Sample Strength of Material Laboratory Report: Influence of Proportion of Water on Standard Consistency of Various Categories of Cement

Influence of Proportion of Water on Standard Consistency of Various Categories of Cement

ACKNOWLEDGEMENT:

First of all, I would like to thank my students who did laboratory investigation and put their best effort in writing this report.

Roll No.	Names	Semester	Section
2020-CV-48	Muhammad Bashar	3^rd	B
2020-CV-50	Shees Hamid Zahidi	3^rd	B
2020-CV-56	Farzam Zafar	3^rd	B
2020-CV-66	Muhammad Atal Khan Kakkar	3^rd	B
2020-CV-69	Azan Hafeez	3^rd	B
2020-CV-148	Mushahid Hussain	3^rd	D
2020-CV-161	Muneer Abbas	3^rd	D
2020-CV-162	Abdul Ghaffar Usman	3^rd	D
2020-CV-171	Emad ud din	3^rd	D
2020-CV-187	Hashim Ali	3^rd	D

ABSTRACT:

Concrete plays major role in the construction industry of Pakistan as it is frequently being used for the construction of substructures and superstructures due to its strength and durability. The major constituents of concrete are cement, coarse and fine aggregates and water. It is understood that concrete is strong in compression and weak in tension. For this purpose, provision of reinforcement is essential to make concrete strong in tension. Similarly, quality of main constituents of concrete are also significantly influenced the strength of concrete. As a matter of fact, the quality of cement surely matters if it does not comply to the required standards so eventually overall strength of concrete will be compromised. Furthermore, determination of quantity of water added in the cement is another major factor to get uniform concrete mix. This study focuses on the determination of consistency of various types of cement on varied percentages of water. It is necessary to get the accurate percentage of water on which standard consistency of cement can be achieved. The comparisons were drawn on the laboratory investigation of consistency of four different types of cement (Ordinary Portland Cement OPC, White Cement, Sulphate Resistant Cement SRC and blended mixture of Ordinary Portland Cement with Sulphate Resistant Cement) on varied percentages of water using Vicat apparatus. The observation is achieved that depth of penetration of plunger in millimeter decreases with the increase of proportion of water added in the cement for all the four categories of cement used in this study.

1. INTRODUCTION:

Undoubtedly, Cement is one of the most essential component of concrete as it provides bonding among other ingredients of concrete, however, the bonding mainly comprises of quality and category of the cement. Surprisingly, cement is available in numerous categories even in Pakistan. In fact, Ordinary Portland Cement OPC is most common category of cement and conveniently accessible in Pakistan. In construction sector of Pakistan, this category of cement is frequently being used for the construction of all types of structures. Ordinary Portland Cement OPC is further classified into three grades, namely 33, 43, and 53 grades. There are other types of cement which are also available in Pakistan such as White Cement and Sulphate Resistant Cement. Furthermore, the properties of cement can be varied with the incorporation of various bonds and supplementary cementitious materials. Since, cement is one of the most used construction material, the consistency of cement is also an important aspect of it.

The consistency of cement paste is defined as the percentage of water requirement of cement paste at which the viscosity of paste in such a way that it determines the amount of water needed to make a paste. It is necessary to determine consistency because the amount of water affects the setting time of the cement. The normal consistency of a cement paste is defined as that consistency (% of water) which will permit the Vicat plunger to penetrate to a point 10 mm from the top of the Vicat mold. The usual range of values being between 22 to 30 percent by weight of dry cement. Normal consistency is also called standard consistency. Consistency plays a vital role in the determination of compressive strength of concrete or workability test for concrete. A certain quantum of water is necessary to react with cement to make a paste with appropriate plasticity. Less water than this quantity would not complete chemical reaction thus resulting in the reduction of strength and more water would increase water-cement ratio and so would reduce its strength. Therefore, correct proportion of water to cement is required to be known to achieve proper strength while using cement in structure. This can be found out knowing standard consistency of cement paste. It is necessary to fix the quantity of water to be mixed in cement while experimenting on it. By standardizing the consistency of cement, we know that how much of water is required to produce an effective cement viscosity which will eventually produce good quality of cement mortar and concrete There are numerous factors which are held responsible for varied consistency of cement such as environmental factors, proportion of silica in cement and their brands.

1.1 OBJECTIVE:

The objectives of the proposed study are as under;

To investigate the basic required quantity of water to form a cement paste of different categories of cement as specified by IS Code 4031 (Part 4 – 1988).
To examine standard consistency of the different categories of cement and their effects.

1.2 SCOPE:

The scope of the study includes environmental factors such as temperature and humidity kept constant throughout the investigation.

2. Literature Review:

Srinivas Gutha investigated comparative study of properties of different types of binder mixes modified with silica fume of slag cement and fly ash cement. There were three combinations of slag and fly ash cement. In each combination three different proportion of silica fume had been added along with the controlled mix without silica fume. Binders being used were different combinations of slag cement, fly ash cement in the proportions 1:0, 0:1 and 1:1 hence total three combinations. Further in each type of combination of binder mix 0%,5 %,10 % and 15 % percentage of silica fume had been added. Hence total 12 sets of mortar of 1:3 proportion were prepared by mixing one part of binder mix and three parts of naturally available sand. They have conducted Compressive Strength Test, Capillary Absorption Test, Porosity Test and Consistency Test. They observed that water requirement or normal consistency of a binder mix increases with the increment in percentage of silica fume replacement and water requirement in case of fly ash cement binder mix is more because it is finer when compared to slag cement. Furthermore, they identified that all binder mixes show that up to 15% replacement of cement with silica fume the compressive strength increases with increasing dose of silica fume.

3. Methodology:

3.1 Apparatus:

The apparatus in this investigation used for the determination of consistency of cement paste is Vicat apparatus. In this laboratory experiment, the apparatus required such as the Weighing Balance of 1000 gram with 0 gram error accuracy, measuring Cylinder of 200ml for measuring of water quantity, Vicat Apparatus consist of glass plate, scale, cap load and plunger and Vicat mould. It is necessary to remember that general plunger should be 50 mm of height and 10 mm dia and vicat mould size is 80 mm in dia and 40 mm height.

3.2 Ordinary Portland Cement (OPC):

The constituents of Ordinary Portland Cement are:

• Argillaceous or silicates of alumina in the form of clays and shale’s.

• Calcareous or calcium carbonate, in the form of limestone, chalk and marl which is a mixture of clay and calcium carbonate.

The ingredients are mixed in the proportion of about two parts of calcareous materials to one part of argillaceous materials and then crushed and ground in ball mills in a dry state or mixed in wet state. The dry powder or the wet slurry is then burnt in a rotary kiln at a temperature between 1400^oC to 1500^oC. the clinker obtained from the kiln is first cooled and then passed on to ball mills where gypsum is added and it is ground to the requisite fineness according to the class of product.

Constituents of Ordinary Portland Cement (OPC)
Lime (CaO)	60 to 67%
Silica (Si O₂)	17 to 25%
Alumina (Al₂ O₃)	3 to 8%
Iron-oxide (Fe₂ O₃)	0.5 to 6%
Magnesia (MgO)	0.1 to 4%
Sulphur-trioxide (SO₃)	1 to 3%
Soda and/or Potash (Na₂O + K₂O)	0.5 to 1.3%

Table No.1: Constituents of Ordinary Portland Cement (OPC)

3.2 White Cement:

The whiteness is understandably one of the most important properties of white cement. This must be taken into account already in the selection of the raw materials proper. White cement is made from raw materials with a low content of colouring elements such as Iron Fe, Magnesium Mn, Chromium Cr and Titanium Ti.

3.3 Sulphate Resistant Cement:

Sulphate Resisting Cement is a cement in which the amount of Tricalcium aluminate (C₃A) is restricted to lower than 5 % and (2C₃A + C₄AF) is lower than 25%. Sulfate-resisting Portland Cement (SRC) is a special purpose cement used where sulphates are present in concentrations that would damage concrete.

3.4 Experimental Procedure:

In this laboratory investigation, different categories of cement purchased which were locally and conveniently available in Karachi, Pakistan. This was aimed at investigating differences in consistency of different categories of cement. Cement consistency tests were carried out on the four different categories of cement including Ordinary Portland Cement (OPC), White Cement, Sulphate Resistant Cement (SRC) and blended mixture of Ordinary Portland Cement and Sulphate Resistant Cement. For each category of cement, approximately 400g of cement weighed and mix it with a weighed quantity of water. The time of gauging should be between 3 to 5 minutes. Vicat mould filled with prepared cement paste and leveled it with a trowel. The plunger of the mould lowered it gently and gradually till it touches the cement paste surface. Finally, plunger was released allowing it to sink into the paste. The reading was noted on the gauge. The following procedure was repeated by taking fresh samples of cement and different proportions of water until the reading on the gauge is 5 to 7 mm. Similarly, the same methodology was adopted for the other categories of cement for the determination of consistency of cement pastes.

1 4. RESULTS AND DISCUSSIONS:

S.No	Category of Cement	Weight of cement (gm.)	Proportion of Water (%)	Amount of Water (ml)	Penetration of Plunger (mm)
1	Ordinary Portland Cement (OPC)	400	26%	104	11
2		400	28%	112	9
3		400	30%	120	6
1	White Cement	400	26%	104	13
2		400	28%	112	11
3		400	30%	120	7
1	Sulphate Resistant Cement (SRC)	400	26%	104	10
2		400	28%	112	8
3		400	30%	120	6
1	Ordinary Portland Cement with Sulphate Resistant Cement	400	26%	104	6
2		400	28%	112	5
3		400	30%	120	3

Table 2: Consistency of Different Cement Pastes with the Proportion of Water.

The above table depicts the proportion of water added in the same amount of different category of cement to determine the depth of penetration of plunger in the cement paste in millimeter. It is to be observed that depth of penetration of plunger calculated at 26%, 28% and 30% of water added in the 400 grams of cement such as Ordinary Portland Cement (OPC), White Cement, Sulphate Resistant Cement (SRC) and Ordinary Portland Cement (OPC) with the addition of Sulphate Resistant Cement (SRC). The depth of penetration of plunger is comparatively different for different categories of cement.

Figure No.1: Vicat Apparatus with OPC

Figure No.2: Plunger of Vicat Apparatus

Figure No.3: Vicat Apparatus with White Cement

Figure No. 4: Scale and Plunger of Vicat Apparatus

The figures represent that plunger of Vicat apparatus is penetrated in the cement paste and reading can easily be interpreted by looking at the scale next to the plunger in the Figure 4 where line of the plunger coincides with the scale. This is the way to interpret the reading of depth of penetration of plunger in the Vicat apparatus to determine consistency of cement paste. It is to be observed that cement paste is uniformly mixed and properly placed in Vicat mould of the Vicat apparatus. It is important to keep remember that proportion of water should be gradually added in the cement and mixing should be proper to attain uniform cement paste. The paste may not be too dry nor to be too wet. This could result that standard consistency will not be achieved. However, necessary attention and precaution should be required.

Figure No. 5: Graph represents consistency of different category of cement.

The above graph represents proportion of water added in the different categories of cement in the varied percentages on the x-axis and depth of penetration of plunger in millimeter on y-axis. It shows that depth of penetration of Ordinary Portland Cement (OPC) is comparatively high with the incorporation of 26% of water and it decreases with the addition of increased amount of water. The other two categories of cement such as White Cement and Sulphate Resistant Cement approximately follows the same pattern and both of them got standard penetration of plunger in millimeter with the addition of 30% of water. In this scenario, the depth of penetration of plunger is different for White Cement and Sulphate Resistant Cement such as 7 mm and 6 mm respectively. The interesting phenomenon is that blended mixture of Ordinary Portland Cement and Sulphate Resistant Cement follows entirely different patter from the other three categories of cement. The standard depth of penetration in millimeter is achieved at the percentage of 26% of water addition. It means that the properties of cement may significantly be changed by mixing different types of cement.

The results show that different categories of cement achieve standard consistency at different percentages of water in the cement. It is to be observed that environmental factors such as temperature and humidity were consistent throughout the investigation, even though, standard consistency of Ordinary Portland Cement, White Cement and Sulphate Resistant Cement are achieved at 30% of water addition while standard consistency of blended mixture of Ordinary Portland Cement with Sulphate Resistant Cement is achieved at 26% of water addition. Furthermore, the depth of penetration of plunger in millimeter is different for different categories of cement.

5. CONCLUSION:

It is to be concluded that the chemical composition of cement have major impact on the consistency of cement and consistency of cement may be achieved early or later by mixing different cements at consistent environmental factors such as temperature and humidity. It is to be observed that depth of penetration of plunger in millimeter decreases with the increase in proportion of water added in the cement.

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