Influence of Temperature on Performance and Microporous Structure of Foamed Concrete during Pouring Period
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摘要:
泡沫混凝土在浇筑至固化成型这段时期内，易受温度等环境因素影响，不利环境因素会导致固化成型后泡沫混凝土的性能退化和劣化. 为研究泡沫混凝土在浇筑期受温度（−15～70 ℃）影响后的性能和微孔结构，设计单因素室内试验方案，以干密度作为泡沫混凝土物理性质评价指标，抗压强度作为施工质量评价指标，吸水率用以评价泡沫混凝土的运营耐久性，并利用图像数据采集系统及Image J软件分析泡沫混凝土微孔结构的演变规律. 结果表明：随着温度上升，泡沫混凝土干密度总体呈阶梯式下降，抗压强度先减小后增大再减小，吸水率以0 ℃为分界点，温度降低或升高均呈先增大后减小趋势；等效孔径先增大后减小再增大，孔隙圆度值先增大后减小，孔隙分布分维先减小后变大；从混凝土宏观性能和微孔结构的演变规律建议泡沫混凝土浇筑期施工的温度范围为−5～40 ℃.
Abstract:Foamed concrete is susceptible to environmental factors such as temperature during the period from pouring to curing and molding, and adverse environmental factors can lead to performance degradation and deterioration of foamed concrete after curing and molding. In order to study the performance and microporous structure of foamed concrete affected by temperature (−15–70 ℃) during the pouring period, a single factor indoor test program was designed by using dry density, compressive strength, and water absorption to evaluate the physical property of foamed concrete, the construction quality, and the operational durability of foamed concrete, respectively. In addition, the evolution of the microporous structure of foamed concrete was analyzed by using an image data acquisition system and Image J software. The results show that the dry density of foamed concrete generally decreases in a stepwise manner as the temperature rises. The compressive strength first decreases, then increases, and finally decreases. The water absorption rate takes 0 ℃ as the cut-off point, and it tends to increase and then decrease when the temperature decreases or increases. The equivalent pore size shows a trend of increasing, decreasing, and increasing. The pore roundness value first increases and then decreases. The fractal dimension of pore distribution first decreases and then becomes larger. The results of macroscopic performance and microporous structure show that the recommended temperature range for the construction of foamed concrete during the pouring period is −5–40 ℃.
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Key words:
- foamed concrete /
- pouring period /
- temperature /
- macroscopic performance /
- microporous structure
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图 2 浇筑期温度对泡沫混凝土干密度的影响
Figure 2. Effect of temperature on dry density of foamed concrete during pouring period
图 3 浇筑期温度对泡沫混凝土抗压强度的影响
Figure 3. Effect of temperature on compressive strength of foamed concrete during pouring period
图 4 浇筑期温度对泡沫混凝土吸水率的影响
Figure 4. Effect of temperature on water absorption of foamed concrete during pouring period
图 5 20 ℃以下的泡沫混凝土累计孔径分布
Figure 5. Cumulative pore size distribution of foamed concrete below 20 ℃
图 6 20 ℃以下的泡沫混凝土孔径分布及对应孔隙图
Figure 6. Pore size distribution and corresponding pore images of foamed concrete below 20 ℃
图 7 20 ℃以上的泡沫混凝土累计孔径分布
Figure 7. Cumulative pore size distribution of foamed concrete above 20 ℃
图 8 20 ℃以上的泡沫混凝土孔径分布及对应孔隙图
Figure 8. Pore size distribution and corresponding pore images of foamed concrete above 20 ℃
图 9 浇筑期温度对泡沫混凝土孔隙圆度值的影响
Figure 9. Effect of temperature on pore roundness value of foamed concrete during pouring period
图 10 浇筑期温度对泡沫混凝土孔隙分布分维的影响
Figure 10. Effect of temperature on fractal dimension of pore distribution of foamed concrete during pouring period
表 1 水泥的主要化合物含量
Table 1. Main compound content of cement
% 名称 SiO2 K2O SO3 CaO Al2O3 Fe2O3 MgO Na2O 含量 20.31 0.39 2.12 65.55 4.80 4.93 1.35 0.12 
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表 2 水泥的物理力学性能指标
Table 2. Physical and mechanical properties of cement
名称 细度80 μm/% 标准稠度用水量/% 初凝时间/min 终凝时间/min 抗压强度 3 d/MPa 28 d/MPa 取值 1.20 25.48 165 232 28.7 45.4
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