Received Date: 17 June, 2017 Accepted Date: 24 November, 2017
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The main objective of this research is to study the ultimate load carrying capacity of Ferro cement columns. The strength of mortar plays a vital role in affecting the performance of specimens. In this experimental work four columns were casted and tested in a column testing machine under axial loading. The results of solid Ferro cement column and hollow Ferro cement column were compared with the conventional RCC column, and it is evident that the ultimate strengths of solid Ferro cement column and Hollow Ferro cement column were increased up to 6.6% and 13.3%.
Ferro cement, Hollow, Ultimate load, Mortar, Wire mesh
Ferro cement is one of the earliest versions of reinforced concrete. However, its design has been mostly empirical, and formal design guides have not developed as they have been for more traditional reinforced concrete. IS 456-2000 gives detailed design guidelines for reinforced concrete structures. However Ferro cement is not specifically covered, and the design guidelines for Ferro cement produced by ACI Committee 549 (ACI 549) lacks detail in its use as a repair and strengthening the material. In the earthquake-resistant design of structures, over strength and ductility are key factors that influence safety. Ferrocement is the combination of cement mortar and thin layers of wire mesh. This study investigates the use of Ferro cement and its use as a construction material for new structures in seismically active zones. Ferro cement has been used as a strengthening and repairing material, especially for quick repairs and strengthening measures for civil engineering structures worldwide. The advantages of using Ferro cement wrapping are its adaptability, high strength to weight ratio, superior cracking characteristics, and good bond with existing concrete surface, improved ductility and impact resistance when compared to conventional strengthening materials such as steel plates. Ferro cement behaves as a similar elastic material over a wide limit because the uniformly distributed mesh reinforcement results in a better crack-resisting mechanism. (Ivy, 2013) Has experimentally investigated the circular columns using high-performance Ferro cement. By replacing the concrete cover with High-performance Ferro cement cover, the strength achieved is 30–59% higher than normal specimens. (Rajesh, 2003) Have conducted an experimental investigation on Ferro cement columns. From his study, it is evident that by using Ferro cement reinforcement as confining shell for reinforced concrete columns increase ductility and load carrying capacity. (Shinde and Bhusari, 2003) From their study on Ferro cement columns by changing the orientation of mesh resulted in the increase of strength which is 36% more in single layer compared to double layer. (Abdullah and Katsuki, 2003) In this study the researcher presents the behaviour of reinforced concrete columns strengthened with Ferro cement jacketing. Ferro cement usedas a strengthening agent for conventional RC columns showed very good results in ductility and stable during plastic hinge formation. (Mourad and Shannag, 2012) In this investigation researcher studied about repair and strengthening of Ferro cement jacketing to RC columns.Ferro cement jacketing to RC columns shows very good results in compressive strength and stiffness and it is about 28%- 33%. Similarly 15%-28% strength gained in repairing of RC columns with Ferro cement jacketing. (Yaqub, et al., 2013) Researcher conducted experimental study on post heated circular and square columns repaired with Ferro cement jacketing. By conducting various experiments optimal solution to regain the strength of post heated columns is by providing both the Ferro cement jacketing and fibre reinforced polymers will show better results in ductility, compressive strength, stiffness etc. (Rathish, et al., 2007) In this study researcher presents the seismic loading tests on RC and Ferro cement columns with jacketing. Energy dissipation capacity, ductility, stiffness had increased because of using Ferro cement as external confinement in columns. (Amrul, 2013; Mohammad and Reza, 2005) In this study by improving square Ferro cement jacketingthe ultimate load carrying capacity of columns were increased and failure at corners had minimised.
Material properties and specifications
Ordinary Portland Cement (OPC) of 53 grade is usedfor test specimens for making both mortar and concrete which is confining to IS 12269. Specific gravity of ordinary Portland cement is 3.15.Fine aggregate is commonly used in the matrix and coarse aggregate is used in preparing concrete. Specific gravity of fine and coarse aggregates are 2.64 and 2.7. Aggregates having high hardness, large strength and containing sharp silica can achieve the best strength results. However, the aggregate should be kept clean, inert, free of organic matter and deleterious substances and free of silt or clay. Additionally, (IS 10262-2009) requires that 80%-100% of the weight of the aggregate should pass the IS Sieve No.7 (2.36 mm). The water used in Ferro cement should be fresh, clean and free from organic or harmful solutions.Welded wire mesh is used in this study which has a higher stiffness than woven mesh, which is why the welded mesh leads to smaller deflections in the elastic stage. The galvanized iron weld mesh is shown in (Figure. 1) having a diameter of 1.26 mm and spacing of 15 mm centre to centre. Welded mesh is more durable, more intrinsically resistant to corrosion and more stable in structures than woven mesh (Bo, et al., 2013; Kaish, et al., 2012).
Mix proportions and design specifications
In this experimental study, M30 grade concrete mix is designed as per IS 10262-2009. 150 mm × 150 mm × 150 mm sized cubes were casted and tested to find the compressive strength. Two trial mixes were done to find the best grade of a matrix to cast Ferro cement columns. 70.6 × 70.6 × 70.6 mm sized cubes were casted and tested to find the compressive strength of matrix which is confining to IS 10080-1982. The details of mix proportions are shown in Table 1.
|Volume of cement (kg/m3)||678||640||492.5|
|Volume of fine aggregate (kg/m3)||1357||1440||651|
|Volume of coarse aggregate (kg/m3)||-||-||1084|
|Volume of water (kg/m3)||305||289||197|
Table 1. Details of mix proportions.
One square reinforced concrete column and three Ferro cement columns were casted. The detailing of reinforcement in columns is shown in (Figure. 2), and it consisted of four longitudinal 8 mm ribbed steel bars and seven 6 mm steel bar stirrups, with 190 mm spacing in between. The prepared reinforcement cage was held carefully in the moulds. Concrete spacers of 20mm size were used to maintain 20 mm concrete cover to the main reinforcement. One column had two-layers of galvanized iron welded mesh, and two columns had one-layer of mesh. The dimensions and skeleton of reinforcing mesh is shown in above (Figure. 1). One RCC column was casted and two Ferro cement solid columns, one Ferro cement hollow column (Syal and Rejivsyal, 1997; American Cement Institute; IS 456:2000). A total of 4 specimens which is having a dimension of 1000 mm height and a cross section of 110 × 110 mm were casted and tested as shown in (Figure. 3). These specimens are tested by using 500 kN hydraulic jack and proving ring which is arranged in a column testing machine. Deflectometers are arranged in center of the column on both sides of a specimen to find deflection. The testing frame is shown in (Figure. 4) (section along with the specimen).
The compressive strengths of concrete and mortar mix for 7, 14, 28 days are shown in (Figure. 5). All casted cubes of concrete and mortar are tested in compressive testing machine which has a capacity of 200 ton as shown in (Figure. 6). Total of 27 cubes (9 cubes for concrete and 18 cubes for mortar) were tested to find the compressive strength.To find the best matrix two trial mixes were used. Concrete achieved a strength of 32.4 N/mm2 and mortar mix achieved a compressive strength of 37.4 N/mm2 after curing of 28 days. Experimental results for cubes were shown below in Table 2.
|Variables||Days of curing||Collapse load (kN)||Compressive strength (N/mm2)|
|Ferr cement (Trial mix-1)||28||170||34.1|
|Ferro cement (Trial mix-2)||28||187||37.4|
Table 2. Compressive strength of cubes.
All the tested specimens with failure crack patterns are showed in (Figure. 7-9) respectively. Failure of Ferro cement hollow column is clearly shown in (Figure. 7) and the crack occurred at the top face of column, weld mesh buckles out. Similarly for conventional column the failure occurred at bottom face of column and spalling of concrete occurred as shown in (Figure. 8). Conventional column has achieved a compressive strength of 232 KN with a deflection of 1.62 mm. Failure of Ferro cement solid columns takes place along the periphery of specimen, diagonal cracks were observed and spalling of mortar takes place instead of buckling welded mesh are clearly shown in (Figure. 9). The collapse load thus determined for all columns were shown in Table 3. Load vs. deflection graphs were plotted for all the tested specimens are shown in (Figure. 10). Ferro cement hollow column carries a load of 272 KN with a deflection of 2.86mm. By increasing number of layers of weld wire mesh compressive strength increased and initial deflection got minimised. Cost analysis were carried out for all the casted specimens and shown in Table 4.
|Specimen||RCC||Ferro cement Hollow||Ferro cement (1 layer of mesh)||Ferro cement (2 layers of mesh)|
|Reinforcement details||#4,8Ǿ||1.26 mm GI mesh||1.26 mm GI mesh||1.26 mm GI mesh|
|Grade of mix||M30||M30||M30||M30|
|Ultimate load (KN)||236||272||252||324|
Table 3. Comparison of collapse load for RCC and ferro cement columns
(1 layer of mesh)
|Ferro cement hollow||Ferro cement
(2 layers of mesh)
|Weight (kg)||Cost (Rs)|
Table 4. Cost analysis for RCC and ferro cement columns
In the earlier studies the work on Ferro cement hollow column were not found. The main aim of this research is to know the performance of Ferro cement hollow column. The above results states that the optimal design of Ferro cement hollow column provides better compressive strength by comparing with conventional and Ferro cement solid columns with same sized specimens. Cost analysis is carried out for all tested specimens and Ferro cement hollow column has 34.66% and 25.5% reduction in cost while comparing to conventional column and Ferro cement solid columns.
1. The ultimate strength of solid Ferro cement column is increased by 6.6% more than that of the conventional column for the same size of the specimen.
2. The compressive strength of Ferro cement hollow column is compared with RCC column and achieved 13.3% higher strength.
3. Based on test results, by increasing layers of weld mesh the compressive strength of columns increased.
4. By comparing ferro cement solid column and ferro cement hollow column. Ferro cement hollow column will give higher compressive strength and lesser deflection.
5. Ferro cement hollow column has a 34.66% reduction of cost while comparing with conventional column.