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Concrete And Mortar: Laying Concrete Hollow Block

Concrete and mortar: The start of the fence

This article is part of a series on how we built our concrete hollow block fence or wall in the Philippines.
More information can be found here: Perimeter Fence Philippines: Index

We’ve covered a lot of ground in this series on how we built our concrete fence in Davao City, Philippines.

This post will include a look at the concrete hollow block (CHB) laying, the mortar and concrete mixes and the Filipino method of making “concrete sandwiches”.

Concrete And Mortar

Separate, Unequal

In case you don’t know, concrete and mortar are not the same. Concrete is aggregate (gravel), sand, cement, and water. Mortar is sand, cement, and water. The ratio of water to cement is higher in concrete than in mortar. Simply put, mortar is thicker. But it is also less structurally strong. It’s meant to hold stronger structures together (concrete hollow block, for example).

Concrete block fences and the walls of concrete block houses in the Philippines are constructed from (usually 4-inch) hollow blocks that are mortared together. Masons set pieces of deformed bar (Rebar) within and between the blocks, vertically. In our case, there are also horizontal lengths of rebar between certain rows of blocks that tie into the rebar in the columns. The blocks are filled with concrete and covered with a couple of inches of mortar on each side. It’s like a cement “sandwich”.

What We Got

We had complained previously to the architect about the consistency of the concrete mix used to form the columns and the wall footer. We told the foreman that we expected concrete in the voids of the block and not mortar.

What we got is what most home builders get: questionable mortar between the block with questionable concrete (and often mortar) used in the block voids.

Concrete and mortar: Lonely pile of mortarWe covered the questionable concrete mixing a couple of posts ago. The mortar mix contains the same guesstimated amounts of cement-to-sand and then too much water. Like the concrete mix, the laborers just add more water if the mortar starts to set up before it’s used (like at left where they made a batch and walked away).

When we arrived that first morning, it was clear that the crew had not been mixing concrete to use in filling the voids. The masons used the same mortar that they used between the block.

Concrete and mortar: Filling the block voids wrongOnce everyone knew that we were on site, the laborers began mixing batches of concrete along with batches of mortar. Even then, the masons only used concrete to fill the voids if the laborers were also mixing it for other sections of the fence (where they continued pouring columns and footers). If the laborers fell behind in mixing concrete because of the demand, the masons used the mortar mix they already had (as in the image at right). So the blocks in our concrete fence are, in some places, filled with concrete and in others with mortar.

Fixing Mistakes

Concrete and mortar: Wall height mistakeThere are mistakes made on every construction job. But in the Philippines, the fixes can make you shake your head.

At left is a mistake. Either the laborers dug the footer trench in this section too deep or the masons poured the footer too low. The masons “fixed” it by using about four inches of mortar. Then they added their block atop the fresh mortar. Any compression of the thick mortar layer would be “fixed” again later by adding more mortar or block to the top row. Argh!

If the masons had used concrete and let it cure, I wouldn’t have been upset. But they didn’t. They just slapped row after row of block on top.

To top it off, one of the “old timers” on the crew told us that the new laborers, hired off of the street, weren’t using enough cement in the mortar mix. He claimed that he’d tried to tell them but that they wouldn’t listen to him.

Concrete and mortar: Sloppy block workThe architect got an earful from us. We complained about this 4-inch mistake. We relayed the “old timer’s” complaint about the cement. We complained (again) about too much water being used in the concrete and mortar mixes. Another complaint was how sloppy the work was (see right). The site foreman was covering more than one job and was only on site twice a day to supervise some experienced workers and common laborers. We complained about that, too.

Enter the Drama Llama

The result was my first taste of Filipino melodrama. The architect replied that the cement and water ratios for the concrete and mortar “must” be correct. What looked like sloppy work was standard and would be “fixed later”. He had a personal reputation to protect, after all. His loyal workers had hungry children to provide for so they would never skimp on cement ratios or add too much water. On he went. I could almost hear violins.

To an American, this appeal to reputation, honor, and family was a ridiculous reaction to a complaint about the lack of work site supervision and consistency of materials. This is how it is in the Philippines, though. You have to understand this.

You must also understand that you will never change a method used by a Filipino with reasonable explanations. You can explain about concrete “slump”, mix ratios and whatever else you may know about construction stuff and all it will get you is a polite period of attention.

There was no way to discuss our concerns with the man and things did not improve (they worsened). We switched to taking photos to document everything that we thought was wrong. After a few run-ins of this nature, we ultimately decided to not use the architect’s crew to construct our house.

I hope you enjoyed this article, Concrete And Mortar: Laying Concrete Hollow Block, in our concrete block fence series. If you have any comments or questions, I hope you’ll use to Comments section below.



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