摘要
使用碱式硫酸镁水泥(BMSC)作为基体材料,制备了树脂透光混凝土(RLTC),并利用界面剪切强度测试、超景深三维显微镜和扫描电镜(SEM)等分析了BMSC基体与树脂的界面黏结性能.结果表明:BMSC与树脂界面处裂纹较少且宽度较窄,在界面处观察到大量针状5·1·7相(5Mg(OH)2·MgSO4·7H2O)结构,微米级5·1·7相晶须填充了BMSC基体与树脂的孔隙,增强了界面间的机械啮合作用;与使用普通硅酸盐水泥的RLTC相比,硬化后BMSC基体与树脂的界面黏结性能明显提高,其中28 d界面剪切强度提高了59.2%.
树脂透光混凝土(RLTC)具备轻质、低能耗的特
为改善水泥基体与树脂界面黏结力较弱的问题,学者们进行了多方面的研究,包括使用硫铝酸盐水
碱式硫酸镁水泥(BMSC)具有高强、轻质及加工装饰性能较好等特
轻烧氧化镁粉(LBM):辽宁海城生产,α‑MgO含
MgO | Al2O3 | SiO2 | Fe2O3 | CaO | f‑CaO | Other |
---|---|---|---|---|---|---|
85.42 | 0.17 | 4.96 | 0.29 | 1.40 | 0.73 | 7.03 |
MgO | SO3 | Al2O3 | CaO | SiO2 | Na2O | Other |
---|---|---|---|---|---|---|
27.43 | 72.05 | 0.06 | 0.20 | 0.18 | 0.06 | 0.02 |
Material | SiO2 | Al2O3 | CaO | Fe2O3 | MgO | SO3 | Other | IL |
---|---|---|---|---|---|---|---|---|
CFBCA | 46.28 | 12.57 | 16.15 | 13.76 | 0.21 | 4.32 | 2.41 | 4.30 |
Sand | 98.10 | 0.50 | 0.69 | 0.17 | 0.54 |
BMSC砂浆按照相当强度的PO砂浆进行配置,BMSC与PO砂浆的配合比分别见表
LBM | MgSO4· 7H2O | Water | CA | CFBCA | Water reducer | S2 | S1 |
---|---|---|---|---|---|---|---|
800.00 | 248.00 | 272.00 | 8.00 | 120.00 | 6.08 | 508.00 | 127.20 |
P·O42.5 | FA | Water | Water reducer | S1 |
---|---|---|---|---|
900 | 270 | 351 | 9 | 1 700 |
PO砂浆的制备过程如下:将水泥、粉煤灰倒入搅拌锅中,再加入混合好的水和减水剂,先慢搅30 s,再加砂,继续慢搅30 s,然后快搅60 s;其试件成型过程与BMSC砂浆相同.
在制备RLTC时,树脂掺入方式与纤维混凝土相似,界面黏结性能在很大程度上决定了非均相系统的一系列性
本文通过拉拔试验来测试树脂与水泥基体的界面剪切强度,如

图1 拉拔试验示意图
Fig.1 Schematic diagram of pull‑out test
进行拉拔试验时使用内径大于10 mm的延长套杆将树脂导光体牢固固定,分别固定套杆和水泥基体,使用CMT5105万能试验机进行拉拔试验,加载速率为0.5 mm/min.记录树脂导光体与水泥砂浆发生滑动位移时的拉力,作为最大拔出荷载.并计算界面剪切强度,计算方法如
(1) |
式中:Fm为最大拔出载荷,N;L为水泥基体中树脂埋入长度,mm;μf为树脂横截面周长,mm.
取破坏前后的RLTC,用洗耳球吹去样品表面沙砾后,使用基恩士VHX‑5000型超景深三维显微系统进行超景深显微分析,利用变焦镜头,全幅对焦,在500倍范围内观察,拍摄后使用配套REMAX V软件进行3D图像处理.
将未破坏的RLTC切割成小块,利用金相研磨抛光机将试块表面打磨平整后,喷金,采用TM‑4000型扫描电镜(SEM)对样品进行微观形貌分析,观察RLTC中树脂与水泥砂浆界面黏结情况.
测试BMSC和PO基体与树脂的最大拔出荷载,结果见
Specimen | 3 d | 7 d | 28 d |
---|---|---|---|
BMSC‑RLTC | 85.62 | 285.85 | 616.86 |
PO‑RLTC | 262.10 | 654.74 | 983.90 |
根据

图2 树脂与不同水泥基体间的界面剪切强度
Fig.2 Interfacial shear strength between resin and different cement matrices

图3 2种水泥基体的抗压强度及强度发展规律
Fig.3 Compressive strength and strength development law of two cement matrices

图4 BMSC与PO基体制备的RLTC的表观与破坏形貌
Fig.4 Surface appearance and failure morphology of RLTC prepared with BMSC and PO matrices
破坏前RLTC中树脂与水泥基体界面的SEM照片见

图5 破坏前树脂与水泥基体界面的SEM照片
Fig.5 SEM images of interface between resin and cement matrix before destruction

图6 破坏前后树脂和水泥基体界面的超景深三维显微镜图像
Fig.6 Ultra‑deep 3D microscopic images of interface between resin and cement matrix before and after destruction

图7 树脂与水泥基体界面水化产物的SEM照片
Fig.7 SEM images of hydration product in interface between resin and cement matrix
本文建立了水泥基体与树脂界面黏结模型,如

图8 水泥基体与树脂界面黏结模型
Fig.8 Interface bonding model between cement matrix and resin
BMSC基体与树脂界面的受力示意图如

图9 BMSC基体与树脂界面的受力示意图
Fig.9 Schematic diagram of interface bonding force between BMSC matrix and resin
(1)与PO基体相比,BMSC基体与树脂的界面黏结性能更强.BMSC‑RLTC与PO‑RLTC的界面剪切强度均随龄期增加而增加,但BMSC‑RLTC的3、7、28 d界面剪切强度均高于PO‑RLTC,其中28 d界面剪切强度比PO‑RLTC高59.2%.BMSC基体在整个龄期内都表现出比PO基体更好的界面黏结性能.
(2)在微观形貌上,BMSC基体与树脂的界面比PO基体更紧密,裂纹更少,裂纹宽度更窄.同时BMSC水化生成的5·1·7相晶须能有效增强水泥基体与树脂界面的机械啮合作用,进一步提高界面黏结性能.微米级5·1·7相晶须填充了BMSC基体与树脂的孔隙,使界面结构更致密,增加了黏结强度.
(3)5·1·7相晶须能够较好地在BMSC基体与树脂界面处生长,使BMSC基体与树脂结合更加致密,提高界面黏结性能,并在微观尺度上抑制裂纹的产生和发展,从而有助于提高树脂透光混凝土的力学性能和耐久性.
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