22-10-2016, 09:13 AM
A Study on the Mechanical Properties of Concrete by Replacing Sand with Waste Foundry Sand
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Abstract-- Conservation of natural resources and preservation of environment is the essence of any development. The problem arising from continuous technological and industrial development is the disposal of waste material. If some of the materials are found suitable in concrete making not only cost of construction can be put down, but also safe disposal of waste materials can be achieved.
Metal foundries use large amounts of sand as part of the metal casting process. Foundries successfully recycle and reuse the sand many times in a foundry. When the sand can no longer be reused in the foundry, it is removed from the foundry and is termed “foundry sand.” Foundry sand production is nearly 6 to 10 million tons annually. Like many waste products, foundry sand has beneficial applications to other industries. Foundry sand consists primarily of silica sand, coated with a thin film of burnt carbon, residual binder ( sea coal, resins) and dust.
Foundry sand can be used in concrete to improve its strength and other durability factors. Foundry Sand can be used as a partial replacement of cement or as a partial replacement of fine aggregates or total replacement of fine aggregate and as supplementary addition to achieve different properties of concrete. In the present study, effect of foundry sand as fine aggregate replacement on the compressive strength, split tensile strength and flexural strength having mix proportions of M30 was investigated. Fine aggregates were replaced with eleven percentages of foundry sand. The percentages of replacements were 0, 10, 20, 30, 40, 60,70,80,90 & 100 % by weight of fine aggregate. Tests were performed for compressive strength, split tensile strength and flexural strength tests for all replacement levels of foundry sand at different curing period (7-days,28 days & 56-days).
INTRODUCTION
Concrete is a composite material composed of gravels or crushed stones (coarse aggregate), sand (fine aggregate) and hydrated cement (binder). It has been in use for over a century in all construction works. A variety of new materials in the field of concrete technology have been developed during the recent past with the ongoing demand of construction industries to meet the functional, strength, economical and durability requirements.
The worldwide consumption of sand as fine aggregate in concrete production is very high and several developing countries have encountered some strain in the supply of natural sand in order to meet the increasing needs of infrastructural development in recent years. To overcome the stress and demand of river sand, researchers and practitioners in the construction industries have identified some alternatives.
Ferrous and non ferrous metal casting industries produce several million tons of byproduct in the world. WFS is major byproduct of metal casting industry and successfully used as a land filling material for many years. But use of waste foundry sand for land filling is becoming a problem due to rapid increase in disposal cost. In an effort to use the WFS in large volume, research has being carried out for its possible large scale utilization in making concrete as partial replacement of fine aggregate.
Foundry industry produces a large amount of by-product material during casting process. The ferrous metal casts in foundry are cast iron and steel, non ferrous metal are aluminum, copper, brass and bronze. Over 70% of the total by-product material consists of sand because moulds consist usually of molding sand, which is easily available, inexpensive, resistance to heat damage and easily bonded with binder and other organic material in mould. Foundry industry use high quality specific size silica sand for their molding and casting process. These WFS is black in color and contain large amount of fines. The typical physical and chemical property of WFS is dependent upon the type of metal being poured, casting process, technology employed, type of furnaces (induction, electric arc and cupola) and type of finishing process (grinding, blast cleaning and coating)
. LITERATURE REVIEW
Rafat Siddique et al. (2008) presented the results of an experimental investigation carried out to evaluate the mechanical properties of concrete mixtures in which fine aggregate (regular sand) was partially replaced with usedfoundry sand (UFS). Fine aggregate was replaced with three percentages (10%, 20%, and 30%) of UFS by weight. Tests were performed for the properties of fresh concrete.Compressive strength, splitting- tensile strength, flexural strength, and modulus of elasticity were determined at 28, 56, 91, and 365 days. Test results indicated a marginal increase in the strength properties of plain concrete by the inclusion of UFS as partial replacement of fine aggregate (sand) and that can be effectively used in making good quality concrete and construction materials.
Gurpreet Singh and Rafat Siddique (2011) carried out an experimental investigation to evaluate the strength and durability properties of concrete mixtures, in which natural sand was partial replaced with (WFS). Natural sand was replaced with five percentage (0%, 5%, 10%, 15%, and 20%) of WFS by weight. Compression test and splitting tensile strength test were carried out to evaluate the strength properties of concrete at the age of 7, 28 and 91 days. Test results indicate a marginal increase in strength properties of plain concrete by inclusion of WFS as a partial replacement of fine aggregate.
H. Merve Basar and Nuran Deveci Aksoy (2012) studied the potential re-use of waste foundry sand (WFS) in readymixed concrete (RMC) production. Regular sand was replaced with five percentages (0%, 10%, 20%, 30%, 40%) of WFS by weight and solidification/stabilization (S/S) process was applied to all concrete mixtures. Three aspects were investigated for the qualification of WFS-based-RMC, i.e., the mechanical, leaching and micro-structural properties. Various tests for the mechanical and physical performance of the solidified products were carried out, and the results indicated that the addition of WFS as partial replacement of sand reduced the strength performance and density and also increased the water absorption ratio of the concrete mixtures. Nevertheless, the concrete having 20% WFS exhibited almost similar results with the control one. The findings of this research suggest that WFS can be effectively utilized in making good quality RMC as a partial replacement of fine aggregates with no adverse mechanical, environmental and micro-structural impacts; however, the partial replacement should not exceed 20%.
Rafat Siddique and El-Hadj Kadri (2011)dealt with the effect of foundry sand (FS) and metakaolin (MK) on the near surface characteristics of concrete. A control concrete having cement content 450 kg/m3 and w/c of 0.45 was designed. Cement was replaced with three percentages (5%, 10%, and 15%) of metakaolin weight, and fine aggregates were replaced with 20% foundry sand. Tests were conducted for initial surface absorption, sorptivity, water absorption and compressive strength at the ages of 35, 56, and 84 days.
I. EXPERIMENTAL INVESTIGATION
A. Materials
Cement: Ordinary Portland cement (Ultra tech cement) of 53 grade confirming to IS: 12269-1987was used. It was tested for its physical properties as per IS 4031 (part II)-1988 and chemical properties as per IS: 12269 at lucid laboratories, Hyderabad.
Aggregate: The size, shape and gradation of the aggregate play an important role in achieving a proper concrete. The flaky and elongated particles will lead to blocking problems in confined zones. The sizes of aggregates will depend upon the size of rebar spacing.
The coarse aggregate chosen for Concrete was typically angular in shape, well graded, and smaller than maximum size suited for conventional concrete; typical conventional concreteshould have a maximum aggregate size of 20mm. Gradation is an important factor in choosing a coarse aggregate. Gap-graded coarse aggregate promotes segregation to a greater degree than the well graded coarse aggregate.
Fine Aggregate: The locally available river sand was used as fine aggregate in the present investigation. The sand was free from clayey matter, salt and organic impurities. The sand was tested for various properties like specific gravity, bulk density etc., and in accordance with IS 2386-1963.
Coarse Aggregate: Machine crushed angular granite metal of 20mm nominal size from the local source was used as coarse aggregate. It was free from impurities such as dust, clay particles and organic matter etc. The physical properties of coarse aggregate were investigated in accordance with IS 2386 -1963.
Waste Foundry Sand: Waste foundry sand was obtained locally from Hinduja Casting Uppal Hyderabad. WFS was used as a partial replacement of fine aggregate (natural river sand). Metal poured in the foundry is gray iron. The sand was tested for various properties like specific gravity, bulk density etc., and in accordance with IS 2386-1963. The fine aggregate was conforming to standard specifications.
Water: Locally available water used for mixing and curing which is potable and is free from injurious amounts of oils, acids, alkalis, salts, sugar, organic materials or other substances that may be deleterious to concrete or steel.
Super Plasticizer: Super plasticizer conforming to IS9103-1979 by trade name Conplast SP 430 manufactured by Fosroc Chemicals (India) limited obtained from United Engineering, Rani Ganj, Hyderabad was used as a water reducing agent to achieve the required workability.
B. Mixes:
The present experiment is carried out to investigate strength properties of concrete mixes of grade M30 in which fine aggregate (river sand) is to be partially replaced with Waste Foundry Sand. Fine aggregate will be replaced with six percentages (0%,10%,15%,20%,25%,30%) of WFS by weight.
C. Mixing, Casting, Curing and Testing:
All the triple blended composites were mixed in the pan mixer. Required number of specimens for various combinations were cast. Continuous curing was maintained upto the age of 7, 28 & 56 days. Mixing, casting, curing and testing were carried out as per the standard specifications.
II. RESULTS AND DISCUSSIONS
The study was conducted to find out the influence of waste foundry sand on strength properties of plain concrete.
The effects of following parameters were studied.
Compressive strength, Split tensile strength and flexural strength at various percentage replacement of fine aggregate with waste foundry sand on some of plain concrete.
i. Workability: The dosage of super plasticizer was kept constant throughout the experimental program at 0.5% of the weight of the binder.
As the waste foundry sand percentage increased in the concrete the workability was reduced. This may be due to the void filling action of the waste foundry sand as it is finer than the fine aggregate, which gives a high cohesion to the mix. Mix with increase in waste foundry sand content tends to become harsh, sticky and stiff.
ii. Compressive Strength: Cube specimens were tested for compression and ultimate compressive strength was determined from failure load measured using compression testing machine. The average value of compressive strength of 3 specimens for each category at the age of 7 days, 28 days and 56 days are tabulated in the Table 1. .The increase in strength of various concrete mixtures over the plain concrete is also tabulated in the Table 1.
There is a considerable improvement in the compressive strength of concrete with inclusion and increase in the percentage of waste foundry sand up to 25%. However on replacement of30% aggregate the concrete showed marginal decrease in strength. It is observed that the compressive strength increased with increasing age of curing. The maximum compressive strength was achieved with 25% replacement of fine aggregate with waste foundry sand.
Fig 1 Compressive Strength of Various Concrete Mixes with
Replacement of Fine Aggregate over Waste Foundry Sand at Different Ages
iii. Split Tensile Strength: Cylinder specimens were tested for splitting tensile strength. The test was carried out according to IS: 5816-1970(10). In this test compressive line loads were applied along a vertical symmetrical plane, which causes splitting of specimen. The average values of 3 specimens for each category at the ages of 28 & 56 days are tabulated in the Table 2. The increase in the splitting tensile strength of various concrete mixtures over plain concrete is also tabulated in Table 2.
There is a considerable improvement in the split tensile strength of concrete with inclusion and increase in the percentage of waste foundry sand up to 20%. However on replacement of 25%&30% aggregate the concrete showed marginal decrease in strength.
It is observed that the split tensile strength increased with increasing age of curing. The maximum strength was achieved with 20% replacement of fine aggregate with waste foundry sand.