摘要
开展了粉煤灰(FA)、矿渣微粉(GBFS)、提钛尾渣(TS)等3种矿物掺合料对泡沫混凝土性能影响的研究.结果表明:3种掺合料均能在一定程度上提高泡沫混凝土的体积密度,其中TS的影响尤为明显;GBFS会降低泡沫混凝土的流动度,但TS和低掺量FA能提高其流动度;3种矿物掺合料在低掺量时均能提高泡沫混凝土的体积吸水率和毛细吸水率,但在较高掺量时,又降低了其体积吸水率和毛细吸水率,其中TS和GBFS的降低作用尤为明显; 3种矿物掺合料在高掺量时均能明显提高泡沫混凝土的抗压强度,其中TS的提升效果最好;FA和GBFS提高了泡沫混凝土的28 d干燥收缩率,TS则显著降低其28 d干燥收缩率;综合而言,FA和GBFS最佳掺量范围均为10%~15%,TS为5%~15%.
泡沫混凝土具有水泥用量低、体积密度低、保温性能好等优点,是一种具有低碳足迹的轻质多孔水泥基材
鉴于此,本研究以硅酸盐水泥-硫铝酸盐水泥-脱硫石膏三元胶凝体系为胶凝材料,掺入发泡剂、稳泡剂及减水剂,基于物理发泡法制备泡沫混凝土;同时研究了粉煤灰、矿渣微粉和提钛尾渣等3种矿物掺合料及其掺量(质量分数,文中涉及的掺量、比值等均为质量分数或质量比)变化对该三元胶凝体系泡沫混凝土关键性能的影响规律,以期为其在该三元胶凝体系泡沫混凝土中的应用提供一定的理论和技术支撑.
胶凝材料包括P·O 42.5 硅酸盐水泥(OPC)、52.5级硫铝酸盐水泥(CSA)和半水脱硫石膏(FDG).矿物掺合料包括粉煤灰(FA)、矿渣微粉(GBFS)和提钛尾渣(TS).上述原材料的化学组成及平均颗粒尺寸如
Sample | Chemical compostion/% | Mean particle size/μm | |||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
SiO2 | Al2O3 | CaO | Fe2O3 | SO3 | TiO2 | MgO | K2O | Na2O | P2O5 | ||
OPC | 18.24 | 3.99 | 67.72 | 2.98 | 3.31 | 0.20 | 2.17 | 0.74 | 0.10 | 19.25 | |
CSA | 8.74 | 33.91 | 43.42 | 1.64 | 7.92 | 1.49 | 1.77 | 0.48 | 0.06 | 9.70 | |
FDG | 1.24 | 0.62 | 42.20 | 0.23 | 54.28 | 0.04 | 0.44 | 0.07 | 0.02 | 21.04 | |
FA | 42.50 | 31.80 | 9.04 | 3.78 | 1.52 | 1.13 | 0.76 | 0.60 | 0.50 | 0.37 | 30.05 |
GBFS | 28.70 | 11.90 | 43.40 | 0.24 | 1.93 | 0.61 | 6.36 | 0.30 | 0.01 | 7.54 | |
TS | 40.30 | 29.00 | 9.44 | 3.96 | 1.59 | 1.19 | 0.73 | 0.60 | 0.47 | 0.36 | 34.95 |

图1 胶凝材料和矿物掺合料的颗粒分布
Fig.1 Particle size distributions of binders and mineral admixtures
泡沫混凝土的配合比如
Sample No. | OPC | CSA | FDG | FA | GBFS | TS |
---|---|---|---|---|---|---|
Blank | 2 380 | 85 | 35 | 0 | 0 | 0 |
FA05 | 2 261 | 85 | 35 | 119 | 0 | 0 |
FA10 | 2 142 | 8 5 | 35 | 238 | 0 | 0 |
FA15 | 2 023 | 85 | 35 | 357 | 0 | 0 |
FA20 | 1 904 | 85 | 35 | 476 | 0 | 0 |
GBFS05 | 2 261 | 85 | 35 | 0 | 119 | 0 |
GBFS10 | 2 142 | 85 | 35 | 0 | 238 | 0 |
GBFS15 | 2 023 | 85 | 35 | 0 | 357 | 0 |
GBFS20 | 1 904 | 85 | 35 | 0 | 476 | 0 |
TS05 | 2 261 | 85 | 35 | 0 | 0 | 119 |
TS10 | 2 142 | 85 | 35 | 0 | 0 | 238 |
TS15 | 2 023 | 85 | 35 | 0 | 0 | 357 |
TS20 | 1 904 | 85 | 35 | 0 | 0 | 476 |
按照如下步骤制备泡沫混凝土:(1)向搅拌桶中加入胶凝材料、发泡剂、稳泡剂、减水剂等粉料,低速搅拌60 s得到干混粉料;(2)向干混粉料中加水,先低速搅拌2 min,然后高速搅拌发泡4 min,得到泡沫混凝土浆体;(3)浇筑泡沫混凝土浆体至不同模具中进行成型.
泡沫混凝土拌和物的流动度测试参照JC/T 985—2017《地面用水泥基自流平砂浆》“7.3流动度”试验进行,表观密度(以下简称新拌体积密度)测试参照JGJ/T 70—2009《建筑砂浆基本性能试验方法标准》“5 表观密度试验”进行.泡沫混凝土的干密度(或称干体积密度)和抗压强度测试按照JG/T 266—2011《泡沫混凝土》进行;硬化体积密度参照GB/T 9966.3—2020《天然石材试验方法 第3部分:吸水率、体积密度、真密度、真气孔率试验》进行. 泡沫混凝土的软化系数和体积吸水率测试分别参照GB/T 20473—2021《建筑保温砂浆》“6.9 软化系数”和“6.10 体积吸水率”试验进行.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》“8 收缩应力试验”进行.毛细孔吸水率测试参照ISO 15148—2002 Hygrothermal Performance of Building Materials and Products‑Determination of Water Absorption Coefficient by Partial Immersion进行,样品尺寸为40 mm×40 mm×160 mm;测试时将样品4个侧面用石蜡密封,并于室温下将样品成型面浸入水中,浸没深度为2~5 mm,在规定时间点称重记录总毛细吸水质量,计算得到毛细孔吸水率.
泡沫混凝土的硬化体积密度、干密度、吸水率、抗压强度测试用样品均在(23±2)℃、相对湿度(95±5)%的条件下养护至试验龄期.
3种矿物掺合料对泡沫混凝土体积密度(包括新拌体积密度、硬化体积密度和干密度)的影响如

图2 矿物掺合料对泡沫混凝土体积密度的影响
Fig.2 Effect of mineral admixtures on bulk density of foam concrete
基准组泡沫混凝土的干密度为457 kg/
TS使得泡沫混凝土的干密度显著增大,且干密度随其掺量增大而增大(
矿物掺合料对泡沫混凝土拌和物流动度的影响如

图3 矿物掺合料对泡沫混凝土流动度的影响
Fig.3 Effect of mineral admixtures on fluidity of foam concrete
矿物掺合料对泡沫混凝土体积吸水率和软化系数的影响如

图4 矿物掺合料对泡沫混凝土体积吸水率和软化系数的影响
Fig.4 Effect of mineral admixtures on volume water absorption and softening coefficient of foam concrete
软化系数能表征泡沫混凝土的耐水性,软化系数越高,耐水性越好,反之亦然.由(
矿物掺合料对泡沫混凝土毛细吸水率的影响如

图5 矿物掺合料对泡沫混凝土毛细吸水率的影响
Fig.5 Effect of mineral admixtures on water capillary absorption of foam concrete
矿物掺合料对泡沫混凝土抗压强度的影响如

图6 矿物掺合料对泡沫混凝土抗压强度的影响
Fig.6 Effect of mineral admixtures on compressive strength of foam concrete
由
由
矿物掺合料对泡沫混凝土干燥收缩率的影响如

图7 矿物掺合料对泡沫混凝土干燥收缩率的影响
Fig.7 Effect of mineral admixtures on drying shrinkage of foam concrete
水泥基材料的干燥收缩率与毛细孔失水速率密切相
综上所述,3种矿物掺合料均不同程度地影响到泡沫混凝土的性能.FA掺量5%~10%会使得泡沫混凝土具有较低的体积密度和较高的流动度,但掺量5%时体积吸水率和毛细吸水率过高,抗压强度偏低;FA掺量15%~20%使得泡沫混凝土具有较低的体积吸水率、毛细吸水率和干燥收缩率,以及较高的抗压强度和软化系数,但FA掺量为20%时流动性能较差.因此,FA在泡沫混凝土中的最佳掺量为10%~15%.
GBFS掺量增大使得泡沫混凝土的体积密度略微提升,流动度逐渐降低,抗压强度先降低后增大;GBFS掺量10%时,泡沫混凝土能维持较高的流动度和抗压强度,具有较低体积吸水率和毛细吸水率;GBFS掺量增至15%时,泡沫混凝土体积吸水率和毛细吸水率进一步降低,但流动度偏低.综合来看,GBFS在泡沫混凝土中的最佳掺量也为10%~15%.
TS能够显著增大泡沫混凝土的流动度,且掺量变化对流动度影响较小;TS掺量5%~10%使得泡沫混凝土具有较低体积密度,较高的抗压强度,但体积吸水率和毛细吸水率也较高;TS掺量15%~20%虽能降低体积吸水率和毛细吸水率,但会使得体积密度显著增大,尤其是20%时.综合而言,TS最佳掺量为5%~15%.
(1)粉煤灰(FA)、矿渣微粉(GBFS)及提钛尾渣(TS)对泡沫混凝土的性能具有显著而不同的影响.FA和GBFS未明显改变泡沫混凝土的体积密度,而TS使其体积密度明显增大;TS和低掺量FA能提高泡沫混凝土的流动度,而GBFS和高掺量FA明显降低其流动度.
(2)FA、GBFS和TS掺量增大使得泡沫混凝土的体积吸水率和毛细吸水率先增大而后降低,但3者影响程度不同:FA使得泡沫混凝土具有最高的体积吸水率和毛细吸水率,最低的软化系数和耐水性;高掺量的GBFS使得体积吸水率和毛细吸水率显著降低,软化系数和耐水性显著提升;高掺量的TS使得泡沫混凝土具有最低的体积吸水率和毛细吸水率,以及最优的耐水性.
(3)随着FA掺量的增大,泡沫混凝土的抗压强度尤其是早期抗压强度明显提高;低掺量GBFS会降低其抗压强度,但随其掺量增大,抗压强度有所提升;TS能显著提升泡沫混凝土抗压强度,且随其掺量增大而迅速提升.FA和GBFS均使得泡沫混凝土干燥收缩率有所提高,且掺量增大将加剧干燥收缩现象;TS能降低泡沫混凝土的干燥收缩率,且随着其掺量的增大,泡沫混凝土干燥收缩率逐渐降低,并具有良好的体积稳定性.
(4)3种矿物掺合料在泡沫混凝土中的最佳掺量范围分别为FA 10%~15%、GBFS 10%~15%、TS 5%~15%.
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