Figures (12)  Tables (7)

    • Figure 1. 

      Particle size distribution of BC300, BC500, BC700, and OPC.

    • Figure 2. 

      Results of FTIR of (a) modified original biochar, and (b) modified SP.

    • Figure 3. 

      Results of XRD of (a) modified original biochar, and (b) modified SP.

    • Figure 4. 

      Raman spectra characterization of different biochar samples.

    • Figure 5. 

      CO2 uptake by different biochar at room temperature.

    • Figure 6. 

      Adsorption kinetic curves of different biochar samples at room temperature.

    • Figure 7. 

      Effect of different biochar additions on the exothermic rate of hydration of cement composites.

    • Figure 8. 

      Compressive strength results of different biochar cement composites tested at (a) 7, and (b) 28 d.

    • Figure 9. 

      Results of biochar-cement composites of (a) XRD, and (b) FTIR.

    • Figure 10. 

      SEM results for Ref, A1, A2, B2, C2, D2, A3.

    • Figure 11. 

      Results of TG and DTG.

    • Figure 12. 

      Influence of different biochar on the cement hydration mechanism.

    • Sample C (%) O (%) Si (%) Cl (%) K (%) Else (%)
      BC300 35.70 25.14 13.19 1.26 5.73 18.98
      SP300 38.50 19.39 11.67 − 1.67 28.77
      BC500 40.63 33.35 17.71 0.94 3.55 3.82
      SP500 44.59 20.06 18.19 − 4.13 13.03
      BC700 43.05 6.58 21.17 0.87 8.83 19.50
      SP700 45.58 19.10 21.88 − 2.78 10.66

      Table 1. 

      Elemental distribution in biochar (wt.%)

    • Sample CaO SiO2 Al2O3 CO2 SO3 Fe2O3 K2O Other
      Content 44.64 25.13 11.57 8.36 3.45 3.35 1.11 2.39

      Table 2. 

      Chemical composition of OPC (wt.%)

    • Samples OPC (g) Biochar (g) W/C
      Control (Ref) 400 0 0.4
      A1, A2, A3 396 4 0.4
      A1, A2, A3 392 8 0.4
      A1, A2, A3 388 12 0.4
      A1, A2, A3 380 20 0.4
      A1, A2, and A3 are BC300-cement composites, BC500-cement composites, BC700-cement composites, respectively.

      Table 3. 

      Ratio of different biochar incorporated into cement composites

    • Sample BET surface area
      (m2·g−1)      		 Adsorption average pore size (nm) Cumulative adsorption pore volume (cm3·g−1)
      BC300 9.804 7.158 0.019
      SP300 18.528 6.425 0.022
      BC500 36.913 5.974 0.024
      SP500 54.658 6.362 0.040
      BC700 140.013 4.676 0.044
      SP700 150.064 4.487 0.047
      MBC300 2.894 6.924 0.012
      MSP300 17.194 4.688 0.017
      MBC500 29.691 4.613 0.033
      MSP500 36.060 4.683 0.026
      MBC700 124.607 4.676 0.044
      MSP700 134.141 4.057 0.034

      Table 4. 

      The surface area, cumulative adsorption pore volume, and adsorption average pore size of the different biochars

    • Model Pfo Model Pso Model Avrami
      Parameters qe k1 R2 qe k2 R2 qe kA n R2
      BC300 14.59 1.5087 0.9270 15.23 0.1489 0.8501 14.43 2.5684 2.2174 0.9974
      BC500 17.99 0.9815 0.9265 19.03 0.0676 0.8825 17.69 1.6072 2.7757 0.9959
      BC700 28.30 1.6080 0.9243 29.48 0.0829 0.8468 27.91 3.1152 2.2713 0.9951
      MBC300 23.59 1.0378 0.9808 24.92 0.0613 0.9360 23.43 1.0987 1.2791 0.9886
      MBC500 32.53 1.6775 0.9072 33.80 0.0770 0.8138 32.14 3.6354 2.5360 0.9982
      MBC700 29.10 1.6533 0.9217 30.27 0.0838 0.8380 28.72 3.2764 2.3077 0.9981
      SP300 25.93 0.8307 0.9509 27.70 0.0393 0.9057 25.53 0.9339 2.0888 0.9936
      SP500 27.72 1.9289 0.9283 28.69 0.1096 0.8283 27.47 3.4575 2.0176 0.9960
      MSP300 31.08 1.0106 0.9168 32.98 0.0416 0.8571 30.68 1.3309 2.7293 0.9978
      MSP500 32.97 1.9945 0.9096 34.13 0.0949 0.8037 32.61 4.6009 2.3394 0.9989

      Table 5. 

      Adsorption kinetics parameters of biochar to CO2

    • Item Ca(OH)2 CaCO3
      Ref 2.822 5.474
      A1 2.685 5.989
      A2 2.883 5.273
      A3 2.806 6.164
      B2 2.967 5.782
      C2 2.759 6.451
      D2 2.693 6.511

      Table 6. 

      Mass loss of Ca(OH)2 and CaCO3 in various biochar cement composites (wt.%)

    • Materials/processes
      (10−5 kg)      		 Without BC A2/B2/C2/D2 (1%) A2/B2/C2/D2 (2%) A2/B2/C2/D2 (3%) A2/B2/C2/D2 (5%) Ecoinvent inputs
      OPC 29400 29100 28800 28500 27900 Cement production, Portland
      Water 2.69 2.69/4.93/4.37/6.61 2.69/7.17/6.05/10.53 2.69/9.41/7.73/14.45 2.69/13.89/11.09/22.29 Tap water production, conventional treatment
      BC500 production (−) − 138.33/173.94/
      138.33/173.94      		 276.66/347.88/
      276.66/347.88      		 414.99/521.82/
      414.99/521.82      		 691.65/869.70/
      691.65/869.70      		 Biochar preparation
      NaOH − 0/0/636/636 0/0/1272/1272 0/0/1908/1908 0/0/3180/3180 China carbon emissions database
      Transportation 164.4 168.48/168.62/
      168.48/168.62      		 172.55/172.84/
      172.55/172.84      		 176.63/177.07/
      176.63/177.07      		 184.77/185.52/
      184.77/185.52      		 Transportation distance: 30 km
      Avoided emission (−) − 0.59/0.60/0.59/0.60 1.17/1.20/1.17/1.20 1.76/1.81/1.76/1.81 2.93/3.01/2.93/3.01 −
      Net emission 29567.088 29132.25/29099.01/
      29769.93/29736.69      		 28697.41/28630.93/
      29972.77/29906.29      		 28262.57/28162.85/
      30175.61/30075.89      		 27392.88/27226.70/
      30581.28/30415.10      		 −

      Table 7. 

      Carbon emissions of biochar cement composites