Can I buy concrete mix online? - Building Materials

Unlikely salt damage - most likely the concrete was an inferior mix or was badly laid or both and there has been some water ingress with resulting frost damage.

It can be successfully patched but the trouble with patching concrete is the repair has to have a feather edge and concrete doesn't feather edge well and a cement feather edge doesn't age well at all.

To overcome this fairly common problem there are a variety of dry and ready mixed compounds designed for concrete repair that are variously reinforced with resins and/or fibres. They are convenient but quite pricey.

I prefer to use the old fashioned method and overcome the problem of the feather edge by chiseling out more of the original concrete to make a stepped edge at least an inch deep and to make the cavity a fairly even depth of at least an inch deep leaving only good secure concrete behind.

Once the cavity is prepared and free of dust, using a good quality pva adhesive, brush it well into the repair area including the stepped edge and mop out any surplus. Mix enough concrete for the patch using a suitably sized aggregate of 1/2 - 3/4 inch and add a little pva to the mix according to the instructions and fill the cavity, tamp well down, screed off level with the surrounding area and trowel the surface to a similar finish to the original.
Further brushing or trowelling might be needed later.

Concrete is a fabulous option for patios, sidewalks, and driveways. But, there can also be issues surrounding it. With the passage of time, holes and cracks may develop on the surface. Not to mention the devastating effects climate change or severe weather conditions can have. The good news is that you don't need to replace the whole surface! Cracks, chips, and holes can easily be fixed by a licensed professional. Even better: there are some things you can do, too, to protect your investments and avoid major concrete repairs. Check the attached link.

Concrete is normally estimated in cubic metres
Convert all figures to metres and multiply
3 x 3 x 0.125 = 1.125 cubic metres
Plus 10% for shrinkage = 1.24 cubic metres
10 bags cement
0.7 cubic metres sand
0.86 cubic metres of stone
All assuming you want a strong mix

Try concrete-mix

Figure 1 90 lb. bag per square ft., 6" deep.
Don't forget sand to grade and rebar to reinforce.
You probably won't find enough guys to mix all that concrete, so you'd really be better off hiring a concrete truck.
Tip: It's best to over estimate a little so you won't be caught short.

Put timber framing around the area, secured with pegs on the outside. Pour in concrete, and level with a timber plank used edge on resting on the timber surround.

You won'tfind concrete picnic tables in many regular furniture stores. But there are lots ofonline stores that sell them. Here's one site that I came across http://www.theparkcatalog.com/picnic-tables/concrete-picnic-table

There should be mixing instructions on the bag of concrete, but it is 1 part cement, 2 parts sand and 3 parts gravel.

Check with a company online called sundberg appliance parts, the counterbalance isn't hard to install and will definately be cheaper than new one.