Hello, everyone.

This is Enta.

The other day at the job site, I noticed that the ground anchor workers were using a lot of plastic, but,

The conversation turned to the fact that rebar installers are sometimes called “injection pipe pullers”!

That's true, isn't it?

Well, I don't really mind either way, so if I'm told to disconnect the injection hose, I'll do it, and

Unless I'm told otherwise, I'll leave it as is.

 

A wide variety of plastics are used in concrete structures.

But it doesn't really have that much of an impact, does it?

It's not all cracked and broken.

If you keep that in mind, I don't think any cracks will form, but,

Conversely, methods such as sprayed mortar are prone to cracking.

 

I think this is due to the small cross-sectional area.

Sprayed mortar that dries rapidly in a narrow cross-section is inevitably prone to cracking, isn't it?

I also wonder if the plastic spacers might be having at least some effect.

It's a matter of the expansion rate.

I made some test specimens and ran some tests before, but the results were that the spray conditions were so good that none of them cracked lol.

I figured it would probably be better to make the test specimens and run the tests in the middle of summer, lol.

 

Lately, I’ve been hearing a lot from the Ministry of Land, Infrastructure, Transport and Tourism that plastic spacers are not allowed (they’re considered foreign objects).

For this reason, we generally use PC spacers (Koiwa Wire Mesh) for spray-applied coatings.

Well, if that's what causes cracks, I guess there's nothing we can do about it.

Generally speaking, rapid drying of small cross-sections tends to cause cracking, so,

During the summer, it's best to add FT700 (admixture).

Adding about 2% to the spray machine significantly improves workability. (Since it doesn't harden.)

Well, it does cost a bit more, but I recommend it during the summer.

 

This argument about plastic has been around for a long time.

However, there isn't really a solution, so it feels like we just have to accept it as it is,

When you consider the cost, plastic is definitely the best option, isn't it?

 

However, since we’re in an era of reducing plastic use, I’m not sure what will happen going forward, but,

It seems that metal spacers are indeed the best choice for applications such as sprayed mortar.

As for ground anchor construction, I don't think it's likely to be phased out ever, so I think it's fine to leave it as is, lol.

 

See you later