This document provides procedures for mechanically mixing hydraulic cement pastes and mortars. The paste procedure involves adding cement to water and allowing it to absorb for 30 seconds before mixing at slow speed for 30 seconds and then medium speed for 1 minute, stopping to scrape the sides after 15 seconds. The mortar procedure involves adding cement to water and mixing at slow speed for 30 seconds, then adding sand over 30 seconds while mixing slowly. It is then mixed at medium speed for 30 seconds, allowed to rest for 1.5 minutes with scraping after 15 seconds, and given a final 1 minute medium mix.

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

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