The improvement of concrete strength through the addition of sustainable materials (agro-waste loaded with copper ions)

The country’s rapid industrialization and urbanization stimulated extensive infrastructure development. This technique results in a shortage of construction materials, increased trash generation, and other side effects. The production of long-lasting and environmentally friendly plain concrete slabs is a critical requirement for this task. It is intriguing to observe that the ions of copper in wastewater added to agro-waste (waste tea leaves) can be used to boost the compressive strength and plain concrete slabs’ workability (or walls) as sustainable materials. Waste tea leaves+Cu were incrementally added in 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 1.3%, and 1.75% by weight. Casting and testing 36 specimens (12 sets x 3 specimens) for seven- and twenty-eight- days strength. The results indicate that the strength of the sample with 0.7% waste tea+Cu is 55% and 15% more than the reference and that having only tea leaves pieces after seven days, respectively. In contrast, the 0.7% group had 46 percent and 20 percent greater strength after 28 days. These findings propose an innovative approach to dealing with toxic trash and give an accessible, practical, cost-effective, sustainable, and ecologically acceptable way of removing numerous forms of garbage.


Introduction
Concrete continues to be the major dominant factor in the development of construction, in spite of the contribution of steel or wood as contributing factors.Because of this, researchers in the twentieth century focused on developing concrete characteristics physically and chemically; this is a topic that relates to the process of putting up structures in places such as buildings, bridges, motorways, dams, and even nuclear reactors.In order to get the best conception of the structural behavior of concrete and to evaluate the good and negative aspects of this fundamental substance, a significant number of investigations and regular observations have been conducted and have produced substantial findings (concrete).These researches are important for several reasons.One is the potential to find new ways to develop this behavior by employing economically viable and environmentally benign methods to produce concrete from an environmental remnant [1].Environmental concrete is currently important as a result of the increased focus on the subject, which is essential for examining the impact of environmental waste on the physicochemical properties of concrete.This focus on the subject is essential for understanding why environmental concrete is currently significant.The building and construction sector helps improve the surrounding environment's quality.Keeping the industry's expanding interest in production at a state of expansion requires using waste materials in concrete additives and admixtures in an innovative and efficient way [2].In the quest 2 to enhance concrete while keeping the environment clean, individuals concerned about the environment being green have begun to focus on additives derived from environmental or agricultural leftovers because these additives have recently become the focus of those concerned about the environment and identified as a significant source of sustainable energy sources [3].Used tea leaves that have been discarded represent one of these environmental organic wastes.Because it is affordable, biodegradable, and available in vast amounts all over the world, waste tea leaves have the potential to be utilized as an additive in concrete to improve the concrete's properties.Additionally, it might make it possible to get rid of this agricultural waste in a way that is both economical and kind to the environment [4].Several lines of investigation are focused on determining how well certain additions work in conjunction with concrete admixtures and analyzing the results.Nasr et al. 2019 investigated the impact of using black tea waste ash as a partial cement replacement.There were five different mixing ratios tested.Their findings revealed that compressive strength values improved by up to 7.5% replacement.In contrast, the compressive strength values for 10% replacement were the same as for control specimens [5].Banu et al. 2020 conducted another study to test long-term concrete strength using three different agro-wastes (rice husk ash, de-oiled earth, and spent bleach earth).The authors created ten different combinations.They discovered that using 7.5% rice husk ash and de-oiled soil as a cement substitute improves compressive strength over control [6].Maglad et al. 2023 recently studied the effect of sugarcane bagasse ash and corn stalk ash on the properties of the strongest concrete.Three different agro-waste percentages were used.The authors demonstrate that their findings result in the production of concrete with a high compressive strength when compared to the control sample [7].Tea leaves that have been discarded are included on this list.The fact that waste tea leaves contain more percentage of cellulose, which can block the holes of the concrete that contains more than 90 percent silica, provide good water resistance capabilities by reducing the amount of water that can penetrate the concrete by up to 60 percent, and minimize the amount of water heat, may provide a significant advantage.In addition, it prevents the erosion of reinforcing steel, restricts the entrance of chloride ions, minimizes the production of fractures during concrete casting, has a high resistance to chloride, and limits the amount of chloride that can enter the concrete [8][9][10].This research investigates whether or not it would be possible to produce an addition for a basic concrete slab by using waste tea leaves residues that have been loaded with the element copper (Cu) and obtained from polluted water (wastewater).This work investigates the properties associated with concrete compressive strength for the cubic model.It is possible that the utilization of discarded tea leaves as a means of removing heavy metals (copper) from wastewater could be regarded as an original approach to increasing the strength of concrete.This study represents a new step towards making the most of agricultural waste in a sustainable manner.The agricultural waste was used to prepare adsorbent materials to remove minerals from the wastewater.The new step in this study is to use the adsorbent material loaded with the mineral element as an environmentally friendly additive to the concrete mix.The effect of the additive on the compressive strength of the prepared samples was also studied.The additive was developed as a direct result of this work.

Cement
In this study's experimental work, the locally produced Portland cement (Tasluja type) was used.The chemical properties were explained in table (1), while the physical properties were described in table (2) of this type, which was examined by [11] and compared to Iraqi standard 5/1984 [12].

Cu-waste tea leaves
Waste tea leaves (its composition shown in table 5) collected from domestic use can be repurposed through a very ingenious process if they are first loaded with copper and then collected.Copper was loaded onto waste tea leaves by applying the adsorption process, which may be carried out on aqueous solutions in various situations (as a concrete additive).The used tea leaves have been found to contain anything from 7.241 to 126.70 g of the element copper (Cu) per cubic meter of concrete sample.Aqueous solutions recover 10 milligrams of copper (Cu) per gram of discarded tea leaves.A full day and a night in the dryer.After extraction, the substance was sieved with a 200-micron mesh.In the final step, the powder is sealed away from moisture in bags before being used to produce the concrete admixture.The milling process was carried out using a domestic electric grinding machine.

Water
In this particular investigation, water from the tap has been used to prepare the concrete models' mixtures.

Research method
The cementitious mixture samples were prepared with a 0.45 mixing ratio of water-cement and Cuwaste tea leaves with a weight that ranges from 0.1 percent to 1.75 percent of the mixture weight (The tea leaves addition percentages were used with a fixed increase of 0.1% between each percentage until reaching 0.8%.Because the compressive strength began to decrease after 0.7% (starting from 0.8%), a rate of 1.3% was taken to find out the decrease in the compressive strength at this percentage, which is a difference of 0.5% from the last percentage.Hence the 1.75% rate at which the model fails immediately) and is applied in the current experiment to improve concrete samples' attributes.In addition, the ratio of cement to sand to coarse aggregate that is used in the mixing process is 1:2:4.Table 6 presents the information regarding the concrete mixtures that were used in the experiment in greater detail.After being thoroughly rinsed with water to remove any remaining dirt, the coarse and fine aggregates are then exposed to the sun for twenty-four hours to complete the drying process.After ensuring that the aggregates are devoid of any moisture, the cement, fine aggregates, and Cu-waste tea leaves are mixed together to create a dry mixture.Following that, the mixture is transferred to a 25kilogram concrete mixer.The blended materials are then mixed with two-thirds of the weight of coarse aggregate until they reach an appropriate degree of homogeneity.The process of mixture mixing still continued after adding the final quantity of water and gravel to the mixture until it was uniform throughout.For the purposes of determining a material's compressive strength, a sample of iron in the form of a cube is used as a model in line with the requirements of the British standard (B.S-1881: Part-113, 2011) [14].When making homogeneous concrete, the steel molds are packed with cementitious material in three layers and mechanically pounded with a vibrator for ten to fifteen seconds.This creates a uniform consistency throughout the concrete.Following the completion of the casting process for cubes, the molds are then coated with nylon for a period of twenty-four hours.Following that, the samples are transferred from the models (the molds) and aged in basins carefully prepared and filled with tap water between 20 and 25 degrees Celsius.Until age days of seven and twenty-eight, which are test days, the various samples are kept in maturation basins.

Testing method (The compressive-strength-test)
The thirty-six cubic models prepared in this study explore the influence of Cu-waste tea leaves as an additive to the hardness of concrete through the concrete compressive-strength test, which is then applied to models of concrete slabs.Each of the twelve groups of a concrete mixture is formed of three cubes with dimensions of 150 mm on each side and 150 mm on all other sides.The BS.EN.12390-3-2019 [15] specifies that the water curing period is seven days, while the curing period at 20 °C is twentyeight days.The concrete samples cubes' compressive strength tests are carried out after seven days and after twenty-eight days using the Wekob (2500 kN) procedure with a rate of fifteen meganewtons per square meter per minute (MN/m2/min) until the cube model breaks.Three different cubic samples are used to compute the compressive results of each combination at two ages (seven days and twenty-eight days).When the concrete compressive strength was calculated, three different concrete cubes' average resistance was used.

The compressive strength test:
As a simple and elementary value, the fine grains will improve the compressive strength when added to any concrete mixture in a restricted percentage, such as ground waste tea leaves (without Cu loading).This is true even if the fine grains come from waste tea leaves.This is because the addition of such material needs more amount of water that is added, which, in turn, so the concrete compressive strength; as a result, was reduced.The reason for this is the fact that the addition of such a substance necessitates a rise in the amount of water that is added.Compared to the concrete cubes used as references, the findings of this research reveal that the concrete cubes show an increase in compressive resistance after both ages (seven days and after 28 days).As shown in figures 1 and 2 the strength was improved by 35% and 22% for samples with tea leaves without Cu ions for both seven days and after 28 days, respectively, compared to the control.While for other cubes, when the tea leaves contained Cu ions, the improvements started from 25% to 18%, then reached the maximum of 55% and 46% for seven days and after 28 days, compared to the control sample.After that, the strength decreased, and finally, the cubes containing a high quantity of tea leaves failed.These findings were in agreement with previous studies [5 and 6].This discovery runs counter to what was anticipated to take place.The quantity of copper that can be recovered from used tea leaves can have an increased concentration of up to 0.7 percent at most.Following that, the cubic models show decreases in the resistance until it fails at a value of 1.75 percent when exposed to the Cu -waste tea leaves, as demonstrated in Figures ( 1 and 2) for the control concrete sample and the Cu -waste tea leaves concrete mixes, respectively.This behavior could be explained by the reality that the waste tea leaf grains fall between the fine and the coarse aggregate and overlap with them, resulting in the most gradation.Another possible explanation for this behavior is that the grains of the waste tea leave may have been contaminated with mold.This is yet another reason that might be given for this behavior.Therefore, as a result of this, the concrete structure's gaps are reduced, and as a result of this, the quality of the concrete mixture has been enhanced; typically, the pores abound in the concrete mixture, which contributes to the deterioration of the concrete structure.Therefore, as a result of this, the concrete mixture's gaps are reduced, and as a result, the structure of the concrete mixture is improved.Because of this, the utilization of fine-grained waste tea leaves has the potential to begin filling and reducing these gaps.Consequently, the concrete mixture's homogeneity is improved and, consequently, the concrete's resilience [7].This is because of the fact that fine-grained waste tea leaves have a smaller particle size.
In addition, a rise in the hardness of the concrete made from the copper-waste tea leaves may result in an increase in the fastening strength between the particles of the waste tea leaf that are loaded with copper and the cement particles in the concrete, and this depends on the general properties produced as a result of the compositional content of used tea leaves.The alternative theory that could account for these findings involves a substance known as a copper ion (Cu), a high-density element that, when it dissolves into the concrete admixture, increases the concrete's resistance to deterioration over time.
There is a widespread consensus that copper possesses a high specific gravity.For both ages (seven-and twenty-eight-days), as explained in figure 3, the results of the concrete compressive strength for the Cu-waste tea leaves added to concrete was increased compared to other samples (reference and sample used waste tea leaves without Cu).The increasing percentage for 7-days age was 55% and 15% compared to the reference and sample used waste tea leaves without Cu, respectively.While for the 28-day age samples, the increase was 46% and 20%, respectively.These results prove the waste materials' visibility in improving concrete compressive strength.

Conclusion
Through the above, we conclude the following: 1. 1.The efficiency of Cu-waste tea leaves, also known as CWTL, in the plain concrete slab was demonstrated, implying that it could be used as a supplementary additive material for the plain concrete slabs.2. The results of the concrete compressive strength tests show that the 0.7% concrete with waste tea leaves+Cu is 55% and 15% more than the reference sample and sample with only waste tea leaves for seven days.3.For 28 days, the 0.7% group had 46% and 20% more strength than the reference sample and sample with only waste tea leaves.4. The compressive strength was affected negatively when the tea leaves increased more than 0.8% and failed at 1.75%.5.The results proved that different types of waste could be disposed of using sustainable methods in other fields, such as what was done in this study.

Table 1 .
Cement chemical investigations results

Table 2 .
Cement physical tests results

Table 5 .
Chemical composition of waste tea leaves

Table 6 .
Concrete mixture content