摘要
为研究微晶氢氧化铝凝胶(AH3)含量对高碱碳铝酸盐胶凝材料性能的影响,设计了氢氧化钠与氢氧化铝复合溶液、偏铝酸钠溶液复配激发石灰石粉的方案.结果表明:随着激发剂中偏铝酸钠溶液的占比从0%逐步增至100%,基体中的单碳型碳铝酸钙含量相对稳定,而微晶AH3的含量则逐渐增加,三水铝石的含量相应减少;微晶AH3的平均晶粒尺寸约19.5 nm,显著小于三水铝石的中值粒径5.82 μm,因而微晶AH3具有更大的比表面积和更强的胶凝性能;随着微晶AH3含量的增加,基体中凝胶孔的占比提升,孔隙结构更致密;试样抗压强度与微晶AH3含量之间呈线性正相关关系,即微晶AH3的含量越高,试样的强度越高.
关键词
石灰石作为碳酸钙矿物在地球上的主要赋存形式,广泛分布于岩石圈,其储量占沉积岩总量的20%~25
石灰石粉亦可作为水泥混凝土的辅助胶凝材料,用来降低水泥熟料的用量和碳排放.虽然石灰石粉的溶解度较低,但是它能与硅酸盐水泥中的铝酸盐矿物反应.然而,由于硅酸盐水泥中铝酸盐矿物含量有限,石灰石粉在其中的反应程度较低,因此石灰石粉掺量过高会劣化水泥基体的力学性
Liu
AH3是硫铝酸盐水泥和铝酸盐水泥中的关键物
基于此,本文配制了氢氧化钠与氢氧化铝复合溶液、偏铝酸钠溶液,设计了用两者复配来激发石灰石粉的方案.通过调整2种溶液的比例,在保证Mc生成量相对稳定的情况下,实现对AH3含量的调节.并对不同AH3含量下基体的反应过程、物相组成、微观形貌及宏观性能进行了研究,揭示了微晶AH3含量对高碱碳铝酸盐胶凝材料形成过程的影响机理.
石灰石粉(LM)购自广西贺州市亿泰石粉厂,其基本信息见文献[

图 1 Al(OH)3的颗粒形貌与粒径分布特征
Fig.1 Particle morphology and particle size distribution of Al(OH)3
Sample | LM | Solution A | Solution B |
---|---|---|---|
C1 | 62.0 | 38.0 | 0 |
C2 | 62.0 | 28.5 | 9.5 |
C3 | 62.0 | 19.0 | 19.0 |
C4 | 62.0 | 9.5 | 28.5 |
C5 | 62.0 | 0 | 38.0 |
通

图 2 试样C1~C5的T2 分布图、孔特征与T2w的演化
Fig. 2 T2 distribution, pore characteristics and T2w evolution of samples C1-C5
基于此,本文分析了激发剂中溶液B的占比wB从0%(试样C1)逐步增至100%(试样C5)时,72 h内凝胶孔水含量及T2w降低值(ΔT2w)的变化情况,结果如

图 3 溶液B在激发剂中的占比对试样中凝胶孔水含量与ΔT2w的影响
Fig.3 Influence of the proportion of solution B in the activator on the water content in gel pore and ΔT2w of samples(72 h)

图 4 试样C1~C5的XRD图谱
Fig.4 XRD patterns of samples C1-C5

图 5 试样C1~C5的物相组成
Fig.5 Phase compositions of samples C1-C5
由
由
为了确定NQ相的组成,使用NMR分析了试样

图 6 试样C1、C3与C5养护28 d时
Fig.6
由

图 7 溶液B占比对试样中三水铝石与AH3含量的影响
Fig.7 Influence of the proportion of solution B in the activator on the content of gibbsite and AH3 in samples
进一步验证试样C1~C5中的物相变化情况,其养护28 d时的TG‑DTG曲线见

图 8 试样C1~C5养护28 d时的TG‑DTG曲线
Fig.8 TG‑DTG curves of samples C1-C5 cured for 28 d

图 9 试样C1~C5的抗压强度
Fig.9 Compressive strength of samples C1-C5
根据2.2的分析结果,随着激发剂中溶液B占比从0%(试样C1)增至100%(试样C5),三水铝石的含量逐渐减少,而微晶AH3的含量相应增加.为了明确微晶AH3含量对力学性能的影响,分析了抗压强度与AH3含量之间的相关性,结果如

图 10 抗压强度与AH3含量的相关性
Fig.10 Correlation between compressive strength and AH3 content
上述分析表明,微晶AH3相比于三水铝石具有更优的胶凝性能.在水泥基体中,物相的胶凝性能与其比表面积有关.通常情况下,颗粒越细,其比表面积越大,胶凝性能越
Calculation method | Angular range/(°) | D/nm | |
---|---|---|---|
1 d | 28 d | ||
Scherrer method (EVA) | 18.0-19.5 | 19.5 | 19.7 |
19.5-21.0 | 19.8 | 20.0 | |
LVOL‑IB (TOPAS) | 18.0-21.0 | 18.8 | 19.0 |
LVOL‑FWHM (TOPAS) | 18.0-21.0 | 19.2 | 19.5 |
物相的比表面积S可通过下式计
(1) |
式中:ρ为密度.
三水铝石的晶粒尺寸同

图 11 试样养护28 d时的SEM图像和EDS点扫图谱
Fig.11 SEM images and EDS spectra of spots of samples cured for 28 d
(1)当氢氧化钠及氢氧化铝复配溶液与偏铝酸钠溶液的质量比改变,但Na2O与Al2O3在胶凝材料中的质量分数保持不变时,硬化基体中的单碳型碳铝酸钙Mc含量相对稳定,而三水铝石与微晶AH3的含量则随之变化.
(2)随着激发剂中偏铝酸钠溶液的占比从0%逐步增至100%,基体中三水铝石的含量降低,微晶AH3的含量增加.微晶AH3含量的增加导致基体中凝胶孔的占比提高,孔隙结构变得更加致密.
(3)在Mc含量保持基本稳定时,基体的抗压强度与微晶AH3的含量呈线性正相关,即AH3的含量越高,硬化试样的强度也越高.微晶AH3的平均晶粒尺寸约为19.6 nm,显著小于三水铝石的中值粒径5.82 μm,因此微晶AH3具有更大的比表面积和更强的胶凝性能.
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