foundation system of burj al arab

How to Measure Stiffening Time of Fresh Concrete?

We are not discussing here about Vicat apparatus; this apparatus is used to measure setting time of cement. In Vicat apparatus we use a needle (with specified weight) and left it to penetrate through cement paste, and depending on penetration depth we can determine setting time of cement paste.

Here we will use a probe named Proctor Probe which is a spring reaction probe and penetration pressure required to penetrate measures setting time of concrete.

Concrete Penetrometer according to ASTM C403
We will use mortar from fresh concrete by sieving concrete ASTM NO.4 sieve (5mm). The setting time is a measure of degree stiffening of concrete measure. The limiting penetration resistance are 500 psi (3.5 Mpa) and 4000 psi (27.6) Mpa.

Initial setting time is an indication of stiffness of concrete that is so stiff that cannot be provided mobility under vibration. The corresponding penetration resistance is 500 Psi.

When penetration resistance reached 4000 psi, it considered that final setting of concrete reached i.e. this is the final setting time. In this condition, if standard cylinder test is conducted to determine compressive strength, the value yields around 100 Psi (0.7 Mpa).

It should keep in mind that final setting of concrete in not final setting of cement.

ASTM C403 provides standard test method and we can use it to make comparison. But again it should include that this is not the absolute measure as we have not used concrete; just used mortar from parent concrete. An identical test method also provided by British Standard BS 5075: Part 1.