Concrete is one of the most important building material in the construction industry. Conventionally, it is produced using coarse and fine aggregates, water, cement, and other admixtures, which are adopted with the objective of improving strength and other specifications, such as durability. Some of the essay writer characteristics of the concrete produced using these materials include little to no flexibility, relatively high unit weight, high durability and weathering resistance, and low degree of porosity (Thomas & Gupta, 2016). With advances in technology, various attempts have been made with the goal of improving the performance of concrete. Some of the improvements, which are already in use include the use of admixtures to lower hardening time and to increase strength. Notably, with advances in technology, it is still possible to enhance the performance of concrete.
Problem Statement
The majority of the course and fine aggregates used in the production of concrete are obtained from quarries. Rivas-Vázquez, Suárez-Orduña, Hernández-Torres, and Aquino-Bolaños (2015) assert that quarrying has various adverse effects on the environment, which ranges from land degradation to air and water pollution. Other noticeable negative effects of quarrying include occupational noise pollution, landslides, land subsidence, and the loss of biodiversity. Ultimately, some of these effects, especially air and water pollution have far-reaching consequences on the wellbeing of the people around the quarry sites. With the rising concerns regarding global warming and the associated effects, there is the need to come up with mechanisms to reduce the human activities related footprints to the environment. To achieve this objective, there is a need to reconsider the materials used in the production of concrete, especially the fine and coarse aggregates. Waste rubber tires, which also have various adverse effects on the environment, such as land degradation can be used as a partial substitute for coarse aggregates.
Methodology Description
This technology reports aims at shedding more light on how the treated waste tire can be used as a partial substitute for coarse aggregates in the production of concrete. Some of the features, which makes concrete one of the most important construction materials include durability, high comprehensive strength, fire resistance, and waterproofing capabilities. On this account, the partial replacement of course aggregates with treated tire waste will be considered a success when the resulting concrete will satisfy the majority of the characteristics of the conventional concrete. In this report, compressive strength and durability will the main parameters of interest. While the comprehensive strength of concrete prepared using the treated tire waste will be verified through the cube crushing experiment, the durability will be ascertained using the water absorption test.
This technology report will aim at achieving a concrete strength of 25 N/mm2 in 28 days while using treated waste rubber as a partial substitute for concrete. The first step in this endeavour will be to obtain waste concrete tyres. The crump waste tires will then be treated using organic sulfur compounds. Notably, these compounds will be used with the objective of strengthening the rubber-cement bond. Upon the completion of the treatment of process, dry aggregates (both coarse and fine) will be batched by weight. In contrast, the treated waste rubbers will be batched by volume. Four partial replacement of course aggregates (0%, 15%, 30%, and 45%) will be considered in this case. A forced type of concrete mixer will be adopted with the goal of preparing the different concrete mixture.
Concrete cubes (150 x 150 x 150 mm) will be prepared using the standards molds. In each case, (0, 15, 30, and 45 substitutions) 6 cubes will be prepared and cured for 28 days. It is important to note that 7-day compressive strength will also be obtained by crushing 3 cubes in each case. After complete compressive strength is achieved (28 days), the water absorption test will be conducted, followed by the comprehensive strength test. The results obtained will shed more light on the effectiveness of partial replacement of course aggregates with treated tire wastes.
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Hypothesis
It is hypothesized that 15 percent partial replacement of course aggregates with treated waste tyres will give a comprehensive strength of above 20 N/mm2 per square millimetre after 28 days of curing. If this hypothesis will be proved, it will be plausible to affirm that treated waste tyres can be used as a partial substitute for coarse aggregates.
Abstract
This technology report aimed at determining the viability of using treated waste tyres as partial substitute of course aggregates in the production of concrete. It adopted the form of experimental study where two tests were undertaken. The tests included the water absorption and comprehensive strength of concrete. Notably, the water absorption test was undertaken with the goal of determining the durability characteristics of concrete produced using course aggregates as partial substitutes for course aggregates. From the laboratory test, it was found that the comprehensive strength of concrete is inversely proportional to the volume of rubber in the mix. Also, it was evident that the presence of rubber in a concrete mix design had limited effects on its water absorption characteristics. Based on findings, this report recommended that treated waste rubber should not exceed 15 percent of the volume of course aggregates in the production of structural concrete. The report also recommended that future studies should be carried out to determine the effects of using varying rubber particle sizes as partial substitutes of course aggregates in concrete production.
Table of Content
Methods of Data Collection. 11
Preparation of Concrete in the Laboratory. 12
Preparing The Test Specimens. 14
INTRODUCTION
This technology report aimed at determining the viability of using treated waste tyres as partial substitute of course aggregates in the production of concrete. On this account it is plausible to affirm that the report is within the building/architecture discipline. Over the past decade, the building industry has undergone numerous changes owing to technological advances. Notably, the majority of the changes have affected structural design and the choice of the building materials. For instance, major trends have been witnessed in the move to adopt eco-friendly building materials. Besides, the majority of companies in the construction industry have adopted the pre-cast building technology, which entails the preparation of structural elements, such as beams offsite and then assembling them onsite. In addition to the changes observed in the selection of building material, various interventions have been adopted with the goal of minimizing the use of non-renewable energy in buildings. As such, a major boom has been witnessed in the use of solar energy as an alternative to the conventional approaches to powering buildings.
Based on the numerous changes observed in the construction sector, it is plausible to argue that the industry is shifting from the conventional approaches to more modern and efficient building interventions. With the rising concern about the issue of global warming and climate change, there is the growing need to adopt building materials, which have limited footprints to the environment. The specific elements of the environment in this case include water, air, land, and energy. On this account, it is plausible to affirm that the construction industry is shifting towards the adoption of building materials, which has limited to no adverse effects on water, land, air, and energy. In the wake of climate change, the emission of greenhouse gasses to the atmosphere is the major concern as far as safeguarding the environment is concerned. On this account, it is reasonable to argue that the entire process of production and use of modern building materials should have limited to zero emission of greenhouse gases, such as nitrogen oxide.
Scope of the Report
As previously mentioned, this report aimed at determining the viability of using treated waste tyres as partial substitutes for course aggregates in the production of concrete. Some of the properties of concrete a famous building material include durability, high compressive strength, desirable fire resistance, impact resistance, low porosity, and high thermal insulation properties. Among these properties, comprehensive strength and durability are of great importance. On this account, this report focused only on comprehensive behaviour of the concrete produced using treated waste tyres as a partial substitute of course aggregates. This report aimed at achieving a comprehensive strength of 25 N/mm2 after 28 days of curing the concrete produced using the treated rubber. In addition, the report focused on the durability aspect of the concrete produced using the same intervention. It is important to note that the behaviour of reinforced concrete produced using treated rubber as a partial substitute for course aggregates is not considered in this report. Besides, the report does not consider the effects of the curing environment on the resulting comprehensive strength of the concrete. Lastly, the only concrete additive element which was used in the study was meant to strengthening the rubber-cement bond.
Problem Statement
The conventional concrete is produced using three main ingredients namely water, aggregates (both course and fine) and cement. The aggregates are usually obtains from quarries through process such as blasting and crushing. Notably, the quarrying process have adverse effects on the atmosphere since besides polluting the air, it is also considered a form of sound pollution. Aslani, Ma, Wan, and Muselin (2018) assert that dust is the most extensive and pronounced form of air pollution from quarries. Notably, when this dust finds its way to the atmosphere, it results in the formation of dust clouds, which have adverse effects on global weather patterns. Thomas and Gupta (2016) affirm that aerosol particles and dust clouds block terrestrial radiation from the earth resulting in warming of the earth surface. Indeed, global warming is an issue of concern for everyone; and therefore, the need to reduce dust related form of air pollution cannot be underestimated.
Besides polluting the environment, dust has also pronounced effects on human health. For instance, there is a growing concern about the rising incidences of valley fever, which are closely linked with the dust storms in the United States. Statistics indicate that in the recent years, cases of valley fever in the Southwestern United States have increased significantly due to solar ranches being put up in the region (Yung,Yung, & Hua, 2013). A). To set up the ranches, the vegetation is removed resulting in the loosening of the soil practices; and therefore, making them prone to wind erosion. Various studies have also indicated that there is positive correlation between asthma and dust.
Quarrying can also result in land degradation and the loss of biodiversity. The first process during the opening of a new quarry sites usually involves the clearing of the vegetation. Shu and Huang (2014) argue that the uprooting of vegetation is one of the risk factors for biodiversity since besides facilitating the extinction of certain types of plants, it destroys natural habitants of some animals. According to Thomas and Gupta (2016), quarrying results in the loss of land’s aesthetic value owing to the unproductive pits, which are usually left after the mining activities are terminated. Also, the pits may hold stagnant water, which acts a bleeding ground for various disease causing organisms.
Justification
Course aggregates used in the production of convectional concrete are obtained from quarries. As previously noted, the entire quarrying process has adverse effects on the environment and the general health of human beings. On this account, it is plausible to affirm that minimizing the use of course aggregates in the production of concrete will go a long way in reducing the quarrying activities. Consequently, it will be possible to minimize environmental pollution and land degradation attributed to the entire process of obtaining course aggregates. According to Yung,Yung, & Hua (2013), the global demand for concrete in 2009 was approximately 25 million tonnes per day. Eight years later, the demand has increased dramatically to reach an all-time high of approximately 435 billion tonnes per day. With increased regional and economic growth, the construction industry is growing gradually; and therefore, the demand for concrete will increase.
The insatiable demand for concrete will result in the opening of more quarry sites. This move will further worsen the environmental effects linked with stone extraction and crushing. With the goal of safeguarding the environment against possible threats, such as quarrying, there is an urgent need to shit from the conventional approaches to concrete production. Thomas and Gupta (2016) argue that the current intervention to concrete production is not sustainable since it relies on non-renewable ingredients, such as aggregates and cement. As such, there is the need to come up with modern approaches to concrete production with the ultimate goal of nurturing sustainability and safeguarding the environment.
With the growing use of road transport, waste tyres are proving to be a major menace to the environment. Thomas and Gupta (2016) assert that these tyres are not biodegradable and when they are disposed, “black pollution” occurs. Various proposals have been brought forward with the objective of reducing the number of waste tyres on the environment. Notably, waste tyres are currently being used as fuel for cement kilns and as fills in lightweight asphalt pavement. According to Shu and Huang (2014), the tyres are also used as artificial reefs in the marine ecosystems and as the primary material in the production of carbon black. It is important to note that some of these uses have proved to be both environmentally and economically unviable. Although various studies have been done in a bid to determine the effectiveness of waste tyres as partial substitute of course aggregates in the production of concrete, there has been little focus on the how the tyres can be treated with additives to improve the rubber-cement bond.
Partially substituting course aggregates with treated tyre wastes can be a both economically and environmentally viable option to the reuse of waste tyres. Notably, the move with go a long way in reducing the number of waste tyres on the environment. In some regions, such as India, waste tyres are used as a cheap source of energy (Shu & Huang, 2014). This application of the product not only pollutes the environment but it also goes a long way in affecting people’s health. Kotresh and Belachew (2014) argue that although waste tyres can serve as an efficient and cheap source of energy, the impacts of burning these products exceeds the benefits. Some of the by-products of burning waste tyres include sulfur oxides, carbon monoxide, and oxides of nitrogen (Guo et al, 2014). Notably, the majority of these by-products are greenhouse gases, which are responsible for global warming. Shu and Huang (2014) argue that exposure to these gases have both long term and short term health effects, such as irritation of the skin, cancer, and depression of the central nervous system.
METHODOLOGY
This section provides a deeper insight into the methods, which were adopted with the goal of determining the viability of treated tyre wastes when used as a partial substitute for course aggregates in the production of concrete. Besides, it sheds more light into the approaches, which were adopted in analysing the collected data. The reliability and validity of the research tools is also discussed in details.
Methods of Data Collection
Scientific tests were the major approaches adopted with the goal of achieving the objective of the report. Two tests main tests namely the cube crushing test and the water absorption test were conducted. While the water absorption test was meant to give an insight into the durability of concrete prepared used the treated waste tyres as aggregates, the cubic crushing test was meant to shed more light into the comprehensive strength of the concrete. Notably, the cube crushing test was conducted after 7 days of curing and after 28 days when it was assumed that the concrete had attained maximum strength.
Preparation of Concrete in the Laboratory
The first step in preparing the test specimen entailed gathering all the ingredients of concrete. The materials included fine aggregates, course aggregates, water, cement, and treated rubber particles. Since tap water is assumed to be free from various forms of contamination in the laboratory, it was adopted as the best option to hydrating the cement in the mixture. Regarding the choice of cement, Ordinary Portland Cement (OPC), was adopted in accordance with BS EN 197-1. In this regard, the concrete mix design process considered the fact that OPC contains 30 percent of pulverised fly ash and has a characteristic strength of 42.5 MPa (Kotresh & Belachew, 2014).
The coarse aggregate used in preparing the specimen were obtained from the laboratory. These aggregates were in the form of crushed gravels with a maximum nominal size of ten millimetres. Since it was paramount to get an insight regarding the water absorption rate of the course aggregates, the crushed gravels were immersed in water for a period of 24 hours. The aggregates were then wiped with a wet cloth with the goal of removing any excess water on the surface. Notably, the objective of immersing the aggregates in water was to determine their water absorption rate under surface-dried condition (SSD). The weight of the saturated aggregates was determined and recorded as M1. Subsequently, the aggregates were over dried over a period of 24 hours at a temperature of 105 Degree Celsius. They were then weighed and their weight recorded as M2.
The following formulae was adopting in calculating the water absorption rate of the aggregates.
The water displacement method was then adopted with the goal of measuring the volume of the sample aggregates under SSD condition. The findings of this test was recorded as V1. With the goal of calculating the density of the gravels at the SSD condition, the following formulae was adopted:
Fine Aggregates
Fine aggregates adopted for this report comprised of natural rive sand. The maximum particle size of these aggregates was 5mm. It is important to note that the water absorption rate and the density of the aggregates ate the SSD condition was determined using the same approach adopted in the case of the course aggregates. Besides, a sieve analysis was conducted with the objective of determining the distribution of the particles in accordance with BS EN 933-1. The sand used presented a continuous grading curve.
Waste Tyres (Rubber)
The rubber adopted for this report was sourced from a local garage. They were then cut into 12 mm pieces and treated with additives meant to enhance the rubber-cement bond. These aggregates were used to partially substitute the course aggregates. The density and water absorption rate of these rubber particles was also determined using the same procedure employed under the section of the fine aggregates.
Concrete Mix Design
The objective of conducting a mix design was to achieve a minimum comprehensive strength of 25 25 N/mm2 after 28 days of curing. Notably, the design was done using concrete mix design curves as documented in (Kotresh & Belachew, 2014). Notably, this intervention to concrete design is anchored on the need to achieve the optimal material proportions. Based on the desired compressive strength, the types of aggregates, desirable water to cement ratio, and the cement strength was determined. Notably, the desired slump height (150 mm), the type of the aggregates, and their nominal size informed the amount of free water used in the mix.
Four partial replacement of course aggregates (0%, 15%, 30%, and 45%) were considered in the mix design. As such, four concrete mixes were produced with the goal of gaining a deeper insight into the viability of partially replacing course aggregates using treated waste tyres. All others parameters of the mix design were kept constant expect the proportion of the course aggregates in the mix.
Preparing The Test Specimens
After measuring the desired portions of the concrete ingredients, mixing was conducted under the SSD condition. A powered mechanical mixer was used to produce a consistent mix, which was the cast into moulds measuring 150 x 150 x 150 mm. Immediately after casting, polythene sheets were using for curing purposes for a period of 24 hours after which the samples were immersed in a tank of water for optimum curing. After 7 days of curing, 12 cubes were crushed with the intent of getting a 7-day comprehensive test. After 27 days, the entire specimens were removed from the tank and subjected to the water absorption and cube crushing tests. These two tests were conducted in accordance with BS EN 12390-3 (comprehensive strength) and BS 1881-208 (water permeability).
RESULTS
Table 1. Average Water Absorption Rate and Density of the Aggregates at SSD Conditions
| Parameter | Fine Aggregates | Course Aggregates (Crushed Gravel) | Treated Waste Rubber |
| Density (kg/m3) | 2346 | 2593 | 1033 |
| Water Absorption (%) | 1.29 | 1.24 | 6.68 |
Table 2. Proportions Obtained From the Concrete Mix Design
| Samples | Volume of Cement | Volume of Crushed Gravel (Course Aggregates) | Volume of Water | Volume of Sand | Volume of Rubber (Course Aggregates) |
| 0 Percent Substitution | 534 | 1025 | 238 | 612 | 0 |
| 15 Percent Substitution | 528 | 872 | 221 | 589 | 153 |
| 30 Percent Substitution | 578 | 702 | 228 | 573 | 308 |
| 45 Percent Substitution | 589 | 600 | 218 | 589 | 461 |
Table 3: Average Comprehensive Strength Results
| Samples | 7 Day Strength (N/mm2) | 28 Days Strength (N/mm2) |
| 0 Percent Substitution | 17.50 | 27.60 |
| 15 Percent Substitution | 17.00 | 26.50 |
| 30 Percent Substitution | 14.20 | 22.50 |
| 45 Percent Substitution | 12.00 | 18.50 |
Table 4. Permeability Test Results
| Samples | Water permeability index |
| 0 Percent Substitution | 1.45 |
| 15 Percent Substitution | 1.75 |
| 30 Percent Substitution | 1.95 |
| 45 Percent Substitution | 2.45 |
Discussion Of Findings
The scope of this report was limited to determining the comprehensive strength of concrete prepared using treated waste tyres as a partial substitute to the conventional course aggregates. Besides, the investigation aimed at shedding more light on the durability of concrete prepared using the same kind of aggregates as a partial replacement to the crushed stone types of aggregates. Two tests were undertaken to achieve the objectives of the report. Prior to undertaking the experimental investigation, the aggregates were subjected to various test, such as the water absorption rate and density at SSD conditions. From Table 1, it is evident that the treated tyres wastes have a low density when compared to the conventional types of aggregates. This phenomenon can be explained by the fact that the mass of waste is low relative to its volume. Since density is a product of mass and volume, the observed results can said to be reliable.
The comprehensive strength characteristic of concrete makes it the most used building material. It was anticipated that partially replacing the course aggregates with treated tyres waste would lower the compressive strength of the concrete. This anticipation was in deeded confirmed by the results in Table 3. It is evident that the control experiment (samples with zero % rubber) have a higher comprehensive strength when compared to the other samples prepared using treated rubber as a partial substitute for the course aggregates. Notably, as the volume of the rubber increases in the concrete, the comprehensive strength is reducing. On this account, it is plausible to affirm that the comprehensive strength of concrete is inversely proportional to the volume of rubber in the mix. This observation can be explained by the fact that rubber particles have low stiffness value and poor surface texture when compared to rubber (Guo, Zhang, Chen, & Xie, 2014). Notably, these two characteristics have adverse effects on the bonding between rubber particles and cement. Besides, they have a joint negative effects on the consistency of the concrete mix. An investigation undertaken by Kotresh and Belachew (2014) with the goal of determining the viability of using rubber particles with a nominal particle size of 3 mm as a partial substitute of fine aggregates also found that the comprehensive strength of concrete was inversely proportional to the volume of aggregates in the mix.
CONCLUSION
In this report, the durability and compressive strength of concrete prepared using treated waste tyres was investigated. From the results section of the report, the main conclusion of this experimental investigation can be stated that rubber affects the water absorption rate and the compressive strength of concrete adversely. However, replacing only 15 percent of the course aggregates with rubber had minimal effects on these two material characteristics of concrete. On this account, it is plausible to affirm that effective concrete mix design should be carried out when using rubber wastes in the production of structural concrete. The findings of this report can be beneficial to the construction industry and to the environment at large. First, utilizing the tyres in construction is both economically and environmentally viable. As far as safeguarding the environment is concerned, the use of tyres in the building sector will result in the reduced black pollution. Also, the current use of waste tyres as an alternative source of energy will reduce.
RECOMMENDATIONS
Based on the findings of this report, various recommendation for general practice and future studies can be brought forward. This report found that substituting course aggregates with only 15 percent of treated waste rubber have limited effect on the durability and compressive strength of concrete. On this account, it can be recommend that in the production of concrete, the amount of rubber used as a replacement for course aggregates should not exceed 15 percent. However, for non-structural use of concrete, the percent of rubber in concrete can be increased up to 30 percent. This study was purely based on the on partial replacement of course aggregates with treated waste tyres of a nominal particle size of 12 mm. On this account, the report did not investigate the effects of the rubber particles on the comprehensive strength and durability of concrete. Although it is anticipated that that increasing the size of the rubber particles will result in a lowered comprehensive strength due to the high number of voids, which are likely to be created, the effect of using rubber particles of varying sizes is not clear. For this reason, future studies should focus on shedding more light on how the characteristics of concrete are affected by the nominal size of the rubber particles. Also, considerable research should be done to devise mechanisms of improving the rubber-cement bond.
References
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