Normal consistency of hydraulic cement

Normal Consistency and Setting Time of Hydraulic Cement

Conducted on: February 2rd, 2020

By:

Batoul Sultan Sultan 2161115732

Rawan Adel Alrshedi 2171120992

Hadel Bader Almutairi 2171114584

February 2th, 2020

Wednesday Group

On my honor I pledge that this work of mine does not violate the University provisions on academic misconduct. By signing below, I certify that I understand the University Policies on academic misconduct is committed; all parties involved are in violation.

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Abstract

There was two experiments were conducted in order to determine the normal consistency of the hydraulic cement and the second one to determine the setting time of the hydraulic cement. In the first part of the experiment used the Vicat apparatus particularly its rod to establish if the cement past was of the normal consistency. One needed to check if after 30 second of the rod being released, did the rod setting to a point 100 (+or-1) mm below the original surface or no? After various attempts, it was concluded that by using 650gm of cement and 160gm of water, the rod penetration had a value of 9mm, which puts the hydraulic cement at normal consistency. The second part (Setting Time of Hydraulic Cement Paste) was also conducted by the used of the Vicat needle. In order to determine the initial setting time, one needed to observe when the needle penetrates 25mm into the paste. However, to determine the final setting time, one needed to observe when the needle does not evidently sink into the paste.

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Table of Contents

Abstract ……………………………………………………………………………………………………………………. i

Table of Contents ………………………………………………………………………………………………………. ii

List of Figures and Tables ………………………………………………………………………………………….. iii

Nomenclature …………………………………………………………………………………………………………… 1

Introduction: …………………………………………………………………………………………………………….. 2

Objectives: ……………………………………………………………………………………………………………….. 3

Theoretical Background: ………………………………………………………………………………………….. 3

Experimental Details (set up and procedure):……………………………………………………………. 4

Results and Discussion: …………………………………………………………………………………………….. 6

Subtitle 1:………………………………………………………………………………………………………….….. 6

Subtitle 2:……………………………………………………………………………………………………………... 7

Conclusions :……………………………………………………………………………………………………………… 8

Acknowledgements :…………………………………………………………………………………………………. 9

References :………………………………………………………………………………………………………………. 9

Appendix :…………………………………………………………………………………………………………………. 10

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List of Figures and Tables

Figure 1: Vicat apparatus ……………………………………………………………………………………………….. 4

Figure2: Vicat penetration versus amount of water………………………………………………………… 7

Figure 3: Needle penetration versus time……….……………………………………………………………... 8

Table 1: Data for determining the Normal consistency of cement paste…………………….…… 6

Table 2: Setting time by Vicat Apparatus…………………………………………………………………………. 7

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Nomenclature

Milligrams = gm

Millimeter = mm

Minutes = min

Second = Sec

Percentage = %

Wight of mixing water = W

Wight of cement = C

1

Introduction

Cement is a water-based binder used to bind other building materials together. It is used in the production of mortar and concrete during the construction process. In the experiment (Normal consistency of Hydraulic Cement) it was used 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, and Iron). Also there are five common types of Portland cement.
The normal consistency of hydraulic cement
Is by determining the amount of water required to prepare cement paste for Initial and final time of setting test. That mean when we change the amount of water will have different consistency for cement.
Normal Consistency:
is a standard measure of plasticity of a Cement Paste , which has a normal consistency when a Vicat plunger penetrates (10 ± 1mm) in time (30sec). Also the time factor must be taken into consideration, to have good result. In this experiment we follow the ASTM C150 Standard.
What is the consistency test? A consistent test is one for which the power of the test for a fixed untrue hypothesis increases to one as the number of data items increases
What is Vicat test?
Vicat softening temperature or Vicat hardness is the determination of the softening point for materials that have no definite melting point, such as plastics. It is taken as the temperature at which the specimen is penetrated to a depth of 1 mm by a flat-ended needle with a 1 mm2 circular or square cross-section
Setting time of hydraulic cement:
The second experiment was used to determine the time of setting of hydraulic cement, by using the vacant needle. Not to mention it distinguish the time of the cement paste if it remains plastic loge enough to allow normal placing of concrete without obstructing final procedure.
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Objectives:

A. Normal consistency:

This method covers determination of the normal consistency of hydraulic cement, which is the amount of water, required in preparing a hydraulic cement paste for testing.

B. Setting time:

This method was used to determine the time of setting of hydraulic cement by means of the Vicat Needle. It also determines if a cement paste remains plastic long enough, to permit normal placing of concrete without hampering finishing operation. It also establishes whether the cement complies with the specification limits of the setting time.

Theoretical Background:

Portland cement is finely ground powder composed of mineral compound that react with water, set and harden. Portland cement is manufactured product and is composed of for four main components, which are Lime, Silica, Alumina and Iron. There are five common types of Portland cement. Normal consistency is the cement paste shall be of normal consistency when the rod settles to a point 10(+or-) mm below the original surface 30 second after being released. Vicat apparatus is a penetration instrument used to find out the setting time (initial and final) and normal consistency of the hydraulic cement. Initial setting time is the time at which the needle penetrates 25mm into the paste and it was measured from the instant of mixing cement with water. Final setting time is the time at which the needle does not visibly into the paste, and it was measured from the instant of mixing cement with water

N.C %=W*100/C , Where:

N.C= Normal Consistency

C= weight of cement=650grams

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

ASTM C150 specifies the following limits:

Minimum Initial setting time is 45min.

Maximum Final setting time is 375min.

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Experiment Details (set up and procedure):

1- Materials:

• Cement

• Water

2- Specimens:

Sample was cement paste

3- Apparatus:

• Mechanical mixer

• Weights and weighing devices

• Glass graduates

• Vicat apparatus

• Supplementary apparatus

Figure1: Vicat apparatus

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4. Procedure:

A. Normal Consistency

a) Preparation of the cement paste:

1- Place all the trial quantity of mixing water in the bowl of the mixer

2- Add 650gm of the cement to the water and allow 30s for the absorption of water

3- Start the mixer at slow speed for 30s

4- Stop the mixer for 15s

5-Scrape down into the batch any paste cement that may be collects on the sides of the bowl

6-Start the mixer at medium speed and mix for 1 minute

b) Molding of the test specimen:

7- Quickly from the cement paste into a ball with gloved hands

8- Then toss six times through the free path of about 15cm from one hand to another

9- Press the ball, resting in the palm of one hand, into the larger end of the conical ring completely filling the ring with the paste and remove the excess using a trowel

c) Consistency determination:

10- Center the paste confined in the ring under the Vicat apparatus rod

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

12- Release the rod and take the reading after 30s

B. Setting time:

1-prepare a cement paste of normal consistency (step 1 to 9 in the normal consistency test)

2-Place the cement confined in the conical ring in the moist room for 30 minutes

3- Center the paste confined in the ring under the Vicat apparatus needle and adjust the apparatus to zero mark when the needle is just touching the surface of the paste

4- Release the needle for 30s and record the penetration reading from the apparatus

5- Determine the penetration at every 15min thereafter

6- Plot penetration versus time and determine (the initial and final setting times)

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Results and discussion

1. Normal consistency

Table 1: Data for determining the Normal consistency of cement paste

Weight of water (gm)

Rod penetration (mm)

155

6

157

7

160

9

162

12

The following table demonstrates the N.C that was measured while conducting the experiment. Considering the constant weight of cement that was 650 gm’s, the weight of water was inferred in order to reach a normal consistency rate, which was 9, 10, or 11mm. First 155gm of water was inferred which resulted in less than the N.C that was needed. Therefore 157 gm’s of water were added however the rod penetration was yet still 7mm. Finally 160 gm’s of water were added and it reached a state of N.C.

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Figure 2: Vicat penetration versus amount of water

The sample required 160 gm of water to reach a state of N.C which was 24.6%.

2- Setting time by Vicat Apparatus

Table 2: Setting time by Vicat Apparatus:
Time (minutes)
Penetration (mm)
Time (minutes)
Penetration (mm)
0
40
165
18
15
40
180
15
30
40
195
12
45
40
210
9
60
39
225
7
75
38
240
4
90
36
255
2
105
33
270
1
120
30
285
0
135
26
150
22
7
The following table demonstrates the measured values while conducting the experiment by using the vicat apparatus needle. The initial and final setting time was also obtained. A trend is observed in the first 4 intervals of 15 minutes, the penetration was the same then it starts decreasing until it reaches a 0mm penetration in 285 minutes.
Figure 3: Needle penetration versus time

Figure 2 shows the relation between the setting time and the Vicat Apparatus using a needle. The x-axis represents the time in minutes while the y-axis represents the needle penetration in mm. the graph is decreasing until it reaches 0mm needle penetration in 285 minutes. The initial time setting at 25 mm is 130 minutes.

Conclusion:

· The sample required 160 gm of water to reach a N.C of 24.6%

· The initial setting time was 130 minute and the final setting time was 285 minutes.

· The sample complies with the ASTM C150 specification.

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Acknowledgments

We would thank our Eng. Nouf Al Sabbagh and express our deepest appreciation to all who help us in understanding the information needed in order to successfully write well-informed report. Also a special gratitude to Eng. Mohammed Yahia and Eng. Nazir Al Islami, without their help we wouldn’t be able to conduct this experiment.

References

- Kuwait University CE 252 Building Materials Lab manual.
- ASTM C 150- Standard specification for Portland Cement.
- ASTM C 18- Normal consistency of hydraulic cement.
- ASTM C 191- Time of setting of hydraulic cement by Vicat Needle
- ASTM C 305- Practice for mechanical mixing of hydraulic cement paste and mortars of plastic consistency.
- Concrete Technology by: A.M. Neville &J.J. Brooks (revised 1991)
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Appendix:

The following calculation is the percentage of normal consistency:

N.C%= W*100/C

N.C%= 160*100/650

N.C%= 24.6%

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Needle penetration versus time

Penetration (mm) 0 15 30 45 60 75 90 105 120 135 150 165 180 195 210 225 240 255 270 285 40 40 40 40 39 38 36 33 30 26 22 18 15 12 9 7 4 2 1 0
Time (minutes)

Needle Penetration (mm)

Vicat penetration versus amount of water

Rod penetration (mm) 155 157 160 162 6 7 9 12

Amount of water (gm)

Vicat penetration (mm)