South Africa’s construction industry has suffered dearly due to load shedding. Complaints of project delays and disrupted work schedules are prevalent, and voltage spikes and power surges have been reported to cause damage to electrical machinery.
While having a generator on site may help ease some of the stress of load shedding, most generators do not have the capacity to fully power all the electrical machinery needed to finish a construction job. Luckily, there are certain cement mixers that do not need any electrical input to work.
How Cement Mixers Work
All cement mixers are powered by one of three things: petrol or diesel, gas, or electricity. While electrical cement mixers are usually considered the most affordable option, considering that electricity is still more affordable than fuel or gas, fuel-powered cement mixers offer the most fuss-free non-electrical alternative.
Cement mixers can be broken down into two different groups: batch mixers, and continuous mixers.
Continuous mixing is known as an energy-conserving method compared to batch mixing and entails materials constantly flowing into the mixer. This can be various slurries or mixes of aggregate, and this method is known to produce aggregate that has reduced structural integrity. This is a cement mixer option that works quickly but does not mix as well as batch mixing does.
Batch mixing, on the other hand, takes in materials and mixes them for quite some time. When the aggregate exits the cement mixers, the machine is either ready to be cleaned or ready to receive the next batch. Batch mixing results in a more thoroughly mixed aggregate mix, and this mix has more structural integrity than that produced by a continuous mixer.
How To Operate Cement Mixers
Operating cement mixers is not overly complicated, but each step must be followed to ensure the aggregate is sufficiently and smoothly mixed, and injuries are prevented.
Gather all the materials you need before starting the cement mixers process. This includes a dedicated mixer, water, buckets and the materials you will use to make the aggregate you need.
It is important to remember that you will require personal protective equipment (PPEs), including but not limited to protective eye goggles, gloves, safety boots, a face mask with filters and thick clothing. These should be worn each time you work with cement mixers.
Always ensure your concrete or cement mix is properly measured out, along with how much water you need. These instructions can be found on the packaging of the cement mix you’ve chosen for your project.
After adding the required amount of water to your cement mixers drum, turn the machine on. Wait until the cement mixers reach the desired speed before slowly adding the cement powder. Doing this slowly and in increments will ensure your aggregate mixes smoothly and thoroughly.
Once the concrete powder has started mixing with the water inside the cement mixers’ drum, the actual mixing can begin. Depending on the model of the cement mixers you will be using, this can typically take between three and five minutes.
If there are lumps forming in the mixing drum, slowly add water in increments. This will slowly mix the lumps into the rest of the aggregate, but it is common for lumps to form regardless of how carefully you add cement powder and water to the drum.
If you notice the cement mixture is becoming too watery, slowly add cement powder back into the drum until the consistency improves.
Once the cement mix has reached the desired consistency, the cement mixers should be turned off. Thereafter, it may be necessary to use tools such as a shovel and buckets to transfer the cement mix from the machine’s drum to wherever it is being poured.
Some cement mixers can be tilted forward to help make the pouring process more efficient.
Fuel-Powered Cement Mixers: The Advantages And Disadvantages
Petrol or diesel cement mixers are known as the reliable option when working on sites with limited electricity, or sites that are simply too remote to have an adequate electrical supply. This can help streamline the entire construction process and means there is a smaller chance of load shedding causing delays or rescheduling to a project.
While the cost of petrol or diesel is higher than the cost of electricity, cement mixers powered by fuel are known to have a lower energy consumption than electricity-powered cement mixers. This means that while the refuelling of petrol or diesel cement mixers is more costly, the long-term spending may be lower than that of an electrical cement mixer.
As these cement mixers make use of a drum mixer, this means that the aggregate being mixed is more likely to be mixed consistently, resulting in a more structurally-sound finished project.
It is important to note that exhaust fumes from fuel-powered cement mixers can pose a danger to those on site. Diesel exhaust emissions are categorised as carcinogenic, according to the World Health Organization (WHO). This is because diesel exhaust fumes contain up to 10 times the amount of soot particles found in petrol exhaust fumes, so care needs to be taken to ensure those working near or with diesel cement mixers wear PPEs and are working in well-ventilated areas.
While diesel cement mixers are not well-suited to the needs of someone who is embarking on a DIY project, they are exceptionally suited to the output needed for commercial or industrial projects.
Overall, the cost of purchasing or renting petrol or diesel-fueled cement mixers is lower than that of electrical cement mixers. Fuel-powered cement mixers also have the advantage of generally being lighter and easier to transport than electrical cement mixers, and also having a larger drum capacity as they are used as industrial mixers.
How To Maintain Diesel Cement Mixers
While the maintenance of diesel cement mixers is not particularly demanding, it is important to ensure maintenance is ongoing. This will ensure that the mixer works efficiently and protects anyone using it from injury due to negligence.
Step 1: Keep the motor clean
Diesel-powered cement mixers require frequent cleaning. The motor can be wiped down with a damp, clean cloth and an air compressor can be used to clean away any hard-to-reach areas.
It is common for cement and other particulate matter to make its way into cement mixers’ engines, and this is dangerous as it can cause clogs that, in turn, can cause the motor to blow.
Step 2: Keep the drum clean
While it may seem demanding to clean your diesel-powered cement mixer after each use, this will ensure it is able to work more efficiently for longer. Drum maintenance is straightforward and simply requires water to be poured into the drum, and then for the cement mixer to be turned on.
Any stubborn concrete or cement can be cleaned out using a pressure sprayer.
Hardened concrete may pose a bit of a challenge, but this is easily solved through several steps, including:
- If there is stubborn concrete or cement stuck inside the drum of diesel-powered cement mixers, fill the drum with water and gently tap it as the drum rotates. This will knock any hard lumps of aggregate loose without causing any denting or damage to the drum.
- If there are still stubborn aggregate lumps clinging to the inside of the cement mixer’s drum, an acidic cleaning product can be used for deeper cleaning.
Step 3: Check nuts and bolts before every use
Always ensure that all nuts and bolts are tight and secure before using a diesel cement mixer. This is a very important step, as it is the biggest contributor to ensuring the cement mixer is safe to use.
Step 4: Grease what needs to be greased
There are many parts of a cement mixer that can wear down due to friction, including the mixing drum’s pulley. Ensuring that everything that needs to be lubricated is adequately maintained will not only reduce the chances of personal injury, but also ensure the cement mixer is well-maintained and thus, will work for longer.
General Safety Rules To Remember When Working With Diesel Cement Mixers
Cement mixers are one of the most vital and common tools to be found at any construction site. While this means many people are familiar with their operation, it may also mean that those who work with cement mixers daily may become lax about safety. Typically, the more familiar we become with a piece of equipment, the less likely we are to regard general rules of safety when using said equipment.
Here are some general rules to help protect those working with cement mixers:
- Always ensure that those who are working with cement mixers are familiar with the safety and instruction manual.
- Never load the drum while the cement mixer is stationary.
- Ensure the cement mixer is well-maintained, all nuts and bolts are tight, and that the cement mixer is clean before the day’s work begins.
- Check that there are no tools or equipment inside the cement mixer before turning it on.
- The machine should not be left unattended while turned on.
- All guards and covers should be removed before the cement mixer is turned on.
- Ensure no one has their hands near the cement mixer’s drum while it is rotating.
- Always ensure those working with a cement mixer are wearing the appropriate PPEs.
A Brief History Of Cement Mixers
Stephen Stepanian developed and patented the first electric truck mixer in 1916 to replace the horse-drawn concrete mixers in use at the time. A wooden shovel stirred the mixture while the wagon wheels turned, but the design was of limited use. However, the same applies to engines and trucks from this period.
By the 1940s, however, engines and truck frames had caught up with the need for heavy-duty vehicles capable of carrying thousands of pounds of wet or uncured concrete. When the post-World War II construction boom was in full swing, truck mixers came into their own. The big drum mixers you see on the streets today haven’t changed much from Stepanian’s vision of a better concrete truck. Mobile transit mixers are available in a combination of motors, truck frames and rotary mixers.
The mixer is like, but larger than, the smaller ones found on construction sites. A large motor, separate from the engine, rotates the drum of the truck body, and a series of paddles or screws driven by the same motor keep the aggregate, water and cement in constant motion. In this way, the ready-mixed concrete does not harden even as the clock ticks to deliver loads to a construction site, section of road, or parking lot. Most cement manufacturers recommend limiting the mix-to-injection time to no more than 90 minutes. Even better, you can have it on your site within an hour.
Technology has also changed the basic mixer design. Many truck mixers still have rotating drums, but most do not simply pick up and carry large amounts of wet cement. Yet most are street locations where the mixture can be watered immediately.
Most transport mixers have a separate water tank on the truck. A rotating drum keeps dry materials, aggregates and cement mixed for most of the process. Drivers add water and deliver fresh concrete just a few kilometres from the site.