Hand mixing

Almost everything that needs to be said about concrete, cement, hand-mixing, uses and prices has been said on this forum. Please check out the contributions before posting new questions.

Moderators: Sometimewoodworker, MGV12, BKKBILL, pattayapope

Hand mixing

Postby Nawty » Tue Apr 08, 2008 3:14 pm

By hand mixing I mean using an electric or motor powered cement mixer, not the black tub with a hoe and a bucket of water.

I know that the hand mixing method is signifigantly cheaper than the ready mixed cement, from my calculations a year or more ago it was around half the price.

I also know that if mixed properly either by competent staff or supervised constantly by competent staff, it can be at least as good as ready mix with the added benefit of knowing what 'actually' is in the mix. Especially when requiring additives etc.

My questions is, the complete hand mixing for a house involves a lot of cement to be mixed and the time to mix each load etc. Does pouring continious beams, slabs, posts etc have any detrimental effect being done this slowly, whereas the load just poured is waiting some time for thye next to join it.

I do not think the time between pouring one load and the next would/should be that long, certainly not long enough to set, but just wondering if there is an optimum time here to avoid cold joints etc.
User avatar
Nawty
 
Posts: 804
Joined: Mon May 07, 2007 12:23 pm

Postby dozer » Tue Apr 08, 2008 6:52 pm

There is a good related post here that has price info

http://coolthaihouse.com/forum/viewtopic.php?t=672&start=0&postdays=0&postorder=asc&highlight=

Here is a portion with recent price info that I wrote up in Feb 2008. It is very accurate and takes in consideration all aggregates. The upshot is, the hand mix is only 25% cheaper.:

Here's an update of proportions of stone/sand/cement in a recent ready mix CPAC pour (nok brand):

Per one cubic meter of 280 KSC at 1600 baht/meter contains:
STONE: 1040 kilograms
SAND: 940 kilograms
CEMENT: 325 kilograms
(If you order ready mix and request 'QC' (quality control) they will come and do various tests on the concrete and tell you the exact mix of materials. They do an on-site slump test and take a sample to confirm a compressive test after it is dry. All free).

KSC = Kilograms per square centimeter. This is the amount of compressive weight a one centimeter cube can support. Same meaning a steng.

Pricing out the individual components in a SELF MIXED concrete of same proportions yields:
CEMENT: brand Nok portland. 6.5 bags @ 130 baht = 845 baht
STONE AGGREGATE: Cost = 4200 per 10 Q or .1748 per kilo. 1040 kilos x .1748 = 182 baht
SAND: Cost = 2200 per 10 Q or .1511 per kilo. 940 kilos x .1511 = 142 baht

Total material price for self mixed = 1169 baht / cubic meter
Total for ready mix = 1600 baht / cubic meter


You can see that the self mixed price is almost 75% of the pre mixed price (making it an even better deal than previously posted when 50% was assumed). THIS DOES NOT include labor.

Quality wise the ready mix is the way to go. See my note about QC above as to verification of the delivered product.

The fact that the pour is contiguous the finished cement slap will bind together and be of overall higher quality. Of course it is only practical where there is a large quantity to be poured such as for a slab or walk way.
dozer
Site Admin
 
Posts: 1940
Joined: Tue Mar 15, 2005 4:21 pm

Postby Nawty » Wed Apr 09, 2008 8:38 am

Am I reading something wrong ?? Dont understand what you said here

"You can see that the self mixed price is almost 75% of the pre mixed price (making it an even better deal than previously posted when 50% was assumed). THIS DOES NOT include labor. "

If it is only 25% cheaper then this does not make sense.

Also I am talking about Bkk prices where it is much more expensive for ready mix and therefore does equate to a very rough half price I think.
User avatar
Nawty
 
Posts: 804
Joined: Mon May 07, 2007 12:23 pm


Return to cement, concrete and mortar

Who is online

Users browsing this forum: No registered users and 1 guest