ROAD B5 BRIDGES INSPECTION DETAILED REPORT copy.docx

MTRD ICT

MINISTRY OF TRANSPORT AND INFRASTRUCTURE

STATE DEPARTMENT OF INFRASTRUCTURE

MATERIALS TESTING AND RESEARCH DIVISION(MTRD)

DETAILED INSPECTION OF BRIDGES ALONG NAKURU-NYAHURURU-

NYERI –MARUA ROAD(B5)

MTRD REPORT NO.1233

MAY,2015

CHIEF ENGINEER (MATERIALS )P.O. BOX 11873-00400

NAIROBI

INTERNATIONAL CONSULTANTS AND TECHNOCRATS(ICT) PVT LTDA-8, GREEN PARK NEW DELHI -

110016, INDIA

DETAILED INSPECTION REPORT FOR BRIDGES ALONG ROAD B5

MTRD ICT

1.0 INTRODUCTIONThis bridge inspection report is in response to a request made by M/S International Consultants and Technocrats (ICT) Pvt Ltd of A-8, Green Park New Delhi -110016, and India to undertake inspection of structures along road B5. This was done under the project: “Consultancy Services for a Feasibility Study, EIA, SIA and Detailed Designs Including Tender Documents for Rehabilitation of Nakuru-Nyahururu-Nyeri –Marua Road”.

A total of seven structures had been targeted for detailed inspection as listed below.

i. Bridge at Km 60+030ii. Bridge at Km 84+520iii. Bridge at Km 93+380iv. Bridge at Km 102+510v. Bridge at Km 125+670vi. Bridge at Km 142+450vii.Bridge at Km 173+120

This report contains a description of the structures, visual observations, description of testing methods, test results for various parameters based on different Non-Destructive Testing methods, conclusions and recommendations.

The report is factual and dwells mainly on the status of structural elements and their material components.

The primary results of these inspections are given and the critical problems have been highlighted.


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1.1 Scope of workThe scope of work as shown below involved testing of structural elements in both the superstructures and substructures for each of the seven bridges for several parameters using various Non-Destructive Testing methods.Table 1: Scope of work

Item no. Structural

elementParameters tested Inspection details/methods

1 Abutments

Appearance Carry out visual inspectionRe-bar details Carry out electromagnetic

testsInsitu Concrete strength Carry out Schmidt hammer

testsQuality, homogeneity and internal defects of concrete matrix

Carry out ultrasonic pulse velocity tests

Deterioration status of the concrete matrix

i. Corrosionii. Remaining effective

good covers

i. Carry out resistivity/half cell potential tests

ii. Carry out carbonation depth tests

Crack profilingi. Widthii. Depthiii. length

i. Use of crack width microscope to measure crack widths

ii. Carry out ultrasonic tests to measure crack depths

2Piers

i. Wall type ii. Column

typeDitto Ditto

3 Deck slab Ditto Ditto

4 Steel Girders

Laminations Carry out ultrasonic testsCorrosion Carry out visual inspection

and ultrasonic thickness testsPlate thicknesses Carry out ultrasonic tests

Continuity of critical welds if any

Carry out radiographic tests

5

Ancillary Fixturesi. bearingsii. expansion

gapsAppearance Carry out visual inspections


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3.0 SUMMARY OF TEST RESULTSGenerally the findings from all the tests done indicate a lot of similarity for six structures in terms of re-bar distribution for various structural elements, cracking patterns, steel girder types ,numbers & sizes, type of ancillary fixtures and concrete deterioration status.

The findings for bridge at km173+120 (at Marua) were different from those of other structures.

Inspection results have been summarized for each structure and are presented below.


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3.1 BRIDGE AT KM 60+030…This is a single span structure comprising a composite deck with 5 no. steel beams, wall type RC abutments and wing walls.

Photo 1: A side view of bridge at km 60+030

3.1.1 ABUTMENTS3.1.1.1 Visual Inspection

Two vertical cracks running full height were found on the Nyeri side abutment. The cracks appear approximately midway between the beam supports at the abutment cap. The crack widths vary from 0.8-1.4mm

Fig. 1: showing crack profiles for Nyeri side abutment


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BRIDGE AT KM 60+030

Photo 2: a vertical crack on an abutment wall

One vertical crack was found on the Nyahururu side abutment. The crack appearednear the inner RHS beam support at the abutment cap and propagated the full height of the abutment wall. The maximum crack width recorded was.1.0 mm

Fig. 1: showing crack profiles for Nyeri side abutment

3.1.1.2 Steel Reinforcement details for the Abutments

The reinforcement details as gathered through electromagnetic method revealed the spacing of the reinforcement bars in the abutment walls on


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either side of the bridge was not uniform in the vertical and horizontal directions, varying between 400mm- 450mm and 380-450mm respectively . The vertical re-bars were 25 mm diameter while the horizontal were 16 mm diameter.

BRIDGE AT KM 60+030Steel Reinforcement details for the Abutments

The average covers were varying at different points on either abutment with the lowest at 33 mm and the highest at 71 mm.

3.1.1.3 Concrete strength, quality and homogeneity for the Abutments

The concrete strength as measured through rebound (Schmidt) hammer method recorded strengths of between 44.0N/mm2 to 54.0N/mm2

The concrete matrix was generally homogeneous as revealed through ultrasonic method except at locations where cracks appeared.

3.1.1.4 Crack depths for the Abutments

The crack depths were ultrasonically determined and found to be106mm at the widest points.

3.1.1.5 Concrete Deterioration for the Abutments

Two methods were employed i.e. carbonation and resistivity potential to indicate the level of deterioration of concrete.

The highest carbonation depth recorded was 6mm indicating a remaining good cover of 27mm (least cover recorded was 33mm). This was an indication of low level deterioration.

Probability of corrosion activity was insignificant as indicated by a high resistivity potential of 111.4kΩcm.

3.1.2 DECK SLAB3.1.2.1 Visual inspection of the Deck Slab

Deck slab thickness was 200mm.


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There were several multi directional cracks appearing from the soffit of the deck. The cracks were distributed all over the deck soffit.

Maximum crack width was 1mm.

3.1.2.2 Steel Reinforcement details of the Deck Slab

The reinforcement details as gathered through electromagnetic method revealed that the distribution of the reinforcement bars in the deck slab was uniform both in both longitudinal and transverse directions. The longitudinal re-bars were 20 mm diameter at an average spacing of 400mm while the transverse were 16 mm diameter at an average spacing of 300 mm. The average covers were 50mm and 35mm for longitudinal re-bars and transverse re-bars respectively.

3.1.2.3 Concrete strength, quality and homogeneity

The concrete strength as measured through rebound (Schmidt) hammer method recorded an average strength of between 56N/mm2 62N/mm2

The concrete matrix was inhomogeneous as revealed through ultrasonic method. This could be due to cracking on the deck slab soffit.

3.1.2.4 Crack depths

The crack depths were ultrasonically determined and found to be “through cracks”

3.1.2.5 Concrete Deterioration of Deck Slab


The highest carbonation depth recorded was 6mm indicating a remaining good cover of 29mm (least cover recorded was 35mm).This was an indication of low level deterioration.

Deterioration in this case refers to chemical effects and not physical.

Probability of corrosion activity was insignificant as indicated by high resistivity potential of 110.2DETAILED INSPECTION REPORT FOR BRIDGES ALONG ROAD B5

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BRIDGE AT KM 60+0303.1.4 WING WALLS3.1.4.1 Visual Inspection of the Wing Walls

There were no visual structural defects on the wing walls

3.1.4.2 Steel Reinforcement Details for the Wing Walls

The reinforcement details as gathered through electromagnetic method revealed the spacing of the reinforcement bars in the wing walls on either side of the bridge not to be uniform in the vertical and horizontal directions, varying between 380mm- 480mm and 390-470 mm respectively. The vertical re-bars were 20 mm diameter while the horizontal were 16 mm. The average covers were varying at different points on either side with the lowest at 26 mm and the highest at 71 mm.

3.1.4.3 Concrete strength, quality and homogeneity for the wing walls

The concrete strength as measured through rebound (Schmidt) hammer method recorded an average strength of 58.0N/mm2

The concrete matrix was generally homogeneous as revealed through ultrasonic method.

3.1.5 STEEL GIRDERS 3.1.5.1 Visual Inspection of Steel Girders

There were spots of paint peeling off from the bracings and beams.

The top flanges near the abutment supports had started to corrode as revealed by red/brown colouration stains at the slab soffit joint. However the corrosion was at an early stage without causing any significant reduction in thickness of the steel plate.


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There was accumulation of soil at the abutment caps which covered the bottom flanges of the steel girders causing the paint to peel off resulting in early stages of corrosion.

BRIDGE AT KM 60+030Visual Inspection of Steel Girders

The bolts and nuts for all the joints were in good condition.

There were no critical welded joints.

3.1.5.2 Ultrasonic Thickness Tests for Steel Girders

There was no delaminating of the plates as determined ultrasonically. The thicknesses for the flange and web plates were determined ultrasonically and found to be uniform.

3.1.6 BEARINGSThe bearing type was elastomeric of approximate size 400x280x 30 mm and was in good condition.


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3.2 BRIDGE AT KM 93+380This is a single span structure comprising a composite deck with 5 no. steel beams, wall type RC abutments and wing walls.


3.2.1 ABUTMENTS3.2.1.1 Visual Inspection Abutments

There were four regularly spaced vertical cracks running full height on the Nyeri side abutment. The cracks appeared approximately midway between the beam supports at the abutment cap.

Fig 3: sketch showing the crack profiles on the Nyeri side abutment wall

The crack widths varied from 0.6-1mm.


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3.2 BRIDGE AT KM 93+380Three regularly spaced vertical cracks running full height were found on the Nyahururu side abutment. The cracks appeared approximately midway between the beam supports for the inner LHS& RHS beams and the centre beam.

Fig 4: showing crack profiles for Nyahururu side abutment-measurement in mm

Photo 4: Showing a vertical crack on an abutment



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The reinforcement details as gathered through electromagnetic method revealed the distribution of the reinforcement bars in the abutment walls on either side of the bridge to be uniform in the vertical and horizontal directions.

BRIDGE AT KM 93+380Steel Reinforcement details for the AbutmentsThe vertical s re-bars were 25 mm diameter at an average spacing of 450mm while the horizontal were 16 mm diameter at an average spacing of 450 mm. The average covers were varying at different points on either abutment with the lowest at 28 mm and highest at 66 mm.


The concrete strength as measured through rebound (Schmidt) hammer method recorded strengths between 40.0 N/mm2 to 60N/mm2 for six test points.



The crack depths were ultrasonically determined and found to be 61mm at the widest points.

3.2.1.4 Concrete Deterioration for the Abutments





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BRIDGE AT KM 93+3803.2.2 DECK SLAB3.2.2.1 Visual inspection Of the Deck Slab

Deck slab thickness was 200mm.There were several multi directional cracks appearing from the soffit of the deck. The cracks were distributed all over the deck soffit. There were two major cracks that ran full width on each half of the Nyeri side and Nyahururu side of the deck at approximatetly1500mm from the cross bracing. There were leakage stains along these cracks, an indication that the cracks were through hence the risk of exposure of re-bars to corrosion due to water ingress at the locations. (See photos below)

Photo 5: showing a transverse crack on the deck of bridge at km 93+380

Photo 6: a closer view of the crack in photo 5 above


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BRIDGE AT KM 93+3803.2.2.2 Steel Reinforcement details for the Deck Slab

The reinforcement details as gathered through electromagnetic method revealed that the distribution of the reinforcement bars in the deck slab was uniform both in both longitudinal and transverse directions. The longitudinal re-bars were 20 mm diameter at an average spacing of 400mm while the transverse were 16 mm diameter at an average spacing of 300 mm. The average covers were 50mm and 34mm for longitudinal re-bars and transverse re-bars respectively.

3.2.2.3 Concrete strength, quality and homogeneity for the Deck Slab

The concrete strength as measured through rebound (Schmidt) hammer method recorded an average strength of 55N/mm2 for three test locations.

The concrete matrix was inhomogeneous as revealed through ultrasonic method. This was especially due to numerous multi directional cracks on the deck slab soffit.


The crack depths for the major transverse cracks were ultrasonically determined and found to be through cracks at the widest points.

3.2.2.5 Concrete Deterioration




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Deterioration in this case refers to chemical effects, not physical.

Probability of corrosion activity was insignificant as indicated by a high resistivity potential 108.6

BRIDGE AT KM 93+3803.2.3 WING WALLSVisual Inspection of the Wing Walls

There were no visible structural defects on the wing walls.

3.3.3.1 Steel Reinforcement Details

The reinforcement details as gathered through electromagnetic method revealed the distribution of the reinforcement bars in the wing walls on either side of the bridge to be uniform the vertical and horizontal directions. The vertical re-bars were 220 mm diameter at an average spacing of 450mm while the horizontal were 16 mm diameter at an average spacing of 350mm. The average covers were varying at different points on either side with the lowest at 37 mm and the highest at 68 mm.


The concrete strength as measured through rebound (Schmidt) hammer method recorded strengths of between 58.0N/mm2 to 65N/mm2.


3.3.4 STEEL GIRDERS 3.2.4.1 Visual inspection of Steel Girders

There were spots of paint peeling off from the bracings and girders.

The top flanges near the abutments had started to corrode for approximately 700 mm length. However the corrosion was at an early stage without causing any significant reduction in thickness of the steel plates.


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Photo 1: showing spots of paint peeling off a bracing on bridge at km 93+380

BRIDGE AT KM 93+380There was accumulation of soil at the abutment caps which covered the bottom flanges of the steel girders causing the paint to peel off resulting in early stages of corrosion.



3.2.4.2 Thickness Tests for Girder Plates


3.3.5 BEARINGSThe bearing type is elastomeric of approxsize400x280.30 while loaded and were in good condition.

photo 8:showing a bridge bearing for bridge at km 93+380

3.3.6 OTHER BRIDGE FITTINGSThe guard rails were in good condition.


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photo 2:showing guardrails for bridge at km 93+380

3.3 BRIDGE AT KM 84+520This is a three span structure comprising a composite deck with 5 no. steel girders for each span, wall type RC abutments, column type RC piers and wing walls.

Photo 9:Showing the Approach for bridge at km 84+520

Photo 10: showing the soffit of bridge at km 84+520

3.3.1 ABUTMENTS3.3.1.1 Visual Inspection of Abutments

Two vertical cracks running from mid way the height downwards were found on the Nyahururu side abutment. The crack widths ranged between 0.6-1.0mm.


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Fig 5:showing crack profiles on the nyahururu side abutment

BRIDGE AT KM 84+520One vertical crack running from mid-way the height downwards was found on the Nyeri side abutment. The crack width was 0.8mm at the widest point.


The reinforcement details as gathered through electromagnetic method revealed the spacing of the reinforcement bars in the abutment walls on either side of the bridge not to be uniform in the vertical and horizontal directions, varying between 480mm- 520mm and 360-440mm respectively. The vertical re-bars were 25 mm diameter while the horizontal were 16 mm diameter. The average covers were varying at different points on either abutment with the lowest at 36 mm and the highest at 66mm.


The concrete strength as measured through rebound (Schmidt) Hammer method recorded average strengths of 50.0N/mm2 and 54.0N/mm2 for the Nyeri and Nyahururu sides respectively.


3.3.1.4 Crack depths for the abutment walls

The crack depths were ultrasonically determined and found to be 27 mm at the widest points.



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The highest carbonation depth recorded was 3 mm indicating a remaining good cover of 29mm (least cover recorded was 32mm.This was an indication of low level deterioration.

Probability of corrosion activity was insignificant as indicated by a high resistivity potential of 111.6 kΩcm

BRIDGE AT KM 84+520

3.3.2 DECK SLAB3.3.2.1 Visual Inspection of the Deck Slab

Deck slab thickness was 200mm.There were several multi directional cracks appearing from the soffit of the deck. The cracks were distributed all over the deck soffit. There were two major cracks that ran full width on each quarter of each span at approximately 1500mm from the transverse bracing. There were leakage stains along these cracks, an indication that the cracks were through hence the risk of exposure of re-bars to corrosion due to water ingress at the locations.Othermulti directional cracks are distributed over the entire deck slab soffit.

Photo 11: showing a transverse crack on the deck slab of bridge at km 84+520


3.3.2.2 Steel Reinforcement Details for the Deck Slab


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The reinforcement details as gathered through electromagnetic method revealed the distribution of the reinforcement bars in the deck slab to be uniform in the longitudinal and transverse directions. The longitudinal re-bars were 20 mm diameter at an average spacing of 400mm while the transverse were 16 mm diameter at an average spacing of 300 mm. The average covers were 45mm and 27mm for longitudinal re-bars and transverse re-bars respectively.

BRIDGE AT KM 84+520


The concrete strength as measured through rebound (Schmidt) hammer method recorded an average strength of 46N/mm2

The concrete matrix was inhomogeneous as revealed through ultrasonic method. This could be attributed to numerous multi directional cracks on the deck slab soffit.

3.3.2.2 Crack depths for the Deck Slab

The crack depths were ultrasonically and visually determined and found to through at the widest points.

3.3.2.1 Concrete Deterioration for the Deck Slab

The highest carbonation depth recorded was 3mm indicating a remaining good cover of 24mm (least cover recorded was 27 mm).This was an indication of low level deterioration.

Deterioration in this case refers to chemical effects rather than physical.

Probability of corrosion activity was insignificant as indicated by a high resistivity potential of 111.6.

3.3.3 WING WALLS3.3.3.1 Visual Inspection of the Wing Walls


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There were no visual structural defects on the wing walls.


The reinforcement details as gathered through electromagnetic method revealed the spacing of the reinforcement bars in the wing walls on either side of the bridge not to be uniform in the vertical and horizontal directions, varying between 350mm- 470mm and 260-370mm respectively. The vertical re-bars were 20 mm in diameter while the horizontal were 16 mm .The average covers were varying at different points on either side with the lowest at 36 mm and highest at 64 mm.

BRIDGE AT KM 84+5203.3.3.3 Concrete Strength, Quality and Homogeneity of the Wing Walls

The concrete strength as measured through rebound (Schmidt) hammer method recorded an average strength of 55.0N/mm2 and 54.0N/mm2 for Nyeri and Nyahururu side respectively.


3.3.4STEEL GIRDERS 3.3.4.1 Visual Inspection of Steel Girders

The girders were generally in good condition.There were no critical welded joints along the entire length of the girders.


There were mud stains at the abutment support, causing early stages of corrosion to the LHS girder near the abutment support for a length of approximately 1m.


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Photo 12:showing stains on a bottom flange of a steel girder for bridge at km 84+520

3.3.4.2 Ultrasonic Thickness Tests for Steel Girders


BRIDGE AT KM 84+5203.3.5 PIER COLUMNS

3.3.5.1 Visual Inspection of Pier Columns

The pier columns were generally in good condition.

Photo 13: showing part of a pier column for bridge at km 84+520

3.3.5.2 Steel Reinforcement details

There were 2 No. pier columns on either side of the river channel where the central span is supported.The columns sizes were 750x600mm.


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The reinforcement details as gathered through electromagnetic method revealed 8 no.32mm diameter re-bars in each column. The average covers were varying at different points on the faces of each column with the lowest at 40 mm and highest at 70 mm.


The concrete strength as measured through rebound (Schmidt) hammer method recorded average strengths of 55 N/mm2 and 62 N/mm2 for Nyahururu side and 48N/mm2 and 54.0N/mm2 for Nyeri side.

The concrete matrix was generally homogeneous as revealed through ultrasonic method. The quality of concrete was also found to be good through direct transmission mode of ultrasonic pulses where an average velocity of 4.2 km/s was recorded.

BRIDGE AT KM 84+5203.3.5.4 Concrete matrix Deterioration for pier columns

The highest carbonation depth recorded was 3 mm indicating a remaining good cover of 37mm (least cover recorded was 40mm. This was an indication of low level deterioration.

Probability of corrosion activity was insignificant as indicated by a high resistivity potential of 111.6 kΩcm.

3.3.5.5 BEARINGSThe bearing type is elastomeric of approximate size400x280x30mm. They were in good condition.


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Photo 14: Showing a bridge bearing for bridge at km 84+520

3.3.6 OTHER BRIDGE FITTINGSThe guard rails were in good condition.

photo 15:showing bridge fittings for bridge at km 84+52

3.4 BRIDGE AT KM 102+510The structure comprises a composite deck with 5 no. steel beams, wall type RC abutments and wing walls.


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Photo 16: showing a side view of bridge at km 102+510

3.4.1 ABUTMENTS3.4.1.1 Visual inspection for the Abutments

Four vertical cracks running from approximately quarter the height of the abutment downwards were found on the Nyeri side abutment. The cracks appeared along a line approximately midway between the beam supports at the abutment cap. The crack widths varied from 0.4-1.2mm.

Fig 6: sketch showing crack profiles for Nyeri side abutment for bridge at km 102+510

Two vertical cracks from approximately mid height down wards were found on the Nyahururu side abutment. The cracks appeared along a line approximately midway between the two RHS beam supports and between the LHS and centre beam supports.DETAILED INSPECTION REPORT FOR BRIDGES ALONG ROAD B5

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Fig 6: sketch showing crack profiles for Nyahururu side abutment for bridge at km 102+510

Photo 17: showing a vertical crack on an abutment wall for bridge at km 102+510

There was scouring of the Nyeri side abutment bottom level up to 1400mm high reducing the re-bar covers along this line which is mostly submerged when water levels are high.

Photo 19: showing a scoured surface at the bottom of the abutment for bridge at km 102+510

BRIDGE AT KM 102+510


The reinforcement details as gathered through electromagnetic method revealed the distribution of the reinforcement bars in the abutment walls on


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either side of the bridge to be uniform in the vertical and horizontal directions. The vertical re-bars were 25 mm in diameter at an average spacing of 450mm while the horizontal were 16 mm diameter at an average spacing of 400mm. The average covers were varying at different points on either abutment with the lowest at 26 mm and highest at 60 mm.


The concrete strength as measured through rebound (Schmidt) hammer method recorded strengths of between 40.0 N/mm2 to 59.0N/mm2.




3.4.1.5 Concrete Deterioration for the abutments

The highest carbonation depth recorded was 4mm indicating a remaining good cover of 22mm (least cover recorded was 26mm), see table ... for calculation of balance of carbonation depth).This was an indication of low level deterioration.



3.4.2 DECK SLAB3.4.2.1 Visual inspection of the Deck


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Deck slab thickness was 200mm.There were several multi directional cracks appearing from the soffit of the deck. The cracks were distributed all over the deck soffit. There were two major cracks that ran full width on either half of the Nyeri side and Nyahururu side of the deck at approx1, 500 mm from the transverse bracing. There were leakage stains along these cracks, an indication that the cracks were through hence the risk of exposure of re-bars to corrosion due to water ingress at the locations. (See photos below).

Photo 20: showing cracks on the deck slab of bridge at km 102+510

Maximum crack width was 0.8 mm.

3.4.2.2 Steel Reinforcement details for the Deck Slab

The reinforcement details gathered through electromagnetic method revealed that the distribution of the reinforcement bars in the deck slab to be uniform in the longitudinal and transverse directions. The longitudinal re-bars were 20 mm in diameter at an average spacing of 400mm while the transverse were 16 mm diameter at an average spacing of 300 mm. The average covers were 45 mm and 60mm for longitudinal and transverse re-bars respectively. 3.4.2.3 Concrete strength, quality and homogeneity for the Deck Slab


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The concrete strength measured through rebound (Schmidt) hammer method recorded an average strength of 55.5N/mm2.

The concrete matrix was inhomogeneous as revealed through ultrasonic method. This could be attributed to numerous multi directional cracks on the deck slab soffit.




The highest carbonation depth recorded was 5mm indicating a remaining good cover of 40mm (least cover recorded was 45mm). This was an indication of no deterioration.


3.4.3 WING WALLS3.4.3.1 Visual Inspection of Wing Walls

There were no visible structural defects on the wing walls

3.4.3.1 Steel Reinforcement Details for wing walls

The reinforcement details gathered through electromagnetic method revealed the distribution of the reinforcement bars in the wing walls on either side of the bridge to be uniform in the vertical and horizontal directions. The vertical re-bars were 20 mm diameter at an average spacing of 500mm while the horizontal were 16 mm diameter at an average spacing of 400mm. The average covers were varying at different points on either side with the lowest at 29 mm and highest at 55 mm.



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3.4.3.2 Concrete strength, quality and homogeneity for Wing Walls

The concrete strength as measured through rebound (Schmidt) hammer method recorded strengths between of 49.0N/mm2 to 60.0N/mm2.


3.4.4 STEEL GIRDERS 3.4.4.1 Visual

There were spots of paint peeling off on the bracings and beams

Photo 21: showing a point where paint has peeled off a bottom flange plate of a girder for bridge at km 102+510

There was accumulation of soil at the abutment caps which covered the bottom flanges of the steel girders causing the paint to peel off resulting in early stages of corrosion.



3.4.4.2 Ultrasonic Plate Thickness Tests for Steel Girders




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3.4.4.3 BEARINGSThe bearing type was elastomeric of approximate size300x280.30 and were in good condition.

3.4.4.4 OTHER BRIDGE FITTINGSThe guard rails were intact and in good condition.

Photo 22: showing the guardrails for bridge at km 102+510

3.5 BRIDGE AT KM 125+670


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This is a three span structure comprising a composite deck with 5 no. steel girders which are continuous through the three spans, wall type RC abutments, and wall type RC piers .There were no wing walls-gabion boxes had been used instead.


3.5.1 ABUTMENTS3.5.2 Visual Inspection of Abutments

The abutments could not be accessed due to protection works (stone pitching)

3.5.3 DECK SLAB3.5.3.1 Visual inspection of the Deck Slab

Deck slab thickness was 200mm.There were numerous (dense) multi directional cracks appearing from the soffit of the deck. The cracks were distributed all over the deck soffit. There were two major cracks that ran full width on each quarter of the span at the transverse bracings.

There were leakage stains along these cracks, an indication that the cracks were through hence the risk of exposure of re-bars to corrosion due to water ingress at the locations.(see photos below)


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Photo 23: showing cracks on the deck slab of bridge at km 125+670

Vibrations could be felt midspan upon movement of vehicles on the deck.


3.5.3.2 Steel Reinforcement details for the deck slab

The reinforcement details gathered through electromagnetic method revealed that the distribution of the reinforcement bars in the deck slab to be uniform in the longitudinal and transverse directions. The longitudinal re-bars were 20 mm in diameter at an average spacing of 400mm while the transverse were 12 mm diameter at an average spacing of 300 mm. The average covers were 25mm and 45 mm for longitudinal and transverse re-bars respectively.


The concrete strength measured through rebound (Schmidt) hammer method recorded a strength ranging between 40N/mm2 to 46.0N/mm2.

The concrete matrix was slightly inhomogeneous as revealed through ultrasonic method. This could be attributed to cracks on the deck slab soffit.

3.5.3.4 Crack depths for the Deck Slab

The crack depths were ultrasonically and visually determined and found to be through cracks at the widest points.


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3.5.3.5 Concrete Deterioration for the Deck Slab

The highest carbonation depth recorded was 4mm indicating a remaining good cover of 21mm (least cover recorded was 25 mm).This was an indication of low level deterioration.


3.5.4 PIER WALLS3.5.4.1 Visual inspection of the Pier Walls

There were two vertical cracks on the Nyeri side pier wall.

The protection works near the bases of the pier walls and for the Nyeri side back fill were damaged.

The walls’ thicknesses were 600mm.

3.5.4.2 Steel Reinforcement Details for the Pier Walls

The reinforcement details gathered through electromagnetic method revealed the spacing of the reinforcement bars in the pier walls on either side of the bridge to be uniform the vertical and horizontal directions at 300 and 450 mm respectively. The vertical re-bars were 25 mm in diameter while the horizontal were 16 mm .The average covers were varying at different points on either side with the lowest at 40 mm and the highest at 67 mm.


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BRIDGE AT KM 125+6703.5.4.3 Concrete Strength, Quality and Homogeneity of the pier walls

The concrete strength measured through rebound (Schmidt) hammer method recorded an average strength of 51.0N/mm2and 53.0 N/mm2 for Nyeri and Nyahururu side respectively.

The concrete matrix was generally homogeneous as revealed through ultrasonic method. Direct transmission of ultrasonic pulses gave an average ultrasonic velocity of 4.3 km/s, an indication of good quality concrete.

3.5.5 STEEL GIRDERS 3.5.5.1 Visual Inspection of Steel Girders

The paint had peeled off the bottom flanges of the steel girders near the abutment supports.

Photo 24: showing paint peeling off the bottom flange and web pates

Three bracings-two on Nyeri side and one on Nyahururu side-were missing, probably stolen. The beams were reachable near the abutments making it easy for vandals to remove bolts and steal the bracings.

Photo 25: Showing a missing bracing on bridge at km 125+670

There were no critical welded joints along the entire length of the girders.


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3.5.6 BEARINGS

The bearings were elastomeric measuring 400x280x 30 mm and were in good condition.

Photo 26: Showing a bridge bearing for bridge at km 125+670


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3.6 BRIDGE AT KM 142+450(NEAR MWEIGA TOWNSHIP)The structure comprises a composite deck with 5 no. steel beams, wall type RC abutments and wing walls.

Photo 27: showing a side view of bridge at km 142+450

3.6.1 ABUTMENTS3.6.1.1 Visual inspection of the Abutments

Three vertical cracks running mid-way the height from the abutment cap were found on the Nyahururu side abutment. One of the cracks appeared approximately midway between the two RHS beam supports while the other one propagated from the centre beam support at the abutment cap downwards.

Photo 28: Showing a vertical crack on the abutment wall for bridge at km 142+450

The maximum crack width was 1.1 mm


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BRIDGE AT KM 142+450(NEAR MWEIGA TOWNSHIP)3.6.1.2 Steel Reinforcement details for the Abutments

The reinforcement details gathered through electromagnetic method revealed the distribution of the reinforcement bars in the abutment walls on either side of the bridge to be uniform in the vertical and horizontal directions. The vertical re-bars were 25 mm in diameter at an average spacing of 450mm while the horizontal were 16 mm diameter at an average spacing of 400 mm. The average covers were varying at different points on either abutment wall with the lowest at 27 mm and highest at 67 mm.

3.6.1.3 Concrete strength, quality and homogeneity for The Abutments

The concrete strength measured through rebound (Schmidt) hammer method recorded strengths of between 54 N/mm2 to 64 N/mm2.

The concrete matrix was homogeneous except for LHS of Nyahururu side, though with no visible defects on the surface. This infers the likelihood of internal defects within the concrete matrix at the tested location.





Probability of corrosion activity was insignificant as indicated by high resistivity potential 111.5.


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BRIDGE AT KM 142+450(NEAR MWEIGA TOWNSHIP)3.6.2 DECK SLAB3.6.2.1 Visual inspection of the deck slab

Deck slab thickness was 200mm.There were longitudinal cracks propagating from both Nyeri side and Nyahururu side towards the middle of the span.

Photo 29: showing longitudinal cracks on the deck of bridge at km 142+450

There were also other multi directional cracks distributed on the deck slab soffit.

Maximum crack width was 1.0mm.

There was lime like substance on the surface of the deck slab soffit which appeared prominently along the location of the re-bars forming a similar pattern to that of the re-bars layout.

Photo 30: showing lime stains on the deck soffit


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BRIDGE AT KM 142+450(NEAR MWEIGA TOWNSHIP)3.6.2.3 Steel Reinforcement details for the Deck Slab

The reinforcement details gathered through electromagnetic method revealed the distribution of the reinforcement bars in the deck slab to be uniform in the longitudinal and transverse directions. The longitudinal re-bars were 20 mm diameter at an average spacing of 400mm while the transverse were 12 mm diameter at an average spacing of 300 mm. The average covers were 45mm and 33 mm for longitudinal and transverse re-bars respectively.


The concrete strength as measured through rebound (Schmidt) hammer method recorded an average strength of 53.3N/mm2 (see details at various point in table no....)





The highest carbonation depth recorded was 6mm indicating a remaining good cover of 27mm .This was an indication of low level deterioration.

Probability of corrosion activity was insignificant as indicated by high resistivity potential of 111.3.


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BRIDGE AT KM 142+450(NEAR MWEIGA TOWNSHIP)3.6.3 WING WALLS3.6.3.1 Visual inspection of the Wing Walls

There were no visual structural defects on the wing walls


The reinforcement details gathered through electromagnetic method revealed the spacing of the reinforcement bars in the abutment walls on either side of the bridge not to be uniform in both vertical and horizontal directions varying between 300mm- 450mm and 400-450mm respectively. The vertical re-bars were 20 mm diameter while the horizontal were 16 mm diameter the average covers were varying at different points on either abutment with the lowest at 40 mm and the highest at 68 mm.

3.6.3.3 Concrete strength, quality and homogeneity for the wing walls

The concrete strength measured through rebound (Schmidt) hammer method recorded strengths between 55.0N/mm2 to 62.0 N/mm2.

The concrete matrix was slightly inhomogeneous as revealed through ultrasonic method.

3.6.4 STEEL GIRDERS 3.6.4.1 Visual inspection of Steel Girders

There were spots of paint peeling off on the beams signalling early stages of corrosion. The LHS girder had a large spot where paint had peeled off on the bottom flange.


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Photo 31: showing spots of paint peeling off from the steel girders

BRIDGE AT KM 142+450(NEAR MWEIGA TOWNSHIP)

There was accumulation of soil at the abutment caps covering the bottom flanges of the steel girders causing the paint to peel off resulting in early stages of corrosion.

The bolts and nuts for the joints were in good condition.


3.6.4.2 Thickness tests


3.6.5 BEARINGSThe bearing type was elastomeric of size 400x280x 30 mm and was in good condition.

Photo 32:showing a bridge bearing for bridge at km 142+450


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3.7 BRIDGE AT KM 173+120(MARUA)This is a three span structure comprising a composite deck with 4 no. steel girders for each span, column type RC abutments and column type RC piers

Photo 33: a side view of bridge at km 173+120

3.7.1 ABUTMENTS3.7.2 Visual Inspection of the abutments

The abutments could not be accessed due to gabion box protection works

Photo34: showing gabion boxes which prevented access to the abutment columns

3.7.3 DECK SLAB


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3.7.2.1 Visual Inspection of the Deck Slab

The deck slab is in good condition. No structural defects were visible

BRIDGE AT KM 173+120(MARUA)3.7.2.2 Steel Reinforcement details for the Deck Slab

The reinforcement details gathered through electromagnetic method revealed that the distribution of the reinforcement bars in the deck slab to be uniform in the longitudinal and transverse directions. The longitudinal re-bars were 16 mm diameter at an average spacing of 150mm while the transverse were 12 mm diameter at an average spacing of 130 mm. The average covers were 20 mm and 10mm for longitudinal re-bars and transverse re-bars respectively.


The concrete strength measured through rebound (Schmidt) hammer method recorded an average strength of between 30.0 N/mm2 and 55.0 N/mm2.

The concrete matrix was slightly inhomogeneous as revealed through ultrasonic method.

3.7.2.4 Concrete Deterioration of the Deck Slab

The highest carbonation depth recorded was 3mm indicating a remaining good cover of 4mm (least cover recorded was 6 mm).This was an indication of high level deterioration. It should be noted that the little balance of effective good cover is contributed to by small initial covers and not due to deep carbonation.



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3.7.3 STEEL GIRDERS 3.7.3.1 Visual inspection of steel girders

The girders were generally in good condition along the spans. There was accumulation of soil through the expansion joint at the abutment caps which upon removal revealed a serious corrosion attack for the bottom flanges, mounting bolts, anchor plates and stiffening plates at the abutment caps supports.

BRIDGE AT KM 173+120(MARUA)The Nyeri side girders’ mounting bolts, stiffener plates and the anchor plates were severely corroded and had started to peel off. See photos below.

Photo 35: showing corrode mounting bolt and bottom flange plate

Photo 36: showing a corroded mounting bolts and a stiffening plate.


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Photo 37: showing corroded mounting bolt ,nut ,bottom flange plate and stiffener plate. Notice the peel off

BRIDGE AT KM 173+120(MARUA)Corrosion at early stages was also observed at the mid span joints.

See photo below


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Photo 38: showing corrosion at early stages at the midspan joint

3.7.4 PIER COLUMNS

3.7.4.1 Visual inspection of pier columns

The pier columns are generally in good condition.


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Photo 39: showing a column pier for bridge at km 173+120

BRIDGE AT KM 173+120(MARUA)3.7.4.2 Steel Reinforcement details for Pier Columns

There were 4 No. pier columns on either side of the river channel where the central span is suspended.The columns sizes were 450x600mm.The reinforcement details as gathered through electromagnetic method revealed 8 No.32mm diameter re-bars in each column. The average covers were varying at different points on the faces of the columns with the lowest at 18mm and highest at 36 mm.The links were spaced at 250mm.

3.7.4.3 Concrete strength, quality and homogeneity for Pier Columns


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The concrete strength measured through rebound (Schmidt) hammer method recorded average strengths of 32 N/mm2 and 45 N/mm2 for Nyeri side and 43.0N/mm2 and 55.0N/mm2 for Karatina side. The concrete matrix was generally homogeneous as revealed through ultrasonic method. The quality of concrete was also found to be good through direct transmission of mode of ultrasonic method where an average ultrasonic pulse velocity of 4.4 km/s was recorded.

3.7.4.4 Concrete Deterioration for Pier Columns

The highest carbonation depth recorded was 6 mm indicating a remaining good cover of 12mm (least cover recorded was 18mm).This was an indication of medium level deterioration.


3.7.4.5 BEARINGS

The bearing type was found to be steel plate laminations which had started to corrode.


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photo 40& 41:showing laminated metallic bearing on the Nyeri side abutment cap support

4.0 CONCLUSIONSFrom the results obtained, the following conclusions can be made:

i. There is severe cracking of the deck slabs


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ii. The steel girders for the structures except bridge at km 173+120 are in good condition but may need repainting.

iii. The concrete strengths recorded for the structural elements are structurally okay.

iv. The concrete covers for the abutments and wing walls vary considerably at different points on these structural elements.

v. The danger of re-bar corrosion is minimal except at locations where the crack depths are greater than the concrete covers where water can get to the re-bars.

vi. There is adequate effective good cover for steel reinforcement bars-carbonation effect is minimal except forbridge at km 173+120 deck slab.

vii.The bearings for the structures are in good condition-except for bridge at km 173+120

viii. The deck slab forbridge at km 173+120 is in good conditionix. The steel girders for bridge at km 173+120(Marua Bridge) are

damaged by corrosion at the abutment capsupport. This is the same case with the mounting bolts and anchor plates-immediate attention is needed.

5.0 RECOMMENDATIONS1) An action plan is needed to address the following

i. Cracking on the deck slabs and abutmentsii. Damaged protection works for bridge at km125+670iii. Vandalism and theft of bracings for bridge at km 125+670iv. Lime accumulation for bridge at km 142+450.v. Severe corrosion of anchor plates, mounting bolts and bottom

flange edges at the abutment caps for bridge at km 173+120vi. Damage or lack of bearings for bridge at km 173+120

2) Development of a periodic inspection plan to monitor any further deterioration or performance of any rehabilitation worksthat may be implemented in response to no.1 above.


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3) The custodians of the structuresshould maintain proper records for the structures in future to enable comparison of status during inspection and original design requirements.

6.0 TESTS DONE

Seven tests were done namely:


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i) Visual Inspection to ascertain the extent of wear and tear of the structure.

ii) Ultrasonic Test to determine the homogeneity, quality, and internal defects in the concrete matrix.

iii) Ultrasonic test to determine steel plate thicknesses and test for delamination.

iv) Electromagnetic Test to establish the steel reinforcement details for reinforced concrete.

v) Schmidt Hammer Test to determine the concrete strength insitu.

vi) Carbonation test to determine the effective good cover to the reinforcement.

vii) Resistivity potential to determine the probability of corrosion of the re-bars.

4.1 Test Method Principles4.1.1 Visual InspectionVisual Inspection is used in maintenance of facilities, inspection of equipment and structures using either or all of human senses such as vision, hearing, touch and smell. Visual Inspection typically means inspection using human senses and/or any non-specialized inspection equipment.

4.1.2 Schmidt Hammer TestThis method is based on the principle that the rebound of an elastic mass depends on the hardness of the surface that it strikes. The rebound number obtained from the Schmidt Hammer is correlated with


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concrete cube crushing strength, whose calibration curves for 7 days and 28 days curing periods are contained in the digital instrument

4.1.3 Electromagnetic TestThis method is employed for locating steel in concrete using an Electromagnetic Covermeter. The principle method of test is by electromagnetic induction. When a probe carrying an alternating field is brought close to steel, eddy magnetic fields are generated by the steel, which reduces the primary field of the probe. At maximum induction level depicted by audio signals and reduction in minimum cover measurement, the location and orientation of a reinforcement bar can be established. After appropriate calibration, the technique is used to determine concrete cover, location and diameter of reinforcement bars (when reinforcement bars are parallel to the surface of the probe).Normally, closely packed reinforcement bars influence the accuracy of this method while determining the bar size. The accuracy of the method employed for bar size determination is ±2mm. 4.1.4 Ultrasonic Pulse velocity Test

The velocity of ultrasonic pulses traveling through a solid material depends on the density and the elastic properties of that material. Ultrasonic pulse velocity testing using low frequency pulses of 54 kHz is employed as a Non Destructive testing technique to determine the quality and homogeneity of concrete. This is given by the velocity at which the pulses will travel through the concrete. Regions of cracks or damaged material will have a corresponding reduction in the pulse velocity due to their high acoustic impedance.


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In this case two modes of transmission were employed namely:

a) Direct transmission to determine the pulse velocity in km/s hence the quality of concrete.

b) Indirect transmission method was employed to determine the homogeneity of concrete. A straight line graph of transit time against distance indicates a homogeneous concrete matrix. Deviations from the straight line are indications of inhomogeneity.

4.1.5 Carbonation Test.

The drilling method is used to determine the depth of carbonation. The drilled out material at prescribed depth is then analyzed for carbonation using phenolphthalein reagent. Presence of carbonation is depicted by no color change while the color changes to pink in the absence of carbonation.

A deterioration degree is judged based on the balance of carbonation depth as shown in the table below.

Based on this table, the degree of reinforcement corrosion is “None” for the results of tests having more than 30 mm depth for the balance of carbonation depth.

Table 2: Evaluation of Carbonation Depth

Deterioration degree

Balance of Carbonation Depth

Degree of reinforcement

corrosionHigh T < 0 mm Large

Medium 0 mm ≤ T < 10 mm MediumLow 10 mm≤ T < 30 mm LowNone 30 mm≤ T None

Note: Balance of Carbonation Depth = Cover – Carbonation DepthDETAILED INSPECTION REPORT FOR BRIDGES ALONG ROAD B5

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4.1.6 Reinforcement Corrosion Investigation (Resistivity potential method)

The time at which corrosion of steel may commence and the rate at which it may proceed is dependent upon the properties of the cement paste and the permeability of the concrete. Since the electrical conductivity of concrete is an electrolysis process, which takes place by ionic movement in the aqueous pore solution of the cement matrix, it follows that a highly permeable concrete will have a high conductivity and low electrical resistance.

The knowledge of the electrical resistance of concrete can provide a measure of the possible corrosion of steel embedded in it as shown below

Table 3: Resistivity Level vs Possible Corrosion Rate

Resistivity Level(k ohm cm) Possible Corrosion Rate<5 Very high

5-10 high10-20 moderate to low>20 insignificant


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DETAILED RESULTS DATA SHEETS


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BRIDGE AT KM 60+030ABUTMENTSElectromagnetic test results for the abutments

Test Element/Location Re-bar spacing(mm)

Average covers(mm)

Re-bar size(mm)

Abutment wall

Thickness(mm)

A1 –Nyeri Side

At abutment cap

LHS Vertical:350Horizontal:400

Vertical:45Horizontal:65


700

Centre Vertical:450Horizontal:400



RHS Horizontal:480Horizontal: 400

Vertical: 35Horizontal:60


Along the middle line







RHS Horizontal:480Horizontal: 400



A2 –Nyahururu Side

At abutment cap







RHS Horizontal:380Horizontal:450










RHS Horizontal:400Horizontal:400



Schmidt Hammer Test Results for the Abutments

Test Element/LocationAverage concrete

strength (N/mm2)

A1 –Nyeri SideAt abutment cap

LHS 49.5Centre 53.1

RHS 53.1


LHS 41.3Centre 44.1

RHS 44.0


At abutment capLHS 54.0

Centre 48.0RHS 44.0


LHS 48.0Centre 43.0

RHS 45.0


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BRIDGE AT KM 60+030Ultrasonic Pulse Velocity Results for the Abutments

Test Element/Location Homogeneity of concrete matrix

A1 –Nyeri Side

LHS Homogeneous Centre Homogeneous

RHS HomogeneousLHS Homogeneous

Centre HomogeneousRHS Homogeneous


LHS HomogeneousCentre Homogeneous



Carbonation Test Results for the AbutmentsTest

Element/LocationCarbonation

depth(mm)

Least cover recorded

(mm)

Balance of carbonation

depth(mm)

Remarks

A1-Nyeri side 6 35 29Low

deterioration degree

A2-Nyahururu side 6 33 27

Resistivity Test Results for the AbutmentsTest

Element/LocationResistivity

(kΩcm)Remarks

A1-Nyeri side 111.3 Probability of corrosion is insignificant

A2-Nyahururu side 111.5

Crack Profiles for the AbutmentsTest

Element/Location

Crack no.

Crack length(mm)

Crack width(mm)

Crack depth(mm)

A1-Nyeri sideCr.1 Full height of the

abutment wall1.4 160

Cr.2 Full height of the abutment wall

0.8 76

A2-Nyahururuside

Cr.1 Full height of the abutment wall 0.8 70


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BRIDGE AT KM 60+030DECK SLABElectromagnetic Test Results for the Deck Slab

Test Location Re-bar spacing(mm)

Average covers(mm)

Re-bar size(mm)

Deck slab Thickness

(mm)

DS1-Nyeri Side Longitudinal:400Transverse:300

Longitudinal:50Transverse:35


250DS3-Nyahururu side




Schmidt hammer Test Results for the Deck Slab

Test LocationAverage concrete strength

(N/mm2)

DS1-Nyeri Side 56.1

DS2 –Mid Span 59.6DS3-Nyahururu side

62.0

Ultrasonic Pulse Velocity Results for the Deck SlabTest Element/Location Homogeneity of concrete matrix

DS1-Nyeri SideNot homogenous-transmission of ultrasonic pulses not consistent

DS2-Nyahururu side Not homogenous-transmission of ultrasonic pulses not consistent

Carbonation Test Results for the Deck SlabTest

Element/Location

Carbonation depth(mm)


(mm)


depth(mm)

Remarks

DS1-Nyeri Side 6 35 29Low deterioration degree

DS3-Nyahururu side 6 37 31


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BRIDGE AT KM 60+030DECK SLABResistivity Test Results for the Deck Slab

Test Element/Locatio

n

Resistivity (kΩcm)

Remarks

DS1-Nyeri Side111.2

Probability of corrosion is insignificantDS2-Nyahururu

side109.1

Crack profiles For the Deck SlabTest

Element/Location

Crack no.

Crack length(mm)

Crack width(mm)

Crack depth(mm)

DS1-Nyeri side Cr.1 9.9-Full width 1.0 Through crackDS3-Nyahururu side

Cr.1 9.9-Full width 1.0 Through crack

WING WALLSElectromagnetic Test Results for the Wing Walls

Test Element/Location

Re-bar spacing(mm)

Average covers(mm)

Re-bar size(mm)

Nyeri Side LHS Vertical:380Horizontal:460



Nyahururu Side LHS




Schmidt Hammer Test Results for the Wing Walls

Test Element/LocationAverage concrete strength

(N/mm2)Nyeri Side

LHS 56.0

Nyahururu Side LHS 60.0

Ultrasonic Pulse Velocity Results for the Wing WallsTest Element/Location Homogeneity of concrete

matrix


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Nyeri Side LHS Homogeneous

Nyahururu Side LHS

BRIDGE AT KM 60+030Carbonation Test Results for the Wing Walls


n



(mm)


depth(mm)

Remarks

Nyeri side 6 26 20Low deterioration degreeNyahururu side

6 31 25

Resistivity test results for the Wing WallsTest

Element/Location

Resistivity (kΩcm)

Remarks

Nyeri side 110.2Probability of corrosion is insignificant

Nyahururu side108.2


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BRIDGE AT KM 60+030STEEL GIRDERSUltrasonic Tests for Plate Thickness & Lamination for steel girders

Steel Girder No.

Section Dimensions (mm)

Continuity Across Plate Thickness

SG1 LHSNo Delamination



22.7

13.7

600

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Steel Girder No.



SG3 CentreNo Delamination

SG2 RHSNo Delamination


22.6

14.5

600

22.4

14.0

600

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Steel Girder No.





22.5

14.0

600

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BRIDGE AT KM 84+520-NDARAGWAABUTMENTSElectromagnetic test results for the abutments


Average covers(mm)

Re-bar size(mm)

Abutment wall

Thickness

(mm)

A1 –Nyeri Side

At abutment cap




770Centre Vertical:470Horizontal:370



RHS Vertical:480Horizontal:360














At abutment cap




770



















strength (N/mm2)


LHS 51.7Centre 41.1

RHS 54.9


LHS 54.1Centre 48.8

RHS 53.8


At abutment capLHS 48.1

Centre 55.7RHS 52.5


LHS 57.6Centre 53.3

RHS 54.9


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BRIDGE AT KM 84+520Ultrasonic Pulse Velocity Results for the Abutments


A1 –Nyeri Side









Element/Location


Least cover

recorded

(mm)

Balance of carbonatio

n depth(mm)

Remarks/deterioration degree

A1-Nyeri side 3 32 29 Low A2-Nyahururu side 3 36 33 None



(kΩcm)Remarks

A1-Nyeri side111.7

Probability of corrosion is insignificantA2-Nyahururu side 111.5


Element/Location

Crack no.

Crack length(mm)

Crack width(mm)

Crack depth(mm)

A1-Nyeri side Cr.1 2000 0.8 25A2-Nyahururuside

Cr.1 1500 1.0 27Cr.2 1500 0.6 22


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Average covers(mm)

Re-bar size(mm)

Deck slab Thickness

(mm)




220DS3-Nyahururu side






(N/mm2)

DS1-Nyeri Side 46.0

DS2-Nyahururu side 47.9


DS1-Nyeri SideSlightly inhomogeneous

DS2-Nyahururu side Slightly inhomogeneous


Element/Location



(mm)


depth(mm)

Remarks/degree of

deterioration

DS1-Nyeri Side 3 24 21 lowDS2-Nyahururu

side 3 33 30 low


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n

Resistivity (kΩcm)

Remarks

DS1-Nyeri Side 110.7 Probability of corrosion is insignificantDS3-Nyahururu

side 110.9

Crack Profiles for the Deck SlabTest

Element/Location

Crack no.

Crack length(mm)

Crack width(mm)

Crack depth(mm)

DS1-Nyeri side Cr.1 Full width 1.2Through cracksCr.2 Full width 1.0

DS2-Nyahururu side

Cr.1 Full width 1.2Cr.2 Full width 1.2


Test Element/LocationRe-bar spacing

(mm)Average covers(mm)

Re-bar size(mm)

Nyeri Side RHSVertical:470

Horizontal:450Vertical:40


Horizontal:16

Nyahururu Side LHSVertical:350

Horizontal:260,370Vertical:60


Horizontal:16



(N/mm2)

Nyeri SideRHS 56.4

LHS 54.0

Nyahururu Side

LHS 53.9

RHS 55.0


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BRIDGE AT KM 84+520Ultrasonic Pulse Velocity Results for the Wing Walls


Nyeri SideLHS Homogeneous

RHS Homogeneous

Nyahururu Side LHS Homogeneous

RHS Homogeneous


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BRIDGE AT KM 84+520STEEL GIRDERSUltrasonic Tests for Plate Thickness & Lamination

Steel Girder No.






23.5

14.2600

23.7

14.2

600

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Steel Girder No.






22.6

14.3600

22.3

14.1

600

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Steel Girder No.





22.4

13.9600

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BRIDGE AT KM 84+520PIER COLUMNSElectromagnetic Test Results for the Pier Columns

Test element /location

Column Size(mm), No. & Arrangement of re-bars

Re-bar size

(mm)

Average covers(mm)

Link Details(mm)

PC 1-Nyeri sideLHS 32

Side A:50Side B:63Side C:70Side D:55

size:10Spacing:300

PC 2-Nyeri sideRHS 32


size:10Spacing:300


D

200 200

250250

600

750

A

B

C

D

D

200 200

250250

600

750

A

B

C

D

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BRIDGE AT KM 84+520Test

element /location

Column Size(mm), No. & Arrangement of re-bars

Re-bar size

(mm)

Average covers(mm)

Link Details(mm)

PC 1-Nyahururu

sideLHS

32Side A:58Side B:56Side C:51Side D:60

size:10Spacing:300

PC 1-Nyahururu

sideLHS

32Side A:55Side B:56Side C:50Side D:50

size:10Spacing:300


B

D

200 200

250250

600

750

A

B

C

D

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BRIDGE AT KM 84+520Schmidt Hammer Test Results for the Pier Columns


(N/mm2)

Nyeri SideRHS 55.0

LHS 61.6

Nyahururu Side

LHS 48.0

RHS 54.0

Ultrasonic Pulse Velocity Results for the Pier Columns for homogeneityTest Element/Location Homogeneity of concrete matrix

Nyeri Side

LHS Homogeneous

RHS Homogeneous

Nyahururu Side LHSHomogeneous

RHSHomogeneous

Ultrasonic Pulse Velocity Results for the Pier Columns for quality of concrete

Test Element/LocationTransit

time(µs)

Distance (mm)

Pulse velocity(km/s)

remarks

Nyeri SideLHS 144 600 4.16 Good quality

concreteRHS 148 600 4.05

Nyahururu Side LHS 137 600 4.40

RHS 142 600 4.22

Carbonation Test Results for the Pier ColumnsTest

Element/Location


Least cover

recorded

(mm)


n depth(mm)



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Nyeri side 3 49 46 None Nyahururu side

3 40 37

BRIDGE AT KM 84+520Resistivity Test Results for the Pier Columns


n

Resistivity (kΩcm)

Remarks

Nyeri side111.6

Probability of corrosion is insignificantNyahururu side

111.6


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BRIDGE AT KM 93+380ABUTMENTSElectromagnetic Test Results for the Abutments


Average covers(mm)

Re-bar size(mm)

Abutment wall

Thickness(mm)

A1 –Nyeri Side

At abutment cap




700




RHS vertical:450Horizontal:440










RHS Vertical :450Horizontal:420




At abutment cap




700



















strength (N/mm2)


LHS 45.5Centre 60.3

RHS 43.2


LHS 57.6Centre 43.8

RHS 44.2

A2 –Nyahururu At abutment cap

LHS 40.1Centre 58.7

RHS 48.2


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Side Along the middle line

LHS 51.1Centre 56.2

RHS 45.8

BRIDGE AT KM 93+380ABUTMENTSUltrasonic Pulse Velocity Results for the Abutments


A1 –Nyeri Side


RHS HomogeneousRHS Homogeneous



RHS HomogeneousCentre Homogeneous

RHS Homogeneous


Element/Location


Least cover

recorded

(mm)


n depth(mm)


A1-Nyeri side 5 30 25 Low A2-Nyahururu side 5 28 23 Low



(kΩcm)Remarks

A1-Nyeri side110.8

Probability of corrosion is insignificantA2-Nyahururu side 110.4


Element/Location

Crack no.

Crack length(mm)

Crack width(mm)

Crack depth(mm)

A1-Nyeri sideCr.1 Full height of

abutment wall 1.0 61


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Cr.2 Full height of abutment wall 1.0 60



BRIDGE AT KM 93+380Crack Profiles for the Abutments


n

Crack no.

Crack length(mm)

Crack width(mm)

Crack depth(mm)

A2-Nyahururuside

Cr.1 Full height of abutment wall

1.055


Cr,3 Full height of abutment wall 0.6 33

DECK SLABElectromagnetic Test Results for the Deck Slab


Average covers(mm)

Re-bar size(mm)

Deck slab Thickness

(mm)




200DS2 –Mid Span




DS3-Nyahururu side




Schmidt Hammer Test Results for the Deck Slab


(N/mm2)

DS1-Nyeri Side 54.5

DS2 –Mid Span 56.6




MTRD ICT

DS1-Nyeri SideHomogeneous

DS2 –Mid SpanHomogeneous

DS3-Nyahururu side Homogeneous

BRIDGE AT KM 93+380Carbonation Test Results for the Deck Slab


n


Least cover

recorded(mm)


depth(mm)

Remarks/degree of

deterioration

DS1-Nyeri Side 5 34 29 Low

DS2 –Mid Span 5 35 30DS3-Nyahururu

side 5 34 29

DECK SLABResistivity Test Results for the Deck Slab


n

Resistivity (kΩcm)

Remarks

DS1-Nyeri Side 106.8 Probability of corrosion is insignificant

DS2 –Mid Span 108.8DS3-Nyahururu

side 110.2

Crack profiles For the Deck SlabTest

Element/Location

Crack no.

Crack length(mm)

Crack width(mm)

Crack depth(mm)

DS1-Nyeri side Cr.1 11600-full width 1.0 Through crackDS3-Nyahururu side

Cr.1 11600-full width 1.0 Through crack

WING WALLSElectromagnetic Test Results for the Wing WallsDETAILED INSPECTION REPORT FOR BRIDGES ALONG ROAD B5

MTRD ICT

Test Element/LocationRe-bar spacing(mm)

Average covers(mm)

Re-bar size(mm)

Nyeri Side LHSVertical:450Horizontal:350



Nyahururu Side RHSVertical:450Horizontal:350



BRIDGE AT KM 93+380Schmidt Hammer Test Results for the Wing Walls


(N/mm2)

Nyeri Side LHS 57.9

RHS 57.7

Nyahururu Side RHS 65.0

LHS 60.2

Ultrasonic Pulse Velocity Results for the Wing WallsTest Element/Location Homogeneity of concrete matrix

Nyeri SideLHS

Homogeneous

RHSHomogeneous

Nyahururu Side LHSHomogeneous

RHSHomogeneous


MTRD ICT


Steel Girder No.






22.1

14.2

600

22.0

14.2

600

MTRD ICT

BRIDGE AT KM 93+380Steel Girder

No.Section Dimensions

(mm)Continuity Across

Plate Thickness




22.5

14.0

600

22.4

14.2

600

MTRD ICT




Plate Thickness



22.1

14.0

600

MTRD ICT

BRIDGE AT KM 102+510ABUTMENTSElectromagnetic Test Results for the Abutments


Average covers(mm)

Re-bar size(mm)

Abutment wall

Thickness(mm)

A1 –Nyeri Side






















(N/mm2)

A1 –Nyeri Side

LHS 59.1Centre 57.7

RHS 51.0Side A2 –Nyahururu

LHS 40.8Centre 52.4

RHS 55.8

ABUTMENTSUltrasonic Pulse Velocity Results for the Abutments


A1 –Nyeri Side


RHS Homogeneous



RHS Homogeneous


MTRD ICT

BRIDGE AT KM 102+510Carbonation Test Results for the Abutments



Least cover

recorded(mm)


depth(mm)



A2-Nyahururu side 4 30 26 Low



(kΩcm)Remarks

A1-Nyeri side110.8

Probability of corrosion is insignificant



Element/Location

Crack no.

Crack length(mm)

Crack width(mm)

Crack depth(mm)

A1-Nyeri side Cr.1 1400 0.4 20Cr.2 1400 0.7 33Cr.3 1400 1.2 42Cr.4 1400 1.2 40

A2-Nyahururuside

Cr.1 2000 0.8 35Cr.2 2000 1.0 38



Average covers(mm)

Re-bar size(mm)

Deck slab Thickness

(mm)



Longitudinal:20Transverse:16 200


MTRD ICT

DS2 –Mid SpanLongitudinal:400Transverse:300



DS3-Nyahururu side




BRIDGE AT KM 102+510Schmidt hammer Test Results for the Deck Slab


(N/mm2)

DS1-Nyeri Side 55.4


54.6


DS1-Nyeri SideInhomogeneous

DS2 –Mid SpanInhomogeneous

DS3-Nyahururu side Inhomogeneous


Element/Location


Least cover

recorded(mm)


depth(mm)


DS1-Nyeri Side 5 30 25 Low

DS2 –Mid Span 5 45 40None


None



n

Resistivity (kΩcm)

Remarks


MTRD ICT

DS1-Nyeri Side110.8


DS2 –Mid Span110.8

DS3-Nyahururu side

110.8

BRIDGE AT KM 102+510Crack profiles For the Deck Slab


n

Crack no.

Crack length(mm)

Crack width(mm)

Crack depth(mm)

DS1-Nyeri side Cr.1 Full width of the deck

0.8 Through

DS3-Nyahururu side

Cr.1 Full width of the deck

0.8 Through



Average covers(mm)

Re-bar size(mm)

Nyeri Side RHSVertical:500Horizontal:400



Nyahururu Side LHSVertical:500Horizontal:450





(N/mm2)

Nyeri SideRHS

59.1

LHS60.1

Nyahururu Side

LHS48.8

RHS55.8


Nyeri Side

LHS Homogeneous

RHS HomogeneousHomogeneous


MTRD ICT

Nyahururu Side LHS

RHSHomogeneous


Steel Girder No.





MTRD ICT





Plate Thickness



22.7

14.1

600

21.9

14.3

600

MTRD ICT





Plate Thickness



22.4

14.0

600

MTRD ICT



Average covers(mm)

Re-bar size(mm)

Deck slab Thickness

(mm)




200DS2 –Mid Span




DS3-Nyahururu side




Schmidt Hammer Test Results for the Deck Slab


(N/mm2)

DS1-Nyeri Side 40.2


MTRD ICT


46.5






Element/Location


Least cover

recorded

(mm)


n depth(mm)


DS1-Nyeri Side 4 25 21Low


None



n

Resistivity (kΩcm)

Remarks

DS1-Nyeri Side112.3



side 110.8

Crack Profiles for the Deck SlabTest

Element/Location

Crack no.

Crack length(mm)

Crack width(mm)

Crack depth(mm)


MTRD ICT

DS1-Nyeri side Cr.1 Full width of the deck

1.0

Through cracks

Cr.2 Full width of deck

1.0

DS2-Mid span Cr.1 Full width of deck

0.8


1.0

DS3-Nyahururu side


1.0


1.0


Steel Girder No.




MTRD ICT



BRIDGE AT KM 102+510Ultrasonic Tests for Plate Thickness & Lamination

Steel Girder No.




22.5

13.5

600

MTRD ICT




Steel Girder No.




21.5

13.4

600

MTRD ICT


BRIDGE AT KM 102+510PIER WALLSElectromagnetic Test Results for the Pier Walls


MTRD ICT


Average covers(mm)

Re-bar size(mm)

Pier wall Thickness

(mm)

Nyeri SideRHS



Vertical:25 Horizontal:16

600







Nyahururu Side

LHSVertical:300Horizontal:450









Schmidt Hammer Test Results for the Pier Walls


(N/mm2)

Nyeri Side

RHS 50.0

Centre 52.4

LHS 51.0

Nyahururu Side

LHS 53.8

Centre 56.4

RHS48.1

Ultrasonic Pulse Velocity Results for the Pier WallsTest Element/Location Homogeneity of concrete matrix

Nyeri Side

LHS Homogeneous

Centre Homogeneous

RHS Homogeneous

Nyahururu SideLHS

Homogeneous

Centre Homogeneous

RHSHomogeneous

BRIDGE AT KM 102+510Ultrasonic Pulse Velocity Results for the Pier walls for quality of concrete

Test Element/Location Transit time

Distance (mm)

Pulse velocity(km/s)

Remarks


MTRD ICT

(µs)

Nyeri Side LHS 133 600 4.5 Good quality concrete

Nyahururu Side LHS 139 6004.3

Carbonation Test Results for the Pier WallsTest

Element/Location


Least cover

recorded(mm)


depth(mm)


Nyeri side 8 48 40None

Nyahururu side 4 42 38None

Resistivity Test Results for the Pier WallsTest

Element/Location

Resistivity(kΩcm)

Remarks

Nyeri side 111.3 Probability of corrosion is insignificant

Nyahururu side 112.3

BRIDGE AT KM 142+450ABUTMENTS


MTRD ICT

Electromagnetic Test Results for the Abutments


Average covers(mm)

Re-bar size(mm)

Abutment wall

Thickness(mm)

A1 –Nyeri Side






















(N/mm2)

A1 –Nyeri Side

LHS 60.8Centre 64.8

RHS 63.9Side A2 –Nyahururu

LHS 60.7Centre 60.9

RHS 54.6

ABUTMENTSUltrasonic Pulse Velocity Results for the Abutments


A1 –Nyeri Side


RHS Homogeneous



RHS Homogeneous

BRIDGE AT KM 142+450Carbonation Test Results for the Abutments


MTRD ICT



Least cover

recorded(mm)


depth(mm)



A2-Nyahururu side 7 30 23 Low



(kΩcm)Remarks

A1-Nyeri side111.8




Element/Location

Crack no.

Crack length(mm)

Crack width(mm)

Crack depth(mm)

A1-Nyeri side Cr.1 3500 1.2 41Cr.2 3500 1.2 42Cr.3 2000 1.0 30


Test LocationRe-bar spacing

(mm)Average covers(mm)

Re-bar size(mm)

Deck slab Thickness

(mm)DS1-Nyeri Side Longitudinal:400

Transverse:300Longitudinal:41Transverse:29


200DS2 –Mid Span




DS3-Nyahururu side




BRIDGE AT KM 142+450Schmidt hammer Test Results for the Deck SlabDETAILED INSPECTION REPORT FOR BRIDGES ALONG ROAD B5

MTRD ICT


(N/mm2)

DS1-Nyeri Side 53.3

DS2 –Mid Span52.1







Element/Location


Least cover

recorded

(mm)


n depth(mm)


DS1-Nyeri Side 6.0 29 23 Low DS3-Nyahururu

side 6.0 30 24 Low



n

Resistivity (kΩcm)

Remarks

DS1-Nyeri Side110.0



side 111.1



MTRD ICT



Average covers(mm)

Re-bar size(mm)

Nyeri Side LHS Vertical:300Horizontal:300



Nyahururu Side LHSVertical:450



Horizontal:16



(N/mm2)

Nyeri SideRHS 59.4

LHS 62.0

Nyahururu Side

LHS 53.2

RHS 55.0


Nyeri Side

LHS Homogeneous

RHS Homogeneous

Nyahururu Side LHS Homogeneous

RHS Homogeneous

Carbonation Test Results for the Wing WallsTest

Element/Location


Least cover

recorded

(mm)


n depth(mm)


Nyeri side 7 33 28 LowNyahururu side

7 45 38 None


MTRD ICT

BRIDGE AT KM 142+450Resistivity test results for the Wing Walls


n

Resistivity (kΩcm)

Remarks

Nyeri side110.0

Probability of corrosion is insignificantNyahururu side 111.5


MTRD ICT


Steel Girder No.






14.5

25

600

MTRD ICT


Steel Girder No.






14.3

23.2

14.5

23.5

600600

MTRD ICT


Steel Girder No.




BRIDGE AT KM 173+120DETAILED INSPECTION REPORT FOR BRIDGES ALONG ROAD B5

14.0

22.4

600

MTRD ICT



Average covers(mm)

Re-bar size(mm)

Deck slab Thickness

(mm)

DS1-Nyeri SideRHS




DS2 –Nyeri Side Centre




DS3-Nyeri Side LHS






(N/mm2)

DS1-Nyeri Side LHS 30.7

DS1-Nyeri Side Centre 40.4

DS1-Nyeri Side RHS 55.2

DS2-Karatina side LHS 52.1

DS2-Karatina side Centre 51.3

DS2-Karatina side RHS 40.6


DS1-Nyeri SideRHS Slightly Inhomogeneous

DS2 –Nyeri Side Centre Slightly Inhomogeneous

DS3-Nyeri Side LHSSlightly Inhomogeneous


Element/Location


Least cover

recorded(mm)


depth(mm)

Remarks/Deterioration degree

DS1-Nyeri Side 6 10 4 High BRIDGE AT KM 173+120

DECK SLABDETAILED INSPECTION REPORT FOR BRIDGES ALONG ROAD B5

MTRD ICT

Resistivity Test Results for the Deck SlabTest

Element/Location

Resistivity (kΩcm)

Remarks

DS1-Nyeri Side 111.4Probability of corrosion is insignificant

PIER COLUMNSTest

element /location

Column Size(mm), No.& Arrangement of re-bars

Re-bar size

(mm)

Average

covers(mm)

Link Details(mm)



size:10Spacing:250



size:10Spacing:250

BRIDGE AT KM 173+120PIER COLUMNSDETAILED INSPECTION REPORT FOR BRIDGES ALONG ROAD B5

A

600

350

500

450

A

B

C

D

MTRD ICT

Test element /location

Column Size(mm), No.& Arrangement of re-bars

Re-bar size

(mm)

Average

covers(mm)

Link Details(mm)



size:10Spacing:250



size:10Spacing:250

BRIDGE AT KM 173+120Schmidt Hammer Test Results for the Pier Columns


A

600

350

500

450

A

B

C

D

A

600

350

500

450

A

B

C

D

MTRD ICT


(N/mm2)

Nyeri SidePC1LHS 45.0

PC2LHS 32.0

PC1RHS 41.8

PC2RHS 45.0

Karatina Side

PC1LHS 43.0

PC2LHS 50.0

PC1RHS 52.1

PC2RHS 55.0

Carbonation Test Results for the Pier ColumnsTest

Element/LocationCarbonation

depth(mm)

Least cover

recorded(mm)


n depth(mm)

Remarks/deterioration

degree

Nyeri sidePC1LHS 6 23 17 Low

PC2LHS 6 18 12 Low

PC1RHS 6 24 18 Low

PC2RHS 6 25 19 Low

Resistivity test results for the Pier ColumnsTest


(kΩcm)Remarks

Nyeri sidePC2 RHS 111.4


BRIDGE AT KM 173+120STEEL GIRDERSDETAILED INSPECTION REPORT FOR BRIDGES ALONG ROAD B5

MTRD ICT

Ultrasonic Tests for Plate Thickness & Lamination

Steel Girder No.







16.5

23

870

MTRD ICT

Steel Girder No.






16.5

23.5

16.0

22.5

870600

ROAD B5 BRIDGES INSPECTION DETAILED REPORT copy.docx

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