Wet Mix Macadam(WMM) work includes laying and compacting clean, crushed, graded aggregate and granular material, premixed with water, to a dense mass on a prepared GSB layer or existing pavement as per the requirement of the project. WMM can be laid in one or more layers, but the thickness of the single compacted layer not less than 75mm, and the maximum of 200mm when vibrating or other approved types of compacting equipment are used.
Plants, Equipment and Machinery for Wet Mix Macadam:
The following sets of plant and equipment are necessary for Wet Mix Macadam works.
- WMM plant – 01 No
- Loader – 1 No
- WMM Paver (Sensor) – 01 No.
- Motor Grader – 01 No
- Vibratory Rollers, capacity 80-100KN static wt – 2 Nos.
- Tipper/Dumpers, Cap – 10T/20T (As per site requirement)
- Plate compactor (as per site requirement)
Note: The above equipment deployment list is for single WMM setup, whereas the number of sets shall be mobilized as per the requirement of the program.
Material for Wet Mix Macadam:
Coarse aggregate The coarse aggregate shall be crushed stone of identified Quarry having the following physical characteristics. The material should conform to the physical requirement & strength contained at sub-clause 406.2.1.1of Technical Specification Contract. The aggregate for Wet Mix Macadam shall conform to requirements specified in the Table 400-10 of MORTH & Technical Specifications.
|Sl. no||Test||Test method to be followed as per||Requirement|
|1.||Los Angeles Abrasion Value or, |
Aggregate Impact Value
|IS 2386 (Part -4) |
IS 2386 (Part -4) or IS :5640
|40 % (Max.) |
|2.||Combined Flakiness and Elongation indices (Total)||IS : 2386 (Part -1)||30% (Max.)|
If the water absorption of the coarse aggregate is greater than 2.0%, the soundness test shall be carried out on the material as per IS: 2386 (Part-5).
A mix of crushed stone and aggregates shall be so proportioned so as to achieve the grading specified as per MORTH & Technical Specifications.
|IS Sieve Designation (mm)||Percent by weight passing the IS sieve|
|45||95 – 100|
|22.4||60 – 80|
|11.2||40 – 60|
|4.75||25 – 40|
|2.36||15 – 30|
|0.600||8 – 22|
|0.075||0 – 8|
The Proportioning shall be completed by determining the individual gradation of the individual ingredients and the blend determined by trial and error method to achieve the gradation specified. Wet Mix Macadam shall be constructed as per the MORTH Specifications, Clause– 406 and also as per change made to various Sub-Clauses in Clause–406 furnished in Contract Technical Specifications.
MDD & OMC shall be determined as per MORT&H clause 406 for the material so blended.
Mix design with the proportion of all materials, grading/test reports shall be submitted to Engineer, and a trial patch of appropriate length shall be constructed before the actual commencement of Wet Mix Macadam work. The trial patch shall be laid on an approved granular sub-base layer on the road alignment as approved by the Engineer. If the trial patch result does not meet the specified requirements, the same shall be redone unless the requirement is fulfilled.
In case of different gradation in the course of work, the proportion shall be suitably modified, and the same shall be furnished to Engineer for their approval.
Wet Mix Macadam Construction Operations:
Preparation of Base for WMM:
The surface to receive the Wet Mix Macadam layer shall be prepared to the specified lines and cross-fall (camber) and made free of dust and other extraneous material. Rain-cuts and surface irregularities if any shall be repaired before placing of WMM layer. Preparation of base shall be done as per Cl.404.3.1 of MORT&H technical specification.
Lateral Confinement of WMM Layer:
While constructing wet mix macadam, the arrangement shall be made for lateral confinement of the wet mix. This shall be completed by laying materials in adjacent shoulders along with that of WMM layer and following the sequence of operations described in clause 407.4.1 of MORT&H specifications.
Preparation of WMM Mix :
Suitable ingredients in required proportion shall be mixed with required OMC in a WMM mixing plant having provision of controlled addition of water and forced or positive mixing arrangements like pug mill or pan type of mixer of concrete batching plant.
Optimum moisture for mixing shall be obtained in accordance with IS: 2720(Part-8) after replacing the aggregate fraction retained on 22.40mm sieve with the material of 4.75mm to 22.4mm size. While adding water, the due allowance shall be made for the evaporation loss. However, during compaction, water in the wet mix shall not vary from the optimum value by more than agreed limit. The mixed material should be properly wet, and no segregation shall be permitted.
Transportation, Spreading, Compaction and Finishing:
- This shall be carried out as per the M.O.R.T&H Clause 406.3.4 & 406.3.5
- Mark the lines of WMM with lime powder or pegs on the completed GSB layer.
- The material shall be thoroughly mixed in the Wet Mix plant as per the approved mix formula.
- The material shall be loaded on to the dumpers directly from the wet mix plant for transporting to the WMM location.
- Lateral confinement shall be provided by laying the material for shoulder prior to commencement of wet mix laying operation as described above.
- The WMM shall be laid and compacted in two layers of uniform thickness as defined in the scope of work, and the compacted layer shall not be less than 75 mm and not more than 200 mm. The first layer shall be spread by Motor grader, whereas the second layer shall be spread with a Sensor Paver. The motor grader shall be capable of laying the WMM material uniformly all over the surfaces. Its blade shall have some hydraulic control suitable for initial adjustments and maintaining the same to achieve the specified slope and grade. The paver finisher shall be self-propelled having loading hoppers and distribution mechanism along with tamping & vibrating arrangement for compaction, control mechanism to ensure finished surface free from surface blemishes.
- Compaction of WMM shall start immediately after laying is completed. The compaction shall be completed with the help of vibratory compactor. The compaction pattern, including no of passes required, shall be finalized after full-scale trials at the site to achieve 98% of MDD determined as per IS: 2720 (Part-8).
- The general pattern shall be as follows:
a) Initial rolling – 2 static passes with Vibratory roller
b) Subsequent rolling – 4 vibratory pass
Note: One pass o roller shall include both forward and reverse movement. The roller speed shall not exceed 5Km/Hr.
- The compaction shall commence from the lower edge and shall move to upper edge width by width. Roller shall progress parallel to the centerline of the road, uniformly over-lapping each preceding track by at least 1/3rd width until the total area/surface has been rolled. Alternate trips of the vibratory roller shall be terminated in stops at least one meter away from any preceding stop. Quality control tests shall be carried out prior to the commencement of the next layer.
- The second layer of WMM shall then be laid to limits and compacted.
- After the final compaction of WMM, the same shall be allowed to dry for 24 Hours.
- The surface of WMM shall have a suitable cross fall to enable efficient surface drainage. The finished level WMM shall be within the tolerance limits specified in Table 900-1. (i.e +10 mm to –10mm).
- Requirements contained at Sub-Clause 406.4 of MORTH Technical Specification of the contract (Opening to traffic) should be adhered to. Vehicular traffic of any kind of heavy movement should not be allowed on the finished WMM top surface till it has dried and the wearing course is laid.
- During the period of construction, the arrangement of traffic shall be made as per Cl. 112 of MORTH technical specification.