Precaution 1. 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. 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. 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.
Reliability 1. The fine aggregate are not fully dried 2. The fresh concrete were hardened too fast due to lack of hand mixing. 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. Make sure the fresh concrete is mixed frequently. Make sure the weighing is set to zero. Ashikin Mastura By carrying out this experiment, we were able to determine the production of concrete mixing.
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. As mixing continues, we observed that the colour turned from gray to a deep gray colour.
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 water- cement ratio was carefully calculated to ensure target can be aimed. By: Thooy Kok Yaw 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. 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 hand- mixing 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.
The fine aggregates such as sand was not dried completely before weighing and mixing and causing a higher water content in it. Make sure the mixing machine was free from contamination of impurities. Not all the aggregates were capsulated by the cement paste due to lesser time of mixing.
Expose the fine aggregate such as sand under the sunlight one day before the experiment start to ensure it is dry enough. Clean the mixing machine with water and let it dry before placing the materials in it for mixing. Make sure the procedure of mixing of mixtures is correct by mixing with the specific time. By Muhammad Haziq Hazim Bin Abd Halim, 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. 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 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. So, from that we can assumed the workability of the concrete is low before the tests will be perform on the concrete. The measurement of the fine and coarse aggregates was not accurate due to the excess water contain. Zero button on the weighing scale was not calibrated correctly.
The paste found to settle too fast. 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. Everyone have to take part in the hand mixing as it need to be more often mixed. By: Mohammed Jehad Kishawi 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. The fine aggregate is not fully dried 2. The fresh concrete was hardened too fast due to lack of hand mixing. Nur Ain Syafiqah binti Abdul Halim, 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. Water might present in aggregate making the weighing inaccurate. Impurities in the container while doing the batching process might affect the weight of the materials when it was weighed.
Dry the aggregate under the sun before weighing. Make sure container to do batching process is cleaned before weighing to avoid any impurities or inaccuracy.
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.
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 mm. 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. The inside of the mold was cleaned and was placed on a hard, flat and non-absorbent surface. Some sample was taken out from the fresh concrete mix. 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. Step 3 was repeated until the mold is fill until the top. 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. The spillage of concrete spillage around the base of the mold was cleaned away. 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. The rod was placed across the top of the mold.
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. The difference was recorded. 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.
Slump test should not be carried out if the aggregates used is 40 mm. Parallax error might be done by the person in charge during taking the measurement of the components. Concrete might not be thumped perfectly as the force applied each time released the rod was not same. We have to make sure that the aggregates used were below than 40 mm. We should performed a relevant calculations so that slump test can be carried out for the concrete.
The person in charge must place the eyes perpendicular to the scale to get the accurate result. 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, Concrete slump test is to determine the workability or consistency of concrete mix prepared during lab session during the progress of the work. Concrete slump test is carried out from batch to batch to check the uniform quality of concrete during construction. It can also be known as measuring consistency to determine rapidly whether a concrete batch should be accepted or rejected. During lab session, a sum of concrete was filled into the frustum of steel cone in three layers.
The concrete then was hand tap in each layer by tampering as much as 25 times using a steel rod. After filling three layers, the cone was lifted and then rotate to degrees upside down. This is to measure the slump as downwards movement of concrete.
From obtaining result, there is a slight slump in our mixture. This indicates the difference of height of the frustum with the height of concrete. The difference is 10 mm and the type of slump determined was a true slump. This means that the general drop of the concrete mass is evenly all around without disintegration. Although, we can also conclude that the workability of the concrete is low due to low optimization of water-cement ratio.
This test was performed to check the workability of freshly made concrete and therefore the ease with which concrete flows. After the removing of truncated conical mould, we were able to get a true slump with a 10 mm difference between height of slumped concrete and the mold. The fresh concrete was slumped due to the water-cement ratio and flow down by its own weight and this also know as slumping. The higher the water-cement ratio, the higher the workability and the bigger the difference of slump.
Since the targeted strength of our concrete is 55 MPa, only a low water- cement ratio is needed. Therefore, due to a lower water-cement ratio, our fresh concrete categorize under true slump as it is a low workability fresh concrete. Fresh concrete was well compacted each layers in the mould by using rounded end steel rod for 25 times.
This is to ensure that the fresh concrete obtain a higher cohesive and reduce the risk of segregation. Slump test is very convenient as the procedure is simple and easy than any other workability test. Besides, it is inexpensive and portable apparatus that can be performed at the construction site as well as in the laboratory.
The truncated conical mould was contaminated inside by some suspended solid. The fresh concrete was not compacted for each layers or the amount of compaction was less than 25 times. The compaction force on the fresh concrete at each layer were not applied uniformly. Parallax error happened when taking the difference between height of slumped concrete and the mold. Wash the truncated conical mould and let it dry before starting the experiment 2.
Make sure the fresh concrete was inserted one fourth of truncated conical mould each time and compact the fresh concrete well with 25 times by using rounded end steel rod.
Apply the same compaction force on the fresh concrete at the same height. Make sure the eyes of observer is perpendicular to the scale of meter ruler to obtain a more reliable result. By Muhammad Haziq Hazim Bin Abd Halim, Slump test is carried out to measure the consistency of concrete which indicates the workability of concrete. Consistency refers to the ability of the concrete to flow without the segregation of ingredients.
The more consistent of the concrete mix, the concrete is considered as stiff while the less consistent of the concrete mix, the concrete is considered as soft. The major factor that affect the consistency and workability of concrete is water cement ratio but there are more minor factor that affect the workability of concrete which are the size, shape, grading, surface texture of aggregates and also the use of admixture. From the slump test conducted, the difference of the slump is 10 mm which indicates it as true slump as concrete slumps evenly and forms a shape same as a mould.
Based on the result, we can say that our concrete mixture is stiff because of the workability is low. Less amount of water cement ratio is the one of major cause of having low consistency but if there is too much amount of water cement ratio, bleeding can take place.
So by doing slump test to the concrete, we can obtain adequate amount of water cement ratio for a specific strength. Our concrete mixture is still can be accepted as low water cement ratio is suitable for a quite high target strength which is 55 MPA.
Although it is very easy to perform this method. But it is not suitable for very wet or very dry concrete. It does not measure all factors contributing to workability and concrete placeability. This test often be used in construction industry as a control test and gives an indication of the concrete uniformity from batch to batch. Repeated batches of the same mix, brought to the same slump, will have the same water content and water cement ratio, weights of aggregate, cement and admixtures are uniform and aggregate grading is within acceptable limits.
By: Mohammed Jehad Kishawi For this experiment, a slump test is conducted to check the workability of our fresh concrete and how it flows. We filled the fresh concrete in the truncated conical mould and each layer being compacted 25 times to reduce the segregation, now we removed the truncated conical mold and we observed that the difference between height of slump concrete and the mold is 10mm, this is due to the exist of water in the fresh concrete.
Thus, it is categorized as a true slump. The methodology of slump test is basic and simple than some other workability tests, slump test can be performed at the development site and in the research facility. The slump test is limited to concretes with the maximum size of aggregate less than 38 mm, also the test is suitable only for concretes of medium or high workabilities i.
For very stiff mixes having zero slumps, the slump test does not show any difference in concretes of different workabilities. Parallax error occured while taking the reading of the difference height between the slump concrete and the mold.
Each layer got different height when the compacting force were applied Modifications 1 Make sure the size of the aggregate is lower than 38mm by the help of sieve analysis. Nur Ain Syafiqah binti Abdul Halim, The slump test result is a measure of the behavior of a compacted inverted cone of concrete under the action of gravity. It measures the consistency or the wetness of concrete. Generally concrete slump value is used to find the workability, which indicates water-cement ratio, but there are numerous factors including properties of materials, mixing methods, dosage, admixtures etc.
The difference is 10mm and type of slump we got was true slump. As the slump is quite low, we can say that the workability for the concrete is low. This is because the strength of our concrete mix is high, thus the water cement ratio is quite low. In the industry, slump test is used to ensure uniformity for different batches of similar concrete under field conditions.
This test is very useful on site as a check variation in the materials being fed into the mixer. An increase in slump may mean, for instance, that the moisture content of aggregate has unexpectedly increases.
This test is used to check the uniform quality of concrete during construction. The concrete was not thumped perfectly using rod as different force was given while thumping that may cause some variation. Concrete might stick to the conical mould.
Parallax error might occur while taking the reading of height difference. Release the thumping rod from about the same height and let it fall under influence of gravity for uniform force. Spread grease around inner part of mould to prevent concrete from sticking to the mould. In this experiment, we used slump test to measure the workability. This test usually used in the site to determine the consistency of fresh concrete from different batches.
The results from this experiment showed that the workability for the fresh concrete by our group is low as the slump is only 10mm. Good compaction is necessary in order to expel air voids in a fresh concrete mix. The presence of voids in concrete greatly reduces its strength. Five percent of voids can results in a drop of strength of more than 10 percent. The compacting factor is defined as the ratio of the weight or partially compacted concrete to the weight of fully compacted concrete and is normally stated to the nearest second decimal place.
The apparatus have been cleaned from any superfluous moisture. The empty cylinder was weighed and the mass have been recorded in gram. Fasten the hopper trap door with the catches. The cylinder was fixed on the base of the apparatus. The cylinder top have been covered with two steel trowels. The top hopper have been gently filled with concrete sample by using a hand scoop until full. Level off or tamp or compact was not allowed. The trap door of the top hopper was opened to allow the concrete to fall into the second hopper.
We have confirmed that no concrete sticks in the top hopper. The steel trowel was removed from the top cylinder and trap door of the lower hopper have been released to allow the concrete to fall into the cylinder.
The top of the cylinder have been leveled and spillage was removed from outside the cylinder. The cylinder was weighed with the partially compacted concrete. The mass have been recorded in gram. The concrete have been taken from the cylinder. The cylinder was refilled with the same concrete in layer approximately 50mm deep.
Each layer was compacted by using a tamping rod for 35 strokes. The top was leveled and the spillage was cleaned. Then the mould was weighed with fully compacted concrete. Note the mass in gram. Test should be carried out on a level surface or ground. The hopper and cylinder must be thoroughly clean and dry. If concrete sticks within the hoppers, push the concrete gently by using a tamping r d. The outside of the cylinder must be wiped clean before weighing.
The test can be carried out within a period of 2hours from addition of water to the mix. The degree of compaction, called the compacting factor is measured by the density ratio which is the ratio of the density actually achieved in the test to density of same concrete fully compacted.
For the experiment,we are doing the test for fully compacted concrete and partially compacted concrete. The result of compacting factor for is 0. This is mainly due to the low content of water cement ratio. As we need to achieve 55 Mpa strength,low water cement ratio is needed to gain that strength.
From the experiment,we can observe that the weight of the partially compacted concrete is lower than fully compacted concrete. This due to more spaces or void and air bubbles inside which cause the density of the concrete to become low. Some other impurities might be found stick or left on the apparatus. Zero button on the weighing scale was not calibrated to zero. The concrete was not thumped perfectly to make the concrete compact. The apparatus should be clean before the experiment conducted.
The person in charge for the thumping process should know the correct way for the process. We have to make sure that the scale must be zero before weighing the concrete and cylinder.
During lab session, the concrete was filled but not compacted. Next, the door below was opened. The cement is now dropped to the bottom cylinder. The excess concrete was struck off the top layer. Then the mass of the concrete is recorded.
From the results obtain, we used the equation given to determine the compacting factor and it was 0. The recorded value is considered to have low workability. This may due to the water- cement ratio that was not enough mixed to the concrete mix to achieve optimum value to pass compacting factor.
Hence, the lower the water, the lower the workability. By: Thooy Kok Yaw We were able to find out the workability by calculating the compaction factor of our fresh concrete in compacting factor test. Compacting factor can be defined as the ratio of concrete that fall in a cylinder with the help of gravity to the weight of fully compacted concrete in the same cylinder.
The compacting factor for our fresh concrete is 0. This is due to the low water-cement ratio of the fresh concrete. For example, if the fresh concrete has a higher water-cement ratio, more fresh concrete will be flowing into the cylinder resulting an increasing of weight and causing a higher ratio of compacting ratio. Besides, a higher water-cement ratio of fresh concrete can flow easily with the help of gravity as they behave more fluidity and mobility compared to a lower water-cement ratio fresh concrete.
Furthermore, more force was needed to compact our fresh concrete as it behave in low workability. The lower the water-cement ratio, the more difficult to compact the fresh concrete. General Science Notes — Click.
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