
青稞纤维表面改性及其对生态混凝土力学性能的影响
赵玉青, 王建翎
青稞纤维表面改性及其对生态混凝土力学性能的影响
Surface Modification of Highland Barley Fiber and Its Modification Effect on Mechanical Properties of Ecological Concrete
为了研究青稞纤维对生态混凝土力学性能的提升,采用NaOH、NaOH+ H2O2、冰醋酸+NaClO2等处理方法对青稞纤维进行表面改性处理,通过正交试验寻求最佳改性方式,同时借助XRD、FTIR、SEM等测试手段,从不同角度对不同处理的青稞纤维进行表征;将改性前后的青稞纤维掺入生态混凝土中,分别测试其抗压、劈裂抗拉和抗折强度,分析改性效果和对生态混凝土力学性能的影响规律。结果表明,采用6%NaOH+10% H2O2溶液在40~50 ℃环境下对青稞秸秆纤维预处理,表面改性效果优良;纤维的掺入减小了生态混凝土内部的孔隙含量,混凝土的立方体抗压强度有所降低,而抗拉、抗弯能力大大增强;相较于未改性纤维混凝土,改性纤维混凝土的28 d抗压、抗折、劈裂抗拉强度分别提高了4.3%、16.5%、20.3%,纤维素得到有效提纯,大大提高了生态混凝土结构的整体性和韧性。
In order to study the improvement of highland barley fiber on the mechanical properties of ecological concrete, NaOH, NaOH+H2O2, or glacial acetic acid + NaClO2 are used to modify the surface of highland barley fibers. The optimum modification method is sought through the orthogonal test. Meanwhile, with the assistance of modern material testing methods like XRD, FTIR, SEM etc., modification effects are evaluated from different perspectives. The highland barley fiber before and after modification is then mixed into ecological concrete, measuring its compressive, splitting tensile and flexural strength respectively to analyze modification effect and its influence on the mechanical properties of the ecological concrete. The results show that the pretreatment of highland barley fiber with 6%NaOH+10%H2O2 solution at 40~50 ℃ has a superior surface modification effect. In addition, the incorporation of fibers has decreased the pore contents inside the ecological concrete. The compressive strength of fiber ecological concrete is lower than that of ordinary ecological concrete, while its tensile and bending resistance are significantly enhanced. Compared to unmodified fiber concrete, the 28 d compressive, flexural, and splitting tensile strengths of modified fiber concrete has increased by 4.3%, 16.5% and 20.3% respectively. Hence, cellulose in highland barley fiber is effectively purified, which greatly improves the integrity and toughness of the ecological concrete structure.
青稞纤维 / 表面改性 / 生态混凝土 / 力学性能 {{custom_keyword}} /
highland barley fiber / surface modification / ecological concrete / mechanical properties {{custom_keyword}} /
图1 青稞秸秆宏观形貌及微观形貌Fig.1 Morphology of highland barley straw on macro and micro level |
表1 青稞秸秆纤维的基本性能参数Tab.1 Basic parameters of highland barley straw fiber |
密度/ (g·cm-3) | 拉伸强度/ MPa | 拉伸模量/ GPa | 断裂伸长率/ % |
---|---|---|---|
1.45 | 400~700 | 10~80 | 1.9 |
表2 水泥基本技术参数Tab.2 Basic technical parameters of cement |
密度/ (g·cm-3) | 细度/ % | 比表面积/ (m2·kg-1) | 凝结时间/min | 抗折强度/MPa | 抗压强度/MPa | |||
---|---|---|---|---|---|---|---|---|
初凝 | 终凝 | 3 d | 28 d | 3 d | 28 d | |||
3.1 | 4 | 355 | 205 | 265 | 5.3 | 9.8 | 25.6 | 50.7 |
表3 骨料的物理性能Tab.3 Physical properties of aggregates |
表观密度/(kg·m-3) | 紧密堆积密度/(kg·m-3) | 堆积密度/(kg·m-3) | 压碎 指标/% | 含泥量/% | 空隙率/% |
---|---|---|---|---|---|
2 780 | 1 540 | 1 380 | 8.20 | 0.19 | 45 |
表4 正交因素表Tab.4 Orthogonal factor table |
水平 | A 预处理溶液 | B 预处理时间/h | C 热处理温度/℃ |
---|---|---|---|
1 | 6%NaOH | 2 | 80 |
2 | 6%NaOH+10%H2O2 | 4 | 100 |
3 | 3%冰醋酸+1.5%NaClO2 | 6 | 120 |
表5 正交试验设计预处理方案Tab.5 Orthogonal design pretreatment scheme |
样品 编号 | A 预处理溶液 | B 预处理时间/h | C 热处理温度/℃ |
---|---|---|---|
T1 | 6%NaOH | 4 | 100 |
T2 | 6%NaOH | 2 | 80 |
T3 | 6%NaOH | 6 | 120 |
T4 | 6%NaOH+10%H2O2 | 6 | 80 |
T5 | 6% NaOH+10%H2O2 | 4 | 120 |
T6 | 6% NaOH+10%H2O2 | 2 | 100 |
T7 | 3%冰醋酸+1.5%NaClO2 | 2 | 120 |
T8 | 3%冰醋酸+1.5%NaClO2 | 6 | 100 |
T9 | 3%冰醋酸+1.5%NaClO2 | 4 | 80 |
表6 生态混凝土的配合比Tab.6 Mix ratio of ecological concrete |
集料粒径/ mm | 孔隙率/ % | 水灰比 | 粗集料/ (kg·m-3) | 水泥/ (kg·m-3) | 水/ (kg·m-3) | 减水剂/ (kg·m-3) | 增强剂/ (kg·m-3) |
---|---|---|---|---|---|---|---|
10~20 | 25 | 0.30 | 1 509 | 333 | 100 | 3.33 | 9 |
表7 正交试验极差分析表Tab.7 The table of Orthogonal test range analysis |
样品编号 | 因素 | 结晶度/% | ||
---|---|---|---|---|
A 预处理溶液 | B 预处理 时间/h | C 热处理 温度/℃ | ||
T0 | - | - | - | 46.81 |
T1 | 1 | 2 | 2 | 59.96 |
T2 | 1 | 1 | 1 | 57.24 |
T3 | 1 | 3 | 3 | 56.86 |
T4 | 2 | 3 | 1 | 63.80 |
T5 | 2 | 2 | 3 | 64.67 |
T6 | 2 | 1 | 2 | 68.41 |
T7 | 3 | 1 | 3 | 46.44 |
T8 | 3 | 3 | 2 | 47.45 |
T9 | 3 | 2 | 1 | 44.71 |
k1j | 58.02 | 57.36 | 55.25 | |
k2j | 65.63 | 56.45 | 58.61 | |
k3j | 46.20 | 56.04 | 55.99 | |
RJ | 19.43 | 1.32 | 3.36 |
表8 青稞纤维结晶度的方差分析Tab.8 Analysis of variance on the crystallinity of highland barley fibers |
因素 | III类平方和 | 自由度 | 均方 | F | F 临界值 | 显著性 |
---|---|---|---|---|---|---|
预处理 溶液 | 574.969 | 2 | 287.485 | 4 545.610 | 99 | 非常 显著 |
预处理 时间 | 2.768 | 2 | 1.384 | 21.887 | 99 | 不显著 |
热处理 温度 | 18.662 | 2 | 9.331 | 147.537 | 99 | 显著 |
误差 | 0.126 | 2 | 0.063 |
表9 纤维成分的特征官能团及振动形式Tab.9 Characteristic functional groups and vibration forms of fiber |
样品编号 | 纤维组分 | 波数/cm-1 | 基团或化学键振动形式 |
---|---|---|---|
1 | 纤维素 | 3 400 | O-H羟基的伸缩振动 |
2 | 2 900 | C-H伸缩振动 | |
3 | 1 161 | C-O-C伸缩振动 | |
4 | 1 058 | C-O伸缩振动 | |
5 | 898 | β-1,4 glycosidic bond | |
6 | 半纤维素 | 3 400 | O-H羟基的伸缩振动 |
7 | 2 900 | C-H伸缩振动 | |
8 | 1 733 | C=O伸缩振动 | |
9 | 1 250 | C-O伸缩振动 | |
10 | 木质素 | 3 400 | O-H羟基的伸缩振动 |
11 | 2 900 | C-H伸缩振动 | |
12 | 1 733 | C=O伸缩振动 | |
13 | 1 600 | 芳香骨架振动 | |
14 | 1 514 | C=C芳环伸缩振动 | |
15 | 1 462 | -CH3、-CH2 变形 | |
16 | 832 | O-H酚羟基 |
表9 纤维增强生态混凝土孔隙率的变化Tab.9 Changes in void ratios of fiber reinforced concrete |
试验组 | 骨料粒径/mm | 水灰比 | 目标孔隙率/% | 有效孔隙率/% | 总孔隙率/% | 有效孔隙率占比/% |
---|---|---|---|---|---|---|
P0 | 10~20 | 0.30 | 25 | 24.75 | 26.23 | 94.36 |
P1 | 19.08 | 21.04 | 90.70 | |||
P2 | 19.82 | 20.74 | 95.55 |
表10 纤维增强混凝土力学性能的变化 (MPa)Tab.10 Changes in mechanical properties of fiber reinforced concrete |
试验组 | 抗压强度 | 劈裂抗拉强度 | 抗折强度 | |||
---|---|---|---|---|---|---|
7 d | 28 d | 7 d | 28 d | 7 d | 28 d | |
P0 | 7.95 | 13.45 | 0.82 | 1.09 | 1.41 | 1.88 |
P1 | 7.19 | 12.39 | 0.87 | 1.15 | 1.69 | 2.22 |
P2 | 7.47 | 12.92 | 0.94 | 1.34 | 1.79 | 2.67 |
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