This study had investigated the admixture properties of plantain peel ash through a series of laboratory experiments. This was targeted at obtaining an effective admixture while relieving the environment from the menace of environmental pollution arising from indiscriminate disposal of agricultural wastes. Plantain peel ash was blended with dry cement at 11 different percentage additions at 0%, 0.2%, 0.4% up to 2.0% for cement pastes and mortar. The cement paste was tested for setting time and soundness to BS EN 196:3-1995 while mortar prisms were tested for flexural and compressive strength to BS EN 196:1 1995, after which, scan electron microscopy (SEM) was carried out on samples of mortar tested at 28 days. Setting time tests results has indicated a retardation in setting of the cement paste with the addition of plantain peel ash whereas the early strength development of the cement was delayed by the ash additions as indicated by the strength tests. From the soundness test results, the ash was found to have no impact on the soundness of the cement as the maximum expansion recorded was 1mm at 0.2% and 1.0% ash contents. The result of the SEM analysis indicated that a mortar prism with higher ash contents tends to have a more porous microstructure. Based on the results, the ash was categorized into a class of set retarding admixture as per the provisions of BS EN 934 part 2(2000) while the optimum ash content recommended for use is 1.0% by weight of cement.
TABLE OF CONTENTS
Cover Page I Fly Page II Title Page III Declaration IV Certification V Acknowledgements VI Abstract VII Table of Contents VIII-XII List of Tables XIII-XIV List of Figures XV List of Plates XVI List of Appendices XVII Abbreviations XVIII Chapter One 1.0 Introduction 1 1.1 General Background 1-2 1.2 Statement of the Problem 3 1.3 Justification for the Study 3 1.4 Aim and Objectives 4 1.4.1 Aim 4
1.342 Objectives 4
1.5 Scope and Limitations 4 1.5.1 Scope 4-5 1.5.2 Limitations 5 Chapter Two 2.0 Literature Review 6 2.1 Chapter Two Preamble 6 2.2 Plantain Peel Ash 6 2.2.1 Chemical composition of Plantain Peel Ash (PPA) 7-9 2.2.2 Properties of other Agro waste Ashes 9-10 2.3 Chemical Composition of Ordinary Portland Cement (OPC) 10-12 2.3.1 Effect of Alkali on the Properties of Cement 12-14 2.4 Standard Tests on Cement 14 2.4.1 Fineness Test on Cement 14-15 2.4.2 Consistency Test on Cement 15 2.4.3 Setting Time Test on Cement 15-16 2.4.4 Soundness Test on Cement 16-17 2.4.5 Strength Test on Cement 17-18
2.5 Standard Sand for Cement Mortar 18-19
2.6 Admixtures 19-21 2.6.1 Water-reducing Admixtures 20-22 2.6.2 Retarding Admixtures 22-23 2.6.3 Accelerating Admixtures 24 2.6.4 Super plasticizers 24-26 Chapter Three 3.0 Materials and Methods 27 3.1 Introduction to Chapter Three 27 3.2 Materials 27 3.2.1 Plantain Peel 27 3.2.1 (a) Acquisition 27 3.2.1 (b) Drying of Plantain Peel 27 3.2.1 (c) Burning of Plantain Peel 27 3.2.1 (d) Sieving and Storage 28 3.3 Chemical Analysis of PPA 28 3.4 Specific Gravity Test on PPA 29 3.5 Fineness Test on PPA 29 3.6 Cement 29 3.6.1 Acquisition 29
3.6.2 Fineness test on cement 30
3.7 Fine Aggregate 30 3.7.1 Acquisition 30 3.7.2 Grading 30-31 3.7.3 Specific Gravity of Sand 31 3.8 Tests on Cement-Ash paste 32 3.8.1 Consistency Test 32 3.8.2 Setting Time Tests 32-33 3.8.3 Soundness Test 33-34 3.9 Tests on Cement-Sand Mortar 34 3.9.1 Preparation of Test Specimens 34 3.9.2 Flexural Strength Test 35-37 3.9.3 Compressive Strength Test 38-40 3.10 Scan Electron Microscopy 40-43 Chapter Four 4.0 Discussion of Results 44 4.1 Preamble To Discussion Of Results 44 4.2 Analysis of Chemical Composition of PPA 44-46 4.3 Effect of PPA on Setting Time 46-48
4.4 Effect of PPA on Early Strength Development of Mortar 48-49 4.5 Effect of Curing Age on Flexural Strengthof Mortar Admixed with PPA 49-50 4.6 Effect of Curing Age on Compressive Strength of Mortar Admixed with PPA 50-51 4.7 The Effect of PPA on Soundness 51-52 4.8 The Effect of PPA on Microstructure 53 4.9 Characterization of the Ash as Per BS EN 934 Part 2 (2000) 53-56 4.10 Optimum Content of PPA 56 Chapter Five 5.0 Conclusions and Recommendations 57 5.1 Conclusions 57 5.2 Recommendations 58 References 59-61
INTRODUCTION 1.1 General Background According to ASTM C 494 (1992), Admixture is defined as a material, other than cement, water and aggregates, that is used asan ingredient of concrete and is added to the batch immediately before or during mixing. They are broadly divided in to mineral and chemical admixtures. Chemical admixtures are commonly classified by their functions in concrete into seven types, as specified in ASTM C 494 (1992) viz: Type A- Water reducing, Type B-Retarding, Type C- Accelerating, Type D- Water – Reducing and Retarding, Type E -Water-Reducing and Accelerating, Type F-High-range water-reducing or Superplasticizing and Type G-High-range water-reducing and Retarding or Superplastcizing and retarding. These are added to concrete in very small amounts mainly for the entrainment of air, reduction of water or cement content, plasticization of fresh concrete mixtures, or control of setting time. Mineral admixtures in the other hand are usually added to concrete in larger amounts to enhance the workability of fresh concrete; to improve resistance of concrete to thermal cracking, alkali-aggregate expansion, and sulfate attack; and to enable a reduction in cement content. The source of mineral admixtures could be natural or artificially obtained as a by-product in the form of ashes, from the combustion of coal and some crop residues. . Neville, 2005
Dumping of these by-products into landfills and streams, amounts to a waste of the material and causes serious environmental pollution. With proper quality control, large amounts of many industrial by-products can be incorporated into concrete, either in the form of blended Portland cement or as mineral admixtures. Plantain peel are by-products of the plantain processing industry, which are normally dumped in landfills, rivers or unregulated grounds. National and international production of banana and plantain is ever booming, while local and domestic consumption is on the increase; but national and international programs for the resulting waste peel are rare, perhaps because information is lacking on the resources inherent in the waste peel; consequently, a huge amount of waste peel is dumped daily especially in Nigeria. A geometric increase in the generation of solid wastes in Nigeria calls for a sustainable management options in which reuse and recycling top the list (Babayemi and Dauda 2009). From the available literature, most of the studies conducted on the waste peel of plantain are science based. These researches however provide an idea of the chemical composition of the peel, based on which further studies could be carried out on the material especially its engineering properties.
In this study, the admixture properties of unripe plantain peel ash and its effect on the strength of cement will be investigated. Due to its alkaline nature as established by Onyegbado et al, 2002, its possible adverse effect on the total alkali content of the paste will be assessed.
1.2 Statement of the Problem .A study of the various researches carried out on mineral admixture derived from agricultural wastes, shows that they mostly focus on their use as pozzolanas. This study will therefore rather aim at producing a mineral admixture derived from plantain peel that will only be required in small dosages to perform its functions as an accelerator, retarder or any other type of admixture as established after characterizing the material. Nigeria is one of the largest plantain producing countries in the world (FAO, 2006). She ranked first in Africa and fifth in the world producing 2,722,000 metric tones in 2011 (FAO, 2012). Despite this large production, she does not export plantain because its production is largely consumed locally. The rise in cottage industries that make use of plantain for snacks (plantain chips) in the non-farming urban population coupled with the demand for easy and convenient foods made from plantain locally, made its consumption to be on the increase (Akinyemi et al., 2010). The high demand for plantain also generates wastes which are often discarded, and sometimes used for animal feeds. 1.3 Justification for the study Based on the findings of Olabanji et al,2012, the plantain peel ash contain high percentage of potassium(K), calcium (Ca) and iron (Fe) as reported by Olabanji et al (2012).
Bentz (2006) has reported that the addition of alkalis of lithium, sodium and potassium increases the early rate of cement hydration but reduces later age hydration and strength development. Based on the foregoing, it is important to study the admixture properties this material and its possible effects on some cement properties.
1.4 Aim and Objectives 1.4.1 Aim The aim of this study is to investigate the admixture properties of plantain peel ash (PPA),charachtrerize same study its effect on the strength and soundness of cement. 1.4.2 Objectives The objectives of this research are to:
i. Determine the chemical composition of PPA
ii. Investigate the effect of PPA on hydration, strength and soundness.
iii. Study and analyze the effect of the ash on the micro structure of cement-sand mortar
vi. Characterize the ash into the appropriate category of admixture as per BS EN 934 part 2, 2000, based on its properties observed.
1.5 Scope and limitations 1.5.1 Scope
This research work presents an investigation into the suitability of PPA as an admixture in concrete. The effect of PPA on the strength and soundness of cement will be investigated. Setting time tests will be conducted on normal cement paste to obtain control data. The test shall then be carried out on cement paste with various contents of the ash. The percentages of the ash used in the setting time test shall then be applied to produce mortar prisms, which would be eventually subjected to flexural and compressive
strength tests, soundness and micro structure analysis. Mortar prisms will also be cast with concrete produced at 0% ash content to serve as control specimens. 1.5.2 Limitations The research will be limited to the characterization of unripe plantain peel ash into the appropriate category of admixture in accordance with the specific requirements of BS EN 934 part 2, (2000)after studying its effect on the strength, setting time and soundness of cement. Other parameters lijke water reduction and air content will not be checked.
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