asrpresentationa for Irr Deptresearch.rid.go.th/rte/attachments/article/72/2.Alkali... · 2019. 2....
Transcript of asrpresentationa for Irr Deptresearch.rid.go.th/rte/attachments/article/72/2.Alkali... · 2019. 2....
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การเสอมสภาพของคอนกรตจากมวลรวม“มะเรงคอนกรต
Alkali Silica Reaction”
รวมจดโดย
ภาควชาวศวกรรมโยธา คณะวศวกรรมศาสตร มหาวทยาลยเกษตรศาสตร
โครงการฝกอบรมคอนกรตสมยใหม ๑ กพ ๒๕๖๒ เพอสานกวจยและพฒนากรมชลประทาน
What are they?Do we have “them”?
Why do we have to “know” them?What if we don’t “know” them?
Outline • AAR, ASR, ACR what are they?
• What are their effects
• What are the symptons?
• Is there any mitigation? How?
• Will we have problem?
• How can we face the problem?
• Modern concrete: Self compacting concrete , SCC
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FURNAS DAM, BRAZIL
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Meantwrong, Wales (Sims andPoo, 2003)
ICAAR2008_061_Andrade
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What is AAR, ASR, ACRand ปญหาอลคาไลนซลกาทวโลก
ปญหาอลคาไลนซลกาในประเทศไทย พศ 2552
AAR:Alkali Aggregate Reaction (AAR)
• → gel
• gel + MC expans.
“ปฏกรยาเคมทเกดขนในคอนกรต / มอรตาร ระหวาง Hydroxyl ion จาก Na, K จากปนซเมนตและสารองคประกอบของมวลรวมบางชนดภายในสภาวะแวดลอมเฉพาะทเหมาะสมและอาจทาใหเกดการขยายตวทเปนผลเสยตอคอนกรตหรอมอรตารได” (ACICommittee116)
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ASR Mechanism and required factors
Well Crystallized Poorly Crystallized
Alkali:
cement
Reactive silica:
agg.
Water :
envi.
internal
กลสมบตของคอนกรตทเสอมสภาพจาก ASR มกลดลง แตมากนอยขนกบระดบความเสย หายในขณะทตรวจสอบ
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AAR มกชนด? ตางกนอยางไร
1. ปฏกรยาอลคาไลซลกา , ASR (ปฏกรยาระหวางอลคาไลโดยเฉพาะไฮดรอกไซด กบซลกาในมวลรวมบางชนด): often found
2. ปฏกรยาอลคาไลคารบอเนต, ACR (ปฏกรยาระหวางอลคาไล และแรคารบอเนตในมวลรวมบางประเภท): less finding, difficult to
solve
3. ปฏกรยาอลคาไลซลเกต (Alkali Silicate Reactions) (ปฏกรยาระหวางอลคาไล และแรซลเกต ทเจอปนอยในเนอมวลรวม ) Slow/Late-Expanding Alkali Silicate/Silica Reaction
(SLASSR, ASSR) : slow, need more time, rather continued expansion, less finding
ลกษณะความเสยหายเปนอยางไร
• รอยแตกราวแบบแผนท
• การขยายรอยแตกราวแบบอนๆ
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• การบดเบยว ผดแนวของอาคารหรอสวนประกอบ
• การซมปดของสารยาแนว • การซมเยมของเจลในลกษณะตางๆ
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• การเปลยนส• การปรากฏคราบขาว• การแตกหลดของมวลรวม
• การเยมของASR เจล
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ลกษณะความเสยหายภายในทอาจตรวจพบจากการตรวจสอบดวยเทคนคตางๆ
• รองรอยของASR rim
• พบผลตภณฑเจลในชองวางและรอยแตกราวภายในซเมนตเพสต
ลกษณะความเสยหายภายในทอาจตรวจพบจากการตรวจสอบดวยเทคนคตางๆ
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Plate formed react. products in reacted sericite aggregate
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ผลกระทบตอสมบตทางกล• ขนกบระดบระดบความรนแรง บรเวณทเกด
กลสมบต เกณฑตาสด(รอยละ)กาลงคอนกรตเมอเปรยบเทยบกบคอนกรตทไมมปญหาโดยพจารณาระดบการขยายตวเปนเกณฑ
0.5 มม/ม 1.0 มม/ม 2.5 มม/ม 5.0 มม/ม 10.0 มม/ม
กาลงรบแรงอด(ลกบาศก) 100 85 80 75 70Uniaxial compression 95 80 60 60 *กาลงรบแรงดง 85 75 55 40 *modulus of elasticity 100 70 50 35 30
(ปรบปรงจาก PRICE 1987; ICOLD: COMMITTEE ON CONC. DAMS
2008; Task Group of The Institution of Structural Engineers JULY 1992)
ในภมภาคนมลกษณะเออตอ AAR อยางไรบาง
• Geology / landform
• วสด : หน ทราย ปนซเมนต• นา ความชน (การเกด การขยายตว) : ลกษณะการใชงานโครงสราง• ภายนอก• ภายใน (ความหนาขององคอาคาร)
• คณภาพในการทางาน
• อณหภม: รอน ชน
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ในภมภาคนมปจจยเออตอ ASR อยางไรบาง
• แหลงมวลรวม: ม / ไมมปญหา• หน และ ทราย Pessimum effect, recrystallization
Sujjavanich S., Wonkhamchan W., Won-in K., et al. , 2012
• อลคาไล (จากปนซเมนต)
• จากแหลงอนๆ: นา สารผสมเพม หน
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Natural light UV light
Ident. Code Type Definition Calcite QuartzDolomiteKaolinite MuscovitMicroclin Albite ClinochlorDiopside Pyrite ntmorillo Sum
I RYLS (TDolomitic Lim
Rayong Limestone (Trat Quartzite) 54.3 10.4 19.0 1.6 6.6 1.6 4.8 0.9 0.7 100.0
H CBCS Calc-Silicate
Chon Buri Calc-silicate 76.3 2.0 0.5 0.4 0.7 5.8 1.6 1.6 11.2 100.0
G CBGN GraniteChon Buri Granite 2.8 24.0 3.2 14.9 21.7 25.8 6.3 1.4 100.0
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มาก นอย
A
D
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What we have done:
• Research work• Basic research to understand the mechanism/
local materials
• Database for local aggregates
• Mitigation
• Public awareness • Academic paper
• Workshop / seminar (at least 7 times)
ประโยชนทคาดหวงจากการบรรยาย
วศวกรในสาขาทเกยวของ
• ขอมลและความรเบองตนเกยวกบASR และความเสยหาย• กรณศกษาจากตางและในประเทศ• สรางความตระหนกร เพอหาแนวทางปองกนภาคราชการและการศกษา และอตสาหกรรมกอสราง ในภาพรวม
• องคความรเกยวกบ ASR ทเกดจากหน บางชนดซงมปรมาณมากในประเทศ • การสรางความตระหนกตอปญหาและใหความรทวไปเกยวกบ ASR ตอ
สาธารณะ และแนวทางทวไปในการใชประโยชนจากหนอยางมประสทธภาพ
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High Performance Concrete (HPC)
• “Concrete that meets special performance and uniformity requirements that can not always be obtained using conventional ingredient, nor mal mixing procedure and typical curing practice” (P.Zia)
คอนกรตสมยใหม
What are the differences between concrete’s concept in the past and present?
Past : focused on improved mechanical properties
Present: focused on improved constructability
easy in placing / compacting
High strength concrete: how high is high
34 Mpa in 1950s40 Mpa in 1960s134 Mpa currently
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Present: focused on improved durability
low permeability, volume stability, deforms less, cracks less , more resistance to chemical attack, freezing and thawing, at higher temperatures
: improved mechanical properties
high early age strength, long term strength, resistance to abrasion /impact loading
Challenge for materials and systems are characterised by
Superior strength, toughness and ductility
Enhanced durability/service life
Increased resistance to abrasion, corrosion, chemicals / fatigue
Initial and life-cycle cost efficiencies
Improved response to natural disasters and fire
Aesthetics and environmental compatibility
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HPC basis:
• proper utilization of
• w/c (0.38 vs 0.42)
• air entrained
• Superplasticizer
Self-Compacting Concrete SCC, flowable concrete, self leveling concrete
Good for: Heavily reinforcement,Narrow size, complex shape, const.rate: faster
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• Development:
• Japan: 1983
• Durability /quality of construction work
• labor cost, development of antiwashoutadmixture
• Workability problem of using antiwashout in air
• entrapped air / difficult compaction between bars
• Optimum combination of water-powder ratio & superplasticizer to get self-compactability for a fixed aggregate contact concrete
• Okamura (1986) proposed the idea of concrete own weight self compacting wo.need of external vibration
• Characteristics: (filling ability /passing ability)
• High deformability
• Rate of deformability
• Capacity of deformability
• High viscosity (wo segregation), when flow through the confined zone
• Passing ability
• No segregation
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• Self compacting concrete focuses on:
• Passabilily through steel space
• Segregation problem / fluidity
• Criteria :
• Deformability: high paste :pozzolan eg fa, sp
• Segregation resistance: low w/b, sufficient powder, special agent (viscosity agent)
• Passing ability : low w/b, limit CA, stable air bubble
• Durability : use pozzolan
• How?
• Limiting aggregate content, agg.size
• Low water-powder ratio /High dosage of SP
Akashi Straits Bridge
• high liquidity • requires no compaction• greatly increased efficiency in casting • reduced construction time• Pipe transporting from mixing plant
Highly workable concrete
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SCCTypes (JSCE)
• Powder type SCC
– primarily by reducing the water powder ratio (high powder content) to impart adequate segregation resistance /using air entraining / HRWR to impart high deformability.
• Viscosity agent type SCC (polymer based type)
– use of a viscosity agent to impart segregation resistance and air-entraining and HRWR: high deformability to the fresh concrete.
SCCTypes (JSCE)
• Combination SCC
– primarily by reducing water powder ratio (high powder content) to impart adequate segregation resistance and using an air –entraining, HRWR (to impart high deformability: A viscosity agent is added to reduce the quality fluctuation of fresh concrete, so as to facilitate the quality control of concrete.
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Cautions for self compacting concrete
• Construction:• High lat.pressure on formwork during placing
• Leakage
• Slump loss (High temp.)
• Delay setting
• Shrinkage (high paste)
• High heat (high paste)
Cautions for self compacting concrete
• Coarse aggregate content (~ 50% of solid volume)
• Fine aggregate content (~ 40% of mortar volume)
• Water-powder ratio in volume (~ 0.9 to 1.0)
• depending on properties of the powder
• Superplasticizer dosage and the final water-powder ratio are determined so as to ensure the self-compactability
• High lat.pressure on formwork during placing
• Difficult to control air content / Air void surface (appearance)
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SCC limitation
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Parameters affecting SCC
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• Quality control
• a test characterizing the flow of concrete
– 2 parameters
• yield stress
• plastic viscosity
Verification of self compactability
Definition
• Filling ability: “ability to flow into all spaces within the formwork under its own weight”
• Tests: slump flow, V-funnel etc
• Passing ability: “ability to flow through tight openings, such as spaces between steel reinforcing bars, under its own weight”
• Test: U-box, L-box, Fill-box, and J-ring test methods.
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Fill cone with concrete, no tamp, simply strike off the concrete level with the top of the cone with the trowel.Raise cone vertically and allow
the concrete to flow out freely. record the time taken for the concrete to reach 500mm spread circle (This is the T50 time). The T50 time is secondary indication of flow. A lower time indicates greater flow ability. 3-7 seconds is acceptable.
Slump flow
V funnelClose trap door and place bucket underneath. Fill with the concrete without compacting or tamping. Open (10 sec after filling ) trap door and allow flow out under gravity. Start the stop watch when the trap door is opened, and record the time for the complete discharge (the flow time). This is taken to be when light is seen from above through the funnel. The whole test has to be performed within 5 minutes.Procedure flow time at T5 minutes:
Close the trap door and refill the V-funnel immediately after measuring the flow time. Refill concrete ,Open trap door 5 minutes after the second fill of the funnel and allow the concrete to flow out under gravity. record the time
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L-Box filling / passing ability of SCC, /serious lack of stability (segregation)
fill vertical section with concrete sample, leave 1 min. Lift sliding gate , allow concrete to flow out into the horizontal section, record time for concrete to reach 200 and 400 marks. When concrete stops flowing, distances ‘H1’ and ‘H2’ are measured. Calculate H2/H1, the blocking ratio. The whole has to performed within 5 minutes.
H2/H1=1. ‘blocking ratio’, is unity, the better the flow of concrete. The minimum acceptable value of 0.8.
14 liter of concrete
: Moisten inside surface of the apparatus, fill vertical section with concrete sample. Leave 1 min. Lift sliding gate , concrete flow out into the other compartment. After concrete rest, measure the height of the concrete / calculate mean (H1), (H2). performed within 5 min.
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J-Ring: BS EN 12350-12 To determine flowability, ( flow time / capability of self compacting concrete to pass through obstacles)
![Page 29: asrpresentationa for Irr Deptresearch.rid.go.th/rte/attachments/article/72/2.Alkali... · 2019. 2. 4. · G CBGN Granite Chon Buri Granite 2.8 24.0 3.2 14.9 21.7 25.8 6.3 1.4 100.0.](https://reader035.fdocuments.net/reader035/viewer/2022071406/60fd40626101020ed678f31d/html5/thumbnails/29.jpg)
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