How to Weld Waterstop — PVC and TPV

Video demonstrates the proper welding techniques for welding PVC and TPV waterstops. Full link here.

Hydrophilic Waterstops

 

The term hydrophilic means “water-loving.” A good example is a sponge that absorbs water (or other polar fluid) and swells. At their most basic level, hydrophilic waterstops absorb moisture, grow in size, and seal the concrete construction joint.

Hydrophilic waterstops sell in rolls or strips. The profile is usually a small rectangle or trapezoidal shape, with 3/4” x 1” being somewhat standard. These strips are adhered to existing concrete using an adhesive or primer, or alternately concrete nails at 12” on-center spacing. This adhesion is essential, as only three sides of the waterstop get exposed to fresh concrete. If the waterstop displaces during the concrete pour, it can quickly lose most of its effectiveness. 

Commercially available for several decades, hydrophilic waterstops have long track records, albeit not always positive. Take great care at the specification level to ensure your project meets this range of product’s relatively narrow application scope.

Hydrophilic Waterstops — The “Pros”

The most significant advantage of hydrophilic waterstops is their ease of installation — the products get glued in place at the cold joint, and concrete is then cast on top of them (the second pour). The installation efficiency of this class of products makes them a favorite amongst contractors in the field.

Another “pro” is their relatively low cost. At the time of publication, a “typical” sodium bentonite-based waterstop is approximately $2.00 per linear foot, and a “typical” chemical-modified chloroprene rubber waterstop is $6.00 per linear foot. When combined with the low labor cost, strip-applied hydrophilic waterstops are time and money savers.

Hydrophilic Waterstops — The “Cons”

To read the manufacturer’s product literature, you would think they are indeed the perfect waterstop product. Cheap and easy to install, high head pressure-resistant, and low material cost. These products are not the panacea the manufacturers claim, and the essential information concerning their use is often not published. For instance, a leading manufacturer of hydrophilic waterstop states the following minimum requirements on their datasheet:

1. 8-inch thick concrete or greater
2. A double row of reinforcing steel
3. 3,000 psi concrete or greater
4. 3 inches of concrete coverage on all sides of the waterstop (minimum)
5. Non-moving construction joints only

These requirements seriously limit the project designer. Few concrete projects consist of just construction joints, and eight-inch thick concrete is rare in residential and light commercial construction. The first four prevent the hydrophilic reaction (waterstop swelling in the presence of water) from cracking or blowing out the concrete. The leading manufacturer of bentonite-based waterstops includes 75% sodium bentonite into the manufacture of their product. This high bentonite concentration allows the product to rapidly swell when exposed to water and quickly seal the joint. However, this high concentration of bentonite can also create problems such as concrete cracking or even the potential of blown-out joints due to the internal pressure of the rapidly expanding waterstop and the low tensile strength of uncured concrete.

Another limitation is the product’s inability to swell as intended in fluids other than water. All of the commercially available hydrophilic waterstop products have published data for swell ratios; however, this data is for potable water (often distilled) and saltwater. Since the products need to swell to seal the concrete joint, a designer for a non-water facility (such as secondary containment of petroleum products) can not specify hydrophilic waterstops with confidence as they will not swell as intended and may deteriorate. The American Concrete Institute recommends against using hydrophilic waterstops for fluids other than water (ACI 350.2R-04).

Hydrophilic Waterstops — Butyl/Bentonite

The first hydrophilic waterstops sold commercially were a mixture of clay and rubber. Sodium bentonite clay is the hydrophilic component of the product. Butyl rubber serves as the cohesive, tacky base. 

Bentonite-based hydrophilic waterstops are susceptible to product disintegration over the long term, especially when the moisture or saturation conditions are cyclical. The continual expansion/shrinkage/re-expansion causes the products to break down, and the bentonite migrates from the butyl rubber, leaving a smaller, cracked, non-expandable product.

Waterstop products containing less bentonite are less likely to break, blow out the concrete joint, and are less likely to break down over time from bentonite migration. However, they also swell slower and less volumetrically. Reduced bentonite waterstops should not be used in saltwater as their hydrophilic reaction is limited.

Sodium bentonite-based hydrophilic waterstops are still commercially available today. However, their use has diminished by the advent of chemically modified chloroprene waterstops that provide the required hydrophilic expansion with water, without the degradation and breakdown of the natural clay product.

Hydrophilic Waterstops — Modified Chloroprene Rubber (MCR)

Not all hydrophilic waterstops use bentonite clay as their hydrophilic agent. Modified chloroprene rubber waterstop is 100% rubber and contains no bentonite. MCR waterstops are chemically modified to swell in water*, but not to the point of disintegration, eliminating the wet/dry cycling problem that affects the bentonite-based waterstops. MCR waterstop holds up much better over time. Other product features make chemically modified chloroprene waterstops the right choice for a variety of applications. However, this class of hydrophilic waterstop also suffers from many of the same weaknesses as the more inexpensive bentonite-based waterstop products — Namely, the inability to swell in fluids other than water, slow swell time, and the lack of expansion and contraction joint functionality.

* All of the commercially available hydrophilic waterstop products have published data for swell ratios; however, this data is for potable water (often distilled).

Contact David Poole for Waterstop Assistance

 Need assistance with waterstop specification or installation? I'm here to help.

Waterstop plays a critical role in the integrity of concrete structures. Waterstop provides a fluid-tight diaphragm when embedded in, and running through concrete joints. Earth Shield® Thermoplastic Vulcanizate Waterstop (TPV) (aka TPE-R), by J P Specialties dramatically expands the scope of conventional waterstop by offering unmatched chemical resistance to a broad spectrum of aggressive chemicals, solvents, and hot petroleum oils. Manufactured NSF 61 certified, EPA-compliant waterstop profiles are available for new construction and retrofit, as well as the necessary tools and accessories for proper installation.

JPS on Facebook at www.facebook.com/waterstop

 Please "like" our Facebook company page at www.facebook.com/waterstop

How to Install W1/2 CalTrans Waterstop

Installation methods for Earth Shield® Waterstop (CalTrans W1/2 part no. 701)

 

Waterstop Selection Diagram

 

Preformed Plastic Adhesive Waterstop (PPAWs) and Federal Specification SS-S-210A

Earth Shield® Type 10 Mastic Waterstop is certified for use in Federal Specification SS-S-210A.

                                          SS-S-210A 

                                         July 2, 1975

                                         SUPERSEDING

                                         Int. Fed. Spec. SS-S-00210 (GSA-FSS)

                                         July 26, 1965

                            FEDERAL SPECIFICATION

  SEALING COMPOUND, PREFORMED PLASTIC, FOR EXPANSION JOINTS AND PIPE JOINTS

    This specification was approved by the Commissioner, Federal Supply

    Service, General Services Administration, for the use of all Federal

    agencies.

    1.  SCOPE AND CLASSIFICATION

    1.1  Scope.  This specification covers a cold-applied preformed plastic

sealing compound or sealing expansion joints and tongue and groove joints of

concrete pipe culvert, storm drain and sewer pipe.

    1.2  Classification.  The sealing compound shall be of one grade and of

the following types and sizes, as specified (see 6.2).

    Type I - Rope Form.

        Sizes          Diameter         Length

                        1/2"                        2'  6"

                        3/4"                        2'  0"

                        3/4"                        2'  6'

                     1"                             2'  6"

                     1  1/2"                        2'  6"

                     1  1/2"                    3'  8"

                     1  3/4"                    3'  8"

                     2"                             3'  8"

    Type II - Flat Tape Form.

        Sizes          Thickness        Width

                        1/8"            1 1/2"

                        1/8"            3"

                        1/8"            6"

                        1/8"            9"

                        3/16"           1 1/2"

                        3/16"           3"

                        3/16"           6"

                        3/16"           9"

                        1/4"            1 1/2"

                        1/4"            3"

                        1/4"            6"

                        1/4"            9"

                        1/4"           12"

    (Lengths of flat tapes shall be 2'6", 3'8', and 4'0" for all foregoing

sizes.)

    2.  APPLICABLE DOCUMENTS

    2.1  The following documents, of the issues in effect on date of

invitation for bids or request for proposal, form a part of this

specification to the extent specified herein.

SS-S-210A

    Federal Specification:

      PPP-B-636 - Boxes, Shipping, Fiberboard.

    Federal Standards:

      Fed. Test Method Std. No. 141 - Paint, Varnish, Lacquer, and Related

                                       Materials; Methods of Inspection,

                                       Sampling and Testing.

      Int. Fed. Test Method Std. No. 210 - Road and Paving Materials, Methods

                                            of Sampling and Testing.

      Fed. Std. No. 102 - Preservation, Packaging, and Packing Levels.

      Fed. Std. No. 123 - Marking for Shipment (Civil Agencies).

    (Activities outside the Federal Government may obtain copies of Federal

Specifications, Standards, and Handbooks as outlined under General

Information in the Index of Federal Specifications and Standards and at the

prices indicated in the Index.  The Index, which includes cumulative monthly

supplements as issued, is for sale on a subscription basis by the

Superintendent of Documents, U.S. Government Printing Office, Washington, DC

20402.)

    (Single copies of this specification and other Federal Specifications

required by activities outside the Federal Government for bidding purposes

are available without charge from Business Service Centers at the General

Services Administration Regional Offices in Boston, New York, Washington, DC,

Atlanta, Chicago, Kansas City, MO, Fort Worth, Denver, San Francisco, Los

Angeles, and Seattle, WA.)

    (Federal Government activities may obtain copies of Federal

Specifications, Standards, and Handbooks and the Index of Federal

Specifications and Standards from established distribution points in their

agencies.)

    Military Standards:

      MIL-STD-129 - Marking for Shipment and Storage.

      MIL-STD-105 - Sampling Procedures and Tables for Inspection by

                    Attributes.

    (Copies of Military Specifications and Standards required by suppliers in

connection with specific procurement functions should be obtained from the

procuring activity or as directed by the contracting officer.)

    2.2  Other publications.  The following documents form a part of this

specification to the extent specified herein.  Unless a specific issue is

identified, the issue in effect on date of invitation for bids or request for

proposal shall apply.

    American Society for Testing and Materials (ASTM) Publications:

      D4    -  Bitumen.

      D6    -  Loss on Heating of Oil and Asphaltic Compounds.

      D36   -  Softening Point of Asphalts and Tar Pitches.

      D71   -  Specific Gravity of Solid Pitch and Asphalt.

      D92   -  Flash and Fire Points by Cleveland Open Cup.

      D113  -  Ductility of Bituminous Materials.

      D217  -  Cone Penetration of Lubricating Grease.

    (Application for copies should be addressed to the American Society for

Testing and Materials, 1916 Race Street, Philadelphia, PA 19103.)

    National Motor Freight Traffic Association, Inc., Agent:

     National Motor Freight Classification.

    (Application for copies should be addressed to the American Trucking

Associations, Inc., Tariff Order Section, 1616 P Street, N.W., Washington, DC

20036.)

                                     2

                                                                    SS-S-210A

    Uniform Classification Committee, Agent:

      Uniform Freight Classification.

    (Application for copies should be addressed to the Uniform Classification

Committee, Room 1106, 222 South Riverside Plaza, Chicago, IL 60606.)

    3.  REQUIREMENTS

    3.1  Description.  The sealing compound furnished under this

specification shall be produced from blends of refined hydrocarbon resins

and plasticizing compounds reinforced with inert mineral filler, and shall

contain no solvents, irritating fumes or obnoxious odors.  The compound shall

not depend on oxidizing, evaporating, or chemical action for its adhesive or

cohesive strength.  It shall be supplied in either extruded rope-form of

suitable cross-section or flat tape form and of such sizes as to fill the

joint space when the pipes are laid.

    3.2  Chemical Composition.  The chemical composition of the sealing

compound shall meet the requirements shown in Table I when tested as

specified in 4.5.

                                   TABLE I

ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

                    Components                                    Minimum       Maximum

ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

Bitumen % by weight                                               50             70

Inert Mineral Filler % by weight                               30             50

Volatile Matter % by weight                                      --              2.0

ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

    3.3  Physical properties The physical properties of the sealing compound

shall meet the requirements shown in Table II when tested as specified in

4.5.

                                  TABLE II

ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

              Property                                                  Analysis

ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

Specific Gravity @ 77 deg. F. (25 deg. C.)                           1.20 to 1.35

Ductility @ 77 deg. F. (25 deg. C.) Min.                                  5.0 cm

Softening Point @ 77 deg. F. Min.                                       320 deg. F.

Flash Point, C.O.C. Min.                                                600 deg. F.

Fire Point, C.O.C. Min.                                                 625 deg. F.

Penetration

  77 deg. F. (25 deg. C.) (150 gs.) 5 sec.                              50 to  120

ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

    3.4  Adhesion and hydrostatic pressure.  The sealing compound shall not

leak at the joints for a period of 24 hours when tested as specified in

4.5.2.

    3.5  Sag or flow resistance (vertical or overhead joint).  No sagging

shall be detected when tested as specified in 4.5.3.

    3.6  Chemical resistance.  The sealing compound when immersed separately

in a 5 percent solution of caustic potash, a 5 percent solution of

hydrochloric acid, a 5 percent solution of sulfuric acid and a saturated hydrogen sulfide solution for 30 days at ambient room temperature shall show

no visible deterioration.

    3.7  Workmanship.  Workmanship shall be in accordance with good

commercial practice for this type of commodity.

                                     3

SS-S-210A

    4.  QUALITY ASSURANCE PROVISIONS

    4.1  Responsibility for inspection.  Unless otherwise specified in the

contract or purchase order, the supplier is responsible for the performance

of all inspection requirements as specified herein.  Except as otherwise

specified in the contract or order, the supplier may use his own or any other

facilities suitable for the performance of the inspection requirements

specified herein, unless disapproved by the Government.  The Government

reserves the right to perform any of the inspections set forth in the

specification where such inspections are deemed necessary to assure that

supplies and services conform to prescribed requirements.

    4.2  Sampling.  Sampling shall be performed in accordance with Methods

101.11 and 101.21 of Interim Federal Test Method Standard No. 210 Road and

Paving Materials.

    4.3  Inspection.  Inspection shall be performed in accordance with Method

1011 of Federal Test Method Standard No. 141.

    4.4  Inspection of preparation for delivery requirements.  An inspection

shall be made to determine that the packing and marking comply with the

requirements in section 5 of this specification.  Defects shall be scored in

accordance with Table III.  The sample unit shall be one shipping container

fully prepared for delivery.  Sampling shall be in accordance with

MIL-STD-105.  The lot size shall be the number of shipping containers in the

end item inspection lot.  The inspection level shall be II with an acceptable

quality level (AQL) of 4.0 defects per hundred units.

       TABLE III.  Classification of preparation for delivery defects

ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

              Examine                                       Defects

ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

Markings (exterior and interior)             Omitted; incorrect; illegible; improper

                                             size, location, sequence, or method of

                                             application.

Materials                                    Any component missing, or damaged.

Workmanship                                  Inadequate application of components such

                                             as incomplete closure of container flaps,

                                             loose strapping, inadequate stapling.

                                             Distortion of container.

ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

    4.5  Tests.

    4.5.1  The following tests shall be made in accordance with the methods

shown in Table IV and as described hereinafter.  Each test shall be run in

triplicate and if more than one specimen fails the test, the lot represented

by that specimen shall be rejected.

                           TABLE IV.  Test methods

ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

        Test

ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

Bitumen                                                    ASTM        D4

Inert Mineral Filler                              Int. Fed. Test Method Std. No. 210

Volatile Matter                                            ASTM        D6

Specific Gravity                                           ASTM        D71

Ductility                                                  ASTM        D113

Softening Point                                            ASTM        D36

Flash Point                                                ASTM        D92

Fire Point                                                 ASTM        D92

Cone Penetration                                           ASTM        D217

ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

                                     4

                                                                    SS-S-210A

    4.5.2  Adhesion and hydrostatic pressure.  Mount a vertical column using

2 1/2 sections of 3 foot 6 inch bell and spigot or tongue and groove pipe.

Seal the 1/2 section to a concrete slab with the sealing compound and follow

with the other two sections.  Immediately fill the pipe sections with water

to obtain an approximate 6 foot head pressure.  Mount a horizontal column

using 3 sections of 12 inch to 36 inch tongue and groove pipe and apply the

sealing compound to seal the tongue and groove joints, the metal end plates,

bolts and washers.  Draw multiple pipe section together until a 1/8 inch to

3/16 inch squeeze-out is observed at all joints.  Immediately fill pipes

with water, slowly applying hydrostatic pressure in increments of 2 pounds

per square inch every minute until 10 psi is reached.

    4.5.3  Sag or flow resistance (vertical or overhead joints).  Fill a

wooden form 1 inch wide and 6 inches long flush with sealing compound and

place in an oven at 135 deg. F, in a vertical position for 5 days.

    5.  PREPARATION FOR DELIVERY

    5.1  Packing.  Packing shall be level A, B or C as specified.

    5.1.1  Level A. The compound of like description furnished in sizes,

lengths and quantities as specified (see 6.2) shall be packed in a

close-fitting box conforming to PPP-B-636, class weather resistant.  The box

shall be closed and strapped in accordance with the appendix to the box

specification.

    5.1.2  Level B The compound shall be packed in accordance with 5.1.1,

except the fiberboard box shall be class domestic and the closure shall be

in accordance with method II of PPP-B-636.

    5.1.3  Level C. The compound shall be packed to insure carrier

acceptance and safe delivery at destination in containers complying with the

National Motor Freight Classification rules or the Uniform Freight

Classification rules.

    5.2  Marking.

    5.2.1  Civil agencies.  In addition to markings required by the contract

or order, the shipping containers shall be marked in accordance with Fed.

Std. No. 123.

    5.2.2  Military activities.  In addition to markings required by the

contract or order, the shipping containers shall be marked in accordance

with MIL-STD-129.

    6.  NOTES

    6.1  Intended use The cold-applied preformed plastic sealing compound

covered by this specification is intended for sealing expansion joints and

tongue and groove concrete pipe.

    6.2  Ordering data.  Purchasers should select the preferred options

permitted herein, and include the following information in procurement

documents:

     (a)  Title, number, and date of this specification.

     (b)  Lengths, sizes and quantities of compound required (see 1.2).

     (c)  Level of packing required (see 5.1).

     (d)  whether civil or military marking is required (see 5.2).

Preparing Activity:

    GSA-FSS

ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ

    Orders for this publication are to be placed with General Services

Administration, acting as an agent for the Superintendent of Documents.  See

Section 2 of this specification to obtain extra copies and other documents

referenced herein.

                                     5

                                                         SS-S-210

                                                         REINSTATEMENT

                                                         December 16, 1981

                                                         SUPERSEDING

                                                         CANCELLATION NOTICE

                                                         October 31, 1978

                            FEDERAL SPECIFICATION

                    SEALING COMPOUND, PREFORMED PLASTIC,

                    FOR EXPANSION JOINTS AND PIPE JOINTS

    This notice as approved by the Commissioner, Federal Supply Service,

    General Services Administration.

    This notice is issued to reinstate Federal Specification SS-S-210A,

dated July 2, 1975.

    Cancellation notice dated October 31, 1978, is hereby canceled.

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Concrete Joints and Waterstop

Over its long lifespan, concrete is subject to physical changes in length, width, height, and volume of its mass when subjected to environmental changes and mechanical conditions surrounding it. The effects may be a permanent contraction from drying shrinkage, carbonation, or creep, abnormal changes from chemical reactions of sulfate or alkali attacks, or merely applying a concrete load.

As the concrete moves, it relieves the internal stresses by forming a crack. Engineer designers minimize the unsightly appearance of self-formed cracks by introducing joints into the concrete to accommodate the movement without losing structural integrity. 

Contraction joints divide large pours of concrete into smaller structural units. Contraction joints create a man-made plane of weakness to regulate and control the location of a crack formed by moisture loss of concrete. Without this formed contraction joint, the concrete would freely crack in unexpected and unattractive places.

A scheduled or unscheduled interruption of the concrete pour 30 minutes or greater creates a construction joint.

Designed to negate the compressive forces from abutting concrete structures that may occur due to expansion, loads, or differential movements, expansion joints require an actual gap between the concrete pours, filled with a compressible joint filler material such as foam, rubber, cork, or cane fiberboard.

Waterstop is a preformed joint material, metallic or nonmetallic, designed to stop the migration of fluids by creating an internal dam running across and along concrete joints.

Commercially available waterstops are either metallic or nonmetallic. Metallic waterstops possess high strength and extreme heat and cold resistance but offer little extensibility. Nonmetallic (plastic, rubber) waterstops provide flexibility rather than strength and have good extensibility, recovery, chemical resistance, and fatigue resistance.