Saturday, May 5, 2012
The entire work: shall be constructed to the exact position and elevation in conformity to the lines and grades shown on the Drawings or as directed by the Engineer. The contractor shall provide his own men and instruments for determining alignment, elevation and position of all construction between any points, subject to the chock and correction by the Engineer,
11. 8. 2 Inspection
Examine the areas and conditions under which paving is to be installed and remedy any conditions decremental to the proper and timely completion of
the work. Do not proceed with the work until unsatisfied conditions have been corrected in an acceptable manner.
1. The formation level on embankments and in cuttings shall be the surfaces level of the underside of the subbase. The levels and tolerance or irregularity of surface shall be within the Unit specified Any permitted deviation below the true levels shall be made up in sub - base material compacted as specified which shall not be measured for payments.
2. Materials for the subgrade shall not contain harmfully amounts of water- soluble substances and shall be such that the strength and bearing capacity will not be adversely affected by the presence of water .
3. In the event of unsuitable material, the contractor shall remove such material to the depth indicated on the drawing or as directed by the Engineer and replaced with approved filling material compacted as specified herein.
4. The compaction shall be performed with suitable compacting component such pneumatic- tired Pollocks or macadam rollers. If necessary, vibrating rollers and shopfitter rollers may by used upon obtaining approval by the Engineer,
The subgrade shall be compacted to a demister not less than- 95% of the maximum dry density ( as determined by AASHTO T180-74) at optimum moister content. Compaction of the subgrodes adjacent to structures shall be carefully performed by an approved method which does not cause any damage to the structures. Degree of compaction of the completed subgracles shall be tested as specified hereinafter.
6. Surface of the subgrades shall extend to at least beyond either edge of the pavement r including the kerbs if any. The completed subgrades shall be protected from any damage.
7. The following tests shall be performed in accordance with ASTM, AASHTO or BS
or other approved standards: (i) Classification Tests
a. Specific gravity --- AASIITO (T1 60-74) or BS 1377 test 6 .
b. Mechanical analysis ---- MSIffO (TOG-77) or BS 1377 Test 7 c, Ligiiicl Iimi4. ---- AASHTO ( T09 -6G) or BS 1377 test 2
d. Plastic limit ---- MSIJTO (T90 -70) or BS 1377 test 3. e Hoififcure content ---- BS 1377 test 1
These tests shall be nade at n fata not loss than one test for every 1000m of the materials but not less than 3 tests in any cose,
(ii) Compaction tests
Compaction and density tests on the subgrades shall be made at a rate not less than one test 2 for every 300m2 of the surface area of the subgrades
The tests shall be on a random basis and cover the entire width of the section. Testing of any layer of construction will bo deemed acceptable providing 8 out of 10 consecutive tests are egual to or in excess of the minimum and the remaining 2 tests do not fall below the minimum by more than 20%.
11.8.4 Sub-Base course
1. Prios to construction of the sUbbase, the previously constructed subgrade surfaces shall be cleaned of all foreign substances . Any area of the subgrade having indoguate compaction or any deviation form the requirements specified shall be corrected by scarifying, removing and/or adding approved material, re - shaping and re - compacting to the raguired density and to the satisfaction of the Engineer.
2. Sub - basr shall be constructed only when weather conditions do not detrimentally affoct the quality of the finished formation.
3. The materials shall be transported with pneumatic tired vehicles to the area whore the subbase is to be constructed, and shall be mechanically spread in an appropriate thickness to obtain the refused compacted thickness .
4. Whore the subbase course thickness exceeds 20cm it may be constructed in two or more layers of equal thickness. No superimposed layer shall be placed before the previous layer has been approved by the Engineer.
5. Each layer shall be compacted to at least 95% of the maximum dfiy density at optimum moisture content as determined by MSHTO T180-74. water shall be applied during the compaction in such an amount as n.ecessary to obtain the specified density,
6. In all places not accessible to the rolling equipment, the materials shall be compacted thoroughly with approved mechanical or hand tampers to a density comparable to that obta-ined by rolling .
7. Surface of the finished subbase course at any point shall be properly shaped to a
smooth uniform surface and shall be not vary more than one (1) cm above or below the grode level shown on the drawing .
8, Tho subbase cours shall be constructed to the full width of the pavement inclusive of the foundation of kerbs in the above-mentioned thickness. Eteuva- tion for the foundation of the kerbs shall be carried out only after the full width of the base course, is compacted and approved by the Sigineer,
9. Grade and alignment central stakes shall be furnished set and maintained by the contractor, subject to checking by the Engineer . The work shall ponfim of the lines, grades and cross~ sections shown on the Drawings. The tolerance for level is +1 cm to 2 can .
10. The completed subbase course shall be main-trained in an acceptable condition at all times prior to the construction of the concrete surfacing . Tnaffic will not be permitted en the subbase during the raing season,
11. The following tests shall be executed, on preselected samples approved by the
Engineer in accordance with relevant AASIITO specifications.
A. Tests for materials
a. Mechanical analysis
b. LL, PL and PI
c. Moisture - density relation d. Modified CUR
These tests shall be made at rate not less than one tests for every 1000 cubic meters of each material or when deemed mecessarly , but not less than 3 tests in any case, Any Materials found not to conform with the requirements, than or later, will be cause for rejection. Unexcepatable materials shall be removed and exchanged with a suitable materials at no cost to the employer .
B. Tests for compacted subbase
Compaction and density tests on subbase shall be performed at a rate not less than one tost for every 300 square meters of surface area of the finished subbaso.
11.8.5 Concrete Surfacing
126.96.36.199 Form Construction
a. The side forms shall be placed to true vertical alignment . They shall be laid on a fcontinvous bed of cement nor tar'or lean concrete about 2 in thick. They shall be laid slightly high and brought to leved by taping down.
b. The forms shall be set to the roqiured grades and lines, rigidly braced and secured . The forns shall have not vertical or horizontal movement in excess of 2am when subjected to the load of the finishing machine, or from any other construction operation,
c. Install sufficient quantity of forms to allow continues progress of the work and so that forms can remain in place at least 24hours after concrete placement.
d. Check completed formwork for grade and alignment to the following tolerances:
1. Top of forms not more than 3mm in 3000 mm.
2. Vertical face on longitudinal axis, not more than 6mm in 3000mm.
e. The forms shall be cleaned thoroughly and oiled with form release agent as often as required to ensure separation from concrete without damage
f. Forms shall be laid at least one day ahead of Concreting
188.8.131.52 Polythene sheeting
Immediately before anjr concrete is placed, polythene sheeting as specified above shall be laid on the subbase over the entire area. The sheeting shall not torn or damaged when the concrete is placed thereon.The sheeting shall be lapped at least
30cm and any damaged sheeting shall be replaced at the contractor's
184.108.40.206 Fixing reinforcement
The number , size , form and pasition of all steel reinforcing bars and other parts shall be exact accordance with the drawings. They shall be kept in the correct positions of the forms without displacement during the process of working the concrete into place , The provision of spacer bars, supporting stools distance pieces if required shall be to the approval of the Engineer, but the responsibility for maintaining the reinforcement in the specified position during concreting
shall rest solely with the contractor. All steel reinforcement shall be cleard and free from all loose mill scale, dust, coating such as paint,cement , grout,…. etc , before the concrete is deposited
220.127.116.11 Concrete placement :
1, Comply with the reguirements of chapter ( 4 ) section. ( 6 ) for mixing and placing concrete and as herein specified.
2. Do not place concrete until subbase and forms have been checked for line and grade.
3. When concreting operations are about to start, the polythene sheeting on the base shall be in a finished condition, free of all forign and -unsuitable materials, not muddy, free from dust and dry earth or any rucking
4. Trucks delivering concrete shall not run on polythene sheeting -nor shall they run on completed slabs until at least 14 days after placing the concrete.
5. The concrete shall be tipped on to a banker board either to the side or on the formation level, and the material shovelled into position by hand.
6. Place and compact concrete in two layers, strike-off the initial pour for the entire width of placement and to the required depth below the finished surface as shown on the Drawing . Care shall be taken to avoid damaging the polythene sheeting during the laying of the lower layer .
7. Great care shall be taken to ensure complete compaction. Fetrol-driven vibrators mounted on a wooden or steel bean can be used for compaction or any other compacting devices approved by the Engineer.
8, The surface of the lower layer, after compaction shall be rough, free from laitance and free from surplus water to eneure complete bond with the upper layer. The
joining of the upper and the lower layers in no way creats a plane of weariness in the concrete pavement slab.
9. Steel fabric reinforcement shall, where it is reguired by the drawings, be placed on the surface of tlio lower layer of concrete with longitudinal and transverse overlaps not less than 40 tines the diameter of the bars transverse to the overlapped edge of the sheet, or 15cm whichever is the greater. The mats shall be clean and free from excessive rust. Keep flat and free of distortions.
10. The upper layer of concrete shall be placed before initial set develops in the lower layer, lower layer concrete initially set before placing the upper layer shall be entirely replaced. The upper layer of concrete shall deposited, spread and compacted, and finished to the reguired surface levels and finishes.
11. Spreading , compacting and finishing operations are to be completed without delay. Any concrete, which, has been in place too long before comply of these operations, is to be removed from the site .
12. Place concrete using methods which prevent segregation c of the max t consolidate concrete along the face of forms and adjacent to transverse joints with an internal vibrator. Keep vibrator away from joint assemblies, reinforcement, or side forms. Consolidate with care to prevent dislocation of reinforcements, dowels, and joint devices.
13. Deposit and spread concrete in a continuous operation between transverse joints, as for as possible. If interrupted for more than 1 ;2 hour,
14. When adjacent pavement lanes are placed in seperate operate, do not operate equipment on the until the pavement has attained sufficient strength to carry the loads without injury.
15. As soon as the side fonr.s are rer.iovedf the edges of the slab shall first be inspected by the Engineer. Any minor honeycombed n-reats shall then be filled in with mortar (1:2 ).
18.104.22.168 General :
Construct expansion, weakened plan a ( contraction), and construction joints as indicated on drawings and in accordance with the regruired specifications All joints shall be constructed true to-line with their faces perpendicular to surface of the pavement, unless otherwise indicated, Joints shall not vary more than 2cm from a true line or from their designated position. Transvers joints shall be at right angles to the centerline. When joining coasting structures, place transverse joints to align with previously placed joints, unless otherwise indicated,
22.214.171.124 Contraction joint :
Provide weakened plane ( contraction) joints, sectioning concrete into areas as shown on the Drawings Construct weakened - plane joints for a depth equal to at least 1 ;4 concrete thickness. The type of the joint may be as fellows:
a. Tooled joints : Form weakened - plane joints in fresh concrete by grooving top
portion with a recommended cutting tool and finishing edges with a jointer.
b. Sawed joints : Form weakened - plane joints using powered saws ecjuipped with shatterproof abrasive or diamondrinmed blades. Cut joints into hardened concrete as soon as surface will not be torn abraded, or otherwise damaged by cutting action.
c. Inserts : Use embedded strips of raetal or sealed wood to form weakened - plane joints.
Set strips into the plastic concrete and carefully remove strips after concrete has hardened.
126.96.36.199 Expansion joints :
shall be inctalled as indicated on the drawings. Provide provided joint filler for expansion joints, The expansion joints shall be located at distances not less than 30ft ( 97441x1) o.c, or as indicated on Drawings. Extend joint fillers full-width and depth of joint, and not less than 13mm or more than 25nn below finished surface where joint sealer is indicated. If no joint sealer, place top of joint filler flush with finished concrete surface. Joint fillers shall be furnished in one -piece lengths for the full width being placed, wherever possible. Inhere more than one length is required lace or clip joint filler sections together. The top edge of the joint filler shall be protected dnring concrete placeraent with a metal cap, wood strip, or other temporary material. Remove protection after concrete has been placed on both sides of joint. Concrete slab edge along the exrpansion joint shall be really finished with a slightly rounded edging tool.
188.8.131.52 Dowel Bars:
Dowel bars for expansion and contraction joints shall be placed on an axis paralled to the surface of the slab and to the centre line of the slab ( Parallel to the side forma).
One —half the dowels must be coated with grease of asphalt to break the bond with the concrete 00 that the dawel may slide freely. The dowels shall be free from indentations or other deformation and have ends.
184.108.40.206 Construction Jointsi
Place construction joints at the end of all pours at locations where placement operations are stopped
for a period of more than 1 ;2 hour except where such pour terminate at expansion joints and as shown on the drawing. The day work should normally begin and end at an expansion or contraction joint, and construction joints should be regarded as emergency joints and avoidsd, whenever Possible tide deformed tiebars to hold the joint tightly closed If the construction joint replace a contraction joint , dWals may be installed so that one end of each dowel bar is free to move, as shown on the Drawings,
Construction joints shall not be placed nearer then 10ft to an expansion or contraction joint,
220.127.116.11 longitudinal joints
Place longitudinal joints between adjacent traffic lanes. Tiebars shall be used at mid- depth of the slab.The tiebars diameter, length, and spacing are shown on the Drawings.
A sealing groove filled with sealing compound should be provided. The groove is formed by securing a chip of wood of the required size to the form vrher carting the first half width of the road. When the form is removed the strip of the Bread is left in position untit the second half of tlie road has been completed, and it is then removed. To prevent the development of cracking, transverse joint on each side of a longituchinal joint should be in line with one another and not staggered. Transverse joints should always be at right angles to the slab edges to avoid sideway movements of the slabs and the formation of diaginal cracking at the acut corners.
11 .8.6.7 Joint Filler
a. Suitable Materials for filling joints are soft knot — free timber; impregnated filreboard, cMpboard, cork and cellular rubber. Materials containing high proportion of bitumen should not be used. The material used shall comply with dwsion 1.3.4.
b. The filler board shall be placed vertically - or perpendicular to tho pavement surface on the line of the joint without any overlap* Mb gaps is allowed below it, between individual lengths or between it and the form, or previously laid concrete.
c. The filler board shall extend to the underside of the groova - forming strip of wood or metal in expansion joints. There shall be no gap between the filler and any such strip.
18.104.22.168 Joint sealing
a. Grooves for sealing construction joints shall be formed either by a strip of steel , hardwood or other approved material secured to the form, Grooves for contraction and expansion joints shall be formed by cutting the concrete after it has hardened sufficiently without risk of cracking or spalling.
All grooves sliall have square corners and the outside edges of pavements shall be finished with a 6mm radius.
b. All joint groovos in the concrete pavement ( excepting any joints incorporating synthetic rubber strip) shall be filled with a joint sealing compound as previously specified in division 1.3.5 and as shown on the drawings.
c. The grooves shall be continuous without blodcago.
d. In the case of expansion joint, the filler mstorial is to be exposed for the full length of the joint. Sefore filling all joint, grooves are to be dry and free form ust, concrete fragments or other deposited materials and shall be inspect by the Engineer before they are filled.
e. The sealing compound is to be heated and poured in accordance with the procedure recommended by the manufacturer, particular care being taken not to exceed the maxeraium temperature specified by the manufacturer,
f. Pouring shall be done by any approved method so that the sealer will fill the prescribed space to levels required without spiling on exposed surfaces of the
concrete. Any excess sealer shall be reraovod immediately in a manner which does not discolour nor injure the concrete o* the regaining sealer
g. Allow sufficient time for the seal to harden before traffic is permitted on the pavement,
h. Expansion joints shall be sealed 6,5 ran below ,-surface levelt contraction joints shall bo sealed J/aw below surface level; construction joints shall be sealed level with the surface .
11.8.7 Concrete Finishing
a, After striking- off and consolidation.of concrete, snooth the surface by screeding and flooting. Use hand methods
b. Finishing shall be carried out continuously over as long a length of concrete as passible. The finishing pass shall be made doss behind the compacting operation and the bea-i shall be tilted slightly so that the leading is about 3 ;8 higher than the trailing edge, to facilitate the striking off any small cfuantites of excess concrete. The mechanical finishers shall not allowed to remain too long in one position, and too many passes shall not made to avoid the formation of laitanco on the surface of concrete.
c. Use hand methods anly where mechanical floating is not possible. Adjust the floating to compact the surtace and produce a uniform liexture.
d. The foregoing work is to be carried out while the concrete is still plastic and workable and in such time sequence as to unsure the removal of water or laitance from the surface. Excess thin mortar, accumulating ahead of the finishing floats and straight - edges, shall be removed from the surface of the pavement, and shall not be used in filling depressions, Presh concrete shall be used to correct and fill all depressions.
e. After floating , test sixrface for triteness with 3m straightedge which shall be sheolced twice dailjc.
f. Work edges of slabs , formed joints, and top edge of curb with an edging tool. Care shall be taken to eliminate any tool marks on concrete surface ,
g. After completion of flooting, coajblete surface finishing as follows :
1. Brush finish , by drawing a fine - hair brush across concrete surface, perpendicular to a line of traffic. Repeat operation if repaired to provide a fine line texture acceptable to the Engineer.
2. 0n inclined slab surface, provide a coarse non - slip finish by scoring surface with a still- bristled broom perpendiclar to line of traffic.
h. The tine allowed to elapce between mixing the concrete in place shall not exceed
1 1 ;2 hours.
i. Do not remove ferns for 24 hours after concrete casting.
After removal , clean ends of joints and repair, any minor honeycombed areas.
11.8.8 Accuracy of surface finish.
a. The finished surface of tie road on the Drawings within a tolerance of + ;- 1 cm.
b. The gap between the bottom of the strength edge and the surface of the pavement shall not be groater than 3mm in any position and direction on the surface of the read.
c. There shall not be any deflection exceeding 1 cm from a straight line between any two prints 30 m apart longitudinally .