*3.4. Pore Structure*

conditions.

The differential pore size distributions of different hardened pastes under standard curing conditions are presented in Figure 6. As shown in Figure 6, the most likely pore sizes of samples SC, SS25 and SS45 at 28 d were 62.1 nm, 30.2 nm and 13.94 nm, respectively. With further hydration, the pore structure of the hardened paste becomes dense. The most likely pore sizes of samples SC, SS25 and SS45 at 28 d were 40.7 nm, 5.42 nm and 3.39 nm, respectively. The most likely pore size obviously decreased with GSP due to its positive effects on pore structure. Pores in hardened paste can be divided into four types, depending on their diameters and functions, according to Mehta's opinion: >100 nm, 50–100 nm, 4.5–50 nm and <4.5 nm [45,46]. Pores larger than 100 nm (also called harmful pores) have adverse effects on the development of mechanical strength and the permeability of hardened matrices [36]. Thus, the detailed pore size distribution of the hardened paste is presented in Figure 7. Figure 7a shows that the porosities of samples SC, SS25 and SS45 at 28 d were 21.52%, 20.81% and 17.29%, respectively. The porosities at 90 d, shown in Figure 7b, were 16.77%, 16.79% and 19.09%, respectively. Compared to the plain cement paste (sample SC), the total porosity and the volume of harmful pores in hardened paste at 28 d were significantly reduced due to the addition of GSP. However, the total porosity in hardened paste containing 45% GSP (sample SS45) was the largest at 28 d due to more harmless pores (<4.5 nm).

90 d.

The differential pore size distributions of different hardened pastes under standard curing conditions are presented in Figure 6. As shown in Figure 6, the most likely pore sizes of samples SC, SS25 and SS45 at 28 d were 62.1 nm, 30.2 nm and 13.94 nm, respectively. With further hydration, the pore structure of the hardened paste becomes dense. The most likely pore sizes of samples SC, SS25 and SS45 at 28 d were 40.7 nm, 5.42 nm and 3.39 nm, respectively. The most likely pore size obviously decreased with GSP due to its positive effects on pore structure. Pores in hardened paste can be divided into four types, depending on their diameters and functions, according to Mehta's opinion: >100 nm, 50– 100 nm, 4.5–50 nm and <4.5 nm [45,46]. Pores larger than 100 nm (also called harmful pores) have adverse effects on the development of mechanical strength and the permeability of hardened matrices [36]. Thus, the detailed pore size distribution of the hardened paste is presented in Figure 7. Figure 7a shows that the porosities of samples SC, SS25 and SS45 at 28 d were 21.52%, 20.81% and 17.29%, respectively. The porosities at 90 d, shown in Figure 7b, were 16.77%, 16.79% and 19.09%, respectively. Compared to the plain cement paste (sample SC), the total porosity and the volume of harmful pores in hardened paste at 28 d were significantly reduced due to the addition of GSP. However, the total porosity in hardened paste containing 45% GSP (sample SS45) was the largest at 28 d due to more

*3.4. Pore Structure* 

harmless pores (<4.5 nm).

**Figure 6.** Differential pore volume of hardened pastes under standard curing conditions: (**a**) at 28 d; (**b**) at 90 d. **Figure 6.** Differential pore volume of hardened pastes under standard curing conditions: (**a**) at 28 d; (**b**) at 90 d.

**Figure 7.** The pore size distribution of hardened pastes under standard curing conditions: (**a**) at 28 d; (**b**) at 90 d. **Figure 7.** The pore size distribution of hardened pastes under standard curing conditions: (**a**) at 28 d; (**b**) at 90 d.

The differential pore size distributions of different hardened pastes under temperature-matching curing conditions are presented in Figure 8. The most likely pore sizes of samples MC, MS25 and MS45 at 28 d were 24.3 nm, 49.0 nm and 5.4 nm, respectively. With further hydration, the pore structure of the hardened paste becomes denser. The most likely pore sizes of samples MC, MS25 and MS45 at 90 d were 17.1 nm, 5.7 nm and 5.0 nm, respectively. The detailed pore size distribution of the hardened paste is presented in Figure 9. Figure 9a shows that the porosities of samples MC, MS25 and MS45 at 28 d were 24.74%, 17.09% and 16.23%, respectively. The porosities at 90 d, shown in Figure 9b, were 22.20%, 16.35% and 11.31%, respectively. Compared to the plain cement paste (sample MC), the total porosity and the volume of harmful pores in hardened paste containing 25% GSP were significantly reduced. Sample MS25 had lower total porosity than sample MC. However, the volumes of harmful pores of both pastes showed little difference. The differential pore size distributions of different hardened pastes under temperaturematching curing conditions are presented in Figure 8. The most likely pore sizes of samples MC, MS25 and MS45 at 28 d were 24.3 nm, 49.0 nm and 5.4 nm, respectively. With further hydration, the pore structure of the hardened paste becomes denser. The most likely pore sizes of samples MC, MS25 and MS45 at 90 d were 17.1 nm, 5.7 nm and 5.0 nm, respectively. The detailed pore size distribution of the hardened paste is presented in Figure 9. Figure 9a shows that the porosities of samples MC, MS25 and MS45 at 28 d were 24.74%, 17.09% and 16.23%, respectively. The porosities at 90 d, shown in Figure 9b, were 22.20%, 16.35% and 11.31%, respectively. Compared to the plain cement paste (sample MC), the total porosity and the volume of harmful pores in hardened paste containing 25% GSP were significantly reduced. Sample MS25 had lower total porosity than sample MC. However, the volumes of harmful pores of both pastes showed little difference.

(**a**) (**b**) **Figure 8.** Differential pore volume of hardened pastes under temperature-matching curing conditions: (**a**) at 28 d; (**b**) at 90 d.

90 d.

**Figure 7.** The pore size distribution of hardened pastes under standard curing conditions: (**a**) at 28 d; (**b**) at 90 d.

ever, the volumes of harmful pores of both pastes showed little difference.

The differential pore size distributions of different hardened pastes under temperature-matching curing conditions are presented in Figure 8. The most likely pore sizes of samples MC, MS25 and MS45 at 28 d were 24.3 nm, 49.0 nm and 5.4 nm, respectively. With further hydration, the pore structure of the hardened paste becomes denser. The most likely pore sizes of samples MC, MS25 and MS45 at 90 d were 17.1 nm, 5.7 nm and 5.0 nm, respectively. The detailed pore size distribution of the hardened paste is presented in Figure 9. Figure 9a shows that the porosities of samples MC, MS25 and MS45 at 28 d were 24.74%, 17.09% and 16.23%, respectively. The porosities at 90 d, shown in Figure 9b, were 22.20%, 16.35% and 11.31%, respectively. Compared to the plain cement paste (sample MC), the total porosity and the volume of harmful pores in hardened paste containing 25% GSP were significantly reduced. Sample MS25 had lower total porosity than sample MC. How-

**Figure 8.** Differential pore volume of hardened pastes under temperature-matching curing conditions: (**a**) at 28 d; (**b**) at **Figure 8.** Differential pore volume of hardened pastes under temperature-matching curing conditions: (**a**) at 28 d; (**b**) at 90 d.

**Figure 9.** The pore size distribution of hardened pastes under temperature-matching curing conditions: (**a**) at 28 d; (**b**) at **Figure 9.** The pore size distribution of hardened pastes under temperature-matching curing conditions: (**a**) at 28 d; (**b**) at 90 d.
