Hello, everyone.
This is Enta.
Earlier, is there a specific reason for using metal spacers (PC spacers)?
So, I put together some materials.
The reason why it's made of iron.
"Because the thermal expansion coefficients are different, there are fewer cracks."
I just put that into a table, but the government office seemed to understand it just fine.
I've included this table as well, but there's a big difference between iron and polyethylene, isn't there?
This is why mortar surfaces develop deep, jagged cracks.
In fact, you might think there’s no way mortar could lose to polyethylene, but it’s a type of mortar that can’t even hold up against tree roots.
There's no way it can beat polyethylene, lol (especially since sprayed mortar is so thin).
Well, it’s constantly exposed to heat and cold over the years, after all.
So why is steel not a problem? It’s because its coefficient of thermal expansion is almost the same as that of concrete.
That's why it's easy to see that the Ras Net is a great match, too.
| Product Name | Unit | Tensile Strength | Product Name | Unit | Coefficient of Thermal Expansion | Notes |
| Polyethylene | kgf·mm² | 0.42–1.61 | Polyethylene | ×10-6/K | 180.0 | High-Density PE |
| 鉄 | kgf·mm² | 35–50 | 鉄 | ×10-6/K | 11.7 | |
| PC Spacer | kgf·mm² | 284–304 | PC Spacer | ×10-6/K | 11.7 | For tensile strength, refer to JIS G3522. |
| Concrete | kgf·mm² | Incidence Rate: 1/10 | Concrete | ×10-6/K | 11.7 | Its coefficient of expansion is nearly the same as that of iron. |
Here's what it looks like in a table.
You can clearly see the polyethylene spacers expanding due to heat within the mortar.
It is a well-known fact that mortar has low tensile strength.
A crack occurs when a polyethylene spacer expands inside the mortar and is pushed from within, causing it to snap open easily.
It is extremely rare to find polyethylene spacers used in critical structural elements such as building frames.
Especially in places that are particularly susceptible to heat.
You can see this clearly when you look at the numbers.
That said, there’s actually another reason why I use steel spacers the most.
Even if there are leftovers at the site, they'll still sell! lol
This is it!
Even if you bring home leftover scrap from the job site, you can sell it at a scrap metal dealer for a small amount. (In reality, it’s sold along with other scrap metal.)
They won't pick up plastic trash unless you pay.
That's a huge difference!
I took the leftovers home from the job siteThings That Can Be Exchanged for MoneyAnd,Things that aren't like that.
And recently, there’s also the issue of microplastics.
While the quality of the mortar spray on the slope is important,
Cost and the environment are important, too!
I want to make sure to keep track of even the smallest expenses!
See you later.
We will post the documents on our website so they can be downloaded.
Weather Resistance of Polyethylene and Carbon Black | The Truth About 100-Year Durability
