Normal consistency of ordinary portland cement

Eng.Anwaar AL-Suraij

Introduction

Building materials experiment

Materials

Cement

Reinforced bars

Bitumen

Fine aggregate & coarse aggregate

Mix design

Fish concrete

Structural building

Destructive Test

Non Destructive Test

Normal consistency and setting Time of Hydraulic Cement

Experiment #1

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Type of Mixing

Cement Past

Cement + water + Sand

Cement Mortar

Cement + Water + Sand + Aggregate

Concrete

Cement + Water + Sand + Aggregate + Reinforcement bars

Reinforced Concrete

Cement + water

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Normal consistency and setting Time of Hydraulic Cement

Introduction:

Portland cement is a finely ground powder composed of mineral compounds that react with water, set and harden.

Portland cement is a manufactured product and is composed of for four main components, which are:

Lime

Silica

Alumina

Iron

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There are five common types of Portland cement

Type I

Normal or ordinary Portland cement (Ordinary Portland Cement (OPC) is the most common cement used in general concrete construction

Type II

Moderate sulfate-resistant Portland cement

Type III

High early strength Portland cement

Type IV

Low heat of hydration Portland cement

Type V

Sulfate resistant Portland cement ( SRC)

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Type I

It is used for general construction purposes.

It is also used in most of the masonry works.

( Above ground level)

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Type II

For general use, more especially when moderate sulfate resistance or moderate heat of hydration is desired.

( underground structure but not high sulfate)

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Type III

It is used where concrete structures are subjected to high temperatures like workshops, refractory, foundries, etc.

It also used where the concrete is subjected to frost and acidic action.

( Time is important )

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Type IV

It is used for the construction of dam’s large footing, large raft slabs, and wind turbine plinths.

It is also used for the construction of chemical plants

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Type V

It is highly sulfate resistant

Frequently used in seawater construction

( Severe Sulfate in soli)

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Mix cement

To Preparation of cement paste

Use Mixer apparent

Place quantity of water ( Trial quantity)

Add 650 g of cement

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Vicat apparatus rod

Center the paste confined in the ring under the Vicat apparatus rod.

Adjust the apparatus to the zero mark when the rod is just touching the surface of the paste.

Release the rod and take the reading after 30s.

Vicat apparatus shall conform sizes requirement in ASTM C 187 – 04

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The cement paste shall be of normal consistency when the rod settles to a point 10 (+ or -1) mm below the original surface

Calculate the amount of water required for normal consistency as follows:

N.C.%=W*100/C

Where:

W = Weight of mixing water for 10 (+1 or -1) mm penetration

N.C. = Normal consistency

C = Weight of cement = 650 grams

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Weight of water (gm) Rod penetration (mm)
148 4
150 5
152 8
154 12
Example :

In order to determine the N.C. of ordinary Portland cement sample, the following Vicat penetrations data were obtained. Calculate the normal consistency.

From the plot, the amount of water required to give 10-mm penetration is equal to:

W10 = 153 gm

W=153

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Vicat pentration versus amount of water

148 150 152 154 4 5 8 12
Amount of water(gm)

Rod penetration (mm)

Normal Consistency test

Setting time of hydraulic cement test

Preparation of cement past sample to be qualified this sample

For anther test to acceptance or rejection of cement

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Setting time by Vicat apparatus

Experiment #1

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Setting time by Vicat apparatus

This method is used to determine the time of setting of hydraulic cement by means of the Vicat needle

The initial setting time: when the needle penetrates 25 mm into the paste and it is measured from the instant of mixing cement with water.

2. The final setting time: when the needle dose not sink visibly into the paste and it is measured from the instant of the mixing cement with water.

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Initial set. Occurs when the paste begins to stiffen considerably.

For construction purposes, the initial set must not be too soon

Final set. Occurs when the cement has hardened to the point at which it can sustain some load

For construction purposes, the final set must not be too late

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After tested the cement paste by normal consistency Place the cement confined in the conical ring in the moist room for 30 minutes.

Then determine the penetration at every 15 minutes thereafter.

Take the first reading at the zero time .

Vicat apparatus shall conform size of needle requirement in ASTM C 191 – 08

Vicat apparatus needle

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Example : In order to determine the initial and final setting time of ordinary Portland cement sample, the following Vicat penetrations data were obtained:

Time (minutes) Penetration (mm) Time (minutes) Penetration (mm)
0 40 165 26
15 40 180 24
30 40 195 21
45 40 210 17
60 39 225 14
75 38 240 9
90 37 255 6
105 36 270 3
120 34 285 1
135 32 300 0
150 29 -- --
Determine the initial and final setting times?

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From the plot, the initial setting time at 25 mm penetration

Solution:

The final setting time at 0 mm penetration

=170 Minutes

= 300 Minutes.

Initial time =170 min

Final time =300 min

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Needle penetration versus time

0 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240 255 270 285 300 40 40 40 40 39 38 37 36 34 32 29 26 24 21 17 14 9 6 3 1 0
Time (minutes)

Needle penetration (mm)

Acceptance Criteria

ASTM C 150 specifies the following limits:

Minimum initial setting time is 45 minutes.

Maximum final setting time is 375 minutes

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