kasi sejuk dulu mata tinguk tumbuhan hijau tumbuh atas concrete ni~~
ok!
this is boring! assignment..
Terpaksa la juga buat kan..
tajuk dia
-THE TEST OF THE CEMENT FOR THE SOUNDNESS AND SETTING TIME-
okay~
mau copy internet ja ka atau pahamkan betul2??
boring ba ui!
suda la aku budu english! iskh!
mula2...
aku mau kasi tau! kau! kau! dan kau!
Sifat-sifat Fizikal Simen
1. Menetapkan Masa (Setting Time)
2. Kekukuhan (Soundness)
3.Kehalusan (Finess)
4.Kekuatan (Strength)
so, dalam Assignment ni, kena suru cerita pasal Ujian2 yang dibuat untuk menguji simen tu punya properties yg pertama dn kedua tu.. iaitu, 'setting time' dan 'soundness'
betul la ba tu kan?? huahuahua
okay!
Setting Time (Vicat Apparatus)
Penetapan masa simen dipengaruhi oleh beberapa perkara iaitu, kehalusan simen, nisbah air simen, kandungan kimia dan bahan tambah!
k. Test dia ni, dibuat 2 kali..Initial dan Final..
mau video ka? mau ka? mau ka? huahuahua
Initial Test (Set Awal)
Final Test (Set Akhir)
Procedure Buku Teks mintapuji jg mau dilampirkan sini! ok
Procedure to determine initial and final setting time of cement
i) Prepare a cement paste by gauging the cement with 0.85 times the water required to give a paste of standard consistency.
ii) Start a stop-watch, the moment water is added to the cement.
iii) Fill the Vicat mould completely with the cement paste gauged as above, the mould resting on a non-porous plate and smooth off the surface of the paste making it level with the top of the mould. The cement block thus prepared in the mould is the test block.
A) INITIAL SETTING TIME
Place the test block under the rod bearing the needle. Lower the needle gently in order to make contact with the surface of the cement paste and release quickly, allowing it to penetrate the test block. Repeat the procedure till the needle fails to pierce the test block to a point 5.0 ± 0.5mm measured from the bottom of the mould.The time period elapsing between the time, water is added to the cement and the time, the needle fails to pierce the test block by 5.0 ± 0.5mm measured from the bottom of the mould, is the initial setting time.
B) FINAL SETTING TIME
Replace the above needle by the one with an annular attachment. The cement should be considered as finally set when, upon applying the needle gently to the surface of the test block, the needle makes an impression therein, while the attachment fails to do so. The period elapsing between the time, water is added to the cement and the time, the needle makes an impression on the surface of the test block, while the attachment fails to do so, is the final setting time.
Oky. bila masanya Set Awal dan Set Akhir ni dibuat??
Set Awal dibuat masa tu simen start2 atau mau2 suda keras..
Set Akhir pula dibuat masa tu simen sudah keras dimana dia boleh suda menampung beban yang sikit2 jak la.. jgn berat yang mati juga berat.. hehehe
ni lah alat yang di guna utk buat tu test..(lebih jelas dr video) -Vicat Apparatus
upps. sebenarnya test ni bukan guna Vicat Needles jak.. boleh juga guna Gilmore Needles, cuma Vicat lg bagus lah! dan selalu diguna!
Kawalan Suhu! itu penting!
haba yang dikaluarkan dalam proses pengisaran menyebabkan gypsium (CaSO4.2H2O) kehilangan air, membentuk bassanite (CaSO4.0.2-0.7H2O) atau y-anhydrate (CaSO4.~0.05H2O). Mineral yg kedua cpt larut, kira2 2% dr dlm simen diperlukan untuk mengawal penghidratan tricalcium aluminate hydration.
kalau lebih drpd jumlah tu terbentuk, ia boleh menyebabkan
False Set !
copy ayt skema!
False Set -Loss of plasticity shortly after mixing – little heat
- Due to hemihydrate (Plaster) in cement –hydrating to Gypsum
- Workability restored by additional mixing
Flash Set - Rapid & early loss of workability – significant heat
- Due to rapid reaction of aluminates – when insufficient sulfate present
-Workability cannot be restored
jagan blur dulu! belum habis! huahuahuaauahaasuy
Soundness (Le Chatelier Apparatus)
Tujuan ujian ini adalah untuk memastikan konkrit yang telah siap tidak mengalami perubahan yang besar pada isipadunya kerana ini akan menyebabkan keretakan dan pengembangan yang tidak wajar dan akhirnya menyebabkan kehancuran konkrit!
eleh, ayat senang! untuk pastikan simen yang diguna tu teda ability untuk mengembang dan kembang dan kembang dan kembang lg...macam obesity la...
Kekukuhan simen ditentukan dgn mengunakan radas Le Chatelier yang terdiri daripada 'split cylinder' diperbuat dr tembaga atau logam(yg sesuai)!
ni cylinder di ats ni, 3mm diameter dan, tinggi pun 3mm ok! pemegang dia tu pula 165mm.
Procedure! (yang boring)
1. Acuan diletakkan diatas kaca2...
iskh.. malas bah.. kasi video la!
huahuahua.. bukan pemalas ni.. rajin suda ni. :P
oklah! oklah! anak sapa la tu, mau juga skema buku teks..copy jak la!
PROCEDURE
i) The mould is placed on a glass sheet and it is filled with the cement paste formed by gauging cement with 0.78 times the water required to give a paste of standard consistency.
ii) Then the mould is covered with another piece of glass sheet, a small weight is placed on its covering glass sheet and immediately the whole assembly is submerged in water at a temperature of 27 ± 2oC and kept it there for 24hrs.
iii) The distance separating the indicator points to the nearest 0.5mm is measured (say d l ).
iv) The mould is submerged again in water at the temperature prescribed above.The water is bought to boiling point in 25 to 30 minutes and it is boiled for 3hrs.
v) Then the mould is removed from the water, allowed to cool.The distance between the indicator points is measured (say d 2 ).
vi) (d 2 – d l) represents the expansion of cement.
okay! sekarang cerita pasal, apa sebab simen tu x kukuh! (unsoundness)
1. Bila terdapat lebihan kapur dalam simen.
2. Bila simen x cukup kena bakar.
3. Tu kisaran x berapa mau halus atau percampuran bahan mentah yang tidak seragam.
4. Bila kandungan magnesium dalam simen tinggi, macam si apal
5. Ditto ditto calcium sulphate ditto ditto.. hahaha (biar aku ja paham)
Ujian ni mesti dibuat awal2 simen dibancuh dengan bahan2 lain..paham juga kan sama apa dia dibancuh..mestila aggregate dan bagai.. x kan juga milo atau nescafe atau nestum.. k
okay, sekarang! macamna untuk mencapai kekukuhan simen yang baik dan hensem mcam johnny depp??
begini!
1. Kandungan ibu mengandung magnesium dihadkan kpd 6% sahaja.. (bayi adalah lelaki.tahniah!)
2. kandungan calcium sulphate ditambah kpd clinker semasa mengisar untuk mengelak daripada flash set of cement . (budu, aku pn x paham)
3. Kuantiti gypsum dalam simen semasa pembuatan simen berbeza dr 3%-5% bergantung kpd kandungan C3A..
-__-'' apa la aku belajar ni
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