Effect of recycled brick powder on the properties of self-compacting fiber reinforced mortars produced with different cement types

Abstract

It is known that clay-based building materials such as bricks and tiles accumulate in landfills at the end of their useful lives. As an alternative, recycling clay-based building material can reduce the negative environmental impacts. Recycled brick powder (RBP) is obtained by grinding waste brick and tile collected from end-of-life landfills. Within the scope of the study, the use of self-compacting fiber reinforced mortars (SCFRMs) produced with RBP using CEM-I 42.5R and 52.5R class cements for two different cement classes was investigated. In accordance with EFNARC, a water binding ratio of 0.42 was used to control the workability and strength of the SCFRM. In the produced SCFRM, 1%, 2%, and 3% by weight binder Polypropylene (PP) fiber was added to the blends with 10%, 20%, and 30% RBP substitutes. A total of 32 SCFRM mixes were produced and tested. The flexural and compressive strengths at 7, 28, 56, and 90 d were evaluated on the produced samples. In addition, porosity and water absorbency values were examined since these are significant for durability properties. It was observed that the use of RBP increases durability, and the use of fiber can have positive effects in terms of both durability and strength.

Graphical abstract

Keywords

cement strength / tile/brick dust / self-compacting fiberized mortar

1 Introduction

While concrete and mortar are the most widely used building materials worldwide, many natural resources are destroyed and consumed to obtain the basic materials, cement, and aggregate. Therefore, concrete and mortar cannot qualify as environmentally friendly materials. In addition, they are difficult to recycle after use and often accumulate in landfills. As a result of the studies carried out in recent years on this subject, minimizing these wastes in landfills by recycling a certain amount of concrete and mortar-based wastes has become a focus of waste management policies [1–7].

Brick/tile dust is generated during transport, such as loading or unloading, or during production on construction sites and brick kilns. In addition, brick/tile material remaining after renovation or as waste can be pulverized. This dust and brick/tile waste can be recycled. The need for rural reconstruction within the scope of developing economies and the new urbanization is the main reason for the need for construction activities in many countries. In this context, many old brick/concrete houses in countries, including China, were demolished and a large amount of brick waste was created during this process. The amount of this waste produced, worldwide, is approximately 0.4 billion t every year. In other developing countries such as India, Russia and Brazil, large amounts of brick waste are produced as a result of rebuilding activities. More than 3000 million t per year of brick/tile waste is generated in the world every year and remains as waste due to application or operational accidents [8–11]. Brick/tile powder and other powdered ceramic derivatives have been used as a pozzolanic material in concrete production. Brick/tile is produced from different types of clay and sand by adding other materials according to their properties. Clay, usually composed of 20%–30% alumina, 50%–60% silica, and the rest of other carbonates and oxides, is mainly responsible for the pozzolanic behavior of the brick/tile. While clay does not show pozzolanic properties in its chemical structure, it gains pozzolanic properties when clay and lime are fired together [12]. In applications such as the repair and rehabilitation of buildings, it is important to obtain high performance mortars to be used in some application methods such as shotcrete. In addition to the durability of the repair mortars produced, the environment it will be exposed to is also important (especially when a structure is exposed to severe marine and industrial environments). Their use has gained importance due to the presence of fibers of different sizes produced by using various materials in repair materials produced with cement, increasing the durability of the produced mortar or the produced concrete (depending on the properties and proportions used), albeit partially. More importantly, they have even more important contributions to reduce or minimize shrinkage cracking. Reducing or minimizing the development of shrinkage cracks can also help reduce the permeability of cementitious concrete or mortars due to the reduced crack state. Studies in the literature show that the compressive strength of the material produced by embedding some fiber types in mortar or concrete matrices decreases and as a result, the permeability increases. One of the important options for minimizing these negative changes is the need to use additional materials that can cause densification of the matrix structure of the mortar or concrete [13–15].

In the literature, different parameters of the waste brick/tile powders in the landfills or the mortar/concrete mixtures produced by using them as aggregates have been investigated [9,16–18]. It has been reported that mortars containing ground clay brick substitute, which can be produced in cement-based mixtures, have lower absorbency and chloride ion penetration rate than mortars without [19]. It is known that the alkali-silica reaction can be significantly reduced when 15%–25% of ground clay brick waste is added instead of cement [20]. On the other hand, in a study examining the replacement of clay brick waste and recycled waste powder from hardened cement paste with cement, scholars found that the shrinkage resistance of the mixture increased, but the chloride resistance decreased [21]. In a study examining clay brick powder in terms of pozzolanic reactivity, it was shown that clay brick powder could be used as waste with a certain pozzolanic reactivity due to its chemical structure. It has also been shown that the existing pozzolanic reactivity can be further improved by grinding clay brick powder to a greater fineness [22]. However, numerous studies have evaluated the effects of replacing cement with more than 25% by weight clay brick waste. It has been noted that the mixtures produced in this case will generally result in lower mechanical properties than is the case for normal mortar/concrete [23].

Ordinary Portland cement (OPC) is a dark gray binder that is frequently used in the production of building elements. Concretes with different properties such as exposed aggregate concrete, photogravure concrete, and colored concrete, which are frequently used as architectural concrete, have been developed for aesthetic reasons. Colored concrete is used in the general design elements of concrete structures, in elements with structural functions and as exterior cladding material. During the production of colored concrete, various colors can be created by the designer and architect with the help of various pigments in white Portland cement (WPC). The pigments are used to permanently color the concrete to be produced with different colors in order to change the color of the concrete [24].

In the literature, studies on WPC have been carried out for the evaluation of waste. In the study using granular blast furnace slag (GGBFS), it was stated that the GGBFS substitution rate affects the color value efficiency. It has been shown that a more yellow or red hue appears as the substitution rate of GGBFS increases, while greener colored concretes can be produced as the substitution rate of GGBFS decreases. With the use of GGBFS, the fluidity of colored mortars was improved compared to WPC, and an increase was observed in the fluidity values of the mortars with the increase of GGBFS replacement ratio [25]. WPC, which is considered indispensable especially for architectural concrete applications, has a minimum whiteness rate of 85% since it is produced from high purity raw materials [26,27]. In addition, high concrete surfaces of desired fineness can be obtained by using appropriate forms. It enables the preparation of successful mixtures with coloring pigments. In addition, thanks to the recycled materials obtained from the wastes to be used (as in the example studied above), it is possible to provide economy in terms of cost by both coloring and reducing the amount of use. Brick and tile production are distributed all over the country. Being an industry branch, it has more than 490 brick and tile factories as of 2000. However, given the number of brick and tile production factories and their extensive geographic locations, it is difficult to obtain their production data and to ensure these data are healthy. An average of 7.5 billion bricks and 700 million tiles are produced annually in Turkey. About 7% of these end up as waste [28].

The main purpose of this research is to evaluate the use of mortars produced by using recycled brick powder (RBP) and fiber in mortars produced using cements with different mechanical properties. For this purpose, the bricks/tiles stored as waste were collected from the landfills and shredded into powder. WPC CEM-I 52.5R and OPC CEM-I 42.5R were used in the mortars.

2 Materials and experimental study

Detailed explanations about the materials used and the methodology applied for the sampling are given under sub-headings. In addition, a brief description of experimental investigation is given in Fig.1 just before as a schematic workflow.

2.1 Materials

In the study, white CEM-I 52.5R type Portland cement was named WPC, and normal Portland cement CEM-I 42.5R was named OPC. The chemical and physical properties of the cement used in the mixtures are given in Tab.1. Crushed sand used in the mixture was sieved through a 4 mm sieve. In addition, the tile dust used in the mixtures was used in the mixture after sieving through a 0.125 mm sieve. Water and a superplasticizer, i.e., a polycarboxylate ether-based, highly water-reducing chemical additive (HRWR) were used in the production of all self-compacting mortars (SCMs) with workability properties according to the EFNARC [29] standard. The specific gravities of tile powder, superplasticizer and aggregate materials used in SCM production are 2.45, 1.055, and 2.68 t/m³, respectively. Blaine values were calculated as 3600, 4530, and 3050 cm²/g for OPC, WPC and RBP, respectively. The analysis of sieved and crushed sand is shown in Fig.2. X-ray powder diffractometry (XRD) was used to determine the mineral phases in the structure of RBP (Fig.3). XRD analysis was carried out with the Rigaku miniflex600 device.

2.2 Mix design

The produced SCMs were homogeneously produced with the aid of a standard mortar mixer meeting the requirements of the current standard [30] until the total homogeneity of the mixture was observed during the preparation of the components.

Mixtures with a fixed binder content of 600 kg/m³ and 0.42 water/binder (w/b) ratio were designed using OPC for both WPCs, as summarized in Tab.2. During the study, 0%, 10%, 20%, and 30% by weight RBP was used instead of cement and 32 mixtures with a water-cement ratio of 0.42 were formed. In SCM blends substituted with RBP, Polypropylene (PP) fiber was added at the rate of 1, 2, and 3 percent by weight of binder. Thus, a total of 32 blends were produced, 24 with PP fiber and 8 without PP fiber. HRWR was used to produce all SCMs with suitable machinability properties according to EFNARC [29].

2.3 Sample facture and mixing procedure

To produce the SCMs, all the components were homogeneously mixed with said mixer until they reached sufficient consistency requirements of ASTM C305/C305-20 [30]. Mixtures were tested for fresh properties immediately after they had sufficient homogeneity. V-funnel and mini slump flow tests were performed to determine the fresh properties. To determine the setting properties of the SCMs, fresh mortar was poured into prismatic and cubic steel molds. The samples were removed from the mold after 24 h and immersed in a water-filled curing tank until satisfying the appropriate test time.

2.4 Fresh state testing procedure

The control mixture consists only of cement, water, limestone-based crushed sand, and a viscosity grade superplasticizer. A total of 32 mixtures were made. Based on the control mixture, 4 mixtures (including control mixture) were designed by using RBP in the mixture instead of 10%, 20%, and 30% of the cement weight in the first group mixture. These designs were realized for both WPC and OPC blends. In the second part of the study, 12 extra blends were produced by adding 1%, 2%, and 3% of the binder weight of PP fiber to the mixtures designed in the first group mixture. A total of 36 blends were produced for both WPC and OPC. First, flowability tests were performed on fresh mortar mixes to determine self-compacting properties based on EFNARC [29]. Mini slump and mini-V funnel tests were conducted to determine the compliance of fresh mortar properties with standards.

First, a mini-slump test was performed to determine the filling capacity of the SCM with a 6 cm high top and bottom 7 and 10 cm diameter truncated cone apparatus to determine the fresh state properties of the SCM. The test specifications determine according to EFNARC [29]. The mini-slump test breakpoints used to check whether the SCM conditions are met should 24 and 26 cm be the minimum and maximum, respectively. Then, as a second stage fresh property test, the V-funnel test was performed to determine the viscosity of the SCMs. During the control of the SCM fresh state feature condition, the allowable limit values for the V-funnel test are given according to EFNARC [29] as 7 and 11 s for the minimum and maximum values, respectively.

2.5 Hardened state testing procedure

While the samples were in fresh mixture, they were placed in molds after meeting the SCM conditions, and after one day they were removed from the mold and put to cure in a water tank saturated with lime. Two curing times at (20 ± 2) °C were applied in these tanks. The first was 7 d, the second was 28 d. After the samples were removed from the tank, the first batch of samples were cured for 7 d, and the remaining samples were cured for only 28 d through water curing. Samples measuring 40 mm × 40 mm × 160 mm were used to test the strength properties of SCMs. The prism samples, which were first subjected to flexural strength tests, were used in two parts because of the flexural strength test and were subjected to axial compressive strength tests. For the curing age of 7 and 28 d, three 40 mm × 40 mm × 160 mm prisms were randomly selected for flexural strength testing according to ASTM C348 [31] for each design set. Then, the axial compressive strength test according to ASTM C349 [32] was performed on the parts consisting of broken prisms. Test views are shown in Fig.4.

Then, a total of 384 prism specimens with the dimensions of 40 mm × 40 mm × 160 mm were produced to perform the mechanical tests in the hardened condition (Tab.3). In addition, a total of 96 cube samples of 50 mm × 50 mm × 50 mm dimensions were produced for durability tests. Mechanical tests were performed on 7-, 28-, 56-, and 90-d. These prism samples were first subjected to flexural strength tests, and then the broken prism pieces obtained were subjected to compressive strength tests. To examine durability, porosity and absorbency tests were evaluated at 28 d of age.

2.6 Sorptivity

The sorptivity test is used to evaluate water penetration through the capillaries after the mortar/concrete has hardened [34,35]. In other words, the absorbency test is to measure the amount of water passing through the capillary spaces on the sample surface in the hardened state of the produced concrete or mortar. Cubic specimens measuring 50 mm × 50 mm × 50 mm are used for the sorption test. The weight gain from the sample’s water absorption over time is measured and plotted against time. The water in these capillary spaces moves inward from the surface with the gravitational force resulting from the contact of concrete/mortar surfaces with water. The values obtained can be used to measure the assessment of capillary voids in the internal structure of concrete/mortar samples. For this reason, it is one of the important criteria that shows the durability of concrete [34,35]. According to ASTM C1585-13 [33], 28-d samples were used to determine absorbency in cured samples. The samples used were in cube dimensions of 50 mm × 50 mm × 50 mm, and these samples were subjected to this test after 28 d of water curing. To prevent evaporation of samples at the end of the curing periods and to ensure uniaxial water flow, samples were kept in an oven at (100 ± 2) °C for 24 h until the sample weights remained unchanged. Then, four sides of the samples were covered with paraffin, while the other two surface sides were not covered with paraffin. One of the open surfaces is in contact with water at the bottom and the surface at the top is in contact with air (Fig.5). In the absorbency test of the samples, as specified in the ASTM C1585-13 [33] standard, the paraffinic surfaces of the samples were left in water not exceeding 5 mm from the lower surface. It was placed as shown schematically in Fig.5. To determine the amount of water absorption in the samples in contact with water, the samples were removed from the water after 5, 10, 30, 60, 240, and 1440 min and the weight changes were measured on a balance with a sensitivity of 0.01 g. The linear relationship between the measure Q (m³) is the amount of absorbed water and the square root of t (s) and time is given below (Eq. (1)). As indicated by k, it symbolizes sorptivity, while A denotes the cross-sectional area of the sample in cm².

(1)k=Q/(A \times \sqrt{t}).

2.7 Porosity and apparent density tests

Porosity and apparent density tests for concrete or mortars have been evaluated in studies in the literature. In these studies, by evaluating the experimental data of porosity and apparent density experiments, information can be obtained with theoretical calculations about the properties of concrete/mortar derivative productions such as cohesion, discontinuity and porosity. Therefore, thanks to these porosity and apparent density tests, a general knowledge about the durability of productions such as concrete/mortar is formed [36,37]. For this purpose, porosity and apparent density tests were performed on all samples prepared with SCM in accordance with ASTM C642 [38] standard. To calculate the values of the porosity and apparent density tests, the water weights and surface dry water saturated weights of the cube samples were measured. Weight measurements using the mentioned standard have been made by other studies in the literature from the past to present [39]. Finally, the samples were kept in an oven at (100 ± 2) °C for 24 h until their weights remained unchanged. The following equations were used to calculate the porosity and apparent density of the samples according to ASTM C642 [38].

(2)\mathrm{P}\mathrm{o}\mathrm{r}\mathrm{o}\mathrm{s} \mathrm{i}\mathrm{t}\mathrm{y}\left(\mathrm{\%}\right)=\frac{w_3-w_1}{w_3-w_2},

(3)\mathrm{B}\mathrm{u}\mathrm{l}\mathrm{k}\mathrm{d}\mathrm{e}\mathrm{n} \mathrm{s}\mathrm{i}\mathrm{t}\mathrm{y}=\frac{w_1}{w_1-w_2},

where w₁ is the final weight that the samples can reach at a constant temperature, w₂ is the measured weight of the fully saturated sample, and w₃ is the weight of the surface-dried saturated sample (Eqs. (2) and (3)).

3 Results and discussion

3.1 Fresh state test results

In Fig.6, test results of the workability properties such as mini slump flow diameter and V-funnel flow time of freshly produced mixtures are given. In Fig.6, the mini slump flow diameter shown on the left axis and the V-funnel flow time on the right axis are given. The limit values given by EFNARC [21] for these two experiments are limited by the red lines in the graph. The values obtained show that the flow diameters and flow times of all SCM mixtures are within the limits approved by the relevant standard (Fig.6). In the blends produced with WPC and OPC, the lowest flow diameters were obtained from the blends with 30% RBP substituted and 3% PP fiber additives. In these mixtures produced with WPC and OPC, the difference in flow diameters is negligible. Between these two mixtures, HRWR ratios are 5% higher than WPC in the OPC mixture. The highest flow diameters are seen in the control mixtures produced with WPC and OPC. In these two control mixes, the HRWR ratio was higher at 5.1% in the OPC control mix.

In addition, the HRWR used in providing fluidity plays an important role. At the mixture recipe, it is seen that it is used in varying proportions to reach the desired EFNARC standard. However, after a certain period of time, the connection between cement paste and aggregate deteriorates and causes segregation. For this reason, it is important to observe the amount of HRWR mortar to be used. The manufacturer of HRWR used in the mixtures produced recommends the upper limit of this ratio as 2% of the binder content. Therefore, these limits have been reached in the SCMs produced. On the other hand, the minimum times in V-funnel times were measured in mixtures containing WPC and OPC, while the highest values were measured in mixtures containing 30% RBP substitution and 3% PP fiber additives.

Schackow et al. [40] observed that blends with increased percentage of substitution increased water consumption with finer RBP content. Thus, it has been observed that the processability of SCMs decreases and it requires extra water or superplasticizer. Also, when using a fixed water/cement (w/c) ratio, up to 10% RBP substitution is recommended for machinability. Similarly, because of 10% RBP substitution within the scope of the study, the machinability shows the highest fluidity radius compared to others. It also creates the need for extra HRWR because of increased RBP substitution.

3.2 Flexural strength

The average flexural tensile strength values (f_ctf) of SCMs produced on the 7th, 28th, 56th, and 90th d. If the sample were not randomly selected from a large number of them in mass production, it would likely be somewhat biased, and the data might not be representative of the population. For this reason, 3 randomly selected samples from the relevant mixture from the sample stock were used for each experiment in this study. Results were calculated by averaging over the 3 samples from each mixture and are given in Fig.7. Maximum f_ctf values were calculated from M16, M16, M15, and M9 mixtures in 7, 28, 56, and 90 d experiments, respectively, in mixtures produced with WPC. The f_ctf values obtained from the mixtures were calculated as 4.377, 5.161, 7.364, and 10.37 MPa. When the maximum f_ctf values obtained from the mixtures of WPC and OPC for 7, 28, 56, and 90 d were compared, the f_ctf values obtained from the mixtures produced with WPC were higher. Results from blends produced with OPC were 20.49%, 11.65%, 5.49%, and 1.64% lower than the maximum values obtained with WPC at 7, 28, 56, and 90 d, respectively (Fig.7). In Fig.7, the change of f_ctf values obtained for WPC and OPC of each mixture during 7, 28, 56, and 90 d shows that the f_ctf values obtained from the mixtures produced with WPC are higher. Results from blends produced with OPC were, on average, 20.47%, 10.73%, 6.18%, and 1.62% lower than f_ctf values calculated relative to WPC-obtained equivalents at 7, 28, 56, and 90 d, respectively. Naceri and Hamina [23] found a reduction in flexural strength when used above certain ratios because of increased amount of RBP.

3.3 Compressive strength

The variation of the mean compressive strengths of SCMs where RBP was replaced by WPC and OPC for 7, 28, 56, and 90 d ages is given in Fig.8. Mixtures produced with WPC achieved 20% higher compressive strengths than mixtures produced with OPC in 7-d tests. In experiments performed at 28, 56 and 90 d of age, mixtures produced with WPC achieved 11%, 8%, and 6% higher results, respectively, than mixtures produced with OPC. Especially at later ages (56 and 90 d), adding 1% and 2% fiber to the mixtures made with WPC gives higher results than the equivalent mixtures made with OPC. O’Farrell et al. [41] reported that as a result of the increase in the amount of RBP in the cement mortar, the compressive strength values of the samples up to 28 d decreased compared to the reference mixture samples. However, they found that in 90-d samples, some mixtures with low substitution levels exceeded the compressive strength of the reference mixture. The basis of this effect was attributed to the formation of extra CSH gel due to the occurrence of the pozzolanic reaction, which caused the filling of the pores and hence the thinning of the matrix. Because of this filling, the connectivity of the capillary pores is significantly reduced. This pozzolanic effect is thought to be especially effective in SCM blends produced with both WPC and OPC, when the PP fiber addition is 3% and the RBP substitution is 10%. These blends are referred to as M14 and M30 in the list in SCM blends produced with WPC and OPC, respectively (Fig.8). According to Aliabdo et al. [42] stated that the compressive strength decreases with the increase of the RBP substitution percentage in cement mortar. O’Farrell et al. [41] and Aliabdo et al. [42], the trends of the data obtained as a result of the studies converge. In the study, it can be said that the compressive strength results of 10% and 20% RBP replacement for the 28- and 56-d results have almost the same values as the compressive strengths obtained from the samples of the control mixture. When the results and those of previous studies were evaluated, the improvement in the level of the pozzolanic reaction formed and developed with the RBP substitution rate may be due to it is active in the range of 10% to 20% at most.

3.4 Sorptivity test

Absorption, also known as capillary water absorption, is the term describing the tendency to absorb water in a sample due to the structural arrangement created by micro voids in the sample. Sorptivity is the key parameter showing the properties of permeability, which is an important parameter in durability. In the experiment performed on 50 mm × 50 mm × 50 mm cubic samples produced with SCM, the free water on their surfaces was measured on a balance with an accuracy of 0.01 g for 5, 10, 30, 60, 240, and 1440 min, respectively. After wiping the free water on the paraffin-coated surfaces with a dry cloth, mass changes were determined by measuring the mass increase. Fig.9 provides a graph of the measurement times versus the mass/surface ratio. In these graphs, water capillary permeability values for all SCMs are plotted for 1440 min in two groups of graphs, presented separately for both WPC and OPC mixtures (Fig.9(a) and Fig.9(b)). The sorptivity value was evaluated by determining the amount of water absorbed in the unit cross-sectional area of the sample during the measurements made during the test period. The experiment was performed for all SCMs after completion of the 28-d cure period. Sorptivity results are determined by averaging the results of 3 samples from each mixture. For blends with RBP substitution, the values of blends with WPC decrease on average 9%, 17%, and 24% for 10%, 20%, and 30% RBP substitution, respectively. In the second mixture group, mixtures with OPC, the values decrease by an average of 7.5%, 14%, and 20% for 10%, 20%, and 30% RBP substitution, respectively. In addition, when PP fiber is substituted, these values decrease by an average of 24% and 18% in WPC and OPC blends compared to control blends (Fig.9). On the other hand, when the other relationships of the remaining mixtures are examined, it is seen that the water absorption capacity decreases over time.

The sorption coefficients can be used as auxiliary parameters to examine these graphs more easily. By using the experimentally determined water absorption amounts and the change of measurement times, the values of the water mass absorbed by the surface are plotted on the graph. With the help of these graphs, the absorption coefficients are determined using the values given in Eq. (4).

(4)\frac{W}{A\times \rho }=S\times \sqrt{t}+I_0,

where W, A, and t are given as the increase in mass (kg), the area is checked (m²), and the time variable (min). S is the sorption coefficient of early age (mm/min^1/2), and I₀ is defined as initial sorption (mm) and \rho is water density (kg/m³) in Eq. (4) [43]. S and I₀ values calculated using the data obtained from Fig.9 are presented in Fig.10. The obtained data shows that because of RBP and PP fiber addition, it leads to a decrease in the amount of water absorption.

3.5 Porosity and specific gravity

While calculating the porosity values, we noted the ratio of the weight difference between the weights of the samples removed from the furnace at the appropriate temperature and the weights of the samples that were saturated with surface dry water to the sample volume. These values were obtained by averaging the three samples tested for each batch of mixtures. The variation between the porosity and the axial compressive strength obtained at 28 d of age and the mean values obtained from the flexural strength test are given in Fig.11.

With the RBP substitution added to the blends produced with WPC, the porosity values for 10%, 20%, and 30% RBP substitution decrease by 5%, 10%, and 12%, respectively, compared to the control mix. The 1%, 2%, and 3% polypropylene fibers (PPF) substitution used in these mixes makes the porosity value in the RBP substituted mixes 12.5% on average 12.5% lower than the control mix. On the other hand, the porosity values for 10%, 20%, and 30% RBP substitution in the mixtures produced with OPC decrease by 2%, 9%, and 14%, respectively, compared to the control mixture. 1%, 2%, and 3% PPF substitution used in mixtures with OPC, the porosity value in RBP substituted mixtures is 12% lower on average than the control mixture (Fig.11). According to the results obtained by López and Castro [44], the researchers’ predictions are that the reduction in permeability is much more important than the gain in strength when examining the effect of pozzolans. For this reason, it is wrong to specify the durability of concrete with strength or to expect an increase in strength due to higher strength when using pozzolan. The contribution of pozzolan is more in terms of reducing permeability rather than adding strength. This is because the hydration products of the pozzolans used in the mixtures contribute to the reduced connectivity of the pore system structuring, which occurs mainly in a mortar/concrete structure. In this context, it is observed that the durability of SCMs increases with increasing substitution rate of RBP. Because it is seen that there is a decrease in the observed porosity values. However, a negative effect on the compressive strength of SCMs was obtained. Decreased compressive strengths are observed with increasing RBP substitution. On the other hand, an observable increase in compressive strength was obtained with the addition of 3% PP fiber and 10% RBP substitutions (Fig.11(b)).

3.6 Statistical evaluation of the parameters

Variance analysis (ANOVA) is used to assess whether an independent variable influences the dependent variable. The general linear model analysis used in ANOVA is an important statistical analysis and diagnostic tool used to measure how dominant a control factor is by reducing control variance. In this study, the analysis was carried out using the 0.05 level of significance to identify statistically significant experimental parameters on slump-flow, V-funnel time, tensile strength, compressive strength and sorptivity coefficients. The contributions of the data obtained by experimentally tested samples to the measured test results are also presented in Tab.4. The data in the column under the contribution of the percentage give an idea of the degree of productivity on the response measured by independent factors. Therefore, the larger the rate in the relevant parameter, the more effective in the parameter. Similarly, if the value of the contribution percentage is low, the contribution of these factors to the result is more limited.

4 Conclusions

An experimental study was conducted to determine the fresh, mechanical and durability properties of self-compacting fiber reinforced mortars (SCFRMs), including RBP and PP fiber content. The results of the study conducted to show the performance change in RBP modified SCFRMs and to determine the effect of PP fiber addition to these blends are summarized below.

1) Values for the fresh state properties, namely the V-funnel and slump-flow diameter, indicated that the 30% RBP replacement level used maximum was the critical substitution point affecting the fresh state properties of the SCM. After this point, the increase in HRWR in the mixture was determined visually during the experimental study, which resulted in bleeding.

2) Increasing RBP substitution ratio in terms of compressive strength causes a decrease of 2%–11% depending on age in the mixtures with WPC from the control mixtures. The resulting rates of change in compressive strength are similar in mixtures with OPC.

3) On the other hand, when 1% and 2% of added PP fibers are used, they create higher compressive strengths in mixtures with WPC and OPC.

4) An increase in flexural tensile strength is observed based on age in mixtures containing 10% RBP substitution. After this ratio of substitution, there is a decrease in flexural tensile strength. This can be determined as the optimum RBP content for flexural tensile strength.

5) As a result of 30% RBP substitution and 3% PP fiber addition, the lowest porosity value is obtained. This situation can be determined as the mixture with the highest durability among the mixtures.

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