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Journal ArticleDOI

A simplified approach for mix design based on shape factors of coarse aggregates

01 Dec 1984-Bulletin of the International Association of Engineering Geology (Springer Berlin Heidelberg)-Vol. 30, Iss: 1, pp 123-126
TL;DR: In this paper, the stability of granular materials and bituminous mixes increases with increase in dry density or decrease in voids in the mix and the proportions of materials are designed to obtain a desired gradation which yields maximum density.
Abstract: The stability of granular materials and bituminous mixes increases with increase in dry density or decrease in voids in the mix. Therefore the proportions of materials in the mix are designed to obtain a desired gradation which yields maximum density.
Citations
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Journal ArticleDOI
TL;DR: In this paper, the effects of grain shape and size on the mechanical behavior of compacted earthen materials were explored and the results showed that the mechanical behaviour of gravel-earth mixture may be influenced by grain shape of the gravel used, thus introducing a new parameter to be taken into account when preparing unstabilized rammed earth material.

6 citations

Journal ArticleDOI
TL;DR: In this paper, two types of coal mining subsidence are identified: the first is the generation of crown holes caused by the collapse of mine entries and mine roadway intersections and the consolidation of shallow voids, and the second is where longwall mining encourages the roof to fail to relieve the strains on the working face and this generates a subsidence trough.
Abstract: One of the geohazards associated with coal mining is subsidence. Coal was originally extracted where it outcropped, then mining became progressively deeper via shallow workings including bell pits, which later developed into room-and-pillar workings. By the middle of the 1900s, coal was mined in larger open pits and underground by longwall mining methods. The mining of coal can often result in the subsidence of the ground surface. Generally, there are two main types of subsidence associated with coal mining. The first is the generation of crown holes caused by the collapse of mine entries and mine roadway intersections and the consolidation of shallow voids. The second is where longwall mining encourages the roof to fail to relieve the strains on the working face and this generates a subsidence trough. The ground movement migrates upwards and outwards from the seam being mined and ultimately causes the subsidence and deformation of the ground surface. Methods are available to predict mining subsidence so that existing or proposed structures and land developments may be safeguarded. Ground investigative methods and geotechnical engineering options are also available for sites that have been or may be adversely affected by coal mining subsidence.

5 citations

Dissertation
01 Nov 2015
TL;DR: In this article, a methodology was developed to increase the packing efficiency of concrete aggregate combinations and use of microfine fillers (finer than 75 μm) in order to make better use of scarce aggregate resources near urban centres while simultaneously reducing the required cement paste content of concrete to improve sustainability, durability, strength, workability, and cost.
Abstract: A methodology was developed in this study to increase the packing efficiency of concrete aggregate combinations and use of microfine fillers (finer than 75 μm) in order to make better use of scarce aggregate resources near urban centres while simultaneously reducing the required cement paste content of concrete to improve sustainability, durability, strength, workability, and cost. A 32% reduction in the portland cement content of a typical 35 MPa concrete mixture was successfully made, meeting all performance criteria evaluated, including workability, CSA A23.1 low-shrinkage and C-1 exposure class requirements, while significantly improving compressive strength. Several concretes that included a significant aggregate volume proportion of low-value intermediate aggregate materials and/or manufactured sands successfully met all performance criteria evaluated. Concrete mixtures conducted indicate that the effectiveness of the predominantly used 0.45 Power Chart for optimization of the total combined aggregate gradation can be substantially improved by considering the influence of aggregate particle shape, angularity and surface texture. A practical method for accurately measuring separate shape, angularity, and surface texture parameters, along with specific surface area of aggregates was developed in this study

5 citations

01 Jan 2011
TL;DR: In this article, an experimental study has been made to develop a relationship between the aggregate shape factors in terms of Combined Index (CI) and Angularity Number and the gradation index 'n' in the Fuller - Thompson ideal gradation equation to arrive at the optimum gradation.
Abstract: A satisfactory bituminous mix should have aggregate gradation, which will ensure maximum density and minimum voids in the mix to fulfill requirements of bituminous mix design specifications. In India organizations such as Indian Roads Congress and Ministry of Surface Transport (MOST) (1) have laid down specifications regarding the range of percentage passing of different size of aggregate in the mix. The conventional procedure is to aim at mid values of these specified ranges for the design of bituminous mix. However, this mid point gradation does not produce a satisfactory mix as it often fails to fulfill the specified requirements of the bituminous mix. This is because the density and voids in a mix depend on the shape factors namely Angularity Number (AN), Flakiness Index (FI) and Elongation Index (EI) of different aggregates in the mix. An experimental study has been made to develop a relationship between the aggregate shape factors in terms of Combined Index (CI) and Angularity Number and the gradation index 'n' in the Fuller - Thompson ideal gradation equation (2) to arrive at the optimum gradation. The results obtained using the conventional mid point of gradation range and those using the proposed optimum gradation concept have been compared in this paper. It is generally observed that the mixes prepared at the optimum gradation considering the CI and AN have higher density and lower voids compared to those at mid point of gradation ranges. The empirical equation developed in the study could be advantageously made use of for mix design.

Cites background from "A simplified approach for mix desig..."

  • ...The preliminary attempt to consider the shape factors along with aggregates gradation during mix design was reported by Rajagopal etal[2]....

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  • ...According to Fuller [2] the ideal gradation of aggregate consisting of spherical and rounded particles that could produce maximum dry density is given by the relation P % = 100 (d/D) ------ 1 where p is the percentage aggregate passing any sieve size d and D is the maximum aggregate size in the mix....

    [...]

  • ...According to Fuller [2] the ideal gradation of aggregate consisting of spherical and rounded particles that could produce maximum dry density is given by the relation P % = 100 (d/D) ------ 1 where p is the percentage aggregate passing any sieve size d and D is the maximum aggregate size in the…...

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References
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Book
01 Jan 1952

81 citations

01 Jan 1954
TL;DR: In this article, the authors studied the effect of the shape of the coarse agregate on the stability of the mixture of bituminous mixtures in three different agregates: rounded NATURAL SAND, rounded CRUSHED LIMESTONE, and rounded UNCRUSHED GRAVEL.
Abstract: THE EFFECTS OF AGGREGATE SHAPE ON THE STABILITY OF BITUMINOUS MIXES WERE STUDIED USING THREE VARIABLES: (1) SHAPE OF THE COARSE AGGREGATE, (2) SHAPE OF THE FINE AGGREGATE, AND (3) AGGREGATE GRADING. VARIATION IN THE COARSE AGGREGATE SHAPE WAS OBTAINED BY USING ANGULAR CRUSHED LIMESTONE, ROUNDED UNCRUSHED GRAVEL, AND CRUSHED GRAVEL. ROUNDED NATURAL SAND AND ANGULAR CRUSHED LIMESTONE PROVIDED THE CONTRAST IN THE SHAPE OF THE FIRE AGGREGATE. TO FURTHER KNOWLEDGE OF THE INFLUENCE OF CRUSHED GRAVEL ON THE STRENGTH OF BITUMINOUS-AGGREGATE MIXTURES, SEVERAL COMBINATIONS OF CRUSHED AND UNCRUSHED GRAVEL WERE USED ALSO. THE EFFECT OF THESE DIFFERENTLY SHAPED AGGREGATES ON THE STRENGTH CHARACTERISTICS OF BITUMINOUS MIXTURES MADE FROM THEM WERE STUDIED IN THREE REPRESENTATIVE AGGREGATE GRADING REFFERED TO AS DENSE, OPEN, AND ONE-SIZE GRADINGS. ALL OF THE BITUMINOUS MIXTURES TESTED WERE HOT MIXTURES IN WHICH AN ASPHALT CEMENT WAS USED, AND ASPHALT CONTENT WAS KEPT CONSTANT FOR EACH GRADING.

26 citations