The initial setting is the required time to set and after that concrete cannot be poured
or formed; the final setting time is the time required for the concrete to be hardened.
Vicat apparatus (Figure 4.2) consists of a carrier with needle acting under a prescribed
weight. The parts move vertically without friction and are not subject to erosion
or corrosion. The paste mold is made from a metal or hard rubber or plastic like
a cut cone with depth of 40 ± 2 mm and the internal diameter of the upper face 70 ±
5 mm and lower face 80 ± 5 mm and provides a template of glass or similar materials
in the softer surface. Its dimensions are greater than the dimensions of the mold.
The needle is used to determine the initial setting time in a steel cylinder with
effective length 50 ± 1 mm and diameter 1.13 ± 0.5 mm. The needle measuring time
is in the form of a cylinder with length of 30 ± 1 mm and diameter 1.13 ± 0.5 mm and
held by a 5 mm diameter ring at the free end to achieve distance between the end of
the needle and the ring of 0.5 mm.
The test starts by taking a sample weighing about 400 g and placing it on an
impermeable surface and then adding 100 ml of water and recording zero measurement
from the time of adding water to the cement and then mixing for 240 + 5 seconds
on the impermeable surface.本文来自辣.文,论-文·网原文请找腾讯3249-114
To determine the initial setting time and calibrate the device until the needle
reaches the base of the mold, then adjust the measuring device to zero and return
needle to its original place.
Fill the mold with cement paste with standard consistency and troll the surface,
then put the mold for a short time in a place that has the the temperature and humidity
required for the test.
Specific Surface (Wagner)-m2/kg
365 days
90 days
28 days
7 days
20
150 200 250 300
30
40
50
Compressive Strength, Mpa
Transfer the mold to the apparatus under the needle, and then make the needle
slowly approach the surface until it touches the paste’s surface, stop it in place for
a second or two seconds to avoid impact of primary speed, then allow the moving
parts to implement the needle vertically in the paste.
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