401General Concrete

- GENERAL CONCRETE GENERAL CONCRETE

401.1DESCRIPTION

Provide the grades of concrete sp ecified in the Contract Documents. See SECTION 402 for specific requirements for Structural Concrete. See SECTION 403 for specific requirements for On Grade Concrete. See SECTION 404 for specific requirements for Prestressed Concrete.

401.2MATERIALS

Provide materials that comply w ith the applicable requirements. Aggregate ............................................................................................................... ….. DIVISION 1100 Admixtures and Plasticizers .................................................................................. ….. DIVISION 1400 Grade 2 Calcium Chloride ...................................................................................... ….. DIVISION 1700 Cement, Fly Ash, Silica Fume, Slag Cement and Blended Supplemental Cementitious........................................................................................................... …. DIVISION 2000 Water ………………………………………………………………. ..................... ….. DIVISION 2400

401.3CONCRETE MIX DESIGN

Do not place any concrete on the project until the Engi neer approves the concre te mix designs. Once the Engineer approves the concrete mix design, do not make changes without the Engineer’s approval. Take full responsibility for the actual proportions of the concrete mix, even if the Engineer assists in the design of the concrete mix. Provide aggregate gradations that comply with DIVISION 1100 and Contract Documents. If desired, contact the DME for available information to help determine approximate proportions to produce concrete having the required characteristics on the project. Submit all concrete mix designs to the Engineer for review and approval. Submit completed volumetric mix designs on KDOT Form No. 694 and all required attachments at least 60 days prior to placement of concrete on the project. The Engineer will provide an initial review of the design within 5 business days following submittal. Include the following with the mix design data:

56 days for all bridge overlays, Moderate Permeability Concrete, and any project with over 250 cubic yards of concrete (this includes structural co ncrete, on grade concrete etc.). Provide the test data for each mix, tested at the highest paste content (cementitious and water) that meets subsection 401.3h. Submit accelerated cure procedures fo r the Engineer’s approval. The field verification test procedure must be the same test procedure as the mix design approval test.

concrete utilizing all actual materials proposed for use on the project at designated percentages.

plus/minus tolerances to perform quality control checks and by the Engineer to perform aggregate grading verification testing. The tests may be performed on the co mbined materials or on individual aggregates, and then theoretically combined to determine compliance.

from the mix design with the highest water to cementitious ratio for the project, utilizing all actual materials proposed for use on the project at designated percentages.

standard deviation selected for use in subsection 401.3b.

applicable. - GENERAL CONCRETE After initial review, the Engineer will perform any testing necessary to verify the design. This may include a 3 cubic yard test batch at the producing plant. Mix designs will remain approved when verification testing for strength and permeability conducted within the last 12 months indicate continued compliance with the specifications and percentages of constituents including aggregate and cementitious materials and product, type and supplier of admixtures remain the same. Test results on the same mix from other sources are acceptable. Provid e ASTM C 1567 results on an annual basis if the mix includes supplemental cementitious materials (SCM). Improvements in concrete strength, workability, durability and permeability are possible if the combined aggregate grading is optimized. Procedures found in ACI 302.1 or other mix design techniques, approved by the Engineer, are acceptable in optimizing the mix design. A water-reducing admixture for improving workability may be required. Adjust the designated slump accordingly. With the exception of concrete for pavement as shown in SECTION 403, use the middle of the specified air content range of 6½ ± 1.5% for the design of air entrained concrete. Maximum air content is 10%. Take immediate steps to reduce the air content whenever the air content exceeds 8%. Determine air content by KT-19 (Volumetric Method). A regularly calibrated KT-18 (Pressure Method) meter may be used for production with random verification by the Volumetric Method. See KT-19 for special requirements when using the Volumetric Method with high cementitious concretes or mixtures with midrange water reducers or plasticizers. Delay the commencement of tests from 4 to 4½ minutes after the sample has been taken from a continuous mixer. If a batch type mixer is used, take the tests at the point of placement and begin testing immediately.

day compressive strength test data from similar concrete mixtures. Similar mixtures are within 1000 psi of the specified 28-day compressive strength, and are produced w ith the same type and sources of cementitious materials, admixtures and aggregates. Consider sand sources the same, provided they are not more than 25 miles apart on the same river and no tributaries enter the river between the 2 points. Consider crushed locations similar if they are mined in one continuous operation, and there is no significant change in geology. Mixes that have changes of more than 10% in proportions of cementitious materials, aggregates or water content are not considered similar. Air entrained mixes are not considered similar to non-air entrained mixes. Mixes tested with admixtures are not the same as mixes tested without those admixtures. Test data should represent at least 30 separate batches of the mix. One set of data is the average of at least 2 cylinders from the batch. The data shall represent a minimum of 45 days of production within the past 12 months. Do not include data over 1 year old. When fewer than 30 data sets are available, the standard deviation of the data must be corrected to compensate for the fewer data points. Provide a concrete mix design that will permit no more than 5% of the 28-day compressive strength tests to fall below the specified 28-day compressive strength (f’c) based on equation A, and no more than 1% of the 28-day compressive strength tests to fall below th e specified 28-day compressive strength ( f’c) by more than 500 psi based on equation B. Equation A: f’cr = f’c + 1.62 *k*s Equation B: f’cr = (f’c-500) + 2.24 *k*s Where: f’cr = average 28-day compressive strength required to meet the above criteria. f’c = specified 28-day compressive strength s = standard deviation of test data k = constant based on number of data points n = number of data points k = 1.3 – n / 100, where 15 < n < 30 k = 1, where n > 30 Provide a concrete mix design that has an average comp ressive strength that is equal to the larger of Equation A or Equation B. Submit all supporting test data with the mix design. - GENERAL CONCRETE All other concrete mix designs. For concrete mixes that have fewer than 15 data points, or if no statistical data is available, use Equations A and B to calculate f’cr using the following values. s = 20% of the specified 28-day compressive strength (f’c) k = 1

Documents, select the type of portland cement or blended hydraulic cement according to TABLE 401-1. Design concrete with a maximum water to cementitious ratio of 0.50 and minimum cementitious content of 480 lbs per cubic yard except for concrete for pavement and shoulders.

SCMs such as fly ash, slag cement, silica fume or blended SCM from an a pproved source as a partial replacement for portland cement or blended hydraulic cement. Obtain the Engineer’s approval before substituting SCMs for Type III cement. Changes in SCM or cement will require a new mix design approval.

allowable substitution rates noted in TABLE 401-2. Substitute 1 pound of SCM for 1 pound of cement.

TABLE 401-2: ALLOWABLE SUBSTITUTION RATE FOR SUPPLEMENTARY CEMENTITIOUS MATERIAL. Material Substitution Rate* Slag Cement 40% Maximum Fly Ash 25% Maximum Blended SCM 25% Maximum Silica Fume 5% Max Total Combined 50% * Total Substitution Rate includes material in preblended cements and blended SCMs.

Voids, Surface Resistivity, or Rapid Chloride Permeability using the parameters described in subsection 401.3a.

the project’s mix design concrete materials at their designated percentages. Provide a mix with a maximum expansion of 0.10 % at 16 days after casting. ASTM C 1567 is not necessary for concrete modified with only silica fume. TABLE 401-1: PORTLAND CEMENT & BLENDED HYDRAULIC CEMENT Concrete for: Type of Cement Allowed On Grade Concrete Type IP(x) Portland-Pozzolan Cement Type IS(x) Portland- Slag Cement Type IT(Ax)(By) Ternary Blended Cement Type II Portland Cement All Concrete other than On Grade Concrete. Type I Portland Cement Type IP(x) Portland-Pozzolan Cement Type IS(x) Portland- Slag Cement Type IT(Ax)(By) Ternary Blended Cement Type II Portland Cement High Early Strength Concrete Type III Portland Cement Type I, IP(x), IS(x), IT(Ax)(By), or II Cement may be used if strength and time requirements are met. - GENERAL CONCRETE When used, add silica fume with other cementitious materials during batching procedures. If the silica fume cannot be added to the cementitious materials, add th e loose silica fume to the bo ttom of the stationary drum that is wet, but has no standing water, before adding the dry materials. The Engineer may approve shreddable bags on a performance basis, only when a central batch mixing process is used. If so, add the bags to half of the mixing water and mix before adding cementitious materials, aggregate and remainder of water. Mix silica fume modified concrete for a minimum of 100 mixing revolutions.

of strength tests representing the mixes proposed for use. The strength data may come from previous KDOT project records or from a laboratory regularly inspected by Cement and Concrete Reference Laboratory (CCRL), and shall equal or exceed the strength requirements for the Grade sp ecified in the Contract Documents as determined by subsection 401.3b. Perform compressive strength tests according to KT-76.

TABLE 401-3: CONCRETE STRENGTH REQUIREMENTS Specified 28 Day Compressive Strengths, minimum, psi f’c Grade of Concrete: Non Air Entrained/Air Entrained Concrete Grade 7.0 7,000 Grade 6.0 6,000 Grade 5.0 5,000 Grade 4.5 4,500 Grade 4.0 4,000 Grade 3.5 3,500 Grade 3.0 3,000 Grade 2.5 2,500

and time requirements specified in the Contract Documents. Unless otherwise specified, design high early strength concrete for pavement at a minimum of 1 of the Contractor’s standard deviations above 2400 psi (cylinders) at 24 hours. Submit complete mix design data including proportions and sources of all mix ingredients, and the results of time and strength tests representing the mixes proposed for use. The strength and time data may come from previous KDOT project records or from an independent laboratory, and shall equal or exceed the strength and time requirements listed in the Contract Documents.

concrete application not to exceed 5 inches except wh ere controlled by maximum allowable slumps stated in SECTIONS 402, 403 and 404 . Reject concrete with a slump that limits the workability or placement of the concrete.

a maximum 28 day Volume of Permeable Voids of 12.0% as per KT-73, a minimum 28 day surface resistivity of 9.0 kΩ-cm as per KT-79, or a maximum 56 day Rapid Chloride Permeability of 3,000 Coulombs as per AASHTO T- 277. The field verification test procedure must be the same test procedure as the mix design approval test.

Verify that the admixtures used are compatible and will work as intended without detrimental effects. Use the dosages recommended by the admixture manufacturers. Incorporate and mix the admixtures into the concrete mixtures according to the manufacturer’s recommendations. Determin e the quantity of each admixture for the concrete mix design. The Engineer will allow minor adjustments to the dose rate of admixtures to compensate for environmental changes during placement without a new concrete mix design or trial batch. - GENERAL CONCRETE Redosing is permitted to control slump or air content in the field, when approved by the Engineer, time and temperature limits are not exceeded, and at least 30 mixing revolutions remain before redosing. Redose according to manufacturer’s recommendations. If another admixture is added to an air-entrained concrete mixture, determine if it is necessary to adjust the air-entraining admixture dosage to maintain the specified air content.

with reinforcing steel and require early strength development to expedite opening to traffic, a non-chloride accelerator may be approved. The Engineer may approve the use of a Type C or E accelerating admixture. A Grade 2 calcium chloride accelerator may be used when patching an existing pavement more than 10 years old. Add the calcium chloride by solution (the solution is considered part of the mixing water).  For a minimum cure of 4 hours at 60°F or above, use 2% (by dry weight of cement) calcium chloride.  For a minimum cure of 6 hours at 60°F or above, use 1% (by dry weight of cement) calcium chloride.

and finishing properties of the concrete mix, the Engineer may allow the use of water-reducers and set-retarders. Verify that the admixtures will work as intended without detrimental effects. If the Engineer approves the use of water- reducers and set-retarders, their continued use depends on their performance. If at any point, a water-reducer is used to produce a slump equal to or greater than 7 ½ inches, comply with subsection 401.3g.

further addition of water, and/or retards the setting of concrete. Flowing concrete is defined as having a slump equal to or greater than 7 ½ inches while maintaining a cohesive nature. Include a batching sequence in the concrete mix design. Consider the location of the concrete plant in relation to the job site, and identify when and at what location the water reducer or plasticizer is added to the concrete mixture. Manufacturers of plasticizers may recommend mixing revolutions beyond the limits specified in subsection

401.8If necessary, address the additional mixing revolutions in the concrete mix design. The Engineer may allow up

to 60 additional revolutions when plasticizers are designated in the mix design. Before the concrete mixture with a slump equal to or greater than 7 ½ inches is used on the project, conduct tests on at least 1 full trial batch of the concrete mix design in the presence of the Engineer to determine the adequacy of the dosage and the batching sequence of the plasticizer to obtain the desired properties. Determine the air content of the trial batch both before and after the addition of the plasticizer. Monitor the slump, air content, temperature and workability at regular intervals of the time period from when the plasticizer is added until the estimated time of completed placement. At the discretion of the Engineer, if all the properties of the trial batch remain within the specified limits, the trial batch may be used in the project. Do not add water after plasticizer is added to the concrete mixture.

401.4REQUIREMENTS FOR COMBINED MATERIALS

yards weighing 94 pounds net. Measur e bulk cement by weight. In either case, the measurement must be accurate to within 0.5% throughout the range of use.

equipment is subject to the same controls as required fo r cement. Provide positive cut off with no leakage from the cut off valve. Cementitious materials may be weighed accumulatively with the cement or separately. If weighed accumulatively, weigh the cement first.

of use.

required. If liquid admixtures are used in small quantities in proportion to the cement as in the case of air-entraining agents, use readily adjustable mechanical dispensing equipment capable of being set to deliver the required quantity and to cut off the flow automatically when this quantity is discharged. - GENERAL CONCRETE

writing at least 2 weeks in advance of producing the aggregate. Include the source of the aggregate and the date production will begin. Failure to notify the Engineer, as required, may result in rejection of the aggregate for use as OGCA. Maintain separate stockpiles for OGCA at the quarry and at the batch site and identify them accordingly.

for obtaining samples of the aggregates. Provide adequate and safe laboratory facilities at the batch site allowing the Engineer to test the aggregates for compliance with the specified requirements. KDOT will sample and test aggregates from each source to determine their compliance with specifications. Do not batch the concrete mixture until the Engineer has determined that the aggregates comply with the specifications. KDOT will conduct sampling at the batchi ng site, and test samples according to the Sampling and Testing Frequency Chart in Part V. For QC/QA contracts, establish testing intervals within the specified minimum frequency. After initial testing is complete, and the Engineer has determined that the aggregate process control is satisfactory, use the aggregates concurrently with sampling and testing as long as tests verify compliance with specifications. When batching, sample the aggregates as n ear the point of batching as feasible. Sample from the stream as the storage bins or weigh hoppers are loaded. If samples cannot be taken from the stream, take them from approved stockpiles, or use a template and sample from the co nveyor belt. If test results indicate an aggregate does not comply with specifications, cease concrete production using that aggregate. Unless a tested and approved stockpile for that aggregate is available at the batch plan t, do not use any additional ag gregate from that source and specified grading until subsequent testing of that aggregat e indicate compliance with specifications. When tests are completed and the Engineer is satisfied that process control is satisfactory, production of concrete using aggregates tested concurrently with production may resume.

maintaining concrete production. Mark the approved stockpile with an "Approved Materials" sign. Provide a suitable stockpile area at the batch pl ant so that aggregates are stored without detrimental segregation or contamination. At the plant, limit stockpiles of tested and approved coarse, fine and intermediate aggregate to 250 tons each, unless approved for more by the Engineer. If mixed aggregate is used, limit the approved stockpile to 500 tons, the size of each being proportional to the amount of each aggregate to be used in the mix. Load aggregates into the mixer such that no material foreign to the concrete or material capable of changing the desired proportions is included.

mixed and used when representative samples taken anywhere in the stockpile indicated a uniform gradation exists.

storage or stockpiled on the site from any damage by climatic conditions which would change the characteristics or usability of the material.

moisture content in the aggregate varies by more than the above tolerance, take whatever corrective measures are necessary to bring the moisture to a constant and uniform consistency before placing concrete. This may be accomplished by handling or mani pulating the stockpiles to reduce the moisture content, or by adding moisture to the stockpiles in a manner producing uniform moisture content through all portions of the stockpile. For plants equipped with an approved accurate mois ture-determining device capable of determining the free moisture in the aggregates, and provisions made for batch to batch correction of the amount of water and the weight of aggregates added, the requirements relative to manipulating the stockpiles for moisture control will be waived. Any procedure used will not relieve the producer of the responsibility for delivering concrete of uniform slump within the limits specified.

Provide separate means for storing ma terials approved by KDOT. If the producer elects to use KDOT Approved Materials for non-KDOT work, during the progress of a project requiring KDOT Approved Materials, inform the Engineer and agree to pay all costs for additional material testing. Clean all conveyors, bins and hoppers of any unapproved materials before beginning the manufacture of concrete for KDOT work. - GENERAL CONCRETE

401.5MORTAR AND GROUT

unless otherwise specified in the Contract Documents, including altering the proportions when a minimum strength is specified.

may contain admixtures, and is typically used to minimize erosion between large stones or to bond masonry units. Proportion mortar for laying stone for stone rip-rap, slope protection, stone ditch lining or pavement patching at 1 part of portland cement and 3 parts of FA-M aggregate by volume with sufficient water to make a workable and plastic mix. Proportion mortar for laying brick, concrete blocks or stone masonry at ½ part masonry cement, ½ part portland cement and 3 parts FA-M aggregate, either commercially produced masonry sand or FA-M, by volume with sufficient water to make a workable and plastic mix. Do not use air-entraining agents in mortar for masonry work. The Engineer may visually accept the sand used for mortar. The Engineer may visually accept any recognized brand of portland cement or masonry cement that is free of lumps.

which sufficient water is added to produce a pouring or pumping consistency without segregation of the constituent materials and meeting the applicable specifications.

401.6COMMERCIAL GRADE CONCRETE

If the Contract Documents allow the use of commercial grade concrete for designated items, then use a commercial grade mixture from a ready mix plant approved by the Engineer. The Engineer must approve the commercial grade c oncrete mixture. Approval of the commercial grade mixture is based on these conditions:  All materials are those normally used for the productio n and sale of concrete in the vicinity of the project.  The mixture produced is that normally used for the pr oduction and sale of concrete in the vicinity of the project.  The mixture produced contains a minimum cementitious content of 6 sacks (564 lbs) of cementitious material per cubic yard of concrete.  The water-cementitious ratio is as designated by the Engineer. The maximum water-cementitious ratio permitted may not exceed 0.50 pounds of water per pound of cementitious material including free water in the aggregate.  Type I, II, III, IP, IS or IT cement may be used unless otherwise designated. Fly ash, slag cement and blended supplemental materials may be substituted for the required minimum cement content as specified in subsection 401.3 . No additives other than air entraining agent will be allowed. The Contractor will not be required to furnish the results of strength tests when submitting mix design data to the Engineer.  In lieu of the above, approved mix designs (including optimized) for all other grades of concrete, Grade 3.0 or above, are allowable for use as commercial grade conc rete, at no additional cost to KDOT. Exercise good engineering judgment in determining what equipment is used in proportioning, mixing, transporting, placing, consolidating and finishing the concrete. Construct the items with the best curr ent industry practices and techniques. Before unloading at the site, prov ide a delivery ticket for each load of concrete containing the following information:  Name and location of the plant.  Time of batching concrete.  Mix proportions of concrete (or a mix designation approved by the Engineer).  Number of cubic yards of concrete batched. - GENERAL CONCRETE Cure the various items placed, as shown in DIVISION 700. The Engineer may test commercial grade concrete by molding sets of 3 cylinders. This is for informational purposes only. No slump or unit weight tests are required.

401.7CERTIFIED CONCRETE

If KDOT inspection forces are not available on a temporary basis, the Engineer may authorize the use of concrete from approved concrete plants. Approval for this operation is based on certification of the plant and plant personnel, according to KDOT standards. KDOT’s ap proval may be withdrawn an y time that certification procedures are not followed. Contact the DME for additional information. The Engineer will not authorize the use of certified co ncrete for major structures such as bridges, RCB box bridges, RCB culverts, permanent main line and ramp pavement or other structurally, critical items. Each load of certified concrete must be accompanied by a ticket listing mix proportions, time of batching and setting on revolution counter, total mixing revolutions and must be signed by certified plant personnel.

MIXING, DELIVERY AND PLACEMENT LIMITATIONS

mixer or in a drum mixer at the work site. Provide plant capacity and delivery capacity sufficient to maintain continuous delivery at the rate required. The delivery rate of concrete during concreting operations must provide for the proper handling, placing and finishing of the concrete. Seek the Engineer’s approval of the concrete plant/batch site before any concrete is produced for the project. The Engineer will inspect the equipment, the method of storing and handling of materials, the production procedures and the transportation and rate of delivery of concrete from the plant to the point of use. The Engineer will grant approval of the concrete plant/batch site based on compliance with the specified requirements. The Engineer may, at any time, rescind permission to use concrete from a previ ously approved concrete plan t/batch site upon failure to comply with the specified requirements. Clean the mixing drum before it is charged with the conc rete mixture. Charge the batch into the mixing drum such that a portion of the water is in the drum before the aggregates and cementitious material. Uniformly flow materials into the drum throughout the batching operation. All mixing water must be in the drum by the end of the first 15 seconds of the mixing cycle. Keep the throat of the drum free of accumulations restricting the flow of materials into the drum. Do not exceed the rated capacity (cubic yards shown on the manufacturer’s plate on the mixer) of the mixer when batching the concrete. The Engineer may allow an ove rload of up to 10% above the rated capacity for central mix plants and drum mixers at the work site, provided the concrete test data for strength, segregation and uniform consistency are satisfactory, and no concrete is spilled during the mixing cycle. Operate the mixing drum at the sp eed specified by the mixer’s manufacturer (shown on the manufacturer’s plate on the mixer). Mixing time is measured from the time all materials, ex cept water, are in the drum. If it is necessary to increase the mixing time to obtain the specified percent of air in air-entrained concrete, the Engineer will determine the mixing time. If the concrete is mixed in a central mix plant or a drum mixer at the work site, mix the batch between 1 to 5 minutes at mixing speed. Do not exceed the maximum to tal 60 mixing revolutions. Mi xing time begins after all materials, except water, are in the drum, and ends when the discharge chute opens. Transfer time in multiple drum mixers is included in mixing time. Mix time may be reduced for plants utilizing high performance mixing drums provided thoroughly mixed and uniform concrete is being produced with the proposed mix time. Performance of the plant must conform to Table A1.1 of ASTM C 94, Standard Specification for Ready Mixed Concrete. Five of the 6 tests listed in Table A1.1 must be within the limits of the specification to indicate that uniform concrete is being produced. If the concrete is mixed in a truck mixer, mix the batch between 70 and 100 revolutions of the drum or blades at mixing speed. After the mixing is completed, set the truck mixer drum at agitating speed. Unless the mixing unit is equipped with an accurate device indicati ng and controlling the number of revolutions at mixing speed, perform the mixing at the batch plant and operate the mixing unit at agitating speed while travelling from the plant to the work site. Do not exceed 300 total revolutions (mixing and agitating). An additional 60 mixing revolutions may be allowed by the Engineer when plasticizers are designated in the mix design. - GENERAL CONCRETE If a truck mixer or truck agitator is used to transport concrete that was completely mixed in a stationary central mixer, agitate the concrete while transporting at the agitating speed specified by the manufacturer of the equipment (shown on the manufacturer’s plate on the equi pment). Do not exceed 200 total revolutions (additional re-mixing and agitating). Provide a batch slip including batch weights of ever y constituent of the concrete and time for each batch of concrete delivered at the work site, issued at the batchi ng plant that bears the time of charging of the mixer drum with cementitious materials and aggregates. Include quantities, type, product name and manufacturer of all admixtures on the batch ticket. On paving projects and other high volume work, the Engineer will evaluate the haul time, and whether tickets will be collected for every load. Thereafter, random checks of the loads will be made. Maintain all batch tickets when not collected. When non-agitating equipment is us ed for transportation of concrete, place within 30 minutes of adding the cement to the water. Provide approved covers for protection against the weather when required by the Engineer. When agitating equipment is used for transportation of the concrete, place concrete within the time and temperature conditions shown in TABLE 401-5. TABLE 401-5: AMBIENT AIR TEMPERATURE AND AGITATED CONCRETE PLACEMENT TIME T = Ambient Air Temperature at Time of Batching (°F) Time limit agitated concrete must be placed within, after the addition of cement to water (hours) Admixtures T < 75 1 ½ None 75 ≤ T 1 None 75 ≤ T < 90 1 ½ Set Retarder In all cases, if the concrete temperature at time of placement is 90°F or above, or under conditions contributing to quick stiffeni ng of the concrete, place the concrete within 45 minutes of adding the cement to the water. Do not use concrete that has developed its initial set. Regardless of the speed of delivery and placement, the Engineer will suspend the concreting operations until correc tive measures are taken, if there is evidence that the concrete cannot be adequately consolidated. Weather conditions and the use of admixtures can affect the set times for the concrete. Do not use the time limits and total revolutions as the sole criterion for rejection of concrete. Exceed the time limits and total revolutions only after demonstrating that the properties of the concre te can be improved. Evaluation of the consistency and workability should be taken into consideration. Reject concrete that cannot be adequately consolidated. Adding water to concrete after the initial mixing is prohibited, with this exception: If the concrete is delivered to the work site in a truck mixer, the Engineer will allow water (up to 2 gallons per cubic yard) be withheld from the mixture at the batch site, and if needed, added at the work site to adjust the slump to the specified requirements. Determine the ne ed for additional water as soon as the load arrives at the construction site. Use a calibrated water-measuring device to add the water, and add the water to the entire load. Do not add more water than was withheld at the batch site. After the additio nal water is added, turn the drum or blades an additional 20 to 30 revolutions at mixing speed. The Engineer will supervise the adding of wate r to the load, and will allow this procedure only once per load. Conduct all testing for acceptance and produce any required cylinders after all water or admixtures have been added. Do not add water at the work site if the slump is within the designated slump tolerance, even if water was withheld. Do not add water at the work site if the percent air is above 8%, regardless of the slump, even if water was withheld. Do not withhold and add water if plasticizer is added to the concrete mixture at the batch site. If at any time during the placement of concrete it is determined that redosing with water is adversely affecting the properties of the concrete, the concrete will be rejected and the Engineer will suspend the practice.

an adequate, artificial lighting system approved by the Engineer is provided. - GENERAL CONCRETE

concreting operations when the descen ding ambient air temperature reaches 40°F. Do not begin concreting operations until an ascending ambient air temperature reaches 35°F and is expected to exceed 40ºF. If the Engineer permits placing concrete during cold w eather, aggregates may be h eated by either steam or dry heat system before placing them in the mixer. Use an apparatus that heats the mass uniformly and is so arranged as to preclude the possible occurrence of overheated areas which might injure the materials. Do not heat aggregates directly by gas or oil flame or on sheet metal over fire. Aggregates that are heated in bins, by steam-coil or water- coil heating, or by other methods not detrimental to the aggregates may be used. The use of live steam on or through binned aggregates is prohibited. Unless otherw ise authorized, maintain the temperature of the mixed concrete between 50 to 90°F at the time of placing. Do not, under any circumstances, continue concrete operations if the ambient air temperature is less than 20°F. If the ambient air temperature is 35°F or less at the time the concrete is placed, the Engineer may require that the water and the aggregates be heated to between 70 and 150°F. Do not place concrete on frozen subgrade or use frozen aggregates in the concrete. Make adjustments for potential longer set time and slower strength gain for concrete with SCMs. Adjust minimum time requirements as stated in SECTION 710 for concrete used in structures. For concrete paving, be aware of the effect that the use of SCMs (except silica fume) may have on the statistics and moving averages.

401.9INSPECTION AND TESTING

Unless otherwise designated in the Contract Documents or by the Engineer, obtain samples of fresh concrete for the determination of slump, weight per cubic yard and percent of air from the final point of placement. The Engineer will cast, store and test strength test specimens in sets of 3. KDOT will conduct the sampling and test the samples according to DIVISION 2500 and the Sampling and Testing Frequency Chart in Part V. For QC/QA contracts, establish testing intervals within the specified minimum frequency. The Engineer will reject concrete that does not comply with specified requirements. The Engineer will permit occasional deviations below th e specified cementitious content, if it is due to the air content of the concrete exceeding the designated air c ontent, but only up to the maximum tolerance in the air content. Continuous operation below the specified cementitious content for any reason is prohibited. As the work progresses, the Engineer reserves the righ t to require the Contractor to change the proportions if conditions warrant such changes to produce a satisfactory mix. Any such changes may be made within the limits of the specifications at no additional compensation to the Contractor. - GENERAL CONCRETE APPENDIX A – NON-MANDATORY INFORMATION GENERAL CONCRETE Design general concrete according to TABLE 401-A1 meeting the applicable requirements for Volume of Permeable Voids, Surface Resistivity, or Rapid Chloride Permeability as required in subsection 401.3h. TABLE 401-A1: GENERAL CONCRETE Grade of Concrete lb. of Cementitious per yd of Concrete, minimum lb. of Water per lb. of Cementitious, maximum Grade 7.0(**):MA Gradation 700 0.35 Grade 6.0(**):MA Gradation 650 0.35 Grade 5.0(**):MA Gradation 602 0.35 Grade 4.5(**):MA Gradation 602 0.40 Grade 4.0(**):MA Gradation 602 0.44 Grade 3.5 and 3.0(**):MA Gradation 564 0.46 Grade 2.5(**):MA Gradation 526 0.50 General Concrete (*) (**) *Grade as specified in the Contract Documents **Air Entrained meeting subsection 401.3a. Air entrained concrete with a target air of 6.5 ± 1.5 percent. Maximum water to cementitious ratio of 0.50 and a minimum cementitious content of 480 lbs per cubic yard. Maximum limit of lb. of water per lb. of cementitious material includes free water in aggregates, but excludes water of absorption of the aggregates. - GENERAL CONCRETE APPENDIX B – NON-MANDATORY INFORMATION SUGGESTED GUIDELINES FOR MEETING KDOT’S PERMEABILITY SPECIFICATIONS General: Water and chlorides permeate through the mortar and paste of the concrete mixes. They do not readily permeate through the larger aggregates. Permeability can be improved by decreasing the mortar and paste of the concrete mix and increasing the coarse aggregate portions. The use of optimized mix designs, blended cements, and/or supplementary cementitious materials (SCMs) can reduce the permeability of concrete. SECTIONS 1102 and 1116, Aggregates for Concrete describes optimized aggregate gradations for concrete mixes. Additional tes ting for alkali silica reaction (ASR) is required when SCMs are used in concrete as per SECTION 401. The amount of SCMs required to pass the ASR testing may be different than the amount required to comply with the permeability specifications. SCMs may also lower the necessary water cement (w/c) ratio and may slow set times and strength gain. Optimizing the coarse aggregate gradations can decrease permeability. This includes mixes with more than 60% retained on the # 8 sieve and gradations with fineness modulus above 4.75. A fineness modulus of over 5.0 can yield even better results. Use the largest practical nominal maximum size aggregate allowed. In general, keeping the w/c ratio below 0.43 may help meet the permeability specifications, as may lower cementitious content mixes when using Type I/II cements. These two properties control the paste in the mix. Concrete mixes with less than 25% paste (as displayed on KDOT Form 694) are more likely to pass the permeability specifications. Acceptable concrete can be mixed with past e contents of 23% or lower. Water cement ratios below 0.39 often do not provide enough wate r for all constituents to properly react, especially when admixtures are used, and may be counterproductive. High early strength conc rete mixes using Type III cement and higher cementitious contents have also beenable to pass the Standard Permeability requirements because of their low w/c ratios. In general, the use of water reducers is helpful in reducing the paste content. Material compatibilities, following the admixture suppliers’ recommendations for dosage rates, and the order of introduction of the chemicals into the mix are paramount to meeting KDOT specifications. Contractors should work with their admixture suppliers to find an admixture that works well with their combination of materials. Changes made to an approved mix design will change the permeability, especially additional water, or redosing water that was withheld from the mix at a concrete plant. It is also recommended that concrete producers verify their mixes with a minimum of 3 cubic yards after doing their laboratory mix designs. Standard Permeability Concrete (SPC) Requirements: Volume of Permeable Voids 12.0% max, or Surface Resistivity 9.0 kΩ-cm min, or RCPT 3000 Coulombs max. The SPC requirements may be met without the use of optimized mix designs, blended cements or SCMs. With certain aggregates, 25% slag cement will be required to pass the ASR testing. With other aggregates, a minimum of 30% slag cement by weight of total cementitious materials is usually needed. Some fly ashes require a minimum of 18% to 20% of the total cementitious material to pass the ASR test. Class C fly ash will react differently than Class F fly ash. Some people believe that lower absorption aggregates have a better chance of meeting the permeability specification, but higher absorption aggregates have been used in concrete mixes utilizing these guidelines and have met the SPC specifications. KDOT has found that the properties of the concrete are often more important than the absorption of the aggregate when meeting this specification. Moderate Permeability Concrete (MPC) Requirements: Volume of Permeable Voids 11.0% max, or Surface Resistivity 13.0 kΩ-cm min, or RCPT 2000 Coulombs max. Concrete mixes for MPC will require aggregates with a minimum Soundness of 0.95, a maximum LA Wear of 40, and a minimum Acid Insoluble Residue of 85%. These aggregates, by nature, are harder aggregates with very low absorption. MPC may rely more heavily on optimized gradations, blended cements or SCMs in order to meet the specification. Consideration could be given to ternary blends of cementitious materials, using more than one - GENERAL CONCRETE SCM, or combining a blended cement with an additional SCM. Combinations of 25% to 30% slag cement with as little as 10% to 25% Class C fly ash have been very effective in keeping permeabilities below the level required for MPC. Incorporation of 20% Class F Fly Ash will often satisfy the requirements of the MPC specification. Low Permeability Concrete (LPC) Requirements: Volume of Permeable Voids 9.5% max, or Surface Resistivity 27.0 kΩ-cm min, or RCPT 1000 Coulombs max. LPC will also use harder aggregates with very low absorption. These mixes must be optimized with the MA-6 gradation. Mix designs with 5% silica fume and 95% Type I/II cement often meet the LPC requirements. These mixes have traditionally been known as silica fume concrete. Ternary mix designs are useful in meeting these requirements. Consider using 3% to 5% silica fume with 25% to 30% slag cement, or 25% to 30% slag cements with 10% to 25% Class C fly ash. Class F fly ash alone may also be effective in reducing the permeability to these levels. Contact KDOT’s Bureau of Research or the Distri ct Office for additional guidance in meeting the Permeability Specifications.