Pouring Concrete

Saturday, Jan. 18, 2014

Today I faced up to the challenge of mixing and pouring concrete.  This is the first time I have tried doing anything with concrete beyond setting fence posts.  But the project was small enough that I didn't feel apprehensive about it.

Today's objective was to build a concrete footing, 5 and 1/2 inches wide and four inches deep, on the south side of the basin, even with the top of the basin wall.  I had bought the concrete mix, Quikcrete, the previous weekend, had built a form for the footing, and laid four inches of sand as a base.  All that remained was to mix the concrete and place it into the form.

I used a wheel barrow to mix the concrete, one 50 pound bag of Quikcrete at a time.

I didn't dare just pour the concrete into the form from the wheel barrow.  I used a shovel, and placed one shovel full at a time into the form, trying to fill the form evenly up to the top.

Following the advice of my concrete book, I used the shovel to work the concrete mix into the space under the rebar, attempting to fill the form evenly, and used a small piece of wood to "screed" the excess from the top.  Also tapped the side of the form with a hammer, which the book says "draws finer aggregates in the concrete against the forms, creating a smoother surface on the sides."

Here I have finished placing the concrete mix, and "bleed water" is starting to appear.  Again quoting the book, "Timing is the key to an attractive concrete finish.  When concrete is poured, the heavy materials gradually sink, leaving a thin layer of water--known as bleed water-- on the surface. To achieve an attractive finish, it's important to let bleed water evaporate before proceeding with the other steps."

The next step would be to smooth the surface with a "float", a tool that is essentially just a flat piece of wood with a handle.  It was already getting dark, and I needed to wait for the bleed water to evaporate, which takes an hour or two, but I couldn't wait until the next day.  By the next morning the concrete would be set and impossible to smooth.

I set up work lights, and did the float work well after dark.

Sunday, Jan. 19, 2014

The smoothing did not turn out very good.

I would not want a sidewalk that looked like this.  But, fortunately, this concrete will not normally be visible.  Apparently there is some real skill involved in producing a nice concrete surface.

Another Concrete Form

Saturday, Jan. 11, 2014

When the catch basin project is finished, there will be a patio with brick pavers on the both sides of the deck.  The pavers will be even with the top of the deck, so that the overall surface is level and smooth.  But the pavers cannot abut the deck on the left side in the photo below, or I would not be able to raise the deck sections.  I need a channel, with width and depth equal to the thickness of the deck, for the deck sections to go into when they are raised.

The channel will have to be open in order for a deck section to be raised, but should be closed normally, so that there is a smooth surface from the deck across the channel to the pavers.  I spent a fair amount of time thinking about how to handle this.

The solution that I decided on was to fill the channel with wood.  A thick wooden beam beside the deck could provide a solid stable surface, level with the deck, but could be removed to provide the open channel necessary for raising the deck sections.  In the photo below, I am trying out this idea with two 4x6 beams, each seven feet long.  I think the beams are heavy enough to provide a stable surface without being attached to the basin, but light enough to be lifted out when I need to raise the deck sections.

A problem was that the hinges protrude about a quarter of an inch from the basin wall, preventing the beam from closely fitting against the deck section.  I solved this problem by cutting a small strip out of the beam.

I originally though that cutting a strip out of the beam would be a difficult (or impossible!) task with the tools that I have.  But then I discovered that the cutting depth of my Skill saw is adjustable.  (Maybe I should have read the user manual when I bought it!)  By adjusting the blade to cut the required depth for each side of the strip, I was able to make a single cut along the full length of the beam in each dimension and remove the strip.  It turned out to be surprisingly easy.

To exactly accommodate the deck sections, the channel needs to be five inches in both width and depth. The width of the 4x6 beam (five and one half inches) matches the needed width with with half an inch to spare.  But, unfortunately, the thickness (three and one half inches) is too small.  With the beam sitting at the same level as the base of the deck sections, it only comes up to the bottom of the deck planks, not to the top.  

I plan to solve this problem by placing a plank of the same thickness as the deck planks on top of the beam.  I will attach this plank firmly to the beam, producing the effect of a beam that is five and one half inches square.

The next problem was that I need something to prevent dirt from falling into the channel when the beams are not in place.  (The same problem that I had to deal with on the other side of the basin.)  I need a fixed barrier, with its top even with the surface of the deck, to act as a tiny retaining wall.  This barrier will form the left wall of the channel.

My first idea was to use strips of concrete board, which is sold as the backing material for the tile in shower stalls.  The concrete board comes in sheets three feet wide by five feet long.  I bought two sheets and cut them in half along the length, producing strips 18 inches wide and five feet long.

The plan was to simply embed these strips in the dirt beside the channel, making the top of each strip even with the top of the deck.  This required digging a trench beside the channel.  I would place the strips of concrete board in the trench, snug up against the beams, and back fill with dirt to hold them in place.

Unfortunately, I could not get the concrete board strips to align with the top of the deck.  It seemed that I needed something more solid than dirt to hold them.  I also worried that even if I could get them aligned initially, they would not stay aligned.  So I lost confidence in this plan.

Plan B was to put a concrete footing under the channel and attach the retaining wall to the footing.  I had considered this plan previously, but rejected it as too much work.  Now it seemed like the right solution.

Building the concrete footing seemed like a small enough project that I could do it myself (unlike the basin.)  Build a form.  Mix Quickcrete by hand in a wheelbarrow, and shovel it into the form.  A good learning project.

Sunday, Jan. 12, 2014

According to my concrete book, a slab should be at least four inches thick in order to avoid cracking.  The footing should be at least five and one half inches wide to match the width of the beam.  And it would be 14 feet long.

The concrete book recommends putting three inches of sand as a base under a footing. 

I computed the amount of sand I would need for the base and the amount of Quickcrete I would need for the footing and set off to Lowe's.  I came home with five 50 pounds bags of sand, seven 50 pound bags of Quickcrete, and two 10 foot lengths of 3/8 inch rebar.  Also, eight widgets to support the rebar two inches above the sand base.

I removed the beams that were beside the basin, and dug a trench down to seven inches below the top of the basin.  I tried to make the depth as accurate as possible, as it would determine the amount of sand that would be beneath the concrete.

Next I needed to build a form for the concrete.  I had some scrap wood from shelves in the garage that I replaced some time ago, which was suitable for making the form.  (Packratism pays off again!)  I cut the boards to a width of seven inches and installed them in the trench that I had dug beside the basin.  I used small strips of wood to hold the form five and one half inches from the basin and back filled with dirt to hold the form in place.  I used short pieces of 4x6 to make the ends of the form.

I filled in three inches of sand as a base for the slab, leaving four inches to top of the form.  Filling the form with concrete would produce the four inch thick slab.  The top of the slab would be even with the top of the basin and bottom of the deck.

By the time I finished with the sand, it was getting dark, and I was getting tired.  Mixing and placing the concrete would have to wait until the next weekend.

Progress Report

Dec. 19  The four deck sections are in place now, ready to stain.

Dec. 20 I have applied stain to the exposed wood.

For the record, I used Olympic Maximum Stain + Sealant in Canyon Brown.

Dec. 28  When the deck and adjoining patio are complete, the patio pavers will come up to the deck, covering the space to the right of the deck in the picture above.  The tops of the pavers should be even with the top of the deck, forming a smooth, level surface.  But the deck sections are movable, hinged on the left side.  When a deck section is raised, there will be a five inch drop from the patio to the concrete basin wall.  What will prevent the pavers and the dirt below them from sloughing off into the basin?  This has been one of the toughest design problems of the project.

I considered several alternatives, none of which seemed entirely satisfactory.  I finally decided to attach a stationary board to the top of the basin wall.  The basin wall extends about an inch and a half beyond the edge of the deck sections, just enough space for a 2x6 to sit between the deck sections and the patio.  (The actual dimensions of a 2x6 are 1.5 inches by 5.5 inches.)

The next question was how to attach the board to the basin.  Again I considered several alternatives, constrained by what material is available at Lowe's and Home Depot.  My first choice was aluminum angle stock, which would be easy to cut and drill, but strong enough to hold the board against the pressure of the dirt and pavers, and not subject to corrosion.

The problem with this solution is that with one side flat against the basin wall and the board, the other side would stick out and be in the way of the pavers.

The hardware stores have strips of perforated galvanized steel, one eighth of an inch thick, thin enough to be cuttable by hand with a hack saw but fairly strong.  This is appealing because the fastener would not interfere with the pavers.  And I would not have to drill holes for the screws.

I decided that this would be a better solution and actually started to use it.  I cut three strips eight inches long and attached one board to the basin, using heavy lag screws into the board and Tapcons into the concrete.  Unfortunately, the attached board felt flimsy.  The flat steel strip is strong, but does not provide much resistance to bending.  So, back to Plan A.

I cut and drilled seven strips of the aluminum angle stock and used them to fasten the boards to the basin, as shown below.  With the aluminum fasteners, the boards felt absolutely rigid.  I will just have to deal with the problem of the fasteners sticking out from the board and basin.  Maybe cut a slot into each paver that needs to fit against a fastener.

Meanwhile, on Dec. 23 I had a job interview with Geographical Solutions in Palm Harbor, and got a job offer from them the same day, which I immediately accepted.  I started the new job on December 30, which is going to seriously interfere with the catch basin project.