摘要
研究了水化铁硅酸钙/聚羧酸减水剂(C‑F‑S‑H/PCE)纳米晶核对矿粉水泥水化和力学性能的影响.采用力学性能测试、等温量热分析、X射线衍射仪和压汞法测试了大矿粉掺量(50%、70%、90%)矿粉水泥的抗压强度、水化放热、水化产物和孔隙率.结果表明:C‑F‑S‑H/PCE纳米晶核的掺入能够显著提升矿粉水泥的抗压强度,50%矿粉掺量的矿粉水泥1 d强度提升60%;C‑F‑S‑H/PCE纳米晶核对矿粉水泥的水化反应具有调控作用,通过加速水泥的早期水化及氢氧化钙的形成激发了矿粉反应活性,从而推动了矿粉反应的持续进行.
中国水泥产量占全球总产量的55%以
水化硅酸钙(C‑S‑H)凝胶是硅酸盐水泥主要的水化产物,也是水泥基材料强度的主要来源,因此提高早期C‑S‑H凝胶的生成量是提升水泥基材料早期强度的重要途径.由于C‑S‑H纳米晶核在组成、结构等方面与C‑S‑H凝胶类似,能够作为成核位点促进C‑S‑H凝胶的成核与生长,提升水泥基材料的早期强度发
为了评估新型纳米晶核对大掺量矿物掺合料水泥基材料的应用潜力,本文以新型C‑F‑S‑H/PCE纳米晶核为例,系统研究了其对大掺量矿粉取代水泥体系力学性能发展和水化进程的影响,以期为大掺量矿物掺合料复合水泥基材料的设计与应用提供新途径.
华新水泥股份有限公司产P·I 42.5基准水泥(PC),比表面积为358
Material | CaO | SiO2 | Al2O3 | Fe2O3 | MgO | Na2O | SO3 | IL |
---|---|---|---|---|---|---|---|---|
PC | 63.54 | 20.19 | 4.37 | 3.36 | 2.67 | 0.18 | 2.51 | 1.71 |
GGBFS | 40.11 | 32.07 | 15.67 | 0.39 | 6.95 | 0.33 | 2.19 | 2.29 |

图1 GGBFS的XRD图谱
Fig.1 XRD pattern of GGBFS
前期研究表
Solution A | Solution B | ||
---|---|---|---|
Ca(NO3)2·4H2O | Fe(NO3)3·9H2O | Na2SiO3·9H2O | |
100.0 | 3.0 | 100.0 |
试验采用矿粉分别替代50%、70%和90 %水泥,以探究不同矿粉掺量下C‑F‑S‑H/PCE纳米晶核对矿粉水泥早期强度及水化的影响.设置水胶比(mw/mb)为0.4,试验配合比如
Label | Sample No. | w(PC)/% | w(GGBFS)/% | w(C‑F‑S‑H/PCE )/% |
---|---|---|---|---|
① | PC | 100.0 | 0 | 0 |
② | S50 | 50.0 | 50.0 | 0 |
③ | S70 | 30.0 | 70.0 | 0 |
④ | S90 | 10.0 | 90.0 | 0 |
⑤ | S50 0.5% CFSH | 50.0 | 50.0 | 0.5 |
⑥ | S70 0.5% CFSH | 30.0 | 70.0 | 0.5 |
⑦ | S90 0.5% CFSH | 10.0 | 90.0 | 0.5 |
(1)力学性能测试
采用TYE‑300型力学性能测试机对养护龄期为1、3、28 d的试样进行抗压强度测试,加载速率为0.6 kN/s,每组试样均测试3次,取其平均值作为测试结果.
(2)水化热测试
采用TAM Air水化量热仪进行水化热分析.按配合比称取50 g矿粉和水泥的混合粉体进行预搅拌,利用超声波分散机将C‑F‑S‑H/PCE纳米晶核与去离子水先超声分散5 min,掺入胶凝材料中再搅拌5 min,制备得到矿粉水泥浆体;随后称取15 g浆体,置于20 mL安瓿瓶中进行水化放热测试,测试温度为20 ℃,测试时间为72 h.
(3)XRD分析
采用Empyrean型X射线衍射仪对各组1 d龄期试样进行测试.预先对试样进行破碎、研磨处理,研磨过程中添加占粉体质量10%的氧化锌作为内标物.扫描速率为2(°)/min,测试范围为5°~70°.
(4)压汞法(MIP)孔结构测试
采用AutoPore IV 9500型全自动压汞仪对各组1 d龄期试样进行压汞测试.预先对试样进行破碎处理.测试压力为0.001~228 MPa,孔径测量范围为5 nm~800 μm.
试样1、3、28 d抗压强度如

图2 试样1、3、28 d 抗压强度
Fig.2 Compressive strength of samples at 1, 3, 28 d
试样72 h水化放热曲线及累计放热量曲线如

图3 试样72 h水化放热曲线及累计放热量曲线
Fig.3 Hydration heat flow curves and cumulative heat release curves of samples within 72 h
由
由前可知,C‑F‑S‑H/PCE纳米晶核对矿粉水泥24 h内水化反应产生了显著的调控作用.因此针对1 d龄期矿粉水泥体系水化产物演变及微结构发展进行深入研究,各试样的XRD图谱如

图4 1 d龄期时试样的XRD图谱
Fig.4 XRD patterns of samples at 1 d
为进一步探究C‑F‑S‑H/PCE纳米晶核对大掺量矿粉取代水泥体系水化的影响,采用XRD分析测试方法对1 d龄期时各试样中的CH含量进行定量计算,结果如

图5 1 d龄期时试样中的CH含量
Fig.5 Content of CH in samples at 1 d
水泥基材料的孔隙类型主要包括4种,分别为凝胶孔(孔径D<10 nm)、过渡孔(10 nm≤D<100 nm)、毛细孔(100 nm≤D<1 000 nm)、大孔(D≥1 000 nm

图6 1 d龄期时试样的累计孔径曲线及孔径分布曲线
Fig.6 Cumulative aperture curves and pore size distribution curves of samples at 1 d
(1)C‑F‑S‑H/PCE纳米晶核的掺入能够显著促进大掺量矿粉取代水泥体系抗压强度的提升.50%掺量的矿粉取代水泥时体系1 d强度与普通硅酸盐水泥相当,且随着矿粉掺量的增加,体系抗压强度增幅变大.这表明C‑F‑S‑H/PCE纳米晶核对于提升大掺量矿粉取代水泥的水泥基材料强度发展具有显著优势.
(2)C‑F‑S‑H/PCE纳米晶核能够促进矿粉水泥体系水化反应的加速进行.在矿粉掺量为50%、70%和90%时,1 d龄期时体系累计放热量分别提升18%、42%和49%.C‑F‑S‑H/PCE纳米晶核的掺入显著提高了矿粉水化放热峰值,表明C‑F‑S‑H/PCE纳米晶核对矿粉的潜在胶凝性有提升作用.
(3)C‑F‑S‑H/PCE纳米晶核促进了水泥的早期水化反应速率及氢氧化钙(CH)的形成,1 d龄期时普通硅酸盐水泥中的CH含量增加29%;同时C‑F‑S‑H/PCE纳米晶核对于矿粉早期水化反应活性的提升导致矿粉对CH的消耗速率增大,从而使得大掺量矿粉取代水泥体系中CH含量降低.
(4)C‑F‑S‑H/PCE纳米晶核通过在早期提升矿粉水泥的水化反应程度,降低了大掺量矿粉水泥的孔体积,主要孔隙由100~1 000 nm的毛细管孔转变为小于10 nm的凝胶孔,体系微观结构致密程度得到显著提升.
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