CONCRETE THAT WORKS FINE – WITHOUT ANY SAND

No-fines concrete (NFC) is obtained by eliminating the fine material – sand – from the normal concrete mix. Instead, single-sized coarse aggregates are surrounded and held together by a thin layer of cement paste to add strength.

Among the main advantages of NFC is economy in materials, higher thermal insulating values, lower shrinkage, and lower unit weight and density.  It is mainly used for load-bearing, cast-in-place external walls of single storey and multi-storey housing, small retaining walls or damp-proofing sub-base material for concrete floors cast on grade.

 Here Bryan Perrie, managing director of The Concrete Institute (TCI) sheds some light on this type of concrete:

NFC consists of coarse aggregate and cement paste. In the hardened state, the aggregate particles are covered by a thin layer of cement paste and are in point-to-point contact with each other. At each contact point, the paste forms a small fillet and these fillets hold the particles together and give strength to the concrete.

NFC therefore has large interconnected voids and a lower density than conventional dense concrete. The structure of NFC makes it ideal for use as a drainage layer under reservoir and basement floors and it can also serve as an insulating layer and as a damp-proofing material. Note, however, that NFC is definitely not suitable for drainage purposes where the water is soft or aggressive to concrete.

Materials:

* Cement – Common cement that complies with SANS 50197 should be used for NFC. Masonry cements are not suitable.

* Water – Water that is suitable for making conventional concrete should be used.

* Aggregates – Clean, single-sized concrete stone should be used, and flaky aggregates should be avoided. The most commonly used aggregate is 19mm crushed stone. Smaller stones may be used and mixes made with smaller stone are in fact easier to handle and place, but consume substantially more cement.

For most applications, mix proportions range from 200 to 300 litres of aggregate per bag (50 kg) of cement. The water content of the mix is critical: if the paste is too dry it will not coat the aggregate properly; if it is too wet, it will run off the aggregate particles and possibly block the voids at the bottom of the pour. Experience has shown that the water content should be between 18 and 22 litres of water per bag of cement.

A cubic metre of compacted NFC requires about 1.05m3 of stone, measured in the loose state. Cement content is between 260 and 180kg, depending on mix ratio.

NFC should be machine-mixed as hand mixing is difficult and laborious. If hand mixing is unavoidable, it is best to mix the cement-water paste in a container prior to mixing the paste with the stone. When mixing the paste, mix the cement into the water rather than the other way around.

NFC must be placed and compacted as soon as possible after mixing as it tends to dry out rapidly because of its open structure. Compaction is achieved by rodding the concrete – vibration must not be used and heavy tamping is not necessary.

Because of its open structure, NFC must be protected from drying out and must be thoroughly wet cured for at least seven days unless it is plastered, screeded or covered before that time.

NFC has a rough surface texture for plastering. Normal plaster mixes are used and the surface of the NFC must be dry when applying the plaster. Plastered NFC walls have some excellent qualities, but one drawback is that neither conventional wall plugs nor masonry nails can be used for attaching fixtures to the walls.

When used in underfloor drainage, roof insulation and domestic floors, NFC should be screeded within 72 hours of placing with particular attention paid to wet-curing the screed. Normal screed mixes of 100 to 130 litres of concrete sand per bag of cement should be used with enough water to produce a mix of plastic consistence.

NFC has negligible flexural or tensile strength. Compressive strength is usually between 5 and 10 MPa at 28 days for mixes in the range mentioned previously. Higher strengths may be obtained by including 50kg of fine sand per bag of cement. This increases the size of the fillets, and hence the strength, but reduces the voids and increases the density correspondingly.

For further information, contact info@theconcreteinstitute.org.za or visit www.theconcreteinstitute.org.za or phone 011 315 0300.

TCI INFO CENTRE VITAL CONCRETE REFERENCE SOURCE

The Information Centre, a key section of The Concrete Institute (TCI) in Midrand, is continuing to add to its unique collection of reference material relating to cement and concrete – the largest collection of its kind in Africa.

Established in 1957, the TCI Information Centre operates as a public concrete technology library and is accessible to anyone in South Africa interested in or needing information on concrete topics. It has over the years become an essential destination – both personally or online – for thousands of students as well as practitioners in the concrete and related industries.

The Centre has a vast collection of well over 140 000 concrete-related reference material, including e-documents, books, and journals from across the globe.

Susan Battison, manager of the TCI Information Centre, says the collection includes the latest published American Society for Testing and Materials (ASTM) standards relating to cement and concrete, adding to the Information Centre’s collection of South African and British standards.

“The collection of conference proceedings, which are indexed fully on our online catalogue, has also grown and now includes papers on super-absorbent polymers and the rheology of construction materials. Information on construction techniques in precast and 3D printing have also been acquired while South African research by Prof Mitchell Gohnert, of Wits University, on shell structures has also been added.

“The assessment, repair and rehabilitation of concrete structures are also key additions to the collection and augments our material on the sustainability and durability aspects of concrete infrastructure. The publications of international organisations such as the International Union of Testing and Research Laboratories for Materials and Structures (RILEM) and the International Federation for Structural Concrete (fib) are also stocked,” Battison states.

The TCI Information Centre indexes all the journals it receives and provides a monthly list of current contents which can be accessed by emailing info@theconcreteinstitute.org.za with the subject line “Subscribe current contents”.

“Despite revolutionary changes in information technology over the past 63 years, the Information Centre collection has kept pace with the latest trends in information dissemination and remains a valuable resource on cement and concrete information that contributes to the development of sustainable and durable South African infrastructure,” she adds.

The TCI online catalogue is available at http://www.cciinformationcentre.org/ActiveConnect2002/default.html.

New Self-Leveller From Mapei

Mapei South Africa is excited to announce the launch of its new locally manufactured self-levelling compound – ULTRAPLAN ECO 20. As a direct result of requests from the market, the decision was taken to add this innovative new product into our basket as an add on to the existing ULTRAPLAN range which has been available for some time.

“ULTRAPLAN ECO has proven to be a fantastic product and will continue to be ideal for use in the environments that are subjected to heavy traffic due to its 26-30Mpa compressive strength. MAPEI subsequently encountered requests for a solution for residential and light traffic areas which lead to the development of ULTRAPLAN ECO 20 which has all the benefits and features of ULTRAPLAN ECO, but with a lower compressive strength.” explains Chad Tosen – Technical Sales Consultant for Soft Coverings and Industrial Flooring.

This high-quality, self-levelling solution is a rapid-setting compound which can be used to correct substrates with thicknesses of between 1 to 10mm. Furthermore, it has very low emissions of volatile organic compounds making it safe to use internally without any additional safety equipment and minimal impact on the environment. Once mixed with water, ULTRAPLAN ECO 20 becomes an easily workable self-levelling compound which can be applied via either a trowel or pin rake. For larger applications in excess of 100m2, an automatic pressure pump can also be used.

ULTRAPLAN ECO 20 will be easily identifiable on site as the finished product is pale pink in appearance.  This will be a benefit to all end users as it ensures the correct product is used for the correct application.

MAPEI South Africa has extended the ULTRAPLAN range to include ULTRAPLAN MAXI which will be available to the local market in the near future. ULTRAPLAN MAXI accommodates thicknesses from 1 and 40mm in a single application whilst still encompassing all the standard features of the ULTRAPLAN range.

About Mapei South Africa

Mapei South Africa is part of the Mapei Group, an Italian-based multinational that is a leading manufacturer of chemical and adhesive products for the construction industry. As part of the multinational group, Mapei South Africa passes numerous benefits onto its client base by having access to knowledgeable technical experts, research capabilities and product specialists. Mapei South Africa distributes its products throughout sub-Saharan Africa.

 

 

A Guide To Industrial Flooring

The correct flooring choice for industrial sites is mission critical, delivering a secure, sterile, and well-organised operative workfloor. But, selecting the appropriate industrial flooring presents challenges as floor failure may be inevitable within 14 months, with attendant client headaches and capital outlay, as well as legal issues.

Ameliorating potential disaster depends on following the correct procedure in choosing the most appropriate flooring that satisfies the mandates of the context-specific work environment with regard to the rules of the particular industries’ well-being, security, sanitation and accordance.

Some pointers to avoid during the ordering procedure comprise selecting a finish based solely on looks, choosing the least expensive option, going with the identical previous choice, and ignoring the state of the substrate or the practical use of the site. These criteria will result in a floor that snaps, powderises and disintegrates when used for the daily operations it is intended.

Look at flooring properties (anti-bacterial agents, anti-slip aggregates and the dissipation of electricity) when considering industrial floor destruction triggers such as chemical abuse from a water, dust, fuels, sanitizers, acids, lubricants, and in certain industries, by-products from foodstuffs including sugars, hot oils, blood and grease. Finish as well as substrate and soil degradation may result, and the corrosiveness of contaminates depending on their temperatures must be factored in.

Another consideration is risk auditing the degree to which the floor is exposed to corrosion, divided into immersion, intermittent spillage or infrequent contact.  And, traffic loading, equipment being moved, dropped tools, dragged pallets and forklift traffic places extra strain on the floor. Here, determining the compressive floor strength defines the suitable flooring needed per task.

Industrial facilities are subject to stringent cleaning with hot water / steam to get rid of grease and fuel – these factories usually experience room temperatures, so heated cleaning produces thermal shock with flooring exposed to unusually hot temperatures

Flooring comprising epoxy, vinyl or MMA is unsuited to thermal shock, leading to cracking, delamination and material damage / failure during temperature fluctuations, including thermal cycling (temperature raised or lowered seasonally or during cleaning).

Successful flooring finishes hinge on correct substrates underpinning them, and inferior substrate / concrete results in delamination (smooth concrete, failure to remove the laitance, ineffective bonding of resin to substrate).

Concrete absorbs ground moisture and new concrete has a significant moisture content until dried, so its pH level and moisture content adversely affects flooring (causing blistering and debonding), necessitating the analysis of the moisture level during specification, and the use of a damp-proof membrane (DPM) if necessary, which smooths the moisture vapour transition).

 

 

Floor Screeds

Following a 1:3 or 1:4.5 ratio of cement to sharp sand, floor screeds comprise cementitious matter, spread over precast concrete flooring or in-situ concrete ground flooring.  Options for application include direct base bonding, unbonded laying over a moisture-proof membrane that is positioned over the slab. Another method is to apply it on a layer of firm insulation material for application with cast-in water pipes to deliver underfloor heating.

For fortification, use a fine metal of glass mesh; the screed may be kept as is or floated to enable smooth surfacing to lay the finish over.

If reinforcement is required, this can either be in the form of a fine metal mesh, fibres which are normally polypropylene or a fine glass mesh. Ready, factory-mixed sand / cement screeds trump site-mixed ones in terms of consistency. Pumpable flowing screeds deliver more level surfaces. These are calcium sulphur binder-based, applied (with varying minimum thickness) more quickly than sand / cement screeds, and can be used in combination with underfloor heating

Cement Sand Screeds

The most likely cause of bonded screed failure to the below substrate is if the screed is too thick, and an unbonded screed fails by lifting or curling, which happens if the screed is too thin. The ideal bonded screed thickness is >50 mm and unbonded < 70 mm to 100 mm to avoid curling.

Criteria for screed design (depth and type) include specified floor finishes, the construction tolerances and the provision of falls. Included is structural dictates like mitigating disproportionate collapse and the actioning of composite movement with the slab below.

Screed use can be avoided by stipulating more stringent construction tolerances that ensure direct flooring material flooring reception. If screeding is required, use cement sand screed or the more contemporary proprietary self-smoothing type.

The following definitions apply to specific screed types:

Levelling screed – screed finished to specified level to receive final flooring.

Wearing screed – screed that functions as flooring.

Bonded – screed laid onto a mechanically prepared substrate.

Unbonded – screed deliberately kept apart from substrate by membrane.

Floating  – type of unbonded screed laid on acoustic / thermal insulation.

Cement sand screed – contains sand up to 4 mm maximum aggregate size.

Fine concrete screed – contains concrete with maximum aggregate of 10 mm.

Pumpable self-smoothing screed – mixed to a liquid that can be moved by pump to site and will flow adequately to deliver the desired level accuracy and surface regularity (also known as self-levelling screeds).

Curling – upward deformation of screed edges.

Leveling equipment

The level and flatness of any concrete floor is of major concern for structural engineers, flooring inspectors, superintendents, finishing foremen and construction contractors.

Extreme concrete floor flatness (FF) and floor levelness (FL) are mandatory for sites containing carefully calibrated equipment, as well as for warehouses, offices and distribution centres. Even, level surfaces are conducive to secure lift truck activity, as well as guaranteeing that high-level vertical storage shelves are able to support electronic picking setups.

Electronic floor profilers were patented in the ‘70s in order to streamline floor flatness and levelling, and were manually operated wheeled machines that created new floor measurement codes, known as F-numbers, which became standardised indicators of FF and FL for industry.

Other pour concrete floor finishing enhancers, eg the laser screed and ride-on power trowel, were also developed, as well as laser scanning. The latter assists in “reality capture” and has immense use in digitally capturing the surface topography of a freshly minted concrete pour in 3D form.

Aberrations in floor flatness and level can be analysed with computer software for the benefit of inspectors and concrete contractors. The exactness, rapidity, ease and flexibility of laser scanning is replacing traditional floor profiling devices as the new standard for FF/FL measurement

Practical floor application tools include spike shoes, spike rollers (For the removal of air bubbles from and cementitious floor coatings,  epoxy floor coatings and self-leveling screeds), rakes, adjustable levelers, squeegees and spatulas and mixing machines.

Concrete Offers Myriad Advantages

Concrete Offers Myriad Advantages

Due to its durability, versatility, aesthetic appeal, cost-effectiveness and availability, concrete is changing the face of South Africa’s landscape with cutting-edge architects and engineers increasingly making concrete their material of choice.

Concrete is the most economical choice for engineered structures, says TCI MD Bryan Perrie

Here, Bryan Perrie, MD of The Concrete Institute, (TCI) deals with the benefits of the world’s oldest and most popular building material:

Economic benefits:

Due to its longevity and ease of construction, concrete is often the most economical choice for engineered structures. Load-bearing concrete exterior precast or tilt-up walls serve not only to enclose the buildings, but to carry roof and wind loads – eliminating the need to erect separate cladding and structural systems.

Lower energy costs:

The energy efficiency of a structure is a major consideration in the life cycle cost analysis. Concrete construction can minimise the overall building height to shorten vertical runs of mechanical and electrical systems and reduce the exterior surface area to be enclosed and insulated.

Insulated concrete buildings with a medium to high level of thermal mass are characterised by their inherent ability to store thermal energy, and then release it several hours later when needed.

Faster turnaround:

Once the design has been selected, there is generally pressure to get a project started. More and more organisations are making speed a priority, particularly high technology companies and rapidly growing firms. When such businesses decide to construct a new facility, they are often overburdened and already behind schedule. With concrete designs, there is no delay in getting started as concrete is readily available from many locations across South Africa. A concrete structure can be well underway using in-situ concrete before final plans are complete. Precast/prestressed concrete can also help reduce construction time and on-site labour costs by taking advantage of pre-fabrication of standard and custom structure segments.

From multi-billion rand massive dams to simple low-cost housing schemes, concrete is the logical choice

Advanced construction techniques such as ‘flying formwork systems’, increase the speed of floor construction. As a concrete frame progresses upward, workers on the completed floors below can proceed with interior partitions, exterior finishing, electrical, mechanical and plumbing systems.

Generating revenue faster:

Faster construction means reduced carrying costs and faster revenue generation. This facilitates more timely pay back of financing charges and faster revenue generation for the developer/owner.

Versatility:

The design flexibility of concrete allows the contractor to accommodate design changes after the process has begun.

Design and colours:

Limited only by a designer’s imagination, the breadth of designs, colours and textured finishes available in concrete today is unrivalled. Mixing and matching colours and textures provides a spectrum of design possibilities.

Textures:

Concrete textures can resemble smooth, high-polished granite or gutsy, exposed aggregates with a rugged feel. Other possibilities include tumbled cobblestone, brick, cultured limestone, slate, flagstone or river rock.

Stamping and scoring:

As natural stone becomes inaccessible or the costs rise prohibitively, concrete is a natural alternative for recreating traditional finishes in a cost-effective way. Besides being widely available and less expensive than quarried stone, cement-based cultured stone is easier to match and install. This makes it popular even in places where quantities of quarried stone are available.

Reduced sound transmission:

Containing sound within the walls of a structure is critical in today’s highly competitive environment. Should the tenant requirements include sound transmission control, the natural mass of concrete floor and wall systems provides both acoustical resistance and vibration control.

Creative wiring options:

Thin concrete floor structures facilitate the use of raised floor systems used where the wiring is run in the space below.

More floors per structure:

Shallower floor systems are an important structural advantage of concrete. On average, the construction of concrete buildings will allow one additional floor to be created for each 10 storeys of traditional building height, resulting in more rentable space for buildings of similar size. When faced with height restrictions, concrete construction is a key consideration and could represent initial construction cost savings and additional income generation. Longer spans:

Post-tensioning reinforced concrete beams and slabs allow for longer floor spans with fewer columns to plan around. This offers flexibility in architectural layout and even more usable space. Increasingly, concrete is setting the standard for space planning and utility infrastructure.

Fire resistance:

The range of designs, colours and textured finishes available in concrete is limited only by a designer’s imagination

Concrete is often left exposed on interior walls due to its aesthetic appeal, durability and inherent fire-resistance.

Ideal for strict specifications:

A major advantage of concrete construction for engineered structures is the material’s properties of density and mass. Lateral stiffness, or resistance to horizontal movement, make concrete the product of choice when constructing tall buildings where high winds or seismic conditions are considerations. This lateral stiffness also means that occupants of concrete towers are less able to perceive building motion.

Energy efficiency:

Most concrete is produced locally, minimising fuel requirements for handling and transportation. Once in place, concrete offers significant energy savings over the lifetime of the structure. The mass of a concrete structure makes it a significant thermal reservoir with the ability to store large amounts of energy. In hot months, concrete walls and floors absorb the interior heat during the day, then radiate warmth back into the space at night. The same principle holds true for cooling. This thermal inertia allows concrete to help maintain a relatively steady interior temperature.

Recycling:

Concrete is an inert material that is easily recyclable. Old concrete that has reached the end of its service life can be reused as aggregate for new concrete mixtures. The addition of industrial by-products such as fly ash, silica fume and blast furnace slag make concrete less permeable while incorporating materials that would otherwise be deposited in landfill sites.

Turner Appointed As SARMA’s New Manager

SARMA Appoints New Manager

Hanlie Turner

Hanlie Turner has been appointed Manager at the Southern Africa Readymix Association (SARMA).

Following the departure of Johan van Wyk who was the face of SARMA for many years, Turner has taken over the reins at the SARMA office.

She brings years of experience in the cement and concrete industry, including a two-year term as President of the Concrete Society of Southern Africa.

South African Cement Producers Apply For Protection Against Imports

South African Cement Producers Apply For Protection Against Imports

The Concrete Institute (TCI) has on behalf of the South African cement producers applied to the International Trade Administration Commission (ITAC) of South Africa to investigate the surge of imports of low-priced cement.

TCI has lodged the application on behalf of AfriSam, Dangote Cement SA, Lafarge Industries South Africa, Natal Portland Cement Company, and PPC.

Bryan Perrie, TCI Managing Director, says imported cement is undercutting the industry by at least 45%. When this is combined with unprecedented low levels of demand due to slowed economic growth, the industry is facing a survival crisis which threatens to undermine the industrial capacity of the country. “The cement industry has no option but to request ITAC to conduct a safeguard investigation to determine whether the cement industry requires protection from the surge in imports,” he states.

Bryan Perrie, MD of The Concrete Institute

Perrie says South Africa has become a net importer of cement with total imports increasing by 139% since 2016 which makes trade remedy protection vital to ensure the viability of the cement industry. “Local producers have the capacity to meet the Southern African Customs Union’s industrial demand and must protect employment, Broad Based Black Economic Empowerment (B-BEEE) investments and Environmental Social and Governance (ESG) requirements. The SA cement industry needs to compete on a level playing field and not against a surge of low-priced imports,” Perrie asserts.

The South African cement industry is very competitive. The cement, concrete and affiliated industries employ thousands of South Africans whose jobs would be on the line if local cement production is not protected. Importantly, several producers have significant B-BBEE investments that are at stake.”

In addition to the surge in low-priced imports, a “carbon tax” was introduced in June 2019 on the South African cement industry’s activities that has increased the industry’s production cost. The effect of this tax translates into a 2% increase in selling prices, putting the local cement industry at a further disadvantage against imports. 

Local pricing reflects the standards (technical, social and environmental) that have been determined by South Africa as necessary for local manufacturing. SA cement manufacturing processes are regulated, from environmental impact assessments to strict quality controls, and from labour and employment regulations to sustainability requirements and South Africa is a signatory of the Paris Accord on CO2 emissions.

In support of the application, TCI has outlined that:  

  • A total of 350 441 tons of cement arrived in RSA during the second quarter of 2019 – the most since the third quarter of 2015; 

  • Most of the cement landed at Durban. The 260 909 tons that arrived there is an 85% increase on the first quarter of this year;

  • Imports from Vietnam totalled 301 872 tons;

  • Imports have exceeded exports by over 50 000 tons during the past year;

  • Total imports increased by 139% since 2016;

  • Employment in the industry increased by less than 0.5%; and

  • South Africa represents roughly 1% of total exports from Vietnam, for example, where exports have increased by 50% in the first half of 2018 to 15 million tons according to information provided by Global Cement. 

Perrie feels the South African economy is at a crossroad where trade policy determinations will play a critical role in determining the industrial direction of the country. “The key to future growth lies in achieving greater efficiencies within the country’s relevant manufacturing sectors. The cement industry must compete on a level playing field and not be scrambling to survive against low priced imports. The sector needs space to grow, which a successful ITAC application would provide,” he states.

Special Training For Concrete Work In Winter

Special Training For Concrete Work In Winter

Icy weather’s effects on concrete is covered in detail in The Concrete Institute’s SCT30 “Concrete Technology” training – an intensive five-day course that deals with, among many other subjects, the special techniques required for cold weather concreting.

John Roxburgh, senior lecturer at TCI’s School of Concrete Technology, says special techniques required for winter concreting include optimising the mix design, methods of heating up the concrete, thermal curing and the use of concrete maturity measurements.

Dealing with extreme temperature is fundamental to good concrete practice on site. Cold weather concreting is often defined as the placing of concrete at temperatures below 50C and in the South African there are many areas that will have ambient temperatures around or below 50C – especially early in the mornings, late afternoons and evenings.”

John Roxburgh, senior lecturer at the School of Concrete Technology

Roxburgh says in cold weather several potential problems may occur:

  • The binder will hydrate at a slower rate leading to concrete taking longer to set and gain strength which has the knock-on effect of longer bleed times and difficulties in finishing, as well as later stripping times;
  • There is also a chance of the concrete freezing with the associated damaged caused by the expansion of ice within the concrete.
  • Thermal cracking in mass pours may also be harder to prevent with high temperature differentials between the hotter core concrete and the outer concrete in contact with the low external ambient temperatures.

However, there are some basic and simple steps to take for concrete work in cold weather. The first is to always try and cast the concrete on a rising thermometer: rather cast in the early morning with the ambient temperature increasing as this would give the concrete more time to gain strength before it potentially freezes. Try and use slightly ‘richer’ mixes by either adding more cement to the mix or reducing the extender content in the cement. The use wooden formwork to help insulate the concrete or placing industrial insulating blankets and mats over the concrete will also help. The concreting works could also be done in a tent.

Concrete pour at sunset:
Casting concrete early in the morning in winter gives the concrete more time to gain strength before it potentially freezes, says John Roxburgh, senior lecturer at the School of Concrete Technology.

All these measures are reasonably easy to implement and will help tremendously in protecting concrete but there are more sophisticated and integral techniques that can be used in cold weather concreting to prevent costly setbacks – and these are covered in the SCT30 course offered by the School of Concrete Technology,” Roxburgh adds.

The TCI School is the oldest and largest provider of concrete technology education in South Africa and has a wide range of courses that cater for all levels of competency.

For more details about the SCT30 course as well as all the other 2019 courses planned in Midrand, Cape Town and Durban by the School of Concrete Technology this year, phone 011 315 0300 or email sct@theconcreteinstitute.org.za or visit www.theconcreteinstitute.org.za.

Innovation In Cement Production Crucial To Environmental Sustainability

Innovation In Cement Production Crucial To Environmental Sustainability

In this exclusive article SA Builder delves into sustainability in cement production:

AfriSam’s value of ‘Planet’ is defined as a responsibility for the impact of its actions on the community and the environment

AfriSam’s Dudfield cement plant near Lichtenburg in the North-West province has its roots dating back to 1949 and remains a vital pillar in South Africa’s construction sector.

Vishal Aniruth, general manager at AfriSam Dudfield, notes that the plant had seen a number of production upgrades over its life-time. As importantly, it had been at the leading edge of efforts to achieve environmental sustainability.

We were one of the first plants in the country to convert from old electrostatic precipitator technology in terms of air emissions control,” Aniruth said. “This involved the installation of bag-house filter technology for kiln emissions, and allowed us to achieve compliance with the latest emissions standards.”

The Dudfield facility began as a mining operation, exploiting the shallow calcrete deposit that covers the entire 3 608 hectare mining licence. Before the plant was built, the mined limestone was shipped to the company’s kilns in Roodepoort.

Today, the quarry is a split-bench operation that opens up about 15 hectares a year. It produces annually about two million tonnes of limestone and 120 000 tons of shale for the plant from the Spring Valley quarry, located 65 km away.

Aniruth highlighted that the latest computer-based modelling techniques are used for deposit optimisation. This ensures that the mine plan generates the required quality of material for the plant. He noted that there are 65 years of proven reserves at the quarry, with further reserves at AfriSam properties at Kalkfontein and on the neighbouring farm Bethlehem.

AfriSam’s Dudfield cement operation in the North West Province was commissioned in 1965

Long experience

The cement plant itself was commissioned in 1965, with one kiln with the capacity to produce 380 000 tonnes per year. Kiln 2 followed in 1972, with an annual production capacity upgraded over time to 780 000 tons. The plant grew further in 1977, when Kiln 3 was added, augmenting capacity by another 630 000 tonnes a year. In an important market-leading innovation in 1992, Dudfield installed the country’s first cement roller press to enhance the manufacturing process and improve grinding capacity.

Continuously aligning its production capacity with market demand, AfriSam Dudfield upgraded its Kiln 3 capacity in 2003 to over a million tonnes a year. The plant currently operates only the Kiln 3 production line – a four-stage configuration with in-line pre-calciner. The kiln features indirect firing with a multi-channel burner.

Fully integrated plants

Among the key elements of current plant operations at Dudfield are two coal mills and two cement mills. Coal mill 1, constructed in 1966 with production capacity of 11 tonnes an hour, feeds the pre-calciner burner. The other unit mills coal for the main burner, and was built in 1975 with a 16 ton per hour capacity. Cement mill 1, installed in 1966, has a 49 ton per hour capacity. The second cement mill is larger, giving it double the capacity at 98 tonnes an hour.

The cement output from Dudfield is delivered as road bulk, rail bulk and bagged cement. The plant’s in-house road bulk and weighbridge facility is used to load tankers. On the rail bulk operation, a large portion of the plant’s production is railed to AfriSam depots. Clinker is also supplied to AfriSam’s Roodepoort milling facility. The packing and palletising facility produces a bagged cement product for the market.

Dudfield is one of two fully integrated AfriSam cement plants in South Africa, which together can produce 4,5 million tons of cement. The second is the Ulco plant in the Northern Cape. The company’s third plant – with annual capacity of 1,2 million tons – is in Tanzania.

The cement output from Dudfield is delivered as road bulk, rail bulk and bagged cement

Environmental mission

Also addressing the media visit to Dudfield was Hannes Meyer, cementitious executive at AfriSam, who focused on the company’s commitment to environmental issues. He noted that the global cement industry was responsible for about 5% of the world’s greenhouse gases released into the atmosphere. The country was also a significant producer of CO2 emissions.

South Africa is one of the world’s largest and fastest-growing carbon emitters,” said Meyer. “We are in the global top ten of CO2 emitters, when measured per capita.”

As a result, the country had committed to reduce greenhouse gas emissions by 34% below its ‘business as usual’ levels by 2020. As cement manufacturing produces a high level of CO2, he said, AfriSam had been proactive since the 1990s in charting and implementing a path towards environmental sustainability.

Cutting emissions

The innovative step in 2006 to install a baghouse in Dudfield’s Kiln 2 line was part of a broader corporate strategy, built on the values of ‘people, planet and performance’. AfriSam’s value of ‘planet’ is defined as a responsibility for the impact of its actions on the community and the environment.

We were the first company to equip all our kilns with the latest bag filter technology,” he said. “As a company, we are committed to make a difference and to leave a legacy that is positive.”

These initiatives have reduced the company’s particulate emissions to less than a tenth of what they were in 2003. It has also brought emissions to below even the European standard of 30 mg/m3; local regulations require 50 mg/m3 or less.

In the year 2000 AfriSam introduced Project Green Cement to actively reduce its carbon footprint

CO2 programme

Overall, the progress achieved in controlling its plant emissions and making production facilities more energy efficient has had considerable impact on AfriSam’s environmental performance. Between 1990 and the present, its CO2 emissions per ton of cementitious material have been reduced by 35%.

The use of extenders in cement has been an important aspect of these efforts. In 2000, the company launched Project Green Cement – to increase the use of extenders like fly-ash and slag from other industries. This allows the reduced use of clinker – the main consumer of energy in the production process – while making more use of extenders.

We are probably South Africa’s leading company in our understanding and application of extenders in cement,” said Meyer. “This field holds considerable scope for creating more environmentally friendly cements. We are pleased that we have developed the technical expertise to do this.”

In 2009, AfriSam was the first in the industry to introduce a CO2 rating system. This indicates the carbon footprint of each of its cement products, relative to Ordinary Portland Cement (OPC). Indeed, the initiative has gone beyond cement manufacture. Even AfriSam’s other construction materials – aggregate and ready mix concrete – receive a carbon footprint rating. This may also be an industry first, argued Meyer.

Carbon tax

The carbon tax recently introduced in June 2019 will be another pressure for many South African CO2-producing sectors, but also brings opportunities, he said.

There are many good concepts that industry has developed to save energy and CO2 emissions, but the depressed economy has dampened their application,” he said. “Carbon tax revenues could be channelled into incentives that promote energy-saving innovation, with good effect. This would ease demand on Eskom’s grid, contribute toward the country’s Paris Agreement obligations, and make our industries more competitive.”

The company’s environmental efforts include the maintenance of a dedicated Nature Conservation Trust for the full rehabilitation of quarries and mining areas after the closure of operations. It also includes collaboration and support for important players in the conservation space such as the World Wildlife Trust and Cape Nature.

MAZIYA AT WORK ON SA’S NEWEST PATHOLOGY LAB

Johannesburg will soon boast one of the most modern forensic pathology laboratories in the southern hemisphere, with work proceeding apace alongside the Helen Joseph public hospital near Auckland Park. Construction is being undertaken by black-owned contractor Maziya General Services, partnering with construction materials leader AfriSam for its supply of readymix concrete and bagged cement

MAZIYA AT WORK ON SA’S NEWEST PATHOLOGY LAB

Johannesburg will soon boast one of the most modern forensic pathology laboratories in the southern hemisphere, with work proceeding apace alongside the Helen Joseph public hospital near Auckland Park.

Construction is being undertaken by black-owned contractor Maziya General Services, partnering with construction materials leader AfriSam for its supply of readymix concrete and bagged cement. When completed in May 2020, the new Johannesburg Forensic Pathology Laboratory will become the main centre for these pathology services in the city. It is being built for the Gauteng Department of Infrastructure Development.

In addition to the laboratories themselves and the related office space, the building will also include educational facilities as training is an important element of the facility’s role. The building therefore includes a double-volume, state-of-the-art auditorium, according to Chris Delport, managing member of Maziya General Services. This will serve the universities in the area, and the nurses training colleges.

AfriSam is the supplier of choice for the supply of the projects bagged cement and readymix requirements

The building’s façade is a Grade 2 smooth concrete finish with no treatment, so care is taken to achieve a uniform colour throughout. To ensure a high quality finish, AfriSam constantly optimises the mixes supplied, says AfriSam territory manager Antonio Benjamin.

As the building is Green Star rated, the concrete being supplied contains slagment as an extender and this reduces the carbon footprint of the product. Standard mixes use 50% slagment, while enhanced mixes use 28%.

A total of over 15 000 m3 of readymix concrete will go into the project by the time it is complete, says Benjamin. Supplied from AfriSam’s Prolecon plant, readymix deliveries began in August 2017 and will continue until the finalisation of concrete work around May 2019. The readymix has been provided in three strength categories – about 260 m3 of 15 MPa for blinding, 10 500 m3 of 30 MPa for the in-situ casting of slabs and 1 300 m3 of 40 MPa for the columns and walls.

15 000 m³ of readymix concrete will go into the project by the time it is complete

 

Earthworks kicked off in October 2017 and continued for about three months, says Delport. Considerable levelling was required due to the slope on the site, with 15 to 20 metres of excavation required.

Following the earthworks stage, extensive piling, to accommodate the stepping on the sloping ground, was done for the four different levels. Over 200 piles – usually 450 mm or 600 mm in diameter – have been driven and poured to a depth of eight to 10 metres. He says that various ground conditions were dealt with, including quartz, hard-scale and sand. The piling was completed by early 2019, and pile caps were then poured on which columns could be constructed.

The building includes a basement at minus 2 level, where there will be parking and service rooms for generators, water plants and heaters. Above the basement, three floors are being constructed, completed with a roof slab. After completion of the concrete work, there will be some limited brickwork with partitioning and aluminium window frames and glazing. Maziya General Services will manage subcontractors and take the building through to full finish, where it can be handed over as a fully functional laboratory.

Between 50-70 young workers from the local area have been employed and upskilled over the project’s two-year construction period

The project is an Expanded Public Works Programme (EPWP), one of government’s key initiatives for providing poverty and income relief through temporary work for the unemployed. The programme provides an important avenue for labour absorption and income transfers to poor households.

We employ between 50 and 70 young workers from the local areas and upskill them over the project’s two year construction period,” says Delport. “This is an important strategy for us to be able to ‘give back’ to the community in the way we conduct business.”

With management, administration and subcontractors on site, there are about 150 people working on the project at any one time, he says. Maziya General Services deploys a range of its own large and small plant on the project, including a tower crane, two mobile cranes, a water bowser, tractor-loader-backhoes (TLBs), excavators, bobcats and compactors.

As the building is Green Star rated, the concrete being supplied contains slagment as extender and this reduces the carbon footprint of the product

Established in 1999, Maziya General Services has expanded its offerings into the broader infrastructural development value chain. With capacity and resources to deliver a range of projects, it holds a Grade 9 rating from the South African Construction Industry (CIDB).

Our multi-disciplinary skills base means that we can offer a single-point responsibility to our clients,” says Delport. “We are known for delivering solutions to clients on time and within budget in a socially and environmentally responsible manner.”