Balcony repair with PMMA resin

[Erik79]

We have a slate balcony that has suffered years of water damage. One of the edges has the most extensive damage, borderline compromising the structural integrity of the slab as directly underneath that edge is one of the pillars holding the balcony (the crack goes all the way almost the depth of the slab in that place). We therefore need a solution that will not only provide waterproofing but also structural bonding. 

I have got a couple of quotes to use a waterproofing system based on PMMA resin. This will cover the whole balcony and the contractor says that it will also provide structural repair once it is applied and cured within the slate cracks. The (only) stonemason that came around to see it suggested to insert reinforcement bars prior to waterproofing. I want a good solution but I also dont want to do unnecessary repairs if the PMMA resin is the solution that can offer both waterproofing and structural integrity?

[TonyT]

Can’t offer any help but make sure the metal work is not rusting, the rust expands the hole the metal work sits in , leading to a route for water.

 

what about lithomex 

https://heritagestonemasonedinburgh.co.uk/our-work/lithomex-stone-repairs-edinburgh/

 

[Erik79]

13 minutes ago, TonyT said:

Can’t offer any help but make sure the metal work is not rusting, the rust expands the hole the metal work sits in , leading to a route for water.

 

what about lithomex 

https://heritagestonemasonedinburgh.co.uk/our-work/lithomex-stone-repairs-edinburgh/

 

You are right on that one, the original entry seems to be at the base of the railing and expanded from there. Previous owner seem to have tried to DIY the crack by some form of resin and cement mix but obviously it failed and led to more damage. We are restoring the railings as well along with the slate slab. I wasn't aware of lithomex I will look it up. 

[Onoff]

You might consider Ferrogard. From memory this was used to arrest the corrosion on art deco concrete buildings for one. I think Sika bought the product off the inventor? I recall when it first came out and the blurb to the effect that fresh concrete around steel initially has a protective effect enveloping it in an alkaline medium. Over time there's an ingress of C02 and it turns acidic leading to corrosion. Or something like that...

 

https://www.rawlinspaints.com/home/repair-materials/hole-and-damage-mortars/1970-sika-ferrogard-903.html?gclid=EAIaIQobChMI0pbTjJS4_gIVCYFQBh0x7godEAAYASAAEgKy_PD_BwE

[SteamyTea]

I would be worried using polymethyl methacrylate if there is steel work in contact with it.

We used to cast stuff in it, we avoided anything metal.

Though having said that, printed beer bottle tops did not give a problem.

Easy way is to test a small sample first, then rapid age it by thermally cycling in an oven.

[Onoff]

36 minutes ago, SteamyTea said:

I would be worried using polymethyl methacrylate

 

Would acrylic resin be better?

[SteamyTea]

1 hour ago, Onoff said:

 

Would acrylic resin be better?

It is an acrylic.

 

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POLYMETHACRYLATES (PMMA, PLEXIGLAS)

PROPERTIES AND APPLICATIONS

Polymethyl methacrylate (PMMA), also known as acrylic or plexiglas, is a high volume amorphous, transparent and colorless commodity thermoplastic that can be easily processed and converted into many finished and semi-finished products.

 

Most commercial grades of PMMA are polymerized by free radical polymerization, yielding atactic polymers whereas anionic polymerization yields syndiotactic or isotactic polymers. Most commercial grades of PMMA, however, are atactic with a glass transition temperature of 398 K (125 °C).

 

 

 

Commercial PMMA is often copolymerized with comonomers other than methyl methacrylate. The Tg of these products can vary, ranging broadly from approximately 360 K to 430 K (87 to 157 °C).

 

PMMA is known for its stiffness, hardness and excellent weatherability. Unmodified PMMA, however, is rather brittle and has low impact strength and fatigue resistance. To increase its toughness, it is often modified with core-shell rubber or other impact modifers. These resins offer seven to 10 times the impact resistance of standard PMMA while maintaining high transparency.1

 

Because of its high transparency (92% transmission) PMMA can be used as a lightweight and shatter-resistant replacement for regular glass. It has sufficient impact resistance to be machined and is often an economical alternative to polycarbonate (PC) when very high toughness and impact strength is not required. It comes in a variety of forms such as sheets, rods, and tubes, and is used for signs, optical fibers, architectural structures, tail lights for cars, bathtubs and sanitary fixtures, to name only a few applications.

 

Many other methacrylic monomers are commercially available. They are either copolymerized with methyl methacrylate to improve its properties or are added to many other resin systems to make a wide range of polymer-based products like binders in paints, coatings, toners, inks, and water-soluble polymers.

Edited April 20, 2023 by SteamyTea

[Onoff]