Both formwork was left for 23 days before deshuttering.. No form release was used. The dark color is of deformed bars spaced at 150 mm c/c.
Yes, the structure is a transverse slab...
We think it is a cold joint which probably occured after fresh concrete was poured on a very small layer of dry...
The second picture was missing... please check this pic of spallinghttp://files.engineering.com/getfile.aspx?folder=8db0b60f-0e1d-439b-b1ad-8d68c90161fc&file=10102011066.jpg
Hi,
We have observed spalling of concrete upon de-shuttering the soffit formwork after 25 days. The concrete slab is 2.0 meter thickness and was poured using 45 Mpa mix with 35% flyash to meet heat of hydration requirements as the thickness is 2.0 meters.
Test cylinder samples have achieved...
Thank you for your valuable comments. The pic is not from my other recent post. This concrete was casted a month ago using static pump. The slump ex-pump was 100-120mm. You are absolutely right that these cracks could have been closed while they are still plastic, but masons keep complaining...
Hi All,
Please classify the crack shown in the uploaded pic. Other data is as below,
1. Concrete grade 45 Mpa (490 Kgs cement)
2. Pumped @ 100 meters
3. Initial water curing not done. Curing membrane was applied late.
4. Slab thickness 40cm & 70cm.
Also recommend measures to control such...
SLab is 300mm thick..A superplasticizer was used Conplast SP430R @ 2% by wt of cement. Cement content is 490 Kgs/cum.
No retarder was used...The crack is still not inspected from the bottom as shutters will be opened after 14 days... We hope it is not thru-n-thru crack.
The concrete is normal weight. Slump measurement was taken ex-truck and then pumped by placing boom.
What shall be the sequence of finishing operations immediately after pouring?
When shall the water be sprinkled? When the concrete did not attain its initial setting (upto 3-4 hrs) how can the...
Hi All,
We have a situation where early shrinkage cracks occured after 1-2 hours of the concrete was placed. Enclosed are the pics of these cracks. The grade of concrete is 45 Mpa (flow upto 600mm) and was pumped up 16 storeys by placing boom. Ambient temp was 41 deg centigrade max.. concrete...
Loading rate, calibration was verified before testing and found okay. samples were cured in laboratory conditions. Mix has 5% silicafume, 35% PFA (Type F), and remaining Type I OPC. Microslica with HRWRA will get us initial strengths in PFA based mixes, but why is later strength gain is...
Hi All,
We tend to ignore the volume of heavy rebars in any structure while ordering the concrete. Given that the yield of the concrete is allright, there remains some difference between theorotical quantities ordered (based on the dimensions from the drawings, offcourse) and the actual...
I got shocker of my life to know the compressive strength @ 60 days of a 45 Mpa mix containing 35% replacement of cement with PFA (Type F C618) and about 5% of microsilica C1240, to be almost equal to 28 days strength. Only minor increase of 2 Mpa has occured @ 60 days.
I reckon the cause to be...
