In this techno-modern world, concrete is a major composite used to develop the infrastructure like bridges, dams, commercial and residential structures. In general, concrete comprises 70 percentage of aggregate fillers. Whereas, fine aggregate occupies 50% of aggregate volume in concrete. In Tamil Nadu, nearly 10 million Cubic feet sand is required per day, where the cost for 1cubic feet is 143 Indian rupees. Also it leads to the destruction of natural resources from river sand and reduces the ground water level around river belt region. In order to preserve the natural resources in its pristine form, an alternate for river sand
Industrial by- products like Foundry sand (FS) and Steel slag are already supplanted for sand. FeCr slag from ferrochrome ore extraction industries can be grained to the required size and to fall on zone condition for concrete. India is the second largest steel producer in the world next to China. In the production of stainless steel, ferrochrome plays a paramount role. While extracting ferrochrome from its ore we get almost 50% FeCr slag. As per International Chromium Development Association (ICDA) activity report 2017, nearly 13.2 Million tonnes (Mt) of FeCr slag are produced from 13 major chromium production countries. Some of the leading producers are China, South Africa, Kazakhstan and India. India lets nearly 1.5 to 2 Mt per year. FeCr slag is liquid in state and it is allowed to cool for a few days in wasteland and it is dumped into the larger part of eastern parts of India like Odisha and Andhra Pradesh. It occupies large dumped areas and creates a lot of nuisance for the society, these waste materials can be used in concrete instead of fine aggregate.
There are a number of studies carried out with this slag as coarse aggregate; on the contrary, very few researches carried out with FeCr slag as fine aggregate. Studies on Crushed Stone sand or Msand is gaining momentum throughout Tamil Nadu after banning River sand consumption for construction. One cubic feet of Msand is around 65 Indian rupees. Moreover, TNPWD (Tamil Nadu Public Work Department) approved some plants to grain the boulders and rocks as fine aggregate which follows IS 383 2016. There are two different varieties of Msand based on the use. They are Msand for concrete and Msand for plastering. Msand for concrete is slightly coarser in texture; whereas, Msand for plastering is finer. Numerous Indian authors experimented and analysed the Msand for concrete based on various physicochemical characters like geographical condition of stone, shape, texture, particle size, chemical composition and other ingredients in the mix.
Existing researchers have discussed the usage of Msand with different percentage of replacements for a particular grade of concrete. The comprehensive view of Msand in different grades of concrete are not yet deliberated so far.
Mortar study was conducted with FeCr slag. It retained the flowability of mix and it has high thermal conductivity due to MgO and Cr2O3 content in slag. .Hence FeCr slag leads to reduction of thermal stress and temperature gradients. Three dimensional surface topography of FeCr slag shows sharp needle than river sand which leads to the brittle nature
Reference | Study area | MC | SG | Z | TB | RP | w/c | WA | FM | Analysis |
---|---|---|---|---|---|---|---|---|---|---|
1 | Mortar | River Sand | 2.85 | II | OPC | 0%, 5%, 10%, 15% and 20% | 0.485 | 0.63 | - | Mechanical strength, Micro structural, drying shrinkage, Thermal property, and XRD. |
2 | Concrete | River Sand | 2.72 | I | OPC, PPC and PSC | 0%, 20%, 40%, 60%, 80% and 100% | 0.5 | 0.42 | 4.8 | Compression, TCLP, SQD and BMD. |
3 | Concrete – M30 | River Sand | 2.52 | II | PSC | 0%,10%, 20%, 30%, 40% and 50% | 0.42 | 1.01 | 2.33 | Mechanical strength, UPV, MOE,RCPT, optical microscopic study acid and sulphate resistant |
4 | Concrete – M30 | River Sand | 2.38 | II | OPC | 0%,10%, 20%, 30% and 40 | 0.43 | - | 2.38 | Mechanical strength at water, acid and base curing. |
5 | Concrete – M30 | Natural Sand | 2.52 | II | PSC | 0%,10%, 20%, 30%, 40% and 50% | 0.42 | 10.89 | 2.69 | Slump Loss, Mechanical strength, water absorption, SAI, TCLP, SEM |
6 | Concrete – M30 | River Sand | 2.52 | II | PSC | 0%,10%, 20%, 30%, 40% and 50% | 0.42 | 10.89 | 2.69 | Review |
7 | Mortar | River Sand | 2.85 | II | OPC with Nanometakaolin | 50% FeCr | 0.485 | - | - | Mechanical strength, Micro structural, Sorptivity, Drying shrinkage, Thermal property, and XRD. |
8 | Concrete – M30 | River Sand | 2.38 | II | OPC | 0%,10%, 20%, 30% and 40 | 0.43 | - | 2.38 | Mechanical strength at water, acid and base curing. |
9 | Mortar | River Sand | 2.65 | II | OPC | 0%, 20%, 40%, 60%, 80% and 100% | 0.5,0.6,0.625,0.650.7, 0.8,and 0.825 | 1.01 | 2.7 | Percentage of Flow,SEM, Compressive strength and Modulus of Elasticity |
10 | UHSC | River Sand | - | OPC with silica fume, fly ash and GGBS | 100% of sandstone, limestone and granite as Manufactured sand | 0.17 to 0.19 | - | - | Slump, compressive strength, SEM and Elemental mapping. | |
11 | Concrete - M60 | River Sand | - | OPC with Fly ash | 100% of various Lithology manufactured sand | 0.34 | - | 2.26 to 3.69 | Slump, compressive strength, XRD, surface roughness. | |
12 | HPC | River Sand | 2.56 | II | OPC with Silica fume | 0%,30%,50% and 70% | 0.32 | - | 3.10 | Compressive strength and flexural strength |
13 | Concrete – M20 | River Sand | 2.84 | II | OPC | 0%, 20%, 40%, 60%, 80% and 100% | 0.45 | 5.6 | 2.84 | Fresh, compressive strength and splitting tensile strength |
14 | Mortar | River Sand | 2.84 | II | OPC - 53 | 0%, 50% and 100% | 0.50 and 0.55 | 5.6 | 2.84 | Compressive strength for 1:2, 1:3 and 1:6 |
15 | Concrete | River Sand | 2.787 | OPC- 53 | 0%, 30%, 50%, 70% and 100% | 0.58 | 0.60 | 2.90 | Slump, compressive strength | |
16 | Concrete – M20 & M30 | River Sand | 2.52 | II | OPC - 43 | 0%, 20%, 40%, 60% and 100% | 0.5 & 0.45 | 2.26 | 2.75 | Slump, compaction factor, Vee-bee, Compressive strength, splitting tension strength, flexural strength & acid treatment |
17 | Concrete –M30 | River Sand | 2.59 | - | PPC | 0%, 30%, 40%, 60% and 80% | 0.5 & 0.48 | - | 2.52 | Compressive strength and splitting tensile strength |
18 | Concrete – M20 | River Sand | 2.5 | II | OPC - 43 | 0%, 5%, 10%, 15%, 20%, and 25% | 0.53 | 0.26 | 2.75 | Compressive strength and splitting tensile strength |
19 | Concrete – M60 | River Sand | 2.65 | II | OPC - 53 | 0%,20%, 40%, 60%, 80% and 100% | 0.32 | - | 2.86 | Compressive strength and structural behaviour of column |
20 | Concrete – M40 | - | 2.57 | - | OPC and GPC | 100% | 0.35 | - | - | Compressive strength, acid attack, sulphate attack and chloride attack. |
21 | Concrete – M60 | River Sand | 2.56 | II | OPC -53 & 7.5% Silica fume | 0%,10%, 20%, 30%, 40, 50%, 60% and 70% | 0.32 | - | 3.10 | Compressive strength, splitting tension strength and flexural strength |
22 | Concrete – M60 | River Sand | 2.65 | II | OPC -53 & Silica fume | 0%,20%, 40%, 60%, 80% and 100% | 0.32 | - | 2.86 | Compressive strength, splitting tension strength,SEM, EDS sorptivity and RCPT |
23 | Concrete –M30 | River Sand | 2.68 | - | OPC – 43 & 1% Steel fiber | 0%, 30%, 40%, 50% and 60% | - | 7 | 5.2 | Compressive strength, splitting tension strength and flexural strength |
24 | Concrete – M60 | River Sand | 2.78 | II | OPC -53, Fly ash, Silica fume, Glass fibre, Polypropylene fibre &Recron 3s fibre | 100% | 0.3 | - | - | Compressive strength, splitting tension strength, flexural strength and RCPT |
25 | Concrete – M40 | River Sand | 2.73 | - | OPC -53, Fly ash and Silica fume | 0%, 50% and 100% | 0.28 | - | 4.66 | Slump, and compressive strength |
26 | Concrete – M20 & M30 | River Sand | 2.57 | II | OPC – 43 | 0%, 20%, 40%, 60% , 80% and 100% | 0.5 and 0.45 | 2.26 | 2.75 | Slump, compressive strength, splitting tension strength, flexural strength & acid treatment |
27 | Concrete – M60 | River Sand | - | II | OPC -53, Fly ash and Silica fume | 100% | - | - | 2.4 to 3.1 | Slump, compressive strength and splitting tensile strength |
28 | SCC-M35 | - | 2.65 | - | OPC -53 | 100% | 0.54 | - | 3.12 | Sulphate and Chloride immersed strength |
Note: MC - Materials used for Comparison, SG - Specific Gravity of FeCr or Msand, Z - Zone of grained sand, TB - Types of Binder, RP - Replacement Percentage of FeCr slag or Msand, w/c - Water Cement ratio, WA – Water Absorption(%) and FM – Finess Modulus.
OPC (Ordinary Portland Cement) with 7.5% weight of silica fume is studied with 0% to 70% replacement of virgin sand with Msand. Compressive strength, split tensile strength and flexural strength increases in a consistent manner up to 60% replacement in HPC cluster
Where,
V1 is the reference strength
V2 is the obtained strength
Compressive strength of FeCr slag in concrete are represented in a graphical format
In
By replacing FeCr slag (10%, 20%, 30%, 40% & 50%) with river sand. Experimental results of splitting tension showed a decreased in percentage difference of 1.96%, 6%, 0.55%, 5.42% and 13.33%respectively than 100% of river sand strength
A particular work by replacing 20%, 40% and 60% of Msand by fine aggregate. Moreover, the splitting tensile strength behaviours are better than control mix. There is a 9.02%, 9.92% and 10.82% increase in percentage difference, respectively
Flexural study by replacing FeCrslag (10%, 20%, 30%, 40% & 50%) instead of river sand. Although, there is a decrease in the percentage difference by 3.05%, 6.20%, 12.08, 8.52% and 10.16% respectively while comparing the control flexural strength
Portland cement and Silica fume (1.5%, 2.5% & 5%) used as binder with 10%, 30% and 50% replacement of Msand instead of natural river sand. However, 10% replacement with 2.5%SF decreases the percentage difference up to 1.37% and in the same sand proportion with 5%, SF increases the flexural the percentage difference by 8.14% than 1.5% SF flexural strength. In 30% replacement flexural strength of 2.5%SF decreases its percentage difference up to 1.83% and in 5%SF increases its percentage difference by 7.29% than 1.5%SF flexural behaviour. By 50% replacement 2.5% and 5%SF increases its percentage difference to 5.21% and 6.89%, respectively in comparison with 1.5%SF
In M20 grade concrete 20%,40% and 60% Msand is replaced instead of river sand. Moreover, there is also 2.89%, 6.04 and 16.50% increase in percentage difference respectively. Moreover, M30 grade supplants 20%,40% and 60% Msand to natural river sand. Laboratory Flexural results showed an increases in percentage difference by 0.93%, 9.25% and 14.64%, respectively in comparison with control concrete flexural strength
Graphical abstract clearly states that the recommended percentage of FeCr slag and Manufactured sand replacement instead of river sand. FeCr slag can be replaced upto 40% to 50% by weight and Msand can be supplants 80% to 100% of virgin sand. Colour of FeCr slag was nigritude black due to some amount of chromium and iron, Msand was grey which represented in image.
FeCr slag has leaching characterised metal CrVI from industrial waste slag, so before using it one has to characterise its physical and chemical properties.
FeCr Slag as fine aggregate is slow reactive due to MgO and reduces its earlier strength. At later ages it shows a good result than ordinary sand strength.
The shape and texture of FeCr slag support a matrix to give a brittle nature and it also consumes less amount of water though slag is porous in nature..
Higher thermal conductivity of slag leads to the reduction of the thermal stress on matrix.
The conclusion of the study emphasizes that FeCr slag sand from 40% to 50% by weight replacement shows better strength performance compared to river sand. 50% of Msand gives better flexural strength results than all the other replacement.
Manufactured sand gives high early strength due to Al2O3 and SiO2 ingredients. Zone II of the crushed Msand is a better one than all other zone sands.
Msand is far better than FeCr Slag as aggregate, based on bonding (ITZ) between cement pastes and increases its mechanical test result values.
The pore structure of Msand is much lesser than FeCr slag composite. And Msand can be 80 - 100% replaceable based on these literature studies (vide Graphical Abstract).
A brief study concludes and recommends based on delay in the earlier strength of FeCr slag matrix and greater earlier strength of Msand matrix. But both FeCr and Msand can be replaceable in concrete and mortar. FeCr slag can be suggested for use in small concrete blocks, concrete wall panels, and where there is a delay in the removal of shuttering and framework. Manufactured sand can be suggested for all types of concrete like Fast track opening projects, metro works, bridges, and skyscrapers.
The authors would like to acknowledge the Anna Centenary Research Fellowships scheme (ACRF) of Anna University, Chennai, India.