Evaluation of durability properties of recycled aggregate concrete incorporating flyash and silica fume

Evaluation of Durability Properties of Recycled Aggregate Concrete Incorporating Flyash And Silica Fume

Prepared by:Parth B. PatelDr. Urmil V. DaveProf. Tejas M. JoshiDepartment of Civil Engineering

Institute of TechnologyNirma University

Ahmedabad

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33rd National Convention of Civil Engineers The Institution of Engineers (India)

Introduction Literature Review Experimental work Results Conclusion References

Flow of Presentation

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Introduction

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Recycled Aggregate

Recycling is the act of processing the used material for use in creating new product.

To reduce the use of natural aggregate we can use recycled aggregate.

Recycled aggregate are comprised of crushed, graded inorganic particles processed from the materials that have been used in the constructions and demolition debris.

Application of Recycled Aggregate

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Concrete kerb Manhole covers Precast toilet blocks Precast walls Concrete planters Granular base Embankment fill Paving block Backfill material

Literature

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Paper Observations

A.M. Knaack, Y.C. Kurama, “Design of Normal Strength Concrete Mixtures with Recycled Concrete aggregates”, Structures Congress, (2011), pp. 3068-3079. [1]

Investigation included three methods for aggregate replacement: direct weight replacement, equivalent mortar replacement, and direct volume replacement. From this investigation it is concluded that direct volume method and equivalent mortar methods gives best and worst workability respectively.

Claudio Javier Zega, Angel Antonio Di Maio. “Recycled Concretes Made with Waste Ready-Mix Concrete as Coarse Aggregate”, Journal of Materials in Civil Engineering, Vol. 23(3), (2011), pp. 281-286.[2]

Investigation included replacement ration as 25%, 50% and 75%. Results shows that when the amount of added water was increased according to the absorption of the recycled aggregate, a increased slump observed and on the contrary, mix in which the amount of mixing water was kept same in all concretes, a slump decrease was noted.

Marco Pepe, Romildo Dias Toledo Filho, Eduardus A.B. Koenders, Enzo Martinelli. “A novel mix design methodology for Recycled Aggregate Concrete”, Construction and Building Materials, Vol. 122, (2016), pp. 362-372.[3]

The experimental programme included different water cement ratio that is 0.4, 0.5 and 0.6; different ratio of NA to RA that is 0%, 50% and 100%; and different moisture condition of aggregates that is dry and saturated. Control concrete was designed for 50 MPA. Results shows that compressive strength decreases as replacement ratio increases, as water cement ratio increases.

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Paper Observations

Kanish Kapoor, S.P. Singh, Bhupinder Singh. “Durability of self-compacting concrete made with Recycled Concrete Aggregates and mineral admixtures”, Construction and Building Materials, Vol. 128, (2016), pp. 67-76.[4]

In this study replacement ratio of NA to RA was kept as 0%, 50% and 100%. Flyash and silicafume were used as 20% and 10% partial replacement of cement respectively. Result shows that the compressive strength across all the curing ages reduced marginally with increasing content of RCA relative to the control mix made with 100% NCA.

Md Shakir Ahmed, H S Vidyadhara. “Experimental study on strength behaviour of recycled aggregate concrete”, International Journal of Engineering Research Technology, Vol. 2, (2013), pp. 76-82.[5]

Investigation included 0%, 20%, 40%, 60% 80% and 100% replacement of NA to RA. RCA is separated from concrete by hammering. Mortar of recycled aggregate is also removed as much as possible. Results shows that split tensile strength, flexural strength and modulus of elasticity of RAC decreases at all the ages as recycled aggregate content increases.

B.M. Vinay Kumar, H. Ananthan, K.V.A. Balaji. ”Experimental studies on utilization of coarse and finer fractions of recycled concrete aggregates in self compacting concrete mixes“, Journal of Building Engineering, Vol. 9, (2017), pp. 100-108.[6]

Effect of acid exposure on recycled aggregate concrete was studied. Natural coarse and fine aggregates were replaced by recycled coarse and fine aggregate at ratio of 20%. RAC was immersed in solution of 3% H2SO4 for 30 days. Results shows that compressive strength after acid attack is decreased by 39.57% as compared to control concrete.

Experimental Work

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Concrete laboratory waste recycled at Kesarjan Building Centre Pvt Ltd, Ahmedabad.

Process of making Recycled Aggregates

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Material Properties

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Sr.No.

Properties Units

Natural Aggregates

RA(Lab. Waste)

20 mm 10 mm 20 mm 10 mm

1 Fineness modulus 7.29 6.03 7.31 5.97

2 Loose density kg/m3 1444 1311 1264 1195

3 Compacted density kg/m3 1671 1584 1446 1407

4 Specific gravity 2.82 2.79 2.44 2.38

5 Water absorption % 1.37 1.27 5.25 6.0

6 Moisture content % 0.9 0.86 1.1 1.0

Recycled aggregate has lower density and higher water absorption as compared to natural aggregate due to attached mortar on aggregates.

Comparison of Properties of aggregate

Mix Design

Grade designation M25

Type of cement OPC 53 grade

Maximum nominal size of aggregate 20 mm

Minimum cement content 300 kg/m3

w/c Ratio 0.5

Workability 100 mm slump

Exposure condition Mild

Method of concreting Non-pumpable

Chemical admixture Super plasticizer

Data to develop a mix design for M25 grade of control concrete.

Specific gravity of cement 3.2

Specific gravity of CA (20mm) 2.81

Specific gravity of CA (10mm) 2.79

Specific gravity of FA 2.75

Specific gravity of chemical admixture 1.15

Fine aggregate zone II

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Mix Design

Material Unit Content

Cement kg/m3 316

CA 20 mm kg/m3 775

CA 10 mm kg/m3 516

Sand kg/m3 728

Water lit/m3 158

Admixture % 0.4

w/c - 0.5

Mix Contents of Control Concrete

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CC RAC50 RAC100Cement % 100 75 75Fly ash % 0 15 15

Silica fume % 0 10 10

Cement kg/m3 316 237 237Fly ash kg/m3 0 47.4 47.4

Silica fume kg/m3 0 31.6 31.6Sand kg/m3 728 789 850

NCA 20mm kg/m3 775 388 0NCA 10mm kg/m3 517 259 0RCA 20mm kg/m3 0 335 671RCA 10mm kg/m3 0 221 441

Water kg/m3 158 187 216Admixture % 0.4 0.4 0.4

Slump mm 105 115 105

Final Mix Design

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Durability Properties Size Specimens 28 Days 56 DaysAcid Attack 150×150×150 Cube 3 3

Sulphate Attack 150×150×150 Cube 3 3

Accelerated carbonation 100×200 Cylinder 3 0

Water Impermeability 150×150×150 Cube 3 0

RCPT100×50 Cylinder 3 0

Sorptivity test

Casting of Specimens for durability properties

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The concrete specimen size 150 mm × 150 mm × 150 mm is casted for evaluating change in compressive strength and change in mass.

The acid resistance of three mixes of concrete is determined by measuring the residual compressive strength and change in mass after acid exposure at 28 and 56 days of time intervals.

After 28 days of water curing, cubes are immersed in 5% sulfuric acid (H2SO4) solution with pH maintained at 3.

Acid attack (IS:4456-1987)

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Mix28 days 56 days

Before After Before After

CC8.51 8.13 8.80 8.238.29 7.96 8.51 7.968.86 8.40 8.67 8.13

Average 8.55 8.16 8.66 8.11

RAC508.18 7.75 8.23 7.598.24 7.81 8.34 7.718.10 7.63 8.15 7.50

Average 8.17 7.73 8.24 7.60

RAC1007.98 7.41 7.89 7.158.01 7.40 7.69 6.987.89 7.33 7.76 7.01

Average 7.96 7.38 7.78 7.05


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From results it can be seen that in mix RAC50 and RAC100 weight loss is higher as compared to CC.

Weight loss is increasing as recycled aggregate content is increasing.

Reason behind this is less bonding between old mortar of recycled aggregate and new mortar.


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MixAvg Comp strength before Comp strength after Avg Comp strength after

28 days 56 days 28 days 56 days 28 days 56 days

CC 32.15 35.41

30.22 27.35

29.81 27.2429.95 26.89

29.26 27.49

RAC50 26.37 31.33

22.92 20.26

22.75 20.1723.85 20.55

21.49 19.69

RAC100 24.07 29.63

20.19 17.25

19.69 16.6119.65 16.21

19.23 16.36


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From results it can be seen that in mix RAC50 and RAC100 compressive strength reduction is higher as compared to CC.

Compressive strength reduction is increasing as recycled aggregate content is increasing.



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The concrete specimen size 150 × 150 × 150 mm is casted for evaluating change in compressive strength and change in mass.

The sulphate resistance of three mixes of concrete is determined by measuring the residual compressive strength and change in mass after sulphate exposure at 28 and 56 days of time intervals.

After 28 days of water curing, cubes are immersed in 5% sodium nitrate (Na2SO4) solution with pH maintained at 8.

Sulphate attack (IS:4456-1987)

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Mix28 days 56 days

Before After Before After

CC8.87 8.89 8.16 8.198.51 8.54 8.36 8.388.93 8.95 8.79 8.82

Average 8.77 8.79 8.44 8.46

RAC508.02 8.07 8.11 8.178.16 8.21 7.92 7.977.98 8.05 8.19 8.26

Average 8.05 8.11 8.07 8.13

RAC1007.96 8.04 7.64 7.737.82 7.90 7.85 7.947.75 7.82 7.77 7.84

Average 7.84 7.92 7.75 7.84


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From results it can be seen that in mix RAC50 and RAC100 little weight gain is noted as compared to CC.

Weight gain is increasing as recycled aggregate content is increasing.

Reason behind this is more absorption of recycled aggregate.


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MixAvg Comp strength before Comp strength after Avg Comp strength after

28 days 56 days 28 days 56 days 28 days 56 days

CC 32.15 35.41

31.16 32.85

31.24 33.3331.69 33.89

30.88 33.26

RAC50 26.37 31.33

24.92 28.51

25.07 28.9725.53 28.82

24.75 29.59

RAC100 24.07 29.63

23.47 26.61

22.86 26.5222.93 26.04

22.19 26.90


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From results it can be seen that in mix RAC50 and RAC100 compressive strength reduction is more as compared to CC.

Compressive strength reduction is increasing as recycled aggregate content is increasing.



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3 cylinders of 100 mm diameter and 200 mm height for each mixes is casted and placed in the carbonation chamber.

Carbon dioxide gas is supplied from a standard industrial cylinder fitted with a regulator. The temperature of the system is controlled by keeping it in a room at a 28°C and a CO2 concentration of 4% with 60% relative humidity.

At completion of test, the specimens is taken out of the chamber and the depth of carbonation is measured by treating the surface of a freshly sliced specimen with a pH indicator that was 1% solution of phenolphthalein in water.

Accelerated Carbonation Test (CEN 12390)

Equipment capacityMax. Temperature : 60°C Humidity range : 40% to 80%Max. CO2 concentration : 4.5%

Test parametersTemperature : 28°C Humidity :60%CO2 concentration :4%


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SplitCylinder

Side

Carbonation depth (mm)Avg.

Carbonationdepth (mm)

Neartop

Nearmiddle

Nearbottom

1 2.99 3.45 3.11

3.223.05 3.56 3.18

2 2.95 3.42 3.163.01 3.53 3.22

Based on the carbonation depth values carbonation coefficient is calculated using following formula :

X = C × √tX = Carbonation depth in mm,C = Carbonation coefficient in mm/day0.5t = exposure time in days


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MixCarbonation

depth(mm)

Rate ofCarbonation(mm/day0.5)

Avg. rate ofCarbonation(mm/day0.5)

CC3.22 1.22

1.313.48 1.323.72 1.41

RAC503.59 1.36

1.443.85 1.464.02 1.52

RAC1004.13 1.56

1.544.25 1.613.82 1.44

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From results it can be seen that mix RAC50 and RAC100 has rate of carbonation more as compared to CC.

Rate of carbonation is increasing as recycled aggregate content is increasing.

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Water Impermeability Test (DIN1048)

The specimens are tested for impermeability test according to German standard DIN-1048 part-5. During this test three concrete specimen are kept as shown in fig. Water pressure is maintained at 5

kg/sq.cm. by compressor attached to the impermeability test setup. After 3 days of exposure to pressurized water the specimen are removed from the test setup. Cubes are then split in to two half and penetration depth is measured.

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Split Cube SideWater penetration depth (mm)

Avg. water penetrationdepth (mm)Near left end Near middle Near right end

1 20.7 22.4 21.820.68

2 20.9 22.2 22.1

Mix Penetration depth (mm) Avg. penetration depth (mm)

CC20.68

20.3619.9520.45

RAC5021.89

21.4121.1321.21

RAC10022.56

23.1223.8422.96

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From results it can be seen that mix RAC50 has 5.16% and RAC100 has 13.56% higher water penetration as compared to control concrete.

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Rapid Chloride Penetration Test (ASTM 1202C)

Specimens of 100 mm diameter and 50 mm length is submerged in the 5% Sodium Chloride solution in a tank, after 28 days of curing period for a 28 days exposure.

Then specimens is tested as per standard procedure of (ASTM C1202-97) for 6 hrs.

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Area under the curve of current versus time duration is the total charge passing through the respective concrete specimens which can be calculate by trapezoidal rule as mentioned below:

Q = 900 (I0 + 2I30 + …. + 2I300 + 2I330 + 2I360)

Where Q = charge passed (Coulombs) I0 = current (Ampere) immediately after voltage is appliedIt = current (Ampere) at t minute after voltage is applied.

Time (min)Current in amp

CC RAC50 RAC1000 0 0 0

30 0.005 0.009 0.01160 0.018 0.022 0.02690 0.028 0.033 0.039120 0.045 0.049 0.059150 0.053 0.064 0.071180 0.066 0.075 0.085210 0.087 0.099 0.109240 0.111 0.12 0.134270 0.1375 0.158 0.171300 0.175 0.186 0.203330 0.2125 0.232 0.255360 0.25 0.265 0.286

Cumulative current 2.2524 2.49 2.739Charge passed 2027.16 2241 2465.1

Chl Ion Permeability Moderate Moderate Moderate

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Control concrete current readings are lower as compared to recycled aggregate concrete. RAC50 and RAC100 concrete mixes showed similar current values at starting.

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Figure shows the percentage increase in total charge passed through specimen with respect to control concrete. It can be observed that mixes RAC50 and RAC100 has higher chloride ion penetrability compared to control concrete.

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Sorptivity (ASTM 1585) This test method is used to determine the rate of absorption (sorptivity) of water by cement

concrete by measuring the increase in mass of specimen resulting from absorption of water as a function of time when only one surface of the specimen is exposed to water.

The specimen required for the test consist of a disc of diameter 100mm 6mm and height 50mm 3mm.

The weight of specimen are measured at time (t) : 1 min, 5 min, 10 min, 20 min, 30 min, 1 hour, every hours up to 6 hours, every day up to 3 days, 24 hours apart from 4 to 6 days and one measurement between 7 to 9 days.

From the change in mass with time. Water absorption and sorptivity is calculated.

Water Absorption I = Mt / (a b) where a = exposed surface area,

d = density of water (g/ mm3) From the water absorption, the sorptivity (S) can be calculated by equation given in ASTM

C 1585,I = S + b

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InitialSorptivity

0.0082 mm/√s

SecondarySorptivity

0.0026 mm/√s

Control ConcreteSorptivity (ASTM 1585)

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InitialSorptivity

0.0093 mm/√s

SecondarySorptivity

0.003 mm/√s

RAC50Sorptivity (ASTM 1585)

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InitialSorptivity

0.0101 mm/√s

SecondarySorptivity

0.0033 mm/√s

RAC100Sorptivity (ASTM 1585)

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Results shows that the RAC50 and RAC100 has higher sorptivity as compared to control concrete.

Sorptivity (ASTM 1585)

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Conclusions From investigation it can be concluded that recycled aggregate has higher water absorption as compared

to natural aggregate which need to be consider in a mix design.

Durability properties like acid attack, sulphate attack, accelerated carbonation, water impermeability, rapid chloride penetration and sorptivity decreases as recycled aggregate content increases.

1. A.M. Knaack, Y.C. Kurama, “Design of Normal Strength Concrete Mixtures with Recycled Concrete Aggregates”, Structures Congress, (2011), pp. 3068-3079.

2. Claudio Javier Zega, Angel Antonio Di Maio. “Recycled Concretes Made with Waste Ready-Mix Concrete as Coarse Aggregate”, Journal of Materials in Civil Engineering, Vol. 23(3), (2011), pp. 281-286.

3. Marco Pepe, Romildo Dias Toledo Filho, Eduardus A.B. Koenders, Enzo Martinelli. “A novel mix design methodology for Recycled Aggregate Concrete”, Construction and Building Materials, Vol. 122, (2016), pp. 362-372.

4. Kanish Kapoor, S.P. Singh, Bhupinder Singh. “Durability of self-compacting concrete made with Recycled Concrete Aggregates and mineral admixtures”, Construction and Building Materials, Vol. 128, (2016), pp. 67-76.

5. Md Shakir Ahmed, H S Vidyadhara. “Experimental study on strength behaviour of recycled aggregate concrete”, International Journal of Engineering Research Technology, Vol. 2, (2013), pp. 76-82.

6. B.M. Vinay Kumar, H. Ananthan, K.V.A. Balaji. ”Experimental studies on utilization of coarse and finer fractions of recycled concrete aggregates in self compacting concrete mixes“, Journal of Building Engineering, Vol. 9, (2017), pp. 100-108.

7. Navdeep Singh, S.P. Singh, ”Carbonation and electrical resistance of self compacting concrete made with recycled concrete aggregates and metakaolin“, Construction and Building Materials, vol. 121, (2016), pp. 400-409.

8. Shi-cong Kou, Chi-sun Poon, Francisco Agrela, ”Comparisons of natural and recycled aggregate concretes prepared with the addition of different mineral admixtures“, Cement Concrete Composites, Vol. 33, (2011), pp. 788-795.

9. IS: 10262-2009, ”Concrete Mix Proportioning - Guidelines“, Bureau of Indian Standards”, New Delhi.10. IS: 4456-1987, “Methods of Test for Chemical Resistant Mortars”, Bureau of Indian Standards, New Delhi.11. CEN 12390 (Part-12)-2010, “Euro Standard for Determination of the Potential Carbonation Resistance of Concrete.12. DIN 1048 (Part-5)-1991, ”German Standard for Determination of Permeability of Concrete“.: Testing hardened concrete - Part 12:

Determination of the potential carbonation resistance of concrete: Accelerated carbonation method13. ASTM 1202C-1997 Standard Test Method for Electrical Indication of Concrete’s Ability to Resist Chloride Ion Penetration.

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References

Thank you

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