An Investigation Into Quality Of Aggregate In Road Construction
The current extensive use of low quality aggregate in Nigerian road for engineering applications is of concern because their 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 deposits in Isi-Agu Abia State and mac-Daniels Abakiliki. One sample each were obtained from different location mentioned above and transported to ministry of works laboratory Enugu, Enugu State.
These two aggregate samples were tested for sieve analysis test, relative density test, water absorption test, ten percent fine test, aggregate crushing value test (ACV), Aggregate impact value test (AIV), and Abrasion value test. Findings revealed that the best aggregate for road construction is the aggregate from Isi-Agu. 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 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
- To identify the key factors affecting the strength of aggregate structure which are aggregate shape, angularity and texture?
- To ensure that the specifications for aggregates angularity are included in the super pave mixture design system.
- 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.
- To determine the aggregate abrasion resistance and breakdown of particles and tests that address aggregate weathering when exposed to freezing and thawing.
- To determine the different properties of aggregates
- 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.
The quality of coarse aggregate has a significant effect on the compressive strength of high strength concrete. The compressive strength of steel slag aggregate concrete was more than that of crushed limestone aggregate concrete. The compressive strength of concrete prepared with calcareous limestone aggregate was the least. These data indicate that in a high strength concrete, i.e. concrete prepared using a low water– cement ratio and high cement content, the compressive strength is dependent on the quality of aggregate. In such concrete, the bulk of the compressive load is borne by the aggregate rather than the cement paste alone.
The failure in such concretes is often through the aggregates. Since the calcareous limestone is known to be weaker than the dolomitic and quartzitic limestone aggregates, its low load carrying capacity is understandable.
Split tensile strength increased with age in all the concrete specimens. The type of aggregate also influences the split tensile strength of concrete. The split tensile strength of steel slag aggregate concrete was more than that of limestone aggregate concrete. The least split tensile strength was noted in the calcareous limestone aggregate concretes. The quality of coarse aggregate also influences the modulus of elasticity of concrete. Weaker aggregates tend to produce a more ductile concrete than strong aggregates do, in the construction of roads.
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