1. PURPOSE
1.1 This specification defines for the contractor the minimum requirements for furnishing and installing auger-cast piles.
2. SCOPE
2.1 The piling contractor (herein known as the contractor) shall furnish all labor, materials, tools, and equipment necessary for furnishing, installing, and testing auger-cast piles as shown on the contract drawings and as specified herein.
2.1.2 Air Products will furnish a representative knowledgeable in this type of installation to inspect and report to Air Products regarding the requirements of this specification.
2.2 Contractor Qualifications
2.2.1 All piles shall be installed by an experienced contractor who shall submit evidence of successful installation of auger-cast piles under similar job and subsurface conditions, including a job supervisor who shall have a minimum of three years of method-specific experience.
2.3 System Description
2.3.1 Auger-cast piles shall be made by rotating a continuous-flight, hollow-shaft auger into the ground to the specified pile depth, or until the specified refusal criteria are satisfied. As the auger is being withdrawn, grout shall then be injected through the auger shaft in such a way as to exert a positive upward grout pressure on the earth-filled auger flights as well as lateral pressure on the soil surrounding the grout-filled pile hole.
2.4 Site Conditions
2.4.1 The contractor shall examine the areas and conditions under which piles are to be installed and notify the Air Products construction superintendent, in writing, of conditions detrimental to the proper and timely completion of the work.
3. RELATED DOCUMENTS
3.1 Air Products Engineering Documents
4WCE-600702 Piling Safety
3.2 American Concrete Institute (ACI)
305R Hot Weather Concreting
306R Cold Weather Concreting
318 Building Code Requirements for Structural Concrete
SP-66 ACI Detailing Manual
3.3 American Society for Testing and Materials (ASTM)
A 615 Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement
C 33 Specification for Concrete Aggregates
C 109 Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2 in. or (50 mm) Cube Specimens)
C 150 Specification for Portland Cement
C 311 Test Methods for Sampling and Testing Fly Ash or Natural Pozzolans for Use in Portland Cement Concrete
C 618 Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete
C 942 Test Method for Compressive Strength of Grouts for Preplaced-Aggregate Concrete in the Laboratory
3.4 Deep Foundations Institute (DFI)
Augered Cast-In-Place Piles Manual
3.5 National Ready-Mixed Concrete Association (NRMCA)
Technical Paper – Certification of Ready-Mixed Concrete Production Facilities
(Checklists with instructions)
3.6 All specifications or codes referenced shall be the latest editions.
4. MATERIALS AND PRODUCTS
4.1 Portland Cement
4.1.1 Portland cement shall conform to the requirements of ASTM C 150. Type I shall be used unless otherwise specified on the contract drawings.
4.2 Mineral Admixture
4.2.1 Mineral admixture, if used, shall be fly ash or natural pozzolan, which possesses the property of combining with the lime liberated during the process of hydration of Portland cement to form compounds containing cementitous properties. The material shall conform to ASTM C 618.
4.2.2 Use only one source of fly ash. Each shipment shall have test reports (at a frequency of not less than one test for each 50 tons of fly ash delivered) certifying compliance with ASTM C 311.
4.3 Fluidifier
4.3.1 Fluidifier shall be a compound possessing characteristics that will increase the fluidity of the mixture and act as a water-reducing agent and retardant.
4.4 Water
4.4.1 Water shall be potable, fresh, clean, and free of sewage, oil, acid, alkali, salts, or organic matter and shall conform to the requirements of paragraph 3.4 of ACI 318.
4.5 Fine Aggregate
4.5.1 Sand shall meet the requirements of current ASTM standards, designation C 33.
4.6 Reinforcing Bars
4.6.1 Reinforcing bars shall conform to the requirements of ASTM A 615, Grade 60.
4.7 Grout Mixes
4.7.1 The grout shall consist of Portland cement, sand, and water and may also contain a mineral admixture and approved fluidifier. The components shall be proportioned and mixed to produce a grout capable of maintaining the solids in suspension, which may be pumped without difficulty and which will penetrate and fill open voids in the adjacent soils. These materials shall be proportioned to produce a hardened grout which will achieve the design strength within 28 days. The design 28-day strength shall be 27.5 MPa (4000 psig).
4.7.2 All materials shall be accurately measured by volume or weight as they are fed to the mixer. Time of mixing shall be not less than one minute at the site. If agitated continuously, the grout may be held in the mixer or agitator for a period not exceeding two and one-half hours at grout temperatures below 21°C (70°F) and for a period not exceeding two hours at higher temperatures, not exceeding 38°C (100°F). Grout shall not be placed when its temperature exceeds 38°C (100°F).
4.8 Reinforcing Bar Fabrication
4.8.1 Reinforcing steel assemblies shall be detailed and fabricated according to ACI SP-66.
5. SUBMITTALS
5.1 In addition to the description of the pile drilling and pumping equipment to be used, the contractor shall submit, with his bid to Air Products, the following information for approval:
5.1.1 Working Drawings
5.1.1.1 A Drilling Sequence Plan referenced to the structural plans, which includes a numbering system indicating the order of pile placement.
5.2.1 Grout Mix Design
5.2.1.1 Proposed pile grout design mix and descriptions of materials to be used. These shall be in sufficient detail to indicate their compliance with the specifications and either laboratory tests of trial mixes made with the proposed mix, or laboratory tests of the proposed mix used on previous projects. The following information shall accompany each mix design:
Sources of aggregate and test data certifying the requirements of ASTM C 33.
Complete gradation and fineness modulus of aggregates.
Specific gravity of aggregates and cement.
Dry, rodded unit weight of aggregate.
Quantities of all components of the mix, including air entrainment agents, superplasticizer, and other admixtures, if used.
When admixtures are used, the manufacturer’s information shall accompany the mix design.
Results of 7-day and 28-day cylinder tests using the proposed mix.
Plant standard deviation, if available.
Type of cement: i.e., Type I, II, and III.
5.2.1.2 No substitution of materials of an approved mix design shall be made without the prior approval of Air Products. All of the above must be submitted for approval at least 15 days in advance of the concrete operation to which the mix applies.
5.2.1.3 Air Products approval of the concrete design mix does not relieve the contractor of the responsibility to furnish materials and construction in full conformance with the drawings and specifications.
5.2.1.4 If, during the progress of the work, it is desired to use materials or proportions other than those originally approved or if the materials from the sources originally approved change in characteristics, the contractor shall submit for approval evidence that the new combinations of materials will produce concrete meeting the requirements of this specification and will not bring about objectionable changes in color, appearance, or structural strength.
6. EQUIPMENT
6.1 Augering Equipment
6.1.1 The auger flighting shall be continuous from the auger head to the top of auger without gaps or other breaks. The auger flighting shall be uniform in diameter throughout its length and shall be the diameter specified for the piles less a maximum of 3%.
6.1.2 The hole through which the grout is pumped during the placement of the pile shall be located at the bottom of the auger head below the bar containing the cutting teeth.
6.1.3 Augers over 12 m (40 ft) in length shall contain a middle guide.
6.1.4 The piling leads shall be prevented from rotating by a stabilizing arm or by firmly placing the bottom of the leads into the ground or by some other acceptable means. Leads shall be marked at 300 mm (1 ft) intervals to facilitate measurement of auger penetration.
6.1.5 Only approved pumping and mixing equipment shall be used in the preparation and handling of the grout. A screen to remove oversize particles shall be placed at the pump inlet. All oil or other rust inhibitors shall be removed from mixing drums and grout pumps. All materials shall produce a homogeneous grout of the desired consistency.
6.1.6 The grout pump shall be a positive displacement pump capable of developing displacement pressures at the pump not less than 2.4 MPa (350 psig). The grout pump shall be provided with a pressure gauge in clear view of the equipment operator. The grout pump shall be calibrated, if required, at the beginning of the work to determine the volume of grout pumped per stroke. A positive method of counting grout pump strokes shall be provided by the contractor. Such methods may include digital or mechanical stroke counters or other acceptable methods. A second pressure gauge, if required, shall be provided close to the auger rig where it can be readily observed by the inspector.
7. FORMWORK
7.1 Forms for grouting any section of pile above grade (if required) shall conform exactly to the shape, lines, and dimensions shown on the contract drawings. The contractor shall have the option of using either of the following choices:
Galvanized corrugated pipe.
Sonotube tubing: contractor shall remove tubing after grout has set (7 day minimum).
7.2 Any substitutions to the above options shall be submitted to Air Products for evaluation.
8. INSTALLATION
8.1 Tolerance
8.1.1 Piles shall be located as shown on drawings. Pile centers shall be located to an accuracy of
+/- 75 mm (3 in) and shall be plumb within 2%.
8.2 Adjacent Piles
8.2.1 Adjacent piles within 3.5 m (11 ft), center to center, shall not be installed within 24 hours of each other.
8.3 Probe Piles
8.3.1 Furnish and install probe piles to determine if the contractor’s methods, materials, and equipment conform to these specifications and produce the result desired by the Air Products representative as defined in paragraph 9.1. The location, length, diameter, and other relevant information will be shown on the plans. There are two probe piles required. The contractor shall provide all materials and equipment required to install the probe piles in the presence of the Air Products representative.
8.3.2 Probe piles shall become part of the foundation system. Install them with the same pile installation equipment, following completely the procedures to be used for installation of test piles and production piles.
8.4 Installation Procedure
8.4.1 The length and drilling criteria of production piles will be as specified on the Air Products contract drawings with adjustment from the installation of the probe piles, if required.
8.4.2 Advance the auger at a continuous rate that prevents removal of excess soil. Stop advancement after reaching the required depth or refusal criteria.
8.4.3 Auger refusal is defined as a rate of auger penetration of less than 300 mm/min (1 ft/min) of drilling.
8.4.4 The hole in the bottom of the auger shall be closed while being advanced into the ground with a suitable plug. The plug shall be removed by grout pressure.
8.4.5 At the start of pumping grout, raise the auger from 150 to 300 mm (6 to 12 in) and after the grout pressure builds up sufficiently, redrill the auger to the previously established tip elevation.
8.4.6 A head of at least 1.5 m (5 ft) of grout on the auger flighting above the injection point shall be maintained during raising of the auger. Positive rotation of the auger shall be maintained at least until placement of the grout. Rate of grout injection and rate of auger withdrawal from the soil shall be coordinated to maintain the minimum grout head at all times. The total volume of grout per linear foot of pile be not less than the volume of grout per foot established for the test pile. After grout is flowing at the ground surface from the auger flighting, the rate of grout injection and auger withdrawal shall be coordinated so that there is a constant grout flow at the surface. If pumping grout is interrupted for any reason, the contractor shall reinsert the auger by drilling at least 1.5 m (5 ft) into the pile and then regrout.
8.4.7 If the actual installed volume of grout per linear foot is less than the volume of grout per linear foot required established in the test pile, in any 1.5 m (5 ft) increment (until the grout head on the auger flighting reaches the ground surface), the pile shall be reinstalled by advancing the auger 3 m (10 ft) or the bottom of the pile if that is less, followed by controlled removal and grout injection.
8.4.8 Auger-hoisting equipment shall be provided that will enable the auger to be rotated while being withdrawn.
8.4.9 The contractor shall establish safe distances from the rotating auger to protect personnel and inspectors by posting someone at the drilling operation to warn others and keep them away, or set up a barricade around the safe distance area. Additional safety requirements are addressed in Section 8 of 4WCE-600702 and shall be followed.
8.5 Obstructions
8.5.1 If nonaugerable material is encountered, such as cobbles, boulders, rock ledge, metal, timbers, or debris that causes the rate of penetration to be reduced to less than 300 mm/min (1 ft/min) above the desired tip elevation or causes the pile to drift from its location, the pile shall be completed to the depth of the nonaugerable material according to these specifications. The length of such short piles shall be included in the total linear feet of pile for payment. If required by the Air Products representative, additional adjacent piles shall be replaced, and the length of these additional piles shall also be included in the total linear feet of piles for payment.
8.6 Cutting Off
8.6.1 Cut off the tops of piles square with pile axis and at the elevations indicated on the drawings. Cutoffs shall be made by removing fresh grout from the top of the pile or by cutting off hardened grout down to final cutoff point at any time after initial set has occurred.
8.6.2 When the pile cutoff is above the bottom of the excavation, sleeves or casing of the proper diameter and at least 450 mm (18 in) in length shall be placed around the pile tops. Piles shall be extended by using a sheet metal or fiber cylindrical “can” placed part in and part out of the pile.
8.7 Reinforcing Steel Placement
8.7.1 Acceptable methods shall be provided to facilitate proper embedment and centering of any steel cores or tension reinforcing steel cages installed in the piles. Extra care shall be taken to hold reinforcing steel cages at the proper elevation. Cages shall be placed before the grout has begun to set.
8.8 Disposal of Spoils
8.8.1 Spoils from the pile installation will contain grout and must be properly disposed. The contractor is responsible for the disposal of this material.
9. TESTING AND INSPECTION
9.1 Representative
9.1.1 The contractor shall furnish a representative from an independent inspection agency qualified in this type of work to inspect the pile installation. The contractor shall cooperate with the representative in the performance of this work. No pile installation work shall be performed unless the representative is present. The presence of the representative in no way relieves the contractor of his obligation to perform the pile installation according to the contract drawings and these specifications.
9.2 Pile Acceptance
9.2.1 The inspection agency representative will determine the acceptability of the piles and will immediately notify the contractor if a pile is not in conformance with these specifications.
9.3 Material Testing
9.3.1 The grout mix shall be tested by making a minimum of six 2-inch cubes for each day during which piles are placed. A set of six cubes shall consist of two cubes to be tested at seven days, two cubes to be tested at 28 days, and two cubes held in reserve. Test cubes shall be cured and tested according to ASTM C 109. Cube specimens may be restrained from expansion as described in ASTM C 942.
9.3.2 Test the flow of each batch of grout.
9.3.3 Protect grout from physical damage or reduced strength, which could be caused by frost, freezing actions, or low temperatures or from damage during high temperatures according to ACI 305R/306R.
9.4 Records
9.4.1 The contractor’s representative from the inspection agency shall submit to Air Products two copies of the installation record of each pile no later than three days after installation is completed. This record will include:
The project name and number
Name of contractors
Pile location
Design pile capacity
Pile diameter
Tip and butt elevation
Drilling elevation
Quantity of grout placed (total and/or continuous)
Any unusual occurrences during the pile installation
The grout quantity shall be determined by recording grout pump displacement or by other acceptable means.