Creating our dwelling in the Philippines. Making certain concrete quality. This essay is about our experiences in the provinces. The uncomplicated availability of much better content in towns (thoroughly clean, graded, crushed stone, washed sand and even air-entrained “Ready Mix” concrete is a complete distinctive context and most of our responses really don’t utilize.
The previously mentioned image reveals the workers introducing material to the cement mixer making use of a “ponke”. The ponke is a picket box with handles. The within dimensions of the ponke are 30cm x 30cm x 30cm. The ponke is sized to maintain a person 40 kilo sack of cement. I questioned that the ponkes be designed and applied as a implies of managing the concrete mixture. The use of the ponkes tends to make it uncomplicated to get the combination right. Ponkes are hardly ever employed in the Philippines now, but formerly were being the norm. Now materials are far more normally measured working with empty cement sacks refilled with sand or gravel. Never ever use shovels to measure.
We wanted powerful concrete and a strong dwelling. After investigation, we made a decision on a quite robust combine of 1 component cement, two areas sand and three components gravel – a 1-2-3 combine, apart from for flooring exactly where we made use of 1-2-4. This also led us to buy a gas driven a single-bagger cement mixer, a gasoline run inside concrete vibrator and to stick with the 1-2-3 concrete mix. “One-bagger” suggests that the mixer is capable of accepting one 40 kilo (88 pound) sack. As a man or woman with neck problems, it would make me wince to see Filipino personnel carrying two 40 kilo sacks on their heads when we get a cement delivery! Extra on the mixer and vibrator at /developing-our-dwelling-acquiring-began/
Basic Chart of Concrete Mixes (hyperlink)
Cement : Sand : Gravel 1 : 2 : 5 for quality C15 (common objective concrete) = 2175 psi = 152 kg/m2 gen. 2000 psi 1 : 2 : 4 for grade C25 (robust) = 3625 psi = 255 kg/m2 typically 4000 psi 1 : 2 : 3 for grade C30 (really robust) = 4351 psi = 305 kg/m2typically 4500 psi
We have had a number of responses that our 1-2-3 C30 mix is wasteful overkill for routine residential construction — that a C20 or C25 combine would be additional than suitable. That would be true if you assumed that the appropriate elements and disorders to make C30 concrete have been possible if we had clear, sorted crushed stone aggregate, if we experienced excellent clean washed sand, if the mixes were perfectly combined and contained the right quantity of h2o and if in hot weather the freshly poured concrete was stored moist for a few times. If these items were accurate, then in truth the 1-2-3 combine is overkill. It’s our experience (admittedly minimal) that these situations rarely implement in the provinces. You might aim for C30 and close up with C15 or C20. If you intention for C15 you could conclusion up with who understands what.
We have been impressed to see how simple it is to demolish concrete properties in the Philippines. Partly it is the comfortable hollow block but it is also the weak concrete.
The concrete in the normal rural home might be 1-2-6 or even weaker. The gravel is not crushed. It’s from the nearest river mattress. There may be salt contamination, based where the gravel is dredged from. The gravel will not be clean up. The sand will not be washed. The blend is soupy in the excessive — no slump. Every appealing physical property of concrete that you can measure is adversely effected by adding much more water. This blend is applied with weak hollow block and as considerably rebar as the operator or builder cares or can afford to place in. What is the PSI? I shudder to believe.
The residence you get an already crafted residence it probably will not have these robust concrete. 1-3-5 is in widespread use. I have viewed deliveries of substandard reinforcing bar. In fact, when you purchase rebar you have to specify normal or you may perfectly get substandard automatically. A inadequately created residence might be created with a “class B” or “class C” concrete mix and not enough rebar. You’ll never know what is in your property unless of course you create it on your own. It may well never ever issue, but here’s a image of the church in close by Oton, Iloilo which was wrecked in the 1948 Panay Island earthquake.
The system of our house was made by a structural engineer. We tried out to be really strict in following the options. Sometimes great Filipino builders use classic rules of thumb not dependent on engineering essentials. This can signify far too a lot steel in areas which seriously really do not want it and not enough in spots that do.
At minimum in the provinces, the ambition to have high quality concrete for your job can direct to stress. My crew were being really hard employees, but accustomed to their ways of concrete design. The area gravel incorporates so considerably sand that the mix possibly ends up currently being 1-3-2 (one cement, a few sand and two gravel). The personnel like this sandy gravel mainly because it’s quick to operate with, flows conveniently into sorts. Using screened, washed, crushed gravel or stone would make more robust concrete. Make confident that the major aggregate you use will conveniently circulation into kinds and around and through the rebar. A massive stone can capture in the rebar and result in a void. See our submit on columns and beams for more information.
Striving to keep Philippine personnel from adding far too substantially water to concrete is a legendary challenge. They like to make soupy concrete for the reason that it flows easily and does not set-up promptly, it remains “workable” for a a great deal extended time than right concrete. If it does start out to set up, they incorporate far more h2o and re mix. We have browse that some on-internet site Filipino supervising engineers have been so disappointed with this difficulty that they just disappeared from the project web-site fairly than fight with the workers over this situation. I now recognize their trouble.
We pushed so really hard that it has triggered real friction with my crew. I would not allow any concrete to be blended until I was there to make sure it was not far too damp and that it stayed in the mixer for at minimum two full minutes. That appears like a short time, but the personnel were so anxious that they would dump it early if I was not there with my watch. I would not allow the addition of far more drinking water “re-tempering” the concrete. If the mix was also soupy or was setting up and would have them dump the batch. They were being really horrified by that. By the finish of the venture the crew realized particularly what we expected, but I’m guaranteed if we have been not there to supervise, they’ed do it their way.
So, listed here are our suggestions:
- Invest in a superior mixer. It will expense about P60,000 but you can market it when you are completed and recoup most of your dollars.
- Purchase thoroughly clean washed sand and crushed stone, at least for beams and columns.
- Invest in a inner vibrator. Research how to use it (url down below) and then educate your crew. It will cost about P20,000 but you can offer it when you’re carried out. We experienced no issues providing our mixer and vibrator.
- Unless of course you have a dependable foreman, be there whenever concrete do the job is accomplished.
- Make sure the new concrete stays moist 24/7 for a couple times. The extended the superior. Rice straw tends to make a excellent covering.
Obtain https://www.ccaa.com.au/imis_prod/files/ConcreteBasics.pdf “Concrete Basics” from the Australian Concrete business. It’s an great overview and involves a area on making use of concrete vibrators that we desire we had witnessed in advance of relatively than after construction of our residence. https://www.ccaa.com.au/imis_prod/files/ConcreteBasics.pdf
THIS is a much more technical but quite valuable PDF “Designing and Proportioning Normal Concrete Mixtures”