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45/20  75slump
45/20  100slump
2隻石矢有咩分別,slump75和100除左希和傑,仲有咩分別
2隻石矢壓core,會否因slump不同而lead有不同結果



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你問得出呢條問題,唔怕得罪講句,就算寫個答案出黎,你都唔會明白!


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slump value does not affect the strength of concrete... slump value is about the workability NOT strength.

hope you can understand what I am talking above.






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引用:
原帖由 kwan9lee 於 2010-10-15 05:25 PM 發表
slump value does not affect the strength of concrete... slump value is about the workability NOT strength.

hope you can understand what I am talking above.
You are correct ONLY for cube test results
Different slump rate DO effect the grade strength after cast on site.



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引用:
原帖由 big-67 於 2010-10-15 05:36 PM 發表



You are correct ONLY for cube test results
Different slump rate DO effect the grade strength after cast on site.
may i know more how slump affect the strength?



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引用:
原帖由 big-67 於 2010-10-15 05:36 PM 發表



You are correct ONLY for cube test results
Different slump rate DO effect the grade strength after cast on site.
Grade 45 Slump 75 同 Grade 45 Slump 100 個strength 咪係28日係45MPa law

e個問題同你問1000斤鐡 重d 定1000斤棉花重d 一樣?



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個人認為SLUMP吾會AFFECT石矢強度 但係...
假落樓面石矢,PROPOSE左2隻石矢同時submitted左(樓面大亦用100slump,細亦用75slump)
1.45/20 100SLUMP
2.45/20 75SLUMP
但實際茖樓面全部用75slump或全部用100slump,會有咩問題出現?

[ 本帖最後由 風見 於 2010-10-15 10:11 PM 編輯 ]



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引用:
原帖由 風見 於 2010-10-15 10:06 PM 發表
個人認為SLUMP吾會AFFECT石矢強度 但係...
假落樓面石矢,PROPOSE左2隻石矢同時submitted左(樓面大亦用100slump,細亦用75slump)
1.45/20 100SLUMP
2.45/20 75SLUMP
但實際茖樓面全部用75slump或全部用100slump,會有咩問題出現?
the slump is adjusted by the amount of cement, which in turn affects the colour of the hardened concrete.  That's no problem wrt the strength.  but the aesthetically.... depending on any finishes on the concrete.  also the shrinkage and hence cracks.

(provided that both types are well compacted.)

Am I correct?






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原帖由 joblessness 於 2010-10-15 11:49 PM 發表


the slump is adjusted by the amount of cement, which in turn affects the colour of the hardened concrete.  That's no problem wrt the strength.  but the aesthetically.... depending on any finishes  ...
Correct only if you say "One crab worser then one crab"
It should be a safety issue also.
Affects are on the formwork and falsework design and voids of the casted concrete.



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你叫得45/20 concrete, 咁core 出黎應該都壓到45MPa (20 代表最大既骨料用20mm)

100 同75 只係25mm slump 相差並唔多, 好難比較兩隻混凝土長遠有咩分別;

正確d 比較兩個concrete mix 應該比較 w/c ratio 有用d (但你又無講到), 如果w/c ratio 細d, 理論上個密度會高d, 咁應該durability 會好d, 但事實上最取決既係d 工人compact 得好唔好, 有無honeycomb, 而鐵既cover 夠唔夠.....

而通常mix design都會specify 左minimum cement content 係幾多kg/m3; 咁既然人地都做到呢個數, 無必要challenge 個mix 既properties 啦, 仲有PFA 用量, AAR.... 好多野要睇, 而理論上多d OPC, 個heat of hydration 會高d, 咁會多d shrinkage crack.......但你講到尾都只係45 concrete, 唔算高grade, 是旦la

要增加個slump, 可以用減水濟(water reducing agent/superplasticizer), 例如咩Daratard, KFDN, 最勁咪 advanced flow (ADVA)



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引用:
原帖由 風見 於 2010-10-14 08:36 PM 發表
45/20  75slump
45/20  100slump
2隻石矢有咩分別,slump75和100除左希和傑,仲有咩分別
2隻石矢壓core,會否因slump不同而lead有不同結果
簡單d講 75 slump 容易有黃蜂(鬥)過 100 slump 因為太乾石屎 workability 唔夠 石屎唔夠槳/起唔到槳
所以 多0左 air void  core出來石屎core  強度變得效弱  唔夠理想 所以 石屎廠 大grade 石屎(35以上果d) 普遍  slump 會大d(100之上) 費事成日肥



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45/20  75slump MIXID:123456
45/20  100slump MIXID:147258
雖然2隻都係同GRADE石矢,但MIXID吾同,所以會影響到壓CORE的RESULT?



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回覆 10# 的帖子

Nicely said. I also agree with joblessness and 史力加.
W/C does affect your strength. Usually it is 35% to 40%.
Too high slump might result in shrinkage and segregation.
In your case, either 4" or 5" slump don't make a huge difference in the field. When the concrete is on site I focus more on the age of the concrete, usually if it is more than 90mins from the Concrete Plant at the time of placement we will reject that load. American industry standard. Don't ever let the truck drive add water onsite. Big no no!

Usually no one will question the designer's specification on the Concrete. The Contractor should not have a problem submitting a mix design in accordance with the Contract Requirements. I think this is industry standard worldwide except in China correct ? In China , don't they use tofu with no rebar instead ?

What are you pouring (Slab, walls, or Columns) by the way? Slump requirements differs depending what you are pouring.







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我見識少, 未見過批積圖上有指定slump. 亦未見過 spec. 對不同element有指定slump.
slump應該係main con.按施工方法選擇的. slump與強度沒直接關係.

[ 本帖最後由 大陸工程師 於 2010-10-27 01:12 PM 編輯 ]



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