Page 6 - Open-Access-July-2019

TECHNICAL PAPER

2.1.2 Fine Aggregate was carried out in order to find the proper mix proportion
for a M 25 grade concrete. Once a mix ratio was obtained,
Natural river sand passing through 4.75 mm IS sieve, conforming concrete cubes of 150 x 150 x 150 mm were cast and tested to
to zone II of IS 383: 1970 [14] was used. The specific gravity and see whether the targeted compressive strength is obtained. A
the fineness modulus of fine aggregate were 2.58 and 3.83 constant W/C ratio of 0.5 was adopted. Due to higher water
respectively. absorption of recycled coarse aggregates, water in proportion
to percentage of absorption was added as extra to the mix. The
2.1.3 Natural coarse Aggregate mix proportions adopted is given in Table 1.
Crushed natural stone of maxi-mum size 20 mm, with a specific
gravity and water absorption of 2.68 and 0.91% respectively, table 1: Mix design data
were used as coarse aggregate for the work. Samples of the
coarse aggregate used for this study were tested as per IS dEscrIptIon QuantItIEs
2386:1997 [15] and it was found to be conforming to specifications Grade of Concrete M25
of graded aggregates in IS 383:1970
Cement content (kg/m ) 383.2
3
Mix ratio 1:2.04:2.69
2.1.4 recycled coarse Aggregate
W/C ratio 0.5
The recycled coarse aggregates used in the experimental study
were 20 mm down size. Recycled aggregate used in this work Cube strength of specimen (28 days) 33.12 MPa
is taken from crushed concrete cubes. The crushed concrete
rubbles were oven dried at 300ºC for 24 hours and ground in
Los- Angeles abrasion testing machine with steel balls. The 2.3 casting and testing of specimens
aggregate and cement mortar powder are separated using sieve
and fraction below 4.75 mm was rejected. The recycled coarse Cement concrete is a well-proportioned mixture of cement,
aggregate was standardized to satisfy the grading requirements coarse aggregates, fine aggregate and water. For the column
of graded aggregates as per Indian standard IS 383:1970. reinforcement, Fe 500 grade steel bars were used and for
Specific gravity and water absorption were found to be 2.32 and confinement; ferrocement, GI wire mesh was used. PVC
6.25% respectively. pipes were used as moulds for the casting of circular column
specimens. Concrete mix was prepared according to the mix-
proportions of M 25 mix designed and placed into the moulds.
2.1.5 wire Mesh
GI wire mesh of 0.44 mm diameter woven in square pattern is The clear cover provided was 40mm. The specimens were
used for confinement in ferrocement. The grid size of mesh is de-moulded after 24 hours and placed under water for proper
4 mm x 4 mm. curing. The circular column specimens were cast in two size
groups with varying height and same diameter. The column
dimensions were 250 x 700 mm and 250 x 1200 mm. Columns
2.1.6 Ferrocement cement Mortar were designed as short columns under axial compression as per

For the ferrocement mortar, trial mixes were made to obtain the IS 456: 2000 codal provisions. Each column is reinforced with
mix proportions for the target cube strength of 50 MPa while 6 bars of 10mm diameter as longitudinal reinforcement and
maintaining a reasonable level of workability. This was achieved 6mm diameter stirrups @ 160 mm c/c spacing. For each group,
by altering the W/C ratio while maintaining the cement to sand one column was kept as control sample (Unconfined specimens).
ratio as 0.5. An average compressive strength of 52 MPa was From each group, specimens with recycled aggregates were
obtained when using cement to sand weight ratio of 0.5, W/C used for confinement. The details of column specimen cast
ratio of 0.4. and reinforcement details are shown in Table 2 and Figure 1
respectively.

2.2 Mix proportions
After 14 days of curing, any dust or loose particles on the surface
On the basis of the material properties, the proportioning of was removed and allowed to dry. On the prepared surface, the
concrete mix was carried out in accordance to IS 456:2000 [16] and wire mesh was wrapped, followed by the application of layer of
as per the guidelines of IS 10262:2009. Initially a trial mix design cement mortar of 25 mm thickness.

20 The IndIan ConCreTe Journal | JulY 2019