Effects Of Aggregate Sizes On The Concrete Strength
The size distribution of aggregates significantly influences the mechanical properties of concrete, particularly its compressive strength. Varying aggregate sizes impact the concrete mixture’s workability, water demand, and overall cohesion. Larger aggregates tend to enhance concrete strength due to their ability to provide better interlocking and reduced void content, thereby improving the load-bearing capacity. Conversely, smaller aggregates increase the surface area available for bonding with cement paste, enhancing the overall density and potentially improving strength as well. However, an excessive proportion of either large or small aggregates can lead to issues such as poor workability, segregation, and decreased strength. Therefore, achieving an optimal balance in aggregate sizes is crucial for optimizing concrete strength and ensuring structural integrity in construction projects.
In the sense that the materials involved in this project were capital intensive more especially cement, so in carrying out the work one must hsve to be careful in the selection and collection of materials to be used in the casting of the concrete.
The materials used are coarse aggregate (granite) fine aggregate (sand). The coarse aggregates used in this work were collected from ishiagu while the fine aggregate was collected in front of the carpentry’s workshop on the campus.
The test conform to the standard method test, the ratio used was 1:2:4 and the method adopted was batching by weight, from the mix ratio the relative weight for each material to be used for concrete cube cast was 36, these cubes were tested for compressive strength of 7, 14 and 28 days.
The results of tests involved in the work and that of compressive strength tests were calculated and tabulated as shown in the final tabulation of results.
With the above information, I now recommend and therefore conclude.
Title page
Latter of transmittal
Approval page
Dedication
Acknowledgement
Abstract
Table of contents
CHAPTER ONE
1.1 The project objectives
CHAPTER TWO
2.1 Materials for concrete
2.2 Aggregates introduction
2.2.1 Fine Aggregate/Sand
2.2.2 Coarse Aggregate/Granite
CHAPTER THREE
3.0 Mixing of the concrete
CHAPTER FOUR
4.0 Preparation for placing and compaction
CHAPTER FIVE
5.0 Curing
CHAPTER SIX
6.0 Testing of hardened concrete and tabulation of results
CHAPTER SEVEN
7.0 Conclusions and recommendation
Bibliography.
THE PROJECT OBJECTIVES
The project has some aims of verification. One of the most important purposes of this project is to compare the strength of concrete made with granite of different sizes eg 20, 15, 10 and 5mm. These same types of concrete are made under the same mix proportion.
Another purpose also is to know the compressive strength of concrete at different ages.
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Effects Of Aggregate Sizes On The Concrete Strength:
The size of aggregates used in concrete can have a significant impact on the strength and performance of the concrete mixture. Here are the effects of aggregate sizes on concrete strength:
Workability: Smaller aggregates generally make the concrete mix more workable. Workability refers to how easily the concrete can be mixed, placed, and compacted. Finer aggregates require less water to achieve a given level of workability, which can be an advantage in some cases.
Water-Cement Ratio: The water-cement ratio is a critical factor in concrete strength. Using smaller aggregates can reduce the water demand for a given workability, which can result in a lower water-cement ratio. Lower water-cement ratios typically lead to higher concrete strength.
Strength: In general, concrete made with smaller aggregates tends to have higher compressive and tensile strength compared to concrete made with larger aggregates. This is because smaller aggregates provide better packing, resulting in a denser concrete matrix.
Durability: Smaller aggregates can enhance the durability of concrete. A denser concrete matrix with smaller aggregates can provide better resistance to freeze-thaw cycles, abrasion, and chemical attack, all of which can affect the long-term durability of the concrete.
Workability and Segregation: While smaller aggregates improve workability, they can also increase the risk of segregation if not properly managed during mixing and placing. Segregation is the separation of coarse and fine particles, which can lead to uneven distribution of aggregates and affect the uniformity of the concrete mixture.
Economy: The cost of aggregates can vary significantly based on size and availability. In some cases, using locally available aggregates of a certain size may be more cost-effective, but this should be balanced with the desired concrete properties.
Aggregate Grading: Properly grading aggregates is crucial. A well-graded aggregate mix, which includes a range of sizes from fine to coarse, can optimize packing and improve the overall performance of the concrete.
Porous Concrete: In some cases, larger aggregates may be intentionally used to create porous or lightweight concrete. This is often done for specific applications where reduced density and increased porosity are desired, such as in the construction of lightweight precast concrete blocks.
In summary, the choice of aggregate size in concrete mix design should be based on a combination of factors including the desired strength, workability, durability, and specific project requirements. It is essential to consider the local materials available and conduct appropriate tests to optimize the mix for the intended application while ensuring good workability and resistance to segregation.