Development Of High Strength Concrete From Recycled Aggregate Concrete
The development of high-strength concrete from recycled aggregate concrete involves innovative techniques to enhance the structural integrity and sustainability of construction materials. Recycled aggregate concrete, derived from crushed concrete waste, presents a promising solution for reducing environmental impact and conserving natural resources in the construction industry. By employing advanced processing methods and incorporating supplementary cementitious materials such as fly ash or silica fume, engineers can optimize the compressive strength and durability of recycled aggregate concrete. Furthermore, precise mix design adjustments and chemical admixtures help mitigate potential drawbacks associated with using recycled aggregates, ensuring consistent quality and performance of the resulting high-strength concrete. This process underscores a paradigm shift towards eco-friendly construction practices, balancing strength requirements with environmental stewardship and resource efficiency.
The aim for this project was to determine the strength and durability characteristics of high strength
structural concrete by using recycled coarse aggregates, which will give a better understanding on the
properties of concrete with recycled aggregates. To develop a mix design method to achieve high
strength of 80N/mm2
using RCA, To evaluate the compressive strength at different replacement level of
cement with metakaolin, To determine the optimum replacement of RCA with natural aggregate. The
scope of this project was to investigate the possibility of using low cost recycled coarse aggregates as
an alternative material to coarse aggregate in high strength structural concrete. The experimental
investigation were carried out using detailed strength and durability related tests such as compressive
strength test of cubes, split tensile strength test of cylinders, test for saturated water absorption and
porosity. The tests were conducted by replacing the coarse aggregates in high strength concrete mixes
by 0, 10, 20, 30, and 40 of recycled coarse aggregates. I was able to obtain a high strength of 82N/mm2
at 0% RCA, 78N/mm2 at 10% RCA, 70N/mm2 at 20% RCA, 67N/mm2 at 30% RCA and 60N/mm2 at
40% RCA. A 40% replaced mix with reduced w/c ratio was also tested. From the experimental
investigation it was found that recycled coarse aggregates can be used for making high strength
concretes by adjusting the w/c ratio and admixture contents of the mix
ABSTRACT
DECLARATION
CERTIFICATION
DEDICATION
ACKNOWLEDGEMENT
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
LIST OF PLATES
ACRONYMS viii
CHAPTER 1:
INTRODUCTION Pages
1.1 Background of Study 1
1.2 Justification of problem 5
1.3 Statement of problem 6
1.4 Project Aim/Objectives 6
1.5 Methodology 7
1.6 Scope of the work 7
1.7 Delimitation of the work 8
1.8 Significance of Study 8
1.9 Layout of Project 8
CHAPTER 2:
LITERATURE REVIEW
2.1.1 General 10
2.1.2 Constituent Materials in Concrete 11
2.1.3 Concrete Waste and Concrete Recycling 11
2.1.4 Properties Of Recycled Aggregate 13
2.1.4.1 Physical 13
2.1.4.1.1 Adhered paste and mortar 13
2.1.4.1.2 Bulk density 14
2.1.4.1.3 Specific gravity 16
2.1.4.1.4. Water absorption 16
2.1.4.2 Mechanical 18
2.1.4.2.1. Abrasion 18
2.1.4.3. Durability properties 18
2.1.4.3.1. Sulphate soundness 18
2.1.5 Recommendations 19
2.1.6 Mix design 21
2.1.7 Properties of Recycled Aggregate Concrete 22
2.1.7.1 Properties of fresh concrete 22
2.1.7.1.1 Water demand and workability 23
2.1.7.1.2 W/C Ratio 25
2.1.7.1.3 Cement quantity 25
2.1.7.1.4 Density and air content 25
2.1.7.1.5 New interfacial transition zone 26
2.1.8 Mechanical Properties of Recycled Aggregate Concrete 29
2.1.8.1 Compression 29
2.1.8.1.1. Behavior of recycled aggregate concrete produced with natural coarse
aggregate and recycled fine aggregate. 29
2.1.8.1.2. Behaviour of recycled aggregate concrete produced with recycled
coarse aggregate and recycled fine aggregate 30
2.1.8.1.3. Behaviour of recycled aggregate concrete produced with
recycled coarse aggregate and natural sand 30
2.1.8.2 Behavior of recycled aggregate concrete in tension 38
2.1.8.3. Behavior of recycled aggregate concrete in flexure 39
2.1.8.4 Stress strain behavior of recycled aggregate concrete 40
2.1.8.5 Young‟s modulus 42
2.1.10 Sound Absorption Characteristics 43
2.1.11 Durability Properties 44
2.1.11.1 Permeability and water absorption 45
2.1.11.2 Freezing and thawing resistance 47
2.1.11.3 Chloride diffusion/Penetration 49
2.1.11.5 Water Sorptivity 51
2.1.11.6 Reinforcement corrosion 52
2.1.11.7 Creep, elastic shrinkage and drying shrinkage 53
2.1.12 Economic Comparison Concrete Recycling 54
2.1.13 Structural Properties 56
2.1.13.1 Flexural behaviour of recycled aggregate concrete 56
2.1.13.2 Shear behaviour of recycled aggregate concrete 57
2.1.13.3 Compression behaviour of recycled aggregate concrete 58
2.1.13.4 Bond behavior of recycled aggregate concrete with steel rebar‟s 59
2.1.13.5 Seismic performance of recycled aggregate concrete 60
2.1.13.6 Glass fiber reinforced recycled aggregate concrete 60
CHAPTER 3:
MATERIALS AND METHODS
3.0 Materials 37
3.1 Material Classification 37
3.2 Classification of Aggregates 39
3.3 Mix Design 39
3.4 Experimental Procedures 40
3.5 Sieve Analysis 42
3.6 Apparatus and Test Procedure of Sieve Analysis 43
3.7 Indirect Tensile Strength Test 44
3.8 Apparatus and Test Procedure of Indirect Tensile Strength Test 45
3.9 Instrumentation and laboratory Testing 47
3.1.1 Indirect Tensile Test 49
3.1.2 Curing of Concrete Specimens 50
3.1.3 Calculation of mix Design 51
CHAPTER 4:
RESULT AND DISCUSSION
4.1 Introduction 52
4.2 Sieve Analysis Test 52
4.3 Slump Test Result and Analysis 57
4.4 Compression Strength Test Result and Analysis 58
4.5 Tensile Strength Test Result and Analysis 59
CHAPTER 5:
CONCLUSION AND RECOMMENDATION
5.1: Conclusion 62
5.2: Recommendations 63
REFERENCES
APPENDICES
INTRODUCTION
1.9 Background of Study
Recycling is the act of processing the used material for use in creating new product. The
usage of natural aggregate is getting more and more intense with the advanced development in
infrastructure area. In order to reduce the usage of natural aggregate, recycled aggregate can
be used as the replacement materials. Recycled aggregate are comprised of crushed, graded
inorganic particles processed from the materials that have been used in the constructions and
demolition debris. These materials are generally from Buildings, roads, bridges, and
sometimes even from catastrophes, such as wars and earthquakes. There are many advantages
through using the recycled aggregate such as Environmental Gain, Cost, Job Opportunities,
Sustainability, Market is wide and many more ( N.Sivakumar 2014).
Use of recycled aggregate in concrete can be useful for environmental protection. Recycled
aggregates are the materials for the future. The application of recycled aggregate has been
started in a large number of construction projects of many European, American, Russian and
Asian countries (Sonawane, Sunil and Pimplikar 2007).
Urbanization growth rate in India is very high due to industrialization. Growth rate of India is
reaching 9% of GDP. Rapid infrastructure development requires a large quantity of
construction materials, land requirements & the site. For large construction, concrete is
preferred as it has longer life, low maintenance cost & better performance. For achieving GDP
rate, smaller structures are demolished & new towers are constructed. Protection of
environment is a basic factor which is directly connected with the survival of the human race.
Parameters like environmental consciousness, protection of natural resources, sustainable
development, play an important role in modern requirements of construction works. Due to
modernization, demolished materials are dumped on land & not used for any purpose. Such
situations affect the fertility of land. As per report of Hindu online of March 2007, India
generates 23.75 million tons demolition waste annually. As per report of Central Pollution
Control Board (CPCB) Delhi, in India, 48million tons solid waste is produced out of which
14.5 million ton waste is produced from the construction waste sector, out of which only 3%
waste is used for embankment. (Magdum 2007)
It is not surprising that alternatives are being sought out. One solution that solves both
problems simultaneously is recycling of concrete waste. Through a process that usually
involves multistage crushing, eliminating impurities and sieving, a new aggregate produced
called recycled concrete aggregate (RCA). When this new aggregate is used to make concrete,
with complete or partial replacement of natural aggregate, this concrete is called recycled
aggregate concrete (RAC).
Recycled concrete aggregate and recycled aggregate concrete have been studied for several
decades. At the material level, practically all important characteristics of RCA and RAC have
been studied, from short-term and long-term mechanical properties to durability. The main
characteristic that distinguishes RCA from natural aggregate is the certain quantity of cement
paste that remains attached to the aggregates after crushing. This residual cement paste is the
reason for higher water absorption of RCA compared with natural aggregates, especially in
the case of fine RCA. (Tošic´, Marinkovic´ and Ignjatovic 2016).
Using recycled aggregates crushed from demolished concrete to produce new concrete can
reduce the consumption of natural sources and save the landfill spaces. This kind of
sustainable material is commonly referred to as recycled aggregate concrete (RAC). (Geng
and Wang 2016).
S. Muthukumar (2010), observed that concrete suitability and adaptability will change with
respect to the environment, the concrete must be such that it can conserve resources, protect
the environment, economize and lead to proper utilization of energy. To achieve this, major
emphasis must be laid on the use of wastes and byproducts in cement and concrete used for
new constructions. The utilization of recycled aggregate is particularly very promising as 75
per cent of concrete is made of aggregates. The use of recycled aggregates from construction
and demolition wastes is showing prospective application in construction as alternative to
primary (natural) aggregates. Research on the usage of waste construction materials is very
important since the materials waste is gradually increasing with the increase of population and
increasing of urban development. The reasons that many investigations and analysis had been
made on recycled aggregate are because recycled aggregate is easy to obtain and the cost is
cheaper than virgin aggregate.
The increasing and unsustainable consumption of natural resources, as well as the excessive
production of construction and demolition waste (CDW), has been a cause of great concern
for the environment and economy. In order to reverse this trend, there have been several
efforts to promote the ecological efficiency in the construction industry, one of them being the
reutilization of CDW in new construction. By doing so, besides decreasing the amount of
waste mass sent to landfills and the extraction of natural resources, more value will also be
added to these materials, thus opening new market opportunities (Coelho and Brito, 2013).
Research on this subject started with basic observations on the effects of using
recycled concrete aggregates (RCA) on the compressive strength of concrete (Buck, 1999;
Frondistou-Yannas, 1998), as well as its economic feasibility (Frondistou-Yannas and Itoh,
2000). Since then, research on recycled aggregate concrete (RAC) has become progressively
complex, introducing several new variables, in which the durability-related performance has
also been considered. These more recent studies have generally shown a decline of the
mechanical and durability-related performance, when compared to that of natural aggregate
concrete (NAC), with similar characteristics (mix design, curing conditions, strength class,
etc.
Very large quantities of construction and demolition wastes are generated yearly, only a small
fraction is recycled. Among these wastes, concrete is one of the most abundant. It can be
crushed in order to produce new aggregates, called Recycled Concrete Aggregates (RCA).
RCA are composed of two phases: Natural Aggregates (NA) used for the manufacture of the
original concrete and hardened cement paste adhering to the natural aggregates. Now, these
recycled aggregates are essentially used in backfills for the construction of new roads. But
they could also be used for the manufacture of new concretes. These new concretes can be
produced by replacing different fractions of natural aggregates by RCA. (Rui´Vasco, Brito
and Ravindra 2016).
Topcu et al. (2004) investigated that the recycling waste concrete aggregates in concrete
production raises the problem of workability. In particular, concrete with more than 50%
waste concrete aggregates experiences more workability problem.
Figure 1.1: Recycled Aggregate
1.10 Justification of problem
Traditionally, the application of recycled aggregate is used as landfill. Nowadays, the
applications of recycled aggregate in construction areas are wide. The applications are
different from country to country.
The main source of raw material for recycling of concrete waste comes from demolition of
concrete structures. The quality and purity of the raw material affect the quality of recycling
products and ultimately commercial acceptance of concrete recycling products, the process of
manufacturing concrete recycling products is relatively simple. BCSJ (2001).
Recycled aggregate can be used for construction of precast and cast in situ gutters and kerbs.
it also Cost saving: – There are no detrimental effects on concrete and it is expected that the
increase in the cost of cement could be offset by the lower cost of Recycled Concrete
Aggregate (RCA). ( Magdum 2007).
Porosity of RAC are responsible gaps for the lower strength compared to NAC.
1.11 Statement of problem
Although aggregate has been used extensively in civil engineering construction in recent
time. However significant deficiency in its applicability in low mechanical and durability
properties compared to normal (natural) aggregate concrete. There is need to carry an
optimal mix design that would reduce the porosity responsible for lower strength of RAC
Incorporation of other cementations materials such as metakaolin or microsilica would
reduce the void or porosity.
1.12 Project Aim/Objectives
The aim of this study is to develop high strength concrete made with recycled aggregate
using the rational mix design method.
This would be achieve using the following objectives
To develop a mix design method to achieve high strength of 80N/mm2
using RCA.
To evaluate the compressive strength at different replacement level of cement with
metakaolin.
To determine the optimum replacement of RCA with natural aggregate.
To measure the tensile strength at different replacement level.
1.13 Methodology
Experimental method is used due to its versatility.
To establish a comparative basis control specimen of concrete made with natural
aggregate (granite) were prepared with RAC recycled aggregate concrete.
In order to obtain the optimum replacement level natural aggregate is replaced with RCA
in the following percentage 10%, 20%, 30% and 40%. To reduce the porosity or voids in
RAC , metakaolin was used to replace Portland cement by 5%, 10%, 15%.
36 cubes and cylinder specimens are made for compressive strength test and Tensile
strength equivalent samples are also made for the control specimen.
The specimens are tested subject to the variables of testing ages of 7, 14 and 28days
respectively.
1.6 Scope of the work
The scope of this project was to investigate the possibility of using low cost recycled coarse
aggregates as an alternative material to coarse aggregate in high strength structural concrete.
The study covers 7, 14 and 28 days casting and curing of cubes 100 x 100 x 100 dimension,
comprising of 36 concrete cubes and cylinder in different mixes, were made for compressive
strength test and tensile strength test involving recycled aggregate and natural aggregate. The
physical and mechanical properties, water absorption, compressive strength and tensile
strength are measured at various ages.
1.7 Delimitation of the work
This work is limited to the physical and mechanical properties, water absorption,
compression and durability aspects such as exposure of RAC to aggressive agents are not
considered.
1.8 Significance of Study
This study provides a design guideline on the application of recycled aggregate in the
production of high strength. The application of RA in construction could be achieve twofold
advantage.
Reduction of environmental hazards
Cheaper and economic advantages.
1.9 Layout of Project
This paper is organized into five (5) chapters followed by bibliography, references and
appendices. Each of the chapter is further divided into sections and subsections for clarity of
purpose and presentation. Brief overview of the contents of each chapter are as follows;
• Chapter 1 presents the introduction to the work with highlights on the background of study,
justification of problem, statement of problem, aims and objectives of the study, methodology,
scope of the work, delimitation of the work, significance of the study and layout of project.
• Chapter 2 provides a review of relevant literature, overview of recycling process, as well as
comparison of recycled aggregate and natural aggregate. This chapter also discussed the
previous investigation and testing done with recycled aggregate.
• Chapter 3 includes the preliminary design and information on the recycled aggregate testing,
sieve analysis and design of the concrete mix.
• Chapter 4 discusses the results and analysis of all experimental results obtained from the
testing procedures.
• Chapter 5 contains the conclusions of the research and recommendations on further work.
SHARE PROJECT MATERIALS ON:
Development Of High Strength Concrete From Recycled Aggregate Concrete:
Developing high-strength concrete from recycled aggregate concrete (RAC) involves several key considerations and steps. High-strength concrete typically refers to concrete with compressive strengths greater than 40 MPa (mega-pascals). Here’s an overview of the process:
- Understanding Recycled Aggregate Concrete (RAC): RAC is concrete made by replacing a portion of natural aggregates (such as crushed stone or sand) with recycled aggregates. Recycled aggregates can come from demolished concrete structures, industrial by-products, or other sources. The quality of the recycled aggregates significantly affects the properties of RAC.
- Quality Control of Recycled Aggregates: To ensure the quality of RAC, it’s essential to carefully select and process the recycled aggregates. This may involve removing contaminants, grading the aggregates, and ensuring they meet specified standards for size, shape, and cleanliness.
- Mix Design: High-strength concrete mix design for RAC involves selecting appropriate proportions of cement, water, and admixtures while optimizing the ratio of recycled aggregates to natural aggregates. The mix design process should account for the quality of recycled aggregates and desired compressive strength.
- Cementitious Materials: The use of supplementary cementitious materials (SCMs) like fly ash, silica fume, or slag can enhance the properties of RAC. SCMs improve the workability, durability, and compressive strength of concrete while reducing the environmental impact.
- Water-Cement Ratio (W/C Ratio): Maintaining a low water-cement ratio is crucial for achieving high-strength concrete. A lower W/C ratio typically leads to higher strength, but it should be balanced to ensure workability and durability.
- Admixtures: Chemical admixtures, such as superplasticizers or viscosity-modifying agents, can be used to improve the workability and flowability of RAC without increasing the water content.
- Testing and Quality Assurance: Rigorous testing is essential throughout the development process to ensure the desired strength and durability of the RAC. Common tests include compressive strength tests, flexural strength tests, and durability tests like freeze-thaw resistance and chloride permeability tests.
- Curing and Ageing: Proper curing of RAC is crucial to achieve high strength. Curing conditions and duration should be carefully controlled to allow the concrete to gain strength over time.
- Construction Practices: High-strength RAC may require special construction practices, such as quality control during mixing, transportation, and placement. It’s important to follow best practices to minimize the risk of defects.
- Quality Control and Monitoring: Implement a quality control and monitoring program to ensure that the RAC meets the specified strength and durability requirements.
- Environmental Considerations: Using recycled aggregates in concrete can have environmental benefits by reducing the demand for virgin aggregates and reducing waste. However, it’s important to consider the environmental impact of the entire concrete production process.
- Documentation: Maintain detailed records of the mix design, testing results, and construction practices to track the performance of high-strength RAC and make any necessary adjustments for future projects.
Developing high-strength concrete from recycled aggregate concrete can be a sustainable and cost-effective solution, but it requires careful planning, testing, and quality control to ensure that the desired properties are achieved. Collaboration with experts in concrete technology and materials engineering is often beneficial in these endeavors.