Hello, everyone.

This is Enta.

Do you know the standards for compressive strength?

I've talked about this before, but maybe you don't get it? A lot of people don't know about it, lol.

 

I think we often perform ground anchor and rebar insertion work.

What type of cement do you usually use for that?

 

I'm guessing it's fast-setting cement, right?

But is that really correct?

 

Basic Specifications for Cement Slurry (Grout): The cement used is ordinary Portland cement.

So that means the strength test is for 4-week strength (28 days), right? (1 week, 4 weeks)

So why are we using fast-setting cement?

 

Because the strength develops quickly.

The reason strength develops quickly is that tension builds and stabilizes quickly.

 

However, just because it is a fast-setting cement does not mean that the test date for the basic compressive strength test changes.

The basic premise is the intensity of Weeks 1 and 4.

However, if the construction plan states that the strength test will be conducted after one week to ensure the stress has been fully developed, then the 7-day strength will serve as the standard.

 

Basically, what I'm trying to say is that we're setting the date for the 7th because we want to complete the strength verification sooner for our own reasons (such as shortening the construction schedule).

That's the thing.

 

There are no references or specifications that require compressive strength testing to be performed on concrete that is 7 days old.

This is strictly based on the intensity of Week 1 and Week 4 only.

 

Since we’re securing the tension after confirming the strength, we’re just being flexible about it, lol.

At the office, the workload is intense for one week out of every four.

It's just that, for the contractor's convenience, they're treating one week as four weeks for verification purposes.

In fact, that would mean we're simply checking the intensity by treating three days as one week.

 

So, this isn't something to take for granted.

 

A section chief at the Ministry of Land, Infrastructure, Transport and Tourism told me this a long time ago.

"You guys are just deciding all this on your own, aren't you?!" lol

 

See you later.

 

References

JIS A 1108:2022 “Test Method for Compressive Strength of Concrete”

JSCE-G 505:2018 “Compressive Strength Testing of Concrete”

The Japan Society of Civil Engineers, “Standard Specifications for Concrete (Construction Edition), 2022 Edition”

Architectural Institute of Japan, “Standard Specifications for Construction Works and Explanatory Notes: JASS 5—Reinforced Concrete Construction”