Hello, everyone.

This is Enta.

Today, I stopped by the Osaka Motor Show on my way to work.

One thing that came to mind during that limited time of an hour and a half was,

I felt like I got to see a different side of the auto show.

I guess a motor show isn't just about cars, huh?

---

But that's beside the point.

 

About Concrete Curing

JIS A1108

If the core test specimen is immersed in water at 20±2°C for at least 40 hours prior to testing,

During testing, the moisture content of the test specimens can be kept nearly constant.

Regarding that.

After looking into this,A shocking revelation!!!

Conclusionｗ

Cores extracted before the test date dry out significantly when left to cure in the open air.

Its strength decreases when it dries.

However, on actual job sites, the legal framework is subject to rain and other factors that cause it to get wet; it isn't always dry.

Therefore, a difference in strength arises between the core and the field, and in order to ensure that they are under the same conditions,

If the core is cured underwater for more than 40 hours, it can be brought to the same conditions as those at the construction site.

Comparison of Strength in Core Curing Methods and On-Site Strength

Core (In-Air Curing) < Construction Site

Core (kept submerged at all times since extraction) > Construction site

Core (cured underwater for at least 40 hours prior to the test) = On-site

 

It's fine to collect the core while in the air, butSwitch to underwater curing 2–3 days before the testThat means you should do it.

Doing so ensures that conditions match those on-site and also helps minimize variation.

I recommend giving it a try at sites where there is significant variation.

By the way, if someone working on a contract basis (who doesn’t know much about the job site) says to you, “But isn’t air curing the standard practice for spray-applied coatings?!!”

JIS A1108

Go ahead and proudly say, "It's in there!!" lol

Also,The strength of a dried core is reduced by up to about 20 percent compared to a normal core.

That's what they say. (↓ It's cited in the reference.)

 

References:Methods for Taking Core Samples from Concrete and Test Methods for Compressive Strength
JISA1107: Deliberated by the Japanese Industrial Standards Committee; Revised in March H24 (Published by the Japanese Standards Association)

Key Points of Concrete Technology 11 (Japan Concrete Institute)

 

See you later.