What is the most cost effective way of purchasing the raw materials for making concrete for home construction. What is the biggest bag of cement available locally and how much do they cost? Is is best to have large piles of sand and gravel delivered or to just buy bags of these as well? How much does quality sand and gravel cost per cubic meter delivered?
Cement comes in a standard 40 KG bag. I heard yesterday that the price has gone up to P220 per bag, but I am guessing that you may find it a bit lower. There are different prices for different brands. I used Grand Pozzolan. It is cheaper than Portland and was told that the only difference is cure time. It is cheaper to buy sand and gravel by the truck load. your workers will put in bags as they use it to gert the proper mix with the cement. The small average trucks you see here hold 4 cubic meters. Sand will cost around P1000 per truck (4 cu mtrs) or more depending on where you live. Gravel varies depending on what you are buying. Large river gravel is the cheapest, maybe P1600 per truck, but crushed stone will cost over P2000 per truck. The cement will grip to crushed stone much better than to the smooth river gravel so your concrete will be a lot stronger if you use the crushed stone. The only place I used river gravel when building my house, was backfilling under my ground floor but I know some that use it throughout their construction. Noting that we are in the ring of fire and subject to the occasional earthquake, I think the extra few pesos is a small cost compared to the benefit. For current prices (prices may have increased significantly sine I bought mine due to the increase in fuel costs and the increased demand created by the flood and earthquake) try Felixberto Sand and Gravel located between Bacong and Valencia at 09208343404 or 09263359781. Their prices include transportaion if you are in their general area (I am in Valencia and did not pay additional transportaiton costs). There are lots of places selling this stuff so shop around before buying. You could easily use 40 to 200 cubic meters of sand in your construction and maybe a similar amount of gravel. For structural concrete you will probably use Class AA, 1 cement - 2 sand - 3 gravel, but some use Class A, 1 cement - 2 sand 4 gravel. Some mix by hand with shovels but I suggest renting a concrete mixer (1 bagger). The mix will be more stable, thus stronger. Be sure to keep the water content to a minimum. Your workers will ALWAYS try to put too much water, drastically reducing the strength of your concrete. When building columns, make sure they they constantly prod the mix they are pouring into the forms to prevent voids. You can buy or rent a vibrator but it can also cause problems if you vibrate too much (the cement and water will separate and run out of the forms). Good luck.
Let me add, if the rebar work is done right than there will be a lot of rebar. A vibrator is essential for getting the concrete to flow into and around the rebar, especially in the corners. Without the vibrator your beams and columns could look like Swiss cheese when the forms come off. So, even if you don't use a vibrator for the whole job, have one on standby just in case it's needed. The time to rent a vibrator is before you do the pour.
Correction on cement prices. I just went by santa Rosa Lumber and they are selling Grand Pozzolan at P205 and Portland at P212.
