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Preparation of Ultra-High Performance Concrete with common technology and materials

Preparation of Ultra-High Performance Concrete with common technology and materials
Preparation of Ultra-High Performance Concrete with common technology and materials

Preparation of Ultra-High Performance Concrete with common technology and materials

Chong Wang ?,Changhui Yang,Fang Liu,Chaojun Wan,Xincheng Pu

College of Materials Science and Engineering,Chongqing University,400045Chongqing,China

a r t i c l e i n f o Article history:

Received 8August 2010

Received in revised form 19October 2011Accepted 14November 2011Available online xxxx

Keywords:

Ultra-High Performance Concrete (UHPC)Preparation

Common technology and materials Workability

a b s t r a c t

The technology development of concrete and demand for high strength construction materials give momentum to the development of Ultra-High Performance Concrete (UHPC).Current UHPC preparation methods require costly materials and relatively sophisticated technology.To overcome these weaknesses,this paper focused on the preparation of UHPC with common technology and ordinary raw materials.In?uence of binder content,water/binder ratio,ground granulated blastfurnace slag (GGBS)content,and limestone powder (LP)replacement on ?uidity and compressive strength of concrete were researched,respectively.The test results show that the addition of superplasticizer and ?ne mineral addi-tives enabled the UHPC to be produced at an extremely low water/binder ratio of 0.14–0.18,achieving excellent workability with a maximum slump of 268mm and compressive strengths of 175.8MPa at 90d and 182.9MPa at 365d.

ó2011Elsevier Ltd.All rights reserved.

1.Introduction

The demand for high strength construction materials is the force behind the development of Ultra-High Performance Concrete.Bouygues was the ?rst to start research in Reactive Powder Con-crete,a kind of UHPC from 1990to 1995[1].The pre-stressed hy-brid pedestrian bridge at Sherbrooke in Canada completed in 1997was the ?rst engineering structure application of UHPC [1,2].In 1997and 1998,UHPCs were cast in beams of Cattenom and Civaux power plants as the ?rst industrial application [1].The ?rst UHPC road bridge was designed and constructed at Bourg-lès-Valence in France in 2001[1,3].More recently,Nguyen Viet Tue [4]has re-searched the application possibilities for steel tubes ?lled with UHPC.The preparation and performance of UHPC have been inves-tigated in other literatures [5–8].

Ultra high performance concrete is characterized primarily with high strength,and when it is reinforced with steel ?bers or steel tubes,exhibits high ductility.However,the strength of UHPC is the crux of its preparation,though it must be supported by ductil-ity.For example,RPC,a type of UHPC,is distinguished by its com-pressive strengths ranging between 200MPa and 800MPa after pressure and heat treatment,depending on the mixture propor-tions and the temperature of the heat treatment applied before and during its setting [9];and Ductal ò,a commercial RPC,demon-strates a compressive strength of approximately 150MPa [10].Therefore,how to improve the strength of a UHPC remains a key factor in the development of UHPC preparations.As an initial re-search into the preparation of UHPC with common technology and widely available materials,this research focused on the strength and workability of the concrete,while ductility will be considered in our later experiments.

Currently,to achieve excellent mechanical behavior,some spe-cial techniques and raw materials must be adopted in the prepara-tion of UHPC,which include:

(a)Coarse aggregate is removed to enhance the homogeneity of

concrete.

(b)Metal ?ber or steel tube is introduced to improve ductility of

composites.

(c)High quality superplasticizer and large quantities of super-?ne silica fume and quartz are added,to achieve a low water/binder ratio to reduce porosity and improve strength.(d)Pressure may be applied before and during the setting to

increase the compactness of the concrete.

(e)High activity micro-silica and/or precipitated silica may be

mixed into cementitious materials to accelerate the hydra-tion of cement and catalyze a strong pozzolanic reaction effect.

(f)Steam curing may be supplied to gain higher strength.In short,to gain the desired strength of a UHPC,well-chosen raw materials and sophisticated technical procedures are convention-ally required,which makes it too costly to meet the demand of large-scale project engineering.Therefore,it is of great signi?cance to ?nd appropriate ways to obtain the strength of UHPC cheaply.

0958-9465/$-see front matter ó2011Elsevier Ltd.All rights reserved.Corresponding author.

E-mail address:chongwang@https://www.doczj.com/doc/2e16037617.html, (C.Wang).

It would be desirable for UHPC to possess high ?uidity perfor-mance to satisfy the pouring and compaction at the construction site.Previous engineering projects of UHPC,such as the Sherbrooke footbridge in Canada,the Seonyu footbridge in Korea,the Shaw-nessy tramway station in Canada,and the beams of Cattenom and Civaux power plants used mostly prefabricated concrete [1].Only a few fresh UHPCs have been cast in place at the project site.In this investigation,UHPC with good workability and a target compressive strength greater than 150MPa was prepared with common technology and materials,especially without the removal of the coarse aggregate.2.Experiment

2.1.Technical foundations for the preparation

In this study,the guidelines for preparing UHPC include the fol-lowing:(a)common and easy to obtain raw materials and (b)no special machine nor special processes of concrete mixing,pouring and curing.

Based on the above principles,the experiment was designed as below:

(1)The water/binder ratio (W/B)was reduced to 0.14–0.18,

which is often used in Reactive Powder Concrete (RPC).(2)A maximum binder content of 900kg/m 3was adopted to

obtain the necessary paste volume and to achieve high ?uid-ity of UHPC.

(3)A Large quantities of super?ne mineral additives such as sil-ica fume (SF),ground granulated blast furnace slag (GGBS),and limestone powder (LP)were added to optimize the com-position and micro-structure of the hydrated binder paste,and to reduce the hydration heat.

(4)To reduce the cost of UHPC,it is a good approach to utilize

coarse aggregate with a maximum size of 20mm in its preparation.

(5)Common technologies were adopted for preparation of

UHPC,which include mixing of fresh concrete with normal forced mixer,pouring in case of good ?uidity,compaction by vibrating,and curing at room temperature.2.2.Raw materials

Grade 52.5ordinary Portland cement (C)was manufactured by the Chongqing Tenghui Company.Semi-condensed SF was sup-plied by Elkem Company,China.GGBS was from the Chongqing Iron and Steel Company and ground in the laboratory.LP was made from limestone rock from the Chongqing Gele Mountain.As an essentially inert mineral material,LP was regarded as a component of the cementitious materials in this investigation.The chemical compositions and physical properties of each cementitious mate-rial are listed in Table 1.

The ?ne aggregate was medium sand with a ?neness modulus of 2.3,an apparent density of 2.72g/cm 3,and a bulk density of 1.60g/cm 3.The coarse aggregate was crushed limestone with a

maximum diameter of 20mm,an apparent density of 2.70g/cm 3,and a bulk density of 1.65g/cm 3.The size distributions of the coarse and ?ne aggregates are listed in Table 2.

The aminosulfonic acid-based superplasticizer and citric acid as a retarder were obtained from the Chongqing Dianni Company.2.3.Experimental methods

2.3.1.Workability and compressive strength test

A forced single-axis mixer with a rotational speed of 45rpm was used to prepare fresh concrete in this study.The mixer is shown in Fig.1.All Concrete mixtures were mixed using the fol-lowing procedures:

Coarse aggregate ;fine aggregate ;and binders !1min Water !2min

Superplasticizer !2min

Discharging

The ?uidity of fresh concrete,including slump and spread,was measured with a normal 300mm slump cone in a laboratory with a temperature of (20±3)°C.Spread refers to the average diameter of the concrete spread in this paper,which is obtained after slump testing:

Spread ?eD max tD min T=2

where D max and D min refer to the maximum and minimum diameter of the measured concrete respectively.A spread of 200mm means that the fresh concrete has no ?ow ability.

Cube specimens of 100mm ?100mm ?100mm were used for compressive strength testing.The casting and compacting of these specimens were performed after the ?uidity test.The specimens were demolded approximately 24h after casting,and then cured in the moist room at a temperature of (20±2)°C and no less than 95%relative humidity until testing.At least three specimens were tested at each age to compute the average strength.

2.3.2.SEM investigation

To understand the strength mechanism of UHPC,the micro-structure of hardened paste and interfacial transition zone be-tween aggregate and cement paste (ITZ)was investigated using an SEM,The samples for SEM analysis were produced by taking small pieces from the concrete fractured specimen.The broken pieces were soaked and rinsed using anhydrous alcohol,oven dried at 60°C,and then coated with gold powder before testing.The SEM study was carried out by using an accelerating voltage of 20kV.3.Results and discussion

3.1.Preparation of UHPC with common technology and materials 3.1.1.In?uence of binder content on strength and ?uidity of UHPC In this experiment,three mixtures with the same binder com-ponent and W/B of 0.18were tested.The mixture proportions are listed in Table 3,and the results are shown in Fig 2.

These three mixtures differed in their ?uidity.Mix 1-1with 500kg/m 3binder content exhibited a very dry fresh mixture with

Table 1

Chemical compositions and physical properties of binders.Binders

Chemical compositions (%)Speci?c surface area (m 2/kg)

Density (g/cm 3)

CaO

SiO 2Al 2O 3MgO Fe 2O 3TiO 2SO 3LOI C 59.3720.869.28 2.07 3.740.47 2.49 1.47330 3.10SF –

95.19–

0.800.13–– 2.8120,000 2.23GGBS 50.4430.3616.90 1.840.340.57 2.42870 2.752 C.Wang et al./Cement &Concrete Composites xxx (2011)

xxx–xxx

a slump of0,mix1-2with700kg/m3binder content had a130mm slump,and mix1-3with900kg/m3presented a very good?uidity of245mm.The test results show that the slump and spread of fresh concrete improved with the increase of the ratio of mortar volume to coarse aggregate volume and ratio of paste volume to aggregate volume,while the binder content of UHPC rose from 500kg/m3to900kg/m3.

Due to the very low W/B,hardened paste with high?uidity ob-tains a very compact structure,and thus very high strength.Fig2 shows that,in the case of?xed W/B in this study,the compressive strength improved with the increase of binder content.All three mixtures reached compressive strengths of more than150MPa after90d.

The experimental results show that it is very important to keep the paste volume high to gain high?uidity and ultra-high strength behavior.In this experiment,900kg/m3cementitious materials was set as the ceiling to balance between performance and cost.

In this investigation,a maximum cementitious material content of900kg/m3was https://www.doczj.com/doc/2e16037617.html,pared with the commonly adopted content of300–600kg/m3,900kg/m3cementitious material in concrete is not impressive.However,contrasted with1200kg/ m3,that typically used in RPC,900kg/m3is much more desirable in project engineering.Particularly,the mineral additives used in this study are industrial by-products,such as silica fume,which is abundant in China,GGBS,and limestone powder from leftover fragments of crushed stone.

3.1.2.In?uence of GGBS replacement of cement on strength and

?uidity of UHPC

Among high activity mineral additives,such as SF,GGBS,?y-ash and metakaolin,GGBS is unique.It is latent in hydraulic reactivity, but it can be catalyzed by proper activators such as Portland ce-ment clinker,lime,gypsum,and alkali metal hydroxides,carbon-ates or silicates to form cementitious materials.The main reaction product generally cited for alkali-activated slag is C–S–H gel similar to that found in hydration products of Portland cement, but with a lower Ca/Si ratios(around0.7)[11].Yaz?c?et al.[12] presented a good illustration for preparing RPC with large replace-ment of about15–45%GGBS successfully.The addition of GGBS in this study helps to optimize the hydration of the binder.

Three mixes with different GGBS replacement and10%SF by mass content are listed in Table4,and the experimental results are shown in https://www.doczj.com/doc/2e16037617.html,pared with mixture2-1concrete,which had no GGBS,mixture2-2containing20wt.%GGBS replacement had higher?uidity,much lower compressive strength at early ages (28d and56d),but approximately equal strength at later ages

Table2

The size distribution of coarse aggregate and?ne aggregate.

Screen size(mm)Cumulative sieve residue(%)

Coarse aggregate Fine aggregate

26.500

19.09.30

16.022.80

9.5061.70

Table3

Mixture proportions for test of in?uence of binder content on strength and?uidity of UHPC.

Mix Binder(kg/m3)Binder compositions(%)W/B Water(kg/m3)Superplasticizer(kg/m3)Fine aggregate(kg/m3)Coarse aggregate(kg/m3)

C SF

1-150090100.1890187971195

1-270090100.18126187151073

1-390090100.1816218616923

C.Wang et al./Cement&Concrete Composites xxx(2011)xxx–xxx3

(90d,180d and 365d).Mixture 2-3containing 40wt.%GGBS had a very low compressive strength and ?uidity at all ages compared to the control mixture 2-1.

https://www.doczj.com/doc/2e16037617.html,pressive strength and ?uidity of UHPC with different W/B Three mixtures containing 900kg/m 3binder material and W/B of 0.14,0.16,and 0.18respectively,were tested.The cementitious materials consisted of 10wt.%SF,20wt.%GGBS and 70wt.%ordin-ary Portland cement.The mixture proportions of these concretes are presented in Table 5,and the results are shown in Fig

4.

It is seen that,with the increase of W/B,the ?uidity of concrete improved while the compressive strength at early ages (28d)de-creases,which is well known.However,the highest strength was achieved with a W/B of 0.16,not with W/B of 0.14at later ages (56d,90d,180d,and 365d).The reason is that the unhydrated ce-ment in a low W/B had a detrimental effect on the structure of the hydrated material.Wang Chong and Pu Xincheng’research [13]illustrated that the hydration degree of hardened cement paste with W/B of 0.16is higher than that of W/B of 0.10at all ages,and external water could migrate into the compact hardened paste to react with cement,as demonstrated by a non-evaporable water content increase with curing age in the case of standard curing con-ditions.For W/C less than about 0.36,there is insuf?cient capillary pore space available for the complete hydration of the cement [14].In this investigation,it is suggested that more unhydrated cement in concrete with W/B of 0.14had a more detrimental effect on the hydrated structure than that of concrete with 0.16W/B.

3.1.

4.Preparation of UHPC with ground LP

LP has been researched in high-?uidity concrete in some litera-tures [13,15,16].In this study,LP was used to prepare the UHPC to-gether with 10%SF,and 20%GGBS by mass.The mixture proportions with different LP replacements for cement are listed in Table 6.The test results are given in Fig 5.

Before the test,it was assumed that the incorporation of LP could improve the ?uidity of the fresh concrete,but might be det-rimental to the mechanical behavior of the hardened concrete with such a low W/B.Surprisingly,compared with mixture 4-1with 0%LP as a control,mixture 4-2with 20%LP replacement achieved a

higher slump of 240mm,and a greater compressive strength at ages from 28d to 365d.In comparison to the control,the mixture with 40%LP replacement had a higher ?uidity but a lower strength at the same ages.Nevertheless,its compressive strength at 365d was still 164.3MPa.

In Section 3.1.2,the binder system of ordinary Portland ce-ment +SF +GGBS has shown a good effect on strength perfor-mance enhancement.In this section,the concrete containing LP of proper content presented a greater strength and higher ?uidity.As an inert mineral material,why could LP improve the structure and strength of UHPC?

The authors have proved that limestone powder accelerated the hydration process of cement and silica fume in another paper [13].Shi et al.[15],Zhu and Gibbs [16],and Svermova et al.[17]have also claimed that LP was bene?cial to concrete structure and per-formance.Tang [18]con?rmed that addition of LP improved the hydration degree of cementitious materials.Refs.[19,20]have shown that calcium aluminate monocarbonate is preferably formed,the hydration of C 3S is accelerated and some carbosilicates are produced in pastes containing limestone constituents.Addi-tional literatures [21,22]shows that LP in cementitious materials systems has a compaction ?ller and great dispersion effect on the hydration precipitation of Ca(OH)2and C–S–H gel,and plays a core role in crystallization.

The test results show that LP can be applied to prepare UHPC,which we ?nd,after extensive literature review,to be the ?rst at-tempt of this kind.

3.2.UHPC ?uidity loss with time

For ready-mix and pumpable concretes,a low ?uidity loss with time for fresh concrete is a must.In the present study,the ?uidity loss with time was measured to determine the possibility of apply-ing UHPC prepared with our methodology to pumpable project engineering.To maintain a long workable time for UHPC,a retarder was added together with superplasticizer,and the mixture propor-tions are presented in Table 7.The results are given in Fig.6.

It is observed that,with a W/B of 0.16,except for mixture 5-1which had 10%SF cement replacement and a very low initial and

Table 4

Mixture proportions for test of in?uence of GGBS replacement on strength and ?uidity of UHPC.Mix

Binder (kg/m 3)

Binder components (%)W/B

Water (kg/m 3)

Superplasticizer (kg/m 3)

Fine aggregate (kg/m 3)

Coarse aggregate (kg/m 3)

C

SF GGBS 2-1900901000.18162186169232-29007010200.18162186169232-3

900

50

10

40

0.18

162

18

616

923

4 C.Wang et al./Cement &Concrete Composites xxx (2011)xxx–xxx

120min slump,other mixtures with SF and GGBS replacement (mixture 5-2,and mixture 5-3),and with SF,GGBS and LP (mixture 5-4,mixture 5-5,and mixture 5-6)presented excellent workability service times.Even at 120min after casting,the slumps were still maintained at more than 200mm,which indicates that these UHPC can be used as a pumpable concrete when superplasticizer and retarder are added together.

3.3.Mechanism for ?uidity and strength of the UHPC

This research successfully prepared UHPC with good work-Good workability resulted from the excellent ?uidity at a very low water–binder ratio.The volume of cementitious material and the mixes of superplasticizer and mineral additives are the key factors for achieving the desired ?uidity.Another key factor is the relationship between volume of mortar or paste and the void space of aggregates.In this experiment,for example,the void space of coarse aggregate of Mix 3-2reached 0.658m 3and that in the ?ne aggregate 0.431m 3.The mortar volume was 0.680m 3and paste volume 0.453m 3,which made enough room for the coarse and ?ne aggregates to form a suspension structure in the mixture,thus the ?uidity of the UHPC is Table 5

Mixture proportions of test for in?uence of W/B on strength and ?uidity of UHPC.Mix

Binder (kg/m 3)

Binder components (%)W/B

Water (kg/m 3)

Superplasticizer (kg/m 3)

Fine aggregate (kg/m 3)

Coarse aggregate (kg/m 3)

C

SF GGBS 3-19007010200.14126186169233-29007010200.16144186169233-3

900

70

10

20

0.18

162

18

616

923

Table 6

Mixture proportions for preparation of UHPC with ground limestone powder (LP).Mix

Binder (kg/m 3)

Binder components (%)W/B

Water (kg/m 3)

Superplasticizer (kg/m 3)

Fine aggregate (kg/m 3)

Coarse aggregate (kg/m 3)

C

SF GGBS LP 4-190070102000.16144186169234-2900501020200.16144186169234-3

900

30

10

20

40

0.16

144

18

616

923

C.Wang et al./Cement &Concrete Composites xxx (2011)xxx–xxx

5

To explore the strength mechanism of the UHPC,the authors

used SEM to investigate the microstructure of the UHPC mixture with 0.16W/B at 180d age.The W/B of the UHPC sample was 0.16,cementitious materials of the sample were composed of 70%cement,20%GGBS and 10%SF by mass.The SEM image of hardened paste and the ITZ structure in the UHPC sample are shown in Figs.7and 8,respectively.

In the SEM images of the samples,one can observe a very dense structure in the hardened paste,and only a few air pores are seen in the SEM image of Fig.7,which can be attributed to the very low W/B,and the hydration of cement and the pozzola-Fig.7,one can observe that the main hydration product is a homogeneous morphology of C–S–H gel,and no Ca(OH)2and nor ettringite products can be seen.

Fig.8reveals that the UHPC prepared with very low water/binder ratio,and with hardened paste made of cement incorpo-rating silica fume and ground granulated blastfurnace slag,and coarse aggregate made of crushed limestone,has a very compact ITZ structure.No distinct porosity is found in the ITZ,which is conducive to UHPC preparation.A homogenous morphology of the paste structure and the compact ITZ structure are the theo-retical rationales for preparing UHPC without removing coarse Table 7

Mixture proportions for test of ?uidity loss with time of UHPC.Mix

Binder (kg/m 3)Binder components (%)W/B

Water (kg/m 3)

Superplasticizer (kg/m 3)Retarder (kg/m 3)Fine aggregate (kg/m 3)Coarse aggregate (kg/m 3)C SF GGBS LP 5-19009010000.1614414.4 3.66169235-290070102000.1614414.4 3.66169235-390050104000.1614414.4 3.66169235-4900501020200.1614414.4 3.66169235-5

900

30

10

20

40

0.16

144

14.4

3.6

616

923

5-1

5-2

5-3

5-4

5-5

Initial 120 mins

5-1

5-2

5-3

5-4

5-5

S p r e a d (m m )

Initial 120 mins

50100

150200250

300

100200300400500

6006 C.Wang et al./Cement &Concrete Composites xxx (2011)xxx–xxx

4.Conclusion

From the results mentioned above,it can be concluded that,with extremely low W/B,high binder content,multi-addition of SF,GGBS,LP,and high standard superplasticizer (and retarder),UHPC can be prepared with common technology and without removing the coarse aggregate.In our experiment,UHPC with a maximum slump of 268mm and the highest compressive strength of 175.8MPa at 90d,and 182.9MPa at 365d was successfully pre-pared.It is discovered that W/B of 0.16and cementitious material content of 900kg/m 3which contained 50%cement,10%SF,20%GGBS,and 20%LP,as well as an appropriate dosage of superplast-icizer to assure adequate ?uidity are mandatory for the successful preparation.The test results also conclude that UHPC can be pre-pared as a pumpable concrete when standard superplasticizer and retarder are added together.

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个人先进事迹简介

个人先进事迹简介 01 在思想政治方面,xxxx同学积极向上,热爱祖国、热爱中国共产党,拥护中国共产党的领导.利用课余时间和党课机会认真学习政治理论,积极向党组织靠拢. 在学习上,xxxx同学认为只有把学习成绩确实提高才能为将来的实践打下扎实的基础,成为社会有用人才.学习努力、成绩优良. 在生活中,善于与人沟通,乐观向上,乐于助人.有健全的人格意识和良好的心理素质和从容、坦诚、乐观、快乐的生活态度,乐于帮助身边的同学,受到师生的好评. 02 xxx同学认真学习政治理论,积极上进,在校期间获得原院级三好生,和校级三好生,优秀团员称号,并获得三等奖学金. 在学习上遇到不理解的地方也常常向老师请教,还勇于向老师提出质疑.在完成自己学业的同时,能主动帮助其他同学解决学习上的难题,和其他同学共同探讨,共同进步. 在社会实践方面,xxxx同学参与了中国儿童文学精品“悦”读书系,插画绘制工作,xxxx同学在班中担任宣传委员,工作积极主动,认真负责,有较强的组织能力.能够在老师、班主任的指导下独立完成学院、班级布置的各项工作. 03 xxx同学在政治思想方面积极进取,严格要求自己.在学习方面刻苦努力,不断钻研,学习成绩优异,连续两年荣获国家励志奖学金;作

为一名学生干部,她总是充满激情的迎接并完成各项工作,荣获优秀团干部称号.在社会实践和志愿者活动中起到模范带头作用. 04 xxxx同学在思想方面,积极要求进步,为人诚实,尊敬师长.严格 要求自己.在大一期间就积极参加了党课初、高级班的学习,拥护中国共产党的领导,并积极向党组织靠拢. 在工作上,作为班中的学习委员,对待工作兢兢业业、尽职尽责 的完成班集体的各项工作任务.并在班级和系里能够起骨干带头作用.热心为同学服务,工作责任心强. 在学习上,学习目的明确、态度端正、刻苦努力,连续两学年在 班级的综合测评排名中获得第1.并荣获院级二等奖学金、三好生、优秀班干部、优秀团员等奖项. 在社会实践方面,积极参加学校和班级组织的各项政治活动,并 在志愿者活动中起到模范带头作用.积极锻炼身体.能够处理好学习与工作的关系,乐于助人,团结班中每一位同学,谦虚好学,受到师生的好评. 05 在思想方面,xxxx同学积极向上,热爱祖国、热爱中国共产党,拥护中国共产党的领导.作为一名共产党员时刻起到积极的带头作用,利用课余时间和党课机会认真学习政治理论. 在工作上,作为班中的团支部书记,xxxx同学积极策划组织各类 团活动,具有良好的组织能力. 在学习上,xxxx同学学习努力、成绩优良、并热心帮助在学习上有困难的同学,连续两年获得二等奖学金. 在生活中,善于与人沟通,乐观向上,乐于助人.有健全的人格意 识和良好的心理素质.

自我管理演讲稿英语翻译

尊敬的领导,老师,亲爱的同学们, 大家好!我是5班的梁浩东。今天早上我坐车来学校的路上,我仔细观察了路上形形色色的人,有开着小车衣着精致的叔叔阿姨,有市场带着倦容的卖各种早点的阿姨,还有偶尔穿梭于人群中衣衫褴褛的乞丐。于是我问自己,十几年后我会成为怎样的自己,想成为社会成功人士还是碌碌无为的人呢,答案肯定是前者。那么十几年后我怎样才能如愿以偿呢,成为一个受人尊重,有价值的人呢?正如我今天演讲的题目是:自主管理。 大家都知道爱玩是我们孩子的天性,学习也是我们的责任和义务。要怎样处理好这些矛盾,提高自主管理呢? 首先,我们要有小主人翁思想,自己做自己的主人,要认识到我们学习,生活这一切都是我们自己走自己的人生路,并不是为了报答父母,更不是为了敷衍老师。 我认为自主管理又可以理解为自我管理,在学习和生活中无处不在,比如通过老师,小组长来管理约束行为和同学们对自身行为的管理都属于自我管理。比如我们到一个旅游景点,看到一块大石头,有的同学特别兴奋,会想在上面刻上:某某某到此一游话。这时你就需要自我管理,你需要提醒自己,这样做会破坏景点,而且是一种素质低下的表现。你设想一下,如果别人家小孩去你家墙上乱涂乱画,你是何种感受。同样我们把自主管理放到学习上,在我们想偷懒,想逃避,想放弃的时候,我们可以通过自主管理来避免这些,通过他人或者自己的力量来完成。例如我会制定作息时间计划表,里面包括学习,运动,玩耍等内容的完成时间。那些学校学习尖子,他们学习好是智商高于我们吗,其实不然,在我所了解的哪些优秀的学霸传授经验里,就提到要能够自我管理,规范好学习时间的分分秒秒,只有辛勤的付出,才能取得优异成绩。 在现实生活中,无数成功人士告诉我们自主管理的重要性。十几年后我想成为一位优秀的,为国家多做贡献的人。亲爱的同学们,你们们?让我们从现在开始重视和执行自主管理,十几年后成为那个你想成为的人。 谢谢大家!

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