14 chloride content decrease after certain depth. Perhaps, this trend due to carbonation

process. Carbonation affected to push chloride ions deeper into concrete due to dry-wet cyclic chloride in tidal zone. In other way, the penetrated chloride ions at the outer region of the specimen migrate more inward due to carbonation [4.20]. This process considered also support from pre-cracked which are increased degradation of concrete due to more aggressive agent into concrete. The more degradation of concrete the more of carbonation depth will be. Based on the measurement results, the rate of carbonation in average with and without pre-cracked up to 0.783 mm/year and 0.466mm/year for PC-O and PC-R respectively. This results indicates that carbonation effect give minor effect than pre-cracked.

4.4.4 Load Carrying Capacity

a. Decompression Load and Prestress Loss

The decompression load was determined by intersecting the two slopes. Plot of applied load vs. displacement to determine the decompression load is presented in Fig. 4.10 It seems that pre-cracked affected to the decompression load as the results reducing in effective prestressed. Prestressed concrete beams type post-tensioning with pre-cracked showed smaller decompression load than without pre-cracked.

Further, prestressed concrete type pre-tensioning also showed reducing in decompression load due to pre-cracked. This is considered that pre-cracked could reduce decompression load about 35.80% for post-tensioning type and 19.10% for pre-tensioning type, respectively. Perhaps, loss of bond between the strand/wire and concrete or through cracking and spalling of the concrete may give significantly affect as the result from corrosion product. It can be said that pre-cracked allowable more deterioration in progress, as the result reducing in effective prestressed.

IV-15

Un-Cracked Cracked

Fig. 4.10 Determination of decompression load from the load-displacement data

The total prestress loss obtained by determined of decompression load and a simple elastic analysis is shown Fig. 4.11 and summary of prestress loss in shown Table 4.3. The effect of pre-cracked for both PC-O and PC-R clearly seen in affected to prestress loss. The total prestress loss for PC-O and PC-R due to pre-cracked about 23.7% and 38.2% respectively. Post-tensioning type, pre-cracked also contributed of prestress loss due to produce deteriorated a part of anchorage

0 20 40 60 80 100 120

0 1 2 3 4

Load, kN

Displacement,mm PC-O-1

Decompression Load ≅80 kN

0 20 40 60 80 100 120

0 1 2 3 4

Load, kN

Displacement,mm PC-O-3

Decompression Load ≅44 kN

0 20 40 60 80 100 120

0 1 2 3 4

Load, kN

Displacement,mm PC-O-2

Decompression Load ≅82 kN

0 20 40 60 80 100 120

0 1 2 3 4

Load, kN

Displacement,mm PC-O-4

Decompression Load ≅60 kN

0 20 40 60 80 100 120

0 1 2 3 4

Load, kN

Displacement,mm PC-R-1

Decompression Load ≅89 kN

0 20 40 60 80 100 120

0 1 2 3 4

Load, kN

Displacement,mm PC-R-2

Decompression Load ≅72 kN Crack re-opening Crack re-opening

Crack re-opening

Crack re-opening

Crack re-opening

Crack re-opening

IV-16 zone. Perhaps during loading for pre-cracked (i.e., 0.65 moment ultimate) anchorage zone have an increasing local stress and produced numerous of crack.

Numerous of crack on anchorage zone lead to anchorage slip and produce prestress loss. The prestress loss likelihood may be produced by accumulative of deterioration of the beams (i.g., spalling, longitudinal cracks, anchorage zone cracks) as the result of the corrosion products.

Fig. 4.11 Prestressing force loss

Table 4.3 Summary of prestressing force loss

Name Prestress Force (kN)

Prestress Loss (%) Initial, Pi Effective, Pe

PC-O-1

443.5

342.4 22.8

PC-O-2 334.2 24.6

PC-O-3 166.6 48.9

PC-O-4 206.3 44.8

PC-R-1

517.3 402.6 22.2

PC-R-2 319.6 38.2

b. Change in Flexural Moment

The changes in ultimate flexural moment against the exposure time is shown in Fig. 4.12from view point of load carrying capacity. The ultimate flexural moment is expressed as the ratio to the initial (before exposure) flexural moment was shown in this figure. It seems pre-cracked affected to the flexural moment both PC-O and

0 50 100 150 200 250 300

PC-O-1 PC-O-2 PC-O-3 PC-O-4 PC-R-1 PC-R-2

Prestress Loss, kN

IV-17 PC-R beams. The change of flexural moment affected due to pre-cracked about 5.6% and 4.4% for PC-O and PC-R respectively. The moment capacity decrease as the compressive strength of concrete dropped and loss of prestressed in despite reached the large ultimate load enough. This considered deterioration in sequence due to pre-cracked in the view point of load-bearing capacity.

Fig. 4.12 Change in flexural moment

Table 4.4 Summary of several points during loading procedure

Name

Applied Load, kN

Neutral Axis, mm

Effective Prestressed,

MPa Decompression

Load

First Crack

Ultimate Load

PC-O-1 80 92 215.4 195 7.6

PC-O-2 82 90 236.2 190 7.4

PC-O-3 32 50 227.3 125 3.7

PC-O-4 53 74 231.4 120 4.6

PC-R-1 89 90 192.7 195 8.9

PC-R-2 72 50 227.9 186 7.1

Summary of several points during loading procedure is presented in Table 4.3.

The first crack observed on PC-O beams with and without pre-cracked about 30 kN and 80 kN respectively. Further, the first crack observed on PC-R beams with and without pre-cracked about 50 kN and 90 kN respectively. It seems that pre-cracked reduced load-carrying capacity by promote early cracks during loading. Further, the

0.5 0.75 1 1.25 1.5

0 10 20 30 40

Mu/Muo

Exposure time (year)

PC-O-1 PC-O-2 PC-O-3 PC-O-4 PC-R-1 PC-R-2

IV-18 effect of pre-cracked continuously on neutral axis. The effect of pre-cracked reduced the effective of tension region about 70 mm and 10 mm for O and PC-R beams respectively. Overall, it could be said that pre-cracked affected to the load carrying capacity.

4.4.5 Corrosion State of Prestressed Tendon/Wire and Steel Bars

The beam specimens were crushed, and all strand/tendon and steel bar were removed to evaluate the reinforcement surface appearance and corrosion area was measured after flexural testing and sketching of crack formation was completed.

Based on observation results show that no changes in stirrups and longitudinal bars shape after bending test and all tendon sheaths was corroded on PC-O beams. Fig.

4.13 show corrosion state of longitudinal bars, stirrups, tendons/prestressing wire and anchorages. Most of the longitudinal bars on the tensile zone of beam suffered severe corrosion, instead, on the compressive zone show the better condition. The same pattern was also shown by stirrups, which at the bottom side mostly suffered quite severe corrosion while the top side remains in good condition. This considered that the effect of tidal zone i.e. natural dry-wet cycled take place

Fig. 4.13 The corrosion state of reinforced bars of PC-O-3 and PC-R-1 beam

PC-O-3 PC-R-1

IV-19