The Effects Of Silt And Clay In The Properties Of Concrete

ABATRACT

Concrete is a versatile and most prevalent construction material. Its long-term performance depends on its interactions with the surrounding environment. The standards limit the ratio of the clay in aggregates due to its harmful effect on the concrete properties. This research paper presents the effect of different levels of clay and silt addition on the concrete properties. Various levels of clay and silt addition for different mixes were used in this experimental study. Their effect is based on workability, compressive strengths permeability and acid attack of concrete mixes was investigated. It has been seen that workability decreased by increasing the clay content to the mix. A drop in compressive strength of concrete up to 12% was observed by adding clay as compared with that of control samples. An adverse effect on resistance to permeability and acid attack of concrete was noted by increasing the clay content. From the results from the silt mix, it was observed that sand with silt content 4.65% compressive strength, split tensile strength, and flexural strength is increased as days of curing increased.

Keywords: properties of concrete, Compressive strength, clay, silt, Water permeability.

CHAPTER ONE

1.0                                          INTRODUCTION

1.1                            BACKGROUND OF THE STUDY

Concrete is a building material, which is most commonly used for construction. Failures in concrete can also be due to the use of improper aggregates. Aggregates cover about 65-80% of the volume of concrete. Aggregates should be characterized so that one could easily ascertain their role on the performance of concrete (Munoz et al. 2005, Neville 2000). Adverse effect on properties of concrete was observed with the presence of some types of micro fines on the faces of aggregates. Clay and silt mineral were found as a major portion of micro fine gravel coatings.

Clay is a type of fine-grained natural soil material containing clay minerals. Clays develop plasticity when wet, due to a molecular film of water surrounding the clay particles, but become hard, brittle and non–plastic upon drying or firing.

Silt consists of small particles or grains of soil and minerals that are easily carried and deposited by water. Each particle is smaller than a grain of sand but larger than a clay particle. When heavy rains pound the soil some of these fine granular particles are carried by the runoff water as silt. Silt carried by water runoff is deposited in lowlands, rivers or ponds as sediment. The environmental impact of silt is enormous, as once it settles into a river or lowland it provides valuable nutrients for plants and insects in the sediment it creates.

Silt carried down the Nile River, for example, created an oasis of rich, fertile soil for the ancient Egyptians. Silt carried down to the rivers can also provide a rich habitat for plants and fish. But silt can also be a source of problems by clogging pipes and drains. When too much silt is dumped into waterways or rivers, it can become a pollutant known as siltation. This can cause a number of environmental problems, including killing fish by clogging their gills, and by reducing the water’s dissolved oxygen level.

The overall objective of this study is to conclude how the existence of clay particles affects the compressive strength and other durability properties of concrete.

1.2                                                                              PROBLEM STATEMENT

Previous studies indicate that silt fine and clay content has an effect on concrete’s durability, especially when silt fine content in concrete is more than 5% (Murray, 2012). The presence of clay minerals in coarse and fine aggregates can have remarkable effects on the workability of fresh concrete, effectiveness of chemical admixtures, and on the mechanical strength, dimensional stability and durability of hardened concrete. It has been widely reported that the compressive strength reduces and shrinkage increases in concrete due to presence of clays in aggregates. The effect of silts and clays on various properties of concrete is not yet clear. This study was carried out to create a clear understanding of the effect of silt and clay in the properties of concrete.

1.3                      AIM AND OBJECTIVES OF THE STUDY

The main aim of this study is to investigate the effects of silt and clay in the properties of concrete. The objectives are:

1. To investigate effect of clay addition on workability, compressive strengths permeability and acid attack of concrete.
2. To determine the compressive strength, split tensile strength, flexural strength on different shaped samples of silt with concrete.

1.4                         SIGNIFICANCE OF THE STUDY

This study will serve as a means of having a wider knowledge about silt and clay, and their properties.

The study will be helpful in reducing troubles and suffering caused by the different stakeholders of construction industries.

1.5                    SCOPE AND LIMITATION OF WORK

This study concentrated on investigation of  how silt and clay affects the properties of concrete. During the investigation of the silt, different quantities of silt content present in fine aggregates were sampled using 3 days, 7 days, & 28 days compressive strength of concrete is checked and tested. For the clay, Various levels of clay addition for different mixes were used in this experimental study. The effect of clay addition on workability, compressive strengths permeability and acid attack of concrete mixes was investigated.

1.6                                 RESEARCH QUESTION

1. How does clay affect concrete?
2. What is the effect of silt?

• What will happen to the strength of the concrete if impurities such as clay and silt occur in the sand?

1. What are the factors that affect the properties of concrete?