摘要
为了构筑低吸湿泡沫混凝土并再生利用热解污泥,以表观密度、导热系数和28 d抗压强度为指标,采用正交设计试验确定了热解污泥粉、甲基硅醇钠和纳米二氧化硅的合理掺量,进而研究了最优组合泡沫混凝土的物理性能. 结果表明:以表观密度和导热系数为衡量指标时,热解污泥粉、甲基硅醇钠和纳米二氧化硅的合理掺量分别为30%、1.5%、3.0%,而以28 d抗压强度为衡量指标时,三者的合理掺量分别为10%、0.5%、3.0%;1.5%的甲基硅醇钠使得泡沫混凝土的吸湿性降低了90.6%~95.5%;最优组合泡沫混凝土的导热系数、表观密度和强度满足FC5自保温泡沫混凝土的基本要求.
建筑能耗高达总能耗的40
中国每年污泥产量约20亿t,利用率低. 研究表明,经热解处理后的污泥密度低,含有一定的玻璃
本文首先利用正交设计试验,以表观密度、导热系数和28 d抗压强度为衡量指标,探究热解污泥、甲基硅醇钠和纳米二氧化硅的合理掺量及其影响规律,进而研究优组合下泡沫混凝土的强度发展规律、表观密度、吸湿性和干缩性,以期提高泡沫混凝土的应用范围并为实现热解污泥的高值利用提供参考.
采用P·O 42.5R型水泥,其3、28 d抗压强度分别为22.5、46.8 MPa;热解污泥,其中CaO、SiO2和Al2O3的总含
Material | SiO2 | Al2O3 | Fe2O3 | CaO | MgO | SO3 | K2O | Na2O | IL |
---|---|---|---|---|---|---|---|---|---|
Cement | 18.3 | 4.5 | 2.3 | 62.4 | 2.1 | 3.5 | 1.5 | 0.3 | 2.6 |
Sludge | 15.7 | 7.2 | 11.7 | 44.3 | 2.7 | 5.7 | 6.1 | ||
nano‑SiO2 | 99.5 |
采用发泡机将发泡剂水溶液制成泡沫,按设定配合比首先干拌1 min,加入水和发泡剂慢拌1 min,加入稳泡剂和减水剂快拌2 min后,加入甲基硅醇钠再慢拌1 min,获得搅拌均匀的浆料,成型后在标准条件下养护3 d后脱模,采用保鲜膜覆盖,湿养护7 d,而后定期浇水保持试件湿润直到测试前2 d.
强度测试方法参照 GB/T 17671—2021《水泥胶砂强度检验方法(ISO法)》执行. 干燥收缩率测试参照GB/T 29417—2012《水泥砂浆和混凝土干燥收缩开裂性能试验方法》,试件尺寸为40 mm×40 mm×160 mm. 表观密度和导热系数测试按照JG/T 266—2011《泡沫混凝土》实施,测试结果取平均值.吸湿性按GB/T 35166—2017《建筑材料及制品的湿热性能 吸/放湿性能的测定 湿度反应法》测试,采用硝酸钾饱和盐溶液控制环境相对湿度为90%±5%,温度为25 ℃,试件静置到规定时间后取出测试其吸湿量.微观分析采用GeminiSEM300场发射扫描电子显微镜(SEM),观察前对样品镀金处理.
根据JGJ/T 341—2014《泡沫混凝土应用技术规程》进行配合比设计,水胶比为0.35,胶凝材料用量为750 kg/
Level | w(sludge)/% | w(sodium methyl‑silanolate)/% | w(nano‑SiO2)/% |
---|---|---|---|
1 | 10 | 0.5 | 1.0 |
2 | 20 | 1.0 | 3.0 |
3 | 30 | 1.5 | 5.0 |
以表观密度、导热系数和28 d抗压强度为衡量指标,采用正交设计,通过分析极差R确定优组合,结果如表
Mix No. | A | B | C | Apparent density/(g·c | Compressive strength(28 d)/MPa | Thermal conductivity/(W· |
---|---|---|---|---|---|---|
A1B1C1 | 1 | 1 | 1 | 0.940 | 7.98 | 0.357 |
A1B2C3 | 1 | 2 | 3 | 0.902 | 7.38 | 0.335 |
A1B3C2 | 1 | 3 | 2 | 0.866 | 6.59 | 0.289 |
A2B1C3 | 2 | 1 | 3 | 0.924 | 7.05 | 0.343 |
A2B2C2 | 2 | 2 | 2 | 0.881 | 6.69 | 0.288 |
A2B3C1 | 2 | 3 | 1 | 0.812 | 5.01 | 0.267 |
A3B1C2 | 3 | 1 | 2 | 0.889 | 6.66 | 0.295 |
A3B2C1 | 3 | 2 | 1 | 0.877 | 5.93 | 0.291 |
A3B3C3 | 3 | 3 | 3 | 0.808 | 4.55 | 0.260 |
Apparent density | Thermal conductivity | Compressive strength(28 d) | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
Parameter | A | B | C | Parameter | A | B | C | Parameter | A | B | C |
k1 | 0.327 | 0.332 | 0.305 | k1 | 0.318 | 0.276 | 0.259 | k1 | 8.260 | 7.200 | 6.410 |
k2 | 0.299 | 0.305 | 0.291 | k2 | 0.238 | 0.247 | 0.249 | k2 | 6.970 | 6.960 | 7.200 |
k3 | 0.282 | 0.271 | 0.313 | k3 | 0.205 | 0.238 | 0.252 | k3 | 5.490 | 6.570 | 7.110 |
R | 0.045 | 0.061 | 0.022 | R | 0.113 | 0.038 | 0.010 | R | 2.770 | 0.630 | 0.790 |
Impact weight | BAC | Impact weight | BAC | Impact weight | ACB | ||||||
Optimal mix | A3B3C2 | Optimal mix | A3B3C2 | Optimal mix | A1B1C2 |
为了定量分析泡沫混凝土导热系数、28 d抗压强度与表观密度的关系,本文对

图1 导热系数、28 d抗压强度与表观密度的关系
Fig.1 Relationship between thermal conductivity, 28 d compressive strength and apparent density
根据正交设计结果可知,当采用表观密度、导热系数和28 d抗压强度作为衡量指标时,最优组合分别为A3B3C2和A1B1C2. 为了获得综合性能较理想的配合比,分析了这2种组合的抗压和抗折强度发展规律,结果如
Mix No. | Compressive strength/MPa | Flexural strength/MPa | ||||||
---|---|---|---|---|---|---|---|---|
7 d | 28 d | 90 d | 180 d | 7 d | 28 d | 90 d | 180 d | |
A3B3C2 | 3.74 | 5.39 | 7.01 | 8.51 | 1.15 | 1.61 | 2.17 | 2.33 |
A3B0C2 | 4.12 | 6.08 | 7.75 | 9.84 | 1.19 | 1.75 | 2.23 | 2.58 |
A1B1C2 | 5.85 | 8.82 | 10.31 | 11.96 | 1.69 | 2.43 | 2.86 | 3.03 |
A1B0C2 | 6.49 | 9.03 | 10.45 | 12.04 | 1.82 | 2.53 | 2.92 | 3.11 |
由
甲基硅醇钠具有一定的引气作用.

图2 甲基硅醇钠的引气作用和憎水效果
Fig.2 Entraining‑air and hydrophobic effect of sodium methyl‑silanolate
由
吸湿性影响泡沫混凝土在潮湿环境中的保温效果,本文利用甲基硅醇钠来降低泡沫混凝土的吸湿性.泡沫混凝土的吸湿性和热工特性如
Mix No. | Hygroscopicity/(kg·k | Apparent density/(g·c | Porosity(by volume)/% | Thermal conductivity/(W· | ||
---|---|---|---|---|---|---|
3 d | 7 d | 28 d | ||||
A3B3C2 | 0.001 | 0.004 | 0.009 | 0.815±0.027 | 67.2 | 0.235±0.009 |
A3B0C2 | 0.022 | 0.057 | 0.096 | 0.929±0.032 | 62.3 | 0.350±0.011 |
A1B1C2 | 0.008 | 0.011 | 0.020 | 0.918±0.045 | 67.0 | 0.343±0.015 |
A1B0C2 | 0.021 | 0.043 | 0.081 | 1.003±0.071 | 64.4 | 0.401±0.022 |
由
由
A3B3C2、A1B1C2、A3B0C2 和A1B0C2的干缩性如

图 3 泡沫混凝土的干缩性
Fig.3 Dry shrinkage performance of foamed concrete
(1)正交设计试验表明甲基硅醇钠能显著影响泡沫混凝土的导热性,热解污泥粉能显著影响泡沫混凝土的强度.以表观密度和导热系数为衡量指标时,热解污泥粉、甲基硅醇钠和纳米二氧化硅的合理掺量分别为30%、1.5%和3.0%,而以28 d抗压强度为衡量指标时,3种原材料合理掺量分别为10%、0.5%和3.0%.
(2)甲基硅醇钠具有引气作用,可增强泡沫混凝土的保温效果,掺0.5%和1.5%的甲基硅醇钠可使泡沫混凝土的孔隙率分别增加2.6%、4.9%,导热系数分别降低16.9%、37.0%.
(3)甲基硅醇钠具有强憎水作用,掺0.5%和1.5%甲基硅醇钠保温材料的3~28 d吸湿性分别降低了61.5%~75.3%和90.6%~95.5%.
(4)采用优组合的配合比时,泡沫混凝土的28 d抗压强度超过5.0 MPa,干缩性和导热系数均满足FC5自保温泡沫混凝土的基本要求,因此,利用30%热解污泥粉、1.5%甲基硅醇钠和3.0%纳米二氧化硅可以构建低吸湿泡沫混凝土.
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