1 Introduction

After agriculture, building is the second-largest economic sector in India [1,2,3]. In the building sector, concrete play a major role in faster construction. In concrete, self-compacting concrete (SCC) play a vital role due to its flow and compaction under its weight. These are distinctive properties of SCC, which was created in 1988 and initially used in the construction industry [4,5,6,7]. There is no need for external vibration for the SCC process. Natural resource conservation in the current and future is a difficult task for the construction industry. Rather than being a consumable sector, the building industry must now become sustainable. The estimated production of building aggregates worldwide in 2015 was around 48.3 billion tonnes. About 70% of the volume of concrete is accounted for by aggregates [8]. Nearly 2.2–3 tonnes of slag are generated for each tonne of copper produced (source). Large amounts of copper slag are often dumped in landfills, causing pollution to the environment. A solution that is technically sound, environmentally friendly, and economically sound may be found in the use of waste copper slag (WCS) as a fine aggregate in SCC. Concrete’s resistance to chemical, biological, and physical disintegration might be considered its durability. The use of CS as fine aggregates in the creation of SCC is a unique aspect of the study. When it comes to building infrastructure, natural resources are always in short supply. The WCS can help alleviate that problem. The primary goal of this research is to use WCS to accomplish concrete's durability performance at a level that is equivalent to or better than concrete. Rajasekar et al. [1] UHSC with a compressive strength of moreover 150 MPa may be made utilizing untreated copper slag and treated copper slag as quartz sand, according to test results. The 30 CS-UHSC was shown to be more durable than a control quartz sand UHSC. Copper slag may be used for quartz sand in the production of UHSC [1]. Sharma and Khan [8] the minimal carbonation depth was found by substituting 100% CS and 10% MK for FA The experiment's outcomes. CS with 10% MK had lower initial surface absorption and sorptivity than control concrete during curing [8]. Gupta and Siddique [9] copper slag replaced natural sand, boosting strength by 10%. SCC durability was determined by water absorption, chloride permeability, and sorptivity. As long as the SCC mix included no more than 30% copper slag, the results were almost equal to a control mix [9]. Sharma and Khan [10] using six SCC combinations, a constant w/b ratio of 0.45, the copper slag was replaced by the SCC. When exposed to sulphate, concrete mixtures lose compressive strength while gaining weight. Reduced carbonation is one potential benefit of making steel from copper slag. Researchers believe that using 60% copper slag instead of ordinary sand might improve or maintain the long-term durability of SCC [10]. Najimi et al. [11] Expansion measurements, compressive strength degradation, and microstructure studies were performed in sulphate solution on concretes prepared with 0%, 5%, 10%, and 15% copper slag waste. This research suggests copper slag as a sulphate-resistant concrete substitute [11]. Mithun and Narasimhan [12] results demonstrate that AASC/CS mixtures may substitute sand up to 100% (by volume) with no discernible reduction in strength [12]. Brindha and Nagan [13] an M20-grade concrete was employed as a control in this study to compare the results. Increases in free water content in the mix result in lower compressive strength for larger percentage replacement levels of copper slag in cement (more than 20%) and in aggregate (greater than 50%) [13]. Chithra et al. [14]. Because nanosilica has a large specific surface area, it requires a lot of water. Colloidal nanosilica was shown to be an excellent filler and activator for pozzolanic activity. With a 2% nanosilica replacement level, the strength qualities are improved [14]. Sandra et al. [15] the results show that CUS substitution does not affect the mineral composition of the studied concrete mixes, indicating that it may be used with OPC blends. Adding copper slag fine aggregate to concrete as a way to dispose of industrial waste offers a wide variety of construction uses [15]. The behaviour of waste copper slag-based self-compacting concrete (SCC) must be evaluated according to the current literature. To bridge this gap, Waste copper slag is substituted for sand at 0%, 10%, 20%, 30%, 40%, 50%, 60%, and 70% in this study. SCC-WCS% was tested for compressive strength, bond stress, and durability tests of water absorption, sorptivity, and rapid chloride permeability were tested. Statically analysis is conducted on CMS with durability properties of SCC-WCS% mixes. The SCC-WCS% properties were determined using an XRD technique, and scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) morphology was found at 28 days of curing.

2 Experimental program

2.1 Materials

IS 269-2015 [16] specifies the OPC 53 grade for use in this study. Fly ash (FA) was supplied by VTPS in Andhra Pradesh, India. Tables 1 and 2 list the chemical and physical parameters of materials. Fine and coarse aggregates (diameters 10–12.5 mm) are gathered from the nearby area for the study. IS 9103: 1999 [17] calls for determining SCC-WCS percent combination characteristics in the lab using tap water and a 1.09-specific gravity HRWR.

Table 1 Chemical properties of materials for SCC-WCS mix
Full size table
Table 2 Physical properties of materials for SCC-WCS mix
Full size table

2.2 Mix proportion

A total of eight mixes, including a control mix, were prepared. Natural sand is replaced with WCS, which may vary from 0 to 70% in SCC. The ideal SCC mix ratio: 425 kg/m3 cement, 92.35 kg/m3 flash, 904 kg/m3 coarse-grain-crushed aggregates, 740 kg/m3 natural sand, 0.43 water to cement and PCE superplasticizer at 4.17 kg/m3 and tap water are used to mix for preparation. It takes around 8–10 min in a pan mixer to get a uniform mixture. EFNARC [20, 21], IS 10262: 2019 [22] and ACI-237R-07 [23] all state that flow qualities should be evaluated.

3 Research methodology

The entire research methodology is represented in a graphical form chart shown in Fig. 1. The various tests conducted and the methodology is discussed as follows:

Fig. 1
figure 1

Graphical chart of research methodology of SCC-WCS% mixes

Full size image

3.1 Mechanical strength

To assess the strength of the SCC-WCS% cube, samples are removed from the moulds and curing is done for 28 and 56 days until they are ready for testing in the lab. Compressive strength tests (CMS) are performed on 100 × 100 × 100 mm cube specimens made in the lab under IS 516:2015 [24]. For testing cubes, 100 tones of UTM of capacity are used for the study.

3.2 Bond stress

Prism specimens with dimensions of 100 × 100 × 100 mm were prepared for pull-out experiments as per IS: 2770 (Part I)—1967 [25]. In this experiment, the diameter of the deformed reinforcing bar was 12 mm, and the overall length was 900 mm are prepared as shown in Fig. 2. Bond stress between the SCC-WCS% mix samples to rebar pull-out test is conducted. The bond stress is the ratio of maximum pull-out force to the bonded area of the rebar. To calculate the bond stress is represented in Eq. 1.

$$\uptau =\frac{\mathrm{P max}}{\pi DLd},$$
(1)

where P max is the maximum pull-out load (N), db is the effective diameter (mm), and Ld is the embedded length.

Fig. 2
figure 2

Samples prepared for the pull-out test

Full size image

3.3 Durability tests

3.3.1 Water absorption

All concrete samples have been subjected to a water absorption test following IS 1124-1974 [26]. For testing, samples were kept at 105 °C in an oven to ensure that no moisture was present within the concrete. From Eq. (2), we can assess the water absorption of SCC-WCS% samples after 28 days of curing.

Wa = saturated sample wt (g) after 24 h of soaking, Wd = dry weight of the sample at room temperature.

$$\mathrm{Water Absorption }(\mathrm{\%}) =\mathrm{ W}\left(\mathrm{\%}\right)=\frac{\left(Wa-Wd\right)}{\mathrm{Wd}}\times 100$$
(2)

3.3.2 Rapid chloride penetration test

To know the chloride penetration of SCC with the incorporation of WCS from 0 to 70% (10% increment). A rapid chloride penetration test (RCPT) was conducted as per ASTM C1202-12 [27]. For testing the samples, 100 mm ϕ and 50 mm thick cylindrical concrete discs are prepared. Figure 3 illutrates the set for testing chloride penetration for SCC-WCS% mixes. Eight sets are prepared in SCC with WCS from 0–70% (10% increment). Each RCPT test set has five cells. As depicted in Fig. 4, each cell has a positive and a negative terminal, and 0.3 M of NaOH and 3% NaCl solutions are used in the study. When measuring the flow of electricity between cells, coulombs are measured. It is possible to determine how much charge travels through the SCC-WCS per cent samples using Eq. 3. The maximum current flow indicates low chloride ionic penetration resistance.

$$Q = 900 \left({I}_{0} + 2{I}_{30} + 2{I}_{60} +---+ 2{I}_{330} + {I}_{360}\right),$$
(3)

where Q = Charge passed (Coulombs). I0, I30, I60… I330, I360 = current at 0, 30, 60, –––, 330, 360 min.

Fig. 3
figure 3

Set up for RCPT test with cells for SCC-WCS% mixes

Full size image
Fig. 4
figure 4

Set up for sorptivity test for SCC-WCS% mixes

Full size image

3.3.3 Sorptivity test

Water penetration through the SCC-WCS% samples was determined using the sorptivity test according to ASTM C1585-13 [28]. To assess surface water penetration, four models of 100 mm ϕ and 50 mm thick cylindrical concrete discs are prepared in each set after 28 days of curing, and the test is conducted. Eight sets are assessed in SCC with the incorporation of sand with WCS from 0 to 70% (10% increment). The specimens were waxed on all sides except the surface, exposed to water penetration as shown in Fig. 4, and the sorptivity values were computed using Eq. (4).

$$\mathrm{S}=\frac{i}{\surd t}$$
(4)

S = coeff. of sorptivity (mm/min 0.5), i = cumulative water absorption and t = time (min),

3.4 Microstructure analysis

The sample’s crystalline structure and morphology must be studied using microstructure analysis. SCC-WCS per cent mix samples were analyzed at 28 days of curing for XRD and SEM in this investigation. In addition, XRD analysis was carried out on powder samples of SCC mixtures that heat-treated and ambient. The SEM, VEG3, and SBHTESCAN are utilized at 15 kN (or) 10 kN to explore backscattered electron imaging.

4 Results and discussion

4.1 Compressive strength (CMS)

The CMS values of the SCC-WCS% mix at 28 and 56 days are represented in Fig. 6. SCC with WCS as sand substitute represents an incremental trend in CMS compared to the control concrete (SCC-WCS0%) at 28, 56 days of curing. SCC samples made up of 70% WCS showed better compressive strength than those of 0% WCS. Incorporating WCS into SCC as a sand substitute significantly improved its strength at 28 and 56 days. At 28 and 56 days,SCC having 10, 20, 30,40,50,60 and 70% of WCS as sand has attained 13.63, 34, 42, 23,57,45,30% and 11.11, 31.94, 41.66, 22.1, 48.6, 33.33,27.77% greater to the pure sand-based SCC sample (SCC-WCS0%) in terms of strength. The w/c of 0.43 provides a homogeneous mix with high workability in the SCC-WCS mix, which improves strength. Chemical reactions involving reactive silica and alkali calcium hydroxide produce calcium silicate and aluminates, which are then formed in the cement paste. Enhanced compressive strength is achieved by the chemical interaction of ITZ with calcium silicate and aluminium oxide hydrates [29,30,31,32,33]. Copper slag's high density and texture are further factors [5, 34,35,36,37,38]. Figure 5 illustrates the SCC samples containing 0%, 30%, 40%, 50%, 60% and 70% WCS spots. By substituting copper slag with sand from 0 to 100% concrete at w/c ratios of 0.45 and 0.55, the maximum strength values of 50.2, 48.2, and 50.2 MPa were achieved when using 20–60% of the CS, compared to 0% in traditional concrete [35]. There was a reported increase in stress in self-compacting concrete of up to 30% with sand replacement [38] and up to 20% with cement substitution at 28 days of curing the concrete because of the high cost of cement and environmental protection [3, 39].

Fig. 5
figure 5

The cross-sectional view WCS spots in SCC-WCS mixes: a WCS 0%, b WCS 30%, c WCS 40%, d WCS 50%, e WCS 60%, f WCS 70%

Full size image
Fig. 6
figure 6

CMS for SCC-WCS% mixes

Full size image

4.2 Bond stress

The bond behaviour between concrete and rebar pull-out test is conducted [40,41,42,43,44]. In SCC with replacement of sand with WCS from 0 to 70% for that bond behaviour and stress of SCC-WCS% with rebars are observed. Figures 7 and 8 represents the experimental data of pull-out load and bond stress of SCC-WCS% mixes at 28 days. Using the WCS content, the bond stress and pull-out values are increased compared to the control concrete (SCC-WCS0%). The maximum pull-out load range between 27.12 to 44.35 kN and the bond strength range from 7.198 to 11.766 MPa are shown in Figs. 7 and 8. At 28 days curing bond stress, SCC having 10, 20, 30, 40, 50, 60 and 70% of WCS as sand has attained 20.86%, 49.34%, 60.50%, 63.46%, 60.32%, 53.50% and 42.86% compare to the control concrete (SCC-WCS0%) as shown in Fig. 8. The bond stress values of SCC replacement with WCS from 10 to 70% show more resistance in strength compare to IS:456:2000 [45].

Fig. 7
figure 7

Pull-out load for SCC-WCS% mixes

Full size image
Fig. 8
figure 8

Bond stress for SCC-WCS% mixes

Full size image

4.3 Water absorption

Figure 9 depict the water absorption of SCC-WCS% at 7 and 28 days of curing. SCC mixes incorporating WCS% content as sand show a reduction in the water absorption values up to WCS50% and a slight increase at WCS 60% and WCS 70% both at 7 days and 28 days of curing. The SCC mixes with 0,10, 20, 30, 40, 50% of WCS mixes have shown 13.33%, 9.6%, 8.5%, 7.69%, 6.8%, 6.5% and 13%, 9.1%, 7.9%, 7.3%, 6%, 5.8% water absorption rate compare to control concrete (SCC-WCS 0%) at 7 days and 28 days of curing period.WCS percent has a low water absorption rate, resulting in the production of a denser structure with fly ash [1, 2, 8, 37]. The concrete's water absorption value improved somewhat at WCS 60% and WCS 70% when copper slag was used. When copper slag percentages were increased in SCC combinations, the free water content increased, resulting in more voids. The increase in water absorption rate is negligible compared to SCC mixes with 100% sand. For 28 days, the water absorption rate in WCS 100% sand (WCS0%) is 13%,in WCS 60% and 70%, the rates are 7% and 8.5%. This might be owing to the reduced surface absorption of waste copper slag particles compared to sand, which could lead to an increase in water absorption.

Fig. 9
figure 9

Water absorption (%) for SCC-WCS% mixes

Full size image

4.4 Rapid chloride permeability test

SCC chloride ion permeability was measured using RCPT with sand replacement WCS ranging from 0 to 70%. (10% increment). Table 4 shows the RCPT, standards as per the following ASTM C 1202-07 [27]. Table 3 displays the results of the RCPT SCC-WCS percent sample. Figure 10 indicates a decrease in chloride ion permeability with WCS replacements for fine aggregates. The higher chloride ion penetration was observed for WCS 70% samples in term charge passed 1090 coulombs. SCC mixes including up to 40% copper slag showed a substantial reduction in RCPT after 28 days. By reducing pores, copper slag reduced concrete’s permeability [9]. Adding WCS reduced water absorption by up to 50%, according to the experiment results. All SCC mixes had low chloride permeability at 28 days. The coulombs ranged from 880 to 1340 FA and WCS percent mixes of SCC exhibited better chloride ion combat than other SCC-100% sand blends in Fig. 10. The addition of particles such as fly ash and copper slag may have increased the matrix's particle packing density, reducing chloride ion penetration. Chloride iron penetration in Self Compacting Concrete was greatly decreased as a result of the addition of Flyash and WCS to the microstructure and improved pore structure. A decrease in RCPT values was seen in a fly ash-based geo polymer mortar with nanosilica additions [32] because the mixture included more crystalline components. Slag admixed concrete has been rated “extremely poor” in terms of its quality. As a result, it suggests that slag additive concrete has a lower permeability. The slag minimizes the pores in the concrete and makes the concrete impermeable [13].

Table 3 Chloride ion permeability values for SCC-WCS% mixes
Full size table
Table 4 Chloride ion permeability as per standards
Full size table
Fig. 10
figure 10

Charge passage of coulombs for SCC-WCS% mixes

Full size image

4.5 Sorptivity test

Sorptivity’s endurance is connected to water absorption through capillary pores in the microstructure. Capillary pores in the microstructure of concrete are primarily responsible for concrete's adsorption capacities. When the volume of capillary holes is greater, the sorptivity is bigger, and the likelihood of concrete degradation increases [10]. At 28 days of curing age, about 30%, 39.23%, 43.84%, 53.84%, 55.38%, 46.15% and 34.64 % of decrease was observed in the water absorption corresponding to WCS10%, WCS20%, WCS30%, WCS40%, WCS50%, WCS60% and WCS70% with respect to control concrete (WCS0%) represents in Fig. 11. Concrete with a sorptivity of SCC-WCS0 percent i.e. 0.032 mm/min0.5 sorptivity for 28 days For SCC-WCS10% to SCC-WCS70%, the lowest values of sorptivity were 0.02, 0.017, 0.015, 0.013, 0.017, 0.021, and 0.029 mm/min0.5 at 28-day curing age, respectively. Compared to control concrete, surface water absorption decreased 37.5, 46.8, 53.1, 59.3, 46, 8, 34, and 25% after 28 days of curing age (SCC-WCS0%). Capillary pores in the microstructure are discussed in sorptivity and water absorption whereas water absorption at the concrete surface under a gradient of pressure head is established. To understand how SCC mixtures perform, it is important to understand how void volume and pore microstructure affect the mix's durability. Water absorption and sorptivity were shown to increase after WCS60% and WCS70%. There was a decrease in durability up to WCS50% due to reduced water absorption qualities and WCS’s larger grain size than natural sand, which increased voids, capillary channels and interfacial transition zone thickness [10].

Fig. 11
figure 11

Sorptivity values of SCC-WCS% mix samples

Full size image

4.6 X-ray diffraction

X-ray diffraction (XRD) techniques was evaluated on phase are tested in the hardened SCC matrix with sand replacement of WCS% from 0%, 10%, 20%, 30%, 40%, 50%, 60% and 70%. For XRD investigation, powder samples were taken from each SCC-WCS per cent combination after 28 days of curing. We utilized 2θ that spanned from 5° to 90° to conduct XRD analysis. Figure 12 Xrd peaks of SCC-WCS% mix samples. The multi-peaks in the SCC-WCS per cent combinations may readily be seen using XRD analysis. Peak phases in SCC combinations include quartz (Q), anorthite (A), calcium hydroxide (C), calcium silicate hydrate (C-S–H), portlandite, and silicon oxide. The main peaks with 2θ at 26.6° of quartz refer to the hexagonal structure. At WCS 40%, the main peak phases of quartz represent crystal structure showing an increment in the strength of SCC mixes other phases C-calcium hydroxide and CSH-calcium silicate hydrate was observed in the SCC mixes [5, 9]. XRD pattern of the SCC-WCS% of mixes of different elements diffraction shows peaks at 2θ value for C is 18.08° and Q is 26.63° which was associated with the hexagonal crystal structures. C–S–H associated with semi-crystalline to normal amorphous structure shows peaks of 2θ value is 27.99° and A-anorthite associated with triclinic crystal shows peaks of 2θ value is 27.5°. Table 5 represents the Xrd diffraction characterizes SCC-WCS% mixes.

Fig. 12
figure 12

Xrd peaks of SCC-WCS% mix samples

Full size image
Table 5 Xrd peak characterizes SCC-WCS% mixes
Full size table

4.7 SEM/EDS analysis

SEM/EDS analysis is done for SCC-WCS% mixtures of the concrete matrix. The microstructure images of SCC mixes are done at 28 days of curing with WCS% content 0%, 20%, 40%, 50% and 70%. The SEM images at 28 days at magnification range from 1.0 to 4.0Kx are investigated. Figure 13a presented the morphology of SCC with WCS0% leads to the formation of C–S–H layers, ettringite, and voids observed. Figure 13b presents the formation of C–S–H gel and ettringite for SCC-WCS20%, and micro-cracks are observed. As the WCS% content is increased further, shown in Fig. 13c at WCS40% observed denser homogenous C–S–H gel and voids. Accumulation of the C–S–H layer makes the concrete denser, leading to an increment in CMS. Having Si and Ca in the concrete matrix phase results in a dense amount of CSH gel at the IT zone and aluminosilicates gel [35], which increases the mix’s strength, and having Fe available in the mixture of 40% of WCS in SCC, but this hasn’t shown any effect on the mix’s strength characteristics. Figure 13d shows the presence of voids and denser C–S–H layer formation observed at SCC-WCS 50% in the SCC matrix under the SEM image. Figure 13e represents SCC-WCS70% shows voids, micro cracks and C–S–H gel formation in the SEM image.

Fig. 13
figure 13

a–e SEM image of SCC-WCS% mix samples

Full size image

Figure 13a–e illustrates the SEM images of SCC mixes at replacements sand with WCS% from 0%, 20%, 40%, 50% and 70%. All replacement levels resulted in denser and more homogeneous concrete mixtures [9]. Ettringite and voids were detected in SCC mixtures including more than 50% copper slag in place of sand. Improvements in the CMS of the SCC matrix are observed from SEM images of denser and homogenous C-S–H gel formation in the concrete matrix with all the replacements of sand with WCS compared to the control concrete (without WCS) [35, 36, 38, 46].

In EDS analysis, Fig. 14a shows that Al, Si, Ca, C and O lead to ettringite formation under EDS analysis. Figure 14b represents Ca, Si, S and O peaks observed in the EDS analysis of SCC-WCS20%. Figure 14c represents the major peaks of Si, Ca, Al, S, C and O; observed these elements lead to the formation of denser C–S–H gel in the concrete matrix; it is seen in SEM image Fig. 13c. Figure 14d illustrates dense C–S–H gel formation and voids, but CMS is more than the control concrete (SCC-WCS 0%). The major peaks of Al, S, Ca, C and O are observed, leads the formation of the C–S–H layer in EDS analysis in Fig. 14d. Figure 14e shows S, Al, Ca and O peaks in WCS70% in the SCC matrix. Figure 14a–e showed the elemental composition of SCC-WCS% from EDS analysis with peaks present, Al, Si, Ca, and C indicates the increment in the CMS with the incorporation of WCS%.

Fig. 14
figure 14

a–e EDS analysis of SCC-WCS% mix samples

Full size image

5 Statistical analysis

Compressive strength and RCPT (charge passed) values, water absorption, and sorptivity of SCC mixtures containing copper slag were studied using linear regression analysis for values up to 28 days of curing. Figure 15 shows the correlation coefficient (R2) of 0.882 between CMS and water absorption. Figure 16 shows a relationship between compressive strength and RCPT values. Compressive strength was found to have a correlation coefficient of 0.908% with the RCPT values (Fig. 16). Water absorption, chloride ion permeability, and sorptivity, all of which are indicators of long-term durability, decrease with increasing strength. This added credence to the testing results for strength and durability. The analysis of the connections between several durability qualities revealed the interdependence of their effects.

Fig. 15
figure 15

Correlation of CMS vs water absorption in SCC-WCS% mixes

Full size image
Fig. 16
figure 16

Correlation of CMS vs charge passed (RCPT) in SCC-WCS% mixes

Full size image

Figure 17 shows that the sorptivity of CMS and the charge passed in SCC mixes are closely connected with coefficients of 0.996 and 0.896, respectively. In Fig. 18. Linear regression analysis demonstrates a correlation coefficient of 0.905 and 0.84 between the water absorption of SCC mixes and the RCPT (charge passed) values and sorptivity during 28 days. Water absorption was decreased due to a reduction in the number of pores and gaps in the concrete matrix. Incorporating WCS and fly ash may lower the system’s chloride-ion permeability. Increasing the porosity of SCC results in an increase in its strength properties [9, 47].

Fig. 17
figure 17

Correlation of sorptivity coefficient vs CMS and charge passed in SCC-WCS%

Full size image
Fig. 18
figure 18

Correlation of water absorption vs sorptivity and charge passed in SCC-WCS%

Full size image

6 Conclusion

The objective of the present research is to study the behavior of SCC with copper slag waste as a secondary source of fine aggregates from 0 to 70% in the mixes for ensuring a sustainable environment. The parameters are bond behaviour, mechanical, durability and microstructural properties of concrete carried out in this research.

These conclusions can be drawn as a result of this investigation:

  1. 1.

    Having a more significant amount of silica hastened the CMS improvement. Due to this, WCS achieves peak strength at an earlier age than conventional concrete. The compressive strength of SCC-WCS, which substitutes WCS for 40% of the sand, has improved.

  2. 2.

    When copper slag was used to replace up to half of the SCC, the water absorption was significantly decreased. With 40%, and 50% WCS, the absorption rate dropped by 6.8%, by 6%, and by 6.5, 5.8% at 7, 28 days of age. Due to WCS's lower water absorption and varied gradation, voids, capillary channels, and interfacial transition zone thickness were increased.

  3. 3.

    The sorptivity of SCC mixtures including copper slag reduced after 28 days. After 28 days, decreases of about 47%, 50%, 59%, 50%, and 37.5% were recorded at slag replacement rates ranging from 20 to 60%. Although the maximum sorptivity values decreased by 59% at a WCS concentration of 40%, they remained higher than the control concrete (WCS 0%).

  4. 4.

    In the SCC-WCS% samples, the chloride permeability is very low up to 40% WCS content at 70%WCS is low. Due to its low value, the primary causes of steel corrosion in reinforced concrete structures surface passive layer is more effectively used as a sand replacement up to 40% in SCC.

  5. 5.

    SEM/EDS and XRD studies demonstrated that C–S–H production filled all of the capillary layers and produced thick concrete with all of the microcracks and holes present in dense structures. In addition, due to a solid pozzolanic reaction and SCC-WCS percentage of 40% to 50%, the SCC mix was effective compared to the control concrete.

  6. 6.

    CMS and durability characteristics showed good statistical connections with water absorption, sorptivity values, charge passed (RCPT) of SCC validating the results obtained.

This study suggests up to 70% is used as WCS substitution with sand compared to control concrete for the development of SCC due to better durability properties. The past researchers have recommended the optimal content of 40% as fine aggregates for normal vibrated concrete and high-performance concrete and 20% for SCC.