Sikasil®-728 NS
Sikasil®-728 NS is a non-sag, 1-component, ultra-low modulus, elastomeric, neutral cure silicone sealant.
- Very high movement capability
- Very good adhesion, especially to concrete
- Very long service life due to outstanding UV resistance
- Very good flexibility for use in extremely high and low temperatures
- Resistance to jet fuel and road salts
- Non-sag, can also be used in vertical joints
Usage
Sikasil®-728 NS is designed to seal saw cut and expansion joints in concrete pavements on highways, airports, bridges, walkways, parking garages, and driveways. Suitable substrates for Sikasil®-728 NS are concrete, steel, glass, aluminium, masonry, brick and natural stone.Advantages
- Very high movement capability
- Very good adhesion, especially to concrete
- Very long service life due to outstanding UV resistance
- Very good flexibility for use in extremely high and low temperatures
- Resistance to jet fuel and road salts
- Non-sag, can also be used in vertical joints
Packaging
858 ml (29 fl. oz.) cartridge, 12 cartridges per box
600 ml foil pack, 20 foil packs per box
17 L (4.5 US gal.) pail
197 L (52 US gal.) drum
Colour
Limestone, charcoal gray
Product Details
APPROVALS / STANDARDS
- ASTM D 5893 Type NS
- ASTM C 920, Type S, Grade NS, Class 100/50, Use T2, NT, M, G, A, O
- TT-S-00230C, Type II, Class A
- US Federal Specification SS-S-200E Flame Resistance (section 4.4.12)
- FAA AC 150/5370-10G Item P-605
Chemical Base
Neutral cure silicone
Shelf Life
Sikasil®-728 NS has a shelf life of 12 months from the date of production, if it is stored properly in undamaged, original, sealed packaging, and if the storage conditions are met.
Storage Conditions
Sikasil®-728 NS shall be stored in dry conditions, protected from direct sunlight and at temperatures between +5 °C and +25 °C (+40 °F and +80 °F).
Density
| ~1.30 kg/l | (ISO 1183-1) |
Shore Hardness
| ~50 (Shore OO after 21 days) | (ASTM C 661, ASTM D 2240, ISO 868) |
Shore A Hardness
| ~10 (after 21 days) | (ASTM C 661, ASTM D 2240, ISO 868) |
Tensile Strength
| ~1.20 MPa (175 psi) | (ASTM D 412) |
Tensile stress at specified elongation
| ~0.24 MPa (35 psi) at 100 % elongation ~0.30 MPa (45 psi) at 150 % elongation | (ASTM D 412) |
Adhesion in Peel
| ~7 N/mm (40 lbf/in) on mortar substrate | (ASTM C 794) |
Movement Capability
| +100 % / −50 % | (ASTM C 719) |
Chemical Resistance
Sikasil®-728 NS is resistant to water, road salts, seawater, diluted alkalis, cement slurry and water dispersed detergent.
Sikasil®-728 NS is temporarily resistant to jet fuel spillage.
Sikasil®-728 NS is not resistant to alcohols, organic acids, concentrated alkalis and acids and chlorinated hydrocarbons.
Resistance to Weathering
| 0 (no cracks) | (ASTM C 793) |
Service Temperature
−60 °C min. / +175 °C max. (−80 °F min. / +350 °F max.)
Joint Design
The spacing between joints and joint dimensions must be designed to suit the joint movement required and the movement capability of the sealant. The joint width shall be ≥ 6 mm (1/4 inch) and ≤ 25 mm (1 inch). The joint depth shall between 0.5 and 0.8 of the joint width (width:depth ratio of 2:1 – 1:0.8) but always ≥ 6 mm (1/4 inch) and ≤ 13 mm (1/2 inch). The joint shall be recessed half of the joint width but always ≥ 10 mm (3/8 inch). For larger joints, please contact Sika technical service.
Standard joint dimensions for joints between concrete elements
| Joint width [mm] | Joint depth [mm] | Recessed below surface [mm] |
| 6 | 6 | 10 |
| 10 | 6 | 10 |
| 15 | 8 | 10 |
| 20 | 10 | 10 |
| 25 | 13 | 13 |
| Joint width [inch] | Joint depth [inch] | Recessed below surface [inch] |
| 1/4 | 1/4 | 3/8 |
| 3/8 | 1/4 | 3/8 |
| 1/2 | 1/4 | 3/8 |
| 3/4 | 3/8 | 3/8 |
| 1 | 1/2 | 1/2 |
All joints must be correctly designed and dimensioned in accordance with the relevant standards before their construction. The basis for calculation of the necessary joint widths are the type of structure and its dimensions, the properties of the adjacent building materials and the joint sealing material, as well as the specific exposure of the building and the joints.
Application
Backing Material
Use closed cell, polyethylene foam backing rods 25 % larger than the joint width. If the joint depth does not allow for a backer rod, use polyethylene bond breaker tape to prevent three-sided adhesion.
Sag Flow
| 0 mm (0 in) | (ASTM D 2202) |
| 0 mm (0 in) non-sag | (ASTM C 639) |
Ambient Air Temperature
+5 °C min. / +40 °C max. (+40 °F min. / +100 °F max.),
min. 3 °C (5 °F) above dew point temperature
Substrate Temperature
+5 °C min. / +40 °C max. (+40 °F min. / +100 °F max.)
Sealants should be installed when substrates are at mid-range of their anticipated movement.
Curing Rate
| ~3.5 mm/d (23 °C (73 °F) / 50% r.h.) | (CQP 049-2) |
| ~1/16 in/d (23 °C (73 °F) / 50% r.h.) | (MNA Method) |
Skin Time
| ~20 min (23 °C (73 °F) / 50 % r.h.) | (ISO 019-1, MNA Method) |
Tack Free Time
| ~35 min (23 °C (73 °F) / 50 % r.h.) | (ASTM C 679) |
SUBSTRATE PREPARATION
The substrate must be clean, dry, sound and homogeneous, free from oils, grease, dust and loose or friable particles. Paint, cement laitance and other poorly adhering contaminants must be removed. Sikasil®-728 NS adheres without primers and/or activators.
However, for optimum adhesion and critical, high performance applications, highly stressed joints, extreme weather exposure or water immersion, the following priming and/or pre-treatment procedures shall be followed:
Porous substrates
Concrete shall be primed with Sikasil® Primer-2100 or Sika® Primer-3 N applied with a clean brush. Before sealing allow a flash-off time of > 30 minutes (< 8 hours).
Non- porous substrates
On aluminium, anodised aluminium, stainless steel and galvanised steel, Sika® Aktivator-205 shall be applied using a clean towel. Before sealing allow a flash-off time of > 15 minutes.
For detailed advice, please contact Sika technical service.
CLEANING OF TOOLS
Clean all tools and application equipment immediately after use with Sika® Remover-208 and/or Sika® TopClean T. Once cured, residual material can only be removed mechanically.