AN INVESTIGATION INTO QUALITY OF AGGREGATE IN ROAD CONSTRUCTION

ABSTRACT

The current extensive use of low quality aggregate in Nigerian road for engineering applications is of concern because they appear to be a level of ignorance surrounding their existing properties and implications. This project was conceived for the purpose of comparing the crushed aggregate and one sample each was obtained from different locations and transported to ministry of works laboratory Enugu, Enugu State. These aggregate samples were tested. It also revealed that the standard strength for Abrasion is between 20 – 30 percent comparison were made between the results, precautions, procedures and observations. And this coarse aggregate should be tested and analyzed before using in any constructional purposes to ensure durability of engineering products. The highest and lowest compressive strength was obtained in the concrete specimens prepared with steel slag and calcareous limestone aggregates, respectively. Similarly, the split tensile strength of steel slag aggregate concrete was the highest, followed by that of dolomitic and quartzitic limestone aggregate concretes. The lowest split tensile strength was noted in the calcareous limestone aggregate concrete. The type of coarse aggregate also influences the modulus of elasticity of concrete. Weaker aggregates tend to produce a more ductile concrete than stronger aggregates do.

CHAPTER ONE

1.0     INTRODUCTION

The basic thing in investigation into the quality of aggregate in road construction is that aggregates serves as reinforcement to add strength to the overall composite material. Due to the relatively high hydraulic conductivity value as compared to most soils, aggregates are widely used in drainage application such as foundation and French drains, septic drain fields, retaining wall drains and road side edge drains. Also the quality of aggregates helps to prevent differential setting under the road that binds with more expensive asphalt. Furthermore, aggregates feature at all levels of road construction up to the surface which includes aggregates resistant to polishing, ensuring skid resistance. The quality plan or system should cover all quality aspect of source material handling aggregate processing, stockpiling and transportation including methods and frequency of sampling and testing to be used, and should also identify key responsibilities.

1.2     BACKGROUND OF THE STUDY

It involves the analysis of the quality of Aggregates used in road construction in respect to its strength, properties of aggregates and application of aggregates in construction field. Also it explained why Aggregates can be defined as Natural aggregates, manufactured aggregates and Recycled aggregates. It reveals the difference between primary aggregates and secondary aggregates during the study. This study examines the practical uses and laboratory testing of the aggregates using different methods and the problem arising during the research. Also recommendation for developing and implementing a quality plan or system are covered during the research.

1.3     AIM AND OBJECTIVES OF THIS STUDY

THE GENERAL AIM AND OBJECTIVES OF THIS STUDY IS AS FOLLOWS

1. To identify the key factors affecting the strength of aggregate structure which are aggregate shape, angularity and texture?
2. To ensure that the specifications for aggregates angularity are included in the super pave mixture design system.
3. To obtain a material sufficiently durable to last the design life of the road in order that its performance is not affected by deterioration or degradation of the material.
4. To determine the aggregate abrasion resistance and breakdown of particles and tests that address aggregate weathering when exposed to freezing and thawing.
5. To determine the different properties of aggregates
6. To examine the different quality plan or system to controlling the sources of aggregate

1.4 SCOPE OF THE STUDY

It covers the systems and procedures recommended by Roading New Zealand (RNZ) for the quality assurance of aggregates for roads. The guideline was developed by quality Association of New Zealand. It reveals that the aggregate producer should have a formal quality plan system in operation in each quarry detailing the quality control producers to be used for sourcing rock and for controlling quality of each of the aggregate produced. Also the quality plan or system should cover all quality aspects of source material handling aggregate processing, stock pilling and transportation, including methods and frequency of sampling of sampling and testing to be used.

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