CATEGORY 500 PAVING SECTION 502 — CEMENT TREATED BASE COURSE AND CEMENT MODIFIED SUBGRADE
502.01 Description
Construct Cement Treated Base (CTB) course or Cement Modified Subgrade (CMS) using a combination of soil or graded aggregate base and Portland cement, uniformly mixed, moistened, compacted, shaped and sealed to the required depth and widths specified. Mix the CTB or CMS in place.
502.02 Materials
Graded Aggregate Base 901.01 Portland Cement 902.03 Emulsified Asphalts 904.03 Select or Capping Borrow for CTB 916.01 Soil for CMS 916.01 Water 921.01
502.03 Construction
Submit the equipment and material sources for approval at least 30 days prior to the start of construction of the CTB or CMS. For mix design approval time frame, refer to 502.03.04. Protect the subgrade and/or base against damage from all causes.
502.03.01 Equipment.
Reclaimer. A self-propelled rotary machine capable of cutting through material to depths equal to or greater than the planned lift thickness as specified in Contract Documents. The reclaimer shall be capable of pulverizing the material at a minimum width of 8 ft and mix water, dry additives, and the pulverized unbound materials into a homogenous mixture to the specified depth. The reclaimer shall be equipped with a computerized integral liquid proportioning system capable of regulating and monitoring the water application rate relative to depth of cut, width of cut, and speed. The reclaimer shall have a mounted spray bar to allow the water to be injected directly into the cutting drum/mixing chamber. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS The cutting drum must have the ability to operate at various speeds independent of the machine’s forward speed to control oversized material and gradation. Perform inspection of the condition of the cutting teeth daily. Replace all worn and broken cutting teeth.
a.Grading Equipment. A self-propelled motor grader capable of shaping the material to the line, grade, and cross section specified.
b.Compaction Equipment. A vibratory pad-foot roller, pneumatic tire roller or double drum vibrator roller for breakdown compaction. Refer to 502.03.08.
c.Spreader or Distributor. A non-pressurized mechanical vane-feed cyclone or screw type machine capable of providing a consistent, accurate and uniform distribution for applying stabilizing agents and additives. The spreader or distributor shall be capable of minimizing dust during construction.
d.Water Trucks. Supply water to the reclaimer or construction operations.
502.03.02 Weather Restrictions.
a.Temperature and Surface Conditions. Place CTB or CMS when the ambient air and surface temperatures are at least 40 F and rising. Do not place material on a frozen subgrade. Do not place CTB or CMS when temperatures are anticipated to be below 40 F within 3 days of the placement.
b.Cold Weather Protection. Protect the completed CTB or CMS from freezing during the seven-day curing period.
c.Precipitation. Any placement during precipitation shall be at Contractor’s risk.
502.03.03 Subgrade Preparation for CTB. Complete the subgrade to line and grade at least 500 ft ahead before beginning construction.
Construct the foundation as specified in Section 204 and Section 208. If traffic or construction equipment are allowed to use the subgrade foundation or preceding layer, distribute the loading over the entire width of the course to aid in obtaining uniform and thorough compaction. Remove rutting by reshaping and recompacting the affected area as specified in Section 204.
502.03.04 Design Mix. The contractor shall submit a mix design report for laboratory testing
along with soil and Portland cement samples for CTB or CMS from the proposed material sources at least 45 days prior to the start of construction for review and approval by Office of Materials Technology (OMT). Review and approval of the mix design by OMT will be based on OMT performing a mix design verification. The proposed material shall be sampled at the source of the material. Sample the materials as specified in the Material Quality Assurance Processes. If the proposed material source for soil is onsite, then obtain representative samples of the existing soil at least every 500 ft of the proposed CTB or CMS placement to develop the mix design in addition to the above requirements. Do not include existing material from beneath the proposed depth in mix design testing. The samples shall be analyzed and tested by an R-18 AASHTO laboratory accredited in the AASHTO Laboratory Test listed below. The AASHTO accredited laboratory shall be approved by OMT. Sampled material must be properly processed and prepared to closely simulate field conditions. The laboratory shall provide the following information as part of the design mix report to the Engineer:
a.Location or Producer of the materials used in the mix design
b.Laboratory Testing required:
1.Sieve Analysis of Fine and Coarse Aggregates AASHTO T27
2.Particle Size Analysis of Soils AASHTO T88
3.Liquid Limit of Soil AASHTO T89
4.Plastic Limit of Soil AASHTO T90
5.Moisture-Density Relations of Soil-Cement Mixtures AASHTO T134
6.Laboratory Determination of Moisture Content of Soil AASHTO T265
7.Classification of Soils and Soil Aggregate Mixtures AASHTO M145
8.Standard Test Methods for Compressive Strength of Molded Soil-Cement Cylinders ASTM D1633-00 Design recommendations shall clearly show for each mix design: optimum moisture content, aggregate gradation and content (if additional aggregate is required), maximum dry density and the proper rate of application for Portland cement necessary to achieve the seven-day compressive strength (450 psi-700 psi for CTB) and (100 psi-300 psi for CMS) or other ranges determined by OMT. Make, cure and test unconfined compressive strength specimens in accordance with ASTM 1633, Method A. The submitted design mix report shall include the design recommendations and all laboratory results/tests used to develop the recommendations. All component materials used in the design mix shall be representative of the materials proposed by the Contractor to be used on the Project. If there is a change in source material of the CTB or CMS, submit materials from the proposed new material source to OMT for review and approval. Using the new materials, the contractor will determine a new or revised mix design for review and approval by OMT. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS A new or revised mix design shall be required when unsatisfactory testing results or other conditions deem necessary. If the contractor for any other deemed reason makes any adjustments to the new or revised mix design, the contractor must submit a revised mix design for review and approval by OMT. Construction shall stop and will only continue once the revised mix design has been approved by OMT. Once the new or revised mix design is approved, then the Contractor may proceed with the control strip. The contractor may not proceed to the control strip without the mix design approval by OMT. Approval of the mix design by the OMT is solely for monitoring quality control and in no way releases the Contractor from their responsibilities.
502.03.05 Control Strip. Construct a 500 ft long control strip to the specified lane width during
the first day of production to verify that the construction process can meet the required gradation, spread rate for cement and the roller pattern needed to obtain the specified density requirement for the entire project. Placement shall not continue unless the control strip has been approved by OMT. Control strips that do not meet the requirements from the determined mix design shall be reworked, re-compacted, or removed and replaced at no additional cost. Use the same method and procedures for the entire project unless adjustments are required to the mix design. Any adjustments to the approved mix design will need to be re-submitted to OMT for review and approval and require a new control strip. If the control strip has not yet been approved by OMT, the Contractor may proceed with the placement at their own risk. However, if the control strip is rejected by OMT, then the Contractor shall rework, re-compact, or remove and replace at no additional cost. Meeting the requirements on the control strip does not relieve the Contractor from meeting the requirements on the entire project. Acceptance of the control strip will be based on obtaining the required design strength validated using the Falling Weight Deflectometer (FWD) testing. For CTB, acceptance of the control strip will be based on the elastic modulus from FWD testing being equal to the designed elastic modulus subject to a minimum of 610 000 psi or as specified. Guidelines for FWD Testing will be according to the Material Quality Assurance Processes. For CMS, acceptance of the control strip will be based on obtaining the required design strength validated using the Falling Weight Deflectometer (FWD) testing. The resilient modulus from FWD testing must be equal to the designed resilient modulus subject to a minimum of 4 500 psi and a maximum of 10 500 psi or as specified in the Contract Documents. Guidelines for FWD Testing will be according to the Administration’s Material Quality Assurance Processes.
502.03.06 Pulverization, Shaping, Stabilization. Pulverize the material to the depth and width
as specified. Add water as necessary to control dust. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
a.Pulverize the material to ensure that the following gradation is met at the completion of moist mixing. Sieve Size Percent Passing for Soils 1-in. 100 No. 4 80 % minimum, exclusive of any gravel or stone. Gravel or stone shall be no more than 2-in. (50 - mm) nominal maximum size.
1.For CTB, refer to 901.01 for Graded Aggregate Base gradation requirements. Protect any buried structures such as bridges, culverts, utilities, drainage pipes, etc. during pulverization and stabilization by stopping or raising the mixing drum at these obstructions if necessary. Repair any damage to these structures at no additional cost. Do not pulverize more than can be completed in a work shift or in the event of precipitation, traffic or cold weather. Maintain a uniform driving surface free of ruts and surface irregularities. Repair any ruts and surface irregularities at no additional cost.
b.Apply the cement at the established application rate according to the approved mix design using an approved spreader/distributor. Use MSMT 254 to verify the spread rate in the presence of the Engineer. The time from addition of cement placement to the start of mixing shall not exceed 30 minutes.
c.Use a pressurized distributor to spray water to adjust the moisture content to at least optimum moisture content if necessary. Limit any variation in the moisture content of the material at the time of cement application to within two percent plus of optimum moisture.
d.Compact and smooth the surface over its full width. Remediate unstable areas encountered below the depth of pulverization as directed by the Engineer. Remediation may consist of greater depths of cement treatment, excavation of unstable material and backfilling with cement stabilized material, and/or incorporation of drainage measures. Perform remediation work as extra work on a unit cost basis.
502.03.07 Grade or Finished Surface Control. Shape the surface of the CTB or CMS to the
specified line, grade, and cross section. Maintain the finished grade within 1/2 in. from the established grade.
502.03.08 Compaction. Compact to a density of at least 97 percent of the maximum dry density
according to T 134. Measure the in-place density according to MSMT 352. Furnish a compaction block as specified in 204.03.04. 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS For CTB, the compacted thickness of any one layer shall not be more than 8 in. The Engineer may approve increasing the compacted depth of a single layer of the CTB when vibrating or other approved types of compacting equipment are used. For in-situ CMS, the compacted thickness of any one layer shall be no more than 12 in. Keep the surface of the compacted material moist during multiple layer construction until covered with the next layer. Place and compact successive layers so that the required total thickness of the CTB or CMS is completed in the same shift. Maintain the moisture in the mixture to within 2 plus percent of the specified optimum moisture at the start of compaction. Begin compaction no more than 20 minutes after mixing to within 2 plus percent of the specified optimum moisture. Complete all compaction operations within 2 hours from the start of the mixing operation. Begin compaction operations at the sides of the course, except on superelevated curves. Overlap the shoulder or berm at least 1 ft and progress toward the center parallel to the center line of the roadway. Begin compaction on superelevated curves at the low side and progress toward the high side. Continue compaction operations until all compaction marks are removed. Perform additional compaction if the density of an area is less than the required percentage of the target density. If additional compaction does not achieve the required percentage of the target density, adjust the moisture content and re-compact. Moisture correction on the nuclear gauge is required for validation of field density. If the density is still below the required percentage of the Target Density but the CTB or CMS is otherwise acceptable as determined, define the area as a new control strip to establish a new Target Density. Take a minimum of five density tests at random locations to determine the average in-place density and to define the new Target Density. The other requirements, such as compressive strength, gradation, and moisture content, need to be verified by OMT on the new control strip. Repeat the control strip and Target Density development process if the uniformity of the mixture changes significantly as determined.
502.03.09 Construction Joints. Create a straight transverse construction joint at the end of each
day’s construction by cutting back into the completed work to form a vertical face. Build the base for large, wide areas as a series of parallel lanes of convenient length and width, complete with longitudinal joints as approved. Longitudinal joints between successive cuts shall overlap a minimum of 6 in. and transverse joints shall overlap a minimum of 2 ft.
502.03.10 Finishing. Complete placement within four hours of initial mixing. Material that is
not fine graded and final rolled within four hours of initial mixing shall be reclaimed again with fresh cement at no additional cost.
502.03.11 Protection and Curing. Maintain the surface of the CTB or CMS in a moist condition
after completion of final finishing until the emulsified asphalt is applied or by being kept continuously moist until the subsequent pavement layers can be placed with a water spray that will not erode the surface of cement treated base course. Apply emulsified asphalt if used for curing no later than 24 hours after completion of the finishing operations. Use distributing equipment as 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS specified in 503.03.01 to apply the emulsified asphalt at the rate of 0.2 gal/yd2. Avoid ponding of the emulsified asphalt. Remove ponding using a sand blotter or an equivalent method as approved. Allow the CTB or CMS to cure for a period of seven days. Close the CTB or CMS to all traffic, except for construction equipment as specified in 502.03.13, during this period unless otherwise approved. Repair damaged areas as directed.
502.03.12 Maintenance. Maintain the CTB or CMS until the layer above is placed. Replace
unacceptable work that cannot be repaired to the full depth of the CTB or CMS. 502.03.13 Subsequent Pavement Layers. Subsequent pavement layers can be placed any time if CTB or CMS is sufficiently rolled to support the required construction equipment without rutting or shoving.
502.03.14 Quality Control Plan (QCP). Submit a Quality Control Plan (QCP) that contains the
field-testing procedures and sampling frequency for cement content, density, moisture content, compaction, depth checks of cement treated base course, and remediation plan for areas that do not meet the requirements. The QCP plan shall also include a calibration report of the cement spreader that confirms the application rate of the cement (lbs/yd
2.and designate a Certified Soils and Aggregate Compaction Technician according to the Administration’s Mid-Atlantic Region Technician Certification Program. The QCP shall be submitted to OMT-Soils and Aggregate Division for review and approval at least 30 days prior to construction. Do not begin construction until the QCP is approved by OMT. The Certified Soils and Aggregate Compaction Technician shall be present at the job site during the placement of the CTB or CMS operations. The Certified Soils and Aggregate Compaction Technician shall be responsible for the required field quality control sampling and testing. Deviations from the QCP shall be grounds for immediate suspension of the CTB or CMS operation. The technician shall perform sampling for quality control, acceptance, split sampling, and verification. Submit quality control test results to the Engineer. Maintain complete records of sampling, testing, corrective actions and quality control inspection results. Provide copies of the reports to the Engineer daily.
502.03.15 Quality Assurance (QA) and Final Acceptance. The Administration will perform
independent QA sampling, testing and inspections according to the Material Quality Assurance Processes manual. Final Acceptance and frequency of QA testing will be according to the following:
a.Mix Design
b.Control Strip (c) Field Compaction (d) Depth Check and Consistency of pulverization 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS
e.Quality Control Plan
f.Application Rate of Portland Cement
502.04 Measurement and Payment
Payment will be full compensation for control strips, falling weight deflectometer testing, pulverization, shaping, compaction, spreading stabilization additive, mixing, in-situ material, emulsified asphalt, water, quality control testing, hauling, setting of lines and grades where specified, and for all material, labor, equipment, tools, and incidentals necessary to complete the work.
502.04.01 Cement Treated Base Course will be measured and paid for at the Contract unit price
per square yard.
502.04.02 Portland Cement for Cement Treated Base Course will be measured and paid for at the
Contract unit price per ton.
502.04.03 Graded Aggregate Base for Cement Treated Base Course will be measured and paid for
at the Contract unit price per square yard.
502.04.04 Select Borrow for Cement Treated Base Course will be measured and paid for at the
Contract unit price per square yard.
502.04.05 Capping Borrow for Cement Treated Base Course will be measured and paid for at the
Contract unit price per square yard.
502.04.06 Cement Modified Subgrade will be measured and paid for at the Contract unit price per
square yard.
502.04.07 Portland Cement for Cement Modified Subgrade will be measured and paid for at the
Contract unit price per ton as determined by the approved mix design. 503 — CHIP SEAL SURFACE TREATMENT 2025 STANDARD SPECIFICATIONS FOR CONSTRUCTION AND MATERIALS CATEGORY 500 PAVING SECTION 503 — CHIP SEAL SURFACE TREATMENT
503.01 Description
Apply one or two seal coats or a prime coat followed by one or two seal coats as specified. The seal coat consists of emulsified asphalt followed by an application of aggregate. The prime coat, when required, consists of preparing and treating an existing surface with emulsified asphalt.
503.02 Materials
MATERIAL SECTION APPLICATION SIZE OR GRADE SPREAD RATE lb/yd 2 SPRAY TEMP F SPRAY RATE SINGLE COAT OR FIRST COAT gal/yd 2 SPRAY RATE FOR SECOND COAT (Double) gal/yd Single or First Coat No. 7 25-50 — — — Aggregate 901 Second (Double Coat) No. 8 20-35 — — — CRS-1 — 70-140 0.3-0.5 0.2-0.4 CRS-2 — 140-160 0.3-0.5 0.2-0.4 RS-1 — 70-140 0.3-0.5 0.2-0.4 Emulsified Asphalts 904.03 Seal Coat RS-2 — 140-160 0.3-0.5 0.2-0.4
503.03 Construction
At least 30 days prior to the start of placement of the chip seal surface treatment, submit a proposed plan, including equipment and material sources, for approval. Protect the treated pavement against damage from all causes. Repair or replace damaged areas as directed.
503.03.01 Equipment. All equipment is subject to approval.
a.Asphalt Distributing Equipment. This equipment shall be inspected and calibrated by the Administration prior to use and shall bear a current Administration inspection
Source: Maryland Standard Specifications for Construction and Materials, 2025 Edition. Pages 622–629 of 1,113.