CEMENT CONCRETE CONSTRUCTION MATERIAL AND TESTING CMT

PPT NOTES

1. CONCRETE CEMENT

2. Table of Contents 01 Introduction Study of materials for various applications. 02 ADMIXTURES Classification and characteristics of admixtures . 03 PROPORTIONING CONCRETE INGREDIENTS Permeability and durability of concrete. 05 CONCRETE MANUFACTURING Production of concrete. 04 CONCRETE ESTIMATING Determining concrete quantities for a construction project. 06 CONCRETE MIXING The actual mixing of concrete.

3. Table of Contents 07 CONCRETE MIXING METHODS Stationary or central mixers. 08 TESTING CONCRETE The sample of concrete to be tested. 09 COMPRESSIVE STRENGTH TESTS Important property of hardened concrete.

4. Introduction Cement concrete is a concentrated suspension containing solid aggregates suspended in a viscous liquid of cement paste . Portland cement concrete The National Ready Mix Concrete Association, based upon the use of well – shaped cubical aggregate as the standard, suggest that flat, elongated, or sharply angular aggregates will require 25 lb. of water more per cubic yard, thus requiring more cement to maintain the same water cement ratio. Importance This requirement is important when using manufactured sand because it contains more flat, elongated particles than natural sand.

5. In the judgement of engineer, the concrete is workable and can be placed without honeycomb or excessive voids, these requirements my be modified.

6. The weight of an aggregate per unit volume is called bulk unit weight . Aggregate’s bulk unit weight , or density in pef or kg/m3. Insulating lightweight aggregates 6-70 lb. per cu. ft Structural lightweight aggregates 30 – 70 lb. per cu. ft Normal – weight concrete aggregates 75 – 110 lb. per cu. ft Heavy weight concrete aggregates 110 – 290 per cu. ft Cement concrete

7. The specific gravity is not a measure of aggregate quality, but it used to design and control concrete mixes. The specific gravity is defined as the ratio of the solid unit weight of a substance to the weight an equal volume of water.

8. Wet weight – weight of solid material plus absorbed water filling the pores plus some free water on the particle surfaces. The amount of free water is variable. Saturated surface dry weight – weight of solid material plus enough absorbed water to fill pores. Air dry weight - weight of solid material plus some variable amount of water in the pores. Oven dry weight – weight of solid material only. This is the most consistent weight because no one water is included. Aggregate moisture conditions

9. Total moisture (%) wet weight – oven dry weight oven dry weight Absorbed moisture ( %) saturated surfaced dry weight – oven dry weight oven dry weight Free moisture ( %) Total moisture (%) – absorbed moisture (%) ( 100 ) (100)

10. admixtures Defined as any material other than Portland cement, aggregates, and water added to a concrete or mortar mix before or during mixing.

11. Admixtures are generally used for one or more of the following reasons: 1.To improve workability of the fresh concrete 2. To reduce water content, thereby increasing strength for a given water- cement ratio 3. To increase durability of the hardened cement 4. To retard setting time or increase it admixtures

12. 5.To impart color to concrete 6. To maintain volume stability by reducing or offsetting shrinkage during curing 7. To increase concrete resistance to freezing and thawing admixtures

13. Trial mixes Nominal mix Design mix small sample batches duplicate job conditions as accurately as possible so that the admixture dosages and results will be close to job expectations. Trial mixes also allow study of admixture’s compatibility if more than one admixture is to be used in the concrete.

14. Type of admixtures accelerators ( ASTM C 494 and AASHTO M 194, TYPE C.) DESIRED EFFECTS Accelerate setting and early- strength development . material Calcium chloride ( ASTM D 98 and AASHTO M 144 ) Triethanolamine , sodium thiocyanate, calcium formate, calcium nitrite, calcium nitrate

15. Type of admixtures Air – entraining admixtures ( ASTM C 260 and AASHTO M 154) DESIRED EFFECTS Improved durability in freeze – thaw, deicers, sulfate, and alkali- reactive environments . Improve workability material Salt of wood resins (Vinsol resin), some synthetic detergents, salts of sulfonated lignin, salts of petroleum acids, salts of proteinaceous material, fatty and resinous acids and their salts

16. Type of admixtures retarder ( ASTM C 494 and AASHTO M 194, TYPE B) DESIRED EFFECTS Retard setting time material Lignin, borax, sugars, tartaric acid and salts

17. Type of admixtures Water reducer ( ASTM C 494 and AASHTO M 194, TYPE a) DESIRED EFFECTS Reduce water content at least 5% material Lignosulfonates, Hydroxylated carboxylic acids, Carbohydrates ( also tend to retard set so accelerator is often added

18. Duff Abrams published his initial research on the water- cement ratio ( w/c) concept in 1918, indicating that the ratio of water to cement was related to concrete strength. Proportioning concrete ingredients

19. Currently it is also accepted that lower water-cement ratios reduced the permeability and improve the durability of concrete. The term water – cement ratio has been modified to water- cementitious material ratio ( w/c + m) or ( w/cm)

20. Proportioning may vary from the simple 1:2:3 formula which means 1 part cement, 2 parts fine aggregates, 3 parts coarse aggregate, to the ACI 211.1 mix design procedure which is included in the Appendix. Proportioning concrete ingredients

21. Trial batches are usually produced and tested before actual production of concrete begins. If the cement ratio is given, the technician can produce a paste (water and cement) for that water ratio and vary the fine aggregates and coarse aggregates to produce different aggregate ratios.

22. To produce quality concrete, the batching and measuring of ingredients must be done accurately Concrete can be mixed by hand in small portable mixers, in transit mix trucks, and in large stationary mixers ASTM C94 specifies weight measurements be made to be required tolerances Concrete manufacturing Weighing materials allows for adjustments in moisture conditions, especially in the fine aggregates where bulking can occur due to moisture

23. The mixing equipment is usually rated for two functions: first, the actual mixing of the ingredients to produce concrete, and the second, the agitating of already mix concrete. Concrete mixing

24. Mixers equipment Stationary mixing equipment can be found on jobs which require large amounts of concrete at steady rate. Many of the stationary mixers have timing devices which can be set and locked to prevent the discharge of the concrete before proper mixing time has elapsed.

25. Concrete mixing method Dry mix The dry materials are thoroughly mixed with enough water to prevent dusting. Wet mix Utilizes wet mortar or concrete forced through the delivery hose to the nozzle, where compressed air is introduced to increase the velocity of the material. Paving mixers Are concrete mixers mounted on crawlers treads. Shotcrete Is a nonproprietary term used to describe mortar or concrete that is placed by high velocity compressed air and adheres to the surface on which it is projected.

26. Concrete mixing method Transit mixed Completely mixed in truck. The ingredients are batched, water is added, and the concrete is mixed in the drum mounted on a truck. Shrink – mixed Combination of central mix and transit mix, with mixing requirements split between the central plant and the transit truck. Ready mix The most familiar concrete production system. Central mix Is mixed in a stationary mixer at the producers yard and delivered to the job site in a transit mixer operating at agitating speeds, in an agitator truck, or in dump truck.

27. Testing concrete astm makes provision for sampling fresh concrete in C172. WORKability A composite term used to denote the ease with which concrete can be mixed, transported, placed and finish with segregation . Consistency A major requirement in fresh concrete, denoted by the fluidity of the concrete as measured by the slump test.

28. Testing concrete Astm c137 test for air content of freshly concrete by the volumetric system. Astm c231 Test for air content of freshly mixed concrete, by the pressure method . Astm c138 Unit weight, yield, and air content (gravimetric) of concrete.

29. Volumetric method Can be used with all types of aggregates and is recommended for lightweight or porous aggregates PRESSURE METHOD cannot be used with lightweight or porous aggregates

30. Chace air indicator a nonstandardized test used to measure air content of plastic concrete Unit weight Determined in pounds per cubic foot or kilograms per cubic meter, and yield is the number of cubic feet or cubic meters of concrete produced from a mixture of known quantities of materials

31. Compressive strength test The measured maximum resistance to axial loading, expressed as force per unit of cross- sectional area in pounds per square inch (psi). The designer of a concrete structure selects a desired compressive strength ( f’ c ) for the concrete.

32. quiz It is affected by particle texture and shape more than hardened concrete a. Fresh concrete b. aggregate c. none of the above Defined as any material other than Portland cement, aggregates, and water added to a concrete or mortar mix before or during mixing a. Admixtures b. concrete c. aggregates

33. 3. Who published his initial research on the water- cement ratio? a. Ivan Brahms b. Duff Abrams c. Maximo Abrams 4. Concrete mixers mounted on crawler treads Paving mixers b. shotcrete c. Shrink – mixed 5. Method that can be used with all types of aggregates a. Volumetric b. pressure c. Testing

34. Thank you!