Fresh Properties Of Concrete - Civil Engineering

1. Fresh Properties OfThe Concrete A project report submitted in partial fulfilment of the degree of B.tech. in civil engineering

2. How Concrete Is Prepared Fresh concrete is a mixture of cement, fine aggregates, coarse aggregates, cement, suitable additives water. When the water is added to the cement the process of hydration gets started immediately. The study of fresh properties of concrete is important as properties of fresh concrete governs the properties of hardened concrete. Fresh properties of concrete include initial setting time, final setting time, workability, segregation and bleeding. https://civilenggascent.com

3. Workability https://civilenggascent.com

4. Workability Of The Concrete Workability is the measure that how easily we can work with concrete. We can use more workable concrete for pumped concrete. Workability could be measured by- - Slump Test - Compacting Factor Test Factors affecting the workability -Size and Shape of Concrete -Water/Cement Ratio -Use Of Admixtures -Fineness Of Cement https://civilenggascent.com

5. Measurement Of Workability Slump Test Slump test is most popular and the easiest method used on site to measure the workability. The equipment used in the slump test are a cone shaped metallic mold with guides having following dimensions. Top diameter – 10 centimeter Bottom diameter – 20 centimeter Height – 30 centimeter For temping the concrete a steel temping road of 16 mm diameter and 0.6 meter length is provided. https://civilenggascent.com

6. Compacting Factor Test For Testing Of The Workability Compacting Factor Test is somewhat more accurate than slump test. It is time consuming and an essentially a laboratory test. IS 456-2012 suggests that for low workability concrete, say to test the Pavement Quality Concrete the slump test should not be used and compacting factor test is must. The range of the Compacting Factor concrete varies from 0.5 to 0.99 Higher the Compacting Factor higher is the workability. Highly workable concrete has Compacting Factor more than 0.95 while the concrete having low degree of workability has Compacting Factor in the range of 0.78 to 0.87 Apparatus used in Compacting Factor test are shown in followoing figure. https://civilenggascent.com

7. https://civilenggascent.com

8. Effect Of Admixtures On Workability Use of Plasticizers and water reducing admixtures gives more workability for the same amount of water. Plasticizers also increases the setting time of concrete thus allows more time before placing the concrete. This property of plasticizers help us reducing water content of the concrete and thus reduced w/c ratio gives more strength for the same degree of workability. Most popular and commonly used plasticizer is SBR. [Styrene Betadine Rubber] SBR is available under many brand names in India, few are, Letecrete, BASF, Doctor Fixit from Pidilite, Sika chemicals, Roff, etc. https://civilenggascent.com

9. Effect Of Water/Cement Ratio On The Workability Higher the W/C ratio higher will be the workability. But this higher W/C ratio costs the decrease in strength. Water allows concrete constituents to move freely as it reduces the friction on aggregates surfaces. Effect Of Aggregate Shape On The Workability Angular shaped aggregates have property of interlocking, and gives lesser workability. Rounded aggregates have shown good workability. Rounded aggregates are the most suitable for pumpable concrete. Also rounded aggregates have less surface are for the same space they occupied as angular aggregates. This means that less amount of cement is needed to cover a round shaped aggregate. https://civilenggascent.com

10. Initial And Final Setting Time Of The Concrete https://civilenggascent.com

11. Initial Setting Time Of The Concrete It is defined the time elapsed after adding the water in the cement till the cement paste starts losing its plasticity. Final Setting Time Of The Concrete Final Setting Time is the time between adding the water to cement and the cement paste lost its plasticity and starts gaining some firmness. As per Is 456-2000 the initial setting time should be at least 30 minutes and final setting time should not exceed 600 minutes or say 10 hours. Setting time can be measured by vicat Apparatus. https://civilenggascent.com

12. Vicat Apparatus For The Measurement Of Setting Time https://civilenggascent.com

13. Segregation And Bleeding https://civilenggascent.com

14. Segregation It is the property exhibit by fresh concrete which means all the or some of the constituents of concrete gets separated after placing the concrete. This could happen because of over mixing of the concrete or over compaction. Segregation could lead to serious impact on the strength of hardened concrete. The only remedy to prevent segregation is the use of lower Water/Cement ratio. https://civilenggascent.com

15. Bleeding Appearance of the fresh water on the surface of freshly laid concrete is termed as bleeding. Bleeding is particularly not harmful. But it will make concrete porous and impacts up to some limit on the strength of hardened concrete. The one remedy to prevent bleeding is to remix the concrete before placing. https://civilenggascent.com

16. This presentation is exclusively prepared by Civil Engg Ascent team. You can find us on social media with following handles. Facebook - https://www.facebook.com/DiligentCivil Twitter - https://twitter.com/CivilAspiring https://twitter.com/CivilBright105 Warmest Regards- Vimal R. Bhojani https://www.linkedin.com/in/vimalbhojani Web address – https://civilenggascent.com https://civilenggascent.com

17. References- 1] Concrete Technology – Theory and Practice M.S.Shetty., S.Chand Publishing house 2] Properties Of Concrete Neville 3] Design of concrete mixes – Krishna Raju,N. 4] IS 10262 – 2019 [Revised] Recommended Guidelines For Concrete Mix Designs 5] IS 456 – 2012 Design criteria for RCC structures https://civilenggascent.com