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CONSTRUCTION AND SEALING OF JOINTS IN CONCRETE PAVEMENT

By

Mr. Tha Kyaw Zan * & Mr. Tirtha Chandan Patra **

* Senior Pavement Expert, Louis Berger Group Inc, USA ** Manager(Tech), NHAI, Berhampur

CONTENTS

1. Introduction 2. Jointing Systems of Concrete Pavement 3. Selection and Application of Joint Sealing Materials in Concrete Pavement 4. Common Problems and solutions in Joint Sealing Application 5. Conclusions

SYNOPSIS

The joints play an important role in the performance of concrete pavements. The failures of concrete pavement can be attributed mainly to failures at the joint, as opposed to inadequate structural capacity. Satisfactory joint performance depends to a large extent on satisfactory joint design, construction and sealing procedures. Otherwise distresses that may result in concrete pavement from joint failure include faulting, pumping, spalling, corner breaks, blowups, and mid-panel cracking etc.. This paper makes an attempt to provide an insight into the significance of providing joints in concrete pavements, its proper construction and sealing procedure. The common problems encountered during the construction and sealing of joints along with its resolution mechanism for a durable performance of the concrete pavement is also elaborated.

1. INTRODUCTION Joints in concrete pavement are primarily provided to control the cracking resulting from induction of stresses due to variations in temperature and moisture in freshly laid cement concrete pavement. Concrete is subject to changes in dimensions due to variations in temperature and moisture which cause it to warp, expand and contract. If these changes are entirely resisted, such high stresses may be induced in the fresh pavement so as to cause the concrete to develop tension cracks or buckling under compressive stresses may occur. Therefore joints are primarily provided in concrete pavement in order to keep these stresses within safe limits, thereby conserving the strength of the concrete to resist the stresses induced by the traffic loads. Joints are also required to be provided to facilitate a break in construction at the end of day’s work or for any interruptions in progress of work. Joints are also necessary to allow construction of the pavement in lanes of convenient widths depending upon the total width of carriageway, the production capacity of the batching plant and the paving machine.

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The construction of joints should receive maximum importance at all stages i.e . Joints Design, Joints Construction and the Joints Sealing because these play important roles for the life and riding quality of the concrete pavement. Particularly, the joint cutting and joint sealing plays the major role for governing the riding quality, performance and the durability of the newly paved concrete pavement. There are several types of sealant materials for the concrete joint sealing. It is very important to select the correct sealant material which will be suitable to the conditions of the project, use the correct methodology for the application of sealant material. The durability of the sealant material in joint may depend on the experience of the applicator. If due care is taken during the construction and sealing stages of the joints, it will result in good performance concrete pavement with high durability and less maintenance cost.

2. JOINTING SYSTEMS OF CONCRETE PAVEMENT Jointing systems for concrete pavement are designed to ensure the structural capacity and riding quality of the pavement at the lowest annual maintenance cost. Joints control the transverse and longitudinal cracking those results from restrained contraction or the restrained warping or combined effects of both and traffic loads. They divide the pavement into practical construction increments, delineate traffic lanes and accommodate slab movements. They also provide some load transfer between slabs. 2.1. Joints in Plain and Reinforced concrete roads Joints can be divided broadly into two types. Longitudinal joints which are parallel to the centre line of the road and Transverse joints which are right angles to the centre line which are of three types, namely Contraction joint, Construction Joint and Expansion joint. The basic functions of these joints are as follows:

Longitudinal joint: These joints also called as Warping joints are provided along the longitudinal direction to prevent warping of the concrete slab due to temperature and subgrade moisture variation.

Contraction joint: These joints are provided along the transverse direction to take care of the contraction of concrete slab due to its natural shrinkage.

Construction joint: These joints are provided whenever the construction work stops temporarily.

Expansion joint: These joints are provided along the transverse direction to allow movement (expansion/ contraction) of the concrete slab due to temperature and subgrade moisture variation.

These joints could be extended to the full or partial depth of the slab as per design. Sometimes iron bars are provided across the joints, the iron bars along the longitudinal joints are called tie bars and along the transverse joints are called dowel bars. For satisfactory performance of the concrete pavement the following major functional requirements of joints are required to be considered:

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i) A joint must be waterproof at all times: Surface water which is entered through a joint will weaken the subgrade design load resistant. If the underlying soil in the embankment is of clayey type, the pumping may occur. This criteria clearly emphasizes the importance of the selection and installing of the most durable sealing materials in joints. ii) Free movement of the slabs at the joint must be permitted at all times: The selection and the application of the correct type Filler and Sealing materials and correct pouring method are important for fulfilling this criteria . Both the materials must be capable to resist the repeated expansion and contraction of the concrete. Most of the defects in the expansion joints are occurred by the entry of the foreign materials get between the slabs joints. It will prevent to the free expansion of the concrete which will increase the stresses in the concrete and subsequent spalling of the edges.

iii) Joints should not form a deterrent to the Riding Quality of a road carriageway: Improper design and/or construction can result in excessive relative deflections of adjacent concrete slabs and also provides a bad riding quality. The incorrect selection of the type of the sealant materials and its application may push off the sealing material above the level of the surface of carriageway causing continuous series of impacts by the traffic and thus causing an irritating experience to the road users.

iv) A joint should not be the cause of an unexpected, undersigned structural weakness in a pavement: Transverse joints on either side of the longitudinal joint should not be constructed in staggered positions because transverse cracks will be induced in the slabs in line with the staggered joints. Furthermore, no joint should be constructed at an angle of less than 90 degrees to an adjacent joint or edge of the slab unless it is required as part of the design.

v) Joints should interfere as little as possible with the placing of the concrete pavement: The numbers of construction/expansion joints should be provided as less as possible. The bad workmanship of the construction/expansion joints will form surface irregularities which result an uneven surface profile giving a bad riding quality to the road user. An economical concrete road construction is facilitated by using the simplest types of joints providing as less numbers as possible, consistent with the structural design of the pavement.

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Fig.1 shows some typical joint configurations.

(a) Expansion joint with dowel bar (b) Contraction joint as dummy joint

(c) Contraction joint with dowel bar (d) Longitudinal joint as plain butt joint

(e) Longitudinal joint with tie bar (f) Tongue and groove longitudinal joint

Fig. 1 Some typical joint configurations. 2.1.1. Longitudinal Joints Longitudinal joints are required in concrete pavement to control the irregular longitudinal cracks which would occur as a result of thermal warping and loading stresses. It is also designed to match with the paver available paving widths. Longitudinal joint locations along wheel tracks should always be avoided. Longitudinal joints should coincide with pavement lane lines whenever possible, to improve traffic operations. For widths upto 4.5m of concrete pavement have performed satisfactorily without any longitudinal joints. Load transfer at longitudinal joints is achieved through aggregate interlock. However, these joints should be tied with tie bars to prevent lane separation and/or faulting. The tie bars should be mechanically inserted and placed at mid-depth. They are not designed as load transfer devices, but only to withstand the tensile stresses. The maximum tension in the tie bar across any joint is equal to the force required to overcome the friction between pavement and subgrade/sub-base from the joint under consideration, to the nearest joint or free edge.

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The area of steel required per/m length of joint is calculated by formula:

At = ( d x f x w ) / Ws _____________________( 1)

Where At = Area of steel required per/m length of joint in sq. cm. d = distance between the joints or joint and free edge in m.

f = coefficient of friction between pavement slab and subgrade (generally taken as 1.5) w = weight of pavement slab in Kg/sq.m. per cm thickness (generally taken as 24 Kg/sq.m.) Ws = allowable working stress in steel Kg/sq.cm. The length of tie bar should be at least twice that required to develop bond strength equal to the working stress of the steel. L = ( 2 x Ws x At ) / (Bs x p) ______________________(2)

Where L = Length of tie bar in cm. Ws = allowable working stress in steel Kg/sq.cm. At = cross-sectional area of one tie bar in sq. cm. Bs = permissible bond stress in Kg/sq. cm. p = perimeter of tie bar in cm

The diameter of tie bar should not exceed 20mm in order to facilitate the angular wrapping movement at the joint. Further, a placing allowance of 75mm is required to be added to the above calculated length of tie bar so as to account for any inaccuracies in placement. 2.1.2. Contraction Joints The basic purpose of transverse contraction joints is to control the cracking that results from the tensile and bending stresses in concrete slabs caused by the cement hydration process, traffic loadings, and the climate. It also permits a subsequent expansion up to the original length of the paved slab. Joint opening should be protected from the entry of dirt or grit which will reduce the effectiveness of the expansion. There are two types of contraction joint namely, Butt Joints and Dummy Joints. On large concrete pavement construction for roads, the most commonly provided joint type is Dummy Joint. This type of joint induces a controlled crack. Out of few type of Dummy Joint, a groove in the top of the slab dummy joint is widely used. The proper dummy joint interval for control cracking will depend on shrinkage properties of the concrete, temperature during placing, slab thickness, sub-base or subgrade friction characteristics, and properties of the joint sealant. The amount of longitudinal slab movement that a joint experience is primarily a function of joint spacing and temperature changes and can be estimated by the following equation:

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C = FL ( Te + Se) ______________________________(3)

where: C = the expected change in slab length F = the base/slab frictional restraint factor (0. 65 for stabilized bases, 0. 8 for granular bases) . L = the slab length.

= the PCC coefficient of thermal expansion. Te = the maximum temperature range (generally the temperature of the concrete at the time of placement minus the average daily minimum temperature) . Se = the shrinkage coefficient of concrete.

Designers commonly recommend a joint spacing of 4.5 meters. Random joint spacings have been successfully used in plain undoweled pavements to minimize resonant vehicle responses. When using random joint spacings, the joints may be spaced using a spacing of 3.9m – 4.5m – 4.2m. . Similarly, skewed joints with a skew of 1 in 6 have been used in plain pavements to provide a smoother ride so that the inside wheel crosses the joint ahead of the outside wheel. Only one wheel crosses the joint at a time, which minimizes vehicle response and decreases stresses within the slab. Skewed joints are generally used when load transfer devices are not present.

The recommended Transverse Contraction Joint widths are shown in Table-1. T A B L E 1

TRANSVERSE CONTRACTION JOINT WIDTHS SPACING OF JOINTS JOINT WIDTH

4.5 m (15’) 10mm 6.1 m (20’) 12mm 9.1 m (30’) 12mm 12.2 m (40’) 16mm 15.2 m (50’) 25mm 18.3 m (60’) 32mm

Load transfer across the transverse joint can be developed by few methods but the most effective and common use method is by the addition of mechanical devices across the joint, such as Dowel Bars. The purpose of dowels is to transfer loads across a joint without restricting joint movement due to thermal contraction and expansion of the concrete. It placed at the mid-depth in the slab to resist the shear as loads cross the joint and thus help to reduce the deflections and stresses at the joint. The dowel bar is designed primarily to prevent crushing of the concrete below the dowel bar. High concrete bearing stress can fracture the concrete surrounding the dowel bars, leading to final faulting of the slab. The maximum bearing stress between the concrete and dowel (Smax) should be less than the allowable bearing stress in concrete (Cb).

Smax = K Pt (2 + β z) / (4 β3 E I) ______________________________(4)

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where: K = the modulus of dowel/concrete interaction in kg/cm2/cm Pt = the load transferred by a dowel bar β = the relative stiffness of the bar embedded in concrete = 4√ (K b / 4 E I) E = the modulus elasticity of dowel in kg/cm2 I = the moment of inertia of the dowel in cm4 b = the diameter of dowel in cm z = the joint width in cm

Cb = Fck (10.16 – b) / 9.525 ______________________________(5)

where: Fck = the characteristic compressive strength of the concrete in kg/cm2 b = the diameter of dowel in cm

Dowels should be corrosion-resistant (be epoxy coated or stainless steel type) to prevent dowel seizure due to corrosion, which causes the joint to lock up. Studies have shown that larger dowels preferably more than 32mm diameter is more effective. The recommended details of dowel bars for various slab thickness are as shown in Table – 2.

T A B L E 2 DOWEL BAR DETAILS

Slab Thickness in mm

Dowel Bar Details Diameter in mm Length in mm Spacing in mm

250 32 450 300 300 38 450 300 350 44 500 300

2.1.3. Construction Joints Construction joints are formed when construction work is unexpectedly interrupted e.g. when the mechanical breakdown or by the onset of bad weather at the locations not normally specified by the design. The structural integrity of the pavement is best maintained by locating these joints at contraction joints location or within the third of a slab bounded by contraction joints. Where transverse construction joints coincide with contraction joints, it should be dowelled. The transverse contraction joints located between contraction joints should be keyed in and tie bars should be provided. Good construction planning ensures that end of the day joints are either contraction or expansion joints, matching with the predetermined joint positions. 2.1.4. Expansion Joints These joints are designed to provide space into which the expansion of concrete slabs can take place when the atmospheric temperature rises at the place where the

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concrete was laid. The provision of expansion joints prevent the development of compressive stresses of high magnitude which will damage the slab and result in the buckling or blow-up of slabs. Expansion joints are also necessary to provide at the locations where the concrete pavements will join with the fixed structures, such as bridge abutments or at intersections with other pavements. Current international practice is to provide expansion joints only near bridges. Good design and maintenance of contraction joints have practically eliminated the requirement for expansion joints, except near structures. 2.1.5. Construction of Joints

2.1.5.1. Placement of Concrete and Formation of Joints

Prior to start of concrete paving operation, a method statement giving minute details of sequence of operation and co-ordination between different activities and persons responsible for the same needs to be finalized between the Engineer-in-Charge of the project and the project contractor. A pre-paving meeting should be organized with all concerned and demo run should be carried out.

The lines of longitudinal joints are verified with respect to references of centre line fixed on the outer paving lines. The inner lines of the outer lanes are also re-checked after their completion to avoid from any deficiencies found in the line of the outer lanes which is the cause of wavering of longitudinal joints.

Expansion joints are constructed at the planned locations using 20 mm wide filler board with a height of its top should be 25 mm below the PQC top surface.

The locations of the contraction joints are marked on the surface of the dry lean concrete surface before the pavement quality concrete paving starts. Nails with painted head are used as reference points on either side of the outer paving lanes. After concrete paving, these points are transferred accurately on top of the constructed slab by means of plumb and long straight steel bars.

The dowel bars should be properly aligned in the dowel basket and that the dowel basket should be securely anchored in the base.

Dowels should be thinly coated with grease or other substance over their entire length to prevent bonding of the dowel to the concrete. Only a thin coating should be used, as a thick coating may result in large voids in the concrete around the dowels.

Care must be taken to ensure good quality concrete is used at construction joints, which should be same as for the remainder of the slab. The practice of modifying the mix at the joints is not advisable.

Care must be taken for adequate compaction of the concrete in the area of the joints in order to ensure a good joint performance. Load transfer across a doweled joint is greatly affected by the quality of concrete compaction around the dowels.

The placement of dowels should be carefully verified soon after paving begins. If specified tolerances are not being achieved, then an evaluation of the dowel installation, concrete mix design, and placement techniques must be made and appropriate corrections should be made to the paving process.

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When paving full-depth full-width, a mechanical pre-spreader and finishing machine in the paving train can be used to reduce drag and shear forces on the dowels.

It is very important that debris do not enter the previously sawed transverse joint reservoir. It is recommended that backer rod, tape, or other material be placed on the vertical face of the transverse joint at the edge of the pavement to prevent mortar from intruding into the existing joint.

2.1.5.2. Sawing of Joints

The sawing of transverse contraction and longitudinal joints should be a two-stage operation. The initial sawing is intended to cause the pavement to crack at the intended joint. The second sawing provides the necessary shape factor for the sealant material. This second sawing can be made any time prior to the sealant installation. However, the later the sealant reservoir is made, the better the condition of the joint face. Both sawing should be periodically checked to ensure proper depth, as saw blades tend to wear more when hard aggregate is encountered.

The timing of sawing is important. Premature sawing will cause spalling and raveling of concrete, and if sawing is late, shrinkage cracks will appear. It is of utmost importance to begin sawing as soon as the concrete is strong enough to both support the sawing equipment and to prevent raveling during the sawing operation. All joints should be sawed within 4-12 hours of concrete placement. Sawing should be done early during hot weather to prevent shrinkage cracking. Once sawing begins, it should be a continuous operation.

For transverse contraction joints, an initial sawing depth of one 3rd of slab thickness is adopted. Transverse contraction joints should be initially sawed in succession. The dimensions of the final sawing should be dependent upon the sealant type and the designed longitudinal slab movement.

For longitudinal joints, a minimum initial sawing depth of one 3rd of slab thickness is adopted. A final sawing that provides a 10mm wide by 25mm deep sealant reservoir is sufficient.

When a lengthy period is anticipated between the initial sawing of the joint and the final sawing and sealing, then the joint should be filled with a temporary filler. This filler material should keep all debris out of the joint.

2.1.6. Causes of the Joint failure in concrete pavement A concrete pavement joint is sealed to protect from the entry of the debris or water. If the joint seal fails, the pavement serviceability will be affected by the surface damages e.g. forming cracks and spallings. If a formed joint fails to transmit the load by means of keys, dowel bars, faulting may occur at the concrete pavement surface and will affect to the riding quality. If joint dowels do not accommodate properly at the saw cutting joint opening and closing the movements, the expansion movements formed during the hot season can concentrate stress at the dowel bars and it may lead to spalling

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at the joints and the contraction movements of the of the concrete pavement can cause cracks in concrete surface. If the joint system fails to prevent the pavement expansion stress then two adjacent concrete slabs may lock and lift or blow-up the joint.

3. SELECTION AND APPLICATION OF JOINT SEALING MATERIALS IN

CEMENT CONCRETE PAVEMENTS 3.1. Joint Fillers and Seals Joint sealants can be divided into two main groups, namely, Field-moulded sealants and Preformed sealants. Field-moulded sealants are the ones which are poured or gunned down in a liquid or semi-liquid form and take up the shape of the reservoir. They will include hot and cold applied thermoplastics and thermosetting sealants. Preformed compression sealants are often cellular in cross section and the cells are designed to collapse as adjacent slabs expand. When selecting a type of joint sealant material, information should be sought not only to the initial cost of the material but also need to find out about the durability and the maintenance technique. It should be chosen to match with the local weather conditions, the traffic capacity and the design life of the pavement. Filler boards are used to provide the gaps for expansion joints during the construction time also to provide support for the sealing compound. Filler board materials should be capable of being compressed without extrusion and sufficiently elastic to recover its original thickness when the compressed force is released. It should be retained these properties throughout the design life of the pavement. The details of sealing of different types of joints is shown in Fig.2.

Fig.2a: Sealing Details of Contraction and Construction Joint Groove

Fig.2b: Sealing Details of Expansion Joint Groove

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Fig.2c: Sealing Details of Longitudinal Joint Groove

Fig.2d: Sealing Details of Longitudinal Joint Between Cement Concrete Slabs and Bituminous Shoulder

3.2. Performance and life of Joints Regardless of the functions of joints as described before, all type of joints formed in a concrete pavement should be made waterproof at the time of construction and maintained in that way throughout the life of the pavement. Delay to prevent the debris from entering into the joints can result in the development of stresses in hot weather which are great enough to cause spalling of joint edges and in some cases, pavement buckling or blow-ups will occur. Water entering into the un-sealed joints can be the cause of pavement pumping. Therefore performance and selection of the proper sealing compound is of utmost importance. It depends upon the correct design of joints as well as the sealing compound must meet certain physical properties to ensure life and performance of the joints. 3.2.1. Correct Design of Joints

Suggestions are given by the manufacturers of the sealing compound that it is

necessary to design the groove width of joints for (Contraction, Longitudinal and Construction Joints) which should be constructed at least equal to 3 to 4 times the amount of the pavement movement at joint. For dummy contraction joints which are constructed for proper aggregate interlock to provide effective load transfer, the joint movement should not exceed 1.5 to 2.0 mm. Therefore, the spacing of contraction joints should be designed not only to maintain the aggregate interlock but also not have excessive size of the joint groove-width which will discomfort to the road users due to bad riding quality. As general rule, to meet these two conditions, the spacing of contraction joints should be designed with a limit of maximum 5 m corresponding to a joint groove width of 6 mm. The selection of the type of sealant to be used and its joint sealing procedure will be depending on the type of joints provided by the designer. As the size of the designed joint

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groove-width shall vary due to the different type of joints, it is important to the field engineers to choose and select the proper type of sealant materials for the joint sealing to the corresponding joints. Otherwise, joint sealing work will not be effectively done and re-sealing works should be executed within a unreasonable period. 3.2.2. Physical properties of sealant materials Joint sealants must meet the following requirements for the good performance and durability. They should

be impermeable. deform to accommodate the total movement and rate of movement occurring at

the joint. sufficiently recover their original properties and shape after cyclical deformations. remain in contact with the joint faces. not rupture internally. not undergo unacceptable softening at high service temperatures. not become unacceptable brittle at low service temperatures and remain elastic. not to be affected to the durability and service factors by ageing, weathering and

other environmental conditions that may occur. not become sticky or cause staining under hotter climatic conditions. have resistance to indentation and intrusion of solids. have high resistance to hardening with age. have high bonding property with adjoining concrete with or without the

application of a primer. not shrink after they have been poured. satisfy to the standard tests like bond strength, retest for bond, flow penetration

and etc. 3.3. Materials required for Joint Sealing 3.3.1. Primer The primer is used to improve the adhesive bond between sealing compound and concrete, to penetrate the pores of the concrete and to coat it with a thin film of a viscous, sticky material. Very low viscosity type of primer is required to penetrate the pores of the concrete surface. The type of primer to be used should be checked with the sealing compound manufacturer’s application manual to meet the condition that prevails at the time of application. Trial tests should be carried out on actual concrete surfaces to be sealed to ensure the optimum adhesion before the final application.

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3.3.2. Sealant Materials Various types of sealant materials for the concrete pavement joint sealing have been developed in the present time. They can be classified as Field Moulded and Preformed. There are two different types in Field Moulded such as, Thermoplastic Type and Thermosetting Type. Thermoplastic Type is the hot applied one and the materials are based on asphalt, rubber asphalt, pitches, coal tar, rubber coal tar and hot applied PVC coal tar. Thermosetting Type is the cold applied one and the materials are based on polysulphide, polysulphide coal tar, polyurethane and polyurethane coal tar. The type of sealants normally used in the concrete pavements are as follows: 3.3.2.1. Hot poured elastic type of sealants It is bituminous based sealants mixed with siliceous materials which may or may not have natural or synthetic rubber. This type of material can not satisfactorily resist either hot or cold climate. 3.3.2.2. Hot poured rubberized asphalts (Thermoplastic type) This type of sealant is improved to resist the hot and cold climates. But their resistant to indentation and intrusion of solids is not much satisfactory. However this type of sealant is better than the simple bituminous based hot poured sealants. The life span of this material may vary from 2 to 5 years. This type of sealant is suitable for joints between concrete and asphalt pavements. 3.3.2.3. Cold-applied thermosetting type of sealants This two component systems polysulphide based products are found to be excellent type of sealants for the application in joints of concrete works. As it is chemically cured after mixing the two components, once they are mixed, they should be poured within a short period before the sealant cures. It has good resistant to climatic conditions and has good bondage property. It also exhibits good resistance to indentation and intrusion of solids. It is applied with the hand gun. This type of Polysulphide sealants are relatively very expensive but it is the most favorable, reliable type and widely used in the sealing of all type of joints in the concrete pavements. 3.3.2.4. Preformed compression seals This type of seals are made of neoprene rubber. It is premoulded to the required shape and pressed into the joint groove keeping in compressed conditions. Primer is required before inserting the seals into the groove. They are generally expensive. 3.3.3. Storage of sealing material Before and during the sealing operation, sealing material shall be stored at the temperatures recommended by the sealant manufacturer.

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3.3.4. Back-up material Back-up material and joint filler installed in the joint shall be compatible with sealant and primer and of a resilient nature, such as, closed cell resilient foam, sponge rubber or a supporting type such as closed cell rigid foam, cork or non-impregnated fibre board. Materials impregnated with oil or bitumen shall not be used without first checking with sealant supplier. It is preferable to use non-impregnated materials. Size and shape shall be as indicated by joint design details on drawings. Sealant shall not adhere to back-up material and shall be as recommended by sealant manufacturer in writing to specifier. Action of slab movement on sealants and the functions of the backup materials and the de-bonding strip are shown in Fig. 3.

Fig.3a: Effect of Debonding Paper on Free Movement of Sealant

Fig.3b: Effect of Compressible Backup Material on releasing Extrusion Pressure to both top and bottom

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3.3.4.1. Types of Back-up material Suggested type of back-up materials for use with sealants are as follows:

Polyethylene closed cell foam Polyurethane closed cell foam Sponge rubber closed cell Neoprene foam rod Preformed gaskets

The final selection of the type of back-up material depends on the type of the sealant which will apply in the joint. Mainly there are two type of sealants such as Polysulphide sealant and Polyurethane sealant which are widely used. Different type of sealants uses their preferred type of back-up material. One should refer to the sealant manufacturer’s written instructions for the final selection of the type of back-up material. 3.3.5. Bond Breaker Tape Where required, it shall be polyethylene tape or as recommended by the sealant manufacturer in writing to the Engineer. 3.3.6. Solvents Solvents, cleaning agents and other accessory materials used shall be as recommended by sealant manufacturer in writing to the Engineer. 3.4. Samples and Testing of Sealant Materials The specifications of the sealant materials should be tested as per BS 5212-1990. The trial of joint sealing work should be applied at one section to see the performance of the joint sealant materials after it is trafficked. Final approval for the application of the proposed joint sealant materials should be given only after the satisfaction to the performance of the joint sealing after trafficked. The contract specification may require:

Certification by the contractor that the sealant complies with appropriate reference standard

That Field Testing and checking of joints have been sealed. That wet samples of sealant should be kept for six months after job completion.

3.5. Work prior to Sealing Joints

Examination of Joints: This will include the inspection of the size and conditions of all joints. Make a report and submit to General Contractor to all conditions which are not acceptable and acceptable. A representative person from

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the sealant manufacturer is to be present at the start of the work and periodically his present should be there to check the installation conditions.

Construction of Transverse Contraction Joint: The top portion of all transverse contraction joints, other than expansion joints should be grooved to a minimum width of 10 to 12 mm.

Construction of Expansion Joint: The width of all expansion joints shall be such that the total anticipated movement of the slabs shall not exceed the overall movement capability of the sealant.

Shape of Joint Groove: The shape of the groove shall form a rectangular or square. The depth of the groove shall be sufficient to allow the placement of at least 12 mm of sealant above the backup and bond-breaker material.

Depth to Width Ratio: The width to depth ratio (shape factor) of the sealant should be near about 1 (squarish), so that stresses (tensile stress, compressive stress, bond stress) in sealant do not reach excessive limits.

Preparation and cleaning of Joint: Joint should be sawn and clean from any debris, oil and other contaminated materials. When sealant is applied, groove surfaces should be dry and free of dirt or dust.

Making good: Where spalling of joint edges has occurred during construction work, repair works in defected joints should be carried out systematically as per the standard specifications. Further works in joints, such as , installation of sealant or continuing of paving works should not be carried out until the repairs have been completed.

3.6. Sealing of Joints

Grooves at the top of the joints which have been prepared and cleaned, shall be sealed with the selected joint sealing material. Joints shall be filled as required with the appropriate back-up material, de-bonding strip and primed with the sealant material manufacturer’s recommended primer. The space which is above the installed back-up material shall be sufficient to provide for the required sealant depth.

The application of the sealant materials in the joints should be carried out by

specialist agency recommended by the sealant supplier and the applicator must be fully conversant with manufactured sealants and their sealants.

The back-up material or bond breaker shall be placed in joint groove to allow the

placement of the sealant to a depth of at least 12 mm. The surface of which should be recessed by not less than 3 mm and not more than 6 mm below pavement surface. Debonding strip paper back (1 to 2 mm) thick is placed between the sealant and the back-up material.

The joint edges are protected with the masking tape to prevent those areas from

being spoilt by the sealant due to overfilling or smearing in windy conditions. Tape should be removed immediately after the sealant filling.

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After the joint is cleaned and back-up material is in place, the primer which is recommended by the sealant manufacturer should be applied to the faces of the joint as per the written instructions of the sealant manufacturer. Priming of the back-up material should be avoided. The time lapse between priming of joint sides and placement of sealant should be accordance with the sealant manufacturer’s written instruction. The sealing compound which is properly proportioned, mixed and applied in the field either by hand or machine accordingly by the sealant manufacturer’s written instructions shall be essentially self-levelling and completely fill the joint groove in one pass from the bottom to the top.The surface of the sealant shall be recessed by not less than 3mm nor more than 9mm below the pavement surface. The temperature requirements for applying the sealant material shall be in accordance with the sealant manufacturer’s written instructions.

The traffic should not be opened to the freshly joint sealed pavement until the sealant has adequately cool or cured not to pick up on vehicle tires. Any excess sealant material or spills should be removed from the pavement surface. All construction related signs are removed when opening to pavement to the normal traffic.

3.7. Photos of Sealing of Joints:

Application of Joint Sealing by Machine Application of Joint Sealing by Hand

Tool the sealant in the joint to level

3mm below the PQC pavement surface

Cleaning the mask tape and the excess sealant material from the

sealed joint

Final inspection in the finished sealing work

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4. COMMON PROBLEMS AND SOLUTIONS IN JOINT SEALING APPLICATION The common problems encountered in joint sealing operation and their solutions are presented here case wise. Case 1 – Sealant not adhering to joint Sl. No. Causes of Problems Solutions

1 Joint not clean enough during preparation

Clean the joint surface and reseal

2 Apply on the wet joint surfaces Allow the joint surface to dry before the application

3 In hot applied sealants type due to low sealant application temperature

Heat up the sealant materials in the melter – pourer to the correct temperature or verify the temperature gauges in the melter – pourer machine

4 In cold ambient temperature Allow the ambient temperature to raise up for pouring the sealant into the joint

5 Insufficient space in joint width for cold applied sealants and after the road is opening to the traffic, the traffic tires are pulling out the sealant

Keep the sufficient space for joint width

6 Concrete is not cured sufficiently when sealing work has done

Allow the concrete curing time sufficiently before the joint sealing operation

7 Sealant application temperature is below the dew point

Apply the sealant when the temperature is warm to above the dew point

Case II – Sealant pick-up or pull-out when opened to traffic Sl. No. Causes of Problems Solutions

1 Opened to traffic too soon after application

Refer to the sealant manufacturer’s written instructions about the full setting time of the sealant after application. Traffic should be opened only after the full setting time of the sealant

2 Sealing operation has done in high ambient temperature

Joint sealing operation should be done in cooler ambient temperature. Refer to manufacturer’s written instructions about the application ambient temperature

3 Excessive sealant application without space under the concrete top surface in the joints

Sealant should be applied with a specified space in a joint

4 Type of sealant is too soft for the particular climate

Use the stiffer type of sealant to resist the extremely hot climate temperature

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5 Due to overheated or under heated temperature sealant was applied

Apply the sealant at correct temperature as per manufacturer’s written instructions. The temperature gauge on melter machine should also be verified

6 Sealant material contaminated with solvent or mixed with heat transfer oil from leaking tank

Check the sealant material and the heat transfer oil tank

7 Concrete joint faces contaminated with old, incompatible sealant and may also cause bleeding

Re-clean the concrete joint and remove the old sealant from the joint surface

8 Pre-formed sealant installed too high in joint

Keep sufficient space in a joint under the concrete top surface during the sealant application

Case III - Sealant gelling in melter Sl. No. Causes of Problems Solutions

1 Sealant overheated in melter Check and verify the temperature gauges in melter

2 Sealant reheated too many times Use the fresh sealant 3 Using sealant with short pot life Change the type of sealant with longer

pot life Case IV – Sealant cracking or debonding in winter Sl. No. Causes of Problems Solutions

1 Applied sealant is too stiff at low temperature

Use the type of sealant which is more extendible at low temperature.

2 Poor cleaning the joint during sealant installation

Improve the joint cleaning during preparation

3 Sealing operation has done during hot summer when the joint widths are at their narrowest gaps

Avoid executing the sealing operation during the extremely hot temperatures

4 Joint width is too narrow for the movement experienced in concrete pavement

Provide wider joints width

5 Joints spacing are too long Provide the closer joint spacing 6 Incorrect joint configuration.

Sealant installed too thick or too thin in a joint

Apply the correct depth to width ratio as specified

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Case V – Voids or bubbles formed in cured sealant Sl. No. Causes of Problems Solutions

1 Due to high temperature and moisture in the pavement when sealing operation has done

Sealing work should be done in cooler periods and allow the concrete pavement sufficient time to dry or cure before the sealing operation

2 Damaging of backer material It may be melting with the hot applied sealants. Use the heat resistant backer material and check for proper sealant temperature during the sealing operation

3 Backer rod punctured and damaged during installation

Install the backer rod cautiously without damaging

4 Due to top to down sealing sequence which can trap air at the bottom

Apply the sealant from bottom to up sequence which will avoid from trapping air at the bottom

5 Air entering the sealant pumping pipe lines

Tighten all the connections at the pipe lines or bleed off the entrapped air

6 Moisture content high on backer material due to early installation before the sealing work can starts

Replace the high moisture backup material with a new dry one

7 Sealant applied on the primer surface which was not properly cured

Allow the primed surface fully cured before the sealing application

Case VI – Sink holes in sealants Sl. No. Causes of Problems Solutions

1 Sealant material flowing through the gaps formed in backer material

Use the larger backer material, reapply the sealant at the top surface to correct the level or use the non-sag type sealant

2 Backer material fixed in the joint is melting when pouring the hot-applied sealants

Use the heat-resistant type backer material

Case VII – Cold-applied sealants not setting up Sl. No. Causes of Problems Solutions

1 Sealant material shelf life is expired

Use the fresh manufactured date sealant material

2 Incorrect proportion mixing of two component sealants

Correct the proportion of mixing the two component sealants and the mixing system. Refer to the sealant manufacturer’s written instructions

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The different types of deficiencies which occur in the concrete pavement joint sealants are shown in Fig. 4.

4a) Bond Breakage due to inadequate quantity of sealant

4b) Faulty sealing procedure has resulted in air bobble embedded in the sealant

4c) Without a debonding strip the lower fiber has started to crack

4d) Harder variety of sealant has cracked in cold season

4e) Sealant filled upto brim is bulging out during expansion of slabs

4f) Overfilled sealant has caused bumpy joint

4g) Improper placement of debonding tape has resulted in leakage of sealant inside the groove

4h) Embedded stone is causing spalling of concrete

5. CONCLUSIONS The life and durability of concrete pavement depends upon the life and durability of joints. The failure of concrete pavement starts mainly from the failure of joints. Therefore design construction and proper sealing of joints for water and debris impermeability as well as to allow for the designed contraction and expansion is of vital importance. Since design of joints is more or less standardized, the correct supervision during construction and sealing of joints is very important. This is more so as a variety of sealant materials with varied properties are now available in the market. The correct selection and proper application of sealant material holds key to the life of concrete pavement. This also reduces the joint maintenance cost which forms a good component of the overall maintenance cost of concrete pavement. This technical paper includes all the stages which should be done properly as per the design criteria, joint construction method and the correct sealing procedure as per the manufacturer’s manual. Proper curing and setting time of the sealing material should be counted as the important role for the good sealing job.

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REFERENCES

1. IRC:15-2002, “Standard Specifications and Code Practice for Construction of

Concrete Roads”, Indian Roads Congress, New Delhi. 2. “Handbook on Cement Concrete Roads”, Cement Manufacturers Association, New

Delhi. 3. Flaherty, C. AO.,”Rigid Pavements Design and Construction”. 4. “Joint Sealing Portland Cement Concrete Pavements”, U.S. Department of

Transportation, Washington DC, USA. 5. “Suggested Sealant Specification Guide (ROADS)”, Thiokol Chemicals Limited,

Conventry, England. 6. Technical Advisory on “Concrete Pavement Joints”, U. S. Department of

Transportation Federal Highway Administration, 1990. 7. Design & Construction of Concrete Pavements, NITHE, New Delhi. 8. IRC:58-2002, “Guidelines for the Design of Plain Jointed Rigid Pavements for

Highways”, Indian Roads Congress, New Delhi. 9. “Concrete Pavement Design, Construction and Performance”, Norbert Delatte, Taylor

& Francis, London.