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IBRACON Structures and Materials Journal • 2012 • vol. 5 • nº 3
Experimental analysis of reinforced concrete columns strengthened with self-compacting concrete
and connectors
ing revealed 8 and 11 seconds for the first and second tests, re-
spectively, whereas the second casting revealed 7 and 10 seconds
for the first and second tests, respectively. The test arrangements
consists of a metal porch anchored by tie bars connected to the
strong slab. Figure 10 displays the arrangements of the test sys-
tem used.
3. Results
This topic presents and analyses the main results obtained from
tests and is divided into three sections: loads and failure modes,
horizontal displacements of the columns and finally the strains
measured in reinforcements and on the concrete’s face.
a) Load and failure mode
The original reference column P1 failed at 140 kN by steel yielding,
whereas monolithic reference column P2 failed at 450 kN by con-
crete crushing. The remaining columns failed by concrete uncoat-
ing, except column P8, which showed concrete crushing. Strength-
ened columns P6 and P6A showed greater concrete strain than
concrete crushing (3.5 mm/m - NBR and 3.0 mm/m - ACI), but af-
ter uncoating. Table 2 shows failure loads, strengths and elasticity
moduli of both substrate and strengthening concretes on the assay
dates of each model, initial and final eccentricities, maximum steel
and concrete strains and failure modes of each column. Strength
values of conventional and self-compacting concretes averaged
10% and 25%, respectively; they were higher for columns P1 to P6
than for columns P6A, P7 and P8. Figure 11 shows the location of
the failure in each tested column.
The monolithic column P2 (155 mm x 250 mm) failed with a 450 kN
load. This column was built to represent the maximum load capac-
ity possible that reinforced columns could reach. The P8 column
reinforced with the highest failure load, failed with a load 16% (Pu
= 520 kN) greater than that of P2. A likely and possible small dif-
ference in initial eccentricity could be one reason for the decrease
Figure 8 – Placement of reinforcement connectors
3
Table 1 – Proportion of substrate materials per m of concrete
Materials
Substrate
Strengthening Concrete (SCC)
3
Quantity (p/m )
3
Quantity (p/m )
Cement
310 kg
360 kg
Natural Fine – Coarse Sand
155 kg - 233 kg
730 kg - 0 kg
Artificial Sand
497 kg
-
Silica
-
31 kg
Grit 0 – 1
388 kg - 619 kg
930 kg - 0 kg
Water
155 l
223 l
Superplasticizer
-
-
3.96 kg (1.1% on cement)
Set Retarder Additive
2.17 l
2.88 kg (0.8% on cement)
Slump (95 ± 10) mm
Flow test = 700 mm