High Volume Fly Ash Concrete Building with Blended Cement at Amethi

Transcription

1 High Volume Fly Ash Concrete Building with Blended Cement at Amethi First of its kind in India The Associated Cement Companies Limited Anil Kumar Banchhor 1

2 Use of Fly Ash in Concrete IS permits use of fly ash in concrete Better utilisation of the fly ash, than in land filling Lab studies & field performance shows improved performance Use of fly ash leads to better pore refinement and minimized micro cracks Processed fly ash is available in some cities 2

3 Environmental Considerations Utilisation of Fly ash would reduce area required for disposal. The fly ash is less permeable to water, protecting reinforcing steel and adding to the concrete s durability. Materials that last longer reduce the demand for natural resources, thus preserving for future generations. Reduce CO 2 emission & saving energy. High volume fly ash concrete usually costs lower than the conventional concrete 3

4 High Volume Ash Concrete Previously the use of fly was limited to 20-25% fly ash in building concrete or in pavements containing 50% fly ash. In India, HVFAC containing 50% fly ash in RCC Building was used for the first time in the Rest Hall Building at Amethi, UP in Suitability of Fly ash based Blended cement in construction of RCC building with M-25 grade concrete containing 50% fly ash. 4

5 Acceptance of fly ash in cement The studies conducted in various laboratories have shown that the concrete made with blended cement are better than those with normal Portland cement Some issues have been raised regarding behaviour of fly ash based cement concrete with respect to its performance against carbonation ph and the corrosion, in a loaded structure. To alley the above apprehension and demonstrate the use of additional quantity of fly ash in concrete made with PPC cement, above project was conceived. It was proposed to study the behaviour of concrete, made with fly ash based Portland pozzolana cements in a loaded structure instead of lab 5 studies alone.

6 Study Programme for 5 Years Compressive strength using NDT techniques and extracted cores, every year, Alkalinity of concrete at various depths, measuring ph of powder, Depth of carbonation by phenolphthalein spray test, Electrical Resistivity of concrete Corrosion levels of rebars in concrete, by measuring Half Cell potential. 6

7 Rest Hall Building at Amethi, UP First Building with 50% Fly Ash 7

8 Rest Hall Building at Amethi, UP Single story Unit of RCC framework, having a built up area of 270 sq. m. M-25 grade concrete of 107 m 3 of concrete was used in footings, beams, columns, and slabs of each bay of the structure. The infill walls are made with bricks, masonry mortar and plaster. 8

9 Limitations of HVFA Concrete Limitations 1. All fly ashes can not be used in structural concrete 2. Replacement level depends on fly ash properties 3. Requires a good facilities for testing 4. Requires good quality control at site 5. Requires good curing for minimum days 9

10 Whether all Fly Ashes good for Concrete? Fly ash needs to conform to IS : Availability of processed fly ash. Expertise required to test fly ash Equipment required to test at regular interval Compatibility studies with plasticisers Mixing efficiency at low w/b of ordinary drum mixer, is poor as compared to Pan mixer and RMC s high efficiency twin shaft mixer 10

11 Rest Hall Building at Amethi, UP 11

12 Sketch of Building 12

13 Wire welded with Reinf. Bar 13

14 Wire taken out of concrete 14

15 Roof Beam with 50% Fly Ash 15

16 Roof Beam & Slab 16

17 Inside Building 17

18 Materials Used Cement and fly ash: PPC Cement (27% fly ash) from ACC s Tikaria cement works was used along with fly ash from NTPC s Unchahar Thermal Power Plant. OPC 43 grade cement of ACC s Kymore cement Works was used in one bay. 18

19 Physical Analysis of the Cement & Fly Ash used Properties PPC Cement OPC 43 Grade Fly ash from NTPC Plant Surface Area Sq.m / kg Retention of 45 micron 15% Soundness Le-chatelier expansion 1mm 2mm Auto Clave Expansion 0.11% 0.2% Setting Times Initial - minutes Setting Times Initial - minutes Compressive Strength 155 minutes 135 minutes 200 minutes 195 minutes 7 days 36Mpa 33Mpa More than 85% of the control 28 Days 51Mpa 43Mpa Fly Ah & in PPC 27% Lime Reactivity of Fly Ash 5 MPa 19

20 Chemical Analysis of the Cement & Fly Ash used Properties PPC Cement OPC 43 Grade Fly ash from NTPC Plant Silicon dioxide (SiO 2 ) 65% Aluminium oxide (AI 2 O 3 ) 22.1% Ferric oxide (Fe 2 O 3 ) 3.3% Calcium oxide (CaO) 0.5% Magnesium oxide (MgO) 4.1% 4.1% 04% Total Alkalis as (Na 2 O) 1.2% Sulphur trioxide (SO 3 ) 2.2% 2% 0.5% Chlorides 0.013% 0.01% Loss on ignition 2.4% 1.6% 1.8% Insoluble Residue 22.1% 1.5% 20

21 Grading of Coarse and Fine Aggregate Coarse Aggregate Fine Aggregate Sieve Size, mm 20mm aggregate s Passing, % IS 383 Limits 10mm aggregates Passing, % IS 383 Limits Sieve Size, mm Passing, % IS 383 Limits

22 Expected effect on Concrete properties Fresh Concrete Reduced water demand Reduced bleeding Reduced segregation Reduced w/b 22

23 Expected effect on Concrete properties Hardened Concrete Comparable compressive strength Better Tensile and Flexural strength Similar Modulus of Elasticity Concrete Temperature Reduced Drying shrinkage 23

24 Durability related properties Reduced Chloride Ingress Carbonation Sulphate resistance Alkali Silica reaction Freeze Thaw Abrasion 24

25 Laboratory Experiments FA absorptions, % Fly Ash, kg O.P.Cement, kg W/OPC+FA Slump, mm Total Aggregate Bleeding, ml/cm2 Density, kg/m

26 Compressive Strengths of HVFAC 80 Compressive strength, MPa Age, days 26

27 Flexural Strengths MOR, MPa Age, days 27

28 Water Permeability -Lab Trial Water penetration,mm Age, days 28

29 Chloride Permeability -Lab Trial Change passed, Coulomb Age, days 29

30 Mix details of Rest Hall Batch No. Fly Ash % Used in Bay Cementit ious Material Cement type Cem ent Ext ra Fly ash Sand 10 m m TM - 1 0% OPC TM % PPC TM % PPC TM % PPC TM % PPC m m Wate r W/cm

31 Slump & Strength Batch No. Fly Ash % Used in Bay w/cm Initial slump Comp. Strength MPa 7 day s 28 day s TM - 1 0% TM % TM % TM % TM %

32 Observation of Fresh Concrete 1. Mixing Time: Mixing time of 5 to 6 minutes as compared to three minutes of conventional mix. 2. Cohesive but Sticky Concrete: The concrete mix was found to be cohesive but sticky in nature. 3.Vibrations: The mix was cohesive, self-standing, non- free flowing and sticky. However on vibration, it flowed very nicely and filled the forms evenly. 32

33 Cores Being taken out 33

34 Resistivity of Concrete ( After 6 months) 34

35 Impact Hammer & Compressive Strength of Concrete 35

36 ph of Concrete 1. OPC Concrete PCC Concrete (27% FA) HVFA with 30% FA HVFA with 40% FA HVFA with 50% FA

37 Carbonation of Concrete No Carbonation observed in 6 months 37

38 Lessons Learnt W/CM should be between 0.32 to 0.42 for HVFA Mixing Efficiency of mixer plays an important role in case of low water to binder ratio. Batching plant for uniform mixing. Use of ordinary tilting mixer machine may lead to improper mixing and failures at low water content. To prevent Plastic shrinkage cracks, cover the concrete with plastic sheets Equipment and expertise required for Testing Fly ash for 38 R45, surface area and LOI, at regular interval.

39 Lessons Learnt The variability in type & quality of fly ash and control on doses plays a vital role in imparting strength and durability to the concrete. Generally, it is seen that at smaller sites, quality control is in the hands of operator and such practice may result in to catastrophe, if proper precautions are not taken care. Moreover, the quality of fly ash may not be uniform if it s collected from different fields. Use of processed fly ash is recommended. 39

40 What to do in case of following? If Processed Fly ash as per desired quality is not availability? Or If the testing facility of fly ash as well as expertise in testing is not available? Or If the control in dosing of right quantity is difficult? Then the use of Factory produced PPC would take care of all the problems mentioned above and user would the get desired benefits. The product performance of the PPC Cement containing fly ash is also checked at regular interval and guaranteed as per the IS 40 code 1489 part 1.

41 Improvement in Sphericity Due to grinding of Fly Ash bigger particles turned in to smaller ones. shapes changes to near spherical Rounding of corners 41

42 Effect of ground Fly Ash with clinker for manufacturing PPC 1. Improved Sphericity: The intergrinding creates new reactive surfaces for the fly ash and improves the sphericity of the coarse angular fly ash particle. 2. Improved Particle size distribution: The intergrinding of clinker with Fly ash delivers much better particle size distribution as compared to separately mixed fly ash with OPC. 3. Gypsum Content: Gypsum is known to activate the alumnus phase of fly ash thereby improving pozzolanicity and strength/ durability. The site mixing of gypsum is possible at RMC plants, where good quality control is possible but not at most of the small construction sites 42

43 Principal Conclusions It is possible in our country to have HVFAC structures It is economically required for our country Needs proactive Owners/Architects / Contractors Ideal Conditions - warm weather of our country Take higher strengths into consideration when designing ( or 56 days strength instead of 28 days Strength) Better Durability Preservation of natural resources for future generation. Use of PPC/PSC or addition of fly ash / slag with OPC should be made mandatory expect for few special requirements. 43

44 THANK YOU For Your Kind Attention 44