mechanical mixing of hydraulic cement

1. Ultra Design & Research.CC
Prepared by: Eng. Shoaib Zarea 16/April/2016

2. Preface:
 Introduction & Scope:
 Significance and Use:
 Apparatus & Materials:
 Procedure:
 Reference:

3. Introduction & Scope:
 This practice covers the mechanical mixing of
hydraulic cement pastes and mortars of plastic
consistency
 Paste= ‫خمیر‬ cement+water
 Mortar=‫مرتار‬ cement +water+sand

4. Significance and Use:
 This practice is intended for use in the mechanical
mixing of pastes and mortars for the testing of
hydraulic cements.

5. Apparatus & Materials:
 Mixer
 Paddle
 Mixing Bowl
 Scraper
 Supplementary Apparatus

6. Procedure for Mixing Pastes
 Place the dry paddle and the dry bowl in the mixing position in the mixer. Then
introduce the materials for a batch into the bowl and mix in the following manner:
 Place all the mixing water in the bowl.
 Add the cement to the water and allow 30 s for the absorption of the water.
 Start the mixer and mix at slow speed (140 +_5 r/min) for 30s.
 Stop the mixer for 15 s and during this time scrape down into the batch any paste that
may have collected on sides of the bowl.
 Start the mixer at medium speed (285 +_ 10 r/min) and mix for 1 min`

7. Summery
of Procedure for Mixing Pastes
 Add cement to water and allow (30 sec)to absorb.
 Turn on mixer in slow speed (30 sec).
 Stop (15 sec) and clean the wall.
 Turn on mixer in medium speed (1 min)

8. Procedure for Mixing Mortar:
 Place all the mixing water in the bowl.
 Add the cement to the water; then start the mixer and mix at the slow speed (140 6 5 r/min) for 30 s.
 Add the entire quantity of sand slowly over a 30-s period, while mixing at slow speed.
 Stop the mixer, change to medium speed (285 +_ 10 r/min), and mix for 30 s.
 Stop the mixer and let the mortar stand for 1 1⁄2 min.
During the first 15 s of this interval, quickly scrape down into the batch any mortar that may have
collected on the side of the bowl; then for the remainder of this interval, cover the bowl
with the lid.
 Finish by mixing for 1 min at medium speed (285 -+ 10 r/min).

9. Summery
Procedure for Mixing Mortar:
 Add cement to water- slow mix for (30 sec)
 For next (30 sec) without stopping the device add sand during this 30 s
 Turn off mixer, immediately turn on in medium speed for
(30 sec)
 Turn off mixer for (1.5 min)- in first (15 sec) clean the wall
and then cover the bowl in (rest of the time)
 Finally, medium mixing for (1 min)

10. Reference:
 ASTM Standards: C 778 Specification for Standard Sand
 ASTM C 191
 ‫بتن‬ ‫ازمایشگاه‬ ‫های‬ ‫عمل‬ ‫دستور‬

11. THANK YOU