Mechanical properties of calcium carbonate whisker-reinforced high-strength cement mortar

In order to improve the brittleness of high-strength cement mortar,calcium carbonate（CaCO3） whiskers are incorporated to strengthen and toughen the high-strength cement mortar.The compressive strength,flexural strength,split tensile strength and work of fracture are measured.Microstructures and micromechanical behaviors are investigated using scanning electron microscopy.The strengthening and toughening mechanisms and the efficiency of whisker-reinforced high-strength cement mortar are discussed.The results show that the addition of CaCO3 whiskers brings positive effects on the high-strength cement mortar.The strengthening and toughening mechanisms are whisker-cement coalition debonding,whisker peeling,whisker impact breakage and whisker bridging.Crack deflection is one efficient mechanism,but it is hard to be achieved in high-strength cement mortar.And the interfacial bonding strength between whiskers and the cement mortar matrix should be appropriately weak to introduce more crack deflection mechanisms to strengthen and toughen the cement mortar efficiently.

The Properties of Cement Mortars Modified by Emulsified Epoxy and Micro-fine Slag

The epoxy resin polymer cement mortars with excellent performances were made up through modifying ordinary Portland cement with emulsified epoxy and micro fine slag.The microstructure of the epoxy resin polymer cement materials was studied and their hydration and hardening characteristics were discussed by means of modern analysis measures such as SEM,XRD and Hg intrusion micromeritics.The experimental results indicate that the series effects of water reducing,density,pozzolanicity,filling and solidification crosslinking through the action together with epoxy organism and micro fine slag endowed cement based materials with perfect performances.The main hydration products in the system are C S H gel and hydrated calcium aluminate.At later age,AFt can be in existence,and no Ca(OH) 2 is found.When epoxy resin is solidified,the organism is in a network structure.In the micro pore structure of hydrated cement with modified epoxy and fine slag,big harmful pores were fewer,more harmless abundant micro pores were and the possible pore radius was smaller than that of ordinary Portland cement.

Behavior of Corrosion-Repaired Concrete Beams Reinforced by Epoxy Mortar

The performance of concrete beams repaired with epoxy mortar was investigated by constructing twelve beam specimens.All the beam specimens were subjected to a constant current for accelerated corrosion.Six specimens were corroded without subsequent reparation as a control group,and the other six beam specimens were corroded and repaired utilizing epoxy mortar.All specimens were tested to failure.During test process,we focused on the failure pattern of beam specimens,structural cracks,mid-deflections,bearing capacity,and probed into the influence of corrosion degree and repair of epoxy mortar on the performance of beam specimens.It was observed that corrosion-repaired beams in the loading test were in a bending failure pattern.It is obvious that cracking loads and bending stiffness of repaired beams and corrosion-repaired beams were larger than those of unrepaired beams and secondly-corroded beams.When the mass loss of main steel bars was smaller than 10%,the bearing capacity of the repaired beams was similar to that of the unrepaired beams.When the mass loss of main steel bars was larger than 10%,the bearing capacity of the repaired beams increased significantly compared with that of the unrepaired beams.

Preparation and Properties of a New Composite of Epoxy Emulsion (EEM) Modified Cement

High performance cement based composite materials was prepared by adding epoxy emulsion. The epoxy emulsion was synthesized with epoxy phosphoric acid ester and poly-glycol in laboratory. This epoxy emulsion has advantages over other emulsion, such as dehydrated slightly, and well film formation abilities. The mechanical properties, corruptness resistance and structure of ep-oxy emulsion modified cement mortars were studied. Experimental results show that the mechanical properties of modified cement mortars are slightly increased with increasing epoxy emulsion content, especially the flexure strength. The corruptness resistance of all modified mortars is better than the unmodified mortar. The polymer film forms the bridge phases between the matrix and the aggregate regions, and forms a three-dimension structure in the cement hydration system , which improves the mechanical properties of modified mortars.

Performance of Epoxy-Repaired Corroded Reinforced Concrete Beams

Reinforcement corrosion has a serious impact on the durability and safety of reinforced concrete structures.Six reinforced concrete(RC)beam specimens are constructed.After beam specimens are subjected to accelerated corrosion with the constant current,beam specimens are repaired with epoxy mortar and the flexural test of beams is investigated.Then the behaviors of repaired corroded reinforced concrete beams are evaluated.The experimental results show that cracking and ultimate loads of corroded RC beams are enhanced after being repaired.And the strain distributions measured across sections of beam specimens still obey the assumption of plane section.After being repaired,the number of cracks decreases and the crack spacing increases.

水性环氧树脂-聚丙烯纤维改性水泥基快速修补砂浆性能研究

为改善机场道面修补砂浆脆性大和粘结性能差等问题,本文利用水性环氧树脂(WER)、聚丙烯(PP)纤维和硫铝酸盐水泥(SAC)制备出一种快速修补砂浆,并对其工作性能、力学性能、阻尼性能和耐硫酸盐腐蚀性能进行研究。结果表明,PP纤维和WER可显著提高快速修补砂浆韧性和粘结性能,使得快速修补砂浆2 h抗压、抗折强度和粘结强度分别达到22.3,5.1和3.7MPa,满足民用机场规范要求,同时可改善快速修补砂浆的阻尼性能和抗硫酸盐侵蚀性能。

高寒地区水工建筑物环氧砂浆防护材料耐候性能及工程应用

高寒地区水工建筑物长期暴露在高海拔、强紫外辐射、冬季严寒且温差大等特殊环境下,较其他地区更易产生裂缝、渗漏破坏,以及冻融破坏、溶蚀、碳化、钢筋锈蚀、冲刷破坏等劣化问题,严重影响工程安全运行。通过室内紫外湿热老化、冻融循环,以及西藏地区自然老化等试验,研究了环氧砂浆的耐候性能。结果表明,改性环氧砂浆紫外线与湿热加速老化2000 h均未出现开裂,且抗拉强度保留率74%;抗冻等级可达到F250;自然老化960 d后,涂层颜色轻微变色,表面不粉化。该材料用于西藏拉洛水利枢纽工程泄洪洞消力池表面防护与修复,经过4 a以上服役,改性环氧砂浆抗冻、耐紫外线等耐候性能表现优异,有良好应用潜力,可为高寒地区类似工程应用提供参考。

低温养护对环氧树脂基砂浆早期性能的影响及机理

环氧树脂基砂浆是一种快速修补材料,为研究低温养护条件对环氧树脂基砂浆工作性能及早期力学性能的影响,构建了全过程低温环境,分别进行了抗压强度、抗折强度、流动度、凝结时间以及内部温度测试,分析了环氧树脂基砂浆的微观结构。结果表明:环氧树脂基砂浆性能受养护温度影响较大,当养护温度为0℃时,流动度仅为112 mm,但随着温度升高流动度增长较快;低温养护使得砂浆内部热效应减弱,延缓了凝结时间;早期强度也损失显著,0℃时,砂浆养护1 d才形成强度,说明低温环境大大减慢了体系的固化速度。微观分析表明低温养护导致砂浆内部结构疏松,裂缝及孔隙增多,说明固化反应不完全,从而降低了砂浆的性能。当养护温度为20℃时,砂浆内部结构较为致密,宏观结构也表现出较高强度。

低水温下大流动性环氧树脂水下修补砂浆的制备

水电站泄水建筑物水下修补施工对环氧树脂修补砂浆的流动性有更高要求,特别是低水温环境下仍然具有大流动性、可以自流平。选用Dinger-Funk方程优化填料粒径分布,优选粒径分布指数为0.4、紧密堆积空隙率仅0.251%的填料,将环氧树脂砂浆流动度提高到18.3 cm;增加稀释剂用量,由20份增加到40份,5℃下环氧树脂基液黏度显著降低73%,砂浆流动度由13.5 cm提高到17.0 cm;为了抵消稀释剂掺量增加和低温所导致的砂浆强度降低,添加30份三环氧官能团树脂增加树脂基液活性,5℃下砂浆的28 d水下粘结强度和抗压强度分别为2.9 MPa、88 MPa,相比未添加的分别提高142%、115%。

高温养护条件下环氧树脂基砂浆早期性能研究

环氧树脂材料具有一定的温度敏感性,因此探究养护温度对环氧树脂基砂浆性能的影响特点十分必要。为进一步明晰高温(30~60℃)养护条件下环氧树脂基砂浆早期物理力学特性的演变规律,对其凝结时间、抗折强度及抗压强度进行了测试,并结合扫描电镜(SEM)及压汞(MIP)技术,分析了环氧树脂基砂浆的微观结构特征。试验结果表明:随着养护温度的升高,环氧树脂基砂浆的凝结时间逐渐缩短,并且凝结时间与养护温度之间大致呈现出线性递减的演变关系。在高温养护条件下,随着温度的升高,环氧树脂基砂浆的早龄期(4 h~3 d)抗折强度及抗压强度均先缓慢增大,再急剧下降。当养护温度为40℃时,环氧树脂基砂浆的强度特性相对最佳,4 h龄期试件的抗折、抗压强度分别达到21.4 MPa和56.8 MPa。在40℃的养护条件下,环氧树脂基砂浆的固化反应较为完全,基体内部结构均匀密实,无明显的孔洞、裂隙等缺陷,而在60℃的养护条件下,环氧树脂基砂浆的固化反应不够充分,基体内部结构松散杂乱,原始缺陷增多。

道路路面免型钢伸缩缝材料与结构

为解决道路路面用毛勒式伸缩缝病害多发现状,提高路面伸缩缝养护维修效率及使用效益,对伸缩缝病害成因及解决方案开展研究。首先,通过足量的现场调研与资料研究,掌握实际路用中不同部位的破坏类别与成因;其次通过对毛勒式伸缩缝结构分析进行设计改进与材料研究,提出用于道路路面的免型钢伸缩缝结构,新型免型钢伸缩缝已应用于湖北省某省道试验段;然后通过力学强度试验、动态单轴压缩试验、高温车辙试验、浸水马歇尔试验、小梁低温弯曲试验和间接拉伸疲劳试验等,综合测试于施工现场取样环氧砂浆混合料试样的力学特性、高温稳定性、水稳定性、低温抗裂性和疲劳耐久性等性能;最后,通过实时位移(缝宽)监测系统对路面的间断式伸缩缝缝宽变化进行监控,获得缝宽同温度的日周期、年周期变化规律。结果表明:随着缝体结构服役年限的增加,病害多发且形式多样,暴露出该结构形式存在缝体脆硬、材料突变、构造分离、应力集中等诸多结构缺陷;环氧砂浆混合料24 h强度可达到28 d龄期强度的70%,具备早强特性,其高温、低温、水稳性能及疲劳性能显著优于同层位沥青混合料;试验段连续配筋路面内部预留缝宽合理,在秋季,缝宽早上7:00最大,晚上20:00最小;CRCP伸缩缝处边缘较中部夏季温度更低缝宽更大;4—5月份、10—11月份为适宜施工的时段,适宜以40 mm预留缝宽施行,低温时节宜增大预留量,高温时节宜减小预留量,调整量以10 mm为宜。

硅烷修饰功能性骨料增韧改性环氧树脂砂浆材料研究与应用

采用硅烷偶联剂KH550改性石英骨料,FTIR结果证实KH550分子结合可在石英颗粒表面。再分别使用石英骨料(QP)和硅烷表面修饰后的石英骨料(TQP)制备环氧树脂复合材料。在粘度曲线中可知填充TQP的混合胶具有更明显的剪切稀化特性。拉伸强度和断裂伸长率特性表明,当填料/树脂增加时,填充TQP的样品具有更高的强度和伸长率保持率。抗压强度测试进一步证实了KH550官能团对体系的积极作用效果。此外,冲击强度随着填料(TQP)/树脂的增加而提高,而随着QP的增加,冲击强度明显降低。在SEM显微照片中,在含有TQP的体系中还可以观察到更多的应力发白现象,表明良好的应力分散效果。将改性后的环氧材料制备成环氧砂浆材料,用于高速公路防撞墙开裂、鼓包、露筋等混凝土缺陷修复,综合应用效果良好。

水工修复技术在公路桥桥墩剥蚀处理中的应用

潘家口水库防汛上坝洒河桥桥墩受推移质冲刷、冻融循环等诸多因素的影响,表层混凝土病害严重,冲坑、脱落情况普遍,粗骨料外露,病害情况日趋严重。本文就桥墩混凝土病害的加固防护处理技术进行分析,介绍了一种常被用于水工建筑物加固防护的缺陷处理技术,该技术原理简单明确,施工灵活,防冲刷、剥蚀效果好,能适用于多种建筑物的修补加固及防护处理中,工程处理取得了良好的效果,其处理技术对类似工程具有良好的借鉴意义,具有很好的应用前景。

双层玻璃纤维网格增强环氧砂浆单面加固砌体墙抗震性能试验研究

为研究双层玻璃纤维网格增强环氧砂浆单面加固砌体墙的抗震性能,对两个高度为1200 mm、宽度为1600 mm、厚度为240 mm的砌体墙进行低周往复试验。试验结果表明:1)双层玻璃纤维网格增强环氧砂浆抗震加固技术切实可行,加固后的墙体破坏形态由脆性转为延性;2)加固后能够降低裂缝扩展速率,减小裂缝宽度;3)显著提高了墙体承载力与变形能力,峰值荷载约提高了91.5%,开裂荷载约提高了20.4%,墙体开裂位移提升了20.0%;4)加固墙体的滞回曲线更加饱满优良,可恢复性变形增加,残余变形更小。本文成果可为砌体墙的加固工程提供一定的借鉴与参考。

T/CECS 10362—2024《钢-混组合梁界面用环氧砂浆》标准解读

随着新型工业化建造方式的推进,钢-混组合梁结构工程得到快速发展,钢-混组合梁界面用环氧砂浆作为一种新型复合材料以优异的综合性能而备受关注,并在多项重大工程中得以应用。简要介绍了团体标准T/CECS 10362—2024《钢-混组合梁界面用环氧砂浆》制订的背景和意义、制订过程、主要内容和依据,并详细阐述了该类环氧砂浆各技术指标及对应试验方法的制定原则,有利于该产品的推广和应用。

我国水下修补环氧砂浆的发展现状

我国有很多处于水下环境的建筑物存在着不同程度的损坏情况,环氧砂浆作为一种效果较好的混凝土修补材料,被广泛使用在各类修补工程中。环氧砂浆用于水下修补时,固化后强度、粘结力均要求较高,主要从组分及施工工艺方面介绍水下环氧砂浆的性能及影响因素,并就我国目前在水下修补环氧砂浆方面的发展状况进行综述。

锂渣对水性环氧砂浆性能的影响研究

为了探索锂渣资源化利用的新路径,测试分析了锂渣的物化性能,并研究了锂渣替代率对水性环氧砂浆凝结时间、力学性能、尺寸稳定性的影响。结果表明,锂渣的重金属浸出毒性、放射性符合相关标准要求,且机械研磨可以较好地激发锂渣的火山灰活性;当锂渣替代0~12%水泥时,随着锂渣替代率的增加,水性环氧砂浆的凝结时间不断延长,抗压、抗折及拉伸粘结强度均先提高后降低,收缩率先减小后增大。当锂渣替代率为6%时,水性环氧砂浆的抗压、抗折及拉伸粘结强度分别为58.8、14.3、1.96 MPa,收缩率为0.036%,其力学性能和尺寸稳定性改善最明显。

抗冲磨水性环氧树脂砂浆设计与试验

水性环氧树脂砂浆具有潮湿环境施工便捷、环境友好等优点,但是力学性能较低,在水工建筑恶劣冲磨防护方面几乎没有实际应用案例。制备了一种新型水乳水溶混合型环氧树脂,兼具了水乳型环氧和水溶型环氧的优点。优化设计了抗冲磨水性环氧树脂砂浆配比,并进行了性能测试。室内试验表明:潮湿面黏接强度超过3MPa,且均非界面破坏;水性环氧砂浆抗压强度均高于80MPa,满足抗冲磨技术要求。现场试验也表明其抗冲磨效果和油性环氧树脂砂浆相当,其综合性能更加优异。因此,该新型水性环氧树脂突破了力学性能提升的技术瓶颈,具备了对传统油性防护砂浆更新换代的能力。

孤河水库混凝土裂缝及老化层处理措施

建筑物混凝土裂缝及表面老化是一种常见病害,若不加以治理,轻则缩短使用寿命,重则影响结构安全。本文以孤河水库泄水闸及出库输水洞为例,介绍了混凝土裂缝和老化病害的处理方法。采用了改性环氧材料进行化灌处理,减缓钢筋锈蚀,对混凝土补强修复;利用丙乳砂浆的优异性能,制定针对性的处理工艺,对表层混凝土老化及钢筋裸露进行了封闭处理。

原材料配比对环氧树脂砂浆性能的影响

研究了固化剂掺量、稀释剂掺量和石英砂填料掺量对环氧树脂砂浆的工作性能和力学性能的影响规律。结果表明:固化剂和稀释剂对环氧树脂砂浆的性能影响最为显著,其次是石英砂填料,固化剂、稀释剂、填料均对环氧树脂砂浆得流动度较大影响,可将环氧树脂砂浆得流动度在146~205mm之间变化。固化剂和稀释剂对凝结时间影响最为显著,填料影响次之,凝结时间可在143~285min之间变化。使用30份固化剂、15份稀释剂和20%填料掺量环氧树脂砂浆具有最好的力学性能,1d抗压强度和抗折强度能达到82.3MPa和23.9MPa。