**5. Results and discussions**

Based on the listed values in **Table 4**, the embodied energy and embodied carbon of the SCC

**Cement FA SA MS Water SP**

*SA*, *MS* and *A* are the contents of water, cement, FA, SA, MS and aggregate, respectively, in

*EE* = 0.010 *W* + 4.500*C* + 0.100*FA* + 0.030*SA* + 0.850*MS* + 0.083*A* (1)

*EC* = 0.001 *W* + 0.730*C* + 0.008*FA* + 0.002*SA* + 0.020*MS* + 0.005*A* (2)

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

**Material Embodied energy (MJ/kg) Embodied carbon (kgCO2**

Water 0.010 0.001 Cement 4.500 0.730 FA 0.100 0.008 SA 0.030 0.002 MS 0.850 0.020 Rock aggregate 0.083 0.005

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

, *EC* is in kgCO<sup>2</sup>

/m<sup>3</sup>

**/kg)**

and *W*, *C*, *FA*,

mixes may be computed as follows, where *EE* is in MJ/m<sup>3</sup>

**Mix no. Mass content (kg/m3**

**)**

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

 492 0 0 0 150 7.4 421 140 0 0 146 17.7 408 136 0 0 152 17.1 395 132 0 0 158 16.6 452 0 80 0 152 7.2 380 0 163 0 146 5.7 320 0 262 0 150 6.3 376 134 0 27 150 16.9 345 133 0 53 149 16.5 365 130 0 26 156 16.4 335 129 0 52 155 16.2 342 117 0 23 161 14.7

kg/m<sup>3</sup> .

**4.4. Test procedures**

**Table 3.** Concrete mix proportions.

#### **5.1. Workability and flowability**

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 of SCC by consuming less amount of SP.


**Table 5.** Workability and strength results.

To reveal the relation between slump and flow, the variation of these two quantities is plotted in **Figure 2**. For ease of visualisation, the data points are divided into four groups, namely "Cement SCC" for Mix 1, "FA SCC" for Mixes 2–4, "SA SCC" for Mixes 5–7, and "FA + MS" SCC for Mixes 8–12. Besides, horizontal lines at flow levels of 550, 650 and 750 mm corresponding to the boundary values of flow classes are drawn. It can be seen from **Figure 2** that the slump and flow are positively correlated. Nevertheless, at a workability level of higher than 200 mm slump, the slump is less sensitive to the change in workability as compared to the flow. Hence, the flow value serves as a better measurement of the self-consolidating ability.

unity, the line of gradient of 1.2 and the trend line of data points are drawn for ease of visualisation. For each SCC mix, the ratio of 28-day strength to 7-day strength is computed and is listed in the last column of **Table 5**. The ratio ranged from 1.11 for Mix 7 with 45% SA content to 1.43 for Mix 11 with

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It is evident from the strength results that the SCC mixes produced in the current experimental programme are suitable for adoption as high-strength SCC, or HS-SCC mixes. From the authors' experience in concrete production and testing, rational grade designation for Mixes 1–12 is assigned with reasonable allowance of standard deviations in strength results to account for the difference between the mean strength and the characteristic strength (grade strength). The grade designation based on concrete cube strength is listed in the second column of **Table 6**, where Mixes 1, 4 and 7 are designated as C70, Mix 5 is designated as C75, Mixes 6 and 12 are designated as C80, Mixes 2, 3, 8 and 10 are designated as C85, and Mixes 9 and 11 are designated as C90. These concrete grades are significantly higher than the grades of common SCC mixes employed in construction projects. It should be noted that the standard deviation of strength results can be established with a higher confidence level upon the availability of data from a larger sample population. Therefore, the grade designation herein

The sustainability performance of the SCC mixes, evaluated through the *EE* and *EC* as per Eq.

binder materials gave rise to the highest *EE* and *EC* values. By blending with FA, SA and MS,

, whereas the

. The cement SCC Mix 1 without supplementary

(1) and Eq. (2), is shown in **Table 6**. The *EE* was ranging from 1590 to 2359 MJ/m<sup>3</sup>

/m<sup>3</sup>

would subject to alteration after further trial mixing and production.

25% FA content and 10% MS content.

**Figure 2.** Plot of flow versus slump.

**5.3. Sustainability performance**

*EC* was ranging from 243 to 368 kgCO<sup>2</sup>

#### **5.2. Compressive strength**

The 7-day and 28-day mean cube compressive strength results are listed in **Table 5**. It can be seen that all 7-day strength results were higher than 60 MPa, and all 28-day strength results were higher than 80 MPa. Therefore, the SCC mixes do satisfy the requirement of high strength. The 7-day strength was ranging from 63.3 to 81.4 MPa. Mix 4 with W/CM ratio of 0.3 and with 25% FA content had the lowest 7-day strength, due to the relative slow strength development of FA concrete as expected. The 28-day strength was ranging from 80.2 to 108.5 MPa. Mix 1 without supplementary binder materials had the lowest 28-day strength, which demonstrated the more effective strength development at a later age of blended SCC mixes. Mix 9 with W/CM ratio of 0.28 and with 25% FA content and 10% MS content had the highest 7-day and 28-day strengths, which proved the beneficial effect of MS on strength enhancement. In particular, the use of SA up to even a high volume allowed the achievement of very high strength. At 30% SA content, the 28-day strength of Mix 6 was 91.8 MPa; where at 45% SA content, the 28-day strength of Mix 7 was 83.4 MPa. The 7-day compressive strength is plotted versus the 28-day compressive strength in **Figure 3**. In the figure, the line of Development of Sustainable High-Strength Self-Consolidating Concrete Utilising Fly Ash, Shale… http://dx.doi.org/10.5772/intechopen.75508 123

**Figure 2.** Plot of flow versus slump.

**Mix no.**

**Slump (mm)**

**Flow (mm)**

**Table 5.** Workability and strength results.

self-consolidating ability.

**5.2. Compressive strength**

**Flow class**

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

**7-day mean cube strength (MPa)**

To reveal the relation between slump and flow, the variation of these two quantities is plotted in **Figure 2**. For ease of visualisation, the data points are divided into four groups, namely "Cement SCC" for Mix 1, "FA SCC" for Mixes 2–4, "SA SCC" for Mixes 5–7, and "FA + MS" SCC for Mixes 8–12. Besides, horizontal lines at flow levels of 550, 650 and 750 mm corresponding to the boundary values of flow classes are drawn. It can be seen from **Figure 2** that the slump and flow are positively correlated. Nevertheless, at a workability level of higher than 200 mm slump, the slump is less sensitive to the change in workability as compared to the flow. Hence, the flow value serves as a better measurement of the

The 7-day and 28-day mean cube compressive strength results are listed in **Table 5**. It can be seen that all 7-day strength results were higher than 60 MPa, and all 28-day strength results were higher than 80 MPa. Therefore, the SCC mixes do satisfy the requirement of high strength. The 7-day strength was ranging from 63.3 to 81.4 MPa. Mix 4 with W/CM ratio of 0.3 and with 25% FA content had the lowest 7-day strength, due to the relative slow strength development of FA concrete as expected. The 28-day strength was ranging from 80.2 to 108.5 MPa. Mix 1 without supplementary binder materials had the lowest 28-day strength, which demonstrated the more effective strength development at a later age of blended SCC mixes. Mix 9 with W/CM ratio of 0.28 and with 25% FA content and 10% MS content had the highest 7-day and 28-day strengths, which proved the beneficial effect of MS on strength enhancement. In particular, the use of SA up to even a high volume allowed the achievement of very high strength. At 30% SA content, the 28-day strength of Mix 6 was 91.8 MPa; where at 45% SA content, the 28-day strength of Mix 7 was 83.4 MPa. The 7-day compressive strength is plotted versus the 28-day compressive strength in **Figure 3**. In the figure, the line of

 230 660 SF2 67.4 80.2 1.19 220 620 SF1 78.2 98.0 1.25 235 665 SF2 74.6 96.1 1.29 225 670 SF2 63.3 81.6 1.29 250 700 SF2 72.7 86.7 1.19 225 650 SF1 73.7 91.8 1.25 255 730 SF2 75.2 83.4 1.11 250 660 SF2 74.6 101.4 1.36 225 620 SF1 81.4 108.5 1.33 235 660 SF2 77.1 102.7 1.33 225 620 SF1 73.1 104.8 1.43 260 775 SF3 72.5 89.8 1.24

**28-day mean cube strength (MPa)**

**28-day to 7-day strength ratio**

> unity, the line of gradient of 1.2 and the trend line of data points are drawn for ease of visualisation. For each SCC mix, the ratio of 28-day strength to 7-day strength is computed and is listed in the last column of **Table 5**. The ratio ranged from 1.11 for Mix 7 with 45% SA content to 1.43 for Mix 11 with 25% FA content and 10% MS content.

> It is evident from the strength results that the SCC mixes produced in the current experimental programme are suitable for adoption as high-strength SCC, or HS-SCC mixes. From the authors' experience in concrete production and testing, rational grade designation for Mixes 1–12 is assigned with reasonable allowance of standard deviations in strength results to account for the difference between the mean strength and the characteristic strength (grade strength). The grade designation based on concrete cube strength is listed in the second column of **Table 6**, where Mixes 1, 4 and 7 are designated as C70, Mix 5 is designated as C75, Mixes 6 and 12 are designated as C80, Mixes 2, 3, 8 and 10 are designated as C85, and Mixes 9 and 11 are designated as C90. These concrete grades are significantly higher than the grades of common SCC mixes employed in construction projects. It should be noted that the standard deviation of strength results can be established with a higher confidence level upon the availability of data from a larger sample population. Therefore, the grade designation herein would subject to alteration after further trial mixing and production.

#### **5.3. Sustainability performance**

The sustainability performance of the SCC mixes, evaluated through the *EE* and *EC* as per Eq. (1) and Eq. (2), is shown in **Table 6**. The *EE* was ranging from 1590 to 2359 MJ/m<sup>3</sup> , whereas the *EC* was ranging from 243 to 368 kgCO<sup>2</sup> /m<sup>3</sup> . The cement SCC Mix 1 without supplementary binder materials gave rise to the highest *EE* and *EC* values. By blending with FA, SA and MS,

**Figure 3.** Plot of 28-day strength versus 7-day strength.

the *EE* and *EC* could be remarkably reduced, with the percentage decrease for each mix relative to Mix 1 listed in brackets in columns 3 and 4 of **Table 6** after the respective *EE* and *EC* values. As noted in the above, SA can be used at a high volume while capable of achieving high strength, consequently, the largest decrease in *EE* and *EC* was attained by Mix 7, which had the highest SA content of 45% by mass of binder. The corresponding reduction in *EE* and *EC* was as large as 32.6 and 34.0%, respectively. The variation of *EE* with the 28-day strength

and the variation of *EC* with the 28-day strength are plotted in **Figures 4** and **5**, respectively. In these figures, moving vertically downwards and towards the right-hand side would indicate a more sustainable and higher strength concrete. It can be observed that Mix 1 performed the worst among all mixes in terms of both strength and sustainability, while the ternary blended (cement + FA + MS) mixes generally performed superior, as reflected by the group of data points close to the bottom right corner in the figures. The good overall performance is due to the effectiveness of FA in lowering the *EE* and *EC*, as well as the effectiveness of MS in improv-

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For comparison on an equal-strength basis, the *EE* per strength and the *EC* per strength at age of 28-days are evaluated and listed in the last two columns of **Table 6**. It is seen that the *EE* per

*EC* per strength relative to Mix 1 is listed in brackets in the last two columns of **Table 6**. This can reflect the concurrent improvement in strength and sustainability by blending with FA, SA and MS. The largest percentage reductions in *EE* and *EC* per strength were attained by Mixes 9 and 11, which contained 25% FA content and 10% MS content. To facilitate visualising the concurrent effects on strength and sustainability, family of straight lines of constant *EE*/ strength ratio at equal intervals and family of straight lines of constant *EC*/strength ratio at

To investigate the rationalisation of SP dosage, one of the SCC mixes, additional trial of Mix 2 was carried out with varied SP dosage while maintaining the proportions of other mix ingredients

)/MPa, whereas the *EC* per strength was ranging

)/MPa. Similar to the foregoing, the percentage decrease in *EE* and

ing the strength.

from 2.4 to 4.6 (kgCO<sup>2</sup>

strength was ranging from 16.1 to 29.4 (MJ/m<sup>3</sup>

/m<sup>3</sup>

**Figure 4.** Plot of embodied energy versus 28-day compressive strength.

equal intervals are plotted in **Figures 4** and **5**, respectively.

**5.4. Additional investigation of rational SP dosage**


**Table 6.** Sustainability performance results.

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**Figure 4.** Plot of embodied energy versus 28-day compressive strength.

the *EE* and *EC* could be remarkably reduced, with the percentage decrease for each mix relative to Mix 1 listed in brackets in columns 3 and 4 of **Table 6** after the respective *EE* and *EC* values. As noted in the above, SA can be used at a high volume while capable of achieving high strength, consequently, the largest decrease in *EE* and *EC* was attained by Mix 7, which had the highest SA content of 45% by mass of binder. The corresponding reduction in *EE* and *EC* was as large as 32.6 and 34.0%, respectively. The variation of *EE* with the 28-day strength

**Embodied carbon** 

*EE* **per strength (MJ/**

*EC* **per strength (kgCO2**

**m3 /MPa)** **/**

**m3 /MPa)**

**(kgCO2 /m3 )**

 C70 2359 (±0%) 368 (±0%) 29.4 (±0%) 4.6 (±0%) C85 2050 (−13.1%) 317 (−13.9%) 20.9 (−28.9%) 3.2 (−30.4%) C85 1991 (−15.6%) 308 (−16.3%) 20.7 (−29.6%) 3.2 (−30.4%) C70 1932 (−18.1%) 298 (−19.0%) 23.7 (−19.4%) 3.7 (−19.6%) C75 2182 (−7.5%) 339 (−7.9%) 25.2 (−14.3%) 3.9 (−15.2%) C80 1855 (−21.4%) 286 (−22.3%) 20.2 (−31.3%) 3.1 (−32.6%) C70 1590 (−32.6%) 243 (−34.0%) 19.1 (−35.0%) 2.9 (−37.0%) C85 1870 (−20.7%) 285 (−22.6%) 18.4 (−37.4%) 2.8 (−39.1%) C90 1752 (−25.7%) 263 (−28.5%) 16.1 (−45.2%) 2.4 (−47.8%) C85 1819 (−22.9%) 277 (−24.7%) 17.7 (−39.8%) 2.7 (−41.3%) C90 1706 (−27.7%) 255 (−30.7%) 16.3 (−44.6%) 2.4 (−47.8%) C80 1712 (−27.4%) 260 (−29.3%) 19.1 (−35.0%) 2.9 (−37.0%)

**Mix no.**

**Grade designation** **Embodied energy (MJ/m3**

**Figure 3.** Plot of 28-day strength versus 7-day strength.

**Table 6.** Sustainability performance results.

**)**

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

and the variation of *EC* with the 28-day strength are plotted in **Figures 4** and **5**, respectively. In these figures, moving vertically downwards and towards the right-hand side would indicate a more sustainable and higher strength concrete. It can be observed that Mix 1 performed the worst among all mixes in terms of both strength and sustainability, while the ternary blended (cement + FA + MS) mixes generally performed superior, as reflected by the group of data points close to the bottom right corner in the figures. The good overall performance is due to the effectiveness of FA in lowering the *EE* and *EC*, as well as the effectiveness of MS in improving the strength.

For comparison on an equal-strength basis, the *EE* per strength and the *EC* per strength at age of 28-days are evaluated and listed in the last two columns of **Table 6**. It is seen that the *EE* per strength was ranging from 16.1 to 29.4 (MJ/m<sup>3</sup> )/MPa, whereas the *EC* per strength was ranging from 2.4 to 4.6 (kgCO<sup>2</sup> /m<sup>3</sup> )/MPa. Similar to the foregoing, the percentage decrease in *EE* and *EC* per strength relative to Mix 1 is listed in brackets in the last two columns of **Table 6**. This can reflect the concurrent improvement in strength and sustainability by blending with FA, SA and MS. The largest percentage reductions in *EE* and *EC* per strength were attained by Mixes 9 and 11, which contained 25% FA content and 10% MS content. To facilitate visualising the concurrent effects on strength and sustainability, family of straight lines of constant *EE*/ strength ratio at equal intervals and family of straight lines of constant *EC*/strength ratio at equal intervals are plotted in **Figures 4** and **5**, respectively.

#### **5.4. Additional investigation of rational SP dosage**

To investigate the rationalisation of SP dosage, one of the SCC mixes, additional trial of Mix 2 was carried out with varied SP dosage while maintaining the proportions of other mix ingredients

by adopting low W/CM ratios through the use of polycarboxylate-ether-based superplasticiser (SP). A series of 12 SCC mixes incorporating FA, SA and MS have been produced for laboratory testing. From the experimental results, all the concrete mixes have attained the required workability and flowability of self-consolidating. The flow values have satisfied the respective ranges of slump-flow classes SF1, SF2 or SF3 according to the European guidelines for SCC, and there has been no problem of segregation instability as revealed from visual observations. The mean 28-day compressive cube strengths of the SCC mixes were within the range from 80.2 to 108.5 MPa, which could be designated as grade C70 to C90. Depending on the contents of respective supplementary binder materials, the use of FA, SA and MS has significantly lowered the embodied energy (EE) and embodied carbon (EC) of the SCC mixes by up to 32.6% and 34.0%, respectively. In particular, SA can be used at a high volume while capable of achieving high strength, thereby enabling great enhancement in sustainability performance. For comparison on an equal-strength basis, the EE per strength and the EC per strength at 28-day age have been evaluated. By so doing, the concurrent improvement in strength and sustainability by blending with FA, SA and MS has been clearly demonstrated, where reductions in EE per strength and EC per strength by up to more than 45% have been achieved. Overall speaking, the results have concluded successful development of sustainable HS-SCC with superior performance compared to the conventional SCC mixes. The mix design contained in this chapter may be adopted as reference HS-SCC mixes for practical use. Moreover, from additional studies, the authors have suggested rationalising the SP dosage based on the specific surface area of cementitious materials, instead of the conventional

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practice of dosing the SP based on the mass content of cementitious materials.

The financial support from the Marie Skłodowska-Curie Actions of the European Commission

, Ivan Yu-Ting Ng2

3 Faculty of Civil Engineering and Architecture, Kaunas University of Technology, Lithuania

1 Faculty of Civil Engineering, Vilnius Gediminas Technical University, Lithuania

2 Department of Civil Engineering, The University of Hong Kong, Hong Kong, China

and Albert Kwok-Hung Kwan<sup>2</sup>

**Acknowledgements**

**Conflict of interest**

**Author details**

Pui-Lam Ng1,2\*, Žymantas Rudžionis<sup>3</sup>

(Project no. 751461) is gratefully acknowledged.

The authors declare that there is no conflict of interest.

\*Address all correspondence to: irdngpl@gmail.com

**Figure 5.** Plot of embodied carbon versus 28-day compressive strength.

unchanged. From the specific surface areas reported in Section 4.1, the SP dosage of Mix 2 in terms of liquid mass per surface area of cementitious materials was evaluated to be 57 × 10−6 kg/m<sup>2</sup> . Two trial mixes, labelled as Mix 2a and Mix 2b, were conducted with the respective SP dosage set at 76 × 10−6 kg/m<sup>2</sup> and 96 × 10−6 kg/m<sup>2</sup> area of cementitious materials (approximately correspond to 4% and 5% by mass of cementitious materials, respectively). The slump and flow results of Mix 2a were 255 and 725 mm, respectively, while the slump and flow results of Mix 2b were 240 and 770 mm, respectively. No sign of segregation was observed. It should be noted that when determining the SP dosage of SCC mixes containing materials of high fineness such as MS, the SP dosage should better be set based on the specific surface area of cementitious materials, so as to more effectively utilised the SP. In any case, the above additional investigation indicated possibility of further increasing the flowability at constant W/CM ratio, or conversely, possibility of further reducing the W/CM ratio for achieving even higher strength while maintaining the flowability. Therefore, it should be viable to develop HS-SCC beyond grade C90 by rationalising the SP usage and further mix optimisation, and research along this direction is recommended.

#### **6. Conclusions**

With the aim to develop sustainable high-strength self-consolidating concrete (HS-SCC) mixes, the authors have conducted research on improving the sustainable performance and mechanical strength of self-consolidating concrete (SCC) mixes. Reduction in embodied energy and carbon emission of SCC mixes has been achieved by reducing the cement consumption with the incorporation of fly ash (FA), shale ash (SA) and microsilica (MS) as supplementary binder materials. High compressive strength of SCC mixes has been achieved by adopting low W/CM ratios through the use of polycarboxylate-ether-based superplasticiser (SP). A series of 12 SCC mixes incorporating FA, SA and MS have been produced for laboratory testing. From the experimental results, all the concrete mixes have attained the required workability and flowability of self-consolidating. The flow values have satisfied the respective ranges of slump-flow classes SF1, SF2 or SF3 according to the European guidelines for SCC, and there has been no problem of segregation instability as revealed from visual observations. The mean 28-day compressive cube strengths of the SCC mixes were within the range from 80.2 to 108.5 MPa, which could be designated as grade C70 to C90. Depending on the contents of respective supplementary binder materials, the use of FA, SA and MS has significantly lowered the embodied energy (EE) and embodied carbon (EC) of the SCC mixes by up to 32.6% and 34.0%, respectively. In particular, SA can be used at a high volume while capable of achieving high strength, thereby enabling great enhancement in sustainability performance. For comparison on an equal-strength basis, the EE per strength and the EC per strength at 28-day age have been evaluated. By so doing, the concurrent improvement in strength and sustainability by blending with FA, SA and MS has been clearly demonstrated, where reductions in EE per strength and EC per strength by up to more than 45% have been achieved. Overall speaking, the results have concluded successful development of sustainable HS-SCC with superior performance compared to the conventional SCC mixes. The mix design contained in this chapter may be adopted as reference HS-SCC mixes for practical use. Moreover, from additional studies, the authors have suggested rationalising the SP dosage based on the specific surface area of cementitious materials, instead of the conventional practice of dosing the SP based on the mass content of cementitious materials.
