Table of Contents
Supplementary Cementitious materials
World os witnessing shortage of materials for construction of civil structures and buildings. Concrete is most widely used material in world after water. It should possess high strength and workability characteristics. Research are made in field of comcrete technology and construction to develop more durable concrete and improve its tensile properties by cementitious materials and fibres. Recycling of waste materials is an important aspect in construction nowadays. The steel waste which has properties of BFS and Metakaolin could be used as a replacement of fine aggregate as well as an added fibre concrete to improve its properties. A good management solution of such waste will create some important marks in concrete technology as it is a proper way of managing and recycling of the waste products.Fiber reinforced concrete (FRC) is a composition of hydraulic cement, sand, coarse aggregate, water and fibers.Addition of various types of fibers and cementitious materials such as such as steel,metakaolin , glass, synthetic, and carbon in plain concrete improves strength, toughness, ductility, post-cracking resistance, and etc.
Dfferent formulations Like cementitious materials and fibres are recommended. The usage of steel fibres and other cementitious materials are recommended for concrete durability and strength.
The fibres and other cementitious materials to be added in concrete may mixed as percentage of total volume of concrete or by percentage of cement. Both are conventional methods. Aspect ratio of the materials is to be checked before grading of constituents of concrete. Mix design shall be conducted as per ACI volume mixing which is attached at last of this paper. It is also necessary to check the properties of concrete like chemical test, acid resistance test, corrossion test, rockwell hardness test and other non destructive test of materials as a part of durability studies. By adding fibres or cementitious materials it improve durability properties of the material by reducing creep and improving modulus of elasticity of materials fibres recommended here is added from 0.1 to 3 % Here compressive strength, split tensile strength and flexural strength of the materials are improved to higher extend by usage of cementitious materials.
1) Stabilization of slopes for geotechnical studies supporting foundations.
2) Road pavement , foundation slabs, floors of industrial buildings and warehouses
3) Bridge abutments, piers and its foundations.
4) Rehabilitation of marine structures such as dock wall and wharf footings.
5) Chemically failed concrete structures deteriorated due to acid attacks
6) Support of tunnels and mines underground
Here we use steel scrap as a main material to be added in concrete to improve its strength properties an durability.As its a waste product from lathe industry the procurrement and usage is much easier. As per teh study strength and durability properties are improved to higher extend Mix chosen for concrete was 1:2:4 :0.5 (c:fa:ca:wcratio). fibres were added at 2,3,4% to the total volume of concrete.
Adding of steel lathes waste fibers in plain concrete enhance its strength under compression. Adding of steel lathes waste fibers imporves strength and durability and reduces the workability of fresh concrete not to fall the slump beyond the limit.By this method . It may be a good environmental management of lathes steel wastes since a large quantity of steel wastes are generated from industrial lathes ( 3-4 kg/lathe.day). The recycling represents a solution of that waste and make use of it.
Various strength tests including compression, flexure and split tension were conducted and 7 days strength of fibre concrete showed a considerable increase in strength compared to other concretes.The inclusion of lathe scrap in concrete has increase the performance of beam in flexural by 30-40% when compared with PCC. There is only a small increase in the split tensile strength of concrete with steel cementitious material when compared with PCC.
The mechanical properties of the concrete are increased by increasing the mix proportion of the steel scrap from 0.5% up to 1.5% to the total volume of concrete . From1.5% to 2.0% it shows slight decrease in the mechanical strength. At 2.0% of steel scrap proportion there is a small reduction in the mechanical strength of supplementary cementitious material concrete .The compressive strength of the concrete is increased by an amount of 10% for 7 days strength when compared to ordinary concrete for all the tested proportions of lathe scrap and steel fiber. For the 28 days strength the fibre concrete poses almost the same compressive strength as PCC for all the tested proportion. The addition of steel scrap as cementitious material has significantly improved the performance of beam in flexural nearly 40% when compared with ordinary concrete .There is a small increase in split tensile strength of about 10% when compared to PCC. The result showed that addition of steel scrap as supplementary cementitious material in to PCC mixture enhanced its compressive strength while it decreased the work-ability of the fresh concrete containing the lathe scrap in most of the cases.
Cement is the binding agent in concrete . Addition of materials in cement like metakaolin and flyash as partial and complete replacement may improve the properties of cement to a higher extend.
3.2 Fine aggregate:
The material smaller than 4.75mm size is called fine aggregate. Natural sands are generally used as fine aggregate. It may be obtained from pits, river, lake or sea shore, but it should free from clay and silt. Sea shore sand may contain acids, chlorides, which may cause efflorescence and not resist to acid attacks and may cause corrosion of reinforcement. Angular grained sand produces, good and strong concrete because it has good interlocking property, while round grained particle of sand do not afford such interlocking.y. The specific gravity and water absorption were found to be 2.74 and 2.65% respectively.
3.3 Coarse aggregate:
The material retained on 4.75mm sieve is termed as coarse Aggregate. Crushed stone and natural gravel are the common type material used as coarse aggregate for concrete.
In general, for mixing of constituents water is used. Excess of acidity or alkalinity in water is to be avoided. Potable and hardless water is used for this work.
4.1 Lathe waste fibre:
Length - 20-30 mm
Width - 1.5 - 2 mm
Thickness - 0.3-0.6 mm
Aspect ratio - 50-70
Modulus of elasticity - 200 Gpa
4.2 EAF Flue Dust :
Electrical arc furnace dust is a major supplementary cementitious material during steel process . Major part is iron oxide and 10-15 % is oxide of zinc , lead ,cadmium
4.3 BF Slag, BOF Slag and EAF Slag :
Here slag is produced as from BOF,EAF and BF is non metallic. These also contains cadmium levels and used as aggregate in industry.
4.4 Millscale :
Steel mills can produce mill scale, which is primarily iron oxide and cadmium materials and is reused/recycled.
4.5 Spent Pickle Liquor
The term “spent pickle liquor” refers to solutions containing soluble metals and acids.
Generated form iron oxide and phosphate and other materials.
4.6 BF Flue Dust :
B F slag is an important supplementary cementitious material which consists of iron oxide , lime and blast furnace as a result of smelting. Usually 1.5 % zinc and iron oxide.
4.7 BF Waste Sludge :
Wet scrubber to capture dust particles from gases during operations. Sludge particles here contains 30 -60 % of water.
4.8 BF Filter Cake :
It is a blast furnase slag after dewatering process . it contains 15-20% water.
4.9 BOF Flue Dust :
Flue dust is released as basic oxygen furnace process of steel making. It typically iron oxide and 1.5-4% of zinc.
4.10 BOF Waste Sludge :
Wet scrubber from steel mills capture iron oxide particles from oxygen furnace. The sludge her e consists of iron zinc oxide particles which has sludge usually containing 30-60 % water.
4.11 BOF Filter Cake :
Here water sludge have been de-watered and contains 15 -20 % of water as BOF filter cake.
Step 1 : Choice of material may be establised based on site conditions as
Step 2 : maximum size of aggregate
Step 3 : Mixing of water
Step 4: Maximum permissible Water cement ratio
Step 5: Cement content = weight of cement /wc ratio
Step 6: Estimation of coarse aggrgates
Step 7: Adjustments for coarse and fine aggregates
Step 8: Preparation of trial mixes
Industrial Resources Council (2008). "Portland Cement Concrete". industrialresourcescouncil.org. Retrieved 15 June 2018.
National Highway Institute. "Portland Cement Concrete Materials" (PDF). Federal Highway Administration.
Li, Zongjin (2011). Advanced concrete technology. John Wiley & Sons. ISBN 9780470902431.
"What is the development impact of concrete?". Cement Trust. 24 October 2010. Archivedfrom the original on 17 September 2012. Retrieved 10 January 2013.
"Global Ready-mix Concrete (RMC) Market worth over USD US$ 624.82 Bn by 2025: QY Research, Inc". Digital Journal(Press release).
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