The self-healing phenomenon in cement concrete was first observed from a bridge in the 18th century in Amsterdam[1].In the past decades, many researchers conducted much work on the self-healing behavior of cement materials[2-6].There are two mechanisms to promote the formation of self-healing products filled in cracks.On one hand, under high humidity conditions, the continued hydration of unhydrated cement and the second reaction of fly ash at crack surface contribute to produce new healing products, thus sealing the crack space[7].On the other hand, when the crack space is filled fully by water, the ions of Ca2+ from the inside of the concrete will react with water and CO2 from air, leading to the precipitation of calcium carbonate (CaCO3), resulting in the blocking of cracks[1,8].

全国职业院校导游技能大赛已经连续举办了8年，赛项的设置越来越科学合理，真正地展示了职业院校学生的导游职业技能和综合素养。通过对参赛方案的解读和对第三届全国导游大赛视频的研读，总结出了几点现场导游词的创作技巧。

Although the continued reaction of cementitious materials and precipitation of CaCO3 are likely to contribute to the formation of healing products, its quantity is limited.Previous studies showed that a crack in concrete can be sealed completely when the crack width is less than 50 μm[9-10].Some researchers even suggested that the crack width should be maintained below 30 μm for better healing[10-11].Moreover, most areas of China are dry and a little rainy.Thus, the lack of water is not helpful for self-healing behavior.To attain its self-healing potential, it calls for the cementitious materials featuring a good crack width control capacity and automatic water absorption capacity.

Engineered cementitious composite (ECC)was developed based on the micromechanic design theory by Li in 1990s, featuring a high tensile strain capacity of 3% to 5% (300 to 500 times that of normal concrete), possessing the self-control of crack open width within micrometer level (typically below 60 μm)[12].With the above characteristics, ECC is expected to have a better self-healing capacity after cracking.

Qian et al.[13] studied the recovery of ECC bending capacity, showing that the bending capacity of pre-cracked ECC submerged in water can recover 65% to 105% compared to virgin specimens.Yang et al.[7] studied the effect of wet-dry cycles on the self-healing of ECC, indicating that the initial resonant frequency value of pre-cracked ECC can recover from 76% to 100% and the tensile strain capacity can also recover from 0.8% to 3.1% under self-healing cycles.Snoeck et al.[14] analyzed the visualization of water penetration in the cracks of concrete by means of self-healing, and a regain of 50% in mechanical properties was achieved.Without water, cracks in ECC will not show self-healing.Therefore, this paper considers adding superabsorbent polymers (SAPs)into ECC to improve the self-healing capacity.

作为一级指标(领域指标)的“知识系统”，它是集浅层文化知识和深层文化知识，无论哪种文化知识作为教师的跨文化能力的一种“外在能力”，相对都比较容易习得和培养。在这个指标设计中，特别把“中医药文化理解力”作为深层文化知识的一部分，主要是要突出作为中医药高校的外语教师，除了外语教学之外，由于面对的教学对象以及科研领域的不同，掌握一定的中医药文化知识，提高对中医药文化的理解力就成为中医药高校外语教师与其他类型高校外语教师的最大区别之一。

SAP is a type of water-retain material, which can absorb much water from the surrounding environment up to 500 times that of its own weight[14-16].Generally, SAP particles were used for reducing shrinkage and internal curing, which benefited the increase of strength during the later stage.Yao et al.[17] found that ECC incorporating SAP particles could enhance its deformability, meanwhile reducing the shrinkage.Craeye et al.[18] studied SAP particles as an internal curing agent, showing that by absorbing water from the surroundings, the release of water from SAP particles is available for healing, and SAP particles are helpful for the internal healing of a crack.

In this paper, the effects of incorporating SAP particles in ECC on its flexural properties and self-healing behavior are investigated.Three different SAP dosages in ECC are adopted to evaluate the differences in mechanical properties by compressive strength tests and four-point bending tests.The cracked ECC’s self-healing behavior under three different curing conditions (95% RH/room air cycle, exposed in air and high relative humidity)are investigated via water flow tests and bending mechanical properties’ recovery.The flexural properties include flexural strength, flexural deformation and flexural stiffness.

To investigate the self-healing behavior in ECC, three different exposure curing conditions were used in this study, as shown in the following:

1　Experimental Programs

1.1　Materials and mixture proportions

In this study, the raw material includes cement, fly ash, silica sand with particles passing seizes between 70# and 140#, water, polyvinyl-alcohol (PVA)fibers, SAP particles with a size of 550 μm, and a polycarboxylate-based high range water reducer (HRWR).The content of SAP particles in ECC mixtures is 2% and 4% by weight of cement.PVA fiber supplied by Kuraray Company was added, whose length and oil coating by weight are 12 mm and 1.2%, respectively.The mechanical and geometrical properties of PVA fibers are shown in Tab.1.

Tab.1　Properties of PVA fiber

Length/mmDiameter/μmTensilestrength/MPaYoung smodulus/GPaDensity/(g·cm-3)Elongation/%1239162042．81．27

To investigate the influence of self-healing on the mechanical property of ECC incorporating SAP particles, four ECC mixtures with a constant water to binder ratio (W/B)of 0.25 and fly ash to cement ratio (FA/C)of 1.5 are adopted in this study.The mix proportion of different ECCs is listed in Tab.2.The variable parameters in ECC are the content of SAP particles (2% and 4%).For this purpose, the control ECC mixture was produced first.

在九头山汉墓中，出土了40多枚汉武帝和汉宣帝五铢钱，同时还出土了琉璃饰品，据考证可能来自东南亚或印度东海岸，从合浦登陆，经南流江、北流江西上柳江进口。这也证明了柳江早在汉朝时期便为柳州提供了航运便利和商贸通道。

1.2　Specimen preparation and experimental tests

All ECC mixtures were mixed in a standard mixer.All solid ingredients including cement, fly ash, sand and SAP particles were first mixed for 2 min thoroughly.Water and HRWR were then added and mixed for another 2 min.PVA fibers were added at a low speed, followed by high speed mixing until all fibers were uniformly distributed.All ECC specimens were demolded after 24 h, and cured in a standard curing room where the temperature and relative humidity (RH)were (20±2)℃ and (90±5)% until testing ages.

Tab.2　Mix proportion of ECC mixtures　kg/m3

MixtureCementFASandWaterSAPHRWRFiberW/BECC1509763462311010260．25ECC250976346231110．210260．25ECC350976346231120．410260．25

对逆变器与DC/DC的级联系统建立MATLAB/Simulink仿真模型，其中电感值设置为4 mH，电容值设置为8 000 μF，内阻0.044 Ω，电池侧直流电压为1 100 V，直流环节侧的期望电压设置为1 500 V。

陶氏化学公司高性能有机硅业务部在“2018国际新型显示技术展”上展出其在压敏胶行业的最新技术成果。陶氏此次展示的主题为“善于创新，可靠稳定”，产品包括 SYL-OFFTM与陶熙TM品牌系列产品。陶氏创新技术和产品将助力中国客户提升产品性能、可持续性及成本效益，从而在快速增长的行业中赢得竞争优势，实现自身发展并引领行业未来趋势。此次展会于2018年6月27日至29日在上海新国际博览中心举行，陶氏展位号为E7展厅5C22。

1)CR1 (95% RH/room air cycle): Pre-cracked ECC specimens were stored under a 95% RH curing condition at 20 ℃ for 24 h, and then cured in room air at (20±1)℃, (50±5)% for 24h.The cycle then repeats itself until a pre-determined testing age.

2)CR2 (95% RH): Pre-cracked ECC specimens were stored under a 95% RH curing condition at 20 ℃ for 48 h.

3)CR3 (room air): Pre-cracked ECC specimens were exposed to room air conditions at (20±1)℃, (50±5)% for 48 h.

The change of water permeability with the number of curing cycles is shown in Fig.6.The relative permeability values on the y-axis represent the weight percentage of the permeated water from the cracks of the specimen after self-healing.The relative permeability is 1, indicating that the pre-cracked specimen has undergone no healing.

他们收获的大部分是冷杉和雪松，然后出售给一个合作社，扣除总价值的一部分返还给伐木公司后，每根原木哈蒙德和摩尔可得25美元的收入，两人平分。除了从伐木公司流出到海上的原木之外，他们还在海上搜寻未经砍伐自然倒下的原始树木，这些树木通过风雨侵蚀或洪水冲刷最终进入海里，由于它们不属于伐木公司所有，可以卖出更高的价钱。他们说，最好的海上拾荒时间是在秋季和冬季，海水涨潮加上强烈的暴风雨，会有更多的原木和倒下的树木进入暴涨的河流水系中然后流向大海。

The typical flexural stress-displacement curves of different ECC at 28 d are given in Fig.4.Fig.4 shows the effect of SAP particles on the flexural behavior of all, ECC specimens.The typical flexural behavior of coupon specimens after FPBT is shown in Fig.5.As seen from Fig.5(a), similar to ductile metal plates, ECC specimens have a better plastic deformation.As shown in Fig.4, SAP particles can reduce the flexural strength of ECC mixtures.Meanwhile, flexural deformation, which can reflect the ductility and toughness of the ECC material, strongly depends on the SAP content.The flexural deformation of ECC at peak load increases from 21.7 mm to 26.2 mm, with the SAP content changing from 0% to 4%.Compared to ECC1, the flexural deformation of ECC2 and ECC3 increases by 11% and 21%, respectively.Fracture energy and first cracking energy are evaluated by corresponding integral areas under the stress-displacement curve of ECC.A toughness index calculated by fracture energy and first cracking energy indicates the ECC strain-hardening degree.As listed in Tab.4, SAPs can improve the toughness index of ECC.Compared with ECC1, the toughness index of ECC2 and ECC3 increases by 23% and 66%, respectively.The above results indicate that SAP particles can act as artificial flaws to lead cracks to occur easily in the ECC matrix and help the ECC to realize pseudo strain-hardening performance[17].

The influence of pre-loading times on self-healing for the mechanical properties of ECC is shown in Tab.5 and Fig.9.Tab.5 presents four-point flexural test results after ten self-healing cycles from specimens subjected to pre-loaded deformation of 3, 6 and 9 mm, respectively, at the age of 7 and 28 d.It can be seen from Fig.9 that no apparent self-healing occurs in CR3.Similar to Ref.[19], the results in CR3 were considered as no self-healing.As seen from Tab.5, self-healing behavior has a slight effect on the flexural strength of ECC when pre-loaded at 7 d.However, when pre-loaded at 28 d, the flexural strength of specimens containing 4% content of SAPs (ECC3)after self-healing is larger than the case without healing.

Fig.1　ECC specimen pre-cracked by the splitting test

Fig.2　Rapid penetration test instrument

Fig.3　The setup of four-point bending test (unit: mm)

The effect of self-healing can also be seen from the level of flexural stiffness retained after CR1, CR2 and CR3 curing compared with the reference sample, as shown in Fig.8.The flexural stiffness is defined as the scant of the initial slope of the flexural strength-displacement curve when the flexural strength is between 1 and 5 MPa.The flexural stiffness of ECC1 in CR3 indicates the stiffness of the relatively soft bridging fibers.As seen from Fig.8(a), all relative stiffness values in CR1 and CR2 are larger than those in CR3 due to self-healing under these conditions, but the degree of recovery is relatively low.

2　Results and Discussion

2.1　Mechanical properties of ECC

The compressive strength of ECC specimens with different SAP contents at 7, 28 and 90 d, respectively, is displayed in Tab.3.Four 75 mm×75 mm×75 mm cube specimens were used to obtain the average results.From Tab.3, as expected, the compressive strength of ECC specimens at 28 d decreases by about 13% as the SAP content increases from 0% to 4%.However, the compressive strength of ECC with 4% SAP at 28 d is still greater than 40 MPa, satisfying the demand for many infrastructure constructions.The compressive strength of ECC specimens incorporating SAP particles is lower than those of one control ECC specimen (ECC1).With the increase of SAP content, the compressive strength of ECC mixtures can be further decreased.For example, the compressive strength of ECC2 and ECC3 at 28 d reduces by 5% and 13%, respectively, compared to ECC1 at 28 d.

Tab.3　Compressive strength of ECC specimens　MPa

MixtureCompressivestrength7d28d90dECC127．852．460．1ECC222．149．756．9ECC318．545．753．3

To study the healing efficiency in ECC, the water flow test was used in this study.Four specimens with a diameter of 100 mm and a height of 20 mm were prepared in this test.The initial crack was produced by the splitting test at the age of 7 d (see Fig.1).All specimens were cured in CR1 and CR2.The rapid penetration setup is shown in Fig.2.The permeability of each specimen was measured by the rapid penetration test for every healing cycle.In this test, the weight of water permeating via pre-cracked specimen was measured.

It can be seen from Tab.4 that the average crack width decreases in different degrees as the SAP content increases.Meanwhile, compared to ECC1, the number of cracks in ECC2 and ECC3 shows an apparent increase.According to Refs.[6, 16-17], a smaller crack width in ECC can promote self-healing behavior and recover some of the mechanical properties.

3.4.4 秋季降水量各地出现异常的年份有所不同，茶卡、天峻1967年出现了异常偏多，刚察、天峻、茶卡1971年出现了异常偏多现象，天峻、共和1989年出现异常偏多现象。秋季降水量出现异常偏少的年份较少，仅海晏1991年和共和1984年出现。

Fig.4　Typical flexural strength-displacement curves for different ECC

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Fig.5　Response of coupon specimens after FPBT.(a)Bended specimen;(b)Multiple cracks

Tab.4　Mechanical properties of ECC mixtures at 28 d

MechanicalpropertiesECC1ECC2ECC3Flexuralstrength/MPa14．412．511．4Deformation/mm21．724．126．2Firstcrackingenergy/J0．1140．0970．080Fractureenergy/J4．44．75．2Toughnessindex394865Flexuralstiffness/(MPa·mm-1)14．512．99．5Crackwidth/μmMin101010Max807070Ave494235Numberofcracks526482Crackspacing/mm2．91．40．9

2.2　Decrease of water permeability by self-healing

本模块根据水泥生产工艺，从原材料进厂到半成品、成品的生产，对生产过程中的各项技术参数、设备运转情况、设备能耗情况进行记录，并使用数据分析软件对采集到的数据进行分析处理，使水泥生产过程全部实现信息化。分析后的数据对企业的生产调度人员有实际的参考和指导作用，能够直观、规范地体现出全厂的生产状况和资源情况，为其他管理系统提供基础数据。

As seen from Fig.6(a), the relative permeability of specimens under CR1 was faster than that of CR2 approaching 0.It can be summarized that high/low relative humidity curing regimes may be more advantageous to crack self-healing.

As seen from Fig.6(b), the water permeability decrease rate of ECC2 and ECC3 is faster than that of ECC1, with ECC3 being the fastest of all mixtures.It can be explained by the crack width of ECC3 being smaller than that of ECC1, which contributes to self-healing.Moreover, higher swollen SAP content can seal the crack and release water to achieve self-healing.

2.3　Recovery of mechanical properties by self-healing

The flexural strength of mixtures ECC1, ECC2 and ECC3 under different curing conditions and pre-loading displacements is compared in Fig.7.It should be noted that the variations of the flexural strength of ECC1 is very small, whereas that of mixtures containing SAP particles has a great fluctuation for different curing conditions and pre-loading displacements.The flexural strength of ECC2 and ECC3 from CR1 and CR2 curing is larger than that of the reference (no pre-cracked)for the preloading displacement of 3, 6 and 9 mm, due to the continuous hydration of unhydrated cementitious material with the help of SAP particles.

在产出导向法整个教学模式下，教师的角色变化最为巨大，虽然不需要长时间的面对面讲授，但是整个课堂节奏性的把握，以及输入输出的资料仍然是需要教师准备的，因为即使是以学生为主体的课程教学，但也仅限于学生学习的这个过程，并不是包括整个教学体系的构建，毕竟学生还是学生，只有任务输出才是完全由学生自我主导的。教师会在整个课堂教学中对于学生的学习掌握能力有更深刻地认识，为了更好地提高学生对大学英语的学习，在输入资料的准备上也可以进行特殊的设置。毕竟，总体目标是要培养学生语言综合运用能力，那么听说读写缺一不可。

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Fig.6　Changes of water permeability with number of environmental conditioning cycles.(a)ECC1 for different exposure regimes; (b)Different ECC mixtures under CR1

ESEM and DES tests were used to study the change of a crack in the self-healing process of ECC and observe the chemical components of the healing product.After being preloaded at the age of 7 d, bending specimens containing a crack width of 30 μm were cut into 5 mm×5 mm×5 mm cubic samples.In these tests, three different points were analyzed by EDS for each sample.

Figs.8(b)and (c)show the relative flexural stiffness of healed ECC2 and ECC3 specimens to the reference specimens (no pre-cracked).As seen from Figs.8(b)and (c), the level of relative flexural stiffness retained after CR1, CR2 and CR3 increases with the content of SAP particles in ECC mixtures due to the presence of SAPs in cementitious materials for continuous hydration.It may be also explained that SAPs manage to take moisture out of a humid environment and provide it to the cemetitious matrix for crack self-healing.The flexural stiffness in CR1 curing is much higher compared with that in CR2 and CR3 curing .This curing condition can effectively help SAPs promote the interaction of water, CO2 and remaining unhydrated cement particles in ECC materials (including matrix and fiber-matrix interface), therefore resulting in the best recovery of flexural stiffness.Moreover, the greater the content of SAP particles, the better the recovery from flexural stiffness.The general trend shows that specimens containing a higher SAPs content, with lower pre-load levels, tend to have higher flexural stiffness recovery.This is because a larger number of cracks and greater crack width at higher pre-load levels can lead to reduction of flexural stiffness recovery.

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Fig.7　Comparison of flexural strength of the mixture for different curing conditions and pre-loading displacements: (a)ECC1; (b)ECC2; (c)ECC3

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Fig.8　Comparison of normalized stiffness of the mixture for different curing conditions and pre-loading displacements.(a)ECC1; (b)ECC2; (c)ECC3

To study the effect of self-healing on the flexural properties of ECC, the four-point bending test (FPBT)was adopted.FPBT was performed on a universal testing machine (UTM)under displacement control at a loading rate of 1.0 mm/min.The span length of FPBT setup was 300 mm (see Fig.3).The dimension of specimens was 400 mm×70 mm ×10 mm.All bending specimens were pre-loaded up to a deflection of 3, 6 and 9 mm, respectively, at the age of 28 d.Then, these pre-cracked specimens were cured for ten curing cycles (CR1, CR2 and CR3).With the continuous hydration of matrix, the flexural properties were enhanced.Finally, to evaluate the healing effect on the residual mechanical properties of ECC after self-healing, all pre-cracked specimens were reloaded under FPBT.

The deflection (deformation)capacity is a major concern for ECC material since its structural applications mainly require high ductility.Fig.9 shows the influence of different pre-loading time and pre-loading levels on the normalized deflection capacity of different mixtures.The normalized deflection capacity is defined as the percentage of the displacement of the healed or non-healed specimens to that of reference case (no pre-cracked).As seen from Fig.9(a), when pre-loaded at 7 d, the remaining deflection capacity of pre-loaded ECC1 specimens (without SAPs)after self-healing and non-self-healing are only about 52% to 74% and 27% to 71%, respectively.A similar deflection capacity is retained in the ECC1 specimens when pre-loaded at 28 d, which may be related to a larger proportion of elastic fiber stretch within the pre-loading deformation since fiber/matrix interface micromechanical performance is enhanced with age, or there is not enough self-healing products inside the crack after self-healing.These results indicate that the ECC specimens without SAPs cannot achieve complete self-healing.

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Fig.9　Influence of different pre-loading time and pre-loading level on normalized deflection capacity of mixture.(a)ECC1; (b)ECC2; (c)ECC3

Figs.9 (b)and (c)show the comparison of the normalized deflection capacity of mixture ECC2 and ECC3 for different pre-loading times and pre-loading levels.As seen from Figs.9 (b)and (c), a larger deflection capacity is retained in the specimens with SAPs after self-healing when pre-loaded at 7 and 28 d compared with ECC1 specimens (without SAPs).It may be explained that SAPs can absorb fluids from the surroundings and swell and block cracks, which contributes to the internal healing/curing.Meanwhile, increasing the content of SAPs can enhance healing due to more internal curing.Ma et al.[19] found that the deflection capacity recovered best after self-healing at 7 d and it was minimal when pre-loaded at 28 d.However, it can be seen from Fig.9 that the samples containing higher content SAPs after self-healing when pre-loaded at 7 and 28 d can both reach about 93% to 102% and 91% to 105% of the deflection capacity of the reference samples.The recovery level is significantly higher than that of ECC1 in Fig.9(a).These results indicate that good self-healing behavior of ECC materials has been achieved at an early age, thus improving the durability of concrete.

Tab.5　Flexural properties of ECC specimens with different pre-loading times

MixturePre⁃loadingtime/dPre⁃loadingdeflection/mmFlexuralstrength/MPaFlexuraldisplacement/mmSelf⁃healingNoself⁃healingSelf⁃healingNoself⁃healingECC1728311．010．014．36．2612．17．812．111．7911．18．017．116．5310．610．211．67．8610．28．915．97．5910．59．815．78．2ECC2728311．89．526．410．1613．39．322．88．0910．08．214．68．1312．19．620．09．5611．48．321．97．7911．611．224．413．4ECC3728312．39．027．418．3612．98．526．417．2914．68．225．117．9313．412．527．520．0613．311．825．417．1912．612．223．913．8

Fig.10 shows the normalized stiffness of healed/non-healed ECC specimens with respect to that of the reference case (condition A)for different pre-loading times.As seen from these figures, the stiffness of pre-loaded specimens without self-healing is always smaller than that of the healed ones, but the gap decreases with the increase of pre-cracking level.Furthermore, Fig.10 shows that there are stable increase stiffness gains when comparing healed and non-healed specimens with the increase of the content of SAPs.In comparison, due to crack self-healing by the release of water from SAP particles, a significant recovery of stiffness has been accomplished in ECC3 specimens, which were pre-loaded at 7 d and then cured in CR1 for 10 cycles.In the case of pre-loading to the deformation of 3, 6 and 9 mm, the stiffness of ECC3 can also recover 80%.When pre-loading to the deformation of 3 mm at 28 d, the flexural stiffness recovery level is 60%, beyond the case of specimens without SAPs.

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Fig.10　Influence of different pre-loading time and pre-loading deflection on flexural stiffness of healed/non healed specimens.(a)ECC1; (b)ECC2; (c)ECC3

2.4　Microstructure of self-healed ECC

From Fig.11, it can be clearly seen that a large number of self-healing products displays along crack lines.As seen in Fig.12(b), an abundant of stone-like healed products were filled in all cracks of ECC1 after 3 cycles.Especially in ECC3, more self-healing products were precipitated in cracks, and the cracks were almost healed completely (see Fig.12(e)).However, this completely healed phenomenon occurring in ECC1 needs ten curing cycles.The microscopical observations indicate that self-healing of ECC mainly occurs in the first three CR1 cycles, in which the cracks can be healed up to about 80% even 100%.All indications show that SAP particles can accelerate the self-healing of ECC materials.

Fig.11　Self-healing of crack-damaged ECC after ten cycles under CR1

Fig.13 and Tab.6 show the ESEM close-up view and EDS analysis results of products in the self-healed cracks of ECC specimens.Based on Tab.6, the mass ratio of Ca to Si increases rapidly with the increase of self-healing cycles.It can be explained that the C-S-H is the main healing product due to its continuous hydration.The change of mass ratio of O to Ca and C to Ca indicates that the CaCO3 content increases in the healed products of cracks.

3　Conclusions

1)Incorporating SAP particles as pre-existing flaws can improve the flexural deformation capacity of ECC specimens.The flexural deformation of specimens in ECC2 and ECC3 at 28 d increases by 11% and 21%, respectively, compared to ECC1.Meanwhile, SAP particles reduce the crack width of ECC specimens, which can improve the durability of ECC.

2)The water permeability of pre-cracked specimens decreases rapidly after 3 or 4 cycles due to self-healing.Compared with ECC1, faster self-healing behaviors were observed in the specimens of ECC3 cured in high/low humidity cycles, because swollen SAP particles release water and help the formation of CaCO3 with abundant availability of CO2 in the air.

3)Different degrees of recovery of mechanical properties due to self-healing were found in this study, including flexural strength, flexural stiffness and deformation capacity.Similar to water permeability, a better recovery of mechanical properties after self-healing was achieved when the SAP content was 4% (ECC3).The lower pre-damaged level it makes, the better mechanical recovery it achieves.

3组患者主要不良反应为骨髓抑制、胃肠道反应和贫血。3组患者中性粒细胞减少均以Ⅰ～Ⅱ级为主。发生恶心呕吐患者的严重程度等级区分并不明显，划分为Ⅰ～Ⅱ以及Ⅲ～Ⅳ级的患者大约各占50%；贫血发生的严重程度均以Ⅰ～Ⅱ级为主。见表4。

4)The self-healing process of ECC mainly occurs in first three CR1 cycles, and the self-healing product is a mixed Ca(OH)2/CaCO3, with CaCO3 being a major component at a later age due to the participation of CO2 in the air.

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Fig.12　Microscopical observation of self-healing process for ECC with 30 μm crack width.(a)0 cycle of ECC1; (b)3 cycles of ECC1; (c)10 cycles of ECC1; (d)0 cycle of ECC3; (e)3 cycles of ECC3

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(b)

Fig.13　ESEM micrograph and EDS analysis of self-healing products for ECC.(a)ESEM; (b)EDS

Tab.6　EDS analysis results for self-healing products of ECC

MixtureSelf⁃healingcyclesAtompercent/%COSiCaWeightratioofCatoSiWeightratioofOtoCaWeightratioofCtoCaECC103741980．95．14．6328502199．52．61．51034480．517342．82．0ECC203246891．15．13．632346129291．60．81029460．424601．91．2ECC3027491290．75．43．0330502178．52．91．8

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