of compressive strengths within a set of three cylinders is 9.5%. This range is found by multiplying 9.5% times the average compressive strength of the three cylinders. If this acceptable range is exceeded, the cylinder that varies the most from the average shall be discarded, and the remaining two cylinders shall be evaluated as outlined in the following paragraph. The maximum acceptable range of compressive strengths within a set of two cylinders is 8.0%. This range is found by multiplying 8.0% times the average compressive strength of the two cylinders. If this acceptable range is e xceeded, the entire test shall be discarded. Under no circumstances shall a compressive strength test consist of less than the average of two specimens. Compressive strength tests shall conform to the requirements of Table 501.3.1. Statistical analysis may indicate a percentage of production to be below nominal minimum design strength. Concrete represented by compressive strengths below the nominal design strength of Table 501.3.1 may be removed and replaced by the Contractor. If the Contractor elects to leave the material in place, it will be evaluated as to adequacy for the use intended. All concrete evaluated as unsatisfactory for the use intended shall be removed and replaced or otherwise corrected by and at the expense of the Contractor as required in 105.3. When an evaluation indicates that the work may satisfactorily remain in place, a statistical analysis will be made of the material. If this statistical analysis indicates at least 93 percent (93%) of the material may be expected to have comp ressive strengths equal to or greater than that shown in Table 501.3.1, and 99.87 percent (99.87%) of the material may be expected to have compressive strengths at least one standard deviation above forty percent (40%) of the design strength (0.4f' c+σ), th e work will be accepted as substantially complying with the specification requirements. If this statistical analysis indicates that less than 93 percent (93%) of the material may be expected to have compressive strengths equal to or greater than that show n in Table 501.3.1 or less than
99.87percent (99.87%) of the material may be expected to have compressive strengths at least
one standard deviation above forty percent of the design strength (0.4f' c+σ), the Engineer will provide for an appropriate adjustm ent under the provisions of 601.15. Whenever possible, the Division's statistical analysis will be based on a minimum of 10 cylinder test results. These results may be from the concrete item being placed, the same class of concrete on the project, or th e same class of concrete from the producer. All of the cylinder test results used in this evaluation, however, must be from the same mix design.
501.5 -EQUIPMENT AND TOOLS : Equipment and tools necessary for handling materials and performing all parts of the work shall be approved by the Engineer as to design, capacity, and mechanical condition. The equipments hall be at the job site sufficiently ahead of the start of construction operations to be examined. Any equipment not maintained in satisfactory working order, or which is proved inadequate, shall be improved or new equipment substituted, as directed by th e Engineer.
501.5.1 -Field Laboratory: Portland cement concrete shall be supplied by a plant which has been certified by the Division as meeting all requirements of the governing Specifications and as having the facilities necessary to ascertain and con trol the quality of the product in accordance therewith. A testing facility or laboratory, as described below, shall be provided within reasonable proximity of the concrete batch patch. The laboratory shall have inside dimensions which provide a minimu m working area of twenty -six (26) feet in length by six (6) feet in width (examples which would generally meet
236 this requirement are a building with inside dimensions of twelve ( 12) by thirteen ( 13) feet, or a trailer with dimensions of eight ( 8) by thirty (30) feet.). The laboratory shall be furnished and maintained with adequate ventilation, heat, light, water, sinks and drainage, electrical or gas outlets, or both, work table, shelves, and supply cabinets. The laboratory shall be supplied with the equi pment and materials listed below and shall be maintained in such a condition that the equipment will meet the applicable requirement of ASTM or AASHTO.
ii. Large oven, gas or electric. iii. Pressure air meter or volumetric air meter (Rollameter). iv. Slump cone and rod.
vi. Solution balance, 20 kg. capacity, one gram increments. vii. Balance, minimum capacity 1,000 g., 0.1 g. increments. viii. Platform scale, 100 kg. capac ity, 10 g. increments. ix. Thermometer, armored type.
xi. Ro-Tap shaker or equivalent, with eight ( 8) inch round screens. xii. Wire basket and container for weighing aggregates under water. xiii. Sample splitters for fine and coarse aggregates. xiv. Equipment for determining specific gravity of sand. xv. Miscellaneous items (including rubber hammer, mason's trowels, approximate dimensions four ( 4) inch and eight ( 8) inch square point shovel , small and large sugar scoops, heavy galvanized pail approximate 14 qt. capacity, aggregate sample pans, brushes, flashlight, glassware, steel straightedge approximate dimensions eighteen
to be made. xvi. “Speedy Moisture Tester”, 20 g. or 26 g. capacity.
501.5.2 -Batching Plant Equipment: 501.5.2 .1-General: The batching plant shall include bins, weighing hoppers, and scales for the fine aggregate and for each size of coarse aggregate. If cement is used in bulk, a separate bin, hopper, and scale for cement shall be included. The weighing hopper shall be pro perly sealed and vented to preclude dusting during operation. If fly ash is used in the concrete, a separate bin shall be included.
501.5.2 .2-Bins and Hoppers: Bins with adequate separate compartments for fine aggregate and for each size of coarse aggr egate shall be provided in the batching plant.
501.5.2 .3-Scales: The scales for weighing aggregates and cement shall conform to the requirements of 109.1. Scales shall be inspected and sealed as often as the Engineer deems necessary to ensure their con tinued accuracy, and as outlined in MP700.00.30. The Contractor shall have on hand not less than ten 50 pound test weights for frequent testing of all scales. Batching plants equipped to proportion aggregates and bulk cement by means of automatic weighing devices may be used.
237 501.5.2 .4-Water Measuring Equipment: Unless the water is weighed, the water measuring equipment shall include an auxiliary tank from which the measuring tank shall be filled. The measuring tank shall be equipped with an outside ta p and valve to provide for checking the setting, unless other means are provided for readily and accurately determining the amount of water in the tank. The volume of the auxiliary tank shall be at least equal to that of the measuring tank.
501.5.2 .5-Admixture Dispenser: A positive, automatic mechanical method shall be used for adding admixtures in solution.
501.5.3 -Mixers and Hauling Equipment: 501.5.3 .1-General: Mixers at the site of construction or at central point, truck mixers, and hauling equipment shall conform to the requirements specified. Each mixer shall have attached in a prominent place a manufacturer's plate showing the capacity of the drum in terms of volume of mixed concrete and the speed of rotation of the mixing drum or blades.
501.5.3 .2-Mixers: Mixing shall be in a mixer capable of combining the aggregates, cement, and water into a thoroughly mixed and uniform mass within the specified mixing period. The mixer shall be equipped with a timing device which will automatically lock the discharge level when the drum has been charged and release it at the end of the mixing period. The device shall be equipped with a bell or other suitable warning device adjusted to give a clearly audible signal each time the lock is released. In case of failure of the timing device, the mixer may be used for the balance of the day while it is being repaired. The mixers shall be cleaned at suitable intervals. The pickup and throw -over blades in the drum or drums shall be repaired or replaced when they are worn down 3/4 in ches or more. The Contractor shall (1) have available at the job site a copy of the manufacturer's design showing dimensions and arrangements of blades in reference to original height and depth, or (2) provide permanent marks on blades to show points of 3/4 in ches wear from new conditions. (Holes of 1/4 in ches diameter near each end and at a midpoint of each blade are recommended.)
501.5.3 .3-Truck Mixers and Truck Agitators: Truck mixers used for mixing and hauling concrete, and truck agitators used for hauling central -mixed concrete, shall conform to the requirements of AASHTO M 157.
501.5.3 .4-Nonagitator Trucks: Bodies of nonagitating hauling equipment for concrete shall be smooth, mortar tight, metal containers and shall be capable of discharging the concrete at a satisfactorily controlled rate without segregation. The concrete shall be discharged from the bottom of the c ontainer. If discharge of concrete is accomplished by tilting the body, the surface of the load shall be retarded by a suitable baffle. Covers shall be provided when needed for protection.
501.5.4 -Finishing Machine: The finishing machine shall be des igned and operated to strike off, consolidate, and obtain a smooth finish. The top of the forms, if used, shall be kept free from accumulation by an effective device attached to the machine, and the travel of the machine on the forms shall be maintained t rue.
238 501.5.5 -Vibrators: For full width vibration of concrete paving slabs, vibrators may be either the surface pan type or the internal type with either immersed tube or multiple spuds. They may be attached to the spreader or the finishing machine, or may be mounted on a separate carriage. They shall not come in contact with the joint, load transfer devices, subgrade, or side forms. The frequency of the surface vibrators shall not be less than 3,500 impulses per minute, and the frequency of the inter nal type shall not be less than 5,000 impulses per minute for tube vibrators and shall be between 5,000 and 10,000 impulses per minute for spud vibrators. When spud type internal vibrators, either hand operated or attached to spreaders or finishing machi nes, are used adjacent to forms, they shall have a frequency of not less than 3,500 impulses per minute. Other types of vibrators may be used when shown they perform the function intended.
501.5.6 -Concrete Saw: When sawing joints is elected or specif ied, the Contractor shall provide sawing equipment, adequate in number of units and power to complete the sawing to the required dimensions and at the required rate for preventing uncontrolled cracking. A standby saw and ample supply of saw blades shall b e maintained at the site of the work at all times during sawing operations. The Contractor shall provide adequate artificial lighting facilities for night sawing. All of this equipment shall be on the job both before and continuously during concrete pavement.
501.5.7 -Forms: Straight side forms shall be of adequate design to support the paving train and to provide the proper pavement section without horizontal joints. Flexible or curved forms of proper radius shall be used for curves of 200 -feet radius or less. Flexible or curved forms shall be of a design acceptable to the Engineer. Forms shall be provided with adequate devices for secure setting and shall have an attachment provision for forming the keyed joint between lanes. When in place they sh all withstand, without visible springing or settlement, the impact and vibration of consolidating and finishing equipment. Forms with battered top surfaces, and bent, twisted, or broken forms shall be removed from the job. The top face of the forms shall not vary from a true plane more than 5/8 in ch in ten (10) feet, and the upstanding leg shall not vary more than ¼ in ch from a plane normal to the subgrade. The forms shall contain provisions for locking the ends of abutting form sections together tightly, and for secure setting.
501.5.8 -Edging Tools: Edging tools shall have ¼ in ch radius for all edges except outside edges, which shall have a ¾ in ch radius.
501.6 -PREPARATION OF GRADE, SETTING FORMS, AND CONDITIONING OF SUBGRADE OR BASE : 501.6.1 -Preparation of Grade: After the roadbed has been graded and compacted, as provided in 207 or 228, the grade shall be trimmed approximately to correct elevation, extending the work at least two ( 2) feet beyond each edge of the proposed concrete pavement to provide support for the fixed -forms or the slip -form paver tracks.
501.6.2 -Setting Forms: 501.6.2 .1-Base Support: The foundation under the forms shall be hard and true to grade so that the form, when set, will be firmly in contact for its whole length and at the specified grade. Any grade which at the form line is found below established grade shall be filled to grade with granular material, in lifts of ½ in ch or less for a distance of eighteen
239 (18) inches on each side of the base of the form, and thoroughly compacted. Imperfections or variations above grade shall be corrected by tamping or by cutting as necessary.
501.6.2 .2-Form Setting: Forms shall be set sufficiently in advance of the point where concret e is being placed. After the forms have been set to correct grade, the grade shall be thoroughly tamped, mechanically or by hand, at both the inside and outside edges of the base of the forms. Form sections shall be tightly locked, free from play or movement in any direction. The forms shall not deviate from true line by more than ¼ in ch at any point. Excessive settlement or springing of forms under the finishing machine will not be tolerated. Forms shall be cleaned and oiled prior to the placing of co ncrete.
501.6.2 .3-Grade and Alignment: The alignment and grade elevations of the forms shall be checked and corrections made by the Contractor prior to placing the concrete. When any form has been disturbed or any grade has become unstable, the form sh all be reset and rechecked.
501.6.3 -Conditioning of Subgrade or Base: The base shall be brought to the proper cross section and plan grade within the tolerances specified for the final course underlying the pavement. The finished grade shall be mainta ined in a smooth and compacted condition until the pavement is placed. The grade shall be constructed sufficiently in advance of the paver to prevent delays. Unless waterproof subgrade or base course cover material is specified, the subgrade or base course shall be uniformly moist when the concrete is placed.
501.6.3.1 -Conditioning of Surfaces Receiving an Unbonded Concrete Overlay: If required, the bond breaker/leveling course for unbonded concrete overlays shall be constructed as shown on the Plans. Construct any specified hot -mix asphalt base, bond breaker, or patching and leveling course in accordance with Section 401. Remove a ll loose materials from the existing pavement prior to placing the asphalt. If required on the Plans, mill the surface before concrete placement in accordance with Prior to placement of the overlay, the milled surface shall be swept clean. The Engineer shall be notified if milling operations expose underlying concrete pavement. All areas where the underlying concrete pavement is exposed shall be repaired, regardless of size. The Contractor shall first determine, in the presence of the Engineer, if the remaining asphalt surrounding the area of exposed concrete is sound. This asphalt shall be considered sound if it cannot be easily removed by prying it loose with a shovel. If it can be easily removed in such a manner, the Contractor shall continue to remove all such unsound asphalt until sound asphalt is encountered. If the asphalt surrounding the exposed concrete area is less than two ( 2) inches thick, greater than 50 square feet or are wider than six (6) feet in the transverse direction, spray exposed concrete with tack coat meeting the requirements of Section 408 and cover with engineering fabric meeting the requirements of Section 715.1 1.8. If the asphalt surrounding the exposed concrete area is two ( 2) inches or more in thickness, repair the exposed concrete area with an asphalt patch of the same thickness as the surrounding asphalt with either a Base -II or 19 mm mix in accordance with Section 401.