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GROUP 15 – CEM Laboratory LABORATORY 1,2 AND 3 CIVIL ENGINEERING MATERIALS (VDB 2013) GROUP MEMBERS (GROUP 15) 1 Afnan Munir bin Mohd Khairi 23779 2 Ashikin Mastura binti Amirudin 23859 3 Thooy Kok Yaw 23876 4 Muhammad Haziq Hazim Bin Abd Halim 23901 5 Mohammed Jehad Kishawi 24791 6 Nur Ain Syafiqah...

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GROUP 15 – CEM Laboratory

LABORATORY 1,2 AND 3 CIVIL ENGINEERING MATERIALS (VDB 2013)

GROUP MEMBERS (GROUP 15) 1

Afnan Munir bin Mohd Khairi

23779

2

Ashikin Mastura binti Amirudin

23859

3

Thooy Kok Yaw

23876

4

Muhammad Haziq Hazim Bin Abd Halim

23901

5

Mohammed Jehad Kishawi

24791

6

Nur Ain Syafiqah binti Abdul Halim

25598

GROUP MEMBERS

GROUP 15 – CEM Laboratory

GROUP 15 – CEM Laboratory

CONCRETE MIXING Date of laboratory: 4th October 2017 MIXING AND SAMPLING FRESH CONCRETE OBJECTIVE To mix and sample fresh concrete in the laboratory. INTRODUCTION Concrete is a hardened building material created by combining a chemically inert mineral aggregate (usually sand, gravel, or crushed stone), a binder (cement), chemical additives, and water. The most crucial step in this process is to determine the proportions of ingredients that will make up the concrete. There are many variables to consider during the calculations. Some of them are cement type, aggregate size and type, amount of water, and mineral and chemical admixtures. While a good mix design can still result in inadequate or poor-quality concrete if it is not executed correctly, a bad mix design will of course always give poor results. Therefore, before the process of mixing, calculations of proportion of material must be done. In the industry, the process of producing concrete starts with batching which means weighing of all the materials needed to make the concrete. This is followed by mixing, transporting, placing, compaction and curing. In this laboratory session, we did a small-scale mixing of concrete. All the processes were done but in small scale, which was up to six small cubes of concrete. For our concrete, the expected strength is 55 MPa. APPARATUS A non-porous timber or metal platform, a pair of shovels, a steel hand scoop, measuring cylinder and a small concrete mixer, weighing machine, 6 cube molds. PROCEDURE

GROUP 15 – CEM Laboratory

1. The quantity of cement, sand and coarse aggregate were weighed according to the ratio that was calculated earlier. (appendix 1) 2. Sand and coarse aggregate were put into the mixing machine and was mixed for 1 minute. 3. Half of water needed were added to the mixer, and was mixed for 1 minute. Then it was left for 8 minutes. 4. Then, the cement was added to the mixer and was mixed for 1 minute. 5. The remaining volume of water was added and was mixed for 1 minute. 6. Then, the mixture was hand mixed to ensure homogeneity. 7. Three tests of workability were carried out while the concrete was hand-mixed to make sure it will not harden. 8. After done with workability test, the concrete was then filled into 6 cube mould. Then it was put on a vibrating machine to compact it. 9. It was then left for 24 hours. 10. After 24 hours, the concrete cubes were then demolded and was put inside a tank full of water in the curing room for curing process. Precaution 1. The room temperature should be approximately 25-27°C. 2. Make sure that fine and aggregate are dry. If they are wet find the content of the aggregates to determine the quality of water required.

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RESULTS/OBSERVATIONS

Figure 1 After machine mixing Before the mixing, all the materials were very segregated. We understood the steps of mixing in the lab manual before starting the experiment. After the mixing, the mixture become more homogenous, and the color was darker compared to before mixing. The mixture became very thick and quite difficult to hand-mix them. From the Figure 1, we can obvious that most of the aggregates were well coated by the cement paste with the help of water and this indicate that all the materials were well mixed. Then, this was followed by hand-mixing to ensure the homogeneity of mixture so that the paste is encapsulating the aggregates hence the required concrete can be made.

DISCUSSION (Afnan Munir Bin Mohd Khairi 23779) Concrete mix design is a process of selecting suitable ingredients of concrete and determining their relative quantities. Before conducting the experiment, some calculation have been made for determining the target mean strength, water/cement ratio, free water content, cement content, fine and coarse aggregates. All the values obtained according to the specified strength given which is 55 MPA.

GROUP 15 – CEM Laboratory

Some preparations like we have to dry the fine and coarse aggregates one day before for ensuring that there is no excess water in the concrete mixing. After measuring all the component according to the value calculated, we started to mix the fine and coarse aggregates with half of water the followed by half of cement. The mixture was mixed for a few minutes and then another half of water and cement were added. This step must be followed in order to make sure that all aggregates will be well coated by the cement so that the concrete will be more efficient due to compression. To achieve a higher strength concrete (55 MPa), the water-cement ratio must be low, but this will reduce the workability. Thus, a lot of effort needed here while “hand mixing” to prevent the hardening. Reliability 1.

The fine aggregate are not fully dried

2.

The fresh concrete were hardened too fast due to lack of hand mixing.

3.

The weighing scale was not set to zero while weighing.

Modification 1.

Make sure that the fine and aggregate is fully dried by exposing it to the sunlight.

2.

Make sure the fresh concrete is mixed frequently.

3.

Make sure the weighing is set to zero.

(Ashikin Mastura 23859) By carrying out this experiment, we were able to determine the production of concrete mixing. the first step into making the concrete is batching of materials. We had to measure and separate the ingredients so that it will be ready for the next step. This consists of fine aggregates, coarse aggregates, water and cement. Next step in to the procedure is the mixing of materials. Sand and coarse aggregates were added first followed by half volume of the water. This will ensure the aggregates are coated, into a blend all ingredients of concrete into a uniform mass. then, cement was added into the mixer creating a bind between water and aggregates that was initially added. As mixing continues, we observed that the colour turned from gray to a deep gray colour. the last

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portion of cement was then added with the other half of the water to ensure homogeneity. Next step is transporting from the mechanical mixer to the wheelbarrow and continuing mixing manually. The fresh concrete needed to achieve a 55 MPa of concrete strength. Hence, the watercement ratio was carefully calculated to ensure target can be aimed.

(By: Thooy Kok Yaw 23876) From this experiment, we were able to know and learn the steps of concrete mixing. Before starting the experiment, we were done for the batching of materials as we did the measurement of all materials used in production of concrete. Furthermore, fine aggregate such as sand was dried one day before the experiment start to ensure there is no excess water amount in the mixing. Sand and coarse aggregates were added in the mixer first followed by half volume of the water. This is to ensure the aggregates were well coated by the water. Then, cement was added into the mixer and coated with aggregates easily due to the water that was already on the aggregates that acted as a ‘glue’. After that, most of the surface of aggregates were coated with cement paste as the colour of the mixing became darker and darker. After the addition of cement, another half volume of water was added in the mixer to ensure a homogeneity and of mixing. The fresh concrete after mixing was poured into a wheelbarrow then followed by handmixing to prevent the fresh concrete from setting too fast. The lower the water-cement ratio, the higher the strength of concrete but the lower the workability of concrete. To reach the concrete strength requirement which is 55 Mpa, more force was needed from us to do the hand-mixing due to the low water-cement ratio. Reliability 1. The fine aggregates such as sand was not dried completely before weighing and mixing and causing a higher water content in it. 2. Make sure the mixing machine was free from contamination of impurities.

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3. Not all the aggregates were capsulated by the cement paste due to lesser time of mixing. Modification 1. Expose the fine aggregate such as sand under the sunlight one day before the experiment start to ensure it is dry enough. 2. Clean the mixing machine with water and let it dry before placing the materials in it for mixing. 3. Make sure the procedure of mixing of mixtures is correct by mixing with the specific time.

(By Muhammad Haziq Hazim Bin Abd Halim, 23901) From the experiment conducted we have learned the correct steps on how to make concrete based on the strength given. There are five components needed in making concrete which are sand, fine aggregates, coarse aggregates, water and cement. Concrete mix design is a process of selecting suitable ingredients of concrete and determining their relative quantities. Before conducting the experiment, some calculation has been made for determining the target mean strength, water/cement ratio, free water content, cement content, fine and coarse aggregates. All the values obtained according to the specified strength given which is 55 MPA. Some preparations like we have to dry the fine and coarse aggregates one day before for ensuring that there is no excess water in the concrete mixing. After measuring all the component according to the value calculated, we started to mix the fine and coarse aggregates with half of water the followed by half of cement. The mixture was mixed for a few minutes and then another half of water and cement were added. This step must be followed in order to make sure that all aggregates will be well coated by the cement so that the concrete will be more efficient due to compression. After mixing, we can see that all aggregates have been well coated, and the color of cement turned to be darker rather than before. The fresh concrete was poured in the wheelbarrow and we have to hand mix the paste to prevent it from setting too fast. We have found that the paste

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was quite hard to mix by hand because the water cement ratio is low in order for the concrete to achieve the target strength. So, from that we can assumed the workability of the concrete is low before the tests will be perform on the concrete.

Reliability 1. The measurement of the fine and coarse aggregates was not accurate due to the excess water contain. 2. Zero button on the weighing scale was not calibrated correctly. 3. The paste found to settle too fast. Modification 1. We have to dry the fine and coarse aggregates under the sun at least one day before 2. We have to make sure that the scale was set to zero before the measurement taken. 3. Everyone have to take part in the hand mixing as it need to be more often mixed.

(By: Mohammed Jehad Kishawi 24791) Before we started the experiment, we made sure that we know the steps and how to conduct it, as first we need to do the batching which is taking note of the materials that will be used with its amount. Then, the fine aggregate was dried a day before conducting the experiment to make sure the percentage of water in aggregate is low or even removed. Once the water aggregate is fully dried we proceed to mixing, were here we added the coarse and fine aggregates in the mixer with ½ the volume of our current water for 1 minute, then leave it for 8 minutes so flocculation can take place. Then, OPC were added to the mixer with the remaining water and some admixtures if needed and mixed for 1 minute, as the color goes darker it indicates that the aggregates surface is coated by the cement, after we are done mixing, now

GROUP 15 – CEM Laboratory

we transport the fresh mixed concrete in site, while transporting it using the wheelbarrow we did hand mixing to prevent it from hardening. To achieve a higher strength concrete (55 MPa), the water-cement ratio must be low, but this will reduce the workability. Thus, a lot of effort needed here while “hand mixing” to prevent the hardening. Reliability 1. The fine aggregate is not fully dried 2. The fresh concrete was hardened too fast due to lack of hand mixing. 3. The weighing scale was not set to zero while weighing. Modification 1. Make sure that the fine and aggregate is fully dried by exposing it to the sunlight. 2. Make sure the fresh concrete is mixed frequently. 3. Make sure the weighing is set to zero.

(Nur Ain Syafiqah binti Abdul Halim, 25598) As concrete is made up of different component which are water, coarse and fine aggregate and also cement, mixing has to be done to make sure all substances are mixed well together. The objective of mixing is to coat surface of aggregate with cement mix and water is needed for hydration process to occur. After the mixing process, we can see that all the substances are well mixed and homogenous, compared to before mixing. All the aggregate has been coated with cement mix. This is to make sure the concrete will function as it should be, which is to resist compression. The colour is darker than before as the cement has reacted with water, therefore it appears darker than before mixing. The mixture also become a thick paste and quite difficult to hand-mix it as the water cement ratio is low. This is because the strength expected for the concrete mix is quite high which is 55 MPa. Therefore, we can expect that the workability will be low.

GROUP 15 – CEM Laboratory

Concrete mixing is very important process in construction as most of buildings nowadays is made up of concrete, and usually is reinforced with steel. But the most important step in mixing is the compaction as it prevents void in the concrete. Presence of void will affect the buildings greatly. Curing which was the last step is to make sure the hydration to continue so that the concrete will achieve its greatest strength. In the big scale, usually contractor will put gunny sack at the concrete and sprinkle with water to cure the concrete. Reliability 1. Water might present in aggregate making the weighing inaccurate. 2. Impurities in the container while doing the batching process might affect the weight of the materials when it was weighed. Modification 1. Dry the aggregate under the sun before weighing. 2. Make sure container to do batching process is cleaned before weighing to avoid any impurities or inaccuracy.

CONCLUSION As a conclusion, from this experiment we have learnt on how to do concrete mixing. We can say that the objective, which is to mix and sample fresh concrete in the laboratory is achieved. Other than that, we also learnt the importance of each steps of production of concrete, by doing it in small scale in the laboratory.

GROUP 15 – CEM Laboratory

SLUMP TEST - TEST FOR WORKABILITY OBJECTIVE To measure the workability of a sample from a batch of fresh concrete of a given. INTRODUCTION/THEORY Slump is a measure of the consistency of fresh which is measured by carry out the concrete slump test. The concrete slump test measures the consistency of fresh concrete before it sets. It is performed to check the workability of freshly made concrete, and therefore the ease with which concrete flows. It can also be used as an indicator of an improperly mixed batch. The slump test is used to ensure uniformity for different loads of concrete under field conditions. The measurement of the workability of fresh concrete is important in assessing the practicality of compacting the mix and in maintaining consistency throughout the job. In this test, we have set the slump of the concrete to be 100mm. The concrete is filled into the mould and lifted to measure the slump. The difference between height of mould to height of the concrete after the mould is lifted is the measure of slump. In addition to this, there are few type of slumps as shown in (figure 1).

Figure 1 Type of slump

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APPARATUS Truncated conical mould 100mm in diameter at the top, 200mm at bottom and 300mm high, with a steel tamping rod (16mm diameter & 600mm long), rounded at one end, a scoop, a steel ruler and a steel trowel. PROCEDURE 1. The inside of the mold was cleaned and was placed on a hard, flat and non-absorbent surface. 2. Some sample was taken out from the fresh concrete mix. 3. The mold was filled with fresh concrete till one fourth of the mold and the layer was rodded 25 times with rounded end of steel rod. The rodding was make sure to pass through the high of each layer. 4. Step 3 was repeated until the mold is fill until the top. 5. After the top layer has been rodded, the surface of the concrete was struck off with a trowel to level up with the top of the mold. 6. The spillage of concrete spillage around the base of the mold was cleaned away. 7. The mold was carefully and slowly lifted vertically from the concrete. The mold was inverted and placed next to the molded concrete. The concrete slumped. 8. The rod was placed across the top of the mold. 9. The difference between height of slumped concrete and the mold was measured. By using steel ruler, the slump of top concrete to underside of the rod was measured. 10. The difference was recorded.

Figure 2 Measuring difference in height for the slump

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RESULTS The difference in height = 10mm DISCUSSION (AFNAN MUNIR BIN MOHD KHAIRI 23779) Concrete slump test is to determine the workability or consistency of concrete mix prepared at the laboratory or the construction site during the progress of the work. Generally concrete slump value is used to find the workability, which indicates water-cement ratio, but there are various factors including properties of materials, mixing methods, dosage and admixtures. During the lab session, we take an amount of concrete and fill it into the frustum of steel cone in three layers. Then, we are required to hand tap the concrete by tampering 25 times by using a steel rod. After the steel cone is filled and tampered, we turn the cone upside down and start to measure the slump as downward movement of concrete. Based on the result, we get 10 mm of slump which can be called true slump. As we have high number of target strength which is 55 Mpa,we need to use low content of water cement ratio.Thus,this result in low value in our slump test. Reliability 1. Slump test should not be carried out if the aggregates used is 40 mm. 2. Slump test won’t suit for the concrete mixture that is very dry concrete because it doesn’t show the differences in heights. 3. Parallax error might be done by the person in charge during taking the measurement of the components. 4. Concrete might not be thumped perfectly as the force applied each time released the rod was not same. Modification 1.

We have to make sure that the aggregates used were below than 40 mm.

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2.

We should performed a relevant calculations so that slump test can be carried out for

the concrete. 3.

The person in charge must place the eyes perpendicular to the scale to get the accurate

result. 4.

We have to make sure that the rod must be released at approximately at the same

height to obtain same forces for every thumping process.

(Ashikin Mastura, 23859) Concrete slump test is to determine the workability or consistency of concrete mix prepared during lab session during the progress of the work....