Time of setting of hydraulic cement by vicat needle experiment

Kuwait University

College of Engineering & Petroleum

Civil Engineering Department

Building Materials Lab

CE – 252

Report #1

Normal Consistency and Setting Time of Hydraulic Cement

Conducted on: February 3rd, 2019

By:

Fatmah Ebrahim Al Hamer 2171113502

Nora Shaheen Al Sulaiti 2171116026

February 10th, 2019

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Abstract

In this experiment, a group of Civil engineering students went to the local building materials lab located in the Kuwait University, Engineering campus. Two experiments were conducted in order to firstly determine the normal consistency of the hydraulic cement and secondly to determine the setting time of the hydraulic cement. The first part of the experiment used the Vicat apparatus (particularly its rod) to establish if the cement paste was of normal consistency. One needed to check if after 30seconds of the rod being released, did the rod settle to a point of 9, 10, or 11mm below the original surface? 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 of the experiment was also conducted by the use of the Vicat apparatus, more specifically the Vicat needle. In order to determine the initial setting time, one needed to observe when the needle penetrates 25mm into the paste (measured from the instant of mixing the cement with water). However, to determine the final setting time, one needed to observe when the needle does not evidently sink into the paste (measured from the instant of mixing the cement with water). After studying the sample of cement for 285minutes, it was concluded that the initial setting time at 25mm penetration was equal to 130minutes, and the final setting time at 0mm penetration was equal to 285minutes.

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Table of Contents

Abstract…………………………………………………………………….i

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

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

Nomenclature……………………………………………………………...1

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

Normal Consistency…………………………..2

Setting time of hydraulic cement……………...2

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

Theoretical Background:………………………………………………….4

Experimental Details (set up and procedure). …………………………..5-6

Figure 1:Vicat apparatus for normal consistency…………5

Results and Discussion:………………………………………………….7-9

Table 1: Normal consistency of cement paste ……………..7

Table 2: Setting time by Vicat Apparatus ……………….....8

Figure 2: Vicat penetration versus amount of water….….…7

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

Conclusions: …………………………………………………………….10

Acknowledgements. ……………………………………………….……11

References. ……………………………………………………………...12

Appendix.………………………………………………………………..13

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List of Figures and Tables

Figure 1: Vicat apparatus for normal consistency…………………………………………

Figure 2: Vicat penetration versus amount of water……………………………………….

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

Table 1: Normal consistency of cement paste……………………………………………

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

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Nomenclature

C= Weight of cement

Gm= Grams

Mm= Millimeter

W=Weight of mixing water

% = Percentage

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Introduction:

Portland cement is one of the most important ingredients that react with water to set and harden. It is used to form the basis of cement paste, mortar, concrete and reinforced concrete. Portland cement is composed mainly of four components, which are lime, Silica, Alumina, and Iron. Changing their percentages will lead to other forms of cement. There are five important types of Portland cement used in our region which are Types I, II, III, IV, and V. In this experiment two tests were conducted one to determine the normal consistency of hydraulic cement and the other was to determine the time of setting of hydraulic cement.

Normal consistency:

This first experiment is important in order to determine the amount of water needed to prepare the paste. The first experiment examines important factors of the cement that need to be acknowledged, which is the amount of water needed to prepare a hydraulic paste for testing, to check the normal consistency; in order to prevent bleeding. If the cement wasn’t hydrated correctly with the right amount of water it will loose its strength. While conducting the experiment we inferred the weight of water to a given weight of cement and tested it using the vacant apparatus by means of the vacant rod. To check if the cement reaches a state of normal consistency, the rod penetration must be of 9,10, and 11 mm’s.

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 distinguishes the time of the cement paste if it remains plastic long enough to allow normal placing of concrete without obstructing final procedure. This experiment focuses on the initial and final setting time of the cement paste such that the initial setting time must penetrate 25mm into the paste within a minimum timespan of 45 minutes. While the final setting time of the paste must penetrate 0 mm into the paste within a maximum of 375 minutes.

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Objectives:

The objectives of this experiment were:

1. To determine the normal consistency of hydraulic cement.

2. To determine the time of setting (the initial setting time and the final setting time) of hydraulic cement.

3. To learn how to accurately use the Vicat Apparatus, including understanding the difference between the Vicat needle and rod.

4. To learn the different types of cement that will be used in the experiment and their main components.

5. To properly understand the factors that affect the time of cement paste.

6. To learn how to use the appropriate equipment’s that determine the normal consistency and setting time.

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Theoretical Background:

Portland cement is keenly ground powder composed of mineral compounds that react with water then set and harden. Portland cement is made from four main components, which are: Lime, Silica, Alumina, and Iron. There are 5 common types of Portland cement, which differ in characteristics. Type I is also known as Ordinary Portland Cement and it’s the most common cement that is used in general concrete construction. Type II is considered moderate sulfate-resistant Portland cement. Type III has early strength while Type IV has low heat of hydration. Type V is considered as Sulfate resistant Portland cement. Cement paste is made from cement and water, while cement mortar is made from cement, water and sand. The Vicat Apparatus is a penetration instrument used to find out the setting time (initial and final) and normal consistency of the hydraulic cement.

The normal consistency of a cement paste is outlined as the consistency that allows the Vicat rod to penetrate to a point 9,10, or 11 mm below the original surface, 30 seconds after being released. In other words it is the amount of water or the degree of “wetness” demonstrated by the hydraulic cement and required for preparing a hydraulic paste for testing. The initial setting time is defined as the time when the Vicat needle penetrates 25 mm into the paste and it is measured from the instant of mixing cement with water. On the other hand, the final setting time is defined as the time when the Vicat needle does not sink evidently into the paste and it is measured from the instant of mixing cement with water. In order to calculated the percentage of Normal consistency of the cement paste, one must use the following equation: N.C. % = (W × 100) ÷ C One can make the assumption that at 9-11 mm of the Vicat rod penetrating below the surface of the cement paste, it will be of normal consistency.

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Experimental Details (set up and procedure):

1. Materials used

For the first and second test conducted the following materials were used.

· Water

· Cement

· Sand

2. Specimens

The following specimens were distinguished in the first and second experiment.`

· Cement paste

· Molding test specimens

· Consistency determination

3. Macintosh HD:Users:laila:Desktop:Vicat-Apparatus-300x267.png Equipment

· Mechanical mixer: was used to mix the cement and water paste by using two speeds slow and medium.

· Weights and weighing devices: was used to weigh the water in grams and the cement in grams.

· Glass graduates

· Vicat apparatus: was used to measure the normal consistency by using the rod and needle.

Figure 1: Vicat Apparatus for normal consistency

· Supplementary apparatus

4. Procedure

Experiment A

a) Preparation of cement paste.

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

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

3. Start the mixer at slow speed for 30 s.

4. Stop the mixer for 15 seconds.

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

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

b) Molding test specimens

7. Quickly form the cement paste into a ball with gloved hands.

8. Then toss six times through the free path of about 15- cm 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 towel.

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.

Experiment B

1. Prepare a cement paste of normal consistency (steps 1-9 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 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 30 seconds and record the penetration reading from the apparatus.

5. Determine the penetration at every 15 minutes thereafter.

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

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Results and discussion

1. Normal consistency

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.

Table 1: Normal consistency of cement paste

Weight of water (gm)

Rod penetration (mm)

155

6

157

7

160

9

162

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The normal consistency is 24.6%. The graph is increasing as the amount of water is added. The amount of water required to give a 10mm penetration is equal to 161 gm.

Figure 2: Vicat penetration versus amount of water

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2. Setting time by Vicat Apparatus

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.

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

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Figure 3: Needle penetration versus time:

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Figure 3 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.

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Conclusion:

The findings we got in the experiment correspond with the purpose of the experiment and the objectives stated in the objective section; they are also supported by the experimental results. We learned lots of information from this experiment as stated in the results and discussion sections. With the help of the Vicat Apparatus one was able to find out the normal consistency and the setting time (initial and final) of the hydraulic cement. By using the Vicat rod we were able to find out that by using 650gm of cement with 160gm of water, the cement paste will be at normal consistency. Also, by using the Vicat needle one was able to record the needle penetration (mm) and time (minutes) it took for the need to penetrate the sample in a booking table. From the values in the booking table one was able to plot a needle penetration vs. time graph. From the plotted graph, by extending a horizontal line from 25mm of penetration we were able to find a point of intersection in the graph. After finding this point of intersection, one can extend a vertical line to find the time in minutes that represents the initial setting time. Moreover, one can conclude that the sample complies with the ASTM C150 specification. The experiment taught us the importance of the Vicat Apparatus device in the study of building materials, civil engineering and construction. From this experiment, one learns how to correctly facilitate the process of using the Vicat Apparatus. One also learns the effects on structures and constructions if the cement samples were not tested before hand.

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Acknowledgments:

We would like to thank our teacher Eng. Nouf Al Sabbagh who helped us in understanding the information needed in order to successfully write a well-informed report. We would also like to recognize the effort of the two technicians whom without their help, we wouldn’t be able to conduct this experiment.

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References:

- Kuwait University CE 252 Building Materials Lab manual

- Sharma, S. K. (2013, September 02). Civil Engineering materials. Retrieved February 6,

2019, from http://civilengineeringmaterials2012.blogspot.com/2013/09/vicats-apparatus-consistency-and.html

- Cement consistancy test [Digital image]. (n.d.). Retrieved from

http://www.civilology.com/consistency-test-of-cement/

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Appendix:

The following calculation is the percentage of normal consistency:

N.C% = = = 24.6%.

From figure 3 the initial time setting is 130 minutes and the final time setting is 285 minutes.

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Vicat penetration versus amount of water

Rod penetration (mm) 155.0 157.0 160.0 162.0 6.0 7.0 9.0 12.0
Amount of water (gm)

Vicat penetration (mm)

Needle penetration versus time

Penetration (mm) 0.0 15.0 30.0 45.0 60.0 75.0 90.0 105.0 120.0 135.0 150.0 165.0 180.0 195.0 210.0 225.0 240.0 255.0 270.0 285.0 40.0 40.0 40.0 40.0 39.0 38.0 36.0 33.0 30.0 26.0 22.0 18.0 15.0 12.0 9.0 7.0 4.0 2.0 1.0 0.0
Time (minutes)