ABSTRACT
The self-compacted concrete (SCC) is a special type of concrete which settles down in the formwork and fills its every corner without any use of compaction or vibration. As SCC has higher flow-ability that causes brittle behaviour resulting in poor performance under tension and bending. The inclusion of randomly distributed short and discrete fibers is one of the most effective way to improve the tensile as well as flexural performance of SCC. In this regard this experimental study is undertaken to investigate the effect of nylon fibers (NF) on fresh and hardened properties of SCC. Two different lengths; 20 mm and 12 mm and five different volumetric percentages; 0.1, 0.2, 0.3, 0.4 and 0.5% of NF were used. The results revealed that addition of NF slightly affects the fresh properties of SCC. However, the extent of the effect is not of that order to be considered as major factor. The fresh properties for entire mixes lie within the required range according to EFNARC guidelines. The strength properties increases with addition of NF, the extent of increment is greater for the longer length of NF. The optimum volumetric fraction of NF for producing high strength SCC was found as 0.5%.
Keywords: Self-Compacting Concrete; SCC; Nylon Fibers; NF; Fresh Properties; Filling ability; Passing ability; Hardened Properties; Compressive Strength; Spilt Tensile Strength.
CHAPTER ONE
INTRODUCTION
1.1 General Background
Concrete is a main construction material, it is a composite material that consists of cement water and aggregates (fine and coarse), aggregates are considered as the most important components in concrete volume. For example, in normal concretes about three-quarters of the volume is occupied by the aggregates. The most important functions of using both fine and coarse aggregates are to provide bulk to the concrete, to increase the density and volume stability, to contribute in workability and uniformity of concrete mixes.
Generally, it is considered that aggregates quality is important in concrete mixing. Not only because the aggregates limit the strength of concrete, but, with undesirable aggregate properties cannot produce a strong, durable and structural performance concrete. Both physical properties and mechanical behavior of aggregates greatly influence fresh and hardened properties and behavior of concrete (A. M. Neville, 2011).
On the other hand, nowadays recycling of waste materials poses a major problem for countries and municipalities worldwide. So, using or recycling these waste materials in construction industry at all and especially in concrete has attracted a lot of interest worldwide due to the increased disposal costs and environmental concerns (Senhadji et al., 2015; Kou et al., 2009; Haghighatnejad et al., 2016). Nylon fiber or nylon fiber is one of the most problematic waste materials. More than 20 million tons of nylon fiber is being produced per year all over the world (Brown et al., 2000). For years, the nylon fiber waste has been burned which caused the environmental pollution. But, today social awareness is finding the new methods of recycling nylon fiber wastes. Like, using nylon fiber as a replacement to either fine and/or coarse aggregates in concrete production will be beneficial behavior in environmental friendly concrete production (Yap et al., 2001).
1.2 Problem Statement
Nowadays, the world environment is facing to a very serious crisis because of waste materials and conventional ways of recycling or utilizing these waste materials. On the top of these materials is nylon fiber which has a great role in causing environmental pollution, also, until now there is not a very property way to reusing and/or recycling it. So by thinking towards using nylon fiber in construction industries may be a perfect way to recycling in a high amount and at the same time it can be a safe and economical way.
1.3 Significance of the Study
This research is focusing on finding out the best way to utilizing the waste nylon fiber in construction industries in order to release the environment from this material in a safe and economical way. It is important to find out the critical effects of nylon fiber as an aggregate substitution, on mechanical and physical properties and long term durability of SCC concrete.
1.4 Objectives of the Study
This thesis aims to investigate the effects of replacing a part of coarse aggregate with nylon fiber, on concrete performance. The objectives to be studied are:
· Effects of nylon fiber on fresh concrete properties.
· Influence of nylon fiber on concrete compressive, splitting tensile and flexural strengths,
· Effects of nylon fiber on flexural toughness,
· Ultra sound pulse velosity readings before and after loading the specimens,
· Long term durability-degradation tests againts heat,
· The optimum amount of nylon fiber waste plastic replaced to aggregates,
· Conclusions and recommendations for further research.
1.5 Organization of the Experimental Study
This thesis is organized into five chapters as follow:
Chapter one is introducing the thesis subject, significance and objectives, while chapter two is about theoretical background and literature review of the study. Chapter three is containing the material and experimental procedure and description. Analysis of experimental results and discussions can be found in chapter four and finally, conclusions and recommendations for further research can be found in chapter 5, which is the last.
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