WET MIX MACADAM CONSTRUCTION-WMM CONSTRUCTION
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| WET MIX MACADAM CONSTRUCTION |
WET MIX MACADAM CONSTRUCTION
WET MIX MACADAM – INTRODUCTION
➤Wet Mix Macadam (WMM) Consist Of Laying And Compacting Clean,Crushed Graded Aggregate Granular Material, Premixed With Water To a dense mass on Prepared Sub Grade/Sub base/Base,
What is wet mix macadam?
What is full form of WMM?
What is wet mix macadam?
What is full form of WMM?
FUNCTIONS OF WET MIX MACADAM (WMM)
➤It Acts As A Binding Layer Between Granular Sub Base ( GSB) And The Bituminous Layer,Provides Structural Support to The Pavement And Help Dispersing Traffic Loads To The Layers Below,
➤It Is An Improvement Over Conventional Water Bound Macadam (WBM) Layer Because It Has A Superior Gradation Of Aggregates, Faster Rate Of Construction, Less Consumption Of Water,High Standard Of Densification And Higher Standard of Quality Achievable,
What is difference between WMM and WBM?
Why WMM is used?
What is difference between WMM and WBM?
Why WMM is used?
MATERIAL REQUIREMENTS FOR WET MIX MACADAM (WMM)
➤Crushed Stone,
➤If Crushed Gravel/Shingle Is Used Not Less Than 90 % of Its Weight Retained on 4.75 mm Sieve Shall Have At Least Two Fractured Faces,
➤Binders Such As Lime Stone Dust, Kankar Dust,
➤Screeners Such As Moorum, Crushed Over Burnt Bricks etc,
➤Shall Satisfy the grading Requirements as will be explained Shortly Please Continue to Read,
➤Shall Satisfy the physical Requirements as will be taken up Shortly Please Continue to Read,
GRADING REQUIREMENTS OF MATERIALS( in image below)
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| wet mix macadam aggregates |
PHYSICAL REQUIREMENTS OF MATERIALS( in image below)
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| WET MIX MACADAM MATERIALS PHYSICAL REQUIREMENTS |
MACHINERY REQUIREMENTS FOR WMM CONSTRUCTION
Following Machines are Required For Wet Mix Macadam Construction
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| Machines for WMM Contruction |
CONSTRUCTION OPERATION AT WET MIX MACADAM PLANT
MIXING OF WMM-
➤The Coarse Aggregates,Fine Aggregates And Water Shall be Mixed In The Mixing Plant, Which Shall Have Pug Mill of Suitable Capacity For Mixing,
➤The Plant Shall Have Different bin feeders for Different fractions Of Aggregates, Required to Arrive at Required Gradation,
➤Controlled water addition Mechanism shall be present to give continuous flow of mixed material that suits pavements requirements at site,
➤The individual fraction shall be loaded to the bins of mixing plant by front end wheel loader tippers from the stock yard,
➤Care shall be taken at stockyard and at the bin feeders to ensure that the aggregate should not be contaminated or mix with other fraction,
➤The aggregate for bottom 100 mm thick of stockpile shall not be fed in the plant bin,
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| WMM PLANT |
What is wet mix plant?
How is Wmm prepared?
What is WBM?
What is water bound macadam?
CONSTRUCTION OPERATION OF WMM WITH GRADER
➤The Toe line/fixing of pegs to marks the limits of WMM level shall be done before the commencement of work,
➤The Width of Pavements for Toe line shall be calculated by referring drawing with due considerations to formation width plus the offsets and slopes of different layers depth the current layer from the formation road level (FRL),
What is WMM layer?
HAULING AND DUMPING-
➤The Required Quantity Of Wet Mix Macadam(WMM) Shall Be Calculated and Informed To WMM Plant Engineer Of Staff Whoever is taking care of Production,
➤Dumping Pattern Such as to ensure uniform spread, shall be determined and explained to the person who is taking care of dumping at site,
➤The Material for WMM shall be hauled to site by tippers and dumped on the bed in predetermined pattern,
SPREADING AND GRADING-
➤The Materials shall be mechanically (grader etc.) spread in uniform layers such that compacted thickness not exceeding 200 mm or any other specified with due considerations to the loose thickness (Compaction Factor) of WMM,
➤Control pegs at every 10 m long C/L shall be fixed on both sides of the bed in such manner that they are not disturbed by grader movement,
➤Required Levels shall be marked on the pegs with suitable vertical offsets,
➤After rough initial spreading, a cotton/nylon string (line door) shall be held at marks on the control pegs at both sides,
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| WMM level fixing |
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| WMM Spreading And leveling with grader |
CONSTRUCTION OPERATION OF WET MIX MACADAM WITH PAVER
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| WMM Laying with Paver |
SPREADING/LAYING WITH PAVER –
➤Immediately after mixing WMM shall be transported to laying site by tippers and shall be spread uniformly and evenly upon the prepared prepared first layer of WMM or GSB layer with the help of a paver finisher,
➤However at the time of spreading the surface shall be checked for grade, camber and thickness with templates and high or low spots are to be rectified by removing or adding the fresh material of same properties,
JOINT PREPARATION-
➤The work shall be planned in a manner so as to reduce the number of joints to the minimum. A full width paver shall be used, if possible , to avoid longitudinal joint,
LONGITUDINAL JOINT-
➤Rolling Shall be done on a strip of approximately 150 mm to 200 mm width from the edge on which the joint is expected to come,
➤This strip shall be rolled along with the edge of next paver pass,
➤Rolling shall be done in such a manner that roller drum moves on both the previous and the new surface,
➤The evenness of joint shall be checked by a straight edge and rectification, if any shall be done immediately,
TRANSVERSE JOINT-
➤A straight edge shall be kept over the transverse edge of the previous work in such manner that the half of the straight edge is on old surface and another half hangs towards the side where new work has to be carried out,
➤Marks shall be given on the points from where the surface level has started coming down,
➤The old surface shall be cut from the points marked above and removed. the cut material can be reused,
➤After the paver has passed over the joint the new surface near the joint shall be trimmed and shaped slightly as required,
➤Roller shall transversely run over the joint such a manner that roller drum moves on both the previous and new surface,
➤ The evenness of the joint shall be checked by a straight edge and rectification , if any shall be done immediately,
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| transverse joint WMM Laying With Paver |
QUALITY CONTROL TESTS AND THEIR FREQUENCY
➤Gradation at a frequency of test for every 100 cum,
➤Atterberg berg limits at a frequency of test for every 100 cum,
➤MDD and OMC As per IS 2720 Part-8 at 1 test for Source,
➤Combined Flakiness and Elongation index 1 test for every 200 cum,
➤Aggregate impact value At a frequency of 1 test for every 200 cum,
➤Water absorption at a frequency of 1 test for source,
➤Density of Compacted layer at 1 test(6 pits)/500 sqm and 1 pit for additional 50 sqm or less,
➤Top level checking for given stretch,
PROBLEMS IN THE CONSTRUCTION OF WMM LAYER AND REMEDIES TAKEN
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