sample in the series with no fly ash that showed an increase compared to the reference sample was obtained from CNT + CD 0.5% (Table 3.4). Although there was an increase in the 7. and 28. day series as the rate of carbon powder increased, it was observed that there was a decrease in the compressive strength in the 56. day series. Table 3.4.Compressive strength test results of control (reference) samples An increase in compressive strength was seen in the 10% grade C fly ash sample without carbon powder compared to the reference sample. Although there was an increase in the series with the combination of 0.5% carbon powder and 10% C class fly ash, it was observed that there was a decrease in the compressive strength in the other series (Table 3.5). Table 3.5.Compressive strength test results of 10% rated Class C fly ash and carbon powder combinations.
An increase in compressive strength was observed in a Class C fly ash sample with a rate of 20% without carbon powder compared to the reference sample. Although the C20 + CD 0.5% sample increased, it was observed that there was a decrease in the compressive strength in the other series (Table 3.6). It has been determined that the carbon powder used more than 0.5 % reduces the compressive strength, despite the 10% fly ash supplement.   An increase in compressive strength was observed in all series with 10% F class with fly ash carbon powder and carbon powder-free compared to the control sample (Table 3.7). The best result was obtained from the F10 + CD 0.5% sample. An increase in compressive strength was observed in in 20% class F class with fly ash carbon powder and carbon powder-free compared to the reference sample except for the F20 + CD 3% sample (Table 3.8). However, the 7th and 28th day readings of the relevant sample are observed to be increased compared to the reference sample. The best result was obtained from the F20 + CD 0.5% sample.   According to the results given in Table 3.9, the most efficient result of 0.5% by weight of aggregate was obtained in C class fly ash and carbon powder combinations. In the compressive strength test, the best result was seen in C10+CD 0.5% and C20+CD 0.5% samples in the C class fly ash and carbon powder combination series. Table 3.9Compressive strength test results of Class C fly ash and carbon powder combinations.
In the compressive strength test, the best results were seen in the F class fly ash and carbon powder combination series in C10+CD 0.5% and C20+CD 0.5% samples. According to the results given in Table 3.10, the most efficient result of 0.5% rate by weight of aggregate was obtained in F class fly ash and carbon powder combinations.

Tensile Strength Test Results
According to the results of the tensile strength test conducted in the series with fly ashless carbon powder, it was determined that there was an increase in the sample with 0.5% carbon powder compared to the reference sample (Table 3.11). It was observed that there was an increase in 56-day series. Table3.11.Tensile strength test results on samples with fly ash-free carbon powder In the 10% Class C fly ash series, an increase in the tensile strength of the sample with carbon powder-free was detected. A decrease in tensile strength was found in 7 and 28 day series with 10% C class fly ash combination of carbon powder compared to the reference sample (Table 3.12). In the 56-day series, it was concluded that it increased the tensile strength.   It was determined that there is a decrease in the tensile strength in the 20% rated class C fly ash series, the carbon powder-free sample compared to the reference sample, and the tensile strength in the combination series with carbon powder (Table 3.13). C20+CD 1% sample showed an increase in tensile strength in 56 days of test. Table 3.13Tensile strength test results of 20% Class C fly ash and carbon powder combinations.
It was observed that there was an increase in the tensile strength of the 10% rated class F fly ash series in the carbon powder-free sample. Although the carbon powder caused an increase in the F10 + CD 0.5% sample, it was found that there was a decrease in the tensile strength in the other series (Table 3.14). An increase in tensile strength was observed in 56-day series.   Vol.13, No.2, 2021 28 Table 3.14 Tensile strength test results of 10% Class F fly ash and carbon powder combinations.
It was seen that there was an increase in the tensile strength of the 20% rated class F fly ash series in the carbon powder-free sample (Table 3.15). Carbon powder has been found to cause a decrease in tensile strength compared to the reference sample, except for the 56-day series. Table 3.15 Tensile strength test results of 20% Class F fly ash and carbon powder combinations.
According to the results of the tensile strength test, when the samples with the combination of fly ash and carbon powder were compared, it was seen that the F class with fly ash series (Table 3.16 and Table 3.17) had higher tensile strength compared to the C class with fly ash series. The best results were seen in C class fly ash and carbon powder combinations with samples that were used at a ratio of 0.5% by weight to aggregate. In F class fly ash and carbon powder combinations, the best results were found in samples that were used at 1% by weight to aggregate.

Discussion
• This study showed that carbon powder increases electrical conductivity in fly ash reinforced mortars used as mineral additives. • It was seen that F and C Class fly ash reinforced mortars improve the compressive and tensile strength.
• F Class (Çayırhan) fly ash and carbon powder combination mortars have been found to improve the compressive and tensile strength compared to the reference sample. • All of the Class C fly ash and carbon powder series were found to have increased tensile strength in 56day tests. • Carbon powder, which has a wide floor in the food, mechanical and defence industries, can also be seen to provide effective benefits in the construction sector and is likely to take its place quickly among building materials. • It has been observed that carbon powder can also provide efficiency in smart concrete targeted structures.
• It has been found that carbon powder can also benefit in structures targeted for conductivity. • In these days, when global pollution is increasing rapidly, carbon powder used with mineral additives reduces environmental damage. • The combined use of fly ash and carbon powder ensures affordability compared to other carboncontaining materials.  He has many domestic and foreign articles, citations and scientific studies in the field of Building Materials and concrete technologies. As of 01/06/2020, he was appointed as the dean of Batman University Technology Faculty.