EN_TCVN8820-2011

VIETNAMESE STANDARD TCVN 8820 : 2011 Standard Practice for Asphalt Concrete Mix Design Using Marshall Method TABLE OF CONTENT Application scope Reference Terms and Definition Classification of asphalt concrete Principle of asphalt concrete mix design using Marshall method Bases for asphalt concrete mix design using Marshall method Stages and content of asphalt concrete mix design 10 Procedure of asphalt concrete mix design using Marshall method 13 General requirements for Site Laboratory 25 Appendix A (for reference) Guideline for mixing design .27 Appendix B (for reference) Volumetric characteristics of asphalt concrete mixture Report on AC mix design with Marshall method……………………………………………………………………….34 Foreword TCVN 8820: 2011 is compiled by Institute of Transport Science and Technology, proposed by MOT, authenticated by Directorate for Standards, Metrology and Quality, declared by Ministry of Science and Technology STANDARD PRACTICE FOR ASPHALT CONCRETE MIX DESIGN USING MARSHALL METHOD Application scope 1.1 This standard sets out guidelines of asphalt concrete mix design using Marshall method 1.2 This standard applies to the type of dense asphalt concrete mixture using binder as asphalt or polymer asphalt 1.3 For types of Gap-graded HMA, Open-graded HMA, and stone matrix asphalt, in addition to the application of this standard for mixture design, it also applies additional related standard specified in correspondent specification for construction of asphalt concrete pavement and acceptance 1.4 Technical requirements as bases for the acceptance of AC mix design are regulated in specification for construction of asphalt concrete pavement and acceptance Reference Following reference documents are necessary for the application of this Standard For reference documents with issuance year specified, the version of that year will be applied For reference document excluding the issuance year, the most updated version, including modifications, will be applied TCVN 7572-2: 2006 Aggregates for concrete and mortar – Test methods - Part 2: Determination of particle size distribution TCVN 7501:2005 - Bitumen − Test method for determination of density (Pycnometer method) TCVN 8860-1: 2011 Asphalt Concrete – Test methods – Part 1: Determination of Marshall Stability and Plastic Flow TCVN 8860-4: 2011 Asphalt Concrete – Test methods – Part 4: Determination of Maximum Specific Gravity and Density of loose Bituminous Paving Mixtures TCVN 8860-5: 2011 Asphalt Concrete – Test methods – Part 5: Determination of Bulk Specific Gravity and Unit Weight of Compacted Bituminous Mixtures TCVN 8860-9: 2011 Asphalt Concrete – Test methods – Part 9: Determination of Air Voids TCVN 8860-10: 2011 Asphalt Concrete – Test methods – Part 10: Determination of Voids in Mineral Aggregate TCVN 8860-11: 2011 Asphalt Concrete – Test methods – Part 11: Determination of Voids filled with asphalt TCVN 8860-12: 2011 Asphalt Concrete – Test methods – Part 12: Determination of Remaining Stability TCVN 8819 : 2011 Specification for construction of asphalt concrete pavement and acceptance TCVN 4195:1995 Soil - Method of laboratory determination of specific weight AASHTO T 84-2000 Standard Method of Test for Specific Gravity and Absorption of Fine Aggregate AASHTO T 85-2000 Standard Method of Test for Specific Gravity and Absorption of Coarse Aggregate Terms and definition 3.1 Hot mix asphalt-HMA The mixture includes aggregates (macadam, sand, mineral powder) with a defined mixing ratio, dried and mixed evenly and mixed with asphalt in accordance with designed ratio 3.2 Dense-graded HMA An AC mixture type includes coarse aggregate, medium-sized aggregate and fine aggregate who volumes are relatively equal, so that these aggregates are well-compacted at compaction Densegraded HMA has small air void content, usually 3-6% 3.3 Gap-graded HMA An AC mixture type includes a great amount of coarse aggregate fine aggregate, and a very small amount of medium aggregate Grading curve of this type tends to be nearly horizontal at medium aggregate zone With this type, coarse aggregates are well-associated to each other, but tend to be segregated during spreading Gap-graded HMA usually have air void content greater than Densegraded HMA 3.4 Open-graded HMA An AC mixture type includes fine aggregate accounting for a small proportion in the mixture Grading curve tends to be nearly vertical at medium aggregate zone, nearly horizontal and value near zero (0) at fine aggregate zone This AC mixture has great air void because fine aggregate volume is not sufficient enough to fill the voids between the coarse aggregates It is usually referred to as porous asphalt Porous asphalt has the biggest air void content comparing to Dense-graded HMA and Opengraded HMA Porous asphalt for the construction of base course, in which mineral powder is not used commonly, has air void from 7% to 12% 3.5 Asphalt concrete with high roughness - higher slip resistance capacity It is used for surface coating, which helps to prevent water splashed caused by vehicle running at high speed, increase slip resistance and significantly reduce road noise from running vehicles Porous asphalt is usually used with air void content of 15-22% (Open graded friction course – OGFC or Porous friction course - PFC) or Gap-graded HMA with air void content of 10-15% (Very thin friction course - VTO) The modified asphalt should be used to produce this kind of AC 3.6 Stone matrix asphalt or Stone mastic asphalt -SMA Is a type of gap-graded HMA mixture This asphalt concrete mixture includes asphalt, aggregate and fiber SMA usually contains mineral powder and asphalt volume higher than Dense-graded HMA SMA has a wide range of air void content, from 2% to 8%, depending on the use of SMA for surface coarse or base course 3.7 Maximum size of aggregate The maximum aggregate size is defined as the smallest sieve size that requires 100% passing In this Standard, square-eye sieve is used for aggregate content test 3.8 Nominal maximum size of aggregate Nominal maximum aggregate size is the largest sieve that retains 10% or more of the total aggregate mixture 3.9 Coarse aggregate Coarse aggregate includes the particles that retain on 4.75 mm sieve They are mineral products from crushed rock or natural gravel, also called as macadam 3.10 Fine aggregate Fine aggregate includes the particles that all passes through 4.75 mm sieve and retain on 0.075 mm sieve They are natural mineral products (natural sand) or products from crushed rock, also called as sand 3.11 Mineral filler The product is finely crushed from carbonate rock (limestone calcite, dolomite ), from furnace slag base or cement, at least 70% passing through 0.075 mm sieve 3.12 Asphalt content The amount of asphalt in asphalt concrete mixture There are two way to express asphalt content: Percent by mass of AC mixture (coarse aggregate, fine aggregate, mineral filler, asphalt), or percent by mass of aggregates (coarse aggregate, fine aggregate, mineral filler) Percent by mass of AC mixture, symbolized as Pb, is applied widely in the world and in this Standard 3.13 Optimum asphalt content Asphalt content is determined when designing AC, corresponding to a designated aggregate mixing rate, meeting all technical requirements specified for the aggregate and AC regulated in Specification for Construction of Asphalt Concrete Pavement and Acceptance 3.14 Absorbed Asphalt Content Amount of asphalt adsorbed by aggregate through voids on surface, expressed as the percent by mass of aggregate; symbolized as Pba 3.15 Effective Asphalt Content Effective asphalt content is the total asphalt content minus the asphalt absorbed by the aggregate, on a volume basis, symbolized as Pbe, expressed by percent by mass of AC mixture Effective asphalt content makes up the outer cover of aggregates and determines physical-mechanical properties of AC mixture 3.16 Maximum Specific Gravity Specific gravity of asphalt concrete mixture not having air void (air void: 0), symbolized as Gmm 3.17 Bulk Specific Gravity The ratio of a compacted HMA weight to the weight of an equal volume of water at a same temperature 3.18 Unit Weight Weight of a unit volume of compacted HMA 3.19 Air Voids Air voids are small airspaces or pockets of air that occur between the coated aggregate particles in the final compacted mix Air void is represented by the percentage of voids in the compacted HMA mass, symbolized as Va 3.20 Voids in the Mineral Aggregate Voids in mineral aggregate, VMA, are the air-void spaces that exist between the aggregate particles in a compacted HMA, including air voids and effective asphalt content VMA is represented by the percentage in the compacted HMA mass 3.21 Voids Filled with Asphalt The voids filled with asphalt (VFA) is the percentage of voids in the mineral aggregate (VMA) filled with effective asphalt content Classification of asphalt concrete Some major classifications as follows: 4.1 Classification by the biggest nominal size of the aggregate particle According to this classification, asphalt concrete is usually classified into types with the biggest nominal particle size as: 37.5 mm; 25.0 mm; 19.0 mm; 12.5 mm; 9.5 mm and 4.75 mm (corresponding to the classification according to the biggest particle size of 50 mm, 37.5 mm, 25.0 mm, 19.0 mm, 12.5 mm and 9.5 mm) 4.2 Classification by property of graded mix According to property of graded mix, asphalt concrete is classified into: a) Dense graded mix; b) Gap graded mix; c) Open graded mix 4.3 Classification by air void According to air void, asphalt concrete is classified into: - Dense asphalt concrete with air void of 3% - 6% - Void asphalt concrete with air void is greater than % 4.4 Classification by function in pavement structure According to function in pavement structure, asphalt concrete is classified into: - Asphalt concrete with high roughness, increased slip resistance: used for high-level motorways, highways, dangerous road sections This layer is coated on the surface of asphalt concrete, shortly after construction of underneath asphalt concrete layers or coated when upgrading the pavement - Surface course mixture, including: + Wearing course mixture: usually apply dense asphalt concrete + Binder course mixture: usually apply dense asphalt concrete - Both dense asphalt concrete and void asphalt concrete can be used Void asphalt concrete is cheaper because of not using mineral powder and having lower asphalt content comparing to dense asphalt concrete - Used for surface course at area having vehicle load not so great, at sidewalks, and at lane for bicycle and non-motored vehicles It can be used as a thin compensation layer before spreading asphalt concrete Aggregate of Sand-asphalt mixture is crushed sand, natural sand or a mixture of both Principle of asphalt concrete mix design using Marshall method Asphalt Concrete Mix Design Using Marshall Method aims to find the optimum asphalt content corresponding to the selected aggregate mixture The mix design must comply with the following requirements: - All the materials used (crushed stone, sand, mineral powder, asphalt) must satisfy physicalmechanical criteria prescribed in Specification for construction of asphalt concrete pavement and acceptance - Grading curve of the aggregate mixture after mixing must be within the limits of the grading envelope prescribed in Specification for construction of asphalt concrete pavement and acceptance - The optimum asphalt content selected should satisfy criteria related to volume properties (air void, voids in the mineral aggregate, etc.), testing criteria according to Marshall method (stability, flow, etc.), and additional criteria (if any) in accordance with Specification for construction of asphalt concrete pavement and acceptance Bases for asphalt concrete mix design using Marshall method 6.1 In Specification for construction of asphalt concrete pavement and acceptance, bases for asphalt concrete mix design and selection of optimum asphalt content are prescribed as follows: - Technical requirements of physical-mechanical properties of coarse aggregate (macadam); fine aggregate (sand); mineral powder (asphalt concrete type using mineral powder) - Limits of grading envelope of aggregate mixture: sieve size, sieve passing limits (upper, lower bounds) for each sieve size - The appropriate asphalt type and technical requirements of physical-mechanical properties of asphalt; The reference asphalt level (as percentage in total volume of asphalt concrete mixture) - Temperature for mixing asphalt concrete and temperature of casting sample of asphalt mixture by Marshall Method - Sample compaction by Marshall method (conventional Marshall method, upgraded Marshall method), number of compaction blow per face - Technical requirements of volumetric criteria of asphalt concrete sample compacted by Marshall method: Air voids (Va); Voids in the Mineral Aggregate (VMA), voids filled with asphalt (VFA) - Technical requirements of criteria of asphalt concrete sample by Marshall method: Stability, Flow, retained Marshall stability - Technical requirements of other criteria related to the quality of materials, quality of asphalt concrete (if prescribed in Specification for construction of asphalt concrete pavement and acceptance) 6.2 The mix design of asphalt concrete by Marshall method must satisfy the above mentioned criteria Stages and content of asphalt concrete mix design Mix design of asphalt concrete is related closely to the construction progress of the construction work Mix design of asphalt concrete includes stages: - Stage 1: Preliminary design or cold bin mix design; - Stage: Hot bin mix design; - Stage 3: Job-mix formula verification; - Stage 4: Control routine construction Each stage in the design has its own role All stages are important, and it cannot skip any stage The content of asphalt concrete mix design at each stage is summarized in Figure 7.1 Preliminary design (Stage 1) 7.1.1 The main purpose of the preliminary design is to determine quality of aggregates available at construction site; compare with technical requirements to determine the suitability or not; and to justify if the aggregate materials can be used to produce asphalt concrete which satisfy requirements of grain composition and criteria prescribed for asphalt concrete or not 7.1.2 In case where there are multiple sources of construction material, it should conduct multiple designs with different sources of material in order to determine an aggregate mixture with lowest price and the satisfaction of all technical requirements set out 7.1.3 At this stage, material samples for the design are taken from supply source or cold bin of mixing plant Grain composition of aggregate mixture are typically selected within the restricted domain of the grain composition chart prescribed in Specification for construction of asphalt concrete pavement and acceptance 7.1.4 The order of asphalt concrete mix design: steps (Figure 1), see Section for details 7.1.5 Meaning of preliminary design: - To confirm the suitability of aggregates and the asphalt concrete mixture using these aggregates regarding to technical requirements of the project This stage is particularly meaningful if there are no data about the aggregate sources available at the construction site; - As a basis for calculating construction cost; - As a basis to carry out hot bin mix design 7.2 Hot bin mix design (Stage 2) 7.2.1 The purpose of this stage is to find the actual grading composition of the aggregate mixture and optimal asphalt content when producing asphalt concrete mixture at batching plant Grain composition of aggregates in this stage shall be the same as at preliminary design stage 7.2.2 This stage shall be carried out after having results from preliminary design 7.2.3 The order of asphalt concrete mix design: steps (Figure 1), similar as preliminary design stage; the difference: aggregates are taken from hot bin of batching plants for test and design Figure 1: Stages and design order of asphalt concrete mixture 7.2.4 Right before implementing hot bin mix design, it should carry out calibration for cold bins of the batching plant and set up the chart representing the relationship between cold aggregate provision speed and conveyor speed The implementation as follows: - Adjust the size of bin so that is will be equal or times as the size of the biggest particle of the aggregate - Operate the sand/aggregate conveyor of the batching plant with speed of 20%, 50% and 70% of the maximum speed Establish the curve representing the relationship between the aggregate provision speed (ton/hour) and conveyor speed (m/minute) for macadam and sand - Based on the relationship curve of aggregate provision speed and conveyor speed, conveying speed for macadam and sand shall be calculated to achieve the ratio of macadam and sand under mix results in Step of the preliminary design stage (Figure 1) - Bring the entire batch plant into operation with conveyor speed for macadam and sand (similar to case of mass production, but not including the mix of aggregate with asphalt and mineral powder) - When the batching plant in state of steady operation, aggregate sample from reserve hot bins (aggregate from each hot bin is regarded as one type of aggregate), mineral powder sample is taken to analyze grain composition Mixing ratio of aggregates shall be calculated as Step of the preliminary design Conveyor speed shall be adjusted so that the grading curves will be similar to that of Step of the preliminary design 7.2.5 Meaning of Hot bin mix design: - Prove the capability of producing asphalt concrete mixture at batching plant; - The produced asphalt concrete mixture complies with technical requirements for the construction work; - Bases for trial production and trial construction 7.2.6 If laboratory test data indicates that the asphalt concrete mixture satisfies technical requirements set forth, trial production of asphalt concrete mixture at batching plant and trial construction at site will be carried out 7.3 Job-mix formula verification (Stage 3) 7.3.1 This stage includes five steps as follows (Figure 1): - Step 1: Trial production - Based on results from of hot bin mix design, produce from 60 to 100 tons of asphalt concrete mixture at batching plant - Step 2: Trial construction – Take asphalt concrete mixture from trial production to perform trial construction on a section of 200 - 300 m - Step 3: Inspection on the trial mixed asphalt concrete (laboratory test for asphalt concrete produced at batching plant) - Step 4: Inspection on the asphalt concrete mixture after trial construction at site - Step 5: Approval for the production formula of asphalt concrete 7.3.2 If test results at laboratory and site indicate that the trial produced asphalt concrete mixture complies with technical requirements regulated in Specification for Construction of Asphalt Concrete Pavement and Acceptance and is highly practical which can be constructed by available equipment, ensuring requirements of density, roughness and geometrical dimensions, etc., the Contractor could submit the production formula to the Consultant and the Employer for approval Production formula of asphalt concrete includes the following contents: - Aggregate and asphalt sources for asphalt concrete mixture; - Results of experiments on physical-mechanical properties of asphalt, macadam aggregate, sand, mineral powder comply with regulation in Specification for Construction of Asphalt Concrete Pavement and Acceptance; - Grading composition of aggregate mixture; - Ratio of aggregates: macadam, sand, mineral filler at cold bin and hot bin; - Design results of asphalt concrete mixture and optimum asphalt content; - The specified temperature values at: mixing, discharging the mixture from the mixer, transporting to the site, spreading, rolling; - The construction plan at site such as: the thickness of the unrolled asphalt concrete layer, rolling diagram, rolling number per point, the surface roughness, etc 7.3.3 The approved production formula is the basis for all proceeding works: Production, construction, acceptance and final settlement between the Contractor and the Employers 7.4 Control routine construction (Stage 4) Control routine construction includes two steps as follows (Figure 1): - Step 1: Quality control during production, the quality control at this step is similar to Step of Jobmix formula verification - Step 2: Quality control after construction - similar to Step of Job-mix formula verification; 7.4.1 Quality control during production 7.4.1.1 The purpose of this step is to control the quality stability of the asphalt concrete, ensuring that the tolerance of aggregate gradation and the asphalt content in comparison to production formula of asphalt concrete is within the specified limits regulated in Specification for Construction of Asphalt Concrete Pavement and Acceptance 7.4.1.2 This work is carried out under a defined plan with a certain sampling frequency Samples of hot aggregate and asphalt concrete mixture are taken from batching plant The purpose of this work is to check the asphalt concrete produced daily then compare with the approved production formula to detect abnormal changes and have proper adjustments 7.4.1.3 When excessive changes are detected (quality of input materials, major variations in material quality, etc.), beyond the control capability of the batching plant, it should redesign the asphalt concrete mixture and reconstruct the production formula of asphalt concrete 7.4.1.4 Frequency of sampling for inspection and inspection criteria for this stage is regulated in Specification for Construction of Asphalt Concrete Pavement and Acceptance 7.4.2 Quality control after construction 7.4.2.1 This work includes many different items, in which sample drilling to determine the density is directly related to the design of asphalt concrete mixture 7.4.2.2 This work is the basis for the acceptance and takeover of the construction work 7.4.2.3 Inspection criteria and inspection frequency in this stage is regulated in Specification for Construction of Asphalt Concrete Pavement and Acceptance Procedure of asphalt concrete mix design using Marshall method Procedure of asphalt concrete mix design using Marshall method includes steps as follows 8.1 Experiment to determine physical-mechanical properties of aggregate and asphalt Carry out experiment to determine physical-mechanical properties of macadam, sand, mineral powder and asphalt Compare with the requirements in Specification for Construction of Asphalt Concrete Pavement and Acceptance to evaluate the quality If any material is not qualified enough, it should take alternative measure 8.2 Aggregate mixing 8.2.1 The purpose of aggregate mixing is to find the proportion of existing aggregates (macadam, sand, mineral powder), so that the aggregate mixture after mixing will have grain composition within the boundary limit of grain envelope regulated in Specification for Construction of Asphalt Concrete Pavement and Acceptance 8.2.2 Types of aggregates: macadam, sand, and mineral powder are produced separately For macadam, two or three groups of grain size should be used for the design, depending on the maximum nominal particle size of the asphalt concrete mixture Therefore, it is necessary to carry out the aggregate mixing to find the suitable aggregate mixture 8.2.3 Carry out analysis of particle size of aggregate groups: macadam, sand, and mineral powder with sieve sizes regulated in Specification for Construction of Asphalt Concrete Pavement and Acceptance 8.2.4 Calculate to find the mixing ratio of aggregate groups (by percentage in total aggregate mass), providing that the gradation of the designed aggregate mixture is within the boundary limit of grain envelope regulated in Specification for Construction of Asphalt Concrete Pavement and Acceptance The aggregate gradation curve of the designed aggregate mixture must be even, in which the lower limit of one sieve size shall not change into the upper limit of the next sieve size or vice versa 8.2.5 Principle of mixing computation is detailed in Appendix A Mixing computation can be conducted by applying a mathematical formula, using a Microsoft Excel spreadsheet or a specialized software (see Appendix A) 8.3 Prepare sample of aggregate mixture for casting Marshall sample 8.3.1 Number of aggregate sample required: - To cast Marshall sample, determine bulk specific gravity of asphalt concrete, and implement Marshall experiment: 15 samples (5 sample groups, samples per group); - To determine maximum weight of asphalt concrete mixture: samples in case of applying he first way (see 8.5.5.1) or samples in case of apply the second way (see 8.5.5.2) - To check physical-mechanical properties of the asphalt concrete sample after having the optimum asphalt content: samples - To determine the remaining Marshall stability of the asphalt concrete sample after having the optimum asphalt content: samples - To check the additional parameters of asphalt concrete after having the optimum asphalt content: the number of sample will follow Specification for Construction of Asphalt Concrete Pavement and Acceptance 8.3.2 Preparation of aggregates: Based on the number of samples required, prepare sufficient aggregate volume, dry, and sieve to separate granular sizes, then mix the granular sizes to form separate aggregate mixture samples: - In case of experiment by conventional Marshall method: the amount of aggregate mixture per sample is about 1,200 g; - In case of experiment by improved Marshall method: the amount of aggregate mixture per sample is about 4,000 g 8.4 Mix aggregate with asphalt, compact Marshall sample 8.4.1 Predict the optimum asphalt content 8.4.1.1 For the design of asphalt concrete mixture, 05 sample groups of asphalt concrete shall be made, in which 05 asphalt content values of each are 0.5% different from each other respectively The selected value of asphalt content among asphalt content values is necessary, so that it can calculate the remaining asphalt content values The selected value of asphalt content should satisfy the condition that the determined optimum asphalt content is within the middle range of the values of the asphalt content of the asphalt concrete specimen The selected asphalt content is called the predicted optimum asphalt content 8.4.1.2 In case the reference asphalt content is given in Specification for Construction of Asphalt Concrete Pavement and Acceptance, the predicted optimum asphalt content will be selected within the range of such reference asphalt content 8.4.1.3 In case the reference asphalt content is not given in Specification for Construction of Asphalt Concrete Pavement and Acceptance, it is necessary to determine the predicted optimum asphalt content The predicted optimum asphalt content can be determined by the following formula: P = 0.035a + 0.045b + Kc + F Whereas: - P is the predicted optimum asphalt content (percentage in total mass of asphalt concrete); - a is the percentage of aggregate on the sieve 2.36mm, in the form of an integer (e.g 22.3% is 22); - b is the percent of aggregate material that can pass sieve 2.36mm and cannot pass sieve 0.075mm; this figure is used in the formula in the form of integer; - c is the percent of aggregate material that can pass sieve 0.075mm; this figure is used in the formula in the form of decimal number (for example, 6.25% is written as 6.25); - K is 0,15 if the percent of material passing sieve 0.075m is from 11 to 15%; K is 0,18 if the percent of material passing sieve 0.075m is from to 10%; K is 0,20 if the percent of material passing sieve 0.075m is from to 5%; - F is from 0.2 to 0.6 depending on coarse aggregate’s asphalt absorption If the aggregate material has low asphalt absorption (or low water absorption), choose low value and vice versa 8.4.2 Mix aggregate material with bitumen 8.4.2.1 Determine required number of asphalt concrete samples (according to 8.3) before preparation of bitumen samples and trial mix of asphalt concrete, including: - Prepare Marshall sample, identify bulk density of Asphalt concrete and Marshall test: Mix groups of aggregate samples (each group include samples) with different bitumen contents (difference of 0.5% around the estimated optimal bitumen content) - Identify the highest bulk density of Asphalt concrete: Mix samples of aggregate material with different bitumen contents if the first method was chosen (accordance with 8.5.5.1) or samples with optimal bitumen content if the second method was chosen (accordance with 8.5.5.2) - Check the mechanical and physical properties of asphalt concrete sample with reference to relative optimal bitumen content: Mix samples of aggregate material with known optimal bitumen content (on the basis of design of asphalt concrete mix) - Identify remaining Marshall stability of asphalt concrete sample with reference to optimal bitumen content: Mix samples of aggregate material with know optimal bitumen content - Check additional asphalt concrete properties with reference to optimal bitumen content: number of asphalt concrete samples in conformity with regulations of standards of asphalt concrete construction and acceptance, 8.4.2.2 Mixing procedure of aggregate material with bitumen is as below: - Weigh to identify the weight of bitumen samples with reference to chosen bitumen content (content is calculated with consideration of weight percent in asphalt concrete mixture) - Put bitumen sample into dryer and increase the temperature to mixing temperature as regulated in standards of asphalt concrete construction and acceptance, - Put aggregate sample into another dryer and heat it to a temperature which is 15 oC higher than mixing temperature - Mix aggregate material with bitumen 8.4.3 Compact Marshall sample 8.4.3.1 Equipment for compacting Marshall sample, testing tools and compaction procedure are regulated by TCVN 8860-1:2011 8.4.3.2 sample groups of asphalt concrete mixture (each group of samples) are put into moulds for compaction one by one Height of asphalt concrete samples after compaction in moulds must be in regulated range (63,5 mm ±1,3 mm with normal Marshall compaction of and 95,2 mm ± 1,8 mm with modified Marshall compaction) Normally, aggregate mixtures with the weight of about 1200 g (with normal Marshall compaction method) or about 4000 g (with modified Marshall compaction method) shall result in compacted samples with proper height 8.4.3.3 In case that the height of compacted sample is not within regulated range, adjust the amount of required aggregate material for sample compaction as below: In which: - A is 63, mm when normal Marshall compaction method is applied - A is 95, mm when modified Marshall compaction method is applied 8.4.3.4 Compaction temperature for Marshall sample is regulated by standards of asphalt concrete construction and acceptance, depending on type of bitumen used 8.5 Tests and calculation of volume properties of asphalt concrete mixture Tests and calculation of indexes required for volume properties for Asphalt concrete design shall follow below procedure: 1) Test to determine bitumen density in accordance with TCVN 7501:2005 It is possible to determine beforehand (refer to Article 8.1) 2) Test to determine coarse aggregate material density (in accordance with AASHTO T 85-2000; fine aggregate material density (in accordance with AASHTO T 84-2000; mineral powder density (in accordance with TCVN 4195:1995, test at 250C, which equivalent to water density of g/cm3) It is possible to determine beforehand by following instructions in Article 8.1 3) Calculate bulk density, apparent density of aggregate mixture 4) Calculate effective density of aggregate mixture 5) Test to determine the maximum density of asphalt concrete mixture before compaction 6) Test to determine the bulk density and volumetric mass of compacted asphalt concrete sample 7) Calculate absorbed asphalt content 8) Calculate effective asphalt content 9) Calculate Voids in mineral aggregate of compacted asphalt concrete mixture 10) Calculate residual voids in compacted asphalt concrete mixture 11) Calculate voids filled with Asphalt in compacted asphalt concrete mixture 8.5.1 Test to determine asphalt density Asphalt density is denoted as Gb 8.5.2 Test to determine aggregate density - Plasticity (deformation): plasticity increases as bitumen content increases - Residual voids: residual voids decrease as bitumen content increases - Voids in mineral aggregate (VMA): at first, VMA decreases as bitumen content increases After reaching a certain minimum value, VMA increases as bitumen content increases - Voids filled with Asphalt (VFA): VFA increases as bitumen content increases - Volumetric mass of asphalt concrete: similar to rule of Marshall stability However, bitumen content in relation to maximum volumetric mass of asphalt concrete will be slightly higher than bitumen content in relation to maximum stability General requirements for Site Laboratory Site Lab is formed to carry out required tests to design asphalt concrete mixture, to monitor quality and propose proper adjustment timely for smooth operation of batching plants to ensure the conformity of asphalt concrete produced Below are basic requirements for site lab that comes with asphalt concrete batching plant 9.1 Requirements on infrastructure of site lab Site lab must satisfy some requirements listed below: - Site lab must be located next to batching plant, with minimum area of 15m2 and sufficient supply of electricity, water and good ventilation system - Tables must be stable for installation and use of testing equipment - There must be at lease windows, one of which must have direct vision of batching plant for people to be able to observe the batching plant while it is operating 9.2 Requirements on testing equipment Main equipment of Site Lab that comes with asphalt concrete batching plant includes: - Marshall compressor and molds - Marshall sample compressor - Centrifuge to determine bitumen content - Vacuum equipment and sample container to determine uncompacted density - Equipment to determine density of coarse aggregate material, including weight basket and other equipment - Equipment to determine density of fine aggregate material, including mold, tamper rod and other equipment - Steel Sieve with different sizes as stipulated in Standards of Construction and Acceptance of asphalt concrete pavement - Equipment to determine liquid limit and plasticity limit - Equipment to determine equivalent sand criteria ES - In-situ sample driller - Other equipment: balances of different types, oven dryer, thermometer; equipment to take samples, divide samples, sample tray, mixing pan, brush, - Other equipment and tools if necessary as stipulated in Standards of Construction and Acceptance of asphalt concrete pavement 9.3 Requirements on Human resources Lab must have sufficient capable personnel to carry out tests precisely and timely for product manufacture Lab staff that is assigned to carry out tests related to design of asphalt concrete mixture must have proper education certificate and knowledge in construction materials and asphalt concrete 9.4 Requirements on quality control system Lab must have a management system to monitor all activities Lab must monitor the following matters: - Document management, including standards on asphalt concrete - Review of technical requirements on asphalt concrete; - Management of test equipment; - Adjust asphalt concrete produced at batching plant when there is any spotted change in produced asphalt concrete; - Education and training for laboratory staff Appendix A (For reference) Guideline for mixing design A.1 General principles A.1.1 In AC mix design work, the first work is to mix aggregates (crushed stone, sand, stone powder) to choose mixture with grading satisfying technical requirements A.1.2 Mixing aggregates is conducted following this principle: for any mixture, percentage (%) of sieve passing of mixed aggregates through any sieve size must follow this formula: P = Aa + Bb + Cc + Dd + (B1) Where: - P is the percentage (%) of sieve passing of any sieve size of the mixture aggregates; - A, B, C,D, refers to the percentage (%) of sieve passing of any sieve size of each aggregate to be mixed; - a, b, c,d, is the mixing proportion of each aggregate used for mixing a+b+c+d+ = (100%) (B2) A.1.3 Based on formula B1 and B2, provided grading of each aggregate (sieve passing percentage of any sieve size A, B, C, D….) is known, to select mixing proportion of each aggregate (a, b, c, d…) reasonably so that aggregates mixture has grading in limit domain of grading curve for the aggregate mixture as stated in the specifications for construction and acceptance A.1.4 Based on this principle, we calculate proportion For convenience in proportion calculation, set up a software for calculation or using Microsoft Excel A.2 Some examples for mixing design A.2.1 Mixing two aggregates Formula applied for mixing aggregates is P = Aa + Bb (B3) As a + b = (or 100%) so a = – b Replace a = – b into B3 we have: Or Given that there are aggregates, symbolized as I (code for Aggregate I) and II (code for Aggregate II) Grading/particle composition (percentage of sieve passing) of aggregates, grading requirement (required percentage of sieve passing), required average percentage of passing of the aggregates mixture in Table B1 Table B1 Size (mm) 19 12.5 Required percentage of passing (%) 9.5 4.75 2.36 0.6 0.3 0.15 0.075 -Upper limit 100 100 90 70 50 29 23 16 10 -Lower limit 100 80 70 50 35 18 13 -Average 100 90 80 60 42.5 23.5 18 12 Aggregate I 100 90 59 16 3.2 1.1 0 Aggregate II 100 100 100 96 82 51 36 21 9.2 To select percentage of passing sieve 2.36 as standard Average point of required percentage of passing sieve 2.36mm is 42.5 Calculate value of a and b by formula B4: From data in Table B1, a and b are known, calculate passing percentage of aggregates (Aa and Bb) and aggregates mixture (P=Aa+Bb) on sieve sizes Results are stated in Table B2 Table B2 Sieve size (mm) proporti on 19 12.5 9.5 4.75 2.36 0.6 0.3 0.15 0.075 Required percentage of passing (%) -Upper limit 100 100 90 70 50 29 23 16 10 -Lower limit 100 80 70 50 35 18 13 -Average 100 90 80 60 42.5 23.5 18 12 CL I 0.5 50 45 29.5 1.6 0.6 0 CL II 0.5 50 50 50 48 41 25 18 10.5 4.6 Aggregates mixture ∑=1 100 95 79.5 56 42.6 25.6 18 10.5 4.6 By table B.2, it is found that percentage of passing sieve 0.075mm of the aggregates mixture (4.6%) is low, so, it is possible to raise proportion of Aggregate II above, specifically b=0.55 and then proportion of aggregate I is a = 0.45 Result of calculating percentage of passing sieve of aggregates and mixture are stated in table B3 Considering that percentage of passing sieve 0.6mm is too high (28.5%), proximate to upper limit of required percentage of passing), so proportion of Aggregate II should be lowered to b=0.52, then percentage of Aggregate I is a=0.48 Calculation result for percentage of sieve passing of aggregates and mixture are stated in Table B4 Table B3 Sieve size (mm) Proporti on 19 12.5 9.5 4.75 2.36 0.6 0.3 0.15 0.075 Required percentage of passing (%) -Upper limit 100 100 90 70 50 29 23 16 10 -Lower limit 100 80 70 50 35 18 13 -Average 100 90 80 60 42.5 23.5 18 12 Aggregate I 0.45 45 40.5 26.6 7.2 1.4 0.5 0 Aggregate II 0.55 55 55 55 52.8 45.1 28 19.8 11.5 5.1 Aggregates mixture ∑=1 100 95.5 81.6 60 46.5 28.5 19.8 11.5 5.1 Table B4 Sieve size (mm) Proporti on 19 12,5 9,5 4,75 2,36 0,6 0,3 0,15 0,075 Required percentage of passing (%) -Upper limit 100 100 90 70 50 29 23 16 10 -Lower limit 100 80 70 50 35 18 13 -Average 100 90 80 60 42,5 23,5 18 12 Aggregate I 0,48 48 43,2 28,3 7,7 1,5 0,5 0 Aggregate II 0,52 52 52 52 49,9 42,6 26,5 18,7 10,9 4,8 Aggregates mixture ∑=1 100 95,2 80,3 57,6 44,1 27 18,7 10,9 4,8 Aggregates mixture in Table B4 satisfy requirements (within limits of required percentage of passing) Mixing result: Aggregate I: 48% Aggregate II: 52% A.2.2 Mixing aggregates (using function “Solver“of Microsoft Excel) Basic formula when mixing aggregates is: P = Aa + Bb + Cc + Dd + Ee (B5) 1=a+b+c+d+e (B6) Assuming there are aggregates, with known grading (percentage of sieve passing) of each aggregate: - Coarse aggregate (crushed stone), Dmax 25 mm, symbolized as D25; - Coarse aggregate (crushed stone), Dmax 9.5 mm, symbolized as D10; - Fine aggregate (crushed sand), Dmax 4.75 mm, symbolized as D5; - Natural sand, Dmax 4.75 mm; symbolized as NS; - Mineral filler as MF We need to calculate mixing proportion of above aggregates (a, b, c, d, e) to make an aggregates mixture satisfying requirements (in this example, aggregates of the mix design must meet requirements in TCVN 8819:2011, Table 1, with dense-graded HMA 19) In which, a refers to proportion of crushed stone D25; b is the proportion of crushed stone D10; c is proportion of crushed sand D5; d is proportion of NS and e refers to proportion of MF This is how to do: 1/ Enter data in the Microsoft Excel worksheet (Table B5): - Enter values of limits of required percentage of passing corresponding with sieve sizes: Upper limit (row 3), Lower limit (row 4), average (row 5) - Enter values of sieve passing percentage for each in aggregates: D25 (row 6), D10 (row 7), D5 (row 8), NS (row 9) and MF (row 10) Table B5 A B C D E F G H I J K L Sieve size Mix 25 19 12.5 9.5 4.75 2.36 1.18 0.6 0.3 0.075 (mm) proporti on Required percentage of passing (%) Upper limit 100 100 86 78 61 45 33 25 17 Lower limit 100 90 71 58 36 25 17 12 5 Average 100 95 78.5 68 48.5 35 25 18.5 12.5 6.5 D25 100 86.3 30.6 7.4 2.1 0.3 0.3 0.2 0 D10 100 100 100 90.9 46.2 15.2 0.9 0.7 0.2 D5 100 100 100 100 90.5 70.1 45.5 18.9 12.5 7.4 NS 100 100 100 98.8 95 89.3 78.1 45.6 8.7 0.9 10 MF 100 100 100 100 100 100 100 100 96.4 76.1 11 Results for running program for the first time 12 D25 0.33 33.0 28.5 10.1 2.4 0.7 0.1 0.1 0.1 0.0 0.0 13 D10 0.20 20.4 20.4 20.4 18.6 9.4 3.1 0.2 0.1 0.0 0.0 14 D5 0.34 34.0 34.0 34.0 34.0 30.8 23.9 15.5 6.4 4.3 2.5 15 NS 0.09 9.4 9.4 9.4 9.3 8.9 8.4 7.3 4.3 0.8 0.1 16 MF 0.03 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.0 2.4 17 Mixture 1.00 100.0 95.5 77.1 67.5 53.0 38.6 26.3 14.1 8.1 5.0 2/ Establishing relationship with formula B5 (P = Aa + Bb + Cc + Dd + Ee) (Table B5): - To assign value a, b,c,d and e (any values) into cells from B12 to B16 - Determine value Aa corresponding with sieve sizes: displayed form cell C12 to L12 These values are product of value in cell B12 and values of cells ranging from C6 to L6 (by Excel language, it is: C12=$B12*C6, D12=$B12*D6, , L12=$B12*L6) - Determine value Bb, Cc, Dd, Ee corresponding with sieve sizes: following the way for Aa, they are displaced from row 13 to row 16, from column C to column L - Establish relationship P (P = Aa + Bb + Cc + Dd + Ee) corresponding with sieve sizes: displayed from cell C17 to cell L17 These values is the sum of corresponding values from row 12 to row 16, column C to column L For example, C17= C12+C13+C14+C15+C16 (by Excel language, it is C17= SUM(C12:C16)) 3/ To establish relationship with formula B6 (1=a+b+c+d+e) (Table B5): - Value in cell B17 is the sum of values from cell B12 to cell B16 (by Excel language, it is B17= SUM(B12:B16)) - Assigning value of to cell B17 (1=a+b+c+d+e) is made by function Solver 4/ To make statements in function “Solver“: - In Microsoft Excel, select menu Tool – Add in – mark and set up function Solver After installation, in the menu Tool, Solver appear - Click in Solver in menu Tool, window “Solver Parameter“ appear for making statements, and then insert the following statements (Figure B1): Figure B1 - In the Command “Set Target Cell“: enter address of B17 (by Excel language, it is $B$17) - In the Command “Equal To“: select “Value of“and enter value (value of equation B6) - In the Command “By Changing Cells“: enter addresses from B12 to B16 (by Excel language, it is $B$1:$B$16) - In the Command “Subject to the constraints“: select “Add“, item “Add Constraint“ is displayed to enter constrains for the problem (Figure B2) Figure B2 + To ensure conditions that values in cells from B12 to B16 (displaying values a, b, c, d e) không will not be negative values (-), enter the row a command $B$12:$B$16 into “Cell Reference“, select expression >=, enter number into the window “Constraint“ and click “OK“ The entered command will be displayed in Figure B1 ($B$12:$B$16>=0) + To ensure conditions that values of cells from C17 to L17 (passing percentage of Sieve sizes of the aggregates mixture) must be within limits of required percentage of passing (less than Upper limit value and larger than Lower limit value of required percentage of passing curve), enter into the window “Cell Reference“ as instructed above The entered command will be displayed in Figure B1 ($C$17>=$C$3, $C$17