570.10 Method of Measurement.
570.10 Method of Measurement.
The Soil Nail Wall will be measured in units of square yards of the shotcrete face of the wall. Measurement will not be made outside of the limits (vertical and horizontal) of the shotcrete face of the wall shown on the plans or designated by the Engineer. Excavation for Construction of Soil Nail Wall will be measured as the theoretical volume in cubic yards wit hin the structure excavation limits shown on the Plans. This will be the excavation volume within the zone measured from the top of the shotcrete wall facing to the bottom of the wall. There will be no measurement of the excavation beyond the limits of exc avation shown on the Plans.
570.11 Basis of Payment.
a.Unit Price Coverage. The Soil Nail Wall will be paid for at the contract unit price. This payment shall be full compensation for all submittals, labor, equipment, tools, materials, material tests, f ield tests and incidentals necessary to acceptably fabricate and test the wall components and construct the wall. This shall also be full compensation for furnishing and placing the reinforcing steel for the wall facing. The contract unit price for Excava tion for Soil Nail Wall shall be full compensation for all equipment, tools and labor required for the excavation and disposal of the excavated materials.
b.Payment will be made under Item No.: 570-A Soil Nail Wall – per square yard 570-B Excavat ion for Soil Nail Wall – per cubic yard 570-C Temporary Soil Nail Wall – per square yard
571.01 Description.
This work shall consist of furnishing and placing one or more courses of shotcrete and reinforcing steel on a prepared surface. The shotcrete shall be a concrete mixture that is pneumatically projected at high velocity onto the surface.
571.02 Materials.
a.General. Materials shall conform to the requirements given in Division 800, Material s. Specific reference is made to applicable portions of the following Sections: Section 801 Coarse Aggregate Section 802 Fine Aggregates Section 806 Mineral Admixtures Section 807 Water Section 808 Air Entraining Admixtures Section 809 Chemical Admixtures for Concrete Section 815 Cement Section 835 Steel Reinforcement Section 852 Underdrain Pipe Materials
b.Aggregates. When coarse aggregates are used, the coarse and fine aggregate shall be weighed separately to avoid segregati on. Oversize pieces of aggregate shall be removed by screening. The combined aggregates shall meet one of the following gradations:
571.02 Materials.
GRADATIONS FOR COMBINED AGGREGATES FOR SHOTCRETE SIEVE SIZE PERCENT BY WEIGHT PASSING INDIVIDUAL SEIVES GRADATION No. 1 GRADATION No. 2 3/4 inch -- -- 1/2 inch -- 100 3/8 inch 100 90 – 100 No. 4 95 – 100 70 – 85 No. 8 80 – 100 50 – 70 No. 16 50 – 85 35 – 55 No. 30 25 – 60 20 -35 No. 50 10 – 30 8 – 20 No. 100 2 – 10 2 – 10
c.Shotcrete Mix Design. The Contractor shall design the shotcrete mix and shall verify the performance of the design of the mix by trial mixes and laboratory tests. The Contractor shall submit the proposed mix design and test results to the Materials and Tests Engineer. The placement of the shotcrete shall not begin until the mix design is approved through field placement tests and compressive strength testing described in Article 571.03. Type I or Type III cement shall be used. The type and dosage of mineral and chemical admixture, if proposed for use, shall be included in the mix design, verification mixes, and production mix. The design, verification, and production of shotcrete mixes shall result in the shotcrete having the following properties: PHYSICAL PROPERTIES OF SHOTCRETE TYPE OF PLACEMENT PROCESS MINIMUM CEMENTITOUS MATERIAL CONTENT (POUNDS PER CUBIC YARD MAXIMUM WATER - CEMENTITOUS MATERIAL RATIO (W/C) (1) AIR CONTENT RANGE, EA(2) ( % ) MINIMUM COMPRESSIVE STRENGTH AT 28 DAYS(3) (psi) Wet 550 0.55 NA 4000 Dry 550 0.50 NA 4000 Wet (w/TAC(2)) 550 0.45 2.5 to 6.0 4000 Notes: (1) W/C = Water -Cementitious Ratio (by weight).
2.TAC = Total Air Content
3.As per AASHTO T 23
d.Mineral Admixtures. Fly ash may be used as part of the cementitious material in the shotcrete mix. Class “F” or Class “C” fly ashes may be substituted for cement up to a maximum substitution rate of 20 % of the total weight of the cementitious materials. Ground Granulated Blast Furnace Slag (GGBFS) may be use d as part of the cementitious material in the shotcrete mix. GGBFS may be substituted for cement up to a maximum substitution rate of 30 % of the total weight of the cementitious materials. Microsilica may be used as part of the cementitious material in th e shotcrete mix. Microsilica may be added up to a maximum addition rate of 10 % of the total weight of the cementitious materials.
e.Chemical Admixtures. Air entraining admixtures and water reducing admixtures may be used for wet -mix shotcrete only. Type "F" admixtures may be used for wet -mix shotcrete only to promote workability without exceeding the maximum allowable water -cementitious ratio. Admixture addition rates, dispensing, and mixing of the admixture shall be in accordance with the admixture man ufacturer's recommendations.
571.03 Construction.
571.03 Construction.
a.Anchorage and Reinforcement. The details of the anchorage and reinforcement of the shotcrete will either be shown on the plans or will be given elsewhere in the specifications when the shotcrete i s required as a part of other items of work.
b.Batching, Mixing and Placing Shotcrete. The requirements for batching, mixing and placing shotcrete shall be as described in ACI 506R, "Guide to Shotcrete". Metal wires shall be used to control the thicknes s and surface of the shotcrete. The temperature of the shotcrete mix shall be maintained between 50 º F and 90 º F.
c.Equipment.
1.Submittal of Description of Equipment. The Contractor shall submit a written description of the proposed equipment for mix ing and applying shotcrete. The submittal shall include the equipment manufacturer’s instructions, recommendations, literature, performance, and test data. This submittal shall be delivered to the Engineer. The placement testing of the shotcrete shall not begin until the Engineer informs the Contractor that the submittal is complete and the proposed mix design (or designs) have been evaluated for completeness by the Materials and Tests Engineer. The Contractor may use the information given in ACI 506R for identifying the equipment required for mixing and applying shotcrete.
2.Water Supply System for the Dry Mix Process. For the dry -mix process the Contractor shall provide a water storage tank at the job site. The Contractor shall also provide a positiv e displacement pump with a regulating valve that is accurately controlled to provide water at the required pressure and volume.
3.Mixing and Placing Equipment. The Contractor shall use equipment capable of handling and applying shotcrete containing the proposed maximum size aggregate and admixtures.
4.Air Hose and Blowpipe. An air hose and blow pipe shall be provided by the Contractor to clear dust and rebound during shotcrete application.
5.Air Supply System. An air supply system shall be provided by th e Contractor. The air supply system shall be capable of supplying the delivery machine and hose with air at the pressures and volumes recommended by the machine manufacturer. Air supply systems that deliver oil -contaminated air, or are incapable of maintai ning constant pressure shall not be used.
d.Testing of Materials and Placement Process prior to Construction.
1.Requirement for Field Testing. The Contractor shall perform a field test at least 30 calendar days before starting shotcrete production. The proposed mix design (or designs) shall be tested using the same equipment and personnel that will be used in production. The Contractor shall make arrangements for the Engineer to be present at the placement of the shotcrete for testing and at all of the s ubsequent testing of the samples of the shotcrete.
2.Test Panels from Field Tests. Application of shotcrete on test panels shall be done in the same manner that will be used for the production placement of the shotcrete. Test panels shall be fabricated in accordance with the requirements given in ASTM C 1140, "Standard Practice for Preparing and Testing Specimens from Shotcrete Test Panel ", as may be modified by the requirements given in this Section. The proposed mix shall be tested on two panels at least 3 feet by 3 feet in size. The thickness of the test panels shall be the same thickness as is required for the production placement. One panel shall be reinforced exactly like the production shotcrete will be reinforced. Test panels shall be cured in the same manner that the production shotcrete will be cured.
3.Coring Test Panels. Six cores shall be obtained from each test panel for testing. Each core shall be 3 inches in diameter and the full thickness of the test panel. The cores shall be taken from ea ch test panel in
571.03 Construction.
accordance with the requirements given in AASHTO T 24. Cores shall be extracted no more than 2 hours before testing.
4.Testing of Cores from Test Panels. Three cores from the unreinforced panel shall be tested for compressive strength at an age of 7 days. Three cores from the unreinforced panel shall be tested for compressive strength at an age of 28 days. Compressive strength tests shall be performed in accordance with the requirements given in AASHTO T 24, "Obtaining and Testing Drilled Cores and Sawed Beams of Concrete". Six cores shall be extracted from the reinforced panel at an age of 7 days for visual evaluation and nozzle operator qualification. These cores shall be delivered to the Materials and Tests Engineer for evaluation. The cores will be graded according to the requirements given in ACI 506.2, "Specification for Shotcrete".
e.Submittal of Material Test Data and Proposed Placement Process. The Materials and Tests Engineer will approve or reject the proposed mix design and pl acement process based on the results of the field testing and laboratory tests. Any changes to a previously accepted mix or the proposal of a new mix design will require field testing and laboratory testing before approval. The Contractor shall submit thre e copies of the test data and proposed placement process data to the Engineer for evaluation by the Materials and Tests Engineer. This data shall be submitted within 4 calendar days after the completion of the compressive strength tests that are performed on the cores at 28 days of age. The following data shall be submitted: • Sample identification including mix design and test panels represented. • Date and time of sample preparation including curing conditions. • Date and time of testing. • Sample dimensions. • Complete test results including load, sketches or pictures of samples before and after testing, and any unusual occurrences observed. • Name of laboratory and technician performing the tests. • Nozzle operator’s experience and training. If more th an one nozzle operator is used, each operator shall perform a set of test panels for each mix design proposed. Only nozzlemen with a test panel mean core grade less than or equal to 2.5 (as determined from the requirements given in ACI 506.2) will be allo wed to place shotcrete. The Engineer will inform the Contractor of the approval of the mix design and proposed placement equipment and procedures after an evaluation of the submittal that is made to the Materials and Tests Engineer.
f.Weather. The placem ent of the shotcrete shall be stopped if: • The wind is detrimental to the placement of the shotcrete; • The air temperature is below 40 ºF or above 90 ºF; • Rain or lightning are present.
g.Time Limit for Placing Shotcrete. The placement of dry -mix shotcrete shall begin within 45 minutes of the beginning of the mix production. A new batch of shotcrete shall be produced if placement does not begin within 45 minutes or if placement is not continuous. The placement of wet -mix shotcrete shall begin within 60 minut es after batching. A new batch of shotcrete shall be produced if placement does not begin within 45 minutes or if placement is not continuous.
h.Thickness of Layers and Time Between Placements of Layers. Shotcrete shall be placed in one continuous lift t hickness up to a maximum lift thickness of 6 inches. For shotcrete layer thicknesses greater than 6 inches, shotcrete shall be placed in lift thicknesses equal to one half the required thickness but no more than 6 inches per lift. If more than one lift is required there shall be a delay of time between the placement of each lift. The delay shall be until the initial set of the shotcrete. The initial set shall be defined as the point in time when the shotcrete has reached a compressive strength of 500 psi.
571.03 Constructio n.
The determination of initial set will be done by the Engineer using a penetrometer in accordance with the requirements given in AASHTO T 197, "Time of Setting of Concrete Mixtures by Penetration Resistance ". The Contractor shall furnish a penetrometer that is determined by the Engineer to be adequate for measuring the compressive strength. The Engineer shall have exclusive possession and use of the penetrometer beginning at least 5 calendar days before the start of shotcrete placement. The penetrometer will be returned to the Contractor when shotcrete placement is completed. At the point in time when the initial set is achieved, the surface shall be lightly broomed to remove laitance to provide an adequate bond with the next application of shotcrete. The En gineer will also determine when the shotcrete has taken a final set and remedial actions shall be taken by the Contractor to insure a bonding of subsequent layers of shotcrete.
i.Construction Joints. Boards or other solid materials shall be installed to provide the construction joints. The solid joint materials shall be removed and the joints shall be thoroughly cleaned before additional shotcrete is placed at the joint.
j.Curing. Two methods will be allowed for curing. The first method of curing is by keeping the surface of the shotcrete continually moist for at least 7 days by burlap that is kept wet. The second method of curing is by using an impervious membrane (curing compound) meeting the requirements given in Section 830.
k.Surface Finish.
1.Retaining Walls. The final surface of the shotcrete shall be finished to an even plane. The surface shall be finished to within 1/2 inch in 10 feet as measured by placing a straightedge anywhere on the surface of the shotcrete. All metal construction mate rials such as guide wires and tie wires that protrude through the surface shall be removed from the surface by breaking back the protrusion and patching the flaw with cement mortar as directed by the Engineer. The shotcrete wall shall be finished with a sl ight chamfer at the exterior edges of the wall. Any additional surface finishing requirements will be shown on the plans.
2.Rock Face Protection. The shotcrete surface shall be left in the natural shotcrete gun finish.
l.Drainage If draining of water f rom behind the shotcrete is required the details of the drainage system will be shown on the plans.
m.Cleaning Excessive Shotcrete. The excessive placement of shotcrete shall be continuously removed to protect the adjacent areas and keep the prior place ment of shotcrete clean. "Rebound" shotcrete shall be promptly removed from the work area.
n.Defective Work. Areas of defective work shall be replaced. The Contractor shall submit a written replacement procedure to the Engineer for review prior to makin g the repair. All repair work shall be performed without additional compensation.
o.Shotcrete Production Report. The Contractor shall submit a written report of the shotcrete production and application to the Engineer within 24 hours of the completion of shotcrete application. The following shall be included in the report: • Quantity and location of shotcrete applied including sketches of areas where shotcrete was placed; • Observations of success or problems of equipment operation, application, final conditi on, and any other relevant issues encountered during production and application; • The batch number of the shotcrete; • Name of nozzleman; • Name and signature of the Contractor's supervisor performing the observation.
572.02 Materials.
p.Test Panels, Coring And Testing During Production Placement. The Contractor shall produce a test panel in accordance with the requirements given in ASTM C 1140 for each work day or every 50 cubic yards of shotcrete placed, whichever is less. Test panels shall be kept moist at all times. The pan els shall be kept between 60 º F to 80 º F for the first 24 to 48 hours before they are moved to the testing laboratory for standard curing. Five cores for compressive strength test specimens shall be obtained from each panel and shall be tested in accorda nce with the requirements given in AASHTO T 24. Two samples shall be tested at 7 days and three at 28 days. Test reports shall be forwarded to the Engineer within 24 hours after testing. Cores for testing shall be obtained from the panels no more than 2 ho urs before testing. It shall be the responsibility of the Contractor to retain a testing laboratory, approved by the Department, to perform these tests.
571.04 Method of Measurement.
Shotcrete may be measured as a part of other items of work. A separate qu antity of shotcrete will not be given when it is included in other items of work. When direct payment is made for shotcrete it will be measured in units of square yards at the surface of the shotcrete placement. The square yardage will be limited to the actual number of square yards placed within lines shown on the plans, or designated by the Engineer, that define the plan limits of the required shotcrete placement. All portions of shotcrete placed outside the limits of measurement will be considered incidental to the placement of the shotcrete.
571.05 Basis of Payment.
a.Unit Price Coverage. The contract unit price for shotcrete shall be full compensation for all materials, equipment tools, labor, testing and incidentals required to complete this item of work. The contract unit price includes preparation of the surface to be treated, furnishing and installation of wire reinforcement and anchor bolts and the furnishing and installing the materials required for drainage and final surface finishing.
b.Payment will be made under Item No.: 571-A Shotcrete * inches Thick - per square yard SECTION 572 SOLDIER PILE RETAINING WALL
572.01 Description.
The work of this Section shall cover designing and constructing a soldier pile retaining wall with permanent ground anchors consisting of steel piles and lagging. The soil and rock behind the wall shall be retained by lagging set in the pile flanges.
572.02 Materials.
a.Steel Piles. Steel piles shall meet the requirements given in Section 834.
b.Structural and Reinforcing Steel. Structural steel shall meet the requirements given in Section 836. Reinforcing steel shall meet the requirements given in Section 835.
c.Concrete for Anchoring Piles in Drilled Holes. Concrete for anchoring piles in drilled holes shall meet the requirements given in Section 501 for Class A concrete.
d.Grout
1.Low Strength Cement Mortar for Stabilizing Drilled Holes. Low strength cement mortar shall meet the requirements given in Section 260 for Cement Mortar Flowable Backfill, Mix 2.
2.Grout for Ground Anchors . The grout shall be a neat cement or sand/cement grout. The Contractor shall submit the proposed grout mix design to the Materials and Tests Engineer for approval no later than 30 calendar
Source: Alabama Standard Specifications for Highway Construction, 2022 Edition. Pages 449–453 of 934.