Section 4 — Structures and Foundations

Concrete Construction Requirements

IPE Engineering Practice IPE-EP-4-3-2

Document number: IPE-EP-4-3-2 · Section: 4 — Structures and Foundations

SCOPE

This standard, project specifications, design drawings, and technical standards, define the construction requirements for plain and reinforced cast-in-place concrete.
When local, city, or regional codes or ordinances are mandatory, construction shall conform to those requirements and to those portions of this specification that do not conflict with local requirements.
Design of concrete buildings and other structures constructed to this Practice shall be in accordance with EP 4-3-1.
Design of foundations constructed to this Practice shall be in accordance with EP 4-2-3.
Any deviation to this Practice must be approved by the procedures described in EP 1-1-3.
An asterisk (*) indicates that a decision or approval of the Owner or the Owner's Engineer is required, or that additional information is furnished by the Purchaser.
A revision bar indicates all changes made to this Revision.
Documentation required for concrete construction in accordance with this Practice is given in Table 5.

2.0 REFERENCES

The latest edition of the following standards and publications are referred to herein.

STANDARDS AND PUBLICATIONS

IPE Engineering Practices
EP 1-1-3 Deviations to IPE Engineering Practices Reinforced EP 4-2-3 Concrete Foundations EP 4-2-9 Grouting and Baseplates for Structural Steel and Equipment EP 4-3-1 Concrete Design EP 4-3-3 Concrete Reinforcement Fabrication
ACI
211.1 Standard Practice for Selecting Proportions for Normal, Heavyweight and Mass Concrete 301 Specification for Structural Concrete for Buildings 304 Measuring, Mixing, Transporting and Placing Concrete 305 Recommended Practice for Hot Weather Concreting Recommended Practice for Cold Weather Concreting 308 Standard Practice for Curing Concrete 347 Recommended Practice for Concrete Formwork

STANDARDS AND PUBLICATIONS (CONT.)

ASTM
C31 Making and Curing Concrete Test Specimens in the Field C39 Test for Compressive Strength of Cylindrical Concrete Specimens C94 Ready-Mixed Concrete C143 Test for Slump of Portland Cement Concrete C150 Portland Cement C172 Sampling Fresh Concrete C173 Test for Air Content of Freshly Mixed Concrete by the Volumetric Method C231 Test for Air Content of Freshly Mixed Concrete by the Pressure Method
AWS
D1.4 Structural Welding Code, Reinforcing Steel
CRSI
MSP-2-81 Manual of Standard Practice

3.0

3.1

3.2

3.3

3.4

4.0

4.1

4.1.1

4.1.2

DEFINITIONS

Contractor - Company or business that agrees to furnish materials or perform specified services at a specified price and/or rate to the Owner.

Inspector - A Inflection Point Engineering, LLC appointed engineer or inspector. Owner - Inflection Point Engineering, LLC.

Owner's Engineer - A Inflection Point Engineering, LLC appointed engineer.

SUBGRADE PREPARATION AND FORMWORK

Foundation Subgrade Preparation

Excavations in materials shall be made with minimal disturbance of the bottom. All excavations shall be level, and free of loose material. The final work of excavating shall be completed just prior to the placing of the reinforcing steel and concrete.

All foundations shall be carried to good bearing soil and to the minimum depth below finish grade as indicated on the design drawings. If the requisite bearing is not encountered at the indicated minimum depth, or should over-excavation occur, the following shall be complied with:

Variations less than 3.0 inches shall be corrected by the use of a lean concrete having an ultimate strength in excess of 2000 psi.
(*)Variations exceeding 3.0 inches shall be referred to the Owner's Engineer for solution.

(*)Earth Cuts shall not be used as forms for vertical surfaces unless approved by the Owner's Engineer.
Formwork
Formwork should be designed, erected, supported, braced, and maintained so that it will sustain all vertical and lateral loads until such loads can be supported by the concrete structure.
Forms shall conform to the shape and dimensions of the members shown on the drawings.
Forms shall be true, rigidly constructed, and sufficiently tight to prevent leakage of cement paste.
All forms for exposed work shall be free of defects likely to cause imperfections in the surface of the concrete.
Forms shall be suitable for the work to be performed and shall be of dressed lumber, plywood, metal, or other suitable materials.
Chamfer strips are required only when specified on the drawings.
Forms shall be thoroughly cleaned and a form release agent shall be applied before any reinforcing steel is placed. Excess release agent shall not be allowed to stand in puddles in the form or on previously placed concrete.
Form material that is to be reused shall have damaged parts repaired and the concrete side thoroughly cleaned before reusing.
Temporary openings shall be provided at the base of column and wall forms to facilitate cleaning and inspection.
Adjustable type shoring shall be used for supporting roof forms or elevated floors.
Tolerances and other details for formwork shall be in accordance with ACI 347.
(*)Form ties shall be standard shop ties or screw ties except for cooling tower basins, clarifiers and other water retaining structures which shall be "Waterseal Snap-Ty" or an Owner's Engineer approved equivalent:
The holes left by the removal of the tie ends shall be patched.
Forms shall be constructed to facilitate their removal without damage to the concrete. Forms shall be preferably removed in the following order (1) columns, (2) sides of beams and girders, (3) bottom of slabs, beams, and girders.
(*)No forms shall be left permanently in place without approval from the Owner's Engineer.
Forms for shoring shall not be removed until the concrete has gained sufficient strength to support its own weight and other imposed loads.

REINFORCEMENT AND ANCHOR BOLTS

Reinforcement

All reinforcing shall be accurately placed and supported using chairs and/or spacers, selected in accordance with EP 4-3-1, to prevent displacement by construction loads or the placing of concrete.
The clear distance between parallel bars in a layer and bars in adjacent layers shall be per ACI standards.

(*)Any tack welding of reinforcement shall be performed only when approved by the Owner's Engineer and in strict compliance with the provisions of AWS D1.4.
Bar reinforcement that must be fabricated at the job site shall be made to conform to the shape and dimensions specified on the drawings and the applicable ACI standards.
All bending shall be done cold around pins of the minimum diameters given in Chapter 6 of CRSI MSP-2-81 and referenced on the drawings.
Reinforcement shall be free of loose rust and of any other coating that may adversely affect the bond.
(*)Splices in bar reinforcement shall be per ACI Standards and shall be lapped and located as shown on the design drawings. Bars in lapped splices shall be in contact unless otherwise shown on the engineering drawings. Additional splices, if required, shall be made only at locations, and in a manner approved by the Owner's Engineer. Welded and mechanically connected splices shall not be used.
Welded wire fabric used in structural concrete shall have splices lapped such that the overlay between the outermost cross-wires of each fabric sheet is not less than two spaces of the cross-wires plus 2 inches in the direction of the spans. Side laps shall overlap not less than the spacing of the longitudinal wires. Fabric shall be supported, in the same manner as reinforcing bars, to place the fabric in its proper location within the concrete member.
Welded wire fabric used in concrete paving shall have lapped splices made so that the overlap between the outermost wires of each fabric sheet is not less than the spacing of the cross wires. In lieu of adequate support of the welded wire fabric, the fabric shall be lifted during placing of concrete to ensure proper positioning in the concrete.
(*)The minimum concrete cover over reinforcement shall be in accordance with ACI Standards, unless otherwise specified by the Owner's Engineer.
Reinforcement materials shall comply with EP 4-3-1 and EP 4-3-3.
Anchor Bolts and Other Embedded Items
Anchor bolts and other embedded items shall be installed as shown on the drawings prior to placing concrete. Unless otherwise noted on the drawings, anchor bolts and embedded items shall be placed within the following tolerances:
Bolt projections: +1/4 in., -1/8 in.
Bolt location-without sleeves: 1/8 in.
Bolt location-with sleeves: 3/16 in.
Bolt sleeves with open tops shall be packed to keep concrete out during the pour.
Sleeves shall ultimately be grouted in accordance with EP 4-2-9.
Anchor bolts shall comply with EP 4-2-3.

The Owner's Engineer shall approve anchor bolt details not given in EP 4-2-3.

CONCRETE SELECTION PRODUCTION, AND TESTING

Proportioning Concrete
Concrete shall be proportioned to provide an average strength as prescribed in EP 4-3-1. In addition, it shall be proportioned so as to provide workability, resistance to special exposures and consistency.
(*)The maximum water-cement ratio for concrete shall be 0.5 unless otherwise approved by the Owner's Engineer. To use water-cement ratios greater than 0.5, compressive strength tests shall be performed and field experience shall be used to demonstrate the adequacy of the mix. Additionally, if freeze-thaw resistance is required, air-entrained cement or admixtures shall be used. If the concrete is to be used in a watertight application, the maximum water-cement ratio shall be 0.45 for fresh water exposure and 0.40 for brackish or sea water exposure.
The recommended slumps for concrete shall conform to ACI 211.1 and Table 1. If the recommended slumps are not met, the concrete shall not be used and shall be replaced at the Contractor's expense.
Ready-Mixed Concrete and Mix Design
Delivered concrete shall be batched, mixed, and transported, in accordance with ASTM C94.
Concrete shall be sampled and tested in accordance with this Practice and ASTM C94.
Materials used in ready mixed concrete shall be per EP 4-3-1.
(*)Unless otherwise specified by the Owner's Engineer, all ready-mix concrete shall be designed to meet the minimum requirements for 28 day compressive strength in Table1 of EP 4-3-1.
(*)The contractor shall submit mix designs for each proposed use to the Owner's Engineer for approval. Each mix design shall include appropriate laboratory testing results to demonstrate that the mix meets the specified requirements.
(*)In conditions not considered "hot weather" by ACI 305, ready-mix concrete shall be delivered to the site and discharged in less than one and one-half hours after either introducing the mixing water to the cement and aggregates or introducing the cement to the aggregates. In "hot weather" conditions, ready-mix concrete shall be discharged in less than one hour, unless otherwise approved by the Owner's Engineer.
Batch Mixing at the Site
(*)Unless otherwise approved by the Owner's Engineer, material characteristics and proportions of concrete ingredients shall conform to those specified for ready-mixed concrete.
Cement and aggregates shall be stored so as to prevent their deterioration or the intrusion of foreign matter. Any material that has deteriorated or has been contaminated shall not be used for concrete.

Batching and mixing of concrete shall be as recommended in ACI 301 for batch mixing at the site.
Concrete Temperature
Cold weather placement of concrete shall be in accordance with ACI 306 and the following:
In cold weather, when the mean daily temperature is less than 40°F, the temperature of the concrete when delivered at the site shall conform to the temperature limitations of Table 2.
If water or aggregate is heated above 100°F, the water shall be combined with the aggregate in the mixer before cement is added. Cement shall not be mixed with water or with mixtures of water and aggregate having a temperature greater than 100°F.
Concrete shall only be poured when the ambient temperature is rising.
Hot weather placement of concrete shall be in accordance with ACI 305 and the following:
For concrete sections having a least dimension of 2-1/2 feet of more, a maximum concrete temperature of 60°F is desirable.
For other concrete structures, a maximum of 90°F is recommended. Every effort shall be made to place the concrete at a temperature lower than 90°F.
Concrete temperatures shall be kept within desirable limits using methods recommended in ACI 305.
Protection against excessive drying shall be provided for the first seven days.
Testing, Evaluation, and Acceptance
(*)Sampling and testing requirements shall be performed in accordance with the standards listed in Table 3 and shall be made by an independent laboratory approved by the Owner's Engineer.
A set of compression test specimens shall consist of four 6 in. x 12 in. (diameter x length) cylinders, each cylinder being one specimen.
A set of compression test specimens shall be made at the following frequency:
A minimum of one set for concrete placed each day.
One set for each structure or foundation exceeding 10 cubic yards.
A group of smaller structures or foundations shall require one set for each total of 50 cubic yards each day.
Each large structure shall have one set of test cylinders taken for the first 10 cubic yards placed each day. Then an additional set shall be taken for each additional 50 cubic yards or increment thereof, in the same day.
All of the test specimens shall be cured under moist conditions in conformance with testing standards in Table 3.
The specimens within each set shall be tested at the following ages in accordance with testing standards in Table 3.
One at 7 days for information.

Two at 28 days. The 28-day strength shall be taken as the average of the two specimens. If one specimen in this test shows evidence of improper sampling, molding or testing, it shall be discarded. The remaining specimen shall be considered the test result. Should both specimens show defects, the entire test shall be discarded.
The fourth shall be retained as a spare to be tested as required.
The following tests shall be made at the time the strength test specimens are made. Additional tests, at a greater frequency, shall be performed as required to ensure uniform quality of concrete.
Determine slump of the concrete in accordance with testing standards in Table 1.
When air-entrained concrete is used, determine the air content of the concrete in accordance with testing standards in Table 3.
Determine the temperature of the concrete sample to check compliance as specified in this Practice.
All concrete shall conform to the provisions of ASTM C94.
(*)Unless core sampling approved by the Owner's Engineer indicates that in-situ concrete strength is acceptable, the Contractor shall remove and replace all concrete that fails to meet the specified strength requirements at 28 days when tested in accordance with the specified requirements, at the Contractor's expense. Core sampling and testing shall be performed at the Contractor's expense.
(*)The results of all laboratory and field testing shall be recorded in a manner consistent with the applicable test standard in Table 3. These results shall be recorded on EP 4-3-2C or an alternative format approved by the Owner's Engineer.

PLACING CONCRETE

Pre-placement Preparation
Unless noted on the drawings, existing concrete surfaces against which fresh concrete will be placed, shall be roughened, thoroughly cleared of loose material and wetted.
Semi-porous subgrade shall be watered sufficiently to eliminate suction.
Extremely porous subgrade shall be sealed.
Standing water within excavations shall be removed.
Formwork shall have been constructed, secured in place and coated in accordance with Section 4.0 of this Practice.
Reinforcement shall have been placed and secured.
Materials to be embedded shall have been positioned and secured in place.
Necessary concrete placement equipment and curing materials shall be at the site.
Placement
Placement of concrete shall conform to the requirements of ACI 304 and the additional requirements of this Practice.

Concrete shall not be placed on frozen ground or other frozen surfaces. Also, all snow or ice shall be removed prior to placing concrete.
Concrete shall be placed in its final position to avoid segregation due to over-handling.
Concrete shall be placed continuously in uniform layers of approximately 2 feet in thickness. The concrete shall be placed so that no concrete will be deposited on concrete that has hardened sufficiently to cause the formation of seams or planes of weakness. Concrete shall be placed at such a rate that it will be integrated with previously placed concrete.
When it is necessary to deposit concrete under water or in deep forms or excavations, tremies, chutes, pumps or other techniques shall be used to avoid segregation of the concrete materials.
Placing of concrete in supported elements shall not be started until the concrete previously placed in walls and columns is no longer plastic and has been in place at least two hours.
Unless appropriate measures are taken to prevent excessive moisture loss before the final curing agent is applied, concrete shall not be placed when the following conditions exist:
Shade temperature in excess of 110°F at the job site, combined with a mean wind speed of 10 mph or over.
Other combinations of temperature, wind velocity, and relative humidity which produce a rate of evaporation that exceeds 0.25 lb/ft2/hr as determined by Figure 2.1.4 of ACI 305.
Interior surfaces of wooden forms, and reinforcement within the form, shall be sprayed with water to prevent excessive absorption of water from the fresh concrete.
All concrete shall be consolidated by vibration, spading, or rodding so that the concrete is worked around the reinforcement and embedded items. Concrete shall be worked into corners of the forms to eliminate any air and stone pockets that may cause honeycombing, pitting, or planes of weakness.
Internal vibrators shall have a minimum frequency of 8000 vibrations per minute and sufficient amplitude to consolidate the concrete effectively.
Vibrators shall be inserted and withdrawn at points approximately 18 inches apart. At each insertion, the duration shall be sufficient to consolidate the concrete but not sufficient to cause segregation. Generally, the vibrator should be moved every 5 to 15 seconds.
A spare vibrator shall be available for critical pours.
(*)Once concrete placement is started, placement shall continue until the panel or section is completed, or until a suitable construction joint is reached. Construction joints in columns shall be at the bottom of the element supported, at mid-span in floor or roof slabs, girders and beams, and as shown on the drawings or as directed by the Owner's Engineer.
Anchor bolt threads shall be protected during pouring. If spattered with concrete, threads shall be cleaned during or immediately following the pour.
Concrete shall be deposited only when the Inspector is present.

FINISHING, CURING FORM REMOVAL. INSPECTION AND PATCHING

Finishing

(*)Unless otherwise specified by the Owner, concrete surfaces shall be finished as follows:

Pavements and Walks:
Top surfaces shall be brought to proper level with a screed.
After the water sheen has disappeared, the surface shall be floated with wood or metal floats or with a finishing machine using float blades.
Before the concrete has thoroughly hardened, the surface shall be roughly scored using a steel wire or stiff coarse fiber broom. The depth of scoring shall not exceed 1/8 inch.
Building Floor and Roof Slabs:
Screed and float as specified for pavements and walks.
All roof slabs and floor slabs receiving a tile-floor or other type of finish shall be finished in accordance with recommendations of the manufacturer of the floor covering.
Other building floors shall be given a steel trowel finish.
Equipment Foundations, Building Foundations, Trenches, Pits, Boxes, and Sumps:
Screed and float as specified for pavements and walks.
A wood float finish shall be provided. Surfaces to receive grout or concrete shall be roughened.
No finish is required for surfaces exposed to forms other than patching of surface defects.
Curing
Curing of concrete shall be performed using the applicable methods and procedures recommended in ACI 305, ACI 306, and ACI 308.
Curing by any of the methods specified shall continue for a minimum of 7 days in which the temperature of the concrete is 50°F or more.
During the curing period, the concrete shall be protected from damage by construction equipment, materials, rain, running water, heavy shock, and vibration.
When the mean daily temperature is less than 40°F, the concrete shall be maintained between 50 and 70°F for the required curing period. Necessary arrangements shall be made in advance for heating, covering, insulating, or enclosing the concrete work to maintain the required temperature and moisture conditions. When heaters using combustible fuels are used in an enclosure, the heaters shall be vented to the outside of the enclosure.
In hot weather, necessary arrangements shall be made in advance for protective measures needed to prevent rapid drying of the concrete. These protective measures shall be started as quickly as finishing and hardening will allow.
Form Removal
(*)The minimum age after which forms may be removed from the concrete shall be as given in Table 4. No forms shall be removed prior to approval of the Owner's Engineer or local building officials.

Prior to or after removal of forms, curing shall continue for the period of time shown in Table 4 for the expected exposure, or for 7 days, whichever is greater.
Inspection and Patching
Immediately after form removal, all exposed concrete surfaces shall be inspected for defects. Results of this inspection shall be recorded on EP 4-3-2C.
(*)Fins, honeycomb, and other defects shall be repaired before the concrete is dry, in a manner approved by the Owner's Engineer.
The patching material shall match the color of the original concrete as closely as possible. One third of the gray cement may be replaced with white Portland cement to help in getting a color match.

9.0 TABLES

TABLE 1 RECOMMENDED SLUMPS

Types of Construction	Slump in inches	Slump in inches
	Max. (1)	Min.
Exposed Roof Slabs	2	1
Heavy Mass Construction	2	1
Pavements	3	1
Plain Footings	3	1
Reinforced Foundation Wall and Footings	3	1
Columns, Beams, Reinforced Walls, and Slabs	4	1

NOTE:

(1) (*)May be increased 1 inch for methods of consolidation other than vibration, if approved by the Owner's Engineer.

TABLE 2

MINIMUM COLD WEATHER TEMPERATURE

Air Temperature °F (°C)	Minimum Concrete Temperature, °F	Minimum Concrete Temperature, °F
	For Sections with least dimension < 12 in.	For Sections with least dimension  12 in.
30 to 40 (-1 to +4)	60	50
0 to 30 (-18 to -1)	65	55
Below 0 (-18)	70	60

TABLE 3 TESTING STANDARDS

Testing Requirements	In Accordance With
Samples	ASTM C172
Curing	ASTM C31
Strength Testing	ASTM C39
Slump Determination	ASTM C143
Air Content	ASTM C231 or C173

TABLE 4

MINIMUM AGE FOR SAFE REMOVAL OF FORMS - DAVS (2)

Construction	Probable Mean Outside Temperature After Period of Protection	Concrete Temperature During Protection	Concrete Temperature During Protection	Concrete Temperature During Protection	Concrete Temperature During Protection
Construction	Probable Mean Outside Temperature After Period of Protection	50°F (10°C)	50°F (10°C)	70°F (21°C)	70°F (21°C)
Construction	Probable Mean Outside Temperature After Period of Protection	Type of Cement (ASTM C150)	Type of Cement (ASTM C150)	Type of Cement (ASTM C150)	Type of Cement (ASTM C150)
Construction	Probable Mean Outside Temperature After Period of Protection	I, II or V	Ill	I, II or V	lll
Pedestals, Walls, Column
and Other Vertical	Above 32°F (0°C)	2	1	2	1
(or nearly vertical)
Sections (3)
	25°F (-4°C) - 32°F (0°C)	11(1)	5(1)	8(1)	4(1)
	16°F (9°C) - 25°F (4°F)	21(1)	16(1)	16(1)	12(1)
	Below 16°F (-9°C)	29(1)	26(1)	23(1)	20(1)
Formed Grade Beams,
Elevated Slabs and	Above 32°F (0°C)	6	3	4	3
Beams, Spans 120 in.
or Less
	25°F (-4°C) - 32°F (0°C)	11	5	4	3
	16°F (-9°C) - 25°F (-4°C)	21	16	16	12
	Below 16°F (-9°C)	29	26	23	20
Spans Larger than 120 in.	Above 32°F (0°C)	20	14	20	14
Spans Larger than 120 in.	Below 32°F (0°C)	28	28	28	28

NOTE:

Forms may be removed at two days for concrete using Type I, ll or V Cement. However, curing protection must be continued for the period shown for the expected condition.
A day shall be defined as a full 24-hour period.
(*)When approved by the Owner's Engineer, forms may be removed in less that the time specified in this section if the concrete (0.50 maximum water-cement ratio) has achieved forty-percent of its specified 28-day compressive strength. To establish the time at which forty-percent of the 28-day strength is achieved, compressive strength tests shall be performed in accordance with ASTM C39 and the following procedure:

(*)ESTABLISHING FORM REMOVAL TIME

STEP 1: Perform a minimum of two compressive strength tests at each of the following time periods since casting (minimum of 6 total tests):

Type of Concrete	Time after Casting (hours)
Normal, Type I or concrete with water- cement ratio < 0.5	24, 36 and 48
High Early Strength, Type III or concrete with water-cement ratio < 0.5	12, 18 and 36

STEP 2: Approximate the time required to achieve forty-percent of the 28-day compressive strength by least squares curve fitting of the data from Step 1. The data and all calculations shall be recorded in a format acceptable to the Owner's Engineer.

STEP 3: Round the time obtained in Step 2 to the next highest hour.

STEP 4: Perform two compressive strength tests at the time after casting obtained in Step 3.

STEP 5: If these tests indicate less than forty-percent of the 28-day compressive strength, add these data points to others obtained in this analysis and repeat Steps 2 through 4.

Otherwise, report this time as the minimum age for safe form removal.

NOTE: When using a concrete mix for which there is substantial field experience and data equivalent to what is required in this procedure, additional testing is not required.

TABLE 5

DOCUMENTATION REQUIREMENTS FOR CONCRETE CONSTRUCTION REQUIREMENTS PER EP 4-3-2

Item	Description	Format	As-Built
1	Laboratory and field test results.	Text	N/A
2	Field inspection results.	Text	N/A
3	Data and calculations used to determine alternative minimum formwork removal time.	Text	N/A

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