Retrofitting For The Slab of An Existing Warehouse On PLOT L.R NO.11880/11 - NAIROBI

RETROFITTING FOR THE SLAB
OF AN EXISTING WAREHOUSE ON
PLOT L.R NO.11880/11 NAIROBI
--------------------------------------------------------------------PROPOSALS & COST ESTIMATES

----------------------------------------------------------------------
CLIENT
CHANDARIA INDUSTRIES LTD
P.O. Box 30621-00100
NAIROBI
CONSULTANT
LEEDS ENGINEERING LTD
P. O. Box 64785-00620
NAIROBI
JULY, 2016
Retrofitting of the Chandaria Structure.

Outline Methodology.
Based on the information provided and our understanding of the parameters of the
required work the proposal can be divided into the following sections;
1. Site Visit the objective being as follows:
a) To gain a full understanding of the working environment and scope of
work.
b) Source locally available materials and plant.
c) Decide on access scaffolding requirements.
d) Programme and plan the work around the clients needs.
2. Mobilization.
a) Appoint and brief all human resources on the objectives and
deliverables.
b) Plan the work and reserve the necessary plant and equipment.
c) Liaise with the clients representative regarding safety and access
requirements.
d) Provide a works programme.(Ms Project)
e) Plan and liaise with the necessary parties for inductions, medicals and
safety.
3. Site Establishment.
a) Establish personnel and equipment on site.
b) Construct site storage facilities.
c) Hoard off site camp and store area.
d) Reticulate power and water from the clients sources.
e) Set in place a project specific quality control plan.
f) Survey and photograph the entire structure and agree on the work to
be completed at each section.
4. Implementation and Method statement.
Proceed with the work in accordance with the agreed programme. More
specifically, undertake the various work items in accordance with the following
procedures.
5. Procedures.
Gaps which have occurred at the intersection of structural members:
a) Ascertain the need for installing temporary propping to create
redundancy while the members are being repaired.
b) Mark out and record/photograph.
c) Decide if the junction requires articulation(movement)
d) If no articulation is required, break out defective and misplaced
concrete until sound concrete is encountered and the joint has been
exposed taking care not to damage embedded steel reinforcing.
e) If articulation is required, re-instate joint and jointing materials.
f) Check that exposed steel is correctly placed.
g) Erect timber shutters.

h) Pre wet the area to be repaired.
i) Cast in or pump in structural grout either bulked or un
bulked(dependent on the size of the repair)
j) After 12-24 hours, strip the shutters and cure the new work.
6. Crack Repairs.
a) A low viscosity structural epoxy will be injected into pre-positioned
injection ports spaced evenly along each crack or joint.
b) Mark out and record/photograph.
c) Protect the area adjacent to the work with plastic sheeting.
d) Remove existing finishes such as plaster and tiles and dispose offsite.
e) Prepare the crack line by routing and cleaning out with air.
f) Install injection ports.
g) Chock the remaining surface of the crack with a thixotropic epoxy.
h) Pump structural epoxy into the crack, via the injection ports, until
refusal.
i) Remove the injection ports and grind the epoxy to the level of the
adjacent brickwork.
7. Spall and Patch Repairs.
a) The following procedures refer to smaller areas of defective concrete
where it is not practical to erect timber forms or shutters.
Preparation and breaking out of defective concrete.
b) Hammer test the relevant concrete surfaces and mark all hollow and
defective areas and record.
c) Break out defective concrete until sound concrete is encountered. The
breaking out should extend to a minimum of 10 mm behind reinforcing
bars.
d) Remove corrosion deposits from all exposed reinforcing by wire
brushing.
e) In case the extremities of each repair area to a minimum depth of
10mm to avoid featheredges when the repair mortal is applied.
f) Pressure wash to remove all dust and contaminants generated by the
previous activities.
g) Apply a passivating premier to all exposed reinforcing taking care to
coat the entire circumference of each exposed bar.
h) Pre wet the concrete substrate.
i) While the substrate is still wet, mix and apply multiple layers of the
specified repair mortar to the level and profile of the adjacent unrepaired concrete.
j) Apply curing compound to all repaired areas. The curing compound
should be compatible with any prescribed anti carbonation coatings.
Larger areas will be repaired by shutter and cast methods.
9. Lack of cover
The general lack of cover can have serious implications regarding the durability of
reinforced concrete in an urban environment.
The lack of physical cover can be compensated by the application of a Migration
Corrosion Inhibitor (MCI) together with a cementitious anti carbonation coating.
The MCI is applied directly onto the concrete after pressure washing. The chemistry
of the product facilitates the permeation of the MCI through the concrete and onto the
steel reinforcement, where a gamma ferric layer forms, and providing ongoing
protection from corrosion.
10. Protective Coatings
The durability of the concrete is further enhanced by the application of a cementitious

anti carbonating coating. The coating forms a flexible seal on the surface of the
concrete and prevents waterborne pollutants from entering the matrix, while allowing
transmission of vapor from within during the curing process. The added benefit of this
coating is that it helps provide a uniform colour and texture after the patch repair
work has been completed.
The protective coatings are aimed at the following;
i.
ii.
iii.
Arresting further corrosion of the embedded reinforcement by the use of a

Migrating Corrosion Inhibitor (MCI).
Preventing water, carbon dioxide and soluble salts and acids from entering
the pore structure of the concrete, thereby preventing electrolytic corrosion
from initiating within the concrete. This is achieved by applying two coats of a
cementitious waterproofing coating.
Furthermore, the cementious waterproof coating will provide a fairly uniform
grey colour after completion of the various patch repairs.
11. Coating Procedures.

The entire surface will be pressure washed and or gift blasted.
The surface will be inspected and blow holes or omegas will be filled with a
proprietary skim mortar.
iii.
Apply the coatings in accordance with the manufacturers recommendations
by spray or brush technique.
i.
ii.
The above presents the intended procedures for the proposed concrete remedial
works. These procedures may vary in accordance with site conditions.
Repair products.
All products will be selected from the Fosroc, or Sika range of concrete repair
materials.
END OF OUTLINE PROPOSALS.
RETROFITTING FOR THE SLAB OF AN EXISTING WAREHOUSE ON PLOT NO. 11880/11

IN NAIROBI FOR CHANDARIA INDUSTRIES LTD
SUMMARY OF COSTS
Item
Description
1 Mobilization of Equipment and personnel on site
2.1
Unit
Lumpsum
420,000.00
Strengthening of Structural Frame of Warehouse

D4 along Gridlines 2-3 & B-E
Concrete Slab works - Recasting and
strenghtening affected areas
Lumpsum
2.2
Beams Strengthening
Lumpsum
2.3
Columns Strengthening
Lumpsum
Total Costs
Extra works
Subtotal
VAT 16%
GRAND TOTAL
Lumpsum
783,700.00
2,399,690.00
235,000.00
60,000.00
3,898,390.00
623,742.40
4,522,132.40
RETROFITTING FOR THE SLAB OF AN EXISTING WAREHOUSE ON PLOT NO. 11880/11 IN

NAIROBI FOR CHANDARIA INDUSTRIES LTD
No
ESTIMATE BILL OF QUANTITIES

TASK DESCRIPTION
Units
Qty
Rate
Price (Kshs.)
CONCRETE SLAB ( Gridline 2-3 & B-E)
1
2
3
4
5
Repair sections
Agree and mark out weak / failed concrete
sections.
Carefully demolish failed concrete
Clean exposed reinforcement with wire
brush
Recast affected areas with Concrete class
25, 250mm thick; including provision of
formork
Curing of new concrete sections
SM
25.00
SM
25.00 5,000.00
LM
250.00
70.00
10.00
SM
25.00 5,200.00
SM
25.00
50.00
1,750.00
125,000.00
2,500.00
130,000.00
1,250.00
Concrete Strengthening by carbon fibre

laminates
1
Mark out laminate positions.
LM
160.00
10.00
Scabble 50mm wide slots along marked

laminate positions.
LM
160.00
440.00
LM
160.00
10.00
LM
160.00
90.00
3
4
Clean with vacuum cleaner to remove all

dust.
Mix and apply epoxy resin to slots and
laminates.
Place and secure laminates in position.
LM
160.00 2,700.00
Clean off excess epoxy and make neat.
LM
160.00
Sub-total
20.00
1,600.00
70,400.00
1,600.00
14,400.00
432,000.00
3,200.00
783,700.00

No

TASK DESCRIPTION
Units Qty
Rate
Price (Kshs.)
BEAMS ( Gridline 2-3 & B-E)
Cracks
Removal of existing finishes such as plaster
and dispose off-site.
Prepare the crack line by routing and cleaning
out with air.
Install injection ports
Chock the remaining surface of the crack with
a thixotropic epoxy.
Pump epoxy into the crack via injection
ports,untill refusal.
Remove injection ports and grind the epoxy to
the level of the adjacent concrete.
SM
5.00
440.00
2,200.00
LM
10.00
440.00
4,400.00
LM
10.00
150.00
1,500.00
LM
10.00 22,065.00
220,650.00
LM
10.00
2,010.00
20,100.00
LM
10.00
50.00
500.00
LM
442.00
10.00
4,420.00
LM
442.00
440.00
194,480.00
10 Clean with vacuum cleaner to remove all dust. LM
442.00
10.00
4,420.00
LM
442.00
90.00
39,780.00
LM
LM
442.00 2,700.00 1,193,400.00

442.00
20.00
8,840.00
SM
60.00
440.00
26,400.00
SM
SM
60.00
60.00
10.00
1,600.00
600.00
96,000.00
SM
60.00
8,040.00
482,400.00
SM
60.00
70.00
4,200.00
19 Apply top coat of epoxy resin.
SM
60.00
940.00
56,400.00
20 Cast silica sand onto the wet epoxy surface.
SM
60.00
650.00
39,000.00
2
3
4
5
6
7
9
Concrete Strengthening by carbon fibre

laminates
Mark out laminate positions.
Scabble 50mm wide slots along marked
laminate positions.
Mix and apply epoxy resin to slots and

laminates.
12 Place and secure laminates in position.
13 Clean off excess epoxy and make neat.
11
Concrete strengthening (Wrapping)

14
15
16
17
18
Scabble beam sides on either end to a rough

open texture finish.
Clean with vacuum cleaner to remove all dust.
Mix and apply poxy resin to prepared
surfaces.
Apply the wrapping fabric in the wet epoxy
resin and saturate.
Remove excess air and secure.
Sub-total
2,399,690.00

No
TASK DESCRIPTION
Units
Qty
Rate
Price (Kshs)
COLUMNS - (Gridline 2-3 & B-E)
Concrete strengthening (Wrapping of

columns, 1 metre below slab)
1
Scabble column sides on either end to a

rough open texture finish.
SM
20
440.00
8,800.00
Clean with vacuum cleaner to remove all dust. SM
20
10.00
200.00
SM
20
1,600.00
32,000.00
SM
20
8,040.00 160,800.00
SM
SM
SM
20
20
20
3
4
5
6
7
Mix and apply poxy resin to prepared

surfaces.
Apply the wrapping fabric in the wet epoxy
resin and saturate.
Remove excess air and secure.
Apply top coat of epoxy resin.
Cast silica sand onto the wet epoxy surface.
Sub-total
70.00
940.00
650.00
1,400.00
18,800.00
13,000.00
235,000.00
Notes
General
All works to be carried out only between gridlines 2-3 & B-E
Godown to be provided empty wihout any stored materials.
Client to provide areas for dumping demolished materials.
Slab
All areas to be demolished to be agreed before hand
Reinforcement assumed to be intact, No additional reinforcement allowed for
Recasting to be done with concrete class 25
Soffits of new slabs to be strenghtened with 50mm wide carbon fibre laminates
spaced at 600mm c/c one direction only
Beams
Beams to include 50mm x 5metres of laminate per metre of beam
Wrapping to be done only on beams with cracks
Columns
Wrapping to be done on the top part, 1 metre, to strenghten the column.
Single wrap to be used per column
Extra works
They include;
Hacking of existing plaster to place the laminates and wraps
12mm thick cement sand (1;3) plaster to: stripped plaster and apply 3 coats
emulson paint to the stripped section.
Allow for Helsian clothe to contain the dust within the affected area.

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RETROFITTING FOR THE SLAB

--------------------------------------------------------------------PROPOSALS & COST ESTIMATES

Retrofitting of the Chandaria Structure.

g) Erect timber shutters.

The durability of the concrete is further enhanced by the application of a cementitious

Arresting further corrosion of the embedded reinforcement by the use of a

11. Coating Procedures.

END OF OUTLINE PROPOSALS.

RETROFITTING FOR THE SLAB OF AN EXISTING WAREHOUSE ON PLOT NO. 11880/11

1 Mobilization of Equipment and personnel on site

Strengthening of Structural Frame of Warehouse

RETROFITTING FOR THE SLAB OF AN EXISTING WAREHOUSE ON PLOT NO. 11880/11 IN

ESTIMATE BILL OF QUANTITIES

CONCRETE SLAB ( Gridline 2-3 & B-E)

Concrete Strengthening by carbon fibre

Mark out laminate positions.

Scabble 50mm wide slots along marked

Clean with vacuum cleaner to remove all

Place and secure laminates in position.

Clean off excess epoxy and make neat.

RETROFITTING FOR THE SLAB OF AN EXISTING WAREHOUSE ON PLOT NO. 11880/11 IN

ESTIMATE BILL OF QUANTITIES

BEAMS ( Gridline 2-3 & B-E)

10 Clean with vacuum cleaner to remove all dust. LM

442.00 2,700.00 1,193,400.00

19 Apply top coat of epoxy resin.

20 Cast silica sand onto the wet epoxy surface.

Concrete Strengthening by carbon fibre

Mix and apply epoxy resin to slots and

Concrete strengthening (Wrapping)

Scabble beam sides on either end to a rough

RETROFITTING FOR THE SLAB OF AN EXISTING WAREHOUSE ON PLOT NO. 11880/11 IN

COLUMNS - (Gridline 2-3 & B-E)

Concrete strengthening (Wrapping of

Scabble column sides on either end to a

Clean with vacuum cleaner to remove all dust. SM

Mix and apply poxy resin to prepared

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