304.01 230 SECTION 304 – SOIL-CEMENT BASE
304.01 Description ................................ ................................ ................... 230
304.02 Materials ................................ ................................ ...................... 230
304.03 Equipment ................................ ................................ .................... 231
304.04 Limitations ................................ ................................ ................... 231
304.05 Preparing the Existing Subgrade ................................ .................. 232
304.06 Pulverizing ................................ ................................ ................... 232
304.07 Cement Application, Mixing, and Spreading ............................... 232
304.08 Compaction ................................ ................................ .................. 233
304.09 Finishing ................................ ................................ ...................... 234
304.10 Construction Joints ................................ ................................ ....... 234
304.11 Thickness and Surface Tolerances ................................ ............... 234
304.12 Curing ................................ ................................ .......................... 234
304.13 Reconstruction and Replacement ................................ ................. 235
304.14 Traffic ................................ ................................ .......................... 235
304.15 Maintenance ................................ ................................ ................. 235
304.16 Method of Measurement ................................ .............................. 236
304.17 Basis of Payment ................................ ................................ .......... 236
DESCRIPTION
304.01 Description
This work consists of mixing in -place or select soil with Portland cement, and moistening and compacting the soil -cement mixture in one or more courses. MATERIALS
304.02 Materials
Provide materials as specified in: Portland Cement, Type I ................................ ........................ 901.01 Portland-Pozzolan Cement, Type IP ................................ ...... 901.01 304.03 231 Bituminous Curing Seal, Emulsified Asphalt, Types allowed for Tack Coat in 403 ............................... 904.03 Select Material for Soil -Cement Base ................................ .... 921.05 Provide water as specified in 921.01. Provide emulsified asphalt, of a type allowed for Tack Coat in 403, meeting the test requirements specified in Table 904.03-1. The Contractor may select the kind of bituminous material to use for curing. Submit a sample of the cement and the select material to be used to the Materials and Tests Laboratory for approval at least 15 days before use. EQUIPMENT
304.03 Equipment
Provide a mechanical cement spreader that will distribute the cement uniformly at the requir ed rate without excessive loss. Provide mechanical mixers meeting 309.03.B; or a stationary mixing plant meeting 309.03.A. CONSTRUCTION REQUIREMENTS
304.04 Limitations
Only process the amount of so il-cement that will be covered with the succeeding stage of base or pavement construction during the same construction season. Only apply cement to subgrade or select material that is unfrozen and when the air temperature in the shade is at least 40 °F and rising. Limit application of cement to an area that will allow for continuous operations and for the completion of all but the final surface finish within three hours from the time the cement is applied. Do not leave any uncompacted soil -cement mixture undisturbed for more than 30 minutes. If the uncompacted soil -cement mixture is wetted by rain so that the average moisture content exceeds the specified tolerance, reconstruct the entire section as specified in 304.13. 304.05 232 304.05 Preparing the Existing Subgrade If in-place soil is to be used, grade and shape the area to be treated as required to construct the soil -cement base in reasonably close conformity with the lines, grades, thickness, and cross -sections shown on the Plans. Place any additional soil needed as directed and blend with the in -place material. Remove unsuitable soil or material and replace with acceptable soil. When removing and replacing unsuitable soil, and placing additional soil, comply with the pertinen t provisions of 203. Where only select material is to be used, prepare the subgrade as specified in 205, 207, or 302, whichever is applicable. Slightly dampen the subgrade just before spreading the select material or soil - cement mixture upon it.
304.06 Pulverizing
If required, before applying cement, scarify the soil and pulverize for sufficient depth and width to achieve the cross -section shown on the Plans. Pulverize the soil -cement mixture so that, at the completion of mixing, at least 80% of the dry material passes the No. 4 sieve and 100% of the combined material passes the 1 -inch sieve, exclusive of gravel or stone retained on these sieves. Remove material retained on a 3 -inch sieve and other unsuitable material.
304.07 Cement Application , Mixing, and Spreading
Use an appro ved mechanical spreader to spread select material on the subgrade before mixing to the required thickness, width, and cross -section. The Engineer will establish the percentage of cement to be used based on tests of the in -place soil or select material. Apply the specified quantity of Portland cement uniformly over the spread select material or in -place soil. Do not apply cement if the moisture content of the soil exceeds 3% the optimum moisture content specified by the Engineer for the soil -cement mixtur e. Before starting mixing, replace spread cement that has been lost due to the Contractor’s negligence at no additional cost to the Department. Use a mechanical mixer to perform road mixing. At least one pass of the mixer may be required before adding wa ter. When required, add water uniformly by distributors or other approved methods to bring the mixture to 304.08 233 the required moisture content. Continue mixing until the pulverization requirements of 304.06 are met and a homogeneous m ixture of soil, cement, and water is obtained. If using stationary plants or mixers, ensure they are equipped with feeding and metering devices that will introduce the cement, soil, and water into the mixer in the quantities specified. All material fed in to the plant shall travel the full length of the pugmill. Continue mixing until a uniform and intimate mixture of cement, soil, and water has been obtained. Transport the mixture from the plant to the road in numbered trucks equipped with tight metal rea r- end dump beds. Provide a sufficient number of trucks to ensure satisfactory progress of construction operations. Spread the material using approved mechanical spreaders within one hour after being discharged from the mixer and in ample time to secure c ompaction during daylight hours. If the moisture content of the uncompacted mixture exceeds the specified tolerance, reconstruct the material as specified in
304.13 When mixing, handling, and placing the base material, take car e to
prevent segregation. When using select material, place shoulder material for a width of at least 3 feet before spreading the base material in order to confine the base material and allow satisfactory compaction along the edges of the base.
304.08 Compaction
At the start of compaction, the percentage of moisture in the mixture and in the pulverized soil lumps, based on oven -dry weights, shall not vary more than plus or minus 2% from the specified optimum moisture content, a nd shall be less than the quantity that will cause the soil -cement mixture to become unstable during compaction and finishing. The Contractor may use any type of compaction equipment that will produce the required results. Extend compaction efforts over the edges of the base material into the shoulders. During final rolling, reshape the surface of the base course and lightly scarify to loosen any imprints left by the compacting or reshaping equipment. The Department will divide the soil -cement base into l ots of approximately 10,000 square yards for density testing purposes, and will perform five density tests on each lot. The average dry density of each lot shall be not less than 95% of maximum density as determined according to AASHTO T 134, and no individual test shall be less than 92% of the maximum density. 304.09 234 Rework material not meeting the required density at no additional cost to the Department, unless conditions exist as described in 304.13. At the beginning of a project or at any time thereafter the Engineer may evaluate the rolling procedures. Complete compaction and final shaping operations within three hours from the time the cement is mixed with the soil or select material.
304.09 Finishing
After compaction, shape the surface of the soil -cement to the required lines, grades, and cross -sections. Sprinkle the surface until it is damp, but not wet, and clip with a motor grader as directed by the Engineer. Dispose of the material removed by clipping. Following clipping, seal the surface with a roller.
304.10 Construction Joints
At the beginning of each day’s construction, form a straight transverse construction joint by cutting back into the previously completed work to form a true vertical face free of loose or shattered material.
304.11 Thickness and Surface Tolerances
The Department will determine the thickness of the base by measuri ng test holes dug at random locations. The measured thickness shall not deviate from that shown on the Plans by more than plus 1 -1/2 inches or minus 1 inch. Reconstruct or replace work found not to be within this tolerance as specified in 304.13. The finished base shall meet the surface requirements specified in 407.18, and when tested as specified in that Subsection, the deviation of the surface from the testing edge of the straight edge shall not exc eed 1/2 inch.
304.12 Curing
After the soil -cement has been finished, protect it against drying for 7 days by applying one of the bituminous materials specified in 304.02. Apply the curing material at th e rate shown on the Plans as soon as possible after completing the base construction, but in no case later than 24 hours after completing finishing operations. Maintain the finished soil -cement in a continuously moist condition until the curing material i s placed. 304.13 235 If construction equipment or other traffic must use the bituminous -covered surface before the bituminous material has dried sufficiently to prevent pickup, first apply sufficient granular cover, consisting of clean sand passing a 3/8-inch sieve o r other approved material. During the 7 -day protection period, maintain the curing material to ensure that all the soil -cement remains effectively covered. Protect finished portions of soil -cement that are traveled on by equipment used in constructing an adjoining section to prevent equipment from marring or damaging completed work. Sufficiently protect soil -cement from freezing for 7 days after its construction.
304.13 Reconstr uction and Replacement
If reconstruction becomes necessary, repeat all construction procedures and adhere to the time limitations specified in 304; however, the Engineer will determine the amount of cement to be used in the reconst ructed soil -cement base. Replace faulty work for the full depth of treatment. Correct low areas by replacing the material for the full depth of treatment rather than by adding a thin layer of soil -cement to the completed work.
304.14 Traffic
The Contractor may open completed portions of soil -cement to local traffic after the 7 -day curing period, provided the soil -cement has hardened sufficiently to prevent marring or distorting of the surface by equipment or traffic. However, provide ingress and egress for property owners and public crossroads as necessary before the 7 -day curing period.
304.15 Maintenance
Maintain the soil -cement in good condition until all work has been completed and accepted. Immediately repair defects that may occur at no additional cost to the Department. 304.16 236 COMPENSATION
304.16 Method of Measurement
The Department will measure:
1.Processing by the square yards of completed base, as determined using the actual length measured along the centerline of the roadbed and the width shown on the Plans or designated by the Engineer.
2.Material moved to prepare the existing subgrade, in accordance with 304.05.
3.Portland Cement incorporated in the work by th e ton in accordance with 109.
4.Bituminous Material used for curing seal by the ton in accordance with 109.
5.Water used in mixing and finishing operations by the M.G. (1,000 gallons) using ca librated tanks or distributors, or accurate meters.
6.Select Material for Soil -Cement Base, added to that already on the road, by the cross -section method in approved borrow pits. The Department will not measure or pay for water added to emulsified aspha lt used for curing.
304.17 Basis of Payment
The Department will pay for accepted quantities at the contract prices as follows: Item Pay Unit Processing (Soil -Cement Base) Square Yard Portland Cement (Soil -Cement Base) Ton Bituminous Material Ton Water MG Select Material (Soil -Cement Base) Cubic Yard 304.17 237 The Department will not pay for reconstructive work, including additional cement and processing , required due to the Contractor’s negligence. The Department may use net certified weights as a basis of measurement for cover material aggregate, subject to correction for aggregate that is lost, wasted, or otherwise not incorporated in the Work. 306.01 238 SECTION 306 – PORTLAND CEMENT CONCRETE BASE
306.01 Description ................................ ................................ ................... 238
306.02 Materials ................................ ................................ ...................... 238
306.03 Equipm ent ................................ ................................ .................... 239
306.04 Proportioning ................................ ................................ ............... 239
306.05 General ................................ ................................ ......................... 239
306.06 Surface Finish and Tolerances ................................ ..................... 239
306.07 Integral Curb ................................ ................................ ................ 239
306.08 Tolerance in Base Thickness ................................ ........................ 240
306.09 Method of Measurement ................................ .............................. 240
306.10 Basis of Payment ................................ ................................ .......... 240
DESCRIPTION
306.01 Description
This work consists of constructing a single course of Portland Cement Concrete Base, with or without reinforcement, as s pecified, on a prepared surface. MATERIALS
306.02 Materials
Provide materials as specified in: Portland Cement, Type I ................................ ........................ 901.01 Fine Aggregate ................................ ................................ ............................... 903.01 Coarse Aggregate ................................ ................................ ... 903.03 Concrete Reinforcement ................................ ............................. 907 Curing Materials ................................ ................................ ......... 913 Water ................................ ................................ ...................... 921.01 Air Entraining Admixtures ................................ ............. 921.06.A.2 Chemical Admixtures and Additives ................................ ..... 921.06
Source: Tennessee Standard Specifications for Road and Bridge Construction, 2021 Edition. Pages 239–246 of 1,072.