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SPECIFICATIONS/ QUALITY REQUIREMENTS PERTAINING TO CONSTRUCTION OF SUB-GRADE/ SUB-BASE/ BASE/ BT WORKS IN FLEXIBLE PAVEMENTS By: HIRALAL AGRAWAL EXECUTIVE.

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Presentation on theme: "SPECIFICATIONS/ QUALITY REQUIREMENTS PERTAINING TO CONSTRUCTION OF SUB-GRADE/ SUB-BASE/ BASE/ BT WORKS IN FLEXIBLE PAVEMENTS By: HIRALAL AGRAWAL EXECUTIVE."— Presentation transcript:

1 SPECIFICATIONS/ QUALITY REQUIREMENTS PERTAINING TO CONSTRUCTION OF SUB-GRADE/ SUB-BASE/ BASE/ BT WORKS IN FLEXIBLE PAVEMENTS By: HIRALAL AGRAWAL EXECUTIVE ENGINEER

2 TYPICAL CROSS-SECTION OF A FLEXIBLE PAVEMENT

3 SECTION-1 Embankment/Sub-grade Construction
The construction of embankments including Sub-grades, earthen shoulders etc. is governed by Clause 305 of MORT & H Specification for Roads & Bridge Works (5th revision). A) Physical Requirements of Materials: The materials used for construction of embankments/sub-grades/ earthen shoulders/Backfills shall be soil/earth, moorum, fly ash or a mixture of these or any other materials as approved by the Engineer. The following types of materials shall be considered unsuitable:- Materials from swamps, marshes etc. Clay having Liquid Limit (LL) > 50 and Plasticity Index(PI) > 25. Expansive Clay exhibiting marked swell & shrinkage properties with Free Swelling Index > 50. B) Other Requirements: (i) The size of the coarse materials/particle in the earth shall ordinarily not exceed 75mm, when placed in the embankment and 50mm, when placed in the sub-grade.

4 Max. dry density (MDD) when tested in lab as per IS: 2720 (Part-8)
(ii) Ordinarily, only the materials satisfying the density requirements given in Table of MORT&H spec., 5th Revn shall be used for the construction of the embankment/sub-grade/shoulders etc. TABLE 300-1: Density Requirements of Embankment & Sub-grade Materials Type of Work Max. dry density (MDD) when tested in lab as per IS: 2720 (Part-8) Embankments up to 3m height, not subjected to extensive flooding. Not less than 1.52gm/cc or 15.2 KN/cum Embankments exceeding 3m height or embankments of any height subject to long periods of inundation. Not less than 1.60gm/cc or 16.0KN/ cum Sub-grade/Earthen Shoulders/ Backfill Not less than 1.75gm/cc or 17.5KN/cum NOTE: 1) The above table is not applicable for lightweight fill materials. e.g. Fly-ash, etc. 2) The material to be used in Sub- grade shall be non-expansive and shall satisfy the design CBR.

5 iii) It shall be ensured prior to actual execution that the material to be used in the Sub-grade satisfies the requirements of design CBR. iv)The field/actual CBR of the constructed sub-grade shall be determined on remoulded samples, compacted to the field density at the field moisture content and tested for 4 days’ soaked condition at Lab. C) The materials used for embankment construction shall be tested for sieve analysis, LL/PL, MDD/ OMC, CBR etc. at Lab & got approved from the Engineer prior to use.

6 Sand Content/Sieve Analysis = 2 tests [As per IS:2720, Part-4]
D) The following routine tests on representative samples of earth shall be carried out for every 3000 cum for each source during construction as per Section 900 of MORT&H Specification, 5th Revision. Sand Content/Sieve Analysis = 2 tests [As per IS:2720, Part-4] Atterberg Limits (LL/PL)tests = 2 tests [As per IS:2720, Part-5] Density test (MDD/OMC) = 2 tests [As per IS:2720, Part-8] Moisture Content test = 2 tests [As per IS:2720, Part-2] CBR tests = 1 test [As per IS:2720, Part-16] E) Compaction Control at Field: Field Density shall be conducted on each finished layer by taking at least one set of 10 measurements of density for each 3000 sqm of compacted area or closer in accordance with IS: 2720 (Part-28) [Sand Replacement Method]. Test locations shall be chosen only through random sampling techniques. The acceptance criteria shall be subject to the condition that the Average Mean density is not less than the Specified Density Plus [1.65 – 1.65/ (No. of samples) 0.5] times the standard deviation (S.D). If the no. of density measurement/ samples=10, then the average mean density should not be less than the specified density plus 1.13 times the S.D.

7 SECTION-2 CONSTRUCTION OF GRANULAR SUB-BASE (GSB)
1) The construction of GSB is governed by Clause 401 of MORT&H Specifications for Road & Bridge Works (5th Revision). 2) The materials to be used for GSB work shall be natural sand, Crushed stone, Crushed Slag or combination thereof depending upon the grading required. 3)The type of grading of GSB to be adopted in a particular work shall be clearly specified in the BOQ/Contract and accordingly required materials to be used in GSB are decided. 4) As per MORT&H Specification,4th Revision, which is also mostly being used today, there are 6 types of GSB Close-graded GSB- Gr-I, Gr-II, Gr-III Coarse-graded GSB- Gr-I, Gr-II, Gr-III 5) As per MORT&H Specification, 5th Revision, there are 6 types of GSB, namely Grading I, II, III, IV, V & VI. Grading III & IV shall preferably be used in lower sub- base, and Grading V & VI shall be used as a sub-base cum drainage layer. The grading requirements of these GSBs are given in Table of MORT&H Specification, 5th Revision.

8 6)Other physical Requirements for Materials for GSB
Test Test Method as per Requirements Aggregate Impact Value (AIV) IS: 2386 (Part- 4) Maximum 40% Liquid Limit (LL) IS: 2720 (Part- 5) Maximum 25 Plasticity Index (PI) Maximum 6 Water absorption of Aggregates IS: 2386 (Part- 3) Maximum 2% CBR (at 98% of MDD, determined as per IS: 2720, Part-8) Minimum 30% 7)The mix design of GSB to be done at laboratory prior to execution of the work to arrive at the proportions of various materials to be used/ Job-Mix Formula (JMF). The GSB work is to be carried out strictly as per the JMF prescribed by the LAB.

9 IS Sieve Gr I Gr II Gr III Gr IV Gr V Gr VI
8) GRADING for GSB Materials (Table of MORTH, 5th Revision) IS Sieve Gr I Gr II Gr III Gr IV Gr V Gr VI 75.0mm 100 - 53.0mm 80-100 26.5mm 55-90 70-100 55-75 50-80 75-100 9.50mm 35-65 4.75mm 25-55 40-65 10-30 15-35 25-50 30-55 2.36mm 20-40 30-50 10-20 10-25 0.85mm 2-10 425mic 10-15 0-5 0-8 75mic <5 0-3

10 Test Frequency(Minimum)
9) At the time of compaction, the moisture content of the GSB mix shall be so adjusted that it lies from 1 to 2% below the Optimum Moisture Content (OMC).Rolling shall be continued till the density achieved is at least 98% of the Maximum Dry Density (MDD), determined at LAB as per IS: 2720 (Part-8). The %age/ degree of compaction of the compacted layer of GSB to be tested at field as per IS: 2720 Part-28 (Sand Replacement Method), generally using Bigger Sand Pouring Cylinder. 10)Various Routine Quality Control Tests as prescribed in Table of MORT&H Specification (5th Revision), shall be carried out during execution of GSB, some of which are given below: Test Frequency(Minimum) Gradation 1 test per 400 cum. Atterberg Limits Moisture content prior to compaction Density of compacted Layer 1 test per 1000 sqm.

11 SECTION-3 CONSTRUCTION OF BASE (NON-BITUMINOUS)
1) WATER BOUND MACADAM(WBM) (Popularly known as Metalling) i) The construction of WBM is governed by Clause 404 of MORT&H Specification, 5th Revision & consists of crushed/ broken aggregates (popularly known as ‘Metals’), mechanically interlocked by rolling and bonding together with stone screening, binding materials (wherever necessary) and water, laid on a properly prepared Sub-grade/Sub-base/ base or existing pavement as the case may be. ii) Materials for WBM a) Screenings It shall generally consist of stone screenings. However, in some cases we can allow moorum/ gravel, provided Liquid Limit(LL) and Plasticity Index (PI) of such materials are below 20 and 6 respectively and also fraction passing 75 mic. Sieve does not exceed 10%. The grading requirement of Screening is given in Table of MORT&H Specification, 5th Revision.

12 b) Coarse Aggregates (‘Metals’)
These shall be either crushed/broken stones, crushed slag etc. of suitable quality, the physical requirements of which are given in table of MORT&H Spec., 5th Revn and reproduced below:- Physical Requirements of Coarse Aggregates for WBM Test Test Method Requirements Los Angeles Abrasion (LA) Value or Aggregate Impact Value(AIV) IS:2386 (Part-4) Maximum 40% Maximum 30% Flakiness & Elongation Index (FI & EI) (Total) IS:2386 (Part-1) Maximum 35% Water Absorption IS:2386 (Part-3) Maximum 2% NOTE: - If the water absorption value is greater than 2%, Soundness test shall be done as per IS: 2386 (Part-5).

13 Tests Frequency (Minimum)
Grading Requirements of Coarse Aggregates for WBM (Table 400-9) Grading No. Size Range IS Sieve Cum %age passing 1 63 to 45mm 75mm 63mm 53mm 45mm 22.4mm 100 90-100 25-75 0-15 0-5 2 53 to 22.4mm 11.2mm 95-100 65-90 0-10 NOTE: - The compacted thickness for a WBM Layer shall be 75mm. iii) Routine Quality Control Tests for WBM during execution: Tests Frequency (Minimum) Aggregate Impact Value (AIV) 1 test per 1000 cum of Aggregates Grading of Aggregates 1 test per 250 cum of Aggregates

14 2)WET MIX MACADAM (WMM) 1) The construction of WMM is governed by Clause 406 of MORT&H Specifications, 5thRevn. WMM consists of laying and compacting clean, crushed, graded aggregates & granular materials, mixed with water &thoroughly mixed up in a Wet Mix Plant. 2) Generally 40mm, 20mm, 10mm, 6mm, Crusher/Stone dust is used for preparation of WMM Mix. 3)WMM can be laid in one or more layers. The thickness of a single compacted layer of WMM shall not be less than 75mm. However we can go up to 150mm thickness, if vibratory roller is used. 4) The physical requirements of Coarse Aggregates are same as in case of WBM.

15 GRADING REQUIREMENTS OF WMM
IS Sieve Cum % by weight passing the sieve 53.0 mm 100 45.0 mm 95-100 26.5 mm - 22.4 mm 60-80 11.2 mm 40-60 4.75 mm 25-40 2.36 mm 15-30 600 mic 8-22 75 mic 0-5 NOTE: 1)Materials finer than 425 mic sieve shall have PI < 6. 2)The final gradation for WMM shall be such that it shall not vary from the low limit on one sieve to the high limit on the adjacent sieve or vice versa.

16 5)Mix design of WMM is to be done at laboratory before execution to find out the Job- Mix Formula (JMF)/ proportioning of various materials to be used and also MDD/OMC. The WMM work is then done strictly as per the JMF. 6)The moisture content of the WMM mix at the time of compaction should be 1-2% less than the corresponding OMC, found out at Lab. 7)Rolling shall be continued till the density achieved is at least 98% of the MDD determined at Lab as per IS: 2720 Part-8. 8)No vehicular Traffic, other than construction equipments, shall be allowed on the finished WMM surface.

17 9)Routine Quality Control Tests of WMM during execution.
Frequency (Minimum) Aggregate Impact Value (AIV) 1 test per 1000 cum of aggregates Grading of Aggregates and Atterberg Limits. 1 test per 200 cum of aggregates Combined Flakiness & Elongation Index 1 test per 500 cum of aggregates Density of compacted layer/ Field Density 1 set of 3 tests for 1000 sqm 10)In case it is found that there is appreciable variation in gradation and other properties of aggregates being used in the work from those tested during mix- design at Lab, the JMF is to be suitably revised in Lab and then used in the work. 11)The acceptance criteria for density tests in WMM shall be same as that in case of embankments/ sub- grade construction. 12)The detailed procedure of construction of WMM is given in Clause 406.

18 SECTION-4 CONSTRUCTION OF BASE COURSE(BITUMINOUS)
The frequently used bituminous base course/ Binder Course are Bituminous Macadam (BM) / Dense Bituminous Macadam (DBM). The general requirements for construction of bituminous pavement layers/ courses are covered in Section 500 of MORT&H Specifications, 5th Revision. 1)BITUMINOUS MACADAM (BM) : The construction of BM is governed by Clause 504 of MORT&H Spec., 5th Revn. BM consists of construction of single course of mm thickness or multiple courses of compacted crushed aggregates premixed with bitumen, prepared/ mixed up in a Hot-Mix Plant (HMP) and laid usually over a prepared base or existing BT surface through paver. Materials for BM Bitumen (Paving grade conforming to IS:73) Coarse Aggregates, consisting of crushed stone retained on mm sieve. Fine aggregates, consisting of crushed mineral materials, passing 2.36 mm sieve & retained on 75 mic sieve.

19 Important Physical Properties of Coarse Aggregates for BM
In general, 20mm, 10mm, 6mm & crusher dust along with Bitumen is used for preparing BM Gr-II mix and 25mm, 20mm, 10mm, 6mm & crusher dust along with bitumen is used for BM Gr-I Mix. Important Physical Properties of Coarse Aggregates for BM Property Test Requirements Strength LA Value Or AIV Maximum 40% Maximum 30% Particle Shape Combined FI & EI Maximum 35% Durability Soundness Test (5 cycles) Sodium Sulphate Magnesium Sulphate Maximum 12% Maximum 18% Porosity Water Absorption Maximum 2% Stripping Coating & Stripping of Bitumen Aggregate Minimum retained coating 95% (IS:6241)

20 Nominal Max aggregate Size
Aggregate Grading & Bitumen Content for BM Grading 1 2 Nominal Max aggregate Size 37.5mm 19mm Layer thickness 80-100mm 50-75mm IS Sieve Size Cum %age passing 45mm 100 - 90-100 26.5mm 75-100 19.0mm 13.2mm 35-61 56-88 4.75mm 13-22 16-36 2.36mm 4-19 300mic 2-10 75mic 0-8 Bitumen content 3.3% 3.4%

21 The mix design is to be done at Lab to determine Job-Mix Formula (JMF) i.e. proportioning of various materials & the density of the mix. Then the work is to be executed strictly as per the JMF. The bitumen temperature, aggregate temperature, mix temperature, laying and rolling temperature, shall be , , , 140 minimum and 900 C minimum respectively when VG- 30 grade bitumen is used. Rolling must be completed before the mat cools down to 900 C and shall be continued until the desired density is achieved or there is no further movement of mix under the roller.

22 Routine Quality Control Tests for BM during execution
In case, it is found that there is appreciable/ large variation in gradation & other properties of aggregates being used from those tested during the mix design at Lab, the JMF is suitably revised and a fresh density is also determined at Lab and accordingly the work is executed. The detailed procedure of construction of BM is given in Clause 504 of MORT&H Specification, 5th Revision. Tests Frequency (Minimum) Grading of aggregates 2 tests per day Bitumen Content 2 tests per day per plant Other physical properties such as AIV, FI & EI, etc. At regular interval, at least 1 test for each source. Mix temperature at the time of laying & compaction and also at HMP. At regular intervals.

23 2)DENSE BITUMINOUS MACADAM (DBM)
The construction of DBM is governed by Clause 505 of MORT&H Spec. for Road & Bridge Works, 5thRevn. DBM is mostly used in Base/Binder course and is laid in a single or multiple layers on a previously prepared base or sub-base. The thickness of a single layer shall be 50mm to 100mm. DBM consists of a mixture of crushed aggregates of various sizes premixed with bitumen, prepared/ mixed up in a Hot- Mix Plant (HMP) and laid with a paver machine. Materials for DBM Bitumen (Paving grade conforming to IS:73) Coarse Aggregates, consisting of crushed rock/stone retained on 2.36 mm sieve. Fine aggregates, consisting of crushed mineral materials, passing 2.36 mm sieve & retained on 75 mic sieve. Filler, consisting of finely divided mineral matter such as crushed stone/dust, hydrated lime or cement, 100% passing in 600 mic sieve, % passing in 300 mic sieve & % passing in 75 mic sieve.

24 Nominal maximum aggregate size Cumulative %age passing
Physical Requirements for Coarse Aggregates for DBM Same as that in case of BM, except the LA & AIV value. The maximum LA value & AIV in case of DBM is 35% & 27% respectively. Aggregate Gradation & Bitumen Content for DBM (Table ) Grading 1 2 Nominal maximum aggregate size 37.5 mm 26.5 mm Layer thickness mm 50-75 mm IS Sieve Cumulative %age passing 45mm 100 - 37.5mm 63- 93 90-100 19.0 mm 71-95 13.2 mm 55-75 56-80 4.75mm 38-54 2.36mm 28-42 300 mic 7-21 75 mic 2-8 Bitumen Content Minimum 4% Minimum 4.5%

25 Mix Requirements for DBM (Table 500-11)
NOTE: The combined aggregate grading shall not vary from the low limit on one sieve to the high limits on the adjacent sieve and vice versa. The bitumen content indicated above is minimum only and the actual bitumen content is to be found out at Lab by doing Mix-design (Marshall Method). The fines to bitumen (F/B) ratio by weight of total mix shall range from 0.6 to 1.2. Mix Requirements for DBM (Table ) Properties In case of Viscosity grade paving bitumen In case of Modified bitumen (Hot Climate) Compaction level 75 blows on each face of the Marshall Specimen. Minimum Marshall Stability (at 600c) 9KN or 900Kg 12KN or 1200Kg Marshall Flow (mm) 2-4 2.5-4 Marshall Quotient (Stability/ Flow) 2-5 2.5-5 %age air voids 3-5 %age voids filled up with Bitumen (VFB) 65-75 Coating of aggregates 95% minimum %age voids in Mineral Aggregates (VMA) 12% for DBM Gr-II & 11% FOR DBM Gr-I 11% for DBM Gr-I

26 Before execution of the DBM work, mix-design is to be done at laboratory and a Job-Mix Formula (JMF) is to be found out/ proposed for use in the works. The JMF should be based on a correct and truly representative sample of materials that will actually be used in the work. The work should be executed strictly as per the laboratory JMF. Whenever there is a change in source of materials to be proposed, a new JMF shall be worked out at Lab through a revised mix-design. Once the Lab JMF is approved, plant trials should be done at HMP site so as to ensure that the plant can produce a uniform mix conforming to the approved JMF with the permissible variations as per Table The temperatures to be maintained in bitumen, aggregates, mix and the laying and compacting temperature etc. are same as in case of BM and to be strictly ensured during execution of the DBM work. Rolling shall continue until the desired density i.e. 92% of GMM (Approximately 95-96% of Lab Density) is achieved at field. It is to be checked by taking 150mm size cores from the compacted layer of DBM through core cutter machine. Rolling must be completed before the mat cools down to 900 C.

27 Routine Quality Control Tests for DBM during execution
Frequency (Minimum) Grading/Sieve Analysis And Bitumen Content 1 set for individual constituents & mixed aggregate from dryer for each 400 tons of DBM mix subject to minimum of 2 tests per day per plant. AIV and FI & EI etc. 1 test per 350 cum of aggregates for each source & whenever there is change in source/ quality of aggregates. Stability and voids analysis 3 tests for stability/ flow value, density and air voids etc. for each 400 tons of mix subject to minimum of 2 tests per day per plant. Temperature of DBM mix at the time of laying & compacting & also in HMP. At regular intervals. In case it is found that there is appreciable variation in gradation & other properties of aggregates being used from those tested during mix design at lab, the JMF is suitably revised & a fresh mix design is done at lab and then the work is executed as per the revised JMF. The detailed procedure of construction of DBM is given in Clause 505 of MORT&H Specification, 5th Revision.

28 SECTION-5 CONSTRUCTION OF BITUMINOUS WEARING COURSE
The frequently used bituminous wearing courses are Semi- Dense Bituminous Concrete (SDBC), Bituminous Concrete (BC), Open graded premium surfacing [popularly known as Pre Mix Carpet (PMC)] along with seal coat (SC), close - graded Premix Surfacing [Mixed Seal Surfacing (MSS)]. 1) Semi- Dense Bituminous Concrete (SDBC) The construction of SDBC is governed by Clause 508 of MORT&H Specification for Roads & Bridges, 4th Revision and IRC: SDBC is laid in single layer of 25mm to 40mm. It generally consists of a mixture of crushed aggregates of various sizes & bitumen, premixed in a Hot- Mix Plant (HMP) & laid with a paver machine. Materials for SDBC Coarse aggregates, Fine aggregates, filler, etc. Physical properties of Coarse Aggregates for SDBC are same as that in case of DBM, except additional requirement of Polished Stone Value, which should be minimum 55%.

29 Nominal Max Aggregate Size
Aggregate grading and binder Content for SDBC (Table: of MORT&H Specification, 4th Revision) Grading Gr-I Gr-II Nominal Max Aggregate Size 13.2mm 9.5mm Layer Thickness 40mm 25mm IS Sieve Cum %age passing 19.0mm 100 - 90-100 70-90 4.75mm 35-51 2.36mm 24-39 1.18mm 15-30 3oo mic 9-19 75 mic 3-8 Bitumen Content Minimum 4.5% Minimum 5%

30 Mix Requirements of SDBC
Same as that in case of DBM except the VMA which is 14% for SDBC Gr- I & 15% for SDBC Gr-II. Before execution of the SDBC works, mix design is to be done at lab and a Job- Mix Formula (JMF) is to be found out/proposed for use in the works. The JMF should be based on a correct and truly representative sample of materials that will actually be used in the work. The work should be executed strictly as per the lab JMF. Whenever there is a change in source of materials, a new JMF shall be worked out at lab through a revised Mix Design. Once the lab JMF is approved, plant trials should be done at HMP site so as to ensure that the plant can produce a uniform mix conforming to the approved JMF with the permissible variation as per Table of MORT&H Specification, 4th Revision. The temperature and compaction requirements are the same as in case of DBM. The routine quality control tests for SDBC to be done at field lab during execution of the work are almost the same as in case of DBM. In case, it is found that there is appreciable variation in gradation & other properties of aggregates being used from those tested during mix design at lab, the JMF is suitably revised & a fresh mix design is done at lab and then the work is executed as per the revised JMF. The detailed procedure of construction of SDBC is given in Clause 508 of MORT&H Specification, 4th Revision.

31 2) Bituminous Concrete (BC)
The construction of BC is governed by Clause 507 of MORT&H Specification of Roads & Bridges, 5th Revision. BC is laid in single layer of 30mm / 40mm/ 50mm. It generally consists of a mixture of crushed aggregate of various sizes and bitumen, premixed in a HMP and laid with a paver machine. Materials for BC Bitumen, Coarse aggregates, Fine aggregates, filler, etc. as in case of DBM / SDBC. The physical properties of Coarse Aggregates for BC are same as in that in case of SDBC, except the LA & AIV requirement. The maximum LA & AIV in case of BC is 30% & 24% respectively.

32 Nominal Max Aggregate Size
Aggregate grading and Binder Content for BC (Table ) Grading 1 2 Nominal Max Aggregate Size 19mm 13.2mm Layer Thickness 50mm 30-40mm IS Sieve Cum %age passing 26.5mm 100 - 19.0mm 90-100 59-79 9.5mm 52-72 70-88 4.75mm 35-55 53-71 2.36mm 28-44 42-58 1.18mm 20-34 34-48 6oo mic 15-27 26-38 300 mic 10-20 18-28 150 mic 5-13 12-20 75 mic 2-8 4-10 Bitumen Content Minimum 5.2% Minimum 5.4%

33 The mix requirements of BC such as stability, flow, air voids, etc
The mix requirements of BC such as stability, flow, air voids, etc. are same as that in case of DBM/ SDBC except the VMA, which is 13% for BC Grade-I The other requirements such as temperature, compaction & routine quality control tests, etc. are almost same as in case of DBM/SDBC. Before execution of the BC works, mix design is to be done at lab and a Job- Mix Formula (JMF) is to be found out for use in the works. The JMF should be based on a correct and truly representative sample of materials that will actually be used in the work. The work should be executed strictly as per the lab JMF. Whenever there is a change in source of materials, a new JMF shall be worked out at lab through a revised Mix Design. Once the lab JMF is approved, plant trials should be done at HMP site so as to ensure that the plant can produce a uniform mix conforming to the approved JMF with the permissible variation as per Table of MORT&H Specification, 5th Revision.

34 OPEN- GRADED PREMIX SURFACING (Popularly known as PMC)
It is an open-graded mix of 20mm thickness, composed of stone aggregates of nominal size 13.2mm(passing 22.4mm and retained on 11.2mm sieve) (67%) and 11.2mm (passing 13.2mm and retained on 5.6mm sieve) (33%), premixed with bitumen and prepared in a hot mix plant (HMP) and laid over a prepared base. The construction of PMC is governed by Clause- 510 of MORT&H Specification, 5th Revision. The physical requirements of Aggregates are same as that in case of BM except that the water absorption value shall not be more than 1% and stone polished value shall not be less than 55. If the loose density/ specific gravity of the above 2 aggregates i.e and 11.2mm are almost same, then the above proportions of 67% and 33% by volume can also be taken as same proportion by weight also. In that case, one tentative combined grading limits of PMC mix has been developed empirically in lab, which is given in the next slide:

35 Cum %age passing by weight of total aggregates
IS Sieve Cum %age passing by weight of total aggregates 22.4mm 100 11.2mm 25-35 5.6mm Routine quality control tests are to be done during execution in accordance with Table of MORT&H Specification, 5th Revision. Seal coat (SC) is to be applied to the PMC surface immediately after laying the PMC. No traffic shall be allowed on the PMC surface until the seal coat is laid. The traffic may be allowed soon after final rolling when the premixed SC materials has cooled down to the surrounding temperature. However, in case of Type-A sealcoat, traffic should not be permitted until the next day.

36 SEAL COAT (SC) It is applied for sealing the voids on the PMC surface so as to make the finished surface less permeable to water. There are 2 types of SC, namely Type A (Liquid SC) using stone chips of 6.7mm size (100% passing 11.2mm & retained on 2.36mm) & Bitumen; Type B (Premixed SC) comprising sand or crusher dust passing 2.36mm sieve and retained on 180 mic sieve & Bitumen. Premixed SC is generally mixed/ prepared in Hot Mix Plant. The details of SC is given in Clause 511 of MORT&H Specification, 5th Revision.

37 Cum %age passing for Type A Cum %age passing for Type B
CLOSE-GRADED PREMIX SURFACING (MSS) It is a close graded mix of 20mm thickness, composed of graded aggregates premixed with Bitumen, prepared in a HMP. It is generally used as a wearing course on light-trafficked road and high rainfall areas and is of 2 types i.e. Type A or Type B. The physical requirements of coarse aggregates for MSS are same as in case of Open Graded Premix Surfacing (PMC). Aggregate Gradation for MSS (Table ) IS Sieve Cum %age passing for Type A Cum %age passing for Type B 13.2mm - 100 11.2mm 88-100 5.6mm 52-88 31-52 2.8mm 14-38 5-25 90 mic 0-5 Bitumen 2.2Kg/sqm 1.9Kg/sqm Routine Quality Control Tests to be done are same as in case of PMC work. Traffic may be allowed after completion of the final rolling when the mix has cooled down to the surrounding temperature.

38 THANK YOU


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