27-06-2013, 03:51 PM
A mini Project report IMPACT OF RICE HUSK ASH ON CEMENT CONCRETE
RICE HUSK ASH.docx (Size: 724.65 KB / Downloads: 239)
ABSTRACT
Concrete is the basic engineering material used in most of the civil engineering structures. Its popularity as basic building material in construction is because of, its economy of use, good durability and ease with which it can be manufactured at site. The ability to mould it into any shape and size, because of its plasticity in green stage and its subsequent hardening to achieve strength, is particularly useful. Concrete like other engineering materials needs to be designed for properties like strength, durability, workability and cohesion. Rice husk ash is obtained by burning rice husk in a controlled manner without causing environmental pollution. When properly burnt it has high SiO2 content and can be used as a concrete admixture. About 108 tonnes of rice husks are generated annually in the world.India produces about 122 million ton of paddy every year. Each ton of paddy produces about 40kg of RHA.
INTRODUCTION
In this project we have replaced the cement by RHA to certain percentages like 10%, 20%, 30%.Diferrent properties of cement, rice husk ash, fresh as well as hardened concrete which are influenced by adding this byproduct were studied. The rice husk thereby constitutes an environmental nuisance as they form refuse heaps in the areas where they are disposed. The use of rice husk ash as a partial replacement to cement will provide an economic use of the by – product and consequently produce cheaper blocks for low cost buildings. Use of RHA with cement improves workability and stability, reduces heat evolution, thermal cracking and plastic shrinkage. This increases strength development, impermeability and durability by strengthening transition zone, modifying the pore-structure, blocking the large voids in the hydrated cement paste through pozzolanic reaction. RHA minimizes alkali-aggregate reaction, reduces expansion, refines pore structure and hinders diffusion of alkali ions to the surface of aggregate by micro porous structure.
Aim of the project:-
The main aim of the project is to adopt a material which improves the properties of concrete and it should be somehow environmental friendly. The replacement even results in the cost reduction which can be highly used for low cost construction. Based on these objectives this project was undertaken.
BASIC INGREDIENTS OF CONCRETE
Cement
Cement is a hardened material with adhesive as well as cohesive properties. It is a building materials that is a powder made of a mixture of calcined limestone and clay; used with water and sand or gravel to-make concrete and mortar. Cement when mixed with water gets hardened. Cement and strength criteria are directly proportional to one another. Cement is useful to construct the walls, bricks, R.C.C works, plastering purposes etc.Portland cement is the most commonly used type of cement in the world today. On a chemical level, Portland cement is a fine powder comprised of a minimum of 66%calcium silicate, with the remainder largely being a mix of aluminium and iron. Various treatments and additives can make cement set and harden at different rates, and various types of Portland cement also posses different properties which affect the rate of setting and hardening.
Additional material for proposed concrete: Rice husk ash (RHA):
In addition to the basic ingredients, in this project we have used RICE HUSK ASH (RHA) as one of the material. It was used as the partial replacement of cement to a percentage of 10, 20, and 30.
Rice husk ash exhibits high pozzalanic characteristics and contributes to high strength and high impermeability of concrete.
There is a good potential to make use of RHA as a valuable pozzolanic material to give almost the same properties as that of micro silica.
In U.S.A., highly pozzolanic rice husk ash is patented under trade name Agro silica and is marketed.Agrosilica exhibit superpozzalanic property when used in small quantity i.e., 10%by weight of cement and it greatly enhances the workability and impermeability of concrete. It is a material of future as concrete admixtures.
EFFECT ON CEMENT
NORMAL CONSISTENCY:
For finding out initial setting time, final setting time and soundness of cement, and strength a parameter known as Standard or normal consistency has to be used. The standard consistency of a cement paste is defined as that consistency which will permit a Vicat plunger having 10mm diameter and 50mm length to penetrate to a depth of 33-35mm from the top of the mould. Vicat apparatus is used to find out the percentage of water required to produce a cement paste of standard consistency.
CONCLUSION
In this project we are partially replacing the cement with rice husk ash. Different properties of cement as well as concrete which of affected due to the introduction of RHA as a constituent of concrete were dealt in this project .Properties of high priority like compressive strength are favorable particularly at 10% replacement. However, workability of concrete and consistency of cement were greatly affected due to the replacement of cement with RHA.The mix was becoming harsh with increase in percentage of replacement of cement. But at 10%replacement, which is more likely to be adoptable it does not be very harsh.
From all the tests performed and results interpretated it can be concluded that the partial replacement of cement with RHA is advantageous and adoptable.