use of granite waste as powder in scc for whitetopping

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use of granite waste as powder in scc for whitetopping

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INTRODUCTION

GENERAL INTRODUCTION
Reinforcing old flexible pavements with concrete layers is called as whitetopping. It is a technique that deserves to be divided under to major s procedures.
Construction of normal thickened slabs over the old pavement and the application of thin cement concrete layers (about 100 mm) with more closed joints, defining square shaped slabs.

There are three types of whitetopping:
1. Ultra thin whitetopping (UTW).
Typically 100mm or less thick, with joint spacing ranging from 2 to 6 feet (ft), this type of whitetopping is used primarily for urban intersections, city streets, and overall low-volume roads. UTW relies on its bond to the existing asphalt pavement for performance.
Thin whitetopping (TWT).
This type is greater than 100mm and less than 200mm thick with joint spacing from 4 to 12 ft. Like UTW, TWT relies on the bond with the underlying asphalt pavement for good performance. TWT is the most prevalent type of whitetopping overlay highway agencies use.

Conventional whitetopping.
More than 200mm thick, this type of whitetopped pavement follows the behavior of a concrete pavement in terms of performance.

UTW solutions for reinforcing old flexible pavements can require concrete flexural strengths ranging from conventional concretes (4.5 to 5 MPa) to very high strength concretes (more than 10 MPa). This great variance will be found depending on the kind of road and on the heavy traffic volume.

Durability is considered to be one of the important aspects for any structure. The durability of concrete is directly related to the degree and quality of consolidation efforts. Using conventional placing and vibration techniques, the resulting concrete can have considerable honey combing due to development of voids. This problem occurs predominantly in reinforced structures with congested reinforcement. Many parts of the world are experiencing this problem.

There are no practical means by which compaction of concrete on a site ever be fully guaranteed. Vibrating the concrete in congested location also causes some risk to labors. There are also doubts about strength and durability. The lack of uniform and complete compaction had been identified as the primary factor responsible for poor performance of concrete structure.

As a result, research have been conducted in different parts of the world which led to the development of a new type of concrete known as SELF COMPACTING CONCRETE (SCC), which could be a solution to most of these problems.

Self-Compacting Concrete is considered to be a concrete which can be placed and compacted under its own self weight with little or no vibration effort and which is at the same time cohesive enough to be handled without any segregation or bleeding.

SCC got its initiation in JAPAN. It was first developed at THE UNIVERSITY OF TOKYO by Prof .H.OKAMURA and OZAWA and has since generated significant interest worldwide. Its innovative aspects lie in its fresh properties and the potential benefits to construction practice.

SCC plays a major role in precast concrete, where the speed of placing and removal of the elements from forms at the earliest are essential requirements, at the same time having defect free surface. SCC is a solution that solves most of the challenges and problems, which come across the concrete industries.

The SCC has gained wide use in many countries for different application and structural configurations. SCC requires a high slump, which can easily be achieved by incorporating several chemical admixtures. In particular, Superplasticizer and Viscosity Modifying Agent (V.M.A).

The superplasticizer influences the rheological behavior, the viscosity and the yield value of the fresh concrete are reduced in certain concrete mix. The super plasticizer ensures high fluidity and reduces water-powder ratio. Superplasticizer greatly improves the pump ability and the slump value can be greatly increased.

The use of Viscosity Modifying Agent increases the segregation resistance of concrete and increases the deformability without segregation and then to lead high optimum self-compatibility.

Self-compacting concrete plays a major role in increasing the use of industrial byproducts like slag, fly ash, silica fume and granite dust obtained during sawing process of granite rocks.. SCC offers possibility for utilization of dusts which are currently waste products demanding with no practical applications and which are costly to dispose off.

NEEDFOR THIS STUDY
Granite powder is a waste product obtained during the process of sawing of granite rocks in granite industries. As this granite dust is creating many environmental hazards, its disposal is a great problem. Self-compacting concrete contains a large quantity of powder materials which is required to maintain sufficient yield value of the fresh mix and hence reducing bleeding, segregation and settlement. Hence, it is worthwhile to investigate the influence of granite powder in SCC as filler.

PROPORTIONING OF SELF-COMPACTING CONCRETE
Absolute volume method is adopted for mix proportioning in this study, where cement and water contents are fixed so that self compactability can be achieved by varying granite powder, coarse aggregate and fine aggregate contents.
Cement content is fixed to 375kg/m3
Water content is fixed to 160ltr.
W/C ratio is fixed as 0.43, whereas water to powder ratio is varying because granite powder content is varying.
Granite powder used in this study has water absorption 23% - 25%, thus the same amount of water is added to granite powder before mixing.
The super plasticizer dosage and the final water-powder ratio are determined so as to ensure self-compatibility.

The powder is reported to contain large amount of very fine particles which are inert in nature. Since they are inorganic in nature they can be used in concrete without any durability issues.

OBJECTIVE OF THE STUDY
The main objective of this experimental investigation is to study
Physical properties of granite powder waste for its possible use as powder in SCC.
The influence of Granite powder on fresh and hardened properties of SCC.
To ascertain suitability of such SCC for the possible use as white topping.

SCOPE OF THE WORK
The scope is limited to the materials used for the experiments, which are
OPC 53 grade cement (Birla Super)
Natural river sand conforming to zone two
Coarse aggregate of size 20mm down
Granite powder (collected from JAI AMBE STONES, Granite industry, jigni industrial Area, anekal taluk, Bangalore 562106)
Superplasticizers (Glenium B233)

REVIEW OF LITERATURE

WHITE TOPPING

Whitetopping consists of a concrete overlay, or inlay, placed on existing hot-mix asphalt (HMA) surfaced pavement, as shown in Figure. Whitetopping is thus PCC resurfacing as a rehabilitation or structural strengthening alternative on bituminous pavement. Concrete overlays offer the potential for extended service life, increased structural capacity, reduced maintenance requirements and lower life cycle costs when compared with bituminous overlays.[Ref:16]