Durability Study of Concrete Using Foundry Waste Sand
Published on Sep 03, 2020
In India nowadays metal casting industries dump lot of foundry sand as a waste, which is creating dangerous environmental related problems, on the other hand we are facing a problem of sand scarcity in construction. With the aim of resolving these two problems, we have attempted an effective strength and durability performance study on concrete with 100% replacement of foundry sand.
Pathariya Saraswati C, Ranajay krushnaK studied the compressive strength of the concrete by replacement of the local sand by foundry waste sand by 0%, 20%, 40% and 60% and they found that for 60% replacement of local sand by waste foundry sand they had obtained maximum compressive strength values.
Rafat Siddique, Ravinder Kaur Sindhu, carried out the test for studying the resistance of the concrete for the sulphate attack and they had observed that for the mix containing 10% FWS an increase in strength as compared to the control mix even after immersing the cubes in magnesium sulphate solution. However, for both 15% and 20% replacement levels, a decrease in strength is observed when compared to the standard 28 days strength of the related concrete mix, at all ages after immersion in the sulphate solution.
Alok Khanduri under the guidance of Rafat Siddique studied the effect of foundry sand on porosity and Resulted that Porosity of the mortar decreases with increase in sand replacements with different replacement levels of foundry sand. The mortar with FWS than 10% exhibited reductions in water absorption and voids ratio.
G.GaneshPrabhu, Jin Wook Bang, Byung Jae Lee, Jung Hwan Hyun,Yun Yong Kim studied the reuse of Foundry sand as a substitute for natural sand in concrete production was evaluated based on the mechanical and durability properties of the resulting concrete. Based on the extensive tests carried out on the six mixtures, the following conclusion has been made. The chemical analysis of Foundry sand indicated that Foundry sand can be a very suitable material for concrete production. However, the fineness and high water absorption of FWS increases the water demand of the concrete by water absorption, decreasing the workability of the concrete, although the effect was profound beyond the substitution rate of 30%.
From the above discussion it is clear that many of the researchers have determined strength parameters at different replacement levels of foundry waste sand. Durability study is very scanty in the available literature. Keeping this point in mind following objectives has been defined below.
Keywords : Foundry waste sand (Burnt black sand and Weathered sand), Porosity and Water absorption, Permeability, Compressive strength, Acid attack
1. Determination of compressive strength of concrete for 28days curing period and 56days (i.e., 28days for curing and other 28 days exposed to atmosphere).
2. Effect of accelerated curing on compressive strength (440C, 550C).
3. Determination of porosity and water absorption.
4. Permeability test.
5. Determination of strength after heating and cooling.
6. Determination of strength after alternate wetting and drying.
7. Acid attack test (sulphate attack test).
Materials which are used to conduct the above tests are Cement (OPC), Locally available sand, Foundry waste sand, Basalt Aggregates and Water
Cube specimen of size 15cm×15cm×15cm were cast using the mix proportion given in Table1 as per IS:516-1959.
Table1: Finalized mix proportions for locally available sand, Weathered and Burnt Black sand for M20 grade concrete.
The cubes were de-moulded after 24 hours of casting. The cubes were kept for curing
under water immersion at laboratory temperature 27±2˚C. Water is being changed at regular intervals.
1. Compressive strength test:
The compressive strength test was carried out using IS: 516-1979. At the end of curing period i.e., 28 days and at 56 days (exposed to environment for a period of 28 days after 28 days curing period), compressive strength test was conducted.
2. Accelerated curing method (warm water method):
As per IS 9013-1978 the specimens after casting were kept for drying for a period of 2 and ½ hours and then sealed, after sealing they are kept in accelerated curing tank at a temperature of 550C for a period of 20± ½ hours, after this period they are taken out and wiped and later checked for its compressive strength.
The same procedure is repeated for 440C (Prevailing temperature in our city).
3. Water absorption test:
The test was carried out as per ASTM C-640.
% water absorption=[(ww-Dw)/Dw]x100
Where, Ww=wet weight of the cube,
Dw=dry weight of the cube.
The specimens are cast according to the mix design and cured for 28 days in curing tank. Then it is removed from the curing tank and surface is wiped, then the weight is noted down. Then the samples were oven dried for 24 hours at 65°C temperature and weighed again. Again it is kept in oven for next 24 hours and again the weight is noted down. This process is continued till the weight remains constant. The difference in the weight of the sample gives the porosity.
5. Permeability Test:
The test was carried out according to German Standard DIN 1048 on concrete specimens of size 150x150x150 mm ,and the depth of penetration in specimen is noted down by breaking them equally under UTM.
6. Alternate heating and cooling:
The specimens are cast and cured for 28 days, after curing the specimens are subjected to heating and cooling for a period of 20days (20cycles) to check the durability. The specimens are heated at normal atmospheric temperature in day time and cooled during the night time. This process is continued for 20 days and after that strength of the specimens is checked.
7. Alternate wetting and drying:
The specimens are cast and cured for 28 days, after curing the specimens are subjected to alternate wetting and drying for a period of 20 days to check the durability. The specimens are kept for wetting in curing tank for 1 day and next day it is allowed to dry, again the procedure is repeated, after 20 days cycle the strength of specimens are tested to check the effect of alternate heating and cooling on concrete.
8. Acid attack test:
Sulphate attack test was carried out as per Leonardo journal of science ISSN 1583-0233. Magnesium sulphate solution of 50g/l is used to evaluate sulphate resistance of concrete.
Corrosion of reinforcement embedded in RCC member using foundry waste sand is to be carried out.
1. From the result of sieve analysis of burnt black sand and weathered sand, both sand belongs to ZoneIII and locally available sand belongs to ZoneII. Foundry waste sand has lower specific gravity compared to locally available sand.
2. Water absorption of weathered sand is more as compared to burnt black sand and locally available sand hence workability is reduced.
3. Higher workability is recorded for concrete containing locally available sand compared to concrete containing weathered sand and burnt black sand.
4. Porosity of concrete decreases in the order of concrete containing weathered sand (17.9%), concrete containing burnt black sand (16%) and control mix (13.6%). Similarly decreasing trend is observed for water absorption i.e., concrete containing weathered sand (2.2%), concrete containing burnt black sand (1.9%) and control mix (1.6%).
5. Concrete containing weathered sand and concrete containing burnt black sand has resulted in lower strength at 28 days of curing i.e., 27.76N/mm2 and 28.05 N/mm2 respectively compared to control mix of strength 42.292N/mm2 , this is due to higher water absorption of foundry waste sand. At 56 days age of concrete (moist cured for 28 days and exposed to ambient temperature for 28 days) control concrete (40N/mm2) and concrete containing burnt black sand (39.385N/mm2) has recorded nearly the same strength but concrete containing weathered sand has recorded lower strength (31.68N/mm2). All the three concrete for both the ages have satisfied the requirement of M20 grade concrete.
6. To study the effect of heat curing warm water method (550C) is used, compressive strength of control mix and concrete containing burnt black sand registered nearly the same strength i.e., 42.292N/mm2 and 40.380N/mm2 respectively but concrete containing weathered has recorded lower strength of 33.94N/mm2 compared to control mix, this is due to higher water absorption of weathered sand. This behaviour is same as that of the behaviour observed in 5th conclusion at 28 days curing.
7. Permeability is measured in terms of depth of penetration of water in concrete, concrete containing weathered sand, control mix and concrete containing burnt black sand recorded depth of penetration 4.38cm, 2.86cm, 1.85cm respectively. Concrete containing weathered sand is more permeable which is clear from higher porosity result in 4th conclusion and lower compressive strength in 5th conclusion.
8. Heating and cooling effect has not much influence on concrete using locally available sand and burnt black sand, but increase in strength was observed for concrete containing weathered sand (17.31%) compared to control mix, this is due to enhanced hydration.
9. Effect of alternate wetting and drying is marginal for concrete using locally available sand and weathered sand. But concrete using black sand has resulted in higher strength (27.47%), it is due to enhanced hydration.
10. Decrease in strength is observed due to sulphate attack on concrete using locally available sand and weathered sand but for concrete containing burnt black sand increase in strength was observed (25.19%), it may be due to formation of ettringite (tri calcium alumina sulphate).
Project Done By Ms. Anuradha B B, Ms. Devika Baba, Mr. M. Rahul, Mr. Manjunath