601.3For the mix design using potent ially reactive aggregates select the level of

481 623.3.2 -Quality Control Personnel: Shotcrete Inspector: Every project in which shotcrete is included is required to have an independent Shotcrete Inspector with a current ACI Shotcrete Inspector Certification. The Shotcrete Inspector must have verifiable work experience in one of the follow ing areas: 1. Testing, inspection, and quality control of shotcrete. 2. Supervision of shotcrete construction work. 3. Design of shotcrete structures. The Shotcrete Inspector is required to be at the place of shotcrete placement while shotcrete placement i s occurring. 623.4 -PROPORTIONING : Unless otherwise specified, the proportioning and mix design of shotcrete shall conform to Section 601.3. For the mix design using potent ially reactive aggregates select the level of prevention of Class B concrete in Table 601.3.1.1.1.3. At least 30 calendar days prior to the start of construction, the Contractor shall design and submit, to the Engineer, for approval, the proportions of ma terials, including cement, aggregate, admixtures, fibers, and supplementary cementitious materials, to be used which will result in a mixture conducive to effective shotcreting, and a mixture having the desired properties. A mix design shall be required fo r each different type of shotcrete to be used in the work. The mix design shall be accompanied by a statement giving the source of materials and components used in the mix. All shotcrete mix designs will be accepted based on the results of preconstruction testing. When using the wet -mix process the air content of the concrete must be 7 ± 1% before shooting. Dry-mix shotcrete may be used provided that the in -place air entrainment shall be checked at least once at the beginning of the operation, once in th e middle, and once after restarting the shotcrete process after any breaks each day and found that the in -place mixture has a of 4 ± 1%% air entrainment. The maximum allowable w/c ratio for any shotcrete mix design will be 0.45. Shotcrete shall achieve a minimum compressive strength of 2000 psi in 3 -days and 4000 psi in 28 -days when tested using cores in accordance with ASTM C1140. Compressive strength and plastic air content test results from at least one test panel for each mix design shall be submitte d to the Engineer prior to construction. 623.5 -PRE -CONSTRUCTION TESTING : Prior to the start of construction, the contractor will shoot qualifying test panels. At a minimum, two panels will be shot for every different mix design that is going to be used on the project. Additional test panels may be required at the discretion of the Engineer. The same ACI certified nozzleman, crew, and equipment that will be performing shotcreting operations on the project must be used to shoot the test panels. If during construction the nozzleman is changed, the new nozzleman will be required to shoot additional test panels prior to beginning work. The same shooting positions that will be used in the project must be used in shooting the test panels. All form materials and procedures will comply with ASTM C1140. One of these two test panels will have reinforcement which is the same as the most congested section on the shotcrete project and shall use the same mix design designated for that section of the project. The finish that is selected for the section of the project, which the panel with reinforcement represents, will be applied to the panel with reinforcement, to indicate whether that finish has any effect on the shotcrete encasement around the reinforcement. This will be used to qualify the nozzleman and shotcreting feasibility. The m inimum diameter for the cores taken from the panel with reinforcement will be 3.75 -inches and will be the entire thickness of the panel. The panel with reinforcement will be large enough so that actual project conditions can be 482 simulated. The other panel will have no reinforcement and will be used to qualify the properties of the mix design. The size of the panel without reinforcement, for qualifying the mix design, will be such so that cores can be drilled allowing for three ( 3)-inches diameter and lengt h of 5.5 -inches or the thickness of the panel, whichever is greater. This process shall follow the guidelines of ASTM C1604. A WVDOH representative and the Shotcrete Inspector must be present when the test panels are constructed and tested, and the WVDOH representative and the Shotcrete Inspector must inspect the performance of the test panels with reinforcement for quality of shotcrete placement, quality of nozzleman, and encasement. Three cores shall be taken from the test panel with reinforcement and will be visually inspected to ensure proper shotcrete placement and consolidation around the reinforcement. Three cores shall be taken from the test panel without reinforcement and will be tested in accordance with ASTM C1604. Cores that are damaged fro m drilling must be immediately discarded. If any preconstruction testing panel fails the contractor will be allowed to shoot another test panel with the same nozzleman, equipment, and mix design. If the second panel also fails, the contractor must make ch anges until the shotcrete panel passes the testing. These changes must be implemented during the entire shotcreting process during construction. If permitted by the Engineer on small projects, where preconstruction testing is cost prohibitive, the requir ement for constructing test panels may be waived if the contractor provides results of previous tests with the same nozzleman, materials, mix designs, qualified personnel, and similar project application. The requests must be made to the Engineer and appro ved before pre - construction testing may be omitted. A site on the project must be selected by the engineer to perform a tensile bond strength test between the original concrete, which will be repaired, and the new layer of concrete placed with shotcrete. The contractor will repair the selected site and after curing, a minimum of three tests will be performed following the guidelines of ASTM C1583 (Standard Test Method for Tensile Strength of Concrete Surfaces and the Bond Strength or Tensile Strength of C oncrete Repair and Overlay Materials by Direct Tension (Pull -off Method))The minimum bond strength which the average of the three tests shall meet is 150 psi. If the average of the three tests do not meet this bond strength requirement then changes should be made to mix design, or methods to ensure the specified bond strength. 623.6 -TESTING DURING CONSTRUCTION : The Contractor must notify the Engineer at least 48 hours prior to beginning any shotcreting operations. The Contractor shall perform Quality Control Testing as outlined in this sub -section. 623.6.1 -Sampling and Testing Methods: Sampling Materials for Shotcrete ASTM C1385 Temperature of Freshly Mixed Hydraulic Cement Concrete ASTM C1064 Testing of Air Content ASTM C231 or AASHTO T 152 Preparing and Testing Specimens from Shotcrete Test Panels ASTM C1140 Obtaining and Testing Drilled Cores of Shotcrete ASTM C1604 623.6.2 -Temperature : Testing of the temperature will be performed hourly and shall be within the allowable temperature ranges specified in Section 601.9. 623.6.3 -Air Content : For wet -mix shotcrete, the air content must be 7 ± 1% when tested prior to placement. The testing frequencies of air content for wet -mix shotcrete, prior to placement, will be as required in MP 601.03.50 Table 1 Section C. A, “as shot shotcrete”, air test shall be performed one per ½ day of operation for both wet - mix and dry -mix shotcrete as follows. The shotcrete nozzleman will shoot a sample of shotcrete into a wheelbarrow or at the wall or floor, then place the shotcrete sample into the air meter using a scoop. The subsequent sample will follow guidelines of ASTM C231 or AASHTO T 152. The air entrainment of the “as shot shotcrete” will be 4.0 ± 1%. 623.6.4 -Compressive Strength : During construction, test panels shall be shot for each different mi x in the project. The panels will have a minimum dimension of sixteen ( 16) inches x sixteen ( 16) inches and have enough depth to allow cores to be 5.5 -inches long. One test panel will be shot for each mix every day or every 50 yd³, whichever produces the greatest number of panels. The panels will then be cured using the procedures in ASTM C1140. Three cores with a diameter of three ( 3) inches and a length of 5.5 - inches will obtained from each panel and tested for compressive strength following the guidel ines of ASTM C1604. The minimum 28 -day average compressive strength for each set of cores from each panel shall be 3,500 psi with no single core strength less than 3,000 psi. When testing in -place concrete that has been placed using shotcrete, cores will be obtained at the location specified by the Engineer and tested as outlined in ASTM C1604. 623.6.5 -Combined Aggregate Gradation: The aggregate gradation shall be performed by the contractor once for every 50 cubic yards of shotcrete that is produ ced from the same mix design. The aggregate gradation shall meet the requirements of Table 623.2 . However, not more than one aggregate gradation test (for each mix design) shall be required per calendar day as long as not more than 400 cubic yards of shotc rete is produced in a single day from the same mix design. In situations when more than 400 cubic yards of shotcrete is produced in a single day from the same mix design, two aggregate gradation tests shall be required (one in the AM and one in the PM) for that mix design. During any calendar week (Sunday through Saturday) in which shotcrete is being produced, a minimum of one aggregate gradation test shall be required (for each mix design from which shotcrete is being produced). This aggregate grada tion test shall be conducted on the first day of production of that calendar week. Should the aggregate gradation tests results for any sieve size listed be outside of the limits set forth in Table 623.2 then production shall be discontinued until approp riate corrections are made. Corrections shall be made either in the aggregate proportions in the shotcrete mix (the mix design), the gradation of the aggregates, or the storage and loading of the aggregate, as the Contractor may elect. When the small qua ntity work condition applies, the aggregate gradation test required after 50 cubic yards of shotcrete production shall be performed on the day that the 50 cubic yard quantity is achieved. All shotcrete produced on that day (the day that the 50 cubic yard q uantity is achieved) shall be represented by the previous aggregate aggradation test. The aggregate gradation test conducted on the day that the 50 cubic yard quantity is achieved shall represent the next 50 cubic yards of shotcrete produced, beginning wit h the shotcrete produced on the next day of production. 484 623.7 -EQUIPMENT AND TOOLS : The Contractor shall maintain a clean, dry, oil -free supply of compressed air sufficient for maintaining adequate nozzle velocity at all times. The equipment shall be capable of delivering the premixed material accurately, uniformly and continuously throug h the delivery hose. To prevent sagging or sloughing of freshly -applied shotcrete, control must be taken with the application thickness, nozzle technique, air pressure and rate of shotcrete placement. A minimum 600 CFM compressor capable of producing 120 p si air pressure exiting the compressor is required. The internal diameter of the hose shall be at least three times larger than the largest particle in the mixture. For shotcrete containing steel fiber -reinforcement, the internal hose diameter shall be a minimum of 1.5 times the length of the fiber, and for shotcrete containing synthetic fibers, the internal hose diameter shall be a minimum of the same length as the fiber. For all dry -mix applications, a water booster pump must be included in the system adding water to the application. 623.8 -HANDLING, MEASURING AND BATCHING OF MATERIAL S: The batch aggregate and cement by weight or by volume must be in accordance with the requirements of Section 601 and AASHTO M 157 or ASTM C685. The mixing equipment must thoroughly blend the materials in sufficient quantity to maintain placing continuity. The batch, delivery and placement of shotcrete must b e completed within 90 minutes of mixing. The use of retarding admixtures may extend application time beyond 90 minutes if approved by the Engineer. Dry-mix shotcrete shall be sufficiently damp prior to shotcreting. Site -batched dry -mix shotcrete typical ly does not need to be pre -dampened, since the aggregate usually contains sufficient moisture. However, pre -bagged dry -mix shotcrete must be pre -dampened. 623.9 -CLEANING : All su rfaces must be free from damaged material. The surfaces must be clean from dirt, oil, or other contaminants that could inhibit the bond of shotcrete. Concrete or masonry surfaces will be chipped prior to the placement of shotcrete to make surfaces even, sa wcut surfaces must be roughened. In concrete repair work, disintegrated concrete shall first be removed with pneumatic or hand tools. The surfaces shall then be thoroughly blasted to remove all dirt and loose materials, special care being taken in concre te repair work to thoroughly clean exposed reinforcing steel. Any unsound concrete, on which shotcrete will be placed, shall be removed. Prior to applying each layer of shotcrete, the concrete surfaces shall be cleaned and washed with water and dried to a saturated surface dry condition with compressed air. Earth surfaces shall be dug to line and grade. The surface will be dampened prior to the placement of shotcrete. There will be no pools of standing water prior to the shooting of shotcrete.