摘要
采用X射线衍射分析、热分析、等温量热法和电感耦合等离子光谱法研究了羟丙基甲基纤维素(HPMC)对硫铝酸盐水泥水化的影响,并从孔溶液的性质和组成方面分析了其对水泥水化的影响机理.结果表明:HPMC改变硫铝酸盐水泥的水化放热速率,增加钙矾石(AFt)、单硫型水化硫铝酸钙(AFm)和铝胶(AH3)的含量,促进AH3与CaSO4和Ca(OH)2反应,并促进AFt向AFm转变;HPMC降低硫铝酸盐水泥孔溶液的表面张力,增大孔溶液的pH值,降低孔溶液中SO的浓度,增加C
硫铝酸盐(CSA)水泥因其快硬、早强、抗冻等优良性能逐渐被广泛应用于工程实践中,针对CSA水泥的改性研究逐渐增多,主要关注于外加
尽管关于HPMC改性CSA水泥基材料的研究和应用不断涌现,HPMC在改性材料中的作用机理和对水泥水化的影响机理尚不明确.基于此,本文从HPMC对CSA水泥水化影响机理的角度开展研究,以完善该体系的水化理论,促进HPMC在CSA水泥中的推广应用.CSA水泥的主要矿物组成为硫铝酸钙()、硅酸二钙(C2S)和硫酸钙(),为避免影响因素过多,本文以超高强CSA水泥熟料直接粉磨后掺加C复配出的CSA水泥为研究对象,开展HPMC对CSA水泥水化影响的研究,并着重从孔溶液性质和组成的角度阐释HPMC对水化的影响机理.
配制CSA水泥的胶凝材料采用磨细后的CSA水泥熟料和纯
CaO | Al2O3 | SO3 | SiO2 | Fe2O3 | TiO2 | MgO | K2O | P2O5 | Na2O |
---|---|---|---|---|---|---|---|---|---|
43.05 | 33.55 | 9.28 | 7.73 | 1.94 | 1.66 | 1.66 | 0.62 | 0.16 | 0.10 |
C4A3 | C2S | C12A7 | C4AF | C | CaTiO3 | MgO |
---|---|---|---|---|---|---|
54.0 | 22.2 | 8.7 | 5.9 | 4.7 | 2.8 | 1.7 |
配制水泥浆体时,m(CSA水泥熟料)∶m(C)=85.0∶15.0,m(去离子水)∶m(CSA水泥熟料+C)=5.0∶1.0,未掺加HPMC的CSA水泥为参比样,HPMC掺量为水泥质量0.3%的CSA水泥为HPMC改性水泥.
按1.1中的配合比称取粉末状原材料和去离子水,先将去离子水倒入安瓿瓶中,然后在5 s内将粉末状原材料迅速倒入盛有去离子水的安瓿瓶中,人工快速搅拌1 min至试样混合均匀后,立即将安瓿瓶密封并放入美国TA公司的TAM Air 8通道等温微量热仪测量水化热,每间隔30 s记录1次数据,直至水化24 h.
按1.1中的配合比称取粉末状原材料混合均匀,加入称量好的去离子水并开始计时,用电动搅拌器搅拌水泥浆体至预定龄期(10 min、30 min、1 h、2 h、4 h、6 h、12 h和24 h)后,取50 mL水泥浆体移入配置了孔径为0.2 μm的微孔滤膜的高压过滤器,将过滤器密封后打开高压泵(1 MPa)阀门加压1~2 min,用离心管收集过滤后的孔溶液,并取出固体试样用无水乙醇终止水化.将部分固体试样在40 ℃的真空干燥箱内烘干后密封保存,用于扫描电子显微(SEM)分析;将部分固体试样磨细后在40 ℃的真空干燥箱内烘干,再经0.106 mm方孔筛筛分后密封保存,用于X射线衍射(XRD)分析和热重(TG)分析.
将块状固体试样表面镀金,采用FEI Quanta 200型场发射环境扫描电子显微镜(ESEM)的低真空模式观察其微观形貌.采用Rigaku D/max 2550型XRD仪分析固体粉末样品的物相组成,Cu Kα为辐射源,加速电压为40 kV,电流为100 mA,连续扫描速率为2(°)/min.采用NETZSCH TG 209 F1型TG分析仪对固体粉末样品进行物相分析,测试温度范围为30~1 000 ℃,升温速率为10 ℃/min,保护气氛为N2,依据TG曲线在50~180 ℃和250~330 ℃的失重率分别计算AFt和AH3的含
采用雷磁PHSJ‑6L型pH计测定孔溶液的pH值.采用上海衡平BZY‑2型全自动界面张力仪测试孔溶液的表面张力.采用Agilent 720ES型电感耦合等离子体发射光谱仪测试孔溶液中3种无机元素Ca、Al、S的含量,并分析孔溶液中相应C
CSA水泥和HPMC改性水泥的水化放热曲线如

图1 CSA水泥和HPMC改性水泥的水化放热曲线
Fig.1 Hydration heat release curves of CSA cement and HPMC modified cement
Type | 0-40 min | 40-12 h | 12-24 h |
---|---|---|---|
CSA cement | 106 | 749 | 48 |
HPMC modified cement | 88 | 770 | 46 |
若CSA水泥中的C量充足,主要发生如
(1) |
(2) |
(3) |
(4) |

图2 CSA水泥和HPMC改性水泥在不同水化阶段的XRD图谱
Fig.2 XRD patterns of CSA cement and HPMC modified cement at different hydration stages

图3 CSA水泥和HPMC改性水泥在不同水化阶段的TG/DTG曲线
Fig.3 TG/DTG curves of CSA cement and HPMC modified cement at different hydration stages

图4 不同水化阶段CSA水泥和HPMC改性水泥中AFt的含量
Fig.4 AFt contents in CSA cement and HPMC modified cement at different hydration stages

图5 不同水化阶段CSA水泥和HPMC改性水泥中AH3的含量
Fig.5 AH3 contents in CSA cement and HPMC modified cement at different hydration stages

图6 水化2、24 h时CSA水泥和HPMC改性水泥的SEM图片
Fig.6 SEM images of CSA cement and HPMC modified cement at hydration time of 2,24 h
在强碱性条件下,若忽略

图7 不同水化阶段CSA水泥和HPMC改性水泥孔溶液的pH值
Fig.7 pH values of pore solutions of CSA cement and HPMC modified cement at different hydration stages
(5) |

图8 不同水化阶段CSA水泥和HPMC改性水泥孔溶液的表面张力
Fig.8 Surface tensions of pore solutions of CSA cement and HPMC modified cement at different hydration stages

图9 不同水化阶段CSA水泥和HPMC改性水泥孔溶液中C
Fig.9 Concentrations of C
Type | Phase | 10 min | 30 min | 1 h | 2 h | 4 h | 6 h | 12 h | 24 h |
---|---|---|---|---|---|---|---|---|---|
CSA cement | AFt |
1.6×1 |
3.3×1 |
7.6×1 |
3.4×1 |
1.2×1 |
1.1×1 |
1.1×1 |
1.6×1 |
AFm |
6.6×1 |
9.0×1 |
3.2×1 |
8.4×1 |
1.2×1 |
7.3×1 |
4.2×1 |
1.2×1 | |
AH3 |
1.3×1 | 2.9 |
1.1×1 |
1.2×1 | 6.6 | 5.3 | 2.9 |
8.6×1 | |
HPMC modified cement | AFt |
7.3×1 |
5.7×1 |
5.1×1 |
9.0×1 |
1.4×1 |
5.7×1 |
2.5×1 |
9.1×1 |
AFm |
6.8×1 |
1.4×1 |
2.1×1 |
4.4×1 |
7.3×1 |
3.2×1 |
6.5×1 |
1.3×1 | |
AH3 | 9.2 | 3.9 |
5.0×1 |
6.4×1 |
9.2×1 |
8.9×1 |
3.0×1 |
2.3×1 |
综合孔溶液pH值、表面张力和离子浓度结果可见:HPMC是非离子型聚合物,其分散在孔溶液中会影响水泥中矿物的溶解和水化产物的析出,改变孔溶液性质,这是影响水泥矿物溶解、改变离子浓度的主要因素;HPMC改变孔溶液中不同离子的浓度和比例,从而改变水化产物的离子浓度积,影响水化产物的析出速率、水化产物的种类和数量;HPMC通过影响水泥水化各阶段的离子浓度调控水化反应的溶解‑沉淀平衡,进而影响水泥的水化进程.
(1)羟丙基甲纤维素(HPMC)主要影响硫铝酸盐(CSA)水泥12 h内的水化反应,降低水化溶解放热峰,延迟但提高第1水化放热峰,加速并提高第2水化放热峰,减少水化溶解放热阶段(40 min内)的放热量,增加快速水化期(40 min~12 h)的放热量.
(2)HPMC改性水泥中的水化产物主要为钙矾石(AFt)、单硫型水化硫铝酸钙(AFm)和铝胶(AH3),水化2 h时AFt和AH3的含量有所增加;HPMC促进AH3与CaSO4和Ca(OH)2反应生成AFt,促进水化后期AFt向AFm转化;HPMC改性水泥水化2 h时,所生成的AFt晶体尺寸较CSA水泥显著增大,且交织更为紧密;HPMC改性水泥水化24 h时,所生成的片状AFm含量较CSA水泥有所增多.
(3)HPMC提高孔溶液的pH值,降低孔溶液的表面张力;水化初期,HPMC显著减小孔溶液中S的浓度,增大C
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