ASTM D995-95b(2002)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation: D 995 – 95b (Reapproved 2002)
Standard Specification for
Mixing Plants for Hot-Mixed, Hot-Laid Bituminous Paving
Mixtures
This standard is issued under the fixed designation D 995; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
1. Scope 4. Requirements for All Plants
1.1 This specification covers requirements for plants suit- 4.1 Uniformity—The plant shall be capable of uniformly
able for producing hot-mixed, hot-laid bituminous paving combining and mixing various sizes of aggregate from stock-
mixtures. piles, reclaimed asphalt pavement, if required, and bituminous
1.2 The values stated in inch-pound units are to be regarded material.
as the standard. 4.2 Equipment for Preparation of Bituminous Material:
4.2.1 Tanks for storage of bituminous material shall be
2. Referenced Documents
equipped for heating the material, under effective and positive
2.1 ASTM Standards:
control at all times, to the temperature required in the paving
C 136 Test Method for Sieve Analysis of Fine and Coarse mixture specifications. Heating shall be by steam or oil coils,
Aggregates
electricity, or other means such that no flame shall contact the
D 8 Terminology Relating to Materials for Roads and Pave- heating tank.
ments
4.2.2 The circulating system for the bituminous material
D 140 Practice for Sampling Bituminous Materials shall be of adequate capacity to provide proper and continuous
circulation between storage tank and proportioning units dur-
3. Terminology
ing the entire operating period.
3.1 For definitions of terms see Terminology D 8.
4.2.2.1 The discharge end of the bituminous material circu-
3.2 Definitions of Terms Specific to This Standard:
lating pipe shall be kept below the surface of the bituminous
3.2.1 batch plant, n—a manufacturing facility for producing
material in the storage tank to prevent discharging the hot
bituminous paving mixtures that proportions the aggregate and
bituminous material into the open air.
bituminous constituents into the mix by weighed batches, adds
4.2.2.2 All pipe lines and fittings shall be steam or oil-
bituminous material by either weight or volume, and mixes the
jacketed or otherwise properly insulated to prevent heat loss.
blend.
When the bituminous material is emulsified asphalt, provisions
3.2.2 continuous mix plant, n—a manufacturing facility for
should be made in the bitumen transfer system that will enable
producing bituminous paving mixtures that continuously pro-
the operator to turn off or reduce the heat media from all lines,
portionstheaggregateandbituminousconstituentsintothemix
pumps, and jacketed bituminous material buckets as soon as
by a continuous volumetric proportioning system without
the system is open and circulating properly.
definite batch intervals.
4.2.3 Storage tank capacity shall be such as to ensure
3.2.3 drum mix plant, n—a manufacturing facility for pro-
continuous operation of the plant and uniform temperature of
ducing bituminous paving mixtures that continuously propor-
the bituminous material when it is introduced into the aggre-
tions aggregates, heats and dries them in a rotating drum, and
gate. Tanks shall be calibrated accurately to 100-gal (378.5-L)
simultaneously mixes them with a controlled amount of
intervals and shall be accessible for measuring the volume of
bituminous material. The same plant may produce cold-mixed
bituminous material at any time.
bituminous paving mixtures without heating and drying the
4.2.4 A sampling tap, complying with the requirements of
aggregates.
Practice D 140, shall be provided in the bituminous material
feed lines connecting the storage tanks to the bituminous
control unit.
This specification is under the jurisdiction of ASTM Committee D04 on Road
4.2.5 When filled or native bituminous materials are used,
and Paving Materials and is the direct responsibility of Subcommittee D04.23 on
Plant-Mixed Bituminous Surfaces and Bases.
means shall be provided for agitation to maintain a uniform
Current edition approved Sept. 10, 1995. Published November 1995. Originally
product.
published as D 995 – 48 T. Last previous edition D 995 – 95a.
Annual Book of ASTM Standards, Vol 04.02.
Annual Book of ASTM Standards, Vol 04.03.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 995 – 95b (2002)
4.3 Mineral Filler—Adequate dry storage shall be provided 4.10.3 Ample unobstructed space shall be provided on the
for mineral filler, when required, and provision shall be made mixing platform if applicable.
for accurate proportioning. 4.10.4 An unobstructed passage shall be maintained at all
times in and around the truck-loading space. This space shall
4.4 Cold Aggregate Feeder—The plant shall be provided
be kept free of drippings from the mixing platform.Aladder or
with mechanical means for uniformly feeding the aggregates
platform shall be located at the truck-loading space to permit
into the dryer so that uniform production and temperature may
easy and safe inspection of the mixture as it is delivered into
be assured. When aggregates must be blended from two or
the trucks. Overhead protection shall be provided where
more bins at the cold feed to meet the requirements of the
necessary.
paving mixture specifications, a synchronized proportioning
method shall be provided.
5. Significance and Use
4.4.1 If recycling capability is required, the plant shall be
equipped with mechanical means for feeding the desired
5.1 This specification describes the various components of
weight of reclaimed asphalt pavement into the mix. Facilities batch, continuous mix, and drum mix plants. This standard is
shall be provided for obtaining samples of the reclaimed
useful to help evaluate existing plants and for specifying new
asphalt pavement. plants to ensure the plant is capable of producing a quality
4.5 Dryer—Adryer of satisfactory design capable of drying product. This standard does not address plant operation and
control or mixture production.
and heating the aggregate to the moisture and temperature
requirements of the paving mixture specifications shall be
6. Requirements for Plants Controlling Gradation of
provided.
Hot, Dry Aggregates
4.6 Bituminous Control Unit:
4.6.1 Satisfactory means, either by weighing or metering, 6.1 Plant Screens:
shall be provided to obtain the proper amount of bituminous 6.1.1 Plants shall be equipped with plant screens located
material. Accuracy of the metering devices shall be within 1.0 between the dryer and hot aggregate bins and shall have
% of the actual weight being measured when that weight has adequate capacity and size range to separate the heated
been determined using another measuring device and shall be aggregate into the sizes required for proportioning so that they
within 0.5 % when that weight has been determined using test may be recombined consistently within the specification limits.
weights. Bituminous material scales shall conform to 8.5. 6.1.2 The nominal maximum size aggregate in the fines bin
shall be specified.The screen type and size shall be determined
4.6.2 Suitable means shall be provided, either by steam or
bytheoperator.Noaggregateshallbelargerthanthemaximum
oil jacketing, or other insulation, for maintaining the specified
specified.
temperature of the bituminous material in the pipe lines,
6.1.3 Control shall be based on frequent bin samples tested
meters, weigh buckets, spray bars, and other containers or flow
in accordance with Test Method C 136.Aggregate in each bin,
lines.
including mineral filler, shall be combined in proper propor-
4.7 Thermometric Equipment:
tions, and the composite shall be checked for compliance with
4.7.1 An armored recording thermometer of suitable range
the paving mixture specifications.
shall be fixed in the bituminous material feed line at a suitable
6.2 Hot Aggregate Bins:
location near the discharge at the mixer unit.
6.2.1 Hot-bin storage of sufficient capacity to ensure uni-
4.7.2 Approved recording thermometers, pyrometers, or
form and continuous operation shall be provided. Bins shall be
other recording thermometric instruments shall be fixed at the
divided into the specified number of compartments arranged to
discharge chute of the dryer and, when applicable, in the hot
ensure separate and adequate storage of appropriate fractions
finesbintoregisterandrecordautomaticallythetemperatureof
of the aggregate.
the heated aggregate or heated mixture.
6.2.2 Each compartment shall be provided with an overflow
4.8 Emission Controls:
chuteofsuchsizeandatsuchalocationtopreventanybacking
4.8.1 A dust collecting system shall be provided. The
up of material into other compartments or into contact with the
system shall be made to waste the material so collected, or to
screen.
return all or any part uniformly to the mixture.
6.2.3 Bins shall be equipped with “tell-tale” devices to
4.8.2 Other emissions, such as smoke but excepting water
indicate the position of the aggregate in the bins at the lower
vapor, shall be controlled to be in compliance with applicable
quarter points.An automatic plant shut-off shall be provided to
limits.
operate when any aggregate bin becomes empty.
4.9 Surge and Storage Bins—If bins are used for surge or
6.2.4 Adequate and convenient facilities shall be provided
storage, they shall be such that mixture drawn from the bin
for obtaining aggregate samples from each bin.
meets the requirements of the paving mixture specification.
4.10 Safety Requirements: 7. Requirements for Plants Controlling Gradation of
Cold, Damp Aggregates
4.10.1 Adequate and safe stairways to the mixer platform
shall be provided if applicable. Guarded ladders to other plant
7.1 Maximum Aggregate Size—Oversize aggregate shall be
units shall be located where required.
rejected by suitable methods or devices before the aggregate
4.10.2 All gears, pulleys, chains, sprockets, and other dan- enters the cold feed, or by plant screens complying with 6.1.
gerous moving parts shall be thoroughly protected. 7.2 Cold Feed Bins:
D 995 – 95b (2002)
7.2.1 Cold feed bins for storing aggregates prior to propor- weights shall be kept clean and conveniently located for
tioningshallbeequippedwith“tell-tale”devicestoindicatethe calibration of the scale.
position of the aggregate in the bins at the lower quarter points.
8.4 Bituminous Material Bucket:
An automatic plant shut-off shall be provided to operate when
8.4.1 If a bucket is used, it shall be large enough to handle
anyaggregatebinbecomesemptyortheflowfromanybingate
a batch in a single weighing.
becomes restricted.
8.4.2 The filling system and bucket shall be of such design,
7.2.2 Adequate and convenient facilities shall be provided
size, and shape that the bituminous material will not overflow,
for obtaining samples of the full flow of aggregate from each
splash, or spill outside the bucket during filling and weighing.
cold feed bin and from the total cold feed.
8.4.3 The time required to add the bituminous material shall
7.2.3 Adequate and convenient facilities shall be provided
not exceed 20 s. Where the quantity of bituminous material is
for diverting aggregate flow into trucks or other suitable
metered, provision shall be made to check the delivery of the
containers to check the accuracy of the aggregate delivery
meter by actual weight.
system.
8.4.4 The bucket shall be steam or oil-jacketed or equipped
7.2.4 Control shall be based on frequent samples from each
with properly insulated electric heating units. It shall be
cold-feed bin and the total cold feed tested by Test Method
arranged to deliver the bituminous material in a thin uniform
C 136. Results of total cold-feed samples shall be checked for
sheet or in multiple sprays over the full length of the mixer.
compliance with the paving mixture specifications.
8.5 Bituminous Material Scales—Scales for the weighing of
8. Requirements for Batch Plants
bituminous material shall meet the requirements for aggregate
scales,asspecifiedin8.3exceptadevicetoindicateatleastthe
8.1 Control of Aggregate Gradation—The plant shall be
last 20 lb (9.1 kg) of the approaching total load shall be
equipped to control aggregate gradation in accordance with the
provided. Beam-type scales shall be equipped with a tare beam
requirements of either Section 6 or Section 7.
or adequate counterbalance for balancing the bucket and
8.2 Weigh Box or Hopper:
compensating periodically for the accumulation of bituminous
8.2.1 Means shall be provided for weighing aggregate from
material on the bucket.
each bin into a weigh box or hopper, suspended on scales, and
8.6 Mixer Unit for Batch Method:
ample in size to hold a full batch.
8.2.2 The weigh box or hopper shall be supported on 8.6.1 The plant shall include a batch mixer of an approved
fulcrums and knife edges that will not easily be thrown out of twin-shaft pugmill type capable of producing a uniform mix-
alignment or adjustment. ture.
8.2.3 Gates, both on the bins and the hopper, shall not leak.
8.6.1.1 The mixer shall be designed to provide means of
8.3 Aggregate scales:
adjusting the clearance between the mixer blades and liner
8.3.1 Scales for any weigh box or hopper may be either
plates to ensure proper and efficient mixing.
beam or springless-dial type and shall be of standard make and
8.6.1.2 Ifnotenclosed,themixerboxshallbeequippedwith
design.Theaccuracyoftheweighingdeviceshallbewithin1.0
a dust hood to prevent loss of dust by dispersion.
% of the actual weight being measured when that weight has
8.6.1.3 The mixer shall be constructed to prevent leakage of
been determined using another measuring device and shall be
the contents.
within 0.5 % when that weight has been determined using test
8.6.1.4 Mixer discharge shall not cause appreciable segre-
weights.
gation.
8.3.2 The change in load required to alter noticeably the
8.6.2 The mixer shall be equipped with a positive means for
position of rest of the indicating element (or elements) of a
governing mixing time and an accurate time lock to control the
nonautomaticindicatingscaleshallnotbegreaterthan0.1 %of
operationofacompletemixingcyclebylockingtheweigh-box
the nominal scale capacity.
gate after the charging of the mixer until the closing of the
8.3.3 Beam type scales shall be equipped with a device to
mixer gates at the completion of the cycle; it shall lock the
indicate that the required load is being approached.This device
bituminous ma
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