We at BS Power Supplies know that working with concrete mixers and producing concrete can be simple but also comes with several challenges. We have a variety of models of concrete mixers available to choose from, allowing you to purchase the machine best suited to your needs. Read further to explore the different challenges that arise when working with concrete mixers and concrete, as well as how to prevent these situations from occurring. We will also discuss the standards and regulations that apply to the South African concrete industry.
Concrete Mixers: Common Challenges and Solutions/ Precautions
It is essential to produce and prepare concrete that suits the recommended standards. If not, concrete can lead to several common issues, such as bleeding and segregation. Producing the concrete can be seen as the easier part, whereas working with concrete and putting it can be more challenging. The weather also plays a significant role in setting concrete and can affect the quality. Below are some of the most common challenges and their precautions when working with concrete:
Concrete Mixers: Bleeding
Bleeding in concrete happens when excess water in the concrete comes to the surface. This is due to the improper settlement of heavier components like aggregates and cement. Excessive bleeding can also occur due to poor weather conditions, such as rain or lack of sunlight. If the evaporation rate and temperature are unideal, then the water droplets in the concrete will keep surfacing. When curing concrete, bleeding is a general process. However, excessive bleeding can cause harm by decreasing the strength of the concrete.
Ways to reduce bleeding:
- Strictly maintaining the water-to-cement ratio.
- Adding sand of finer particles.
- Using supplementary cementitious materials to increase water absorption.
- Adding an air-entraining admixture increases the freeze-thaw durability of concrete, increases its resistance to scaling caused by deicing chemicals, and improves the concrete’s workability.
Concrete Mixers: Segregation
To put it simply, segregation is the separation of the cement paste and the aggregates found in the concrete. In this concrete problem, the cement paste comes to the top while the aggregates settle down at the bottom of the concrete. Segregation affects the durability and strength of concrete as good concrete is always an even and homogenous mixture.
Ways to prevent segregation:
- Using the recommended proportion of cement and water.
- Avoiding over-vibration or compaction of concrete.
- Being cautious while handling, placing, or transporting concrete.
- Adhering to the advised concrete mixing guidelines, like mixing at a speed.
- Avoiding dropping concrete from long heights.
Concrete Mixers: Scaling
Scaling, or surface scaling, is one of the most common concrete problems. In scaling, the surface layer of concrete starts to deteriorate by getting by breaking off or peeling away. This is a common problem in areas with cold climates, roads and bridges, parking lots, driveways and sidewalks, industrial floors, pool decks, exterior building surfaces, and concrete slabs with poor finishing.
Ways to prevent scaling in concrete:
- Using air-trained concrete
- Not performing finishing steps till the water is present on the surface.
- Not using deicing salts like calcium, magnesium, or sodium chloride.
- Properly curing the concrete with the use of liquid membrane curing compound or by covering the surface of a freshly placed slab with wet burlap and polyethene sheets or a non-woven geotextile.
- Protecting the concrete surface during harsh weather conditions.
Concrete Mixers: Plastic Shrinkage Cracking
Plastic shrinkage cracking occurs in the concrete when there is excessive and rapid water loss from the concrete before it has been set. This happens when the surface moisture evaporation rate is higher than the rate of water bleeding in concrete. This problem is very common during hot weather conditions.
Here are the ways to avoid plastic shrinkage cracks in concrete:
- Avoid overmixing of the concrete.
- Provide sunshades around the concrete in hot weather.
- Placing or constructing temporary walls to block or reduce wind velocity.
- Placing concrete either early in the morning or in the late afternoon to avoid hot temperatures.
Concrete Mixers: Laitance
The consequence of the problems of segregation and bleeding leads to laitance in the concrete. During this concrete problem, a thin and weak layer of cement dust, sand, and lime appears on the surface. This condition further weakens the strength and durability of cement. Laitance often occurs due to segregation of the concrete components, over-vibration when placing the concrete, improper finishing techniques, inadequate consolidation when removing air, and rain/ water exposure during the early stage of curing the concrete.
Prevent Laitance With These Steps:
- Using water-reducing admixtures in concrete.
- Not doing the finishing steps till the water has evaporated from the surface.
- Removing clay, silt, and dust content before mixing concrete.
- Using well-graded aggregates in the concrete mixture.
- Use proper finishing techniques and avoid overworking the surface of the concrete.
Concrete Mixers: Dusting
Dusting refers to the formation of a loose, powdery layer on the surface of the concrete. This can lead to reduced durability of the concrete and aesthetic issues. Dusting is often found on traffic-exposed concrete surfaces.
How to Stop Concrete Dusting:
- Maintaining perfect water-cement ratio.
- Using dust-free aggregates and high-quality aggregates that are free from contaminants.
- Giving the concrete proper time to cure or dry or using wet curing methods or curing blankets.
- Using sealers to make concrete dusting proof.
- If calcium chloride is used, follow recommended dosage rates and take the necessary precautions.
Concrete Mixers: Challenges Regarding the Environment
Over the last 40 years, cement and concrete manufacturers have been working to reduce their environmental impact, particularly their CO2 emissions. Several actions have been taken to achieve this, such as improving the energy efficiency of kilns and processes, using alternative fuels to partially replace the fossil fuels needed to power cement kilns, using alternative raw materials in the concrete mixture, and manufacturing multi-constituent cement to lower the clinker content and help reduce the environmental impact of concrete.
With the main focus on producing low-CO2 cement and concrete, challenges with this new “green cement” have risen. Below are some of the challenges faced with using low- CO2 cement in production:
- Using alternative fuels often means a high degree of heterogeneity and new flame profiles for the kiln to produce the clinker. With many variations to manage, strict composition control to avoid harmful elements needs to take place.
- Decreasing the clinker ratio implies accurately controlling the kiln feed (chemical composition /particle sizes) to make it as active as possible. This requires extra effort and a watchful eye.
- Controlling the process (temperature and atmosphere) to get the right product of cement or concrete, regarding the oxidation, colour, etc.
- Using suitable calcined clay, which can be challenging to source locally.
Concrete Mixers: Modern Challenges in the Industry
Every industry faces challenges within our constantly changing environment. Several main concerns have affected almost every organisation in the concrete industry. Read further to learn about these challenges.
Concrete Mixers: Cost of Energy
The cost of energy has become a primary concern within the industry, mainly because power and fuel account for 25% of the costs of a cement operation. With most of the world’s cement production still relying on coal as an energy source, the industry remains sensitive to changes in the commodity market.
Concrete Mixers: Increased Overcapacity
Following the decades of plant expansion and greenfield projects in the 1990s and 2000s, the concrete and cement industry has struggled with the aftereffects.
Concrete Mixers: Environmental Regulations
Environmental regulations have become a popular topic in modern times. Almost every industry has been forced to innovate greener and more sustainable operating methods. Several initiatives have been criticised for not converting to more sustainable and eco-friendly practices and products, with concrete being one of them. Global efforts to mitigate the effects of climate change are only likely to intensify in the coming years, which is why the cement and concrete industry needs to move towards more environmentally- friendly and sustainable practices and materials.
The three challenges mentioned above are the main difficulties faced by the industry. However, a few others are of smaller yet great importance. These include:
- Lack of capital
- Economic uncertainty
- New disruptive technologies
- Political instability
- Threat of alternative building materials
- Logistics and transport
Concrete Mixers: Standards and Regulations
Every industry sector has regulations and standards that must be adhered to, and the concrete industry is no different. Standards and regulations are designed for safety, quality, and environmental purposes. These standards and regulations may change over time. Hence, it is essential to check with an experienced organisation in the industry or the local authorities for an up-to-date version. Read further to learn about the standards and regulations in South Africa that apply to the concrete industry:
National Building Regulations and Building Standards Act (NBR):
Published in 1977, these guidelines have been updated over time to remain relevant. The NBR applies to anybody in South Africa that is building any type of structure, mentioning the do’s and don’ts of building with concrete and concrete mixers. This information is accessible to the public via the Internet and includes several chapters related to building regulations. Below are some of the chapters mentioned:
- General principles and requirements
- Structural design
- Site operations
- Energy usage
The NBR includes many more parts and can be found online.
South African National Standards (SANS):
The SANS is a division of the South African Bureau of Standards (SABS) that publishes the South African National Standards. Some of the relevant SANS standards related to the concrete industry are:
- SANS 2001-CC1: Code of Practice for the Structural Use of Concrete (Part 1)
- SANS 1200: Civil Engineering Construction
- SANS 10100: The Structural Use of Concrete
More Standards and Regulations to Consider:
- Environmental Regulations from the National Environmental Management Act (NEMA) that require environmental impact assessments from building organisations.
- The South African Ready-Mix Association (SARMA) provides guidelines and standards for producing and using ready-mixed concrete.
- Note: Regulations and standards can change, and new ones may be introduced. It’s essential to consult with relevant authorities, government associations, industry associations, and legal experts to ensure compliance.
Concrete Mixers: About BS Power
B&S Commercial Power (pty) Ltd imports and manufactures a range of robust and high-performance equipment for professional use in construction, agriculture, forestry, and much more. We offer Baumax, Stihl, Husqvarna, Briggs and Stratton, and Honda concrete mixers and products.
Although we are based in Cape Town, we have a range of clients from all over Southern Africa, including Mozambique, Namibia, Zimbabwe, Namibia, etc. We stay updated with modern trends and information by regularly attending training workshops from our leading manufacturers.
With over 100 years of combined experience, we know what it takes to support professional concrete mixers and other commercial equipment users.
Please contact us via email or phone for more information regarding concrete mixers and our other equipment. We would love to help you find concrete mixers suited to your needs.