This study investigates the size effect on the compressive strength of foamed concrete at the mesoscale level combining X-ray computed tomography (X-CT) and a discrete lattice model. Image segmentation techniques and X-CT were employed to obtain virtual specimens comprising hydrated cement paste and air voids. The lineal-path function and pore size distribution was used to characterise the air void structure. A two-dimensional lattice fracture model of foamed concrete considering different wet densities was established. The model was verified experimentally at a wet density of 700 kg/m and then used to predict the strengths of specimens with wet densities of 600 and 800 kg/m. Square and rectangular specimens (slenderness ratio = 2) with widths of 10, 20, 40, 70.7, and 100 mm were investigated. Results show that the air void structure significantly influences the observed size effect on the compressive strength in the investigated size range. A random forest regressor was used to predict the compressive strength of the foamed concrete; the regressor yielded satisfactory results. Finally, existing analytical size effect models were used to fit the simulated strength. Although good fitting was achieved, special attention should be given to the applicable range and physical meaning of fitted empirical parameters.

中文翻译：

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泡沫混凝土抗压强度的尺寸效应：实验和数值研究

本研究结合 X 射线计算机断层扫描 (X-CT) 和离散晶格模型，研究介尺度水平上泡沫混凝土抗压强度的尺寸效应。采用图像分割技术和 X-CT 来获得包含水化水泥浆体和气孔的虚拟样本。线性路径函数和孔径分布用于表征气孔结构。建立了考虑不同湿密度的泡沫混凝土二维晶格断裂模型。该模型在湿密度为700 kg/m3下进行了实验验证，然后用于预测湿密度为600和800 kg/m3试件的强度。研究了宽度为 10、20、40、70.7 和 100 mm 的正方形和矩形试样（长细比 = 2）。结果表明，在所研究的尺寸范围内，气孔结构显着影响观察到的抗压强度尺寸效应。使用随机森林回归器来预测泡沫混凝土的抗压强度；回归器得到了令人满意的结果。最后，使用现有的分析尺寸效应模型来拟合模拟强度。虽然取得了良好的拟合效果，但应特别注意拟合经验参数的适用范围和物理意义。