CODEN (USA): IJCRGG, ISSN: 0974-4290, ISSN(Online):2455-9555 Vol.10 No.6, pp 898-904, 2017
M. Achyutha Kumar Reddy3 & V. Ranga Rao4
Abstract : The main aim of this study is to search an alternative of cement and to present an experimental study on the durability properties of concrete with the replacement of cement with calcium bentonite. In this paper, six samples of the same grade at desired bentonite percentage of 10, 15, 20, 25 and 30 in comparison with the control mix (CM). The durability properties were studied through sulfate attack (H2SO4) and alkali attack (NaOH). The lower compressive strengths were observed for the bentonite mixes, after 28 days cured in water. The weight losses were observed in both sulfate and alkali attacks. The random variation of compressive strengths of the samples was observed, after 28 days of water curing and 30 days cured with H2SO4 and NaOH. The increase in strength of bentonite mixes is due to the increase in age and not due to the durability attacks. Key words: Bentonite, Durability, Sulfate attack, Alkali attack, Compressive strength.
The world's yearly creation of concrete of 1.6 billion tons discharges 7% of the worldwide stacking of carbon dioxide into the air and it is likewise the most vitality escalated material of development which is in charge of the emanation of extensive measure of greenhouse gasses into the environment [1]. So we are in the requirement for the look of an optional material for cement. Bentonite is exceedingly plastic mud containing around 85% earth minerals and montmorillonite. Two sorts of bentonite uncommonly swelling sort or sodium bentonite and non-swelling sort or calcium bentonite. In our present work, calcium bentonite was utilized which is otherwise called
[2] [3]
more fuller’s earth . Bentonite is accessible bounteously in nature and it obeys pozzolanic properties . The construction industry which utilizes around 12.6 billion tons of crude materials consistently is the largest user of characteristic assets on the planet and it antagonistically impacts the ecology of the planet [4]. Along these lines, the improvement of durability of the concrete structures is essential. The Durability properties were investigated through chemical attacks.
K. Sreenivasa Sudheer et al /International Journal of ChemTech Research, 2017,10(6): 898-904.
In this experimental work, OPC 43 grade cement was utilized which is having a specific gravity 3.15[5] ,
[6][7]
standard consistency 34, initial setting time 43 minutes and final setting time 123 minutes.fine aggregate
[8][9]
confirming to zone-IIIand specific gravity 2.60was used. The coarse aggregate of size 20mm and 10mm and specific gravity of 2.64[9] were used. Calcium Bentonite having a specific gravity 2.38, Standard consistency 75,
[12-15]
and Initial setting time 68 minutes and Final setting time 190 minutes.
Taking after IS: 10262-2009[10], our mix design was gone for ordinary Portland cement concrete having 28 days compressive strength of 30Mpa for control mix. For control mix having a compressive strength of 30Mpa, the mix proportion arranged is organized in Table 1. Other concrete mixes were prepared by replacing cement by weight with a carved measure of Bentonite i.e., 10, 15, 20, 25, 30 %. Different constituents were kept steady.
Table 1 Mix proportion
Mix Type | Bentonite (%) | Cement (kg/m3) | Bentonite (kg/m3) | Fine Agg. (kg/m3) | Coarse Agg. (kg/m3) | W/C | Proportion (C:FA:CA) |
---|---|---|---|---|---|---|---|
CM | 0 | 427.00 | 0.00 | 743.60 | 960.96 | 0.5 | 1:1.74:2.25 |
B-10 | 10 | 384.30 | 42.70 | 740.74 | 957.26 | 0.5 | 1:1.73:2.24 |
B-15 | 15 | 362.95 | 64.05 | 736.73 | 952.08 | 0.5 | 1:1.72:2.22 |
B-20 | 20 | 341.60 | 85.40 | 735.59 | 950.75 | 0.5 | 1:1.73:2.23 |
B-25 | 25 | 320.25 | 106.75 | 733.18 | 947.50 | 0.5 | 1:1.71:2.21 |
B-30 | 30 | 298.90 | 128.10 | 730.67 | 944.25 | 0.5 | 1:1.711:2.211 |
To assess the impact on compressive strength cube specimens were made and cured as shown in Fig1. Standard sized cube specimens of 15 X 15 X 15 cm according to IS: 516-1959[11] were tested for compressive strength utilizing the compressive testing machine were shown in Fig2. The results of compressive strength were tabulated in Table 2.
Table 2. Compressive strength results in MPa
S.No | Mix type | Compressive strength in MPa (28 days) |
---|---|---|
1 | CM | 38.804 |
2 | B-10 | 27.032 |
3 | B-15 | 25.724 |
4 | B-20 | 25.942 |
5 | B-25 | 17.004 |
6 | B-30 | 15.260 |
K. Sreenivasa Sudheer et al /International Journal of ChemTech Research, 2017,10(6): 898-904.
Figure 1 Cubes after 28 days of water curing
Figure 2 Cubes testing for compressive strength
For acid attack and alkali attack test concrete cubes of size 15X15X15 cm are prepared for various percentages of Bentonite. The specimens are then weighed and immersed in 2% Sulfuric acid[16] (H2SO4) shown in Fig4 and 2% Sodium Hydroxide (NaOH) solution of 10 Molar for 30 days shown in Fig3 after 28 days of water curing. After 30 days of immersing in acid and alkali solution, the weights and compressive strength of the cubes were taken and the failure samples were shown in Fig5. The physical properties of the chemicals were tabulated in Table 3. The changes in compressive strength were tabulated in Table 4 and Table 6.
Table 3 Physical Properties of Chemicals Used
S. No | Property | H2SO4 | NaOH |
1 | IUPAC ID | Sulfuric acid | Sodium oxidanide, Sodium Hydroxide |
2 | Molar mass | 98.079g/mol | 39.997g/mol |
3 | Density | 1.84g/cm3 | 2.13g/cm3 |
4 | Boiling Point | 337◦C | 1388◦C |
5 | Melting Point | 10◦C | 318◦C |
K. Sreenivasa Sudheer et al /International Journal of ChemTech Research, 2017,10(6): 898-904.
Table 4 Change in Compressive Strength With 2% H2SO4
Mix type | Compressive strength at 28 days (MPa) | Compressive strength after immersion in acid for 30 days(MPa) |
---|---|---|
CM | 38.804 | 20.050 |
B-10 | 27.032 | 20.710 |
B-15 | 25.724 | 29.860 |
B-20 | 25.942 | 23.106 |
B-25 | 17.004 | 25.280 |
B-30 | 15.260 | 16.347 |
Table 5 Change in Weight of bentonite mixes With 2% H2SO4 attack
Mix type | Weight of specimens before immersion(grams) | Weight of specimens after immersion (grams) |
---|---|---|
CM | 8035 | 7890 |
B-10 | 8120 | 7815 |
B-15 | 8140 | 8095 |
B-20 | 8020 | 7965 |
B-25 | 8015 | 7955 |
B-30 | 8035 | 8015 |
Table 6 Change in Compressive Strength with 2% NaOH
Mix type | Compressive strength at 28 days (MPa) | Compressive strength after immersion in alkali for 30 days (MPa) |
---|---|---|
CM | 38.804 | 34.008 |
B-10 | 27.032 | 30.080 |
B-15 | 25.724 | 34.440 |
B-20 | 25.942 | 22.450 |
B-25 | 17.004 | 18.965 |
B-30 | 15.260 | 18.090 |
Table 7 Change in Weight With 2% NaOH
Mix type | Weight of specimens before immersion(grams) | Weight of specimens after immersion(grams) |
---|---|---|
CM | 8230 | 8105 |
B-10 | 8180 | 8105 |
B-15 | 8190 | 8025 |
B-20 | 8025 | 7940 |
B-25 | 8035 | 7860 |
B-30 | 8120 | 7965 |
The compressive strength of the mixes is taken for 28 days of water curing. The comparison between the compressive strength of 28 days of water curing and compressive strength of 30 days of sulfate attack and alkali attack after 28 days of water curing. The compressive strength of CM in sulfate attack is 20.050 MPa and in alkali attack is 34.008 MPa, 48.33% and 12.35% are decreased than CM of 28 days of water curing. B-10 shown 20.710 MPa in sulfate attack, 23.38% decrease than B-10 of 28 days of water curing and also it showed 30.080 MPa in alkali attack, 11.27% increase than B-10 of water curing. B-15 shown 29.860 MPa and 34.440 MPa in sulfate attack and alkali attack, 16.07% and 33.88% increase than B-15 of water curing. B-20 shown 23.106 MPa and
22.420 MPa in sulfate and alkali attack, 10.93% and 13.46% decrease than B-20 of water curing. B-25 shown
K. Sreenivasa Sudheer et al /International Journal of ChemTech Research, 2017,10(6): 898-904.
25.280 MPa and 18.965 MPa in sulfate and alkali attack, 48.67% and 11.53% increase than B-25 of water curing. B-30 shown 16.347 MPa and 18.090 MPa in sulfate and alkali attack, 7.123% and 18.54% increase than B-30 of water curing. The compressive strengths variations were shown in Fig 6.
The weights are taken after 28 days of water curing and the weights are taken after 30 days of sulfate and alkali attack and the following comparison are done. CM showed 7890 grams and 8105 grams in sulfate attack and alkali attack, 1.8% and 1.5 % decrease than CM of 28 days of water curing. B-10 shown 7815 grams and 8105 grams in sulfate and alkali attack, 3.7% and 0.91% decrease than B-10 of water curing. B-15 shown 8095 grams and 8025 grams in sulfate attack and alkali attack, 0.55% and 2.01% decrease than B-15 of water curing. B-20 shown 7695 grams 7940 grams in sulfate and alkali attack, 4.05% and 1.05% decrease than B-20 of water curing. B -25 shown 7955 grams and 7860 grams in sulfate and alkali attack, 0.74% and 2.17% decrease than B25 of water curing. B-30 shown 8015 grams and 7965 grams in sulfate and alkali attack, 0.24% and 1.90% decreased than B-30 of water curing. The changes in weights were tabulated in Table 5 and Table 7.
Figure 3 Cubes immersed in alkali solution
Figure 4 Cubes immersed in acid solution
K. Sreenivasa Sudheer et al /International Journal of ChemTech Research, 2017,10(6): 898-904.
Figure 5 Failure Samples after durability attacks
Figure 6 Graph showing variations in compressive strengths after water curing, sulfate attack, alkali attack
The following conclusion are drawn after the finish of the experimental work, the compressive strength of bentonite mixes were reduced at the age of 28 days in comparison to the CM, B-10 shown optimum among all blended mixes. A little bit Weight loss was observed in alkali, high % of weight was observed in acid attack for all mixes, B-20 shown 4.05%. In sulfate attack, the compressive strength is increased in B-15, B-25, and B-30 concrete mixes and decreased in CM, B-10, and B-20 concrete mixes. In alkali attack the compressive strength is increased in B-10, B-15, B-25, B-30 concrete mixes and decreased in CM, B-20 concrete mixes. The control mix does not increase its compressive strength but Bentonite mixes increased their strength due to increase in age. The increase in the compressive strength is because of the increase in age but not due to the sulfate and alkali attacks.
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