**4. Method**

bricks [25], its use in the production of SCC has been much less explored [26]. Due to the minerology of shale, SA contains relatively high content of calcium oxide, usually in the range of 10–40%. The pozzolanicity of SA is similar to that of GGBS, and it has a silica content of 30–40%. In terms of chemical composition, SA can be classified as calcium-alumino-silicate dominated, with a subtle content of aluminium oxide. The addition of SA in concrete had been reported to increase the concrete strength, reduce the permeability and improve frost resistance [27]. However, the alkali content in SA is generally at the high side, and the content of SA in concrete should be limited to

116 Sustainable Buildings - Interaction Between a Holistic Conceptual Act and Materials Properties

MS (also called condensed silica fume) is a by-product of the smelting process used to produce silicon metal and ferrosilicon alloys. MS is characterised by the high content of reactive silica of over 85% and the extremely fine particle size in the order of 0.2 μ. The high fineness of MS allows it to fill the voids between larger cement particles and increases packing density. The displaced water becomes excess water to lubricate the solid particles. From mix design perspective, the water demand for packing is greatly reduced and a lower W/CM can be used for achieving higher strength. The high fineness and large specific surface area risk of MS also mitigate the plastic settlement and segregation problems. The use of MS in concrete production is rather established, and it is among the common constituent materials for making high-strength concrete [29, 30]. The use of MS as well as the combined use of MS and FA in producing SCC had been investigated and confirmed to be effective by the authors [31, 32].

Plasticising and superplasticising admixtures have taken an indispensable role in advancing the concrete technology and development of SCC. Before the 1960s, workability improving admixtures based on hydroxycarboxylic acids or lignosulphonates had been developed. They were usually known as plasticisers or water reducers, and they would allow the W/CM ratio to be reduced by 5–10% without adversely affecting the workability of concrete. In the 1960s–1970s, a newer generation of workability improving admixtures based on sulphonated formaldehyde condensates of melamine or naphthalene was developed. These admixtures are generally named superplasticisers (SP) or high-range water reducers because of their superior performance compared to their predecessors. Such SP could allow the W/CM ratio to be reduced by as much as 20–30% without affecting the workability [33]. Terminologically, SPs derived from sulphonated melamine formaldehyde condensates are sub-classified as melamine-based superplasticisers (abbreviated as SMF), while SPs derived from sulphonated naphthalene formaldehyde condensates are sub-classified as naphthalene-based superplasticisers (abbreviated as SNF). SMF and SNF have similar performance and may be blended together in usage [34]. In the 1980s, manufacturers started works to develop polycarboxylate-ether-based SP (abbreviated as PCE), but initially there were serious problems of severe retardation and excessive air entrainment [35]. It was only until around the turn of century, PCE became available in the market and these products were dubbed the third-generation superplasticisers or hyperplasticisers. The PCE remarkably outperformed the existing SP. Their use would allow the W/CM

prevent expansive alkali-silicate reaction [28].

**3. Use of superplasticising admixtures**

#### **4.1. Materials employed**

A total of 12 concrete mixes were produced for testing. The materials employed were as follows. The cement used was an ordinary Portland cement that complied with the requirements in European Standard EN 197. It has a solid density of 3.1 and a specific surface of 350 m<sup>2</sup> /kg. The fly ash (FA) used was produced from coal-fired power station and the properties complied with the requirements in European Standard EN 450. The shale ash (SA) used was produced from shale oil fuelled power plant and the properties have been investigated in this research. To show the morphology of SA particles, **Figure 1** depicts the scanning electron

**Figure 1.** Morphology of SA.

microscopy image of the SA. The microsilica (MS) used was produced from ferrosilicon plant and the properties complied with the requirements in European Standard EN 13263. **Table 1** lists the chemical compositions in percentage of the cement, FA, SA and MS. Regarding the physical properties, the cement, FA, SA and MS had specific surface areas of 595, 415, 570 and 20,000 m<sup>2</sup> /kg, and had specific gravities of 3150, 2110, 2800 and 2200 kg/m<sup>3</sup> .

The coarse aggregate was crushed granitic rock with a maximum size of 10 mm, while the fine aggregate used was crushed granitic rock fine with a maximum size of 5 mm. The properties and grading of the fine and coarse aggregates have been tested to comply with European Standard EN 12620. The SP used was polycarboxylate-ether-based complying with European Standard EN 934. It is a white-colour milky liquid that can be added into the mixing water or directly to the wet concrete. The recommended SP dosage by the manufacturer was typically 0.5–3.0% by mass of the cementitious materials content. Such polycarboxylate-ether-based SP is very effective and it allows adoption of low W/CM ratios.

#### **4.2. Experimental programme**

The experimental programme encompassed 12 SCC mixes. For all concrete mixes, the W/CM ratio by mass was ranging from 0.28 to 0.33, and the paste volume was ranging from 0.32 to 0.35. The fine to total aggregate (F/T) ratio was fixed at approximately 0.4 for the majority of concrete mixes, except for one of the mixes with W/CM ratio of 0.33 the F/T ratio was raised to 0.5. The contents of supplementary binder materials in mass percentage of the total binder were as follows: the FA content varied among 0 and 25%, the SA content varied among 0, 15, 30 and 45%, and the MS content varied among 0, 5 and 10%. One of the SCC mixes was cement concrete and did not contain any supplementary binder materials, six mixes featured binary blending of FA or SA, and five mixes featured ternary blending of FA and MS. **Table 2** summarises the mix parameters of the experimental programme. The SP dosage of the majority of mixes was 3.0%, except the dosage was lowered to 1.5% by mass for the mixes with SA due to the higher inherent workability of those mixes. It should be noted that the dosage was adjusted based on the surface area of the solid particles present in the concrete and the actual achieved workability compared to the target workability. The mix proportions are listed in **Table 3**.

**4.3. Embodied energy and carbon**

**Table 2.** Concrete mix parameters.

expressed in terms of kgCO<sup>2</sup>

To study the embodied energy (EE) and carbon emission of the SCC mixes, the data in the literature: Embodied Carbon: The Inventory of Carbon and Energy [42] were referred to. **Table 4** lists the embodied energy (*EE*) and embodied carbon (*EC*) of the constituent materials. Here, the embodied energy is expressed in terms of MJ/kg of material, and the embodied carbon is

**Minerals Cement Fly ash (FA) Shale ash (SA) Microsilica (MS)**

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SiO<sup>2</sup> 18.8 48.8 24.8 92.1

O<sup>3</sup> 3.9 25.2 5.9 1.2 CaO 62.1 2.4 50.5 1.1

O<sup>3</sup> 2.8 5.3 4.6 1.2 MgO 2.6 2.4 6.5 0.8

O 0.2 0.9 0.1 1.1

O 1.1 3.6 2.1 0.7 SO<sup>3</sup> 0.8 0.5 4.4 1.3

**Table 1.** Chemical compositions (in %) of cement and supplementary binder materials.

Note: The FA, SA and MS contents are expressed in percentage by mass of total binder.

**Mix no. W/CM ratio Paste volume F/T ratio FA content (%) SA content (%) MS content (%)**

 0.30 0.32 0.39 0 0 0 0.26 0.35 0.40 25 0 0 0.28 0.35 0.40 25 0 0 0.30 0.35 0.40 25 0 0 0.32 0.34 0.39 0 15 0 0.32 0.34 0.39 0 30 0 0.32 0.34 0.39 0 45 0 0.28 0.35 0.40 25 0 5 0.28 0.35 0.40 25 0 10 0.30 0.35 0.40 25 0 5 0.30 0.35 0.40 25 0 10 0.33 0.35 0.50 25 0 5

Al<sup>2</sup>

Fe<sup>2</sup>

Na<sup>2</sup>

K2

are generally one to two orders higher than those of FA, SA and MS, which originate from industrial by-products. Therefore, blending with supplementary binder materials to reduce the cement consumption is an effective means to enhance the sustainability of concrete.

/kg of material. It can be seen that the tabulated values for cement

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**Table 1.** Chemical compositions (in %) of cement and supplementary binder materials.


Note: The FA, SA and MS contents are expressed in percentage by mass of total binder.

**Table 2.** Concrete mix parameters.

microscopy image of the SA. The microsilica (MS) used was produced from ferrosilicon plant and the properties complied with the requirements in European Standard EN 13263. **Table 1** lists the chemical compositions in percentage of the cement, FA, SA and MS. Regarding the physical properties, the cement, FA, SA and MS had specific surface areas of 595, 415, 570 and

The coarse aggregate was crushed granitic rock with a maximum size of 10 mm, while the fine aggregate used was crushed granitic rock fine with a maximum size of 5 mm. The properties and grading of the fine and coarse aggregates have been tested to comply with European Standard EN 12620. The SP used was polycarboxylate-ether-based complying with European Standard EN 934. It is a white-colour milky liquid that can be added into the mixing water or directly to the wet concrete. The recommended SP dosage by the manufacturer was typically 0.5–3.0% by mass of the cementitious materials content. Such polycarboxylate-ether-based SP

The experimental programme encompassed 12 SCC mixes. For all concrete mixes, the W/CM ratio by mass was ranging from 0.28 to 0.33, and the paste volume was ranging from 0.32 to 0.35. The fine to total aggregate (F/T) ratio was fixed at approximately 0.4 for the majority of concrete mixes, except for one of the mixes with W/CM ratio of 0.33 the F/T ratio was raised to 0.5. The contents of supplementary binder materials in mass percentage of the total binder were as follows: the FA content varied among 0 and 25%, the SA content varied among 0, 15, 30 and 45%, and the MS content varied among 0, 5 and 10%. One of the SCC mixes was cement concrete and did not contain any supplementary binder materials, six mixes featured binary blending of FA or SA, and five mixes featured ternary blending of FA and MS. **Table 2** summarises the mix parameters of the experimental programme. The SP dosage of the majority of mixes was 3.0%, except the dosage was lowered to 1.5% by mass for the mixes with SA due to the higher inherent workability of those mixes. It should be noted that the dosage was adjusted based on the surface area of the solid particles present in the concrete and the actual achieved workability compared to the target workability. The mix proportions are listed in **Table 3**.

.

/kg, and had specific gravities of 3150, 2110, 2800 and 2200 kg/m<sup>3</sup>

118 Sustainable Buildings - Interaction Between a Holistic Conceptual Act and Materials Properties

is very effective and it allows adoption of low W/CM ratios.

**4.2. Experimental programme**

20,000 m<sup>2</sup>

**Figure 1.** Morphology of SA.

#### **4.3. Embodied energy and carbon**

To study the embodied energy (EE) and carbon emission of the SCC mixes, the data in the literature: Embodied Carbon: The Inventory of Carbon and Energy [42] were referred to. **Table 4** lists the embodied energy (*EE*) and embodied carbon (*EC*) of the constituent materials. Here, the embodied energy is expressed in terms of MJ/kg of material, and the embodied carbon is expressed in terms of kgCO<sup>2</sup> /kg of material. It can be seen that the tabulated values for cement are generally one to two orders higher than those of FA, SA and MS, which originate from industrial by-products. Therefore, blending with supplementary binder materials to reduce the cement consumption is an effective means to enhance the sustainability of concrete.


by the slump and flow tests as stipulated in European Standard EN 12350: Part 2 and Part 8. The same equipment was used for the slump and flow tests. The slump cone had a base diameter of 200 mm, a top diameter of 100 mm and a height of 300 mm. A smooth steel plate of size 1× 1 m was placed on level ground for carrying out the test. The size of steel plate was sufficiently large to cater for the extent of flow of concrete. Concrete was first filled into the slump cone without tamping. When the slump cone was full, the top surface of concrete was trowelled flat and the slump cone was lifted steadily to allow the concrete to flow under its own weight to form a patty. After the flow had ceased, the slump of concrete was measured as the difference between the height of slump cone and the highest point of the patty. Besides, the slump flow (or flow in short) of concrete was measured as the average diameter of the patty in two orthogonal directions. The slump and flow values were measured and reported to the nearest 5 mm. In addition, any sign of segregation instability was observed by visual

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The compressive strength of the SCC mixes was measured in accordance with European Standard EN 12390: Part 3 and Part 4. Cubes of size 100 mm were cast from the fresh SCC mixes and then covered to protect against loss of moisture by evaporation. One day after casting, the cubes were demoulded and were cured by immersing in lime-saturated water curing tank at a temperature of 27 ± 2°C. Until the required age of testing at 7 days or 28 days, the cubes were taken out from the curing tank, wiped dry and underwent the compressive strength test. The mean compressive strength was obtained by averaging the test results of a set of three cubes. If there was any individual cube strength deviating from the average cube strength by more than 10%, the individual result would be discarded and the average cube strength would be taken as the average of the remaining two cubes. All strength results pre-

The experimental results of workability and strength of the SCC mixes are presented in **Table 5**. It is noted that the slump values fell in the range from 220 to 260 mm, and the flow values were within the range from 620 to 775 mm. No sign of segregation instability was observed for all the SCC mixes. Basically, all the concrete mixes achieved the required workability and flowability of being self-consolidating. Such workability and flowability regime also offers potential applications for tremie concrete mixes and pumped mixes. According to the relevant European guidelines [7], SCC are classified into three flow classes, namely class SF1 for flow value between 550 and 650 mm, class SF2 for flow value between 660 and 750 mm and class SF3 for flow value between 760 and 850 mm. The flow classification of each SCC mix is indicated in **Table 5**. It is worthwhile to note that for the SA concrete (Mixes 5, 6 and 7), the workability and flowability at the presence of SA were favourable such that the SP dosage was set at a low level (circa 1.5% by mass of the cementitious materials content). Therefore, the use of SA can economise the material cost

inspection particularly around the rim of the slumped patty.

sented in this chapter are the mean compressive strength so evaluated.

**5. Results and discussions**

**5.1. Workability and flowability**

of SCC by consuming less amount of SP.

**Table 3.** Concrete mix proportions.

Based on the listed values in **Table 4**, the embodied energy and embodied carbon of the SCC mixes may be computed as follows, where *EE* is in MJ/m<sup>3</sup> , *EC* is in kgCO<sup>2</sup> /m<sup>3</sup> and *W*, *C*, *FA*, *SA*, *MS* and *A* are the contents of water, cement, FA, SA, MS and aggregate, respectively, in kg/m<sup>3</sup> .

$$EE = 0.010\,\text{W} + 4.500\,\text{C} + 0.100FA + 0.030SA + 0.850MS + 0.083A \tag{1}$$

$$EC = 0.001\,\mathrm{W} + 0.730\,\mathrm{C} + 0.008FA + 0.002\,\mathrm{SA} + 0.020\,\mathrm{MS} + 0.005\,\mathrm{A} \tag{2}$$

#### **4.4. Test procedures**

Laboratory pan-type mixer was employed to mix the concrete, with a total duration of mixing of not less than 5 minutes for each mix. The workability of the fresh SCC mixes was measured


**Table 4.** Embodied energy and embodied carbon of constituent materials.

by the slump and flow tests as stipulated in European Standard EN 12350: Part 2 and Part 8. The same equipment was used for the slump and flow tests. The slump cone had a base diameter of 200 mm, a top diameter of 100 mm and a height of 300 mm. A smooth steel plate of size 1× 1 m was placed on level ground for carrying out the test. The size of steel plate was sufficiently large to cater for the extent of flow of concrete. Concrete was first filled into the slump cone without tamping. When the slump cone was full, the top surface of concrete was trowelled flat and the slump cone was lifted steadily to allow the concrete to flow under its own weight to form a patty. After the flow had ceased, the slump of concrete was measured as the difference between the height of slump cone and the highest point of the patty. Besides, the slump flow (or flow in short) of concrete was measured as the average diameter of the patty in two orthogonal directions. The slump and flow values were measured and reported to the nearest 5 mm. In addition, any sign of segregation instability was observed by visual inspection particularly around the rim of the slumped patty.

The compressive strength of the SCC mixes was measured in accordance with European Standard EN 12390: Part 3 and Part 4. Cubes of size 100 mm were cast from the fresh SCC mixes and then covered to protect against loss of moisture by evaporation. One day after casting, the cubes were demoulded and were cured by immersing in lime-saturated water curing tank at a temperature of 27 ± 2°C. Until the required age of testing at 7 days or 28 days, the cubes were taken out from the curing tank, wiped dry and underwent the compressive strength test. The mean compressive strength was obtained by averaging the test results of a set of three cubes. If there was any individual cube strength deviating from the average cube strength by more than 10%, the individual result would be discarded and the average cube strength would be taken as the average of the remaining two cubes. All strength results presented in this chapter are the mean compressive strength so evaluated.
