Substrates and Application

Substrate preparation and types

1. For all substrates: the application surfaces must be clean. No dust, traces of other materials, paints, salts, organic growth etc... should be present.

- Concrete surfaces should be brushed and washed. Traces of materials such as building finishes should be scraped off if they are over 1/3 of the proposed finish thickness.

- Wetting/Dampening: Thermocromex must be applied on a correctly dampened substrate. As a rule the substrate should be damp on the surface. Dampening must take into account the overall substrate suction and the climatic conditions at the time of application and should be done about half hour before application. Thermocromex should be dampened in hot weather conditions, in the presence of strong drying wind and on high suction substrates. Do not apply materials over saturated surfaces (when water runs off it after wetting) or on previously waterproofed surfaces unless these have been keyed properly.

- The suction of the walls must be uniform throughout.

PRODUCT

FLEXURAL STRENGTH

ELASTICITY

DRY DENSITY

KG x m³

CAPILLARITY

g.dm².min1/2

THERMOCROMEX

> 2.5 MPa

4000 - 6000 MPa

1350 - 1550

 <  2.5

B. Application Method

There are 3 major application methods:

1. Thermocromex is easily applied with machines such as Putzmeister or any stator type pump.
2. Using a pneumatic hopper gun: all finishes should be able to be used with this method. Take care in the spraying distance and pressure to avoid greater thickness and consumption higher than necessary.
3. Manual application. Please note: Thermocromex is made for spraying and could present some "stickiness" when applied manually. 

When using spraying equipment it is essential to respect the mixing instructions of Thermocromex on the water addition and mixing time. It is also essential, as for all plastering work, that the substrate is correctly prepared.

Weatherproofing

This is achieved when the finish thickness is at a minimum of 3/8 inch (10mm). Use a depth gauge or equal to measure thickness.

Coat(s) Thickness

Do not apply in coats over 3/4 inch (20mm). If a thicker coat is required, apply in 2 or more passes at 48 hour intervals. In cold weather 40^oF (4^oC) to 50^oF (10^oC), this interval should be one week. The maximum overall thickness should not be over 1 1/2 inches (40mm).

Thermocromex over CMU and AAC Blocks/Panels

Apply Thermocromex at 3/8" thick directly over clean and properly prepared CMU block or AAC Blocks/Panels at 3/8" thick.

The suction of the walls must be uniform throughout.

Thermocromex over sheathing, lath and a scratch coat/OSC

After sheathing, lath and a scratch coat (ASTM C 926)/OCS, apply Thermocromex at a minimum 3/8" thick. Allow scratch coat to cure 7-10 days or until initial shrinkage has occured. 

On very smooth and non suction surfaces including tilt wall and poured in place concrete

Add 1 quart of SBR bonding agent (minimum solids of 48%) per 30kg bag of Thermocromex then mix per manufacturer's instructions (including colorant) reducing the water content by 1 quart. The coverage rate is 30 sq ft at 1/4 of an inch thick.

Thermocromex over ICF

After lath and a scratch coat (ASTM C 926), apply Thermocromex at a minimum 3/8" thick.

CLIMATIC CONDITIONS DURING APPLICATION

Do not apply in temperatures below 40^oF (4^oC) or above 85^oF (29^oC).

Apart from protecting the work from exposure to rain, it is important to consider hot weather, drying wind and the type of substrate.

In warm climate and in the presence of drying wind, the correct dampening of the substrate and suitable wind/rain protection is required to avoid high shrinkage.

Thermocromex should not be applied on flat surfaces with an inclination below 10 degrees.  

TYPE OF FINISHING REQUIRED

The main finishes are:

• as sprayed or rough cast
• partly smoothed roughcast
• scratched
• floated, smooth
• blended
• textured
• custom

These finishes have been specifically designed to maximize speed of application to shorten completion. Normally sprayed, they can be supplied in a range of colors using inorganic pigments (See color chart). This eliminates the need for painting or re-coloring. Thermocromex is weatherproofed, but also retains high breathability and elasticity and vibrant custom color finishes.

- When applied. Thermocromex should be immediately straightened with a straight edge or a feather edge.

- Where the humidity is less than 80%, apply a light water mist at least twice a day to adequately cure the work for 48 hours after application.

C. Protection and Curing

• Protect fresh work against adverse weather conditions.
• To avoid blooming, do not apply Thermocromex with strong colors at temperatures below 46°F (8^oC) and/or in high humidity.
• In hot weather or windy conditions, cure the work repeatedly (3-4 times daily) with light water mist for at least 2-3 days.
• Where the humidity is less than 80%, apply a light water mist at least twice a day to adequately cure the work for 48 hours after application.

Protecting Thermocromex

A very important function of Thermocromex in masonry work is to provide wind and watertight protection to walls; this is equally relevant to finish joints and to finished surfaces. Proper specification and application will ensure that the wall functions properly. It is essential therefore to ensure that new work, properly specified is allowed to cure from its wet application state into a fully functioning finish. To assist in this process adequate protection must be given to finishes during and after their application until the finish is sufficiently cured to perform its designated function.

Protection starts before the work takes place: it is important to assess the state of the structure before work commences. Strong detailing, properly installed ground drainage, roof membranes, gutters etc should all be in working order to avoid water ingress and over saturation of fresh finishes.
During and after application, protection should be in place for as long as necessary for the finish to firstly cure properly and dry out in a controlled manner. Provided Thermocromex is adequately cured, generally for the first 48-72 hours after application, it will then be possible to remove temporary screening or protection except where there is a risk of frost or freezing within 3-4 weeks from application.

The exposure of the site to adverse weather conditions is also a major consideration in the design, specification, planning and execution of the work. The principle factors are: a)Rapid drying caused by: direct sun, heat and wind over 5 mph. b)Insufficient drying caused by: excessive rainfall, low temperatures and humid/damp conditions. c) Freeze thaw expansion

Rapid drying:
If the finish dries out too quickly, hydration and carbonation will be inhibited, drying shrinkage may occur and the finish may become crumbly or brittle. Rapid drying is best avoided by screening against strong direct sunlight and provision of physical barriers to reduce wind action. A cost effective and simple method is to screen work with small sized mesh debris netting (double if necessary), strong tarpaulins or heavy-duty plastic sheeting on the outside of the scaffold.
Seasonal aggravating factors are: hot weather, warm drying wind and rain.

Insufficient drying:
If the finish dries too slowly, water held in the finish will slow or diminish the rate of initial and possibly final set, inhibit carbonation and result in a finish that is weakened. It may also be susceptible to lime migration, sufficient to cause the finish to crumble or become brittle. Protection of the wall heads and functioning drainage should be in place.

Freeze Thaw expansion:
Can only occur if the finish pore structure is saturated. If there is a danger of freezing of fresh or uncured finish, close covering with hessian or tarpaulins and if necessary additional heating should be provided. Polythene should not come in contact with fresh finish.

Planning and Budget for protection of new work:
The organization of work, particularly finishes that require careful planning as well as execution in addition sufficient resources should be included in the contract cost to provide the following. Scaffolding for all work should be capable of supporting temporary covers and project sufficiently above the works to afford protection at the wall heads or eaves. It should also allow sufficient working space for the application intended. Site storage must be available to keep materials in clean dry conditions.

* Note: Late autumn, early spring & winter working Cold wind or strong wind with low air temperature will produce wind chill effects that will significantly reduce the surface temperature of fresh finish. Due to the season and/or inadequate protection against rain or, indeed, if moisture is present due to saturated structures, the finish might not be dry enough and therefore frost damage may occur.

Rain Allowing finishes to be saturated by rain should be avoided for the following reasons:

* Over saturated finishes can result lime leaching which, in severe cases, will affect the binder ratio with negative effects on the durability of the finish. A typical example is if the finish is too sandy when rubbed.

Light and not continuous rain, provided that frost is not forecasted, will help to cure the finish and can be beneficial especially in warm spells. Heavy rain, especially if detailing is poor or wind driven will not allow the fresh finish to dry sufficiently to withstand frost unless adequate protection is in place.

Frost - Water expands by about 9% of its volume when it freezes. In a closed container containing pure water, the critical saturation point is 91.7% of the total volume if there is less than 8.3% unoccupied space, then rupture of the vessel is likely as the water freezes.

The most effective protection against frost is to carry out work in the months where frost does not occur, but where this is not possible provide a scaffold construction with sheeting on the outside against rain/wind and hessian sheeting on the wall. Again attention should be paid to detailing, roof, drainage and gutters. The same applies in structures where moisture is coming from within.

Should it be necessary to continue work during the cold season, adequate heating of the structure should be in place together with the scaffolding system previously described.

Sun - Strong and direct sun can cause rapid drying and shrinkage. This effect could be aggravated in the presence of warm wind.

Scaffolds should have close knit debris netting on the outside to provide shade without impeding ventilation.

It is also required that, in warm weather and active drying conditions, the finish is cured (3-4 times daily) with light water. 

VISUAL OBSERVATION

MAIN CAUSES

CRACKING
not due to movement 
 
Cracking webs:
very fine, normally on surface only
 
   
 
Micro cracking:
less than 1/64 inch (0.2mm), various directions
    
Macro cracking: up to 1/16 inch (2mm)
 
 
Fissures : over 1/16 inch (2mm)

Wrong choice of product's characteristics and specification with poor product knowledge.
 
Movement cracks in the substrate.
Cracked joints.
Bridged joints
Wrong water addition.
 
Insufficient mixing time.
Non-application of metal or fiber mesh when needed including between different substrates.

High shrinkage due to substrate suction or climatic conditions.
 
 
Finish too thick in places. Overworking the surface.

WATER ABSORPTION

Cracks
Finish below 3/8 inch (10mm) minimum thickness.
Too deep scratches, reducing minimum thickness at lowest point.

DELAMINATION

Substrate not cleaned and prepared properly.
Over saturated substrate
High suction in the substrate
Absence of a bonding coat on particular substrates
Rapid drying of the finish due to suction or climatic conditions especially in thin coats.

SHEARING
Mainly on low strength substrates
such as light weight blocks.

Wrong product choice. Substrate not dampened.
Masonry units not ready (own shrinkage not completed).
Absence of bonding coat.