摘要
利用混凝土搅拌站废水作为拌和水,制备了超硫酸盐水泥混凝土,研究了其力学和抗冻性能,并通过扫描电镜、X射线衍射仪及低场核磁共振观察了混凝土的微观形貌、物相组成及孔隙特征.结果表明:全废水超硫酸盐水泥混凝土早期抗压强度较低,后期抗压强度发展较快;水胶比0.41的全废水超硫酸盐水泥混凝土掺入80%矿渣后,其28 d抗压强度可达48.6 MPa,矿渣中的玻璃体被废水中的O
关键词
在“双碳”目标的指导
混凝土搅拌站废水(简称废水)指用于冲洗罐车、泵车、搅拌机及配套设备后,经沉淀处理排出的污
本文采用工业废弃物和废水制备了高性能超硫酸盐水泥混凝土,探究了其力学与抗冻性能,以期解决废水碱度高、污染大及处理难等问题,为西北高寒易受冻害地区的混凝土结构设计提供理论基础和技术支撑.
矿渣(S)为S95级矿渣,密度为3.00 g/c

图1 矿渣和脱硫石膏的粒径分布
Fig.1 Particle size distributions of slag and desulfurized gypsum
Material | SiO2 | CaO | Al2O3 | Fe2O3 | MgO | SO3 | TiO2 |
---|---|---|---|---|---|---|---|
S | 26.8 | 40.2 | 15.2 | 0.3 | 10.1 | 3.2 | 2.5 |
DG | 5.5 | 39.1 | 3.9 | 0.5 | 1.5 | 47.4 | 0.1 |
C | 21.9 | 58.8 | 6.9 | 3.6 | 2.6 | 3.9 | 0.4 |
根据文献[
Specimen | S | DG | C | FA | CA | FW | WW | WR |
---|---|---|---|---|---|---|---|---|
0.36S75‑W0 | 345.0 | 92.0 | 23.0 | 735.0 | 1 040.0 | 165.0 | 0 | 9.2 |
0.36S75‑W100 | 345.0 | 92.0 | 23.0 | 735.0 | 1 040.0 | 0 | 165.0 | 9.2 |
0.36S80‑W0 | 368.0 | 69.0 | 23.0 | 735.0 | 1 040.0 | 165.0 | 0 | 9.2 |
0.36S80‑W100 | 368.0 | 69.0 | 23.0 | 735.0 | 1 040.0 | 0 | 165.0 | 9.2 |
0.36S85‑W0 | 391.0 | 46.0 | 23.0 | 735.0 | 1 040.0 | 165.0 | 0 | 9.2 |
0.36S85‑W100 | 391.0 | 46.0 | 23.0 | 735.0 | 1 040.0 | 0 | 165.0 | 9.2 |
0.41S75‑W0 | 300.0 | 80.0 | 20.0 | 805.0 | 1 030.0 | 165.0 | 0 | 8.0 |
0.41S75‑W100 | 300.0 | 80.0 | 20.0 | 805.0 | 1 030.0 | 0 | 165.0 | 8.0 |
0.41S80‑W0 | 320.0 | 60.0 | 20.0 | 805.0 | 1 030.0 | 165.0 | 0 | 8.0 |
0.41S80‑W100 | 320.0 | 60.0 | 20.0 | 805.0 | 1 030.0 | 0 | 165.0 | 8.0 |
0.41S85‑W0 | 340.0 | 40.0 | 20.0 | 805.0 | 1 030.0 | 165.0 | 0 | 8.0 |
0.41S85‑W100 | 340.0 | 40.0 | 20.0 | 805.0 | 1 030.0 | 0 | 165.0 | 8.0 |
超硫酸盐水泥混凝土的抗压强度见

图2 超硫酸盐水泥混凝土的抗压强度
Fig.2 Compressive strength of supersulfated cement concretes
冻融次数N对超硫酸盐水泥混凝土质量损失率的影响见

图3 冻融次数对超硫酸盐水泥混凝土质量损失率的影响
Fig.3 Effect of freezing‑thawing cycles on mass loss rate of supersulfated cement concretes
冻融后超硫酸盐水泥混凝土的抗压强度见

图4 冻融后超硫酸盐水泥混凝土的抗压强度
Fig.4 Compressive strength of supersulfated cement concretes after freezing‑thawing(N=100 times)
全废水超硫酸盐水泥混凝土的XRD图谱见

图5 全废水超硫酸盐水泥混凝土的XRD图谱
Fig.5 XRD patterns of full wastewater supersulfated cement concretes
冻融前后全废水超硫酸盐水泥混凝土的SEM照片见图

图6 冻融前全废水超硫酸盐水泥混凝土的SEM照片
Fig.6 SEM images of full wastewater supersulfated cement concretes before freezing‑thawing

图7 冻融后全废水超硫酸盐水泥混凝土的SEM照片
Fig.7 SEM images of full wastewater supersulfated cement concretes after freezing‑thawing(N=100 times)
综上,随着冻融次数的增加,全废水超硫酸盐水泥混凝土质量损失加剧,强度下降明显,内部裂缝与断层发展迅速.
为表征全废水超硫酸盐水泥混凝土的孔隙变化,对试件0.41S80‑W100冻融前后的孔隙率和孔隙结构进行LF‑NMR测试.冻融前试件的孔隙率为2.5%,经过100次冻融后其孔隙率增加至3.5%,可见冻融后试件的孔隙数量增多,内部孔洞和裂缝增多是造成试件强度下降的原因之一.冻融前后试件0.41S80‑W100的T2谱分布曲线见

图8 冻融前后试件0.41S80‑W100的谱分布曲线
Fig.8 spectrum distributions of specimen 0.41S80‑W100 before and after freezing‑thawing(N=100 times)
(1)超硫酸盐水泥混凝土早期抗压强度较低,后期抗压强度发展较快.随着矿渣掺量的增加,全废水超硫酸盐水泥混凝土的抗压强度呈先增加后降低的趋势,水胶比0.41、矿渣掺量为80%的全废水超硫酸盐混凝土抗压强度为最高值48.6 MPa.
(2)随着冻融次数的增加,超硫酸盐水泥混凝土的质量损失率呈先降低后增加的趋势,冻融25次时试件的质量损失率最低,经过100次冻融后试件的抗压强度下降;全废水超硫酸盐水泥混凝土的抗压强度均低于全清水超硫酸盐水泥混凝土.
(3)废水属于高碱环境,大量O
(4)全废水加速了矿渣的水化反应,提高了超硫酸盐水泥混凝土的抗压强度,这可为全废水超硫酸盐水泥混凝土在实际工程中的应用提供参考.
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