Fracture Toughness and Impact Strength of High-Volume Class-F Fly Ash Concrete Reinforced with Natural San Fibres
Results of experimental investigation carried out to study the effects of addition of natural san fibres on the fracture toughness and impact strength of high-volume fly ash concrete are presented in this paper. San fibres belong to the category of ‘Natural Bast Fibres’, also known as ‘Sunn Hemp’. Its scientific (botanical) name is Crotalaria Juncea. It is mostly grown in the Indian Sub-Continent, Brazil, Eastern and Southern Africa, and in some parts of the U.S.A. Initially, a control mixture without fly ash was designed. Then, cement was replaced with three percentages (30, 40 and 50%) of low-calcium (Class F) fly ash. Three percentages of san fibres (0.30, 0.60 and 0.90%), having 25 mm length, were used. Tests were performed for compressive strength, fracture toughness, and impact strength at the ages of 28 and 91 days. The test results indicated that the replacement of cement with fly ash decreased the compressive strength and fracture toughness, and had no significant effect on the impact strength of plain (control) concrete. Addition of san fibres did not affect significantly the compressive strength, increased the fracture toughness and impact strength of high-volume fly ash concrete as the percentage of fibres increased.
Durability of Flax Fibre Reinforced Concrete
............................................................................................................................ ii Acknowledgements.......................................................................................................... iii Table of Contents ............................................................................................................. iv List of Tables .................................................................................................................. vii List of Figures ................................................................................................................ viii 1. Introduction................................................................................................................ 1 1.1. Background ......................................................................................................... 1 1.2. Objectives............................................................................................................ 3 1.3. Scope and Methodology...................................................................................... 4 1.4. Outline of Thesis ................................................................................................. 4 2. Literature Review....................................................................................................... 5 2.1. Fibres ................................................................................................................... 5 2.1.1. Vegetable Fibre Structure ............................................................................. 6 2.1.2. Vegetable Fibre Mechanics .......................................................................... 7 2.1.3. Effect of Alkaline Substances on Vegetable Fibres ..................................... 8 2.1.4. Vegetable Fibre Treatment ........................................................................... 9 2.2. Fibre-Reinforced Concrete ................................................................................ 11 2.2.1. Fibre-Reinforced Concrete Performance.................................................... 12 2.2.2. Bonding between Vegetable Fibre and Cement Paste................................ 13 2.2.3. Vegetable Fibre-Reinforced Concrete Performance................................... 16 2.2.4. Effect of Weathering on Vegetable Fibre-Reinforced Concrete Performance .................................................................................................................... 18 2.2.5. Effect of Fibre Treatments on Bonding of Vegetable Fibre and Cement Paste .................................................................................................................... 22
Strength and Durability of Concrete Using Bottom Ash as Replacement for Fine Aggregate
It is anticipated that coal-fired thermal power stations will increase in Japan and that the discharged amount of coal ashes, which are industrial by-products, will rapidly increase in the future. In order to effectively use the bottom ash discharged from coal-fired thermal power stations, concrete which substitutes bottom ash from 0 to 40% by volume for fine aggregate was investigated in this study. The compressive strength, tensile strength, freezing and thawing resistance, and abrasion resistance of the concrete were examined. The results of the concrete strength tests indicate that the compressive strength and tensile strength of bottom ash concrete generally increases with the increase of replacement ratio of fine aggregate and curing age. The freezing and thawing resistance of concrete using bottom ash is lower than that of ordinary concrete and the abrasion resistance of bottom ash concrete is higher than that of ordinary concrete. The use of bottom ash in amounts of 10 to 40% as replacement for fine aggregate is effective in improving the concrete properties except for the freezing and thawing resistance.