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Tag: MS sealant

Importance of concrete expansion joints and joint sealant

What are concrete expansion joints and why are they important?  What is a concrete expansion joint? A concrete expansion joint – or control joint – is a gap which allows the concrete to expand and contract as/when the temperature changes. It forms a break between the concrete and other parts of a structure to allow movement without causing stress, which can lead to cracking. They should be used in large concrete slabs such as foundations and concrete driveways. The expansion joint shall be covered by sealant to prevent dust accumulation, water and secure a smooth drive on the surface. Normally there 2 kinds of sealant used for expansion joint namely polyurethane (PU) and modified silicone (MS sealant) sealant. PU sealant is often harder to apply, may cause bubbles (as it contains isocyanate), shrinkage (as it contains solven –  a kind of gas which evaporates during curing) and less UV resistant than MS sealant. MS Construction Sealant is a one-part, high-performance hybrid sealant that is based on advanced MS Polymer technology. It has excellent weathering, UV and temperature resistance characteristics, and with outstanding features:
  • Good Environmental Choice Australia (GECA) certified
  • ASTM C920 (Class 50) compliant
  • ISO 11600 (F Class 25 LM) compliant
  • Good UV resistance
  • Low static charge – Less dirt streaking
  • No silicone oil – Non-staining on adjacent substrates
  • No isocyanate – No air bubbling
  • No solvent – No shrinkage
  • Bonds most substrates without primer
See more here Why do you need concrete expansion joints? All concrete will shrink slightly as it dries and, when it’s set, will expand or contract depending on the ambient temperature. To prevent crack formation, concrete expansion joints should be incorporated to allow for movement, particularly in slabs with a surface area exceeding 6m2. Concrete expansion joints are particularly important where there have been consecutive concrete pours and are also useful when laying concrete within an area bordered by walls or buildings or if objects such as manhole covers need to be incorporated. If several construction joints are needed, it would be advisable for them to be designed and specified by a structural engineer.  Installing concrete expansion joints You can install concrete expansion joints before or after the concrete is laid. In the first instance, a flexible material is inserted along the length of the joint before the concrete is poured. Alternatively, once the concrete has set, grooves can be cut in the concrete, this will control where the concrete will crack leaving a neat saw cut at the surface and allow joint materials to be added where required, but care must be taken to ensure the correct depth is achieved (see below). Tips for placing concrete expansion joints
  1. Place joints around 30 times the slab thickness apart. So, for a slab which is 100mm thick, the joints should be placed around 3,000mm (3 metres) apart.
  2. Make sure joints are cut deep enough: they need to be at least a quarter of the thickness of the slab. For a 100mm slab, cut the joints at least 25mm deep. 
  3. If you’re cutting joints after the concrete has been poured, don’t leave it too long. Concrete might crack if the joints aren’t cut within 12 hours after finishing.
  4. Placing joints under walls will mean they won’t be seen.
  5. Joints are most effective when the aspect ratio of the slab is kept to 1:1, for example 5m x 5m if the slab is a narrower than it is long it is possible to increase this to a maximum aspect ratio of 1.5 for example 2m x 3m, don’t leave the placing of concrete expansion joints to chance and enlist the services of a structural engineer if several are required. 
  6. For a neat sealant edge, it is recommended to use masking tape.
  7. To better control sealant depth and avoid 3-side bonding, use backer rod.
Below is how expansion joint sealing is applied.
keo tram khe co gian MS slealant 8
masking before sealant application
keo tram khe co gian MS slealant 7
Door peremeter sealing
keo tram khe co gian MS slealant 9
Concrete expansion joint sealing
keo tram khe co gian MS slealant 6
Concrete expansion joint sealing
keo tram khe co gian MS slealant 1
Concrete expansion joint sealing
keo tram khe co gian MS slealant 11
Door peremeter sealing

MS sealant for green building

GECA green MS sealant
Construction Sealant is a one-part, high-performance hybrid sealant that is based on advanced MS Polymer technology. It has excellent weathering, UV, and temperature resistance characteristics. Ideal for sealing building concrete joints like wall panel joints, expansion joints, control joints, etc. It is also recommended for sealing window frame perimeter, metal panels and natural stone façade etc. Other common applications include sealing of anodized aluminium, finished wood, porcelain, coated metal, epoxy and polyester panels, polystyrene, UPVC, and stainless steel, is a base resin for producing quality sealants and adhesives for construction and industry. Its unique properties enable MS Sealant (the sealant based on Kaneka MS Polymers) to deliver outstanding performance, widely recognized by applicators and architects throughout the world. The inherent properties of MS Sealant can be summarized as in the next slides.

EASY HANDLING/WORKABILITY

MS Sealant is easy to use: it can be extruded from cartridges with a low force even at low temperature. A continuous flow of sealant with stable viscosity is the norm. Furthermore, smoothing and tooling of the joint are easier with MS Sealant than with any other kind of sealant
EXCELLENT ADHESION

EXCELLENT ADHESION

MS Sealants exhibit good primerless adhesion to a wide range of substrates that are commonly used in construction and industry, such as PVC, Aluminum, Glass, Steel, Ceramic, Plywood and many of the newly developed materials for construction.
WEATHER RESISTANT

WEATHER RESISTANT

The resistance to natural weathering such as rain and UV is one of the advantages of MS Sealant that allows use of the sealant outdoors ? even in adverse weather. MS Sealant shows no cracks after UV exposure. The elasticity of the sealant is maintained over time, even years after application.

HIGH-QUALITY MECHANICAL PROPERTIES

MS Sealant has excellent mechanical properties including both: stable elasticity over a wide temperature range (-40C to 100C) and long-term stability. MS technology enables formulators to customize from a very low modulus sealant with 100% modulus at 60psi, to a very high strength adhesive with lap shear strength of 1,500psi.
NON-BUBBLING

NON-BUBBLING

MS Sealant does not bubble on the surface at all. The surface of the sealant is kept smooth and intact. A constant and uninterrupted joint is easily achieved.
NON-STAINING

NON-STAINING

Excellent non-staining characteristics can be obtained with MS Sealant. Porous substrates used in construction, such as granite and marble, can be sealed with a wide range of MS Sealants with low risk of contaminating the stone surface.
PAINT COMPATIBILITY

PAINT COMPATIBILITY

Compatibility with many kinds of paint is appreciated by many users in industry and construction. MS Sealant is compatible with many types of paints and coatings. MS Sealant can immediately be painted over after application. The paint cures relatively quickly after a reasonable time.
UNIVERSAL

UNIVERSAL

MS Sealant can be used for a wide variety of applications. A single product can be used for waterproofing, bonding, sealing… and will adhere to different substrates at the same time. There is no need to buy a seperate sealant for each application.
GREEN SEALANT

GREEN SEALANT

Certificed by Good Environmental Choice Australia (GECA), no hazardous materials such as isocyanate, solvent, heavy metals etc.

Why Sealant Joints Fail: Avoiding Sealant Application Failures

Sealant failure
Sealant adhesion and cohesion failures
The sealant’s main function is to accommodate movement.  This is more easily performed if the sealant does not have to also act as weather protection.  When a sealant does form the joint’s sole weather protection then the spacing, location and sizing of the joint are even more crucial to the ultimate success of the seal. Basic guidelines for the proper application of a sealant:

1. Substrate must be clean and dry for the sealant to adhere properly.

All sealant manufacturers state this in their recommended application procedures.  When this basic rule is violated then the most common of all adhesion problems begin.  Some of the most basic clean deficiencies are:
  • Not cleaning at all
  • Using contaminated or dirty solvent
  • Using the wrong solvent for a particular sealant,
  • Allowing contaminated solvent to dry on the substrate
  • Using contaminated rags or brushes
  • Using a rag containing lint

2. Improper use of sealant.

The second most common adhesion issue is caused by the improper use of sealant and primers.  What does this mean?
  • Poor quality sealant. Now MS sealant, with innovated technology, can overcome weaknesses of PU and silicon sealant.
  • Not using the primer at all
  • Using too much primer
  • Using the wrong primer for the specific sealant or substrate
  • Not allowing the primer to dry completely before adding the sealant

3. Weather on day of application.

Temperature is key.
  • Cold temperatures causes the sealant to lose viscosity which makes it difficult to apply without gaps and voids and it will be too thick to properly tool.  Cold air may retard the cure and if the substrate has contracted due to the temperature then the joint will be wide open.  Issues occur when the substrate warms up and expands, causing the joint to close and the sealant to be squeezed out entirely.
 
  • High temperatures can cause the sealant to sag or flow out of the join resulting in failure.  Premature skinning over the sealant bead can also occur resulting in craze cracking.
 
  • Dry surfaces are imperative.  Dew, frost or any sort of precipitation will guarantee adhesive failure.  The same applies if the substrate is still damp from a previous rain.

4. Field applications that can go awry.

  • The most common is substitution of the specified product.  Many sealants look alike, but they do not perform in the same way.
  • Improper storage can cause sealants to freeze, prematurely cure, or exceed their shelf life.

5. Don’t paint your sealant!

  • Most paint will not adhere to your sealants and are not formulated nor intended to take the kind and amount of movement to which sealants are subjected.
  • If the paint does adhere it will crack when the joint moves.
  • If the paint cracks so does the sealant.

6. Joint surface detail.

  • The edges of the joint must be smooth and not jagged so the sealant doesn’t develop air pockets during installation.
  • Any mortar must be removed or cohesive failure can result.

7. Importance of backer rods.

  • Backer rods create the proper depth to width ratio, act as a bond breaker, and provide a firm surface for tooling.
  • Failure to specify an appropriate bond breaker can cause nightmares.
  • A joint with three sided adhesion will fail cohesively, adhesively or both.
  • Closed-cell backer rods should not be used with sealants that cure by reacting with moisture in the air.  These rods must also be protected from puncturing to avoid outgassing.
  • Open cell backer rods should not be used where moisture absorption into the backer rods can be a problem.
  • Backer rods are held in place by compression therefore,  the rod selection should be about 20% larger than the maximum expected joint opening.  If it is too small it will not function as intended and proper tooling will be impossible.

8. Usage of bond breaker tape.

  • Bond breaker tape should be used only where there is a firm bottom surface and when the joint is so shallow that a backer rod will not fit.
  • Tape sizing is very important.   If it is too small, three sided adhesion will result; if it is too large, the tape will wrap around the bottom and sides of the joint, eliminating some of the bonding area required for good adhesion.

9. Benefits of tooling

  • Helps protect the weather tightness of the joint by eliminating air pockets created behind the sealant during gunning.
  • Forces sealant contact with the side of the joint promoting good adhesion.
  • Sealant is pushed against the backer rod and pressed into an hourglass shape allowing it to stretch properly.
  • Without tooling, the bond area between the sealant and the sides of the joint may not be sufficient to prevent the sealant from pulling away from the sides of the joint.
 

High performance sealant for precast concrete panels

High performance MS sealant for precast concrete panels

Precast concrete wall
Precast concrete wall elastomeric joint
The successful performance of a building exterior is frequently defined by its ability to keep rain and the elements outside, away from the building’s occupants. Precast concrete panels are relatively impermeable to water. Moisture will not penetrate through precast concrete panels. The joints between precast concrete panels or between panels and other building materials must be considered to prevent water and air penetration through the building envelope. The design and execution of these joints is therefore of the utmost importance and must be accomplished in a rational, economical manner. Joint treatment also has an effect on the general appearance of the project. To ensure the joint and sealant give the desired performance, selecting the right product, appropriate joint design, and proper surface preparation and application technique is required. The penetration of moisture into a building envelope may enter directly (through an opening), by gravity, capillary action, and as a result of the mean (steady state) air pressure difference across the wall. Joint sealants are fully exposed to the major agents of aging and deterioration—ultraviolet light and thermal cycling. High performance sealants with a low modulus and high movement capability must be used to ensure quality long-term performance. In new construction, labour to material costs are typically 4 to 1, while in renovation/rehabilitation the ratio may be 8 to 1 or more. Joints are required to accommodate changes in wall panel or structure dimensions caused by changes in temperature, moisture content, or deflection from applied design loads. The joints between panels are normally designed to accommodate local wall movements rather than cumulative movements. Sealants subjected to volume change movements, either horizontally or vertically at building corners, at adjacent non-precast concrete construction, or at windows not having similar movements must be given special consideration. These intersections are a prime source of sealant problems. Sealants have grown in sophistication in recent years as the markets have grown more demanding. The emergence of new materials has spawned a range of sealant types as varied as their applications. Sealants cover a wide range of materials, from low cost oil and butyl based mastics, for use around doors and windows, to considerably more costly one and two part polyurethanes and silicones used to seal joints in high rise structures. In between is a range of other materials, all with their own unique characteristics and preferred applications. Polyurethane and silicone sealants are often referred to as “high performance” sealants in that they provide significant adhesion, movement capability, and durability. However, even these adhesives have certain disadvantages that can limit their use. Although silicone and polyurethane sealants account for nearly 70 per cent of the sealant market, hybrid construction adhesives have increased in prevalence due to their many advantages and recent improvements in performance. As a group, hybrid sealants represent only about 9 per cent of the market by volume and MS sealants represent only 1.6 per cent although they are growing faster than their more conventional counterparts. MS sealants are considered to be competitively priced with polyurethanes and oxime-cured silicones. The MS polymers have found applications mainly in sealants although they are also being used in adhesives that have high tack (acrylic modified MS) and excellent toughness and flexibility (MS-epoxy blends).
MS sealant trend
MS sealant trend
Although the use of MS sealants has been relatively slow to develop in Vietnam, they are the most used type of sealant in Japan since their introduction nearly 30 years ago. MS sealants were originally developed to solve some of the bleeding and staining issues that occur with highly plasticised sealants. With continuous improvements in weather ability, MS sealants have taken shares from both the urethane and the silicone sealant markets. The rise in MS sealant popularity has been primarily due to its versatility and well-balanced properties. MS sealants are suitable for a wide range of applications. Movement capability in construction joints is generally +/- 25 per cent which places these materials in the category of “high performance sealants”. MS sealants meet the requirements of ASTM CC920 Class 25, as well as those of Federal Specification TT-S-00230C Type II, Class A as a one-component sealant and Specification TT-S099227E Type II, Class A as a two-component sealant. MS sealants also meet ISO Standard 11600G, Class 25HM (high modulus). Compared with the other two types of sealants, MS sealants have well balanced properties and performance. we outline some of the unique properties of MS sealants are:
  • Environmental friendliness (solvent-free and isocyanate-free)
  • Low temperature gunnability: the viscosity of MS sealants is less dependent on temperature changes storage stability: shelf life is excellent although sealant must be protected from moisture
  • Weather resistance and durability: MS sealant shows no cracking, splitting, discoloration or adhesion failure after ten years of testing in desert climate
  • Stain resistance: MS sealants do not stain as some silicone sealants do because of low molecular weight silicon materials that bleed from the surface of sealed joints
  • Paintability: MS sealants provide good paintability unlike silicone sealants adhesion
Sealant painted over with water based paint
Sealant painted over with water based paint
MS sealants provide adhesion to various substrates including metals, plastics, wood, and ceramics. The MS sealants have high performance capabilities with many of the same characteristics as a urethane sealant. However, the one-part MS sealants cure much faster than a one-part urethane sealant and find use in the construction industry where property development speed is important. The skin formation (15-20 mins) occurs much faster with MS sealants than with silicones and urethanes, therefore they exhibit very little dirt pickup. They can also cure in much deeper sections than polyurethane. Perhaps the most compelling value proposition associated with MS sealants is their lack of isocyanates in the formulation. MS sealants are based on a polymer, which is already silyl-terminated, eliminating isocyanate content. The presence of isocyanates also provides a tendency for bubbling during cure. Isocyanates are considered to be hazardous materials to use. Reasonable caution must also be exerted in the use of materials containing isocyanate including adequate ventilation and prompt washing of body areas coming in contact. In recent years, MS sealant has been addressing the growing demand for advanced technology sealants, adhesive and speciality coatings in Vietnam and across the globe. Alseal have pioneered the manufacture of MS Polymer sealant for construction, infrastructure and automobile sector. In Vietnam, Vina Trade Synergy is exclusive distributor of Alseal MS sealant and silicone sealants, of which AS-4001S is an outstanding product perfectly suitable for, among other applications, precast concrete wall elastomeric joints, grc panel joint, glass reinforced concrete joint. See also hybrid jointing compound.

PU vs MS sealant | The outstanding features of MS sealant

See more: | PU vs Modified Silicone Sealant             | High performance MS sealant AS4001S

Characteristics MS Sealant PU Sealant
Chemical base Modified Silicone Polymer (hybrid, STPE) PolyUrethane
ASTM C920 compliant Yes Yes, exceeding
Tack free time <1 hour > 1 hour
Movement capability (ASTM C719) ±50% ±25%
VOC content Low VOC, GECA certified green lable for green building High
Containing solvent and Isocyanate (hazardous) No Yes
Bubbling (caused by isocyanate that reacts with moisture and generates CO2 bubbles in curing process) No Yes (the higher the moisture level, the more bubbles)
Shrinkage (recessed) after cure (caused by solvent evaporating in curing process) No Yes
Paintable Yes Yes
Damp substrate bonding Yes No
UV resistance Good Bad
Service life >10 years 3-10 years
Primerless bonding to most substrades Yes No
Storage stability/heat resistance Good Bad
Service temperature -30oC to +100oC -40oC to +70oC
Price Competitive against PU Moderate

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