Q&A / 

Concrete in a Bag and Heat Pumps

concrete in a bag

You may think that concrete in a bag is inferior. It’s not. (C) Copyright 2018 Tim Carter

Concrete in a Bag

Question #1: Hello Tim. This summer I’ve got a few outdoor projects that involve pouring small amounts of concrete. I looked into having a ready-mix truck do it, but the cost is so expensive. I’ve seen the bags of concrete in stores. Is it any good? Have you used it? Can I modify the mix to increase the strength? If so, what do you use and how? Malcolm McC., Albany GA

Do you have exciting project plans like Malcolm’s that involve concrete? I can clearly remember my first experience working with this magic material. I formed and poured a large set of steps that led up to the front door of the first house I remodeled. Looking back, it was too big a project for a rookie. That said, the job turned out not too bad!

The good news is the bagged concrete you can buy at local hardware stores is a fantastic product. The man who invented it built his first plant just a few miles from my childhood home in Cincinnati, OH.

It’s important to realize that basic concrete contains just four ingredients: small rocks, sand, Portland cement, and water. The cement is the glue or binder that holds the sand and rocks together. When water is added to the other three ingredients, it starts a chemical reaction. Countless invisible Portland cement crystals start to form and interlock all the sand and rock together. 

I’ve used bagged concrete for years and had great success with it. My two most recent uses were for the in-ground piers that support a massive deck and the piers for my giant two-story shed. The piers are going to last for many decades because I used the right amount of water to mix the concrete. Add too much water and you’ll ruin the concrete.

You can add more Portland cement to bagged concrete to make it stronger. You can also add some hydrated lime. To make the strongest concrete, the sand should be sourced from volcanic lava that has a high silica content. This is not easy to locate and I’d not worry about it. But you should get a bag of pure Portland cement and lime and add some of those two things. Both ingredients are inexpensive.

Most bagged concrete comes in standard-sized bags. If I wanted to make it stronger, I’d take an old kitchen measuring cup and add 16 ounces of Portland cement and 8 ounces dry measure of hydrated lime to each bag of concrete.

You want to blend the extra cement and lime with the bagged concrete in dry form. Use a newer plastic mixing bag and roll around the dry ingredients before adding the needed water. The concrete should have a consistency like stiff applesauce when you add the correct amount of water.

I’ve got many other bagged concrete tips and videos showing the magic plastic mixing bag at my AsktheBuilder.com website. Just go to: http://test.askthebuilder.com/working-with-concrete-in-a-bag/

Heat Pumps

Question #2: I’m about to put an offer in on a home that has a heat pump. I don’t understand how this machine could possibly produce heat in the winter months using air from outdoors. My friends are warning me that the air that comes out of the indoor registers is a cold heat. What does that mean and do heat pumps really get heat from cold air? Sue W., Orlando, FL

You may be like Sue and wonder about heat pumps and how in the world they work. It’s true, they can squeeze heat from the cold air. It’s all about the boiling temperature of the refrigerant that’s kept at very high pressure inside the heat pump and the copper lines that connect it to the indoor air handler.

The dirty little secret most HVAC people don’t tell you is the heat pumps also come with large electric resistance heating coils inside your home. As the temperature of the air drops outdoors and approaches 32 F, the heat pump needs help creating heat and electricity starts to flow through these coils making them glow just like a toaster. It’s common sense that as the outdoor air gets colder, there’s less heat to extract from it.

Heat pumps do a fantastic job of getting heat from the outdoor air if that air temperature is in the 50-55 F range. Technology is constantly making the machines more efficient so they produce more heat from a given amount of electricity.

The temperature of the air flowing out of the supply registers in the home will seem cold. Often the temperature of the heat-pump air is 90 F or less. Homes that heat with natural gas, propane, oil, or wood can see air temperatures of 110 F or even greater. This is why as a kid I used to put my feet right on top of the register in our living room. The metal got so hot I’d have to lift my feet every few minutes so I’d not get burned!

I’ve got lots more facts about heat pumps and great videos showing exactly how they work for you.  Go to: http://test.askthebuilder.com/heat-pumps-how-well-do-they-work/

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