Bridge Materials

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 2 A porous non-homogenous material that is made of cement, water, fine aggregate (sand), coarse aggregate (gravel), and air. Ratios –Aggregate(75 to 80%) –Cement(10 to 15%) –Water and Air(remainder) Concrete Material Properties What is Concrete?

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 3 Admixtures Ingredients used to modify certain properties of concrete to have a desired function Air-entraining - improves air void structure Water reducers - reduces water in the mix Superplasticizers - increases slump Accelerators - increases set rate Retarders - decreases set rate

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 4 Physical Properties Compressive strength(28 day) Tensile strength(10% f’c) Permeability –Causes:- evaporation of bleed water - excess water - micro-cracking - porous aggregates - improper mixing, finishing

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 5 stress strain Concrete Stress-Strain Diagram

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 6 Concrete Damage & Deterioration Types of Cracks –Crazing - surface cracking, from surface drying –Shrinkage - tension caused by reduction in moisture –Temperature Cracking - restrained thermal changes –Flexural Cracking - tension from flexural bending –Shear Cracking - diagonal tension from loads

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 7 Concrete Defects (cont’d) Scaling - freeze thaw, surface finishing Pop-Outs- porous aggregate Abrasion- wheel wear Spalling- corrosion of steel Delamination- debonding of substrate Staining- rust Alkali Aggregate Reaction Carbonation

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 8 Steel Material Properties What is Steel? –It is an alloy of iron, carbon and other trace elements. Ratios –Carbon0.15 to 1.7% –Manganese0.5 to 2% –Phosphorus0.05 to 0.6% –Sulphur0.02 to 0.06% –Silicone0.80 to 1.5%

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 9 Iron Iron in the pure form is a soft, shiny metal like aluminum. However, it is never found in this state. Iron oxidizes extremely easily. In nature it is always found as an oxide.

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 10 Steel Making Process To convert iron ore to pig iron, ore is heated with coke. Pig iron has 2 to 5% carbon. Steel cannot have more than 1.7% carbon.

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 11 Effects of Carbon Increased carbon in steel: –increases strength –increases hardness –increases hardenability (heating and quenching) –reduces ductility –reduces toughness –reduces impact properties –reduces machinability

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 12 Physical Properties Compression Tension Fatigue Weldability Notch toughness

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 13 Tension & Compression Stress Strain Diagram (-) lengthen (+) (+) stress tension compression shorten

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 14 Concrete - Steel Combination Reinforced Concrete Mild steel for tension Always cracks under load Prestressed Concrete High strength steel strands Precompressed Carry load without cracking

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 15 Steel Damage and Deterioration Corrosion –moisture, oxygen, electrical potential Cracking –fatigue, impact, excessive loading Deformation –excessive loading, impact

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 16 UNCONTROLLED WELDING IS NOT ALLOWED ON BRIDGE STRUCTURES.

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 17 Timber Material Properties What is wood? –A naturally occurring material containing carbohydrate compound fibres and water. (It grows on trees!)

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 18 Cross Section of Tree

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 19 Composition of Wood Carbohydrate fibres –oriented in longitudinal direction –not homogenous through cross-section Water –moisture can reach 200% of sap wood –19% is considered seasoned

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 20 Physical Properties Compression - perpendicular to grain - parallel to grain Tension Bending Shear - horizontal shear Shrinkage - 60% radially - 2% longitudinally

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 21 Timber Damage & Deterioration Warping Checks & Splits Flexural Cracking Shear Cracking Fire Damage Decay

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 22 Decay Caused by fungi which feed on cellulose Growth of fungi depends on: –adequate moisture –supply of O 2 –favorable temperature Moisture content below the fibre saturation point (30%) inhibits fungus growth.

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 23 Decay (cont’d) Air is in wood cells, but constantly submerged piles will inhibit fungus by lack of oxygen. Fungus goes dormant over winter but will reactivate in the spring. High kiln drying temperatures will kill fungus, but the wood can be reinfected. Insects and borers are not a problem in Alberta.

BRIDGE MATERIALS TECHNICAL STANDARDS BRANCH INTRODUCTION TO BRIDGES TRANSPORTATION Slide 24 Treatment Treatment chemicals toxic to fungus, insects and man. Only exterior is protected Pressure treatment improves penetration