Conrete Mix Lab

1 | P a g e Concrete Mix Design – Group 5 11

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Concrete Mix design

Laboratory Report – GROUP 5

Member of staff: Dr. Peter Domone

Personal Tutor: Dr. Andy Chow

Submission date: Friday, 11th of February

Tarek Cheaib Luqing Shi

Junyan Chen Nicholas Chen

Fivos Lagios Philip McClintock Di-Pauli


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Table of Contents 1. Introduction .................................................................................................................................... 3

2. Objectives........................................................................................................................................ 3

3. Methodology ................................................................................................................................... 3

3.1. Aggregate properties .............................................................................................................. 4

3.2. Mix Design ............................................................................................................................... 5

3.3. Concrete Mixing ...................................................................................................................... 5

3.4. Fresh Concrete Testing ........................................................................................................... 5

2.5. Hardened Concrete Testing and Re-evaluation ...................................................................... 7

4. Concrete Mixture 1 ......................................................................................................................... 7

4.1. Target Mean Strength ............................................................................................................. 8

4.2. Free water/cement ratio ......................................................................................................... 9

4.3. Free water content ................................................................................................................. 9

4.4. Cement Content .................................................................................................................... 10

4.5. Total aggregate content ........................................................................................................ 10

4.6. Fine and coarse aggregate content ....................................................................................... 11

4.7. Final trial mix proportions ..................................................................................................... 11

5. Batch Calculations ......................................................................................................................... 11

6. Testing ........................................................................................................................................... 13

6.1. Fresh Concrete ...................................................................................................................... 13

6.2. Hardened Concrete ............................................................................................................... 13

7. Concrete Mixture 2 - Revised ........................................................................................................ 14

8. Problems encountered during mixing testing .............................................................................. 18

9. Final results ................................................................................................................................... 18

10. Cost of concrete ........................................................................................................................ 18

11. Embodied Energy and Carbon content ..................................................................................... 19

12. Conclusion ................................................................................................................................. 20

13. Appendix ................................................................................................................................... 21

14. References ................................................................................................................................ 22


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1. Introduction

On the 21st January, 2011, Group 5 carried out the first stage of an experiment whose aim was to design and produce a concrete mix based on a characteristic strength given to each group. The process involved calculating the proportions of the four main components of concrete: cement, water, fine and coarse aggregate respectively. In our case, the use of admixtures was omitted from the design process. Subsequently, a second stage followed after 7 days, where the hardened concrete was tested to see whether it fails at not less or more than the required compressive strength. Due to lack of compliance, the mixture was re-evaluated to produce a new concrete mixture that if tested, we hope to achieve the required strength.

2. Objectives

The objective of the laboratory is to design, produce and test a concrete mix such that it meets the requirements given for each group. Essentially the ultimate aim is to establish the proportions of cement, water and fine and coarse aggregate for a concrete mix that not only meets the strength required by the contractor but also produces an economic mix that reduces the total costs and the impact on the environment (i.e. the amount of carbon dioxide produced as a result). The concrete specifications are as follow:

- Compressive strength class at 7 days: C25/30

- Therefore the characteristic strength at 7 days is 30 MPa for cube concrete casting.

- Slump Class: S2

Table 1 Slump classes for concrete

Slump classes

Class Slump (mm) S1 10-40 S2 50-90 S3 100-120 S4 160-210 S5 ≥ 220

Therefore according to table 1, the required slump during the testing of fresh concrete must be within the 50 to 90 mm range to ensure the correct consistency of the concrete.

3. Methodology

The procedure by which the optimal concrete mix is derived is separated into several steps that require meticulous calculations and testing. The laboratory itself is split into two phases: the first half compromises of the design of the concrete mix and fresh concrete testing and the second half is that of the testing of the hardened concrete. The mix design method used is based on the most common UK method, that suggested by the Building Research Establishment – “Design of Normal Concrete Mixes (1997)” (1). The four steps below identify the principle procedures by which the final concrete mix is given at the end of the report.


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3.1. Aggregate properties

The size, type and grading of the aggregates and the cement type must be known in order to determine the density of the concrete. This will subsequently allow for the calculation of the final mix proportions of the concrete mix. Using the aggregates provided, a sieve analysis was carried out to determine the size of each aggregate and the percentage retained at each sized particle (table 2). This will help us distinguish between the fine and coarse aggregates.

Table 2 Results for the sieve analysis of the aggregates

sieve size (mm)

Fine aggregate Coarse aggregate

Total sample weight= 3463 g

weight retained(g)

percent retained

percent passing

weight retained(g)

percent retained

percent passing

40 0 0.00 100.00 0 0.00 100.00

20 0 0.00 100.00 133 9.41 90.59

10 0 0.00 100.00 787 55.70 34.89

4 126 6.15 93.85 471 33.33 1.56

2 301 14.68 79.17 0 0.00 1.56

1 207 10.10 69.07 0 0.00 1.56

0.5 515 25.12 43.95 0 0.00 1.56

0.25 778 37.95 6.00 0 0.00 1.56

0.125 97 4.73 1.27 0 0.00 1.56

pan 26 1.27 0.00 22 1.56 0.00

total 2050 100 100 1413 100 100

Using table 2, we are able to draw an aggregate grading curve that is used in section 4 of the report to determine the percent of fine aggregate passing 0.6 mm of sieve subsequently allowing us to derive the proportion of fine aggregate required for a specific slump of 50 to 90 mm.

Figure 1 Overall grading curve for combined aggregates


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The cement type used is CEM I class 52.5N Portland cement.

3.2. Mix Design An initial estimate of the trial mix proportions, that will give the concrete with required properties as specified by the contractor, is produced. It is important to acknowledge that the mix produced is merely a best estimate as the constituent materials will not be exactly as assumed and their interaction cannot be predicted with any great certainty (2). Also due to the fact we have no previous knowledge or results of the same type of concrete mix, in order to determine its behaviour and properties, we have to rely on the typical behaviour of concrete. Based on the idea that the strength is mainly dependant on water/cement ratio and consistence (workability) is mainly dependant on water content (assuming the same cement, coarse aggregate type and age), we follow a step by step method illustrated in section 4 of this report.

3.3. Concrete Mixing Once the batch weights have been calculated in the previous step, the concrete mix can begin in the laboratory. Each component of concrete is measured and placed in the concrete mixer. The concrete mixer is a device that mixes homogonously the weighted cement, aggregates and water, typically used on site. It operates using a revolving drum to mix the components (3). The interior surface of the concrete mixer is dampened to retain the cement powder. Whilst it is rotating at an angle of roughly 45 degrees, all the solid materials are placed in the following order: fine aggregate, Portland cement, coarse aggregate and water. When placing the water, we prolong the process over a period of one minute to avoid the cement powder from being dispersed in the air and also to render a more homogenous mix. We then mix for another 2 minutes and allow for the concrete to stand still for another 1 minute. Following this break, we further mix for another 30 seconds, after which the fresh concrete mix is ready for testing. It is important to control the amount of water added as too much or too little will reduce and increase the consistency respectively. A good mix should be smooth and plastic, not wet and runny or dry and crumbly (4). Also, the machine should be kept running throughout the process to allow for a homogenous mixture. As a safety measure, when handling the Portland cement, a mask should be worn at all times to avoid breathing in the cement dust. In the event that the wet concrete comes in contact with skin, it is essential that we wash it off immediately with water as it tends to release an alkali which damages the skin (4).

3.4. Fresh Concrete Testing Once the mixture is ready, it is to incur three different tests as described below:

1. Slump test Essentially, the slump test is an empirical test that measures the workability of fresh concrete. In order words it checks the consistence of the concrete and whether is remains so over a short period of time. The following is the brief procedure by which we carry out a slump test (5):


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1. We dampen the inside of the cone shown in figure 2 and place it on a smooth, non

absorbent flat surface (that is also dampened), large enough to accommodate both the slumped concrete and the slump cone. To ensure stability, as to avoid any flaws in the results, one person must firmly stand on the cone to stop it from moving.

2. Samples from the trial concrete mix are extracted using a spatula and used to fill 1/3 of the volume of the cone. Once completed, a long steel rod, preferably with a hemispherical tip, is used to tampered the mix exactly 25.

3. Step 2 is repeated another to times (at 1/3 intervals) until the cone is filled to the top.

4. Any excess concrete is removed using the tamping rod as a screed. Also the base of the cone is cleaned to avoid any obstructions.

5. The vertical cone is slowly lifted, without moving laterally. The inverted cone is placed to the side of the slumped concrete, without touching it.

6. The steel rod is laid across the top of the slump cone (as shown in figure 2).

7. By measuring the amount of slump from the bottom of the straight edge to the top of the slumped concrete, we subtract that from the total height of the cone (which is 300 mm) and we obtain the slump.

8. We use that value to compare it with the expected given value for the slump class shown in table 1.

Figure 2 Slump Test (6)


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2. Compactability Test

The compactability test essentially measures the consistence of the fresh concrete. A sample of fresh concrete is placed carefully in a container and allowed to descend gently to avoid any compaction while filing. When the container is full, the excess concrete at the top of the surface is struck off. The concrete is then compacted by the means of a vibrating table, allowing the dissipation of the voids in the concrete. This results in the reduction of its volume. The distance between the surface of the concrete and the top edge of the contained is then measure (see figure 3) at the mid-point of each of the four sides and the degree of compactability is measured using the formula below:

Degree of compactability =

Where:

Figure 3 Compactability Test

2.5. Hardened Concrete Testing and Re-evaluation

After 7 days, the hardened concrete cubes are now tested to see whether the trial concrete mix achieves its target mean strength of 43 MPa. If the compressive strength at which the concrete fails is indeed 43 MPa, then the concrete mix is successful. Otherwise, the mixture is re-evaluated, and all the proportions are re-calculated using the same process as described above. For more details, please see section 6 of the report.

4. Concrete Mixture 1 As stated in section 3 of this report, we will start off by calculating a trial mix for concrete following a step-by-step procedure. Since we have no previous knowledge of the concrete to be used, we will have to rely on a series of graphs identified in the sections to follow. The methodology and all graphs in this section are derived from source (2).


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4.1. Target Mean Strength Similar to all materials, the strength of concrete tends to change for the same sample of concrete. Thus an average cube compressive strength above the characteristic strength is required. To achieve a 5% failure rate (the normal value chosen for concrete) the margin (shown in figure 4) should be 1.64 times the standard deviation of the strength test results, found using figure 5.

Figure 4 Failure rate, margin and characteristic strength

The following graph depends on the quality control of the concrete sample. As already established, there is no previous data on the concrete therefore we use the upper values given in figure 5 which are estimates based on the upper limits found in practice. The target mean strength is then calculated. The standard deviation for a characteristic strength of 30 MPa = 8 MPa (using figure 5) The margin = 1.64 × 8 MPa = 13 MPa Thus the target mean strength = 30 MPa + 13 MPa = 43 MPa


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4.2. Free water/cement ratio It is safe to assume at this stage that the concrete strength is governed by the water/cement ratio as illustrated in the graph in figure 5. Using the calculated target mean strength, we can determine the free water/cement ratio. It is crucial to keep it mind that this value is not the same as the ‘total water’ as some of the water in the concrete will be absorbed into the pores in aggregates and therefore will not act to hydrate the cement. This difference will be made when making the batch calculations.

Figure 5 Approximate compressive strength vs. water/cement ratio for concrete with class 52.5 N Portland cement and

uncrushed coarse aggregate

The free water/cement ratio is thus calculated to be 0.46.

4.3. Free water content It is now assumed that for a given coarse aggregate type and maximum size, the concrete workability is governed by the free water content only. An estimate is determined using the required slump value of 70 mm respectively (assuming the middle value of 50 to 90 mm for class S2) and figure 6 below.

0.46


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Figure 6 Approximate slump vs. free water content for concrete with 20 mm coarse aggregate

Using the values for uncrushed aggregate, we find that the free water content for a concrete mixture with a slump of roughly 70 mm is 184 kg/m3.

4.4. Cement Content Having obtained the free water/cement ratio and the free water content using figures 4 and 5 respectively, we can carry out a simple calculation as follows to determine the cement content:

Free water/cement ratio =

0.46 =

Cement content = 400 kg/m3

4.5. Total aggregate content In order to calculate the total aggregate, we first need to estimate the density of the concrete using figure 6 which displays the assumed values of relative density of the specific aggregates (uncrushed in our case).

Figure 7 Wet density of fully compacted concrete vs. free water content

The obtained density is roughly 2360 kg/m3. By subtracting the known free water content and the cement content (184 kg/m3 and 400 kg/m3 respectively) we obtain the total aggregate content as being 1776 kg/m3.


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4.6. Fine and coarse aggregate content

The estimated value of the proportion of fine aggregate in the total aggregate is highly dependent on the maximum size of the aggregate, the concrete workability, the grading of fine aggregate passing through 600 micron sieve and the free water/ cement. In terms of the fine aggregate, we use figure 2 to find the percentage of fine aggregate passing through the sieve at 0.6 mm. This is found to be roughly 51%. Using this and the free water/cement ratio (0.44) and expected slump (70 mm), we use figure 8 below to find the proportion of fine aggregate.

Figure 8 Proportions of fine aggregate according to percentage passing 0.6 mm sieve for a slump of 60 to 180mm

Thus the proportion of fine aggregate required for the trial concrete mix is 40%. Thus knowing that the total amount of aggregates is 1776 kg/m3, we obtain the following: Fine aggregate content: 0.4 × 1776 kg/m3 = 710 kg/m3 Coarse aggregate content: 0.6 × 1776 kg/m3 = 1065 kg/m3

4.7. Final trial mix proportions Having calculated the aggregate content by simple arithmetic, we now have the final proportions in kg/m3 required for the trial concrete mix. These are summarized in table 3 below to the nearest multiple of 5: Table 3 Final trial mix proportions

Materials Proportions in kg/m3

Coarse aggregate 1065

Fine aggregate 710

Portland cement 400

Free water 185

5. Batch Calculations

The batch weights are required to produce the proportions of each material to produce 0.02m3 of concrete (roughly 50 kg). A series of simple calculations are made and illustrated below. In terms of

50


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the water content, the batch weights should be altered to allow for the water in the pores contained within the moist aggregates. The percentage absorption for each is given in table 4. Table 4

Materials Trial Mixed Proportions (kg/ m3)

Absorptions (% by weight)

Moisture Content (% by weight)

coarse aggregate 1065 1% 2.70%

fine aggregate 710 1.50% 2.80%

cement 400

water 185

It is crucial that the required water content for the mix takes into account this percentage absorption. This is because the free water is the main determinant of workability of the concrete mix and the amount that actually reacts with the cement. Since the batch weights of 0.02m3 of concrete are required, the total batch weight of coarse and fine aggregate and cement respectively are calculated my multiplying the trial mixed proportions in table 4 by 0.02m3 , obtained the values shown in table 5.

Table 5 Batch weights

Batch weight for 0.02m3

Coarse aggregate 21.3 kg

Fine aggregate 14.2 kg

Cement 8 kg

Total water content 2.7 kg

As for the free water content, we use the total water content and the following formulas: 1. Total weight of water = Total water content + (Batch Weight for coarse aggregate × absorption) +

(Batch Weight for fine aggregate × absorption)

Total weight of water = 3.7 + (21.3 × 0.01) + (14.2× 0.015) = 4.13 kg 2. Water already in the aggregates = (Batch Weight for coarse aggregate × moisture content) +

(Batch Weight for fine aggregate × moisture content)

Water already in the aggregates= (21.3×0.027) + (14.2×0.028) = 0.97 kg 3. Batch weight of water = Total weight of water – water already in aggregates = 3.2 kg

Table 6 Final batch weights for trial concrete

Batch weight

Coarse aggregate 21.3 kg

Fine aggregate 14.2 kg

Cement 8 kg

Water 3.2 kg

The final batch weights to produce 0.02 m3 of the trial concrete are given in table 6 above.


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6. Testing

6.1. Fresh Concrete Following the testing procedures for fresh concrete described in section 3.4.of the report, the slump for the trial concrete mix was obtained to be 10 mm, which is way less than the range of 50 to 90 mm. Since a true slump was produced, the test remains valid. That is to say that the concrete has low workability and thus new calculations for the concrete mix must be made accordingly. In terms of the degree of compactability, the mean value of the four distances from the surface of the compacted concrete to the upper edges of the container was found to be 100 mm. Using the formula below:

Degree of compactability =

where s = 100 mm and h1 = 400 mm, We obtain a degree of compactability of 1.33. For computability test, degree of Compactability testing should be in the range of 1.04 and 1.46 (7). Anything outside this range indicates that the concrete has a consistency for which the degree of compactability test is not suitable; however for our trial concrete mix, this is not the case.

6.2. Hardened Concrete

After 7 days of storage under controlled conditions, three samples of the mixed concrete were tested to see whether the compressive strengths were indeed as predicted (in our case: 43 MPa). Table 7 below illustrates the data.

Table 7 Compressive strengths

Cube 1 Cube 2 Cube 3

Compressive strength (MPa)

39.9 37.9 40.3

Seeing as the average compressive strength obtained (39.4 MPa) is lower than the required, we re-calculate the batch weights accordingly. This procedure is given in section 9 of this report and follows the same methodology as that used for the trial mix design. Also to ensure that there were no voids in the concrete cube castings or any possible defects, we calculated the densities of each cube and compared it to the expected value of the density found in section 4 of the report. The results obtained are given in table 8 on the next page.


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Table 8 Trial Concrete Mix Density

Cube 1 Cube 2 Cube 3

Weight in air(g) 2333 2362.5 2327.5

Weight in water(g) 1360 1380 1344

Failure load(kN) 398.5 379 403

=

Density of cube concrete 1=

*1000=2397.7 kg/m3


*1000=2404.58 kg/m3


*1000=2366.55 kg/m3

Since our expected density value is 2360 kg/m3 , cube 3 has the closed density to the expected on whilst the other 2 cubes are within a 10% discrepancy.

7. Concrete Mixture 2 - Revised

Even though the compressive strengths do not differ largely from our target mean strength, the value for the slump was found unacceptably lower than the expected value (see section 6). Nevertheless, adjustments will be made for both of the above mentioned properties. To begin with, using the average compressive strength obtained (39.4 MPa) we use figure 9 to find the value of the free water/cement ratio. However we first interpolate the line as shown in red below, adjusting for the actual values obtained (since we obtained a compressive strength of 39.4 MPa at 0.46 free water/cement ratio, we redraw the curve accordingly).

Figure 9 Recalculating the free water/cement ratio


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Where:

- Point A: tested compressive strength - Point B: target compressive strength

- 0.46 is the designed water/cement ratio in Mix design 1

- 0.44 is the revised water/cement ratio

Hence, a value of 0.44 is obtained as the new free water/cement ratio. Following the step-by-step method described in section 4, we now find the new free water content. We achieve this by using figure 10 and the obtained slump value of 10mm, in addition to interpolating the existing plot.

Figure 10 Recalculating the free water content

- 70 mm is the average slump value of slump class S2

- 10 mm is the tested slump value

- 187 kg/m3 Is the designed free water cement in Mix design 1

- 220 kg/m3 is the revised free water content

Hence we obtain a free water content value of 220 kg/m3, leading to a cement content of:

Cement content =

= 500 kg/m3

Once again assuming the relative density of our aggregate to be 2.6 and using our new free water content we use figure 11 as such:


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Figure 11 Re-calculating the density of the concrete

Hence, our new concrete density will be 2320 kg/m3. Now, we move on to calculate the aggregate content which will be: Aggregate content = Total Density – Cement content – Water Content = 2320 – 500 – 220

= 1600 kg/m3

Using figure 12 below, we then calculate the new proportion of fine aggregate, using our value of 0.44 for free water/cement ratio and a value of 51% as previously calculated for the percentage of fine aggregate passing 0.6mm sieve.

Figure 12 Re-calculating the proportion of fine aggregate


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Hence, the proportion of fine aggregate is found to be 32%. Then the fine aggregate content as well as the coarse aggregate content can be found to be: Fine aggregate content = 0.32×1600 = 512 kg/m3 Coarse aggregate content = 1600 – 512 = 1088 kg/m3 All values found through this adjustment will then be used to calculate the required batch weights of this second trial mix. Table 9 below summarizes the final results:

Table 9 Mixed proportions for mix 2

Materials Mix Proportions (kg/m3 )

Coarse aggregate 1088 Fine aggregate 512

Cement 500

Total water 220

Revised batch weights:

Table 10

Materials Mix props Absorptions Moisture Content Batch weight(kg)

Coarse aggregate 1088 1% 2.70% 21.96

Fine aggregate 512 1.50% 2.80% 10.34

Cement 500 10

water 220 (4.4)

Table.5 For 0.02m3 required batch weight: Total weight of water= 4.4 + (21.76*0.01) + (10.24*0.015) = 4.77 kg Water already in the aggregates= 21.76*0.027+10.24*0.028=0.874 kg Batch weight of water=4.77-0.874=3.90kg Therefore, the finial batch weight of each component is shown in table 11 below:

Table 11

Batch weight

Coarse aggregate 21.96kg

Fine aggregate 10.34kg

Cement 10kg

Water 3.9kg


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8. Problems encountered during mixing testing

Besides the limitations and assumptions made throughout the various sections of this report, there were little issues encountered throughout the actual process of mixing and testing. Some of the identified issues are listed below:

- The proportion measurements were subject to alterations, mainly that of cement. Due to its lightweight, when placed in the concrete mixer, a proportion of it dissipated in the air. This may account for some of the cement losses.

- When placing the water in the concrete mixer, so was lost on the asides. Additionally, the mixer was dampened before use but the water was not accounted for during the calculation of the total free water.

- When performing the slump test, it was difficult to keep the cone steady, thus minor vibrations may have allowed for the concrete to compact, thus reducing the slump value

- Also during the slump test, when tampering the sample at first, it was performed in roughly the same location, distributing the concrete unevenly in the cone.

9. Final results

The table below summarizes the final mix proportions of each component for both trial mixes and the requirements given.

Table 12 Final results

Requirement Trial Mix 1 Trial Mix 2

Compressive Strength 43 MPa 39.7 MPa NA

Material proportions (kg/m3):

- Fine aggregate NA 1065 1088

- Coarse aggregate

NA 710 512

- Cement NA 400 500

- Total Free water

NA 185 220

Density NA 2360 kg/m3 2320 kg/m3

Slump (mm) 50 – 90 10 NA

10. Cost of concrete The cost of each component used in the design of the concrete mix is given in the instruction sheets provided at the beginning of the laboratory. These are shown in table 13 below, where the total cost for 1 m3 of the second trial concrete was found to be £ 78.15. The standard price for concrete is normally around £80 as identified by individual concrete producers (8) thus the final cost proves to be credible. In the case that a more economical mix is required, the addition of admixtures would be a solution. They act to increase the strength, at the same time increasing the workability. This will allow a reduction in the use of both the water content and consequently the water/cement ratio (which means that less cement will be required) (9). In our case however, we have made the


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assumption that the contractor did not set a limit for the cost thus we have allowed for the cost to stay the same.

Table 13 Cost of concrete

Weight (kg/ m3 ) Cost (£/kg) Cost (£/m3 )

Coarse aggregate 1088 0.021 22.848

Fine aggregate 512 0.025 12.8

Cement 500 0.085 42.5

Total (per m3 concrete) - - 78.15

11. Embodied Energy and Carbon content

In terms of the embodied energy and carbon content, it was based on values provided by the ‘Inventory of Carbon and Energy (ICE)’ (10). Embodied energy of a building material can be taken as the total primary energy consumed over its life cycle. It normally includes the process of extraction of the material, manufacturing and transportation. One of the main assumptions made during our calculations is that we have taken the ‘Cradle –to-site’ embodied energy, thus includes all of the energy until the product has reached the point of use. Similarly we have also calculated the embodied carbon content. Table 14 below shows the figures for each of the materials used for the production of concrete. The total embodied energy was found to be 1.06 MJ per kilogram. Comparing this with the standard value for concrete of 1.11 MJ/kg (concrete used for in-situ floor slabs) (11), it contained less embodied energy however in terms of carbon, the total embodied carbon was found to be 0.182 CO2/kg whereas the standard value (for concrete used in in-situ slabs) is 0.159 Co2/kg. It is to say that the concrete produced is not the most environmentally friendly mixture thus requires alterations.

Table 14 Embodied energy and carbon content

Weight (kg/ m3 ) Embodied

energy (MJ/kg)

Embodied carbon (kg

CO2/kg)

Coarse aggregate 1088 0.1* 0.005*

Fine aggregate 512 0.1* 0.005*

Cement 500 4.6* 0.83*

Total (per m3 concrete) 2320 2460 423

Total (per kg concrete) - 1.060 0.182

Despite the fact that the total embodied energy of concrete is not that great in comparison to other materials in the construction industry (see appendix 1), it is the most used material used when constructing a house for instance. Therefore the total amount of embodied energy is much higher than that of any other material if we were to consider the amount used (figure 13). To avoid harmful environmental impacts (i.e. global warming due to collective increase in Co2 emissions), it is crucial to design a mix whose carbon footprint is as minimal as possible.


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Figure 13 Total embodied energy for materials used in housing (12)

12. Conclusion To conclude, having performed a re-evaluation of the concrete mix design, given the limitations, we can safely say that we satisfied the requirements given. However, there were some parts where our accuracy can be questioned namely our initial value for the slump. Nevertheless, there are several reasons that can justify the abovementioned, apart from encountered difficulties during the actual laboratory test itself. Some factors that may have influenced the results are the estimations made using our provided graphs and reading errors (visual judgment). Also, further assumptions made, including that of our uncrushed aggregate’s density being 2.6, when in reality it was unknown. Bad calibration of the equipment used (e.g. the scale) could be another reason for inaccuracies, with a chance of some zero-offset error possibly existing. As a final point, in order for us to improve our accuracy, the experiment should be repeated several times so that we are more confident about our results. A revised mix, illustrated in section 7, is performed however before we can be certain that the potential results adhere to the requirements, a series of tests must be performed to confirm our findings.


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13. Appendix

"Your Home Technical Manual - 5.2 Embodied Energy." Your Home Design Guide - Home Page. Web. 11 Feb. 2011. <http://www.yourhome.gov.au/technical/fs52.html>.


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14. References (1) Teychenne, D. C., R. E. Franklin, and H. C. Erntroy. "Design of Normal Mixes." Building Research

Establishment, 1997. (2) Domone, Peter, Illston, J. M., ‘Construction Materials – Their Nature and Behaviour’, Third Edition,

2001 (3) "Mixing Cement | Cement Mixer – Concrete Mixers Guide – How to Mix Cement." Cement Mixer –

Concrete Mixers Guide – How to Mix Cement | Compare Pros and Cons of Drum Concrete and Cement Mixers, and Learn How to Mix Cement. <http://www.cementmixer.com/mixing-cement.php>.

(4) "Mixing Concrete by Hand, Cement Mixer or Using Ready Mix." Do It Yourself Information and Advice. <http://www.diydata.com/general_building/concrete/concrete_mixing.php#mixer>.

(5) "Slump Test Procedure (Field Testing)." Gates - Concrete Forming Systems. Web. <http://www.gatesconcreteforms.com/pdfs/slumpTest.pdf>.

(6) Maripo, Goda, "File:Slump Test.png." Wikimedia Commons. <http://commons.wikimedia.org/wiki/File:Slump_test.png>.

(7) CALcrete (8) "Plastering Prices - How Much Will It Cost to Plaster Walls, Ceilings." Home Improvement and

Decoration Project Prices including Conservatory Costs. <http://www.whatprice.co.uk/building/plastering.html>.

(9) Domone, Peter, Illston, J. M., ‘Construction Materials – Their Nature and Behaviour’, Third Edition, 2001

(10)Hammond G ＆Jones C, INVENTORY OF CARBON＆ENERGY（ICE）Version 1.6a University of Bath, UK (11) GreenSpec - Green Building, Design, Products, Materials, Energy, Specification and Sustainable

Construction. <http://www.greenspec.co.uk/embodied-energy.php>. (12) "Your Home Technical Manual - 5.2 Embodied Energy." Your Home Design Guide - Home Page.

<http://www.yourhome.gov.au/technical/fs52.html>.

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