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The Effect Of Admixtures On Properties Of Co`ncrete
[CASE STUDIES OF SUGAR, COW BONE ASH, GROUDNUT SHELL ASH, AND LIME STONE POWDER]
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Salt water does not have adverse effect on the strength and durability of concrete but known to cause surface dampness efflorescence and staining. Insufficient quantity of gypsum in concrete causes an immediate stiffening of cement paste with large amount of heat generated while further addition of it will reduce the heat generation and lower the setting time.
Admixture when added to concrete in large quantities affects the strength of concrete as well as all other properties. Sugar cause lack of proper cohesion and adhesion in concrete mix. It therefore retard the setting time of concrete. For an aggregate to be suitable for construction use the graph of the aggregate grade, for the aggregate sample must lie within the upper and lower limits of the standard grading. For workability test slump varies from 20mm for vibrated mass concrete to 130mm for heavily reinforced non vibrated concrete.
Granite which is called coarse aggregate as one of the concrete component should be hard, well shape, clean and fire resistance in nature while sand which is fine aggregate should be clean, free from clay and durability for concrete.
Cement which is the finest of all particles in concrete mix should be rich to produce strong, dense and durable concrete while water for concrete mix should be fresh, clean, and free from oil, acid, organic matters and solution due to pollution from industrial waste or similar drainage.
Setting time of cement are measured using the vacal apparatus with different penetrating attendant. For the determination of the initial set, around needle with a diameter 1.13 +_ 0.05mm is used. When the cement paste stiffens sufficiently for needle to penetrate only to a point 5+_ 1mm from the bottom, initial set is said to have taken place. Initial set is expressed as the time elapsed since the mixing water was added to the cement. BS 12:1975 prescribed a minimum time of 45 minutes for OPC.
Final set is determined by a similar needle fitted with a metal attachment hollowed out, so as to leave a circular cutting edge 5mm in diameter and set 0.5mm behind the lip of the needle, gentle lowered to the surface of the paste, makes on impression on it, but the water circular cutting edge fails to do so. The final setting time is reckoned from the moment when mixing water was added to the cement, and is required of the relevant British standard to be not more than 10hrs for OPC.
2.2 TYPE OF ADMIXTURES
Rixon and Mailvaganam (1986), admixture in concrete mix will influence the workability of concrete, voids percent, water absorption percent, strength and durability of the concrete, therefore it is necessary to classify or group admixtures according to the purpose for which they are used in concrete. They can be grouped as:
1. Accelerators: The use of accelerating admixtures is common during cold-weather concreting, as the rate of hydration of cement is decreased by lower temperatures. Their function is to increase the rate of hydration, thereby speeding up the setting time and early strength development. Examples of accelerators are calcium chloride, calcium nitrite, calcium chloride is commonly used but the use of calcium nitrite (also called a corrosion inhibitor) leads to a better strength gain at later ages than calcium chloride. Excessive amount of calcium chloride in concrete mix may results in several adverse effect such as increased drying, shrinkage, reduced resistance to sulphate attack and increase risk of corrosion of steel reinforcement, its should only be used with extreme caution and in accordance with any relevant specifications. It may usefully be employed for concreting in winter condition, emergency repair or where early removal of formwork were required.
2. Retarders: Slow down the hydration of cement, their function is to delay or extend the setting time of cement paste in concrete. They are used mainly in hot weather conditions in order to overcome the accelerating effects of higher temperature and large masses of concrete on concrete setting time. Because most retarders also act as water reducer. As per chemical admixture classification by ASTM C494, type B is simply admixture, while type D is both retarding and water reducer, resulting in concrete with greater compressive strength because of the lower water-cement ratio.
Retarding admixtures are used;
i. Where long transportation of ready mixed concrete is required then premature setting can be usefully avoided by this type of admixture,
ii. When concrete is being placed or transported under conditions of high ambient temperature,
iii. In case of large concrete pours,
iv. Concrete construction involving sliding formwork.
Retarding admixtures consist of both organic and inorganic agents. Organic retardants include:
i. Unrefined lignosulphonates containing sugar, which of course the component responsible for retardation,
ii. Hydroxyl carboxylic acid and their salts,
iii. Carbohydrates including sugar,
iv. Unrefined calcium, sodium and NH4.
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ABSRACT - [ Total Page(s): 1 ]ABSTRACT The project titled “The effect of admixtures on properties of concrete: case study of sugar, cow bone ash, groundnut shell ash, and lime stone powder†was carried out with the aim of knowing the effect the of the various types of admixtures used on the properties of concrete, in term of the workability of concrete, durability of concrete and the concrete strength. The material used are cow bone ash, groundnut shell ash, sugar and lime stone powder. The cow bone was sou ... Continue reading---
LIST OF TABLES - [ Total Page(s): 1 ]LIST OF TABLESTable 4.1: Data Analysis for Fine Aggregates (Sand) Table 4.2: Data Analysis for Coarse Aggregate (Granite) Table 4.3: Slump Test Result for GSA Concrete Table 4.4: Slump Test Result for CBA Concrete Table 4.5: Slump Test Result for Sugar Concrete Table 4.6: Slump Test Result for LP Concrete Table 4.7: Summary of Slump Test Result for Various Concrete Admixtures Table 4.8: Compressive Strength Test Result of Normal Concrete Table 4.9: Compressive Strength Test ... Continue reading---
LIST OF PLATES - [ Total Page(s): 1 ]LIST OF PLATESPlate 3.1: Groundnut Shell and Cow Bone Plate 3.2: Burning of Groundnut Shell and Cow Bone Plate 3.3: Cow bone ash, Groundnut shell ash, Limestone powder and Sugar. Plate 3.4: Batching of Concrete Plate 3.5: Type of Slump Plate 36: Cube Production Plate 3.7: Curing of Cubes Plate 3.8: Crushing Machine ... Continue reading---
LIST OF FIGURES - [ Total Page(s): 1 ]LIST OF FIGURESFigure 4.1: The graph of sieve analysis for Fine Aggregate (Sand) Figure 4.2: The graph of sieve analysis for Coarse Aggregate (Granite). Figure 4.3: The graph of slump test result for GSA Concrete Figure 4.4: The graph of slump test result for CBA Concrete Figure 4.5: The graph of slump test result for SUGAR Concrete Figure 4.6: The graph of slump test result for LP Concrete Figure 4.7: The graph for summary of slump test result for various Concrete AdmixturesFigure 4.8: Th ... Continue reading---
TABLE OF CONTENTS - [ Total Page(s): 1 ]TABLE OF CONTENTSTitle Page Declaration Certification Dedication Acknowledgement Abstract Table of Contents List of Tables List of Figures List of Plates CHAPTER ONE 1.0 Introduction 1.1 Statement of the Problem 1.2 Aims and Objectives of the Study 1.3 Justification of the Study 1.4 Scope of the Study CHAPTER TWO 2.0 literature Review 2.1 Concrete ... Continue reading---
CHAPTER ONE - [ Total Page(s): 2 ]CHAPTER ONE1.0. INTRODUCTION The importance of understanding various types of materials used in Civil Engineering is widely recognized. There has been tremendous increase in the latest research and practical achievement to improve on concrete technology. Free exchange for technical know ... Continue reading---
CHAPTER THREE - [ Total Page(s): 8 ]CHAPTER THREE3.0 PROJECT METHODOLOGY For successful accomplishment of the aims and objectives of this project the following methods are applied.i. Market survey for the most commonly used cement was carried out and it was found that elephant and dangote cement are the most commonly used in the locality due to their availability in the market all time.ii. Text books, internet and some experienced practicing engineer are consulted in order to obtain relevant and detailed ... Continue reading---
CHAPTER FOUR - [ Total Page(s): 16 ]D10 = 1.686μmm = 0.169mmD30 = 273.6μmm = 0.274mmD60 = 503.75μmm =0.504mmi. The effective grain size; i.e. D10 = 0.169mmii. Uniformity coefficient, Cu = = = 2.98iii. Coefficient of curvature, Cc = = = = 0.88D10 = 7.6mmD30 = 12.8mm D60 = 15.2mmi. The effective grain size; i.e. D10 = 7.6mm ii. Uniformity coefficient, Cu = = = 2.0iii. Coefficient of curvature, Cc = = = =1.42 ... Continue reading---
CHAPTER FIVE - [ Total Page(s): 1 ]CHAPTER FIVE5.0 CONCLUSION Based on the results of this investigation, the following conclusion is drawn; Admixtures affect properties of concrete like its slump value, density, compressive strength, etc. Admixtures generally decrease the slump value of concrete which in turns decrease the workability of the concrete, since normal concrete(0% concrete) has a slump value of between 55-60mm while concrete with admixture has slump value lesser ... Continue reading---
REFRENCES - [ Total Page(s): 1 ]REFERENCEAkogu Elijah Abalaka (2011): ‘Effects of Sugar on Physical Properties of Ordinary Portland Cement Paste and Concrete.Albadan B.A, M.A Olutoye, M.S Abolarin & M. Zakariya (2005): ‘Partial Replacement of Ordinary Portland Cement (OPC)with Bambara Groundnut Shell Ash (BGSA) in Concrete. Leonard Electronic Journal of Practices and Technologies. Issues 6, pp. 43 – 48, January – June 2005. Aribisala, O.J & Bamisaye, A.J (2006): ‘Via ... Continue reading---
