306 – CEMENT TREATED BASE
300-17 Submit (email or fax) copies of all failing test results (based on a moving average of 4 tests, if appropriate)
and a summary sheet to the Field Engineer on a daily basis. File all reports, records, charts and diaries developed during the progress of construction activities. Upon completion of the contract, all document ation becomes the property of KDOT.
f.Testing Requirements. In the QCP, identify test methods, procedures and equipment proposed for use. Use standard KDOT test methods and properly calibrated m easuring and testing equipment as outlined in Part V. Detail any alternative sampling method, procedure or inspec tion equipment proposed to be used. Such alternatives are subject to review and approval by the DME. Take all samples for tests and perform in-place test s at random locations se lected according to the Contractor’s QC Plan and at the rate s specified in the Sampling and Testi ng Frequency Chart for Cement Treated Base for Quality Control/Quality Assurance Projects in Append ix B, Part V. Retain the latest 10 gradation samples for use by the Engineer. Retain the second half of the latest 10 gradation samples for use by the Engineer.
g.Mix Design. Design a mixture of aggregate and portland cement or fly ash, or both. If fly ash is used in the mixture, address the set time and strength gain as a function of the ambient temperature. Design the mixture according to the following requirements:
1.The compressive strength shall be between 650 and 1600 psi. Any test correlating to the maximum value or higher requires scoring or sa wing joints in the base that fall within the failing test se ction (from previous to next passing test sections). Determine compressive strength at 7 days, according to Part V.
2.Submit a single point gradation for the combined ag gregates along with a plus/minus tolerance for each sieve to the Engineer. The plus/minus tolerances shall be used by the Contractor to perform quality control checks and by the Engineer to perform aggreg ate gradation verification testing. Perform tests on the combined materials.
3.Submit the mix batch weights in an acceptable manner to the DME. Address the initial set times (specified in AASHTO T 154) and placement times (with regards to the set times) in the proposed mix design.
4.Submit laboratory compressive strength test results on a minimum of 1 set of 3 plugs, produced from the proposed mix design and utilizing the actual materials proposed for use on the contract.
5.Submit the test results 2 weeks prior to the anticipated date for using the design on the contract. The Engineer will review the design within 5 working days of receipt. The Engine er may perform any testing necessary to verify the adequacy of the Contractor’s design. If the Engineer calls for verification tests, supply the Engineer with the necessary materials to enable the Engineer to test the mix properties within 5 working days of notification.
6.Submit any proposed changes to the approved mi x design to the DME for approval before implementing the proposed changes.
h.Corrective Action. In the QCP, identify procedures for notifying the Engineer when corrective measures must be implemented, and for halting production. Notify the Engineer when the moving average test result trend line for any property approaches the specification limits. Cease operations when 2 consecutive moving average points fall outside the specification limits, or 2 consecutive single compressi ve strength tests exceed the specificati on limits. Ceasing operations is the Contractor’s responsibility. Quality control tests for this determination include aggregate gradation, compliance with the mix design band and in-place density of CTB. Failure to cease operations for the c onditions cited above will subject all su bsequent material to rejection, or acceptance at a reduced price, as determined by the Engineer. The Engineer may examine materials represented by individual test results, which lie beyond the Contractor’s normal quality control testing variation. The investigation may be based on either Contractor or KDOT test results. The information from add itional testing (including testing of in-p lace pavement) may be used to define unacceptable work according to SECTION 105 . The Engineer will apply appropriate price reductions or initiate corrective action. If a dispute exists between the Engineer and Contractor about the validity of any test results other than compressive strengths or thickness determination, the K DOT District Materials Laboratory or MRC will perform referee testing. If one of the disputed KDOT test results was generated at the MRC, then an independent laboratory agreeable to both parties will be se lected. The AASHTO Accr editation Program shall have approved the selected laboratory for the appropriate test procedure. If refer ee testing indicates that KDOT test results are correct, the Contractor is responsible for the cost of additional testing, including referee testing performed at the MRC. If the 306 – CEMENT TREATED BASE
300-18 referee testing indicates that the Contractor test results are correct, KDOT is responsible for the cost of additional
testing.
i.Non-Conforming Materials . In the QCP, specifically address how non-conforming materials will be controlled and identified. Establish and maintain an effective and positive system for controlling non-conforming material, including procedures for its identifica tion, isolation and disposition. Reclaim or rework non-conforming materials according to procedures acceptable to the Engineer. Identify all non-conforming materials and products to prevent use, shipment and intermingling with conforming materials and products. Provide holding areas, mutually agreeable to the Engineer and Contractor. The Engineer will determine if reclaiming or rewo rking of non-conforming materials is allowed. 306.3 MATERIALS Provide materials that comply w ith the applicable requirements. Concrete Admixtures & Curing Mate rial .............................................................. DIVISION 1400 Portland Cement and Fly Ash ............................................................................... DIVISION 2000 Water for CTB ....................................................................................................... DIVISION 2400 Aggregates for CTB .................................................................................................... DIVISION 1100 306.4 CONSTRUCTION REQUIREMENTS
a.Preparation and Maintenance of the Subgrade. Before placing any CTB material on any section, complete the ditches and drains along that section to e ffectively drain the highway. Use automatic grade control equipment to trim the surface of the subgrade to the line, grade and cross-section as shown in the Contract Documents. Maintain the subgrade to the as-constructed condition under other contract bid items, repairing any encountered defects to the specifications of the previous bi d items. Maintain the subgrade surface to readily drain at all times. Protect the subgrade from damage when handling materials, tools and equipment. Do not store or stockpile materials on the subgrade. Do not place ma terial or lay CTB on a fr ozen or muddy subgrade. Lightly spray the subgrade with water to obtain a thoroughly moistened condition before the CTB is placed. Do not puddle water on the grade. Do not place CTB on frozen subgrade. Do not deposit any material un til the subgrade or base has been checked and approved by the Engineer.
b.Mixing the Materials. Do not place CTB on the project until the Engineer has reviewed and approved the submitted mix design. Plant mix the aggregate, cemen ting agent and water according to the approved mix design. Control the charge in a batch mixer, or the rate of feed to a continuous mixer (pugmill), to allow complete mixing of all the materials. Mix the materials to produce a homogeneous mixture. Do not use frozen aggregate. Take all compressive strength samples at the plant si te. Compact the samples pr ior to the CTB reaching its initial set.
c.Spreading and Compacting the CTB . The maximum compacted thickness of a single lift is 6 inches. If the thickness is greater than 6 inches, spread and compact the subgrade in multiple lifts of equal thickness with a maximum lift thickness of 6 inches. If the base is spread in multiple lifts, offset the longitudinal joints by at least 6 inches. If multiple lifts are placed, keep th e surface of each lift moist until the succeeding lift is spread. Cover the exposed lower lift with the final lift the same day the lower lift is placed. Compact each lift of CTB to a minimum of 95% of the standard density. Compact the CTB within 2 hours from the time the water and cementing agent is added to the aggregate, or before the mixture reaches the initial se t, whichever is the shorter timeframe.
d.Compaction Determination. Determine dry density and moisture content according to Part V. 306 – CEMENT TREATED BASE
300-19 If the mix is stiff (can be slip-form ed), determine the standard density by averaging the 3 most recent field
molded densities using plant mixed base material. Compact one standard mold (using plant mixed material with the proper moisture content) for each day’s operation as specified in KT-37. If the mix is fluid (requires forming), determine the Standard Dry Density by averaging the 3 most recent consolidated unit weight test results (K T-20). It will be necessary to convert the unit weight (wet density) into a standard dry density which also requires the percent of moisture (KT-11 (4) ) to be known. Use Equation 1 to determine the standard dry density. Equation 1: 100]) / [%Moisture (1 y Wet Densitty Dry Densi Standard Determine the density of the CTB within 1 day of the compaction operations. The Engineer may verify the Contractor’s density test results by conducting density tests at random. If the comparison is not favorable, the DME will investigate to determine the cause and may suspend production until corrective action is taken.
e.Trimming and Finishing the CTB. Trim and recompact the CTB within 2½ hours of the time the water and cementing agent is added to the aggregate. Trim and compact the CTB to the grades, lines and typi cal cross sections shown in the Contract Documents. Dress the edge slopes and joints between sections. Use automatic grade control equipm ent to trim the surface of the CTB to line grade and cross section. Keep the surface of the CTB moist during all finishing operations. Perform the finishing and compac ting operations to produce a smooth, dense surface, free of surface compaction planes, cracks, ridges or loose material. If required, lightly scarify the surface of the CTB to l oosen any imprints left by the trimming and compacting equipment. Recompact the surface of the CTB. At the end of each day’s operations, construct a straight transverse construction joint by cutting back into the completed work to form a vertical face. Place a protectiv e covering of earth on the ne wly constructed CTB a distance back of the joint for turning of equipment used on the following day’s work. Upon satisfactory performance, the Engineer may approve the use of equipment that combines the placing, compacting and finishing operations.
f.Protection and Curing. Keep the surface of the CTB moist until the curing material is applied. Apply the curing material immediately after completing the trimming and finishing. Protect the CTB against the loss of moisture for a curing period of 7 days (unless the Contractor’s mix design test results justify a different curing period). Protect the CTB against freezing during the curing period. Apply a wax-based liquid membrane-forming compound for the curing material. The minimum application rate for wax-based liquid membrane-forming compound is 0.12 ga llons per square yard. Use an enclosed spray system that minimizes wind influence and obtains the proper applicat ion rate. Keep all traffic and construction equipment off the CTB. The only exception is the equipment used to appl y the curing material. Cover the surface and edges of the CTB with a complete, uniform coverage. Us e a hand sprayer in inaccessible areas. If the wax-based liquid membrane-forming compound will be in place for more than 30 days, reapply a single coat at the single application rate within 7 days of placing the pavement. At locations where it is necessary to carry traffic acro ss the CTB, place a layer (8 inches or greater, compacted depth) of stable earth (sand-clay) over the CTB. The Contractor may place portland cement concrete pavement (PCCP) on the CTB after a minimum of 24 hours, provided all traffic and construction equipment is kept off the CTB. The Contractor assumes the risk of 7-day compressive strength requirements when PCCP is placed early. To promote cracking through the full depth of the base, score or cut the finished CTB surface to coincide with the pavement joint locations, in a parallel manner and within 1 foot: if the 7-day compressive strength exceeds 1600 psi. (Note: This does not apply if the CTB has developed cracks at regular intervals prior to placing the PCCP.) if the Contractor opts to place the PCCP over th e CTB before the 7-day compressive strength is determined. The Engineer may waive this requirement when the Contractor’s control charts for CTB shows a history that the 7-day compressive strength is below 1600 psi.
Source: Kansas Standard Specifications for State Road and Bridge Construction, 2015 Edition. Pages 163–165 of 978.