2. Topic : MIX DESIGN OF CONCRETE

3. Properties of concrete Submitted To: DR. AYUB ELAHI Submitted By: SOHAIB NASEER 2K9-scet-29/CIVIL M.ZAEEM FAKHAR 2K9-scet-03/CIVIL ISRAR–UL–HAQ 2K9-scet-30/CIVIL AWAIS ULLAH 2K9-scet-31/CIVIL BILAL RIAZ 2K9-scet-59/CIVIL

4. INTRODUCTION Concrete is the second largest material consumed by human beings after food and water as per WHO. It is obtained by mixing cement, fine aggregate, coarse aggregate and water in required proportions. The mixture when placed in forms and allowed to cure becomes hard like stone. The hardening is caused by chemical action between water and the cement due to which concrete grows stronger with age.

5. INTRODUCTION The strength, durability and other characteristics of concrete depend upon the properties of its ingredients, proportion of the mix, the method of compaction and other controls during placing, compaction and curing.

6. Definition the process of selecting suitable ingredients of concrete and determining their relative proportions with the object of producing concrete of certain minimum strength and durability as economically as possible

7. Objective In Designing Concrete Mixtures To determine the most economical & practical combination of readily available materials to produce a concrete that will satisfy the performance requirements under particular conditions of use

8. Designing Concrete Mixtures Factors to be considered Workability Placement conditions Strength Durability Appearance Economy

9. Factors to be considered Strength – important to the design engineer Durability – important to the owner Workability – important to the contractor Economy – important to the owner Proportioning concrete is the art of optimizing the mixture to meet these requirements

10. Methods Of Selection Of Mix Proportions There are two main methods for the selection of mix proportions of concrete.  American method  British method

11. Steps For Mix Designing ACI METHOD 1. Choice of slump 2. Choice of max. Size of aggregates 3. Estimate of water and air contents 4. Selection of water cement ratio 5. Calculation of cement contents 6. Estimate of coarse aggregates content 7. Estimate of fine aggregates content 8. Adjustments to mix proportion

12. Steps For Mix Designing BRITISH METHOD 1. Determining the Free Water/ Cement Ratio 2. Determining the Free-water Content 3. Determining the Cement Content 4. Determining the Total Aggregate Content 5. Determining of The Fine and Coarse Aggregate Contents

13. Coarse Aggregate Requirement Grading Nature of particles –Shape –Porosity –Surface texture

14. Max Aggregate Size Cover between steel & form, C: Dmax <3/4C Spacing between bars, S: Dmax <3/4S Depth of slab, D: Dmax <D/3

15. Max Aggregate Size (For pumped concrete) Dmax < 1/3 diameter of hose or 1-1/2 inch, whichever is smaller

16. Fineness Modulus of Sand The FM is calculated from particle size distribution of the sand Values should range between 2.3 to 3.1 Coarse sand has a higher FM than fine sand FM influences the bulk volume of coarse aggregate

17. Air Content The amount needed depends on: Max aggregate size –Less paste as size increases

18. Workability Requirements Concrete must always be made with a workability, consistency and plasticity suitable for job placement

19. Workability Requirements Concrete ConstructionSlump Maximum Slump Minimum Reinforced walls & footings31 Plain footings, caissons, and Substructure walls 31 Beams & reinforced walls41 Columns41 Pavements and slabs31 Mass concrete31

20. Water cement ratio  Range of w/c= 0.45 to 0.65  For mix design of  1:2:4  The w/c is standardized as 0.5

21. Water Content Water demand is influenced by:  Slump requirement  Aggregate size  Aggregate shape  Air content  Cementing materials content  Temp  Admixtures

22. Slump mm Water. Kg/m 3 of concrete for idicated nominal maximum size of aggregate 9.512.5192537.55075150 Non-air entrained concret 25 to 50 207199190179166154130113 75 to 1oo 228216205193181169145124 150 to 175 243228216202190178160- Amount of air entrapped % 32.521.510.50.30.2 Water Contents

23. Cement Content Cement Material Content= Water Content W/CM Minimum cement content may be specified for the purpose of: –Durability –Finishability –Wear resistance –Appearance Excessively high cementitious contents should be avoided for: –Economy –Avoid adverse effects Workability Shrinkage Heat of hydration