National standard 8819 2011

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Tiêu chuẩn thi công và nghiệm thu bê tông nhựa nóng Bản dịch tiếng Anh với các thuật ngữ chuyên ngành cầu đường của Phiên dịch 8 năm kinh nghiệm trong ngành. Tiêu chuẩn được áp dụng cho các dự án cầu đường lớn của Việt Nam. NATIONAL STANDARD TCVN 8819:2011 First edition SPECIFICATION FOR CONSTRUCTION OF HOT MIX ASPHALT CONCRETE PAVEMENT AND ACCEPTANCE HANOI – 2011 Table of Contents Foreword TCVN 8819:2011 is converted from 22 TCN 249-98 according to regulations in Clause 1, Article 69, Law on Technical Standards and Regulations and point a, section 1, clause 1, Article 7, Decree No.127/2007/ND-CP dated 01/08/2008 by the Government providing details for implementation of some articles under Law on Technical Standards and Regulations TCVN 8819:2011 is composed by Institute of Transport Science and Technology, recommended by Ministry of Transport, verified by Directorate for Standards, Metrology and Quality and published by Ministry of Science and Technology NATIONAL STANDARD TCVN 8819:2011 Specification for Construction of Hot Mix Asphalt Concrete Pavement and Acceptance Scope of application 1.1 This standard provides technical regulations on materials, technology to produce hot mix, technology for pavement, inspection, supervision and acceptance of asphalt concrete payment layers (asphalt concrete) by hot mixing and hot paving method 1.2 This standard is applied for new construction, repair, and improvement of pavement for highway, street, road, yard and square 1.3 This standard is in no case applied for asphalt concrete using bitumen with improvement admixture, mastic asphalt, asphalt concrete with special function (thin asphalt concrete layer with high roughness, porous asphalt with high roughness, stone matrix asphalt) References The following references are very necessary for applying this standard For references with year of publish indicated, apply the stated version For references without specifying date of issuance, apply the latest version including modifications (if any) TCVN 7572-2: 2006 Aggregates for concrete and mortar – Testing method – Part 2: Determination of particle size distribution TCVN 7572-7: 2006 Aggregates for concrete and mortar – Testing method – Part 7: Determination of moisture TCVN 7572-8: 2006 Aggregates for concrete and mortar – Testing method – Part 8: Determination of content of dust, mud, clay in aggregates and clay lumps in fine aggregate TCVN 7572-10: 2006 Aggregates for concrete and mortar - Testing method – Part 10: Determination of strength and softening coefficient of the original stone TCVN 7572-11: 2006 Aggregates for concrete and mortar - Testing method – Part 11: Determination of crushing value and softening coefficient of coarse aggregate TCVN 7572-12: 2006 Aggregates for concrete and mortar - Testing method – Part 12: Determination of resistance to degradation of coarse aggregate by abrasion and impact in Los Angeles machine TCVN 7572-13: 2006 Aggregates for concrete and mortar - Testing method – Part 13: Determination of elongation and flakiness index of coarse aggregate TCVN 7572-17: 2006 Aggregates for concrete and mortar - Testing method – Part 17: Determination of feeble weathered particle content TCVN 7572-18: 2006 Aggregates for concrete and mortar - Testing method – Part 18: Determination of crushed particle content TCVN 4197-1995 Soil – Laboratory method for determination of plastic limit and liquid limit TCVN 7493:2005 Bitumen – Technical Specification TCVN 7494:2005 Bitumen – Sampling method TCVN 7495:2005 Bitumen – Method for determination of penetration TCVN 7496:2005 Bitumen – Method for determination of elongation TCVN 7497:2005 Bitumen – Method for determination of softening point (ring and ball apparatus) TCVN 7498:2005 Bitumen – Test Method for Flash and Fire Points by Cleveland Open Cup Tester TCVN 7499: 2005 Bitumen - Test Method for Weight Loss on Heating TCVN 7500: 2005 Bitumen - Test Method for Solubility in Trichloroethylene TCVN 7501: 2005 Bitumen - Test Method for Specific weight (Pycnomefer method) TCVN 7503: 2005 Bitumen - Determination of the Paraffin Wax Content by Distillation TCVN 7504: 2005 Bitumen – Test method for adhesion with paving stone TCVN 8860-1:2011 Asphalt concrete – Test method – Part 1: Determination of Marshal stability and Marshal flow TCVN 8860-4:2011 Asphalt concrete – Test method – Part 4: Determination of Maximum Specific Gravity and Density of loose Bituminous Paving Mixtures TCVN 8860-5:2011 Asphalt concrete – Test method – Part 5: Determination of Bulk Specific Gravity and Unit Weight of Compacted Bituminous Mixtures TCVN 8860-7:2011 Asphalt concrete – Test method – Part 7: Determination of Fine Aggregate Angularity TCVN 8860-8:2011 Asphalt concrete – Test method – Part 8: Determination of Compaction Coefficient TCVN 8860-9:2011 Asphalt concrete – Test method – Part 9: Determination of Air Voids TCVN 8860-10:2011 Asphalt concrete – Test method – Part 10: Determination of Voids in the Mineral Aggregates TCVN 8860-12:2011 Asphalt concrete – Test method – Part 12: Determination of Remaining Stability of asphalt concrete TCVN 8820:2011 Hot mix asphalt concrete – Designed by Marshall method TCVN 8864:2011 Highway pavement - Standard test method for measuring road pavement surface roughness using a 3.0m straight edge TCVN 8865:2011 Highway pavement - Method for measuring and assessment roughness by International Roughness Index (IRI) TCVN 8866:2011 Highway pavement – Standard test method for measuring pavement macrotexture depth using a volumetric technique TCVN 8817-1:2011 Cationic emulsified asphalt – Part – Technical Specification TCVN 8818-1:2011 Cut-back asphalt – Part – Technical Specification AASHTO T 176 Standard Method of Test for Plastic Fines in Graded Aggregates and Soils by Use of the Sand Equivalent Test AASHTO T 324-04 Standard Method of Test for Hamburg Wheel-Track Testing of Compacted Hot Mix Asphalt (HMA) Terminology and Definition In this standard the following terms are used: 3.1 Hot Mix Asphalt Concrete Pavement The pavement (including or more layers with designed thickness) produced from hot mixing asphalt concrete 3.2 Hot Mix Asphalt Concrete - HMA A mix constituted of aggregates (crushed stone, sand, mineral powder) with a pre-designed mixing proportion, and then being heated and mixed, mixed with a certain rate of asphalt by mixing design Hot mix asphalt is produced in the batching plant 3.3 Maximum Size of Aggregate The minimum size of sieve that percentage of particle passing that size is 100% This standard uses ASTM square sieve mesh system to test aggregate particle size and shows aggregate curve by size of aggregate particle 3.4 Nominal Maximum Size of Aggregate The largest sieve that retains some of the aggregate particles but generally not more than 10 percent by weight 3.5 Asphalt Content The amount of asphalt in asphalt concrete mixture, by percentage of asphalt concrete mix weight (including aggregates of crushed stone, sand, mineral powder, asphalt) 3.6 Optimum Asphalt Content Content of asphalt to be determined by asphalt concrete design, in proportion with a selected percentage of aggregates and satisfies all technical specifications for aggregates and asphalt concrete indicated herein 3.7 Air voids Total volume of all small airspaces or pockets of air that occur between the coated aggregates in the compacted mixture of asphalt concrete Air voids are shown by volumetric percentage of compacted asphalt concrete mixture sample 3.8 Voids in the Mineral Aggregate The intergranular space occupied by asphalt and air in a compacted asphalt mixture It is the sum of volume of air and the volume of effective asphalt Voids in the mineral aggregate is indicated by volumetric percentage of compacted asphalt concrete mixture sample Classification and technical criteria for asphalt concrete 4.1 Classification of asphalt concrete 4.1.1 By air void, asphalt concrete is classified into types: - Dense-graded Asphalt Concrete (DAGC): with aid void ranging from 3% to 6%, used as pavement surface and sub-surface course The mixture must compose of mineral powder; - Open-graded Asphalt Concrete (OGAC): With aid void ranging from 7% to 12% and use as base course 4.1.2 By nominal maximum size of aggregate of dense - graded asphalt concrete, it is classified into types: - Dense - graded asphalt concrete with nominal maximum size of aggregate of 9.5mm (and maximum size of aggregate is 12.5mm), shortly called DAGC 9.5; - Dense - graded asphalt concrete with nominal maximum size of aggregate of 12.5mm (and maximum size of aggregate is 19mm), shortly called DAGC 12.5; - Dense - graded asphalt concrete with nominal maximum size of aggregate of 19mm (and maximum size of aggregate is 25mm), shortly called DAGC 19; - Dense - graded asphalt concrete with nominal maximum size of aggregate of 4.75mm (and maximum size of aggregate is 9.5mm), shortly called DAGC 4.75; Limit on composition of aggregate mixture (tested following TCVN 7572-2:2006) and scope of application of types of DAGC are stated in Table Table – Proportion of Aggregate of dense-graded asphalt concrete (DAGC) mixture Specification Nominal maximum size of aggregate, mm Size of square sieve mesh, mm DAGC 9.5 9.5 DAGC 12.5 DAGC 19 12.5 19 Passing sieve, % weight DAGC 4.75 4.75 25 - - 100 - 19 - 100 90÷100 - 12.5 100 90÷100 71÷86 - 9.5 90÷100 74÷89 58÷78 100 4.75 55÷80 48÷71 36÷61 80÷100 2.36 36÷63 30÷55 25÷45 65÷82 1.18 25÷45 21÷40 17÷33 45÷65 0.600 17÷33 15÷31 12÷25 30÷50 0.300 12÷25 11÷22 8÷17 20÷36 0.150 9÷17 8÷15 6÷12 15÷25 0.075 Recommended asphalt content % weight of asphalt concrete mixture Reasonable thickness of asphalt concrete layer (after compaction) cm 6÷10 6÷10 5÷8 8÷12 5.2÷6.2 5.0÷6.0 4.8÷5.8 6.0÷7.5 4÷5 5÷7 6÷8 3÷5 Sidewalk, lane for bicycle and nonmotorized vehicles Scope application of Surface course Surface and surface course subSub-surface course 4.1.3 By nominal maximum size of aggregate of Open - graded asphalt concrete, it is classified into types: Open - graded asphalt concrete with nominal maximum size of aggregate of 19mm (and maximum size of aggregate is 25mm), shortly called OGAC 19; - Open - graded asphalt concrete with nominal maximum size of aggregate of 25mm (and maximum size of aggregate is 31.5mm), shortly called OGAC 25; - Open - graded asphalt concrete with nominal maximum size of aggregate of 37.5mm (and maximum size of aggregate is 50mm), shortly called OGAC 37.5; Limit on composition of aggregate mixture (tested following TCVN 7572-2:2006) and scope of application of types of OGAC are stated in Table - Table – Proportion of Aggregate of Open-graded asphalt concrete (OGAC) mixture Specification Nominal maximum size of aggregate, mm OGAC 19 OGAC 25 OGAC 37,5 19 25 37,5 Size of square sieve mesh, mm Passing sieve, % weight 50 - - 100 37.5 - 100 90÷100 25 100 90÷100 - 19 90÷100 - 40÷70 12.5 - 40÷70 - 9.5 40÷70 - 18÷48 4.75 15÷39 10÷34 6÷29 2.36 2÷18 1÷17 0÷14 1.18 - - - 0.600 0÷10 0÷10 0÷8 0.300 - - - 0.150 - - - - - - 4.0÷5.0 3.5÷4.5 3.0÷4.0 8÷10 Base course 10÷12 Foundation 12÷16 Foundation 0.075 Recommended asphalt content % weight of asphalt concrete mixture Reasonable thickness of asphalt concrete layer (after compaction) cm Scope of application 4.2 Proportion for mixture aggregate for DAGC and OGAC while designing must be in limit specified in Table and Table The grading curve of designed aggregates must be regular, not change from lower limit of a sieve size to upper limit of the next size and vice versa 4.3 Optimum asphalt content of DAGC and OGAC (calculated by % of weight of asphalt concrete mixture) is selected based on mix design by Marshall method, so that technical criteria of designed asphalt concrete sample satisfy technical specifications in Table for DAGC and Table for OGAC Sequence of asphalt concrete mix design by Marshall method follows guidance in TCVN 8820:2011 and Appendix A Table 3- Technical specifications for dense graded asphalt concrete (DAGC) Specification DAGC 19 Indicators DAGC 12.5 DAGC 4.75 DAGC 9.5 Number of tampers 75x2 50x2 Stability at 600C, 40 min, kN ≥ 8.0 ≥5.5 Plasticity, mm 2÷4 2÷4 Remaining stability, % ≥75 ≥75 Air void, % 3÷6 3÷6 Void in the mineral aggregate (corresponding with air void of ≥ 15 ≥17 4%) ≥14 - Maximum nominal particle size 9.5mm ≥13 Test method TCVN 8860-1:2011 TCVN 8860-12:2011 TCVN 8860-9:2011 TCVN 8860-10:2011 - Maximum nominal particle size 12.5mm - Maximum nominal particle size 19mm Depth of wheel tracking (HWTD – Hamburg Wheel Tracking Device), 10000 circles, pressure of 0.70MPa, temperature of≤12.5 AASHTO T 324-04 50oC, mm (*): Test only with special instruction by the Employer, It is possible to compact for sampling with modified Marshall method (TCVN 8860-1:2011) Table 4: Technical specifications on open graded asphalt concrete (OGAC) Specification OGAC 19, OGAC 25 OGAC 37.5 (*) Number of tampers 50 x 75 x 2 Stability at 600C, 40 min, kN ≥5.5 ≥12.5 (**) Plasticity, mm 2÷4 3÷6 Remaining stability, % ≥ 65 ≥65 Air void, % 7÷12 7÷12 (*): Test in accordance with the enhanced Marshall method (**) : Immersing time of sample: 60 minutes Indicators Test method TCVN 8860-1:2011 TCVN 8860-12:2011 TCVN 8860-9:2011 Requirement on quality of asphalt concrete materials 5.1 Crushed stone 5.1.1 Crushed stone is from mountain rock or quarry rock Crushed stone originated from magma rock, clay sandstone, clay shale is not allowed 5.1.2 For OGAC, crushed boulder is allowed but not over 20% of mass (apply for silicon-based stone) 5.1.3 Physico-mechanical indicators of crushed stone used for asphalt concrete should meet requirements specified in Table Table - Physico-mechanical indicators for crushed stone Indicator Compressive strength of source rock, MPa - Magma rock, metamorphic rock - Sedimentary rock Regulation DGAC Top course Bottom course ≥100 ≥80 ≥80 ≥ 60 Test method ODAC Base course ≥80 ≥60 TCVN 7572-10: 2006 (based on test certificate of the manufacturer of crushed stone used for the construction work) TCVN 7572-12 : 2006 Loss due to strike inside Los Angeles ≤28 ≤35 ≤40 machine, % Content of flakiness and elongation ≤15 ≤15 ≤20 TCVN 7572-13 : 2006 particle (Rate 1/3) (*), % Content of soft and weathered particle, ≤10 ≤15 ≤15 TCVN 7572-17 : 2006 % Content of broken gravel (at least ≥80 TCVN 7572-18 : 2006 faces broken), % Compression of broken gravel under ≤14 TCVN 7572-11 : 2006 grinding, % General content of dust, mud, clay, % ≤2 ≤2 ≤2 TCVN 7572- : 2006 Ball clay content, % ≤ 0.25 ≤ 0.25 ≤ 0.25 TCVN 7572- : 2006 Cohesion of gravel and asphalt (**), ≥ grade ≥ grade ≥ grade TCVN 7504 : 2005 grade (*): Use square mesh sieve with dimension ≥ 4.75 mm, regulated at Table 1, Table to Content of flakiness and elongation particle (**): Where the crushed stone source intended for asphalt concrete production has the cohesion with asphalt less than grade 3, it is necessary to consider solutions: use admixture for adhesive strength increase (cement, lime, chemical additives), or use crushed stone from other sources to ensure the adhesive strength The solution shall be decided by Supervision Consultant 5.2 Sand 5.2.1 Sand used to make asphalt concrete is natural sand, milled sand, or a mixture of natural sand and milled sand 5.2.2 Natural sand shall not contain organic impurities (wood, coal ) 5.2.3 Milled sand shall be from rock whose compressive strength is not less than the compressive strength of those used to produce crushed stone 5.2.4 Sand used for sand asphalt (DGAC 4.75) shall contain a content not less than 18% for those with sieve number ranging from 4.75 mm to 1.18 mm 5.2.5 Physico-mechanical indicators of sand should meet requirements specified in Table Table - Physico-mechanical indicators for sand Indicator Module mass (MK) Equivalent sand coefficient factor (ES), % - Natural sand - Milled sand General content of dust, mud, clay, % Content of ball clay, % Lobbing loam of sand (void of sand before compression), % - DGAC of top course - DGAC of bottom course Regulation ≥2 ≥ 80 ≥50 ≤3 ≤ 0,5 Test method TCVN 7572-2: 2006 AASHTO T176 TCVN 7572- : 2006 TCVN 7572- : 2006 TCVN 8860-7:2011 ≥43 ≥ 40 5.3 Mineral Powder 5.3.1 Mineral powder is crushed from carbonate rock (limestone, calcite, dolomite ) with compressive strength of source rock greater than 20 MPa, from base slag of the furnace or cement 5.3.2 Carbonate stone for production of mineral powders must be clean, free of organic impurities, with general content of mud and clay mud not exceeding 5% 5.3.3 Mineral powder must be dry, not clotting 5.3.4 Physico-mechanical indicators of mineral powder should meet requirements specified in Table Table - Physico-mechanical indicators for mineral powder Indicator Regulation Test method Particle content (passing through square –hole TCVN 7572-2: 2006 sieve), % 100 - 0.600 mm 95÷100 - 0.300 mm 70÷100 - 0.075 mm Moisture, % ≤ 1,0 TCVN 7572-7: 2006 Plasticity index of mineral powder crushed from ≤ 4,0 TCVN 4197-1995 carbonate rock, (*) % (*): To determine plastic limit by Casagrande method Use mineral powder passing square mesh sieve of 0.425mm to test plastic limit and yield limit 5.4 Asphalt (bitumen) 5.4.1 Asphalt for producing asphalt concrete must be petroleum originated solid type, meeting technical requirements specified in TCVN 7493-2005 Refer to Appendix A of TCVN 7493-2005 to select the appropriate type of asphalt as hot asphalt concrete Type of asphalt shall be determined by Design Consultant 5.4.2 Asphalt 60/70 is very suitable for producing types of DGAC and ODAC Asphalt 85/100 is very suitable for producing DGAC 4.75 Asphalt concrete mix design 6.1 The aim of the mix design is to find out the mixing ratio among mineral materials (stone, sand, mineral powder) to satisfy the aggregate composition of asphalt concrete mixture specified for each type in Table and Table 2, and to find out the optimum asphalt content which satisfies the specifications for asphalt concrete in Table and Table 6.2 Asphalt concrete mix design shall apply Marshall method 6.3 Procedure of asphalt concrete mix design: The design is conducted in steps: Cold Mix Design, Hot Mix Design, and Job Mix Formulae The sequence design is guided in TCVN 8820:2011 and Appendix A 6.3.1 Cold Mix Design: The purpose of this step is to determine the appropriateness of the quality and particle composition of aggregate types available at the place of execution, the ability to use these aggregates to produce asphalt concrete satisfying the norms prescribed for asphalt concrete mixtures Materials at yard of batching plant are used for the design Results of this step is the basis for Hot Mix Design 6.3.2 Hot Mix Design: The purpose of this step is to determine the grading composition of the aggregate mixture and optimal asphalt content when aggregate is baked Test operation of batching plant shall be conducted on the basis of the Cold Mix Design Aggregate sampling is taken at reserve hopper of hot aggregate for the design Results of this step is the basis for the determination of trial production of asphalt concrete mixture and trial asphalt concrete paving 6.3.3 Job Mix Formulae: Based on Hot Mix Design, trial asphalt concrete paving shall be conducted Based on result of trial asphalt concrete paving, adjustment (if necessary) is conducted to determine the job mix formulae used for mass construction of asphalt concrete Job mix formulae is the basis for all subsequent works: production of asphalt concrete mix at the batching plant, construction, quality monitoring and acceptance The formulae should indicate the following: - Sources of aggregate and asphalt used for asphalt concrete mix; - Test results of physico-mechanical indicators of asphalt, crushed stone aggregates, sand, mineral powder; - Composition of mixed aggregates; - Proportion of aggregates: crushed stone, sand, stone powder at cold and hot hoppers; - Test results of Marshall method and optimum asphalt content (by percentage of the mass of asphalt concrete mix); - The biggest density of asphalt concrete (as a basis for determining Air void); - Volumetric mass of the asphalt concrete sample, equivalent to the optimum asphalt content (as a basis for determining the compaction K); - Construction method at site, such as: asphalt concrete thickness before rolling, rolling diagram, rolling turns per point, pavement roughness, etc 6.4 During the construction process, if there is any change in the input material sources or great variation in the quality of the materials, asphalt concrete mix design shall be redone in accordance with abovementioned steps and redefine the job mix formulae Asphalt concrete mix production at batching plant 7.1 Requirements for yard, stocking place of materials 7.1.1 The entire area of batching plant for asphalt concrete mix production must ensure environmental hygiene, good drainage and clean ground to keep the material clean and dry 7.1.2 Stocking place of crushed stone and sand for batching plant must be large enough, the material supply hole for the drum dryer of the mixer should be waterproofed Crushed stone and sand should be separated to avoid mixing; mixed material shall not be used 7.1.3 Stocking place of mineral powder: Mineral powder must have its own repository with high ground to avoid being moistened or quality degradation during storage 7.1.4 Area for asphalt heating and storage must be sheltered 7.2 Requirements for batching plant: use cyclic batching plant or continuous mixing plant to produce asphalt concrete mixt Requirements for these two types: Must have control devices, appropriate technical features and capacity, ensuring environmental hygiene, the ability to produce asphalt concrete mix with quality stability and allowable tolerances comparing to job mix formulae specified in Table in addition, for each type of batching plant, there are some following requirements: 7.2.1 Cyclic batching plant 7.2.1.1 Sieving system: It requires to adjust, supplement and change the sieving system of the batching plant to suit each type of asphalt concrete whose biggest nominal grain size is different, providing that the aggregate after drying will be split into grain groups which ensures that aggregate mix grading satisfies the established job mix formulae Lab sieve size and the corresponding converted sieve size for batching plant are referenced in Appendix B 7.2.2.2 Dust filter system: The return of dust to mix tank for asphalt concrete mix production shall be determined by the Employer, depending on quality of the dust The collected dust must be clean with plasticity index ≤ Table – Allowable tolerance comparing to job mix formulae Indicator Allowable tolerance (%) Grading of aggregate particle Passing amounts correspond to- Maximum diameter (Dmax) of asphalt0 sieve sizes, mm concrete - 12.5 and higher ±8 - 9.5 and 4.75 ±7 - 2.36 and 1.18 ±6 - 0.600 and 0,300 ±5 - 0.150 and 0.075 ±3 Asphalt content (% by total mixture mass) ± 0,2 7.2.2 Continuous batching plant: Becase this type does not have sieving system, it does not have hot aggregate drawer Therefore: 7.2.2.1 Grading of cold aggregate should be checked regularly, ensuring absolute stability 7.2.2.2 Quantitative balance system should be checked regularly, ensuring stable aggregate grading speed throughout the production process 7.3 Production of asphalt concrete mix 7.3.1 Chart of asphalt concrete mix production at batching plant should comply with regulation at technical specification for batching plant 7.3.2 The production of asphalt concrete mix at the batching plant should comply with the established job mix formula (definition at 6.3.3) 7.3.3 Allowable tolerance of the aggregate grain gradation and asphalt content of asphalt concrete mix coming out from mixing tank at batching plant in comparison with job mix formular should not exceed the value specified in Table 7.3.4 The output asphalt concrete mix should satisfy technical specifications for asphalt concrete specified in Table corresponding to DGAC, and Table corresponding to OGAC 7.3.5 Asphalt temperature at preliminary cooking is within 80-100oC for pumping into asphalt kettle 7.3.6 Asphalt temperature when transferring to batching bucket of the mixer shall correspond to asphalt viscosity at about 0.2 Pa.s Depending on the grade of asphalt, the temperature is usually within specified temperature range when mixing in the mixing tank (Table 9) 7.3.7 Asphalt should occupy 75% -80% of asphalt kettle capacity during cooking 7.3.8 Crushed stone grades and sand should be weighed preliminarily at aggregate feeding equipment before bringing into drum dryer, with allowable tolerance of ±5% 7.3.9 Aggregate temperature coming out drum dryer should not be over 15°C higher than the batching temperature Humidity of crushed stone and sand coming out drum dryer should be less than 0.5% 7.3.10 Mineral powder in cold form, after weighing, is fed directly into the mixing tank 7.3.11 Mixing time of aggregates and asphalt in the mixing tank must comply with the technical specifications for the kind of applied batching plant and the type of produced asphalt concrete mix, usually from 30s to 60s Mixing time is adjusted appropriately based on the results of pilot production and trial paving NOTE 1: Mixing time of aggregates and asphalt in the mixing tank is defined as the shortest time when satisfying following requirements: - When mixing asphalt concrete types used for top course: at least 95% of the aggregate grains are coated entirely with asphalt - When mixing asphalt concrete types used for base course: at least 90% of the aggregate grains are coated entirely with asphalt 7.3.12 Temperatures of asphalt concrete mixture corresponding to the construction stages and temperatures of Marshall test are specified in Table 7.4 Test for quality control of asphalt concrete mixture at batching plant 7.4.1 Each batching plant of asphalt concrete mixtures should be equipped with fully necessary experimental equipment to test material quality, physico-mechanical properties of the asphalt concrete mixture at batching plant 7.4.2 Experimental content and frequency for quality control over materials and asphalt concrete mixture at the batching plant are specified in 9.3 and 9.4 7.4.3 If the temperature of asphalt concrete mixture is higher than the maximum temperature specified for the mixing stage in the mixing tank, or higher than the maximum temperature when discharging the mixture into trunk silo, it shall be rejected (see Table ) Asphalt concrete construction 8.1 Cooperation during the construction 8.1.1 It should ensure smooth operation of the batching plant, means for transporting mixture to the site, paver and rolling facilities It should ensure that productivity of the batching plant is suitable with that of paver if overall productivity of the batching plant is low, it should supplement batching plant or order at some batching plants adjacent to the site of paving 8.1.2 The distance between the batching plant and the construction site must be carefully considered so that the asphalt concrete mixture being transported to the site can satisfy the temperature specified in Table Table - Temperatures of asphalt concrete mixture corresponding to the construction stages Construction stage Regulated temperature, corresponding to asphalt grade, 0C 40/50 60/70 85/100 Mix in mixing drum 155÷165 150÷160 145÷155 Discharge mixture into truck silo (or other transport 145÷160 140÷155 135÷150 mean) Discharge mixture from truck silo into hopper of ≥130 ≥125 ≥120 paver Start rolling ≥125 ≥120 ≥115 Finish rolling (ineffective rolling if the temperature ≥85 ≥80 ≥75 is lower than the regulated value) Temperature of Marshall specimen conduction: - Specimen mixing 155÷160 150÷155 145÷150 - Specimen compaction 145÷150 140÷145 135÷140 NOTE: The most effective temperature for asphalt concrete rolling and compaction, corresponding to the types of asphalt: - Asphalt 40/50: 140OC÷115OC; - Asphalt 60/70: 135OC÷110OC; - Asphalt 85/100: 130OC÷105OC 8.2 Requirements for construction condition 8.2.1 Only carry out the asphalt concrete construction when the air temperature is greater than 15 oC Do not execute at raining or possible raining condition 8.2.2 It should ensure the spreading and compaction shall be completed within day-time In special case of night-time construction, it must have sufficient lighting equipment to ensure quality and safety in the construction process which shall be approved by Supervision Consultant 8.3 Requirements for trial construction segment 8.3.1 Before mass construction or when using a different type of asphalt concrete, it should carry out trial construction on a segment for checking and determining construction technology applied for mass construction The trial segment should have minimum length of 100m, minimum width of traces of paver Trial segment shall be selected right at the site of mass construction or at another site of similar nature 8.3.2 Data from trial construction shall be used for the adjustment (if any) and the approval for mass construction Items for approval include: - Job mix formulae (according to 6.3.3); - Construction plan and technology: materials for tack coat or prime coat; ratio of tack coat or prime coat; allowable time for paving asphalt concrete after tack coat or prime coat application; thickness for paving asphalt concrete before rolling and compaction; paving temperature; temperature at the beginning and the end of rolling and compaction; work chart of roller types, necessary number of rolling turns; rolling compaction level; flatness; surface roughness after construction, etc 8.3.3 If the trial construction segment does not achieve quality requirements, another trial segment shall be done, with the adjustment of job mix formulae and construction technology until achieving the required quality 8.4 Ground preparation 8.4.1 It should clear and clean dirt and improper materials scattered on the surface intended for asphalt concrete construction with the use of cleaners, blowers, sprinklers (if necessary); and air-drying is compulsory The prepared surface must be extended to each side of the curb at least 20 cm comparing to the width under tack coat or prime coat application 8.4.2 Before paving asphalt concrete on the old road, it should conduct the repair of for holes and potholes and level offset If using cold-mix asphalt stone or cold-mix asphalt concrete for repairing, it should be completed at least 15 days in advance; if using hot asphalt concrete, it should be completed at least day in advance 8.4.3 The prepared surface, or the ground of the base, or the ground of the subgrade for the paving should ensure elevation, flatness, cross slope, longitudinal slope with errors within the permit specified at relevant technical standards 8.4.4 Tack coat or prime coat paving: Before paving asphalt concrete, it should apply tack coat or prime coat 8.4.4.1 Prime coat paving: Perform on surface of non-asphalt subgrade layers (crushed stone aggregate, cement-bound graded aggregate, etc.) Depending on the surface state (open or dense), it shall apply prime coat at the rate from 0.5L/m2 to 1.3L/m2 Medium curing cutback MC30 or MC70 (TCVN 88181:2011) shall be applied: 45 0C±100C for MC30, 700C±100C for MC70 The time from applying prime coat to asphalt concrete paving should be sufficient for 5-10 mm penetration of cutback asphalt into the subgrade and the evaporation of light oil, which shall be determined by Supervision Consultant, about day in common 8.4.4.2 Tack coat paving: Perform on surface of old asphalt road, on asphalt subgrade layers (stone matrix asphalt, penmac, asphalt-treated surface, etc.) or on the surface of paved asphalt concrete Depending on the surface state (open or dense) and duration of old road surface, paving rate of tack coat shall be determined properly Apply cationic slow setting emulsion CSS1-h (TCVN 8817-1:2011) at a rate from 0.3L/m2 to 0.6L/m2; fresh water can be added to the emulsion (1/2 water and 1/2 emulsion), thoroughly stirring before paving Or it can use rapid curing cutback RC70 (TCVN 8818-1:2011) at a rate from 0.3 L/m2 to 0.5L/m2 The time from applying tack coat to asphalt concrete paving should be sufficient (for the performance of CSS1-h or RC70) which shall be determined by Supervision Consultant, usually after at least hours Where the construction at night or moisture weather condition, it can apply rapid setting emulsion CRS -1 (TCVN 8817-1:2011) at a rate from 0.3L/m2 to 0.5L/m2 8.4.5 Only apply dedicated equipment which are capable of controlling dosage and temperature of asphalt for tack coat or prime coat Do not use manual tools for paving 8.4.6 Only carry out tack coat or prime coat work the surface has been fully prepared as specified in 8.4.1, 8.4.2 and 8.4.3 Do not perform at conditions of strong wind, rain, or possible rain Material for tack coat and prime coat should be applied evenly on the surface; apply handheld spray device for insufficient-coated position, and remove for overfilled position 8.4.7 Identify paving position and elevation at two edges of pavement in accordance with design To check elevation with level machine When there is curbstone on sidewalks, mark paving elevation and apply a fluid asphalt layer (or emulsion) onto the curbstone 8.4.8 When using paving machine with elevation automatic adjuster during pavement, prepare carefully standard lines (or a very straight stringing wire, stretching along the pavement and paving trace, or put a bracing bar as a standard line, after taking accurate elevation along the pavement and edge of paving trace) Inspect elevation with level It is necessary to fully comply with the device manufacturer’s instruction in the course of installing standard elevation system, ensuring stable operation of sensors with this standard elevation system 8.5 Carriage of asphalt concrete mixture 8.5.1 Use dump truck to carry asphalt concrete mixture Choose truck with tonnage and number as appropriate to the capacity of the batching plant, paver and carriage distance, assuring continuousness, smoothness in every stage 8.5.2 A suitable carriage plan must be provided so that mixture temperature when reaching destination is not lower than specifications in Table 8.5.3 Truck body for asphalt concrete must be sealed, and evenly spread with a thin layer of soap fluid (or non-adhesive oil) on the wall and bottom of truck body Do not use black oil, diesel oil or other asphalt dissolvent to apply on truck body wall or bottom Truck must be provided with a cover canvas 8.5.4 Each truck transporting asphalt concrete mixture leaving the batching plant must be given with a delivery slip stating mixture temperature, volume, quality (visual check on homogeneousness), time of departure from the batching plant, destination and name of the driver 8.5.5 Before pouring asphalt concrete mixture into the paver hopper, check the mixture temperature with thermometer If the temperature is lower than minimum temperature required for pouring the mixture from truck to the paver hopper (refer to Table 9), then the mixture is rejected 8.6 Paving of asphalt concrete mixture 8.6.1 Asphalt concrete mixture shall be paved by dedicated machine, it is preferable to employ paving machine with automatic elevation adjuster Except for some local narrow positions on which it is impossible to construct with machine, it is allowable to pave manually providing that specifications in 8.6.13 are strictly conformed 8.6.2 Upon the pavement width, we should use (or 3) pavers working at the same time on (or 3) paving traces Pavers shall run on interval of 10 to 20m In case one paver is utilized, paving sequence must be well organized so that distance between endings points of traces in one day is minimized 8.6.3 Before paving, heat the screed plate and spiral conveyor 8.6.4 Truck carrying asphalt concrete mixture will run backward to the paver hopper, and its wheels are in regular and soft contact with rolling shafts of the paver Control so as the bucket pours slowly the mixture down to the center of paver hopper Switch the truck to gear, then the paver will push the truck little by little ahead along with the paver When the asphalt concrete mixture is evenly distributed along the paver spiral conveyor, and full up to 2/3 of spiral conveyor height, the paver goes ahead on defined trace In the course of paving, maintain the mixture to be full of 2/3 spiral conveyor height 8.6.5 During paving of asphalt concrete mixture, it is obligatory to take the paver’s compactor bar (or vibrator on the screed plate) in operation 8.6.6 Depending on thickness of paving trace and machine capacity, choose paver speed as appropriate to prevent crack, tear or uneven surface Paving speed shall be approved by the Engineer and kept unchanged during paving process 8.6.7 Frequently use an iron scale with marking to check paving thickness For machine without automatic adjuster, turn the lifting arm (or lowering arm) gradually so that asphalt concrete layer thickness is not suddenly changed 8.6.8 When the paving machine is in operation, arrange workers to hand a tool following the machine to: - Take small sized particle mixture from the hopper to spread in thin layer along the joints, and to level smoothly on cave, concave and holed surface of joints before rolling - Remove, or compensate for local cave, concave positions on the newly paved asphalt concrete course 8.6.9 Ending each working day, the paver shall run in idle mode to the end of paving trace for about 5-7 m then shut it down 8.6.10 On section with longitudinal slope of more than 40‰, conduct paving of asphalt concrete from the foot slope 8.6.11 In the event the paver is broken while paving (and it takes time to repair), inform the batching plant at once to suspend supply of asphalt concrete and use self-propelled grader to level the remaining quantity of asphalt concrete mixture 8.6.12 In case it is suddenly rainy during paving: - Immediately inform the batching plant for suspending supply of asphalt concrete - If the asphalt concrete layer has been already compacted for 2/3 total turns of required compaction, compaction in the rain will go on until meeting requirements Otherwise, stop compaction and remove asphalt concrete mixture out of the pavement scope Until the pavement is dry, then continue paving 8.6.13 In case it is necessary to pave manually (in narrow positions), be abide by the following specifications: - Use a shovel to scoop asphalt concrete mixture and pour at low level, not throw it from far distance to prevent segregation Use a rake and leveler to spread out the mixture into a flat layer reaching required cross slope, with estimated thickness of 1.35 ÷ 1.45 of designed asphalt concrete layer (determine accurately by field test of compaction) - Manual paving shall be conducted simultaneously with machine paving so that compaction and rolling can go on a same paving trace by manual and machine construction, ensuring no joint on the pavement 8.6.14 Horizontal joint - Horizontal joint, at each working day, must be rectified to be perpendicular with the pavement shaft Before next paving, use machine to cut the end of joint, then use material of prime coat to overcoat the cut, ensuring the existing and new paving trace are in good linking - Horizontal joints of the upper layer and the lower layer must be at least 1m far from each other; - Horizontal joints of the paving trace for the top layer is arranged in alternate of at least 25cm 8.6.15 Longitudinal joints - For longitudinal joints over working day, edges along the previous trace must be removed, use material of prime coat to overcoat the cut, then conduct the paving; - Longitudinal joints of the upper layer and the lower layer must be at least 20cm far from each other; - Longitudinal joints of the upper and lower layer are arranged so that longitudinal links of the top layer of the asphalt concrete pavement coincides with the division of traffic lanes or the road center with lane road 8.7 Rolling on asphalt concrete mixture 8.7.1 Roller on asphalt concrete mixture shall consist of at least light steel wheel roller of 6-8 tons, and heavy steel wheel roller of 10-12 ton and pneumatic tired roller with plane tire following a paver In addition, we can compact with combination of rollers as below: - Pneumatic tired roller in combination with steel wheel roller - Vibrating roller in combination with steel wheel roller - Vibrating roller in combination with pneumatic tired roller 8.7.2 Pneumatic tired roller must have at least wheels, even plain tiers and serviceable with tire pressure up to 0.85MPa Each tire will be pumped with required pressure and pressure difference between two any tires is not more than 0.03 daN/cm Measure shall be taken to adjust capacity of pneumatic tired roller so that weight on each wheel may vary from 1.5 tons to 2.5 tons 8.7.3 Right after the asphalt concrete mixture is paved and preliminary compacted, check and remedy unsmooth places Temperature of asphalt concrete mixture after paving and in rolling must be closely controlled to control it ranges in the defined limits (Table 9) 8.7.4 Rolling diagram, rolling speed and combination of rollers, turns of rolling over the same point of each roller to reach required density is determined on the trial paving trace 8.7.5 As far as the paver goes, roller must closely follow In preliminary rolling turns, the active wheel will be nearest to the screed plate of the paver Rolling process of rollers must be carried out on uninterrupted basis while the asphalt concrete mixture still keeps the effective rolling temperature, no less than temperature at rolling end (Refer to Table 9) 8.7.6 Track of rollers must be at least 20cm overlapped First rolling turns are for longitudinal joints, then conduct rolling from the external edge in parallel with the center and move towards the center When rolling in curve with super-elevation, rolling will be made from the lower side then moving toward the upper side Rolling turns are not stopped at points within meter from the ending point of previous turn 8.7.7 In the course of rolling, for steel wheel roller, moisten the steel wheel with water For pneumatic tired roller, apply anti-adhesion oil on the wheel surface for the first few turns, and when the wheel has temperature which is approximately equal to asphalt concrete mixture temperature, adhesion will not occur Do not use water to moisten the pneumatic tired wheel Never use diesel, fuel oil or asphalt dissolvent to apply on the roller wheel 8.7.8 When the roller starts, or changes its direction, moves backward or forward and so on, handle with care slowly, not change suddenly so that the asphalt concrete mixture is free from movement and tear 8.7.9 Rollers and other heavy machines shall in no case stop on the asphalt concrete layer which is not compacted and entirely cool down - 8.7.10 While conducting compaction process, if the asphalt concrete layer is cracked, it is necessary to find out the reason and adjust accordingly (temperature, compaction speed, load used for compaction,…) Supervision, Inspection and Acceptance of Asphalt Concrete layer 9.1 Inspection should be conducted on a regular basis before, during and after constructing asphalt concrete layer The following regulations on inspection works are only at minimum level, based on actual site conditions, Supervision Consultant can adjust inspection frequency accordingly 9.2 Check site before conducting construction, including the following items: - Conditions of the layer on which asphalt concrete layer shall be directly placed on, longitudinal and cross slope gradient, elevation, width - Conditions of Prime coat layer and Tack coat layer; - Standard elevation system; - Paver, compactor, communication devices, construction team, traffic safety and labor safety system 9.3 Check material quality 9.3.1 Check for acceptance of the material prior to construction - Asphalt: check quality criteria in accordance with TCVN 7493:2005 (except Kinematic Viscosity at 135oC) for each delivery of material - Materials of tack coat and prime coat: check quality criteria of the materials adopted for construction for each delivery of material - Crushed stone, sand, mineral powder: check criteria in accordance with articles 5.1, 5.2 and 5.3 for each delivery of material 9.3.2 Check during process of asphalt concrete production: in accordance with regulations at Table 10 Table 10 – Check materials during process of asphalt concrete production Material type Checking Frequency Checking Basis criteria location Crushed stone - Grain content time/2days or Crushed stone’s Table delivery site - Elongation and time/200m3 Flakiness content - Content of dust and clay Sand - Grain content time/2days or Sand’s delivery Table time/200m3 site - Sand Equivalent coefficient ES Mineral - Grain content time/2days or Storage Table time/50ton powder - Plasticity index Asphalt - Penetration time/day Preliminary TCVN 7493 : Asphalt kettle 2005 - Yielding point NOTE: For batching plants that continuously produce concrete: frequency of checking aggregate materials (crushed stone, sand, mineral powder) is time/day 9.4 Check at batching plant: in accordance with regulation in Table 11 Table 11 – Check at batching plant Item Criteria/method Frequency Checking s location Materials at - Grain content time/day Hot bin hot bin Asphalt - Grain content time/day On truck or collecting concrete - Asphalt content hopper of Paver formula - Marshall stability Basis Grain content of each bin Approved criteria of asphalt concrete mix - Air void - Asphalt Material Weighing system Thermometer system Asphalt concrete sample’s volumetric mass - Maximum density of asphalt concrete - Check calibration certificate and check visually - Check calibration certificate and check visually Thermometer time/2days time/day All plants batching Batching plant technical specifications time/day All plants batching Batching plant technical specifications time/hour Preliminary Asphalt kettle, mixing drum Drum dryer temperature Temperature of Aggregate material after drying Mixing temperature Mixing duration Temperature of the mixture after pouring out of mixing drum Thermometer time/hour Thermometer Each batch Each batch Each batch Clock Thermometer In accordance with 7.3.6 and Table In accordance with 7.3.9 mixing Mixing drum Table mixing Control room In accordance with 7.3.11 Table mixing Control room 9.5 Check during conducting construction: in accordance with Table 12 Item Mixture temperature on truck Mixture temperature while paving Mixture compaction temperature Thickness of asphalt concrete layer Compactio n work Table 12 – Check during constructing asphalt concrete layer Criteria/methods Frequency Checking Basis location Thermometer Each truck Truck body Table Thermometer 1point/50m Right Paver Thermometer point/50m Pavement Table Penetrating steel point/50m rod Pavement Design document Compaction plan, On a speed, times, basis weight, other behind Table regular Pavement In accordance with 8.3.2 and 8.7 Traverse regulations for compaction work Visual Each joint observation and longitudinal joints Roughness 3-meter Ruler after preliminary compaction 25m/cross section Pavement In accordance with 8.6.14 and 8.6.15 Pavement Gap is less than 5mm 9.6 Check during asphalt concrete pavement acceptance Item Width Cross Table 13 – Tolerance of geometrical properties Method Frequency Tolerance Regulations on unsatisfied measuring points ratio Steel ruler 50m / cross - 5cm Total number of narrow section sections does not exceed 5% of road length Level 50m / cross ≥ 95% of total number machine section of measuring points ± 0,5% slope: Lower layer - Upper layer Thickness Core drilling - Lower layer - Upper layer - Elevation - Lower - layer Upper layer Level machine ± 0,5% 2500 m (or ≥ 95% of total number length 330m of 2- ± 8% of measuring points, lane road) / thickness remaining 5% does not group of ± 5% exceed 10mm samples thickness 50m / point ≥ 95% of total number of measuring points, - 10mm; remaining 5% does not +5mm exceed ±10mm ± 5mm 9.6.2 Pavement roughness: use IRI equipment to check pavement’s roughness Reports on IRI checking results are made on the basis of 100m length; if the pavement’s roughness is not good, IRI reports shall be made on the basis of equal or less than 50m length In case that the length asphalt concrete section is short (≤ 1km), roughness shall be checked by using 3-meter straight edge Specifications for acceptance is shown in Table 14 Table 14 – Specifications for acceptance of Roughness Item Frequency Requirements Roughness IRI Whole pavement’s length, all In accordance with TCVN lanes 8865:2011 Roughness measured 25m / lane In accordance with TCVN 8864:2011 by 3-meter straight edge (when pavement length is ≤ 1km) 9.6.3 Pavement Macrotexture Depth: In accordance with Acceptance standards at Table 15 Table 15 - Acceptance standards for Pavement Macrotexture Item Frequency Requirements Measuring Pavement measuring points / Km / In accordance with TCVN Macrotexture Depth Using a lane 8866:2011 Volumetric Technique 9.6.4 Compaction density: Compaction density (K) of asphalt concrete layers are not allowed to be less than 0,98 K = ɣtn/ɣo In which: - ɣtn: Average volumetric mass of asphalt concrete after using for construction, g/cm (determined from drilling sample) - ɣo: Average volumetric mass of asphalt concrete at batching plant corresponding to station of checking, g/cm3 (determined from Marshall sample at batching plant in accordance with requirements in Table 11 or from asphalt concrete sample at corresponding stations) Frequency of test: 2500m2 pavement (or 330m length of 2-lane road) / group of drilling samples (used for drilling samples of which thickness were determined in accordance with Table 13) 9.6.5 Aggregate components, asphalt content of original samples taken from pavement section corresponding to station of checking must satisfy approved asphalt concrete formula and tolerance as stated in Table Frequency of test: 2500m2 pavement / sample (or 330m length of 2-lane road/ sample) 9.6.6 Marshall stability is checked based on drilling sample: use sample of which thickness and compactness have been checked Marshall stability must be ≥ 75% stability values stated in Table and Table in conformity with specific asphalt concrete type Plasticity and Void ratio (determined based on drilling sample) should also be within allowable range (Table and Table 4) 9.6.7 Adhesive strength between asphalt layer and under layer must be good and visually checked based on drilling samples 9.6.8 The quality of joints shall be visually checked Joints must be straight, smooth, have no blister, notch or gap 9.7 Inspection documents include: - Acceptance result of input material; - Preliminary design; - Complete design; - Relation graph of feed rate (ton/hour) and conveyor speed (m/minute) for crushed stone and sand - Approved design – formula of asphalt concrete - Documents of trial Paving works, including the Consultant’s decision on compaction temperature, compaction plan, number of compaction passes for one point,… - Diary of each asphalt concrete delivery truck: mass of the mixture, mixture temperature when being poured from mixing drum into truck, time of delivery, mixture temperature when being poured into paving machine; weather condition when paving work is conducted, station of paving work; - Checking result documents in accordance with regulations mentioned in Table 10 ~ Table 15 10 Labor safety and environmental protection 10.1 At the location of asphalt concrete batching plant 10.1.1 Strictly comply with existing regulations on fire prevention, lightning protection, environmental protection, labor safety, electric operation 10.1.2 At the locations where fire can possible occur (stockpile, storage of asphalt concrete, fuel, mixing machine…), there should be fire fighting equipment, dry sand fire bucket, foam fire extinguisher, water tank and emergency exits 10.1.3 Asphalt batching location should be at least 50km away from flammable structures and storages Any spilled asphalt should be cleaned and covered with sand 10.1.4 Batching plant’s dust filter must be well functioned 10.1.5 Regarding the operation of batching plant’s machines, it is essential to: - Check all machines and equipment; - Start the machine and check the flow of asphalt in all conduit pipes, it may be necessary to warm up the pipes and valves so that asphalt can flow easily - Blowtorch shall only be ignited in the drum dryer after all machines are tested without load 10.1.6 Blowtorch operation sequence must comply with batching plant’s instruction guide When igniting and adjusting the blowtorch, worker must stand on the side of ignite chamber instead of facing it 10.1.7 It is not allowed to us drum dryers with defects in ignite chamber, blowtorch or when flame can be seen coming out of ignite chamber’s gaps 10.1.8 At the location of automatically operated asphalt concrete batching plants, the following regulations shall be ensured: - Operation station is at least 15m away from batching plant; - Before each working shift, it is necessary to check wire system, operating device and each component of the batching plant - When starting the machine, it is necessary to strictly comply with regulated operation instructions for each type of batching plant (from feeding input materials to taking mixture out of batching plant) 10.1.9 When checking and conducting technical reparation for asphalt kettle, storage tank and wet locations, it is only allowed to use mobile electric light with capacity of 12V When checking and conducting technical reparation inside drum dryer and mixing drum, it is mandatory to wait for these components to cool off 10.1.10 All workers of asphalt batching plants must be trained on labor safety and provided with basic technical information on asphalt concrete batching plant’s operation process, provided with clothes, glasses, gloves, work shoes in consideration of each task 10.1.11 A medical staff must be always on duty at batching plant, especially to provide first aid for workers who got burns, with sufficient equipment and medical drugs in accordance with existing regulations 10.2 At the location of paving asphalt concrete 10.2.1 Before constructing asphalt concrete, signboard “Construction site” should be placed at both ends of the construction area, assign personnel and detour signboard to guide transportation vehicles; regulate schedules and movements of delivery trucks, ensure lightning condition for night shifts 10.2.2 Workers assisting paving machines should be equipped with work shoes, gloves, masks and protective clothes that are suitable for working with and stepping on high-temperature mixture 10.2.3 Before each working shift, all construction machines and equipment should be checked, repaired and adjusted to ensure functionality Machines’ conditions and defects should be noted in construction diary and reported to construction foreman on time 10.2.4 Regarding asphalt concrete paving machine, it is necessary to check the feed conveyor and warm up the screed plate Before lowering the hanging component of the paving machine, it is necessary to ensure that nobody is standing right behind the paving machine Appendix A (Regulations) Guidance for Asphalt Concrete Mixture Design A Preliminary Design A.1.1 Test for particle size determination of each material: crushed stone, sand and mineral powder (once materials satisfy relevant technical specifications stated in section 5.1; 5.2 and 4.3) To calculate average particle size distribution on each sieve number of crushed stone, sand (based on results of grading analysis) and mineral powder (based on grading analysis results) A.1.2 On the fundamental of average particle size results on each sieve number of each aggregate, to calculate proportion of aggregates mixing to select grading curve of aggregates mixture satisfying requirements in Table and Table in corresponding with each type of designed asphalt concrete A.1.3 Based on mixing proportion of aggregates selected in A.1.2, prepare about 25kg of aggregates mixture, dry them and sieve them into separate particle sizes Mix particle sizes into 20 separate mixture portions, each one weights about 1100gram to make into sample combinations including samples each one, for standard Marshall testing method With asphalt concrete type tested with modified Marshall method, prepare volume of aggregate mixture sample of about 80kg to mix into 20 separate mixtures portions, each one weights about 4000gram A.1.4 Put asphalt into oven and heat it to defined mixing temperature (Table 9) Then put the aggregates mixture in another oven and heat to higher temperature than mixing temperature of 15oC A.1.5 Mix aggregates mixture sample combinations (each combination includes samples) with asphalt contents (by total weight of asphalt concrete mixture) verifying by 0.5% around the reference asphalt content With each sample combination, samples will be compacted in Marshall mold and sample of no compaction will be tested for determining maximum density and specific volume of asphalt concrete A.1.6 Determine maximum density of asphalt concrete for samples of asphalt concrete corresponding with asphalt contents NOTICE A1: It is possible to test determining only one maximum density value of AC mixture in proportion with estimated optimum asphalt content (normally at middle range of reference asphalt content) Then use this result to calculate maximum density values of AC mixture in proportion with other asphalt contents In this case, we only produce samples with estimated optimum asphalt content, to be tested for maximum density and take average value A.1.7 Compact sample combinations (each one including samples) with Marshall method with predefined compaction times (Table or Table 4) corresponding with designed asphalt concrete type Compaction temperature shall follow specifications (Table 9) A.1.8 Test for determining volumetric mass of asphalt concrete of compacted samples Calculate average asphalt concrete volumetric mass (g/cm 3), average air voids (%), average voids in the mineral aggregate (%) for each sample combination A.1.9 Soak the compacted sample in thermostatic tank at 60 oC in required time, then have it compressed on Marshall Compressor to determine Marshall stability and plastic flow Calculate values of average stability, average plastic flow for each sample combination A.1.10 Choose Marshall based optimum asphalt content: From testing results of sample combinations, set up relation graph between asphalt content with parameters: average stability, average plastic flow, average air voids, and average voids in the mineral aggregate, average volumetric mass Based on values specified in Table or Table 4, determine ranges of asphalt content meeting each parameter: stability at 60oC, plastic flow, air voids, voids in the mineral aggregate Determine range of asphalt content satisfying all above parameters Value of asphalt content which is in the middle of asphalt content satisfying all above parameters is often selected as Marshall based optimum asphalt content With dense graded asphalt concrete, it is preferable to opt optimum asphalt content so that air voids is about 4% Determine value of asphalt concrete volumetric mass corresponding to optimum asphalt concrete as basis to calculate compaction density K A.1.11 Prepare samples of asphalt concrete mixture with particle size as in A.1.2, with optimum asphalt content specified in A.1.10, cast Marshall samples to determine remaining stability and calculate average remaining stability of samples If average remaining stability meets requirements in Table or Table 4, corresponding with designed asphalt concrete type, then the optimal asphalt content selected following A.1.10 is reasonable, and we now proceed to complete design phase A.2 Complete Design A.2.1 Take the batching plant’s conveyor of crushed stone and sand into operation Formulate a relation curve between feeding speed (tons/hour) and conveyor velocity (meters/minute) for crushed stone and sand Determine material moisture value with the aim of accuracy calibration When formulating the relation curve, there must be at least values in proportion with conveyor velocities: 20%, 50% and 70% of maximum speed Adjust so that dimension of hopper mouth is the same of times larger than maximum particle size of aggregates A.2.2 Get the whole batching plant into trial operation likewise mass scale production but aggregates are not mixed with asphalt and stone powder Based on results in A.2.1, calculate conveyor speed for crushed stone, sand to reach defined ratio of crushed stone and sand determined in A.1.2 A.2.3 When the batching plant is in sound operation, sample aggregates from hot bin hopper and mineral powder for grading analysis, then calculate mixing proportion of aggregates so that grading curve of aggregates is similar to that in A.1.2 Carry out mixing design by Marshall Procedure of testing to determine grading curve and optimum asphalt content by Marshall are stated from A.1.1 to A.1.10 A.2.4 Prepare samples of asphalt concrete with particle size and optimum asphalt content selected by A.2.3., cast Marshall samples to define remaining stability and calculate average remaining stability of these samples If the average remaining stability satisfies requirement in Table or Table corresponding with designed asphalt concrete type, then the selected optimum asphalt concrete is reasonable and we now proceed to trial production and trial paving NOTICE A2: For continuous batching plant, completed design is preliminary design so there is no need to perform step A.2.3 and A.2.4, carry as follows: - Set up relation curve between feeding speed (tons/hour) and conveyor speed (meters/minute) for each aggregate, similarly to description in A.2.1 Based on results of the preliminary design, adjust speed of conveyor as appropriate to mixing ratio of each kind of aggregate Take the aggregate feeding system into service, wait until the system becomes stable then take sample of aggregates before putting the same into drying drum (or mixer) If aggregates of this mixture is suitable with those in preliminary mix design, then conveyor speed adjustment is satisfactory – end complete mix design phase A.3 Setting up formulae of asphalt concrete mixture production A.3.1 Trial production: On the basis of complete design result, conduct trial production of asphalt concrete at the batching plant with weight ranging from 60 to 100 tons A.3.2 Check quality of trial produced asphalt concrete Examine the conformity of particle size, asphalt content, Marshall properties against complete design A.3.3 Trial paving: Pave asphalt concrete on a section of at least 100m length, and minimum width of paving traces Implement construction alternate: Spreading materials of prime coat, tack coat; ratio of prime coat and tack coat spreading; allowable time of asphalt concrete paving after applying prime coat or tack coat; thickness of asphalt concrete layer that has not been compacted; paving temperature; rolling temperature at the beginning and ending; rolling diagram of different types of rollers, and number of rolling turns necessary to reach compaction density A.3.4 Inspect quality of asphalt concrete after trial construction: compaction density, thickness, flatness and roughness after execution A.3.5 If laboratory and field test results show that asphalt concrete mixture of trial paving comply with technical specifications in Table or Table 4, corresponding with DGAC and OGAC, and it is able to construct with available machines, ensuring requirements on density, thickness and flatness and so on, the Contractor shall submit formulae for asphalt concrete production (as instructed in 6.3.3) to the Engineer and the Employer for approval Appendix B (For reference) Instruction for sieve size conversion in Lab into sieve size in batching plant Lab sieve size (mm) 2.36 4.75 9.5 12.5 19.0 25.0 31.5 37.5 50 Batching sieve size (mm) 2.5 11 14 22 29 35 41 57 [...]... Requirements 1 Roughness IRI Whole pavement’s length, all In accordance with TCVN lanes 8865 :2011 2 Roughness measured 25m / 1 lane In accordance with TCVN 8864 :2011 by 3-meter straight edge (when pavement length is ≤ 1km) 9.6.3 Pavement Macrotexture Depth: In accordance with Acceptance standards at Table 15 Table 15 - Acceptance standards for Pavement Macrotexture Item Frequency Requirements Measuring Pavement... pavement, prepare carefully standard lines (or a very straight stringing wire, stretching along the pavement and paving trace, or put a bracing bar as a standard line, after taking accurate elevation along the pavement and edge of paving trace) Inspect elevation with level It is necessary to fully comply with the device manufacturer’s instruction in the course of installing standard elevation system,... rate of tack coat shall be determined properly Apply cationic slow setting emulsion CSS1-h (TCVN 8817-1 :2011) at a rate from 0.3L/m2 to 0.6L/m2; fresh water can be added to the emulsion (1/2 water and 1/2 emulsion), thoroughly stirring before paving Or it can use rapid curing cutback RC70 (TCVN 8818-1 :2011) at a rate from 0.3 L/m2 to 0.5L/m2 The time from applying tack coat to asphalt concrete paving... which shall be determined by Supervision Consultant, usually after at least 4 hours Where the construction at night or moisture weather condition, it can apply rapid setting emulsion CRS -1 (TCVN 8817-1 :2011) at a rate from 0.3L/m2 to 0.5L/m2 8.4.5 Only apply dedicated equipment which are capable of controlling dosage and temperature of asphalt for tack coat or prime coat Do not use manual tools for paving... aggregate, cement-bound graded aggregate, etc.) Depending on the surface state (open or dense), it shall apply prime coat at the rate from 0.5L/m2 to 1.3L/m2 Medium curing cutback MC30 or MC70 (TCVN 88181 :2011) shall be applied: 45 0C±100C for MC30, 700C±100C for MC70 The time from applying prime coat to asphalt concrete paving should be sufficient for 5-10 mm penetration of cutback asphalt into the subgrade... Inspect elevation with level It is necessary to fully comply with the device manufacturer’s instruction in the course of installing standard elevation system, ensuring stable operation of sensors with this standard elevation system 8.5 Carriage of asphalt concrete mixture 8.5.1 Use dump truck to carry asphalt concrete mixture Choose truck with tonnage and number as appropriate to the capacity of the batching... items: - Conditions of the layer on which asphalt concrete layer shall be directly placed on, longitudinal and cross slope gradient, elevation, width - Conditions of Prime coat layer and Tack coat layer; - Standard elevation system; - Paver, compactor, communication devices, construction team, traffic safety and labor safety system 9.3 Check material quality 9.3.1 Check for acceptance of the material prior... or the ground of the base, or the ground of the subgrade for the paving should ensure elevation, flatness, cross slope, longitudinal slope with errors within the permit specified at relevant technical standards 8.4.4 Tack coat or prime coat paving: Before paving asphalt concrete, it should apply tack coat or prime coat 8.4.4.1 Prime coat paving: Perform on surface of non-asphalt subgrade layers (crushed... Table 15 Table 15 - Acceptance standards for Pavement Macrotexture Item Frequency Requirements Measuring Pavement 5 measuring points / 1 Km / 1 In accordance with TCVN Macrotexture Depth Using a lane 8866 :2011 Volumetric Technique 9.6.4 Compaction density: Compaction density (K) of asphalt concrete layers are not allowed to be less than 0,98 K = ɣtn/ɣo In which: - ɣtn: Average volumetric mass of asphalt... them and sieve them into separate particle sizes Mix particle sizes into 20 separate mixture portions, each one weights about 1100gram to make into 5 sample combinations including 4 samples each one, for standard Marshall testing method With asphalt concrete type tested with modified Marshall method, prepare volume of aggregate mixture sample of about 80kg to mix into 20 separate mixtures portions, each ... Science and Technology NATIONAL STANDARD TCVN 8819: 2011 Specification for Construction of Hot Mix Asphalt Concrete Pavement and Acceptance Scope of application 1.1 This standard provides technical... on Technical Standards and Regulations TCVN 8819: 2011 is composed by Institute of Transport Science and Technology, recommended by Ministry of Transport, verified by Directorate for Standards,... ≥14 - Maximum nominal particle size 9.5mm ≥13 Test method TCVN 8860-1 :2011 TCVN 8860-12 :2011 TCVN 8860-9 :2011 TCVN 8860-10 :2011 - Maximum nominal particle size 12.5mm - Maximum nominal particle
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