Australia is often thought of as being a hot country, but in truth this isn't quite accurate. Australia is an extremely large landmass—comparable in size to the entirety of the United States—and its temperatures vary a great deal as a result. If you're in Victoria, Tasmania or New South Wales, you're very likely indeed to spend some time in temperatures well below freezing and beset by snowfall.
This can be bad news for concrete contractors, who find that their 'mud' (as those in the trade call it) freezes in the boom, the hopper and the pipes as it's being pumped. So what can be done to limit this issue?
Use very hot water to mix and prime the concrete and the slurry: If it's very cold in the morning but likely to warm up a little as the day wears on, you can simply use water that's as hot as you can arrange for to mix the concrete and its slurry. This is a great short-term fix on such days.
Insulate your boom: Simply by wrapping your pipeline with thick insulating foam, you'll be able to keep your concrete warmer for longer. This is a great thing to do alongside tip #1, as it helps the effects of that tip last a great deal longer into the day.
Don't be afraid to let your machine thaw: If your concrete does freeze, your pumping machine will cease operations till it's thawed out. When that's done, you'll need to clean it thoroughly before starting up again. Some people get nervous about this, thinking the delay will ruin their batch of concrete—but the thing to bear in mind is that frozen concrete cannot set. This is a problem when it's laid and you need it to dry, but a boon when you're trying to work with it on a cold day.
Experiment with additives: There are a few things that can help you out simply by being added to your mix. The most common is calcium chloride. Be careful, though: using an additive like this can cause some of the same issues you might find while working on a very hot day, like flash setting or concrete drying into the works of the machine. Keep an eye out for potential issues and nip them in the bud before they can settle in.
Whichever method you choose, your primary concern is safety. Make sure neither you nor your machinery are set up on icy surfaces, and ensure that you and the rest of your team are not working in a dangerously chilly situation.