Mechanical Mixing of Hydraulic Cement Pastes and Mortars

ASTM C 305

Ultra Design & Research.CC

Prepared by: Eng. Shoaib Zarea 16/April/2016

Preface:Introduction & Scope:

Significance and Use:

Apparatus & Materials:

Procedure:

Reference:

Introduction & Scope:

This practice covers the mechanical mixing of hydraulic cement pastes and mortars of plastic consistency

Paste= خمیر cement+waterMortar= مرتارcement +water+sand

Significance and Use:

This practice is intended for use in the mechanical mixing of pastes and mortars for the testing of hydraulic cements.

Apparatus & Materials:

Mixer

Paddle

Mixing Bowl

Scraper

Supplementary Apparatus

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`

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)

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).

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)

Reference:

ASTM Standards: C 778 Specification for Standard Sand

ASTM C 191 بتن ازمایشگاه های عمل دستور

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