Concrete Ramp Block

In our flat's area there are 4 steps. We and our neighbours need to lift our bikes every time we pass upstairs. Unfortunately, the distance between the steps is similar to the distance between the wheels. This means if we want to lift justs the front wheel, it doesn't work as the rear wheel is blocked by the lower step.

Therefore I've decided to build some kind of ramp to allow bikes to be pushed up along the steps. I didn't want to build anything permanent and invasive. Instead, the plan was to build a movable ramp blocks, heavy enough so they stay in place anyway. If needed, they can be removed during winter.

In a first part of this instructable, I will present the success story. After that I will share my failed attempts pointing out mistakes and observations.

I strongly advise you to check the Concrete class. There are lots of information and good practices.

Materials:

• Plywood (or some other wooden material). I've used a 12mm thick plywood.
• Some screws or nails to assemble a frame (I've used screws)
• Concrete mixture - I've used a "ready to use" concrete mixture, a concrete class of C25/30 (old class B25)
• Water

Tools:

• Saw - I've used a circular saw
• Screwdriver/hammer
• Measurement tape
• Bucket to mix a concrete
• Drill and stirrer
• Trowel

In my case, the steps are 10cm high. A slope needs to be small enough to make lifting a bike easy. The ramp block cannot be too big (too long). After some checkings, I've picked a length of ~27cm what gives an angle to be ~21 deg. The width of the ramp is 15cm.

To build a frame for such a block we need 5 pieces:

• 1x bottom: 260mm x 174mm (174=150mm internal width + 2 * 12mm width of plywood)
• 2x sides: triangle with cut corner: 260mm (bottom) x 100mm (height) x ~20mm (cut corner)
• 1x top: 280mm x 174mm
• 1x front (part at cut corner): 174mm x ~30mm

The cutting is straight forward.

Attach as many screws as reasonable. Initially I've added 2 screws on each side. But concrete is really heavy. It means it may split the parts just by it's weight. So later on I had to attach 2 more screws to keep the frame in a shape.

On my 2nd attempt I've used a concrete of C25/30 class (old B25). I've measured the volume of mortar I needed. In my case it was 4.6kg of mixture + 460ml of water.

Then I mix it with a trowel and then with a dedicated concrete stirrer with a drill.

Applying mortar is just fun. Try to already push the mortar into the corners (improved anyway later by vibrating).

Check if the frame is strong enough to hold the mortar in place so there are no leakages.

Vibrating concrete is very important! It allows the mold to fill as much volume as possible. It also causes bubbles to bubble up to the surface so in the end there are much less "holes" in final result.

I didn't have a dedicated concrete vibrator so I had to use my hands and a hammer to move the mold as much as possible. In my case the vibration process was taking 15-30 mins.

As suggested in comments by TK Trooper and zap88, you can use any other tool which may cause the form with mold to vibrate. In my case I could use an electric sander which I have used later to finish the surface of the block. Try some other tools as possible options.

According to some advices I've read, these are some timings I was following:

• 24h - Keep the mold in the frame. After 24h concrete was hard enough to pull out.
• 48h - (since making mortar) After 48h concrete is hard enough so a person can walk on it. It's not allowed to put heavy things on it.
• 28 days - It's the time concrete needs to get its full strength.

After a block was pulled out from the form, it was hydrating further in a cellar. Then I could prepare another ramp block.

As you know, concrete doesn't dry but hydrate. This means it needs the proper amount of water for this process. If it dries too fast on the surface it may cause cracks. To prevent this you can water it a accordingly, or - as I did - wrap it with a plastic bag so the moisture inside is kept at the proper level (so concrete hydrates but doesn't dry). I kept a block for first 24h till the surface has became hard. (Thx pixel tamer for pointing it out).

Normally a ramp blocks can be easily removed from the frame. Some delicate smashes with a rubber hammer does the job and the block pops out from the frame.

Occasionally I had to unscrew the sides of the frame. On a last photo you can see the last 4th ramp where I disassemble the frame completely (as I didn't need a frame anymore).

I needed 4 ramps. Making one was taking 24h to pull out from a frame and then at least 24h for hydration process so it is hard enough to be able to stand on it.

For all 4 it took me about a week. 1st one was hydrating for ~5 days and the last one 2 days.

After making the last one I waited 3 more days so the blocks have became hard enough.

I've noticed that concrete "soaked" the colour of the wood in some places. I decided to grind it softly so the colour has became back light gray.

Also, I washed the blocks - just to remove some concrete dust.

Ramps work as expected. It helps a lot with lifting bike upstairs. I hope the colour difference will decrease as the ramp blocks become dirty.

Yes, it helps a lot. You can see how easy it is to lift bikes up through these 4 steps even by kids 🙂.

Below there is a list of mistakes and observations I've made on my attempts to build the ramp blocks.

First I've built a frame using MDF. First 2 blocks were relatively OK. But when I was making a 3rd one, I've noticed that the MDF has soaked too much of moisture from concrete and it has lost its shape. I had to rebuild the frame with plywood.

Of course a solid wood is one of the best options but it's also more expensive.

By a mistake, I've initially bought a concrete which was a fast-curing one.

And it is really fast! You have like maximum 5 minutes since applying water to mix it and put it into the frame. It's not enough time to do any adjustments. Therefore I was not happy with the final result.

Use the long curing/hydrating mixture - just take your time.

Using a plastic bag/foil sounds like a good idea to separate the wet concrete mixture from a frame. But the problem was obviously the corners. It was hard to shape the foil so that corners are straight and not rounded.

Also, plastic foil applies a texture of it in places where it bends which doesn't look nice.

It's up to you. If you have more experience with using a plastic foil - do it. It didn't work for me.

According to pixel tamer's comment, a better approach is to wrap each piece of a frame separately so there are no folds at the corners of the frame.

Instead of using a plastic foil, you can (thx pixel tamer and MaxB146 for comments):

• paint the inside walls of a frame,
• use a release agent,
• apply a non invasive oil to inside walls of a frame,
• use a plywood which is covered already with a plastic by manufacturer.

I guess it's a rule which everybody knows except me. But in general - avoid sharp angles.

Especially when bigger pieces of stones and sand are used. They may create empty spaces which may not be removed even by vibrating the concrete. After that, such a sharp angles are much easier to break off of the block.

Every angle should be maximum 90 degrees. If there is a need for a sharp angle, the best approach is to "cut".

Numbers on a picture:

1. Contains sharp angles
2. Sharp angles are just cut
3. If we want to make the ramp more steep, the cut can be done at the width of the original length of a ramp block.