With loads of evidence pointing to the effectiveness and importance of socially distanced gatherings, Sephaku Cement explores creative concrete outdoor entertainment areas that account for safe social distancing, air flow, convenient fittings for handwashing and hygiene while accounting for elegant design and decorative concrete features.
Having spent the better part of 2020 isolated and socially distanced, as communities emerge from more restrictive corona virus alert level lockdowns, creating safe and distanced outdoor areas where we can once again welcome family and friends back into our homes is an important consideration.
French Country Harvest Tablespaces
Some of the most welcoming concrete outdoor seating ideas are found fitted with an extra length hardwood harvest table elegantly place on easy to clean concrete stained floor decking. Framed by overhanging vines or flowering creepers and perfectly placed brass outdoor taps and concrete basins made to match the raw outdoor concrete styling, not matter the season covered outdoor harvest tablespaces create a warm countryside feel with the convenience of conveniently placed hand washing stations and socially distanced seating arrangements in an open-air, concrete outdoor setting.
Santorini Rooftop Concrete Decking
Where space may be a challenge, converting balcony dead-space or underutilised rooftop decking into a crisp clean outdoor concrete lounge area styled in classic Santorini Greek-styled finishes, using screed, stained, mosaiced and white painted concrete can be effectively styled to create a gorgeous lounge-like decking with 360 degrees views of your surrounds and clean outdoor air flow, together with spaced seating arrangements.
Concrete Greenhouse Pavilion
A greenhouse party pavilion with stackable, foldaway doors that invite the outdoors in or the indoors out depending on how you look at it. Finished with a minimalist concrete screened floors, stained or simply sealed as is, together with screed concrete pillars made to match and strategically placed to pitch skylighted roofing and the guided framework for stackable or foldaway glass doors. Fully aerated and fitted with a guest washroom that makes hand washing convenient and inexcusable, greenhouse entertainment areas offer a beautiful alternative to decorative concrete outdoor areas.
Grey stained and seamless stonelike concrete fittings create much like a Japanese Zen garden immersing guests into a serene outdoor setting. Styled with baby bamboo shoots, dark and mossy koi ponds and dark wood decking and bridges, concrete hand washing basis and smart self-disinfecting surface treatments. In fact, while some may opt to treat surfaces and door handles with self-sanitising technology, concrete is one of the easier materials to clean and sanitise pre and post visitors. Kept warm and welcoming should the evenings cool off, modern concrete outdoor fireplace fittings can be well placed in the form of fire bowls of pillars to finish off this modern-day look.
As the summer season welcomes warmer weather conducive to outdoor entertaining, coupled with the return to controlled social gatherings and family get-togethers, outdoor entertainment areas are the better choice when hosting group gatherings at your home as these spaces allow for optimised airflow. Adhering to the various guidelines and safety precautions aligned to controlling the spread of the Corona Virus, Sephaku Cement encourages the continued used of masks or face shields, frequent handwashing and sanitisation, regular surface cleaning, limited physical contact and continued social distancing when in the company of others.
Strengthened by different types of concrete reinforcements Sephaku Cement discusses steel concrete and the risk of corrosion caused by embedded metals in concrete fittings.
Durable, low maintenance and one of the most widely used building materials in all forms of construction, reinforced cement concrete or RCC offers both bearing strength as well as tensile strength in various concrete applications. Reinforced using steel rods or rebar (reinforcing bars), mesh, wires or cables results in steel reinforced concrete often referred to as steel concrete. Offering added resistance to tension and compression, the tightly twisted steel rebar strands help to create a rope like reinforcement that can anchor itself in cured concrete while also offering the same propensity for expansion and contraction as the concrete itself. While successfully incorporated in several civil engineering projects, domestic buildings, foundations, lintels and even underwater projects an important element to factor for when making use of steel reinforced concrete is the corrosion of embedded metals in concrete fittings.
What is Steel Corrosion?
Described as an electrochemical process that sees the flow of electrical currents between electrons and ions, together with chemical reactions between two or more metals and compounds in both steel and concrete, the corrosion of streel reinforcements and other metals embedded in concrete causes a corrosive attack on the concrete that can be dangerous and costly to repair.
Possibly one of the most common causes of damage to the otherwise stronger forms of concrete, moisture and oxygen are the leading culprits that cause the corrosive effects on steel concrete fittings.
When exposed to various environmental factors including humidity coupled with oxygen these elements act as the catalyst that sets in motion the corrosive effects on steel rebar embedded in reinforced concrete. This corrosive activity results in the rusting effect of embedded steel and other metals which is responsible in compromising the strength of steel reinforced concrete.
Avoiding the Corrosive Effects Steel in Concrete
It is no secret that concrete and water go hand in glove and given the porous structure of cured concrete, the presence of oxygen in its sponge like make up is inevitable. And while we now know the electrochemical process that causes corrosion of steel embedded in concrete can be attributed to oxygen and moisture (amongst other elements) there are various precautions that can be taken to prevent or reduce the rate of corrosion and the inevitable damaged caused to steel reinforced concrete.
- Employ the help of “crack-free” concrete making use of low permeable concrete. Preventing undue exposure to moisture and oxygen, making use of higher cement contents resulting in higher strength concrete and less porous. The cement being alkaline will afford sufficient protection to corrosion of the steel. The passivity layer as it is called actually consists of “Beta-Gamma Ferro oxide”. Low water to cement ratios again resulting in higher strength and less permeable concrete which will help to reduce the corrosion rate of embedded metals in concrete.
- Adding a corrosion inhibiting admixture to cement mix blends will also help reduce the rate of corrosion of embedded metals.
- Contractors manually reinforcing concrete applications may also opt to coat the reinforcement rebar using a resin sealer before embedding the steel in the concrete or could opt to use a different material for the steel e.g. Stainless steel or may opt to have the re-bars galvanised..
- Sealing concrete structures with a membrane or surface sealant will also help prevent the absorption of moisture into the body of the concrete fitting at a surface level.
Placing reinforced concrete fittings under even greater tensile stress that results in spalling and often hazardous cracks, paying close attention in adhering to safety guidelines and best practices that help to prevent the corrosion of embedded metals in concrete is a function not to be overlooked by contractors, civil engineers or home improvement enthusiasts.
Used in almost all large-scale civil engineering projects as well as domestic building projects such as foundations, lintels and loadbearing fittings, Sephaku Cement explains how to reinforce DIY concrete installations. Durable, low maintenance and made to stand the test of time, while concrete is one of the stronger building materials to use, when over exposed to the elements, incorrectly mixed and poured or placed under load-bearing or tensile pressure it can be vulnerable to cracks and compromised strength.
To follow, see Sephaku Cement’s Step by Step process on how to create your own DIY steel concrete reinforcements for home-based projects.
- Step One: Prepare your subgrade
No matter what your DIY home improvement project may be, always be certain to spend an adequate amount of time preparing the subgrade on which you plan to place the concrete. Begin by clearing the surface and removing stones, rocks and any debris that may prevent a level pour. It’s also recommended that the surface is compacted and further smoothed out by making use of a tamping rammer, plate compactor, roller or hand tamper.
- Step Two: Partition the area and prepare the rebar
Using timber boards to create the framework, demarcate the designated area that you will place the concrete. Once secured, using the framework as your template measure and place the steel rebar cutting it to the correct size to fit the frame. Be certain when measuring the rebar to leave around a 25mm to 50mm space between the outer frame and the rebar. Steel reinforcement should be used with a concrete strength of at least 25Mpa or more. The alkalinity of the cement will protect the steel from rust only if the compaction/vibration is sufficient to ensure complete bond between concrete and steel. Air voids and porous concrete will lead to rusting of the re-bar and subsequent detrimental cracking of the concrete.
Once measured and cut to fit, remove the rebar from the timber framework and proceed to step three.
- Step Three: Mix and Place the Concrete
Following the mixing instructions detailed on the bag of cement you are using, blend the concrete taking care to measure the correct ratios of water and aggregates required. Working quickly, you can begin to pour the wet concrete mix into the timber framework. At this stage you need only pour half of the mix, smoothing it across the full surface area. Once half full and smoothed over, place the measured steel rebar into place. Now pour the remaining half of the concrete on top of the rebar so that the steel reinforcement sits in the centre of the cast.
Allow your reinforced concrete cast to adequately cure which could take between 24-48 hours.
Once fully cured you can now remove the timber framework and proceed with the next steps of your project.
Steel concrete can also be reinforced following a similar process as the above, but instead of using steel rebar, you could also make use of steel rods, mesh, wires or cables to create your own DIY lintels, columns or decorative loadbearing concrete or reinforced retaining walls. Offering both bearing strength (increased load bearing capacity) as well as tensile strength, by combining concrete’s natural compressive strength with steel’s ability to resist tension reinforced concrete can be put to use in a number of applications that need added flexural and or tensile strength for durability.
One other exciting characteristics of steel concrete is steel’s propensity to expand and contract much to the same degree as concrete does when under the same type of influence from hot or cold conditions, what this means is that as concrete will expand and contract the steel used to reinforce the concrete will experience the same degree of growth or shrinkage, working hand in glove to maintain the structural integrity.
One of the stronger building material alternatives and certainly the most widely used in the industry, Sephaku Cement explore the different types of reinforced cement concrete or RCC. While cement based applications offer a durable and low maintenance building solution, concrete is not without its vulnerabilities when incorrectly installed or expose to harsh elements, moisture and freeze-thaw effects.
To counter these cons and to ensure the integrity of inhabitable structures is maintained, most civil engineering projects and certain structural concrete constructions make use of concrete reinforcements to ensure the structure’s bearing and tensile strength.
- Bearing strength can be explained as a structure’s load bearing capacity or its ability to carry contact pressure or weight.
- Tensile Strength is best described as concrete’s resistance to breaking under tension/bending
Fibre Reinforced Concrete
While certain concrete applications, typically those installed as non-load carrying applications need not be reinforced, others need the added strength to ensure a sound and compliant structure that is safe for use or occupation.
The added reinforcement of concrete and more specifically using fibrous materials dates as far back as prehistoric times where fibres such as straw and even horsehair were mixed with mud-like cement based material.
Much later the 20th century saw the use of fibrous materials such as steel, glass and synthetic fibres used to give rise to the various types of fibre reinforced concretes namely;
- Glass Fibre Reinforced Concrete (GFRC)
- Steel Fibre Reinforced Concrete (SFRC)
- Natural Fibre Reinforced Concrete (NFRC)
- Polypropylene Fibre Reinforced Concrete (PFRC)
- Engineered Cementitious Composite (ECC)
Other ways that concrete can be reinforced is by embedding materials such as steel rods or reinforcing bars also known as rebar, mesh, wires and cables in the concrete application which is where the term Steel Concrete comes from. In doing so the instalment or structure resists both tension and compression whereby the concrete offers a compressive strength and the steel produces tensile strength. Rebar is made of steel strands tightly twisted to form a rope-like structure which helps to keep it secured in the cured concrete. Further to this, steel is often a preferred material of choice to use when reinforcing concrete as a result of its propensity to expand and contract much to the same degree to that of concrete when exposed to both hot and cold conditions.
While reinforced concrete offers one of the most durable building solutions in construction, pre-stressed concrete delivers an even more effective reinforced concrete option and an effective solution to prevent concrete from cracking or becoming brittle under pressure. Placing reinforced concrete under pre-stress is done by applying compressive stress on the concrete before its put to its intended use, when pre-stressed concrete is eventually exposed to an external load, the pre-stress or compressive pressure applied to the concrete counteracts the loadbearing pressure on the reinforced concrete fitting offering an extremely durable and robust solution.
From fibre reinforced concrete or steel concrete reinforcements to pre-stressed or pre-tensioned concrete, reinforced concrete is used on a number of engineering projects both large and small. Employed in almost all large-scale civil engineering projects including bridges and sports stadiums, as well as water based projects such as dams and piers, reinforced concrete is also put to use in domestic applications such as foundations, columns, lintels and loadbearing walls, platforms and balconies.
As climate change and the reduction in carbon gas emissions becomes a global concern across multiple industry sectors, Sephaku Cement discusses alternative waste management processes and how recycling concrete into aggregate alternatives present the building sector with more sustainable green solutions. Reduce, reuse and recycle, these are the three most important R’s in the waste management trifecta in finding a sustainable solution to the ongoing threat that climate change poses to global ecological communities.
From plastics to paper, tin cans and glass, there are many strategies in place for households and businesses to cut down on the amount of waste thrown away on a daily basis. As the need for more sustainable waste solutions becomes paramount, the construction and civil engineering sectors are also playing their part in repurposing and upcycling waste and rubble resulting from various civil engineering projects.
From concrete driveways that need to be replaced, to precast pathways, pavements or refurbishing concrete fittings, aged, damaged or compromised concrete installations can be effectively recycled into an affordable and eco-conscious aggregate. A critical component in reinforcing concrete applications, aggregates create the volume and added durability that Portland cement binds to resulting in the compressive strength of various concrete installations. Natural aggregates such as stone, sand and crushed gravel, are both costly and a non-renewable resource derived from natural sources, however, when upcycling aged concrete fittings that are being replaced or refurbished, recycled concrete offers an eco-conscious and sustainable solution as a natural aggregate alternative effective in reinforcing new concrete applications.
Although not a totally new concept, many concrete installations are 100% recyclable with this process put into practice in Europe since the 1940s. Recycled concrete aggregate (RCA) offers both cost saving as well as various environmentally sustainable benefits that include;
- Conservation of natural aggregate resources
- Sustainable building waste and rubble management
- Reduction in landfill consumption Energy and
- greenhouse gas emission reductions
The production process of recycled concrete aggregate includes breaking up the old concrete installation which is then collected and hauled to a crushing plant. The demolished concrete is then crushed into specified sizes and quality grades and then sorted and further refined into batches of consistently sized aggregate material. In most cases, recycled concrete aggregate is produced to meet both the quality and grading requirements that can be used in a diverse selection of new concrete applications. In other instances, an alternate recycled concrete aggregate can be created when demolished concrete is blended with other building waste materials such as wood. This material is produced to result in a totally new aggregate material that offers a more pliable or bendable strength put to use in more specific concrete projects.
“RCA particles – which tend to be extremely angular – consist of reclaimed virgin aggregate, reclaimed mortar or both. Reclaimed mortar generally has higher absorption, lower strength and lower abrasion resistance than most virgin aggregates. RCA therefore generally has lower specific gravity and higher absorption than virgin aggregate.”
“The properties of a specific recycled concrete aggregate depend upon many factors, including the properties of the original concrete and the processes used to produce the RCA, particularly the crushing operations. With proper process control, RCA can be produced to meet quality and grading requirements for almost any application and should be considered an engineered material for which the properties must be determined at the outset so that appropriate mix design or construction adjustments can be made.
“When RCA is used in the production of new concrete mixtures, its effect on the properties of those mixtures can range from minimal to significant, depending upon the nature, composition and gradation of the RCA. For example, when little reclaimed mortar is present in coarse RCA and virgin fine aggregate is used, the handling characteristics and engineering properties of the new concrete properties will be practically the same as if all virgin aggregate had been used. But if the new mixture contains only coarse and fine RCA, these characteristics and properties will be substantially different from traditional concrete mixtures when all other mixture design factors remain constant.”
With the hopes to reduce construction costs and the added benefit of reducing carbon emissions, as the cement and construction sector continues to pursue more "green" building practices, the production of recycled concrete aggregates offers a number of added benefits. While addressing the growing concerns of climate change and waste management solutions, recycled concrete not only addresses a more environmentally sustainable alternative to natural sand and stone aggregates, but also stimulates a circular economy that offers society wide benefits and job creation.
Reshaping the future of construction and eco-conscious architecture, sustainable building practices take centre stage as South African contractors and civil engineers shoot for the “green” stars! With a growing commitment to creating eco-conscious, “green building” precincts, green star buildings have taken shape across South African landscapes. To follow, Sephaku Cement showcases two all new and pioneering concrete buildings and properties that have been built with as little environmental impact as possible while offering long term sustainability.
Discovery Head Office – Sandton Johannesburg
Incorporating both mechanical and environmentally sustainable designs, the new Discovery head office located at 1 Discovery Place, Sandhurst in Sandton Johannesburg holds a Five (5) Green Star rating. Assessed by the Green Building Council of South Africa, One Discovery Place was developed by Growthpoint Properties in a joint venture with Zenprop Holdings.
Taking into consideration the health and well-being of its employees while checking all the boxes as a world-class sustainable building, One Discovery Place is said to be one of the largest and greenest buildings in Africa. Having taken just under four (4) years to complete the building made up of eight (8) levels of office space structured across a 3-tiered layout that includes a data centre and feature roof level covers around 150 000 m2. From energy efficient lighting, to grey and rainwater harvesting applications, water conscious sanitary systems and a carbon monoxide monitoring feature fitted to the basement, while the structure offers an incredible aesthetic to the Sandton CDB skyline, the curved facade also plays a role in the buildings thermal heat control.
As part of these eco-efficient strategies fitted to the building, engineering and construction also included the responsible use of building materials and waste management handling. With its architectural focus aimed at well-being and movement, the new Discovery Head office also offers a rooftop running track, an indigenous landscaped roof garden, staircases designed to encourage staff to use stairs instead of elevators and its largest atrium measuring the size of a Boeing 737.
Cintocare Hospital, Menlyn Main Pretoria
The first facility of its kind in South Africa and the first specialised surgical hospital in Africa to be awarded a Five (5) Green Star Custom Healthcare design certification from the Green Building Council South Africa (GBCSA), let’s find out more about the Cintocare Hospital in Pretoria.
A collaboration between Growthpoint Properties and Cintocare, the Cintocare Hospital has been engineered to bring both a positive social and environmental impact to is surrounds. Creating a sustainable healthcare facility that supports the well-being of patients, the environment and local communities, the 11 000 m2 hospital covers seven (7) floors including the hospital plant room, three (3) clinical and consulting levels. The 100-bed hospital, with the capacity to expand to 160 beds will also host five (5) theatres, one of which is a hybrid. The site’s green building rating has been achieved through architectural design and various sustainable design principles incorporated into its engineering. Further to this, this particular collaboration between Growthpoint Properties, Cintocare and GBCSA has resulted in an all new green building certification tool which will be used to drive the development of other green healthcare buildings in South Africa.
As eco-conscious architecture, sustainable building practices and green building practices continuing to guide civil engineering and property design principles, we look forward to showcasing more Green Star buildings that lead the South African construction sector into the future.
With a splash of motivation, a little bit of know-how and only the finest quality Portland cement, explore some of Sephaku Cement’s most inspired outdoor concrete design features. While the winter months are inclined to keep us bundled up indoors, it’s actually the ideal time to spruce up your outdoor entertainment area and other garden landscaping, allowing ample time to start and finish your DIY home improvement projects before the turn of the season. Again your success and designs are only limited by your imagination - if you can imagine it you can build it
Sephaku Cement showcases some of the simplest Outdoor Concrete Design Features that can be incorporated into your DIY concrete projects with little to no building and landscaping experience.
Embedded Concrete Lighting Features
From dainty down lights to uplight garden landscaping, concrete design installations that incorporate light fittings embedded within the concrete application create a seamless flood of illumination, delicate enough to add to the ambience while still offering an effective outdoor lighting solution. From LED lit concrete pathways, to cement paver dots, subtle uplight garden edging or the sheer magnificence of concrete column lighting to increase height and added drama, concrete creates the ideal capsule to produce a subtle glow to any decorative outdoor concrete design.
Path Maker Paving Moulds
Possibly one of the simplest ways to landscape garden pathways without the help of a concrete contractor, pathway paving moulds are designed with the home improvement DIY enthusiast in mind. A user-friendly solution to pave tea gardens, outdoor entertainment areas, cladded pathways, courtyards and even cobbled driveways, paving moulds are available in a variety of designs and details that produce an expert finish at a fraction of the cost. Making use of two or more moulds at a time (for a more speedy application) depending on the finish you wish to achieve paving moulds can be placed to create a repetitive design or rotated in alternate patterns to create a more random arrangement.
Concrete Retaining Walls
Ideal for homes and gardens landscaped on a slope, concrete retaining walls offer a minimalist sophistication, and modern flare to its functional purpose. Sculpted around the sloped banks of your garden landscaping, concrete retaining walls can be used to create decorative flowerbeds and beautifying embankments and shelfs that make it easier to manoeuvre around otherwise steeply sloped gardens. Placed using timber frame casting moulds customised to any design you can imagine, this simple decorative concrete feature can be fitted with a smooth sand-finish or textured with concrete stamping or etching made to fit any theme or concrete design concept.
Concrete Braais and Fire Pit Fittings
Heat resistant and made to last a lifetime, concrete braais, modern fire pits and decorative concrete fire bowls add a refined finish to every outdoor entertainment area. While some may opt for brick and wrought iron alternatives, concrete braais and decorative fire pits can be built to make use of a variety of fuels including wood, gas and other fuel alternatives. Able to withstand any heat produced while also offering a diverse selection of design options, get your garden looking gorgeous with a fire pit, decorative concrete fire bowls and customised concrete braais.
While many Portland cement concrete projects can prove to be successful with “do it yourself” instructions, even the most experienced home improvement enthusiast should know when to call a professional. Although seemingly simple to measure, mix and pour there are some instances when the help of a professional concrete contractor may be required to avoid common concrete blunders.
Here to point out common challenges faced when working with concrete on DIY projects, Sephaku Cement highlights common concrete blunders and when to call for back up.
Preparing the subgrade is one of the most critical steps in any concrete application regardless of whether the project is DIY or commissioned by a professional contractor. Forming a stable and sound foundation for any concrete application to stand on will determine the ultimate strength and crack resistance of the surface. When installed on poorly compacted, uneven and irregular subgrade, concrete applications will eventually result in cracking and crumbling as the foundation shifts underneath the weight of the fitting. Call in a contractor who can assist with the correct compacting equipment to ensure that the subgrade is of the correct quality and adequately prepared to withstand the weight of the application without shifting or buckling under the pressure of the installation.
Unexpected Weather Interference
Where variations in the weather bring about varying ambient conditions that can influence the pouring and curing of Portland cement concrete, although weather interference usually only occurs under extreme conditions, there are some instances, most of which are unexpected and almost always take place when working on a deadline or during the most critical part of the job that can hamper the success of your home improvement project. Call on a concrete expert when the summer pouring temperatures exceed 32 degrees celsius and pay careful attention to curing in below freezing conditions. While wet and rainy conditions may not be terribly detrimental, too much hydration too quickly can be as damaging as drying too fast.
Armed with adequate skill may be only as effective as the tools you have available to work with. From something as simple as a wheelbarrow to a small-scale concrete mixer, a hard bristle brush, float leaves and finishing trowel, the complexity of your concrete project will determine the specialised tools required to work with. Without the appropriate equipment to complete your job to perfection rather call on the help of concrete suppliers or equipment rental services who will be able to provide you with the necessary resources to produce the perfect concrete finish.
Perhaps not necessary to call on an expert to correct, but consulting an expert couldn’t hurt. By now we know that measuring the correct ratio of water to cement, to aggregate is an art that must be perfect if you want your DIY concrete project to result in a durable and crack free application. Depending on the desired finish, strength, and purpose, the best construction tips will advise that while additional water may make concrete pouring easier to work with, incorrect water ratios will result in an uneven pour and weakened/cracked concrete finish. Don’t be tempted by adding additional water when blending, slow and steady wins the race when producing the ideal concrete mix.
Working with the correct type of cement for the job, careful planning and adequate preparation are all the markers that make for a successful concrete application, but much like following a recipe from your favourite cookbook, if one step is overlooked, the measurements don’t add up or the ingredients are not of sound quality, a lot can go wrong, hard and fast.
Offering a workable alternative to traditional concrete foundations, concrete garden pavers, outdoor entertainment areas, seamless driveways and garage flooring, find out how to fit concrete slabs as a DIY project at home.
The beauty of concrete slabs is they can be poured and placed in just about any shape, colour or surface texture imaginable as long as the form fits the function, what's more, placed on well prepared and compacted sub-grade, concrete slabs offer lasting durability at a fraction of the price compared to painstakingly mapping the route of intricate foundations, outdoor entertainment areas, patios and pavers.
The key to pouring a concrete slab lies in the preparation of the subgrade, where preventing cracks and fissures depends on the base the concrete settles on and how well the slab is protected from moisture absorption. Concrete slabs can be further reinforced using vapour barriers and a combination of rebar, wire-mesh or even fibre-mesh for added durability and load bearing capacity.
Placing concrete slabs at home can be a fairly simple process to follow with the devil in the detail of preparing a balanced, primed and well compacted subgrade. Together with a crushed gravel base to prevent natural sinkage from weight and added pressure and further reinforced by a level and compressed soil subgrade, concrete slab foundations and flooring will refrain from sinking or cracking even under the most extreme South African weather conditions.
Creating a concrete slab for beginners starts with the assembly of a sturdy timber frame to define the perimeter of the concrete base. Once enclosed around a well-prepared and compacted subgrade that has been finished with stone gravel, the gravel acts not only as an added layer of reinforcement on top of the subgrade but also as an effective filter preventing groundwater runoff and causing moisture to move away from the concrete slab.
Before pouring your wet concrete into place, wet subgrade slightly to avoid sucking the water out of the concrete, secure wire mesh or rebar inside your shuttered area ensure that the reinforcing is not laying on the gravel surface by lifting it to approximately centre of the slab using some bigger stones or commercially available spacers, which acts as concrete slab reinforcement, effective in increasing the load bearing capacity especially in frequent and weighty traffic zones such as driveways and garage flooring. Another detail to consider when pouring wet concrete to form a concrete slab is to do so at a very slight and gradual slope which will help water or moisture build up to run off instead of pooling in one focused depression in the slab.
Strategically beginning at the highest point of the slope, carefully pour and screed concrete into the timber frame and using a screeding tool flatten the wet concrete by sweeping the mix back and forth to create a uniform surface. Moving from the top of the slope to the bottom, create a flattened concrete surface that can then be compressed using a floating device to press aggregate gravel beneath the visible surface while offering a smoothed out and creamy finish.
Next, make use of a groover to insert measured control joints every 2 meters which will ensure the concrete slab is able to endure thermal expansion and contraction and control the position of cracks to be directed to the predetermined joints as opposed to unplanned and unsightly random cracks. (The rule of thumb is that slab sizes do not exceed the following size. Slab size must be preferably less than 32 X Thickness of slab. E.g. if you intend to cast a slab with a 100mm nominal thickness the slab / block sixe should not exceed 100 X 32 = 3.2 meters)
For outdoor concrete slab installations keep in mind that surfaces will become slippery underfoot and adding traction is considered best practice especially when surrounding wet surfaces such as pool decks, outdoor entertainment areas and garden walkways. Traction can be easily created by simply using a stiff bristle brush to sweep gentle grooves onto the smoothed surface of concrete slabs. Alternative options include incorporating decorative stamping or finishing cured concrete surfaces with a grit sealant.
Whether you have a large or small concrete surface area to clean, removing dirt, grime and debris from concrete surfaces at home can be done quite professionally by applying a few basic care principles.
Indoor and outdoor concrete surfaces can be successfully cleaned without the help of professional cleaners with a few household supplies most of us already have available at home, but there is a place for professional cleaners as well, especially when concrete surfaces are largely soiled or have not been cleaned over a long period of time, the long term build-up of dirt, stains and marks caused by grease may need the help of a professional to get these cleaned.
It's also important to keep in mind that concrete is caustic and susceptive to corrosion and damage caused by compounds that trigger a chemical response. When cleaning concrete surfaces finished with epoxy coatings, colour stains, sealants or polished concrete floors make sure to clean these with a PH neutral detergent to avoid damage to these decorative surfaces.
Cleaning concrete surfaces without any professional supplies
Whether you are trying to remove, oil, grease marks or organic matter from indoor and outdoor concrete surfaces, large or small concrete surfaces, including those treated with a PH sensitive finish, can be cleaned safely by using a mix of dishwashing liquid and warm water. Creating a warm soapy mix of 30 millilitres of dishwashing detergent with 20 litres of water and gently scrubbing the surface with a soft bristle brush (or a broom for larger surfaces areas) is an effective way to remove every day dirt and trivial stains and grease mark from porous concrete surfaces. As the soap and warm water re-emulsifies oil-based marks, the surface can then be rinsed clear with clean and untreated water.
Cleaning concrete surfaces with a stronger home solution
It's important to note that using an acid or alkaline cleaning solution may provide a more effective result, however, these can corrode, discolour and peel decorative concrete surfaces, epoxy coatings and coloured stains and polishes.
While there are many natural solutions to cleaning concrete surfaces, these may not always be PH neutral.
For example, mixing 1 part vinegar to 1 part of warm water, or 10 millilitres of lemon juice to 1 litre of water makes for a stronger cleaning solution, both vinegar or lemon juice (in its natural state) are high acid cleaning solutions perfectly fine to be used on untreated concrete, but should be avoided when cleaning decorative concrete surfaces.
Another home solution stronger than dishwashing liquid and water is a solution made of 1 cup of bleach and 2 cups of bicarbonate of soda mixed in 20 litres of water (for very stubborn oily stains a 10ml Ammoniac can be added to this solution and then care must be taken not to inhale the fumes – cover nose and mouth with a wet cloth). Especially useful in removing mould and mildew, this solution has a high alkalinity and will have an equally damaging effect on surface treated concrete in the same way as high acid cleaners do. If cleaning surfaces from oil where it is not going to matter if there is a colour change, white spirits can be used (white spirits tend to leave white stains/marks on concrete).
Alternative cleaning methods that are effective and require the least amount of manual labour include the use of high-pressure washers for outdoor surfaces or steam cleaning machines for indoor and decorative surfaces, where both are pet friendly, non-toxic cleaning methods that are especially useful on larger surfaces.
While a common assumption that pouring concrete in wet/rainy weather presents more favourable curing conditions, see Sephaku Cements top tips and tricks to pouring concrete in rainy climates making sure your concrete pouring project is a solid success.
As one of South Africa’s provinces moves from a hot and wet summer, another one of our provinces are lined up for a cold and rainy winter which means inevitably South African concrete contractors will all be required to pour concrete in wet and rainy conditions at some time during the year. While concrete and water go together like a hand in glove, there are very specific guidelines that should be followed under wet and rainy conditions to make sure the integrity of your concrete project is not compromised by unpredictable summer thundershowers or weeklong soft soaking rains. As with so many things in the concrete construction business, success is largely put down to the timing of things, whereby with planning and a little bit of forethought, even the most disastrous conditions need not stop your progress.
Plan Around Weather Forecasts
While it’s neither a fool-proof method nor wise to place all of your faith in the weather forecast, a good place to start is by planning your concrete pouring project around expert weather predictions. With a number of resources that offer a near accurate seven to ten-day weather forecast begin by keeping a close watch on the coming weather predictions planning your project around the drier days than on the scheduled wet ones. No matter how much pressure your project may be under, it’s always a smarter choice to postpone pouring until drier conditions if the weather forecast predicts wet/rainy weather.
In the case of an unpredictable summer thunderstorm, hard and fast rain can negatively affect newly poured concrete, causing the surface to become over saturated and soft, compromising the overall strength and increasing the risk of cracking once cured. If your concrete project has been poured within a few hours of a fast-moving thunderstorm try to protect the surface of the concrete by erecting a temporary shelter above the worksite even if this is effective enough to deter just some of the downpour.
Sweep Away the Excess
Once a sudden downpour has come to an end, never try to blend excess rainwater into poured concrete, remember that the correct water to cement ratio must be adhered to in order to ensure the concrete cures with its required strength. Provided that doing so won’t damage or deface the desired finish, try to push or pull excess water from the surface of recently poured concrete. If the concrete was placed between four and eight hours prior the rain setting in, you need not be concerned with removing any excess water from the surface.
Pouring Concrete After the Rain
While waiting for the rain to subside before placing new wet concrete, it’s important to note that wet concrete should never be poured into a hollow filled with water or cavities and groves that are filled with remaining water or runoff. By doing so, much in the same way as rain falling and pooling onto the surface of concrete, concrete poured into a puddle of rainwater will adversely affect the water to cement ratio compromising the strength and consistent curing of your concrete project.
While concrete contractors can on the most part operate all year round, as seasons change bringing about varying weather conditions, see Sephaku Cement’s top tips and guidelines on seasonal concrete pouring.
Known for its warm and mostly sunny days, South Africa’s weather ranges between Mediterranean to Subtropical climates where conditions are typically influenced by the differences in the county's varying
landscapes. While conditions are rarely extreme, temperatures are known to plummet a few degrees below freezing in winter, both summer and winter rains are encountered depending on the region you are working in and high summer temperatures can see the mercury rise in close vicinity and in some provinces even over the 40°C mark.
Variations in the weather bring about varying ambient conditions that can influence the pouring and curing of Portland cement concrete to follow see guidelines for curing concrete in different South African seasons.
Pouring concrete during a scorching African Summer
South Africa Summer temperatures are usually above 32°C countrywide and, in some regions, often peaking up to 38 °C, temperatures, humidity and wind factors will each play their role in influencing the rate and consistency of how wet concrete cures. While Portland cement concrete is not particularly fussy when it comes to weather conditions, careful attention needs to be paid to keeping the curing speed and process consistent.
Where temperatures climb above 32°C concrete contractors need to take care that the surface of poured concrete are kept cool. To do this, begin by making sure that the materials you are using are kept
in a cool place or could be kept cool with a fine mist sprayer whereby for example if aggregate sand and stone has been left to bake in the sun, this will just add to the rise of the concrete temperature above 32°C. Another tip when mixing concrete in hot conditions is to make use of cold water (some contractors often especially when pouring mass concrete like dams where heat of hydration contribute to internal concrete temperatures, even go as far as using ice as a water substitute) and once poured into
place keep the concrete surface moist by lightly watering it with the sprinkler or a fine mist.
Pouring concrete under cold conditions
While daytime winter temperatures in South Africa rarely reach below freezing, night-time temperatures in the dead of winter can often plummet into negative numbers on the thermometer. Concrete cures at a slower rate in cooler temperatures which, if kept above freezing are favourable conditions for optimal curing. However, if the ambient temperature reaches below freezing the risk is that the water in wet concrete may freeze before it cures. When water freezes it expands which will result in larger pockets in between the already porous structure of cured concrete and could potentially even crack concrete if it has not reached at least 5-10 MPa. So what’s the issue you may ask? If allowed to freeze, pouring concrete in below 5°C and falling freezing temperature will increase the risk of cracks and fissures as a result of the freezing water in the concrete. To keep curing concrete from freezing in winter begin with mixing combined materials with warm water and conversely to summer tips, let stone and sand aggregates sit in the sun if any, to increase the ambient temperatures as much as possible. Plan concrete pours to take place early as possible to allow strength of 5-10 MPa to be reached before temperatures fall below zero°C. Most contractors will also leave shutters on and insulate the open surfaces with polystyrene when casting mass concrete in the winter to prevent the temperature differential between inside and the concrete surface to go beyond the allowed 17°C. Another tip is to make use of early strength cement that has been blended with various additives to influence the strength class and strength gain pattern of the concrete. Using products such as Sephaku 32,5R or Sephaku 42,5R where the R denotes rapid strength gain Portland cement means that the cement has been engineered to deliver an improved early strength and rapid curing.
One of the leading causes for major structural damage to homes, schools and places of business, learn to identify tell-tale signs of distressed foundations, what is causing this to happen and the risks associated to damaged concrete foundations.
Much in the same as a chain is only as strong as its weakest link, structures and standalone fittings such as boundary walls and other applications placed on concrete foundations, are only as steadfast as the foundations they are built on.
While water or ongoing exposure to moisture is typically the primary cause of damage to any concrete installation, there are a few other factors that have a hand in causing damage to concrete foundations that include;
Subgrade Soil Type and Preparation
Typically clay type soil is guilty of becoming expansive both by swelling and contracting depending on the water content present. Comparatively sand type soil can lose traction and sift with time creating an equally unstable surface for long term foundations. While soil type should always be a consideration for sound foundations, so should the preparation of the foundation’s subgrade. Using an infill material from a good quarry is an alternative if insitue material is not sufficiently stable for a proper foundation, subgrade should also be effectively compacted to prepare a stable and compressed surface on which to place steadfast foundations.
Improper water drainage
Pooling in and around foundations, if rain water or irrigation run off is not adequality drained away from foundations, ongoing exposure to water that is absorbed into the air chambers of concrete will freeze and expand, thaw and retract forcing the concrete to become brittle and distressed over time.(not common in South Africa except can occur in very cold/high altitude places like Lesotho)
Extreme Weather Conditions including floods or droughts
Also influenced by the presence of water or moisture in the concrete matrix, extreme weather can have a negative impact on concrete. Whether too much moisture, freezing temperatures of extreme heat and dry spells that can evaporate moisture, each of these conditions eventually erode concrete foundations.
In areas of increased seismic conditions, earthquakes can wreak havoc on concrete foundations as the surface of the earth shifts, shudders, rolls and shakes concrete installations during an episode. Damage is not only cause by movement originating from beneath the surface of the earth, but the shift in pressure of the construction on top of the foundations.
Surrounding Influences such as tree roots and other subgrade disruptions (like big boulders in surrounding soft sandy soil).
Exerting pressure on surrounding soil or directly intruding on concrete foundations, the roots of large trees are known to cause some significant damage to concrete foundations. Leaching moisture from soil and subgrade, uprooting slabs and even bursting underground water pipes flooding foundations, tree roots should always be a consideration when planting to nearby construction. (best to involve a horticulturist)
Regardless of the cause, damaged concrete foundations compromise the integrity of the structure in question while also having a negative impact on the property’s value and cause unsightly blemishes like cracks and surface warping even requiring to demolish buildings with severe foundation damage, to name a few.
So, what are tell-tale signs that your foundations are damaged or in need of repairs?
While all new construction settles into place with time, if foundations are insecure and of not sufficient size or strength and under duress, there are very apparent signs to tell foundation issues apart from slight and organic shifts.
The most obvious signals that foundations are unstable are;
- Cracked bricks
- Misaligned doors and windows
- Cracked or uneven floors
- Wall rotation or leaning – off plumb
- Splits in masonry where brick separate form mortar
An alarming amount of homes and other structures are built on inappropriate subgrade and damaged foundations that can cause costly structural damage and more concerning compromise the structural integrity making the building a hazard and unsafe to occupy.
While hairline cracks in concrete foundations are normal and mostly unavoidable given the effect of freeze thaw expansion and contraction when exposed to water or moisture, experts estimate that if a crack is broader than around 3 mm, this could be a good indication that concrete foundations are in need of a foundation inspection and repairs by a foundation specialist. Foundation repairs are extremely difficult and not always successful, besides it being very expensive.
With early detection and effective repairs made to damaged and distressed foundations is one of the surest ways to prevent lasting and hazardous structural damage to your home/building. Often when left too late damaged foundations negatively impact the structural integrity of buildings that are too far gone to be repaired. Requiring a comprehensive rebuild from the ground up, leaving damage foundations to literally tear through any structure is not only costly but dangerous for occupants too.
Identifying damaged foundations can be done by a simple inspection of the foundations or by looking for tell-tale signs of damage to structures that may indicate distressed foundations. Structural engineers as well as a foundation repair expert will also be able to assess your property and note any concerns that should be addressed to prevent structural damage before it’s too late.
Once it has been identified that a structures foundation is in need of repair there are a few methods in which structural engineers and foundation repair specialists will approach the restoration of damaged foundations.
The most effective way to repair distressed and damaged concrete foundations is by blending the best in technologies and industry experience to apply effective solutions to damage foundation.
Today there are more effective and technologically advanced approaches to repairing foundations and where many contractors offer a lifetime guarantee on their repairs (subject to service provider).
Once having established the cause of foundation damage your structural engineer will be better advised to recommend an appropriate repair process typically being one of two methods, namely piering or slabjacking.
Just as the name suggests, slabjacking sees concrete grout used to lift a concrete slab or beam up towards a warped or shifted foundation taking on its original position. Typically used to repair sunken driveways and pavements, outdoor entertainment areas and patios, a simplified slabjacking technique can also be used by pouring concrete grout down boreholes, filling the gaps of compromised foundations with grout which then cures around the original foundation, reinforcing it from the bottom up.
Typically used to repair more extensive and significant damage to foundations, the piering method makes use of steel posts to stabilise or raise concrete foundations damaged by compromised subgrade and soil types. This method is effectively used in homes or commercial buildings and requires the opening of the damaged foundation by digging under and around it then a steel beam or posts are placed and with the help of a mechanical jack that is used to lift and secure the damaged foundation into place. Then an amount of concrete is placed around and under the damaged foundation. And left to set and gain strength.
From function to form, Portland cement can be put to task in a variety of ways and with some of the coolest uses and interesting facts that you may not have been aware of up until now. The most widely used building material in present day and with its foundations dating as far back as ancient roman concrete, cement is by far one of the coolest construction materials around given its hugely versatile and resourceful purposes.
Let’s take a look at the Top Five Things That Make Concrete Cool.
- Heat of Hydration
To the untrained eye it’s easy to assume that mixing Portland cement with water to form a paste is as simple as mixing flour with water to make glue. While the principle might be similar, you’d be mistaken to assume that there wasn’t a little bit of magic that happens as concrete creates some of the most magnificent and longest standing man-made forms in the world. The process of blending cement with water that then later cures is in fact a chemical reaction that occurs as compounds in the cement comes into contact with water. What happens next is in fact rather astounding whereby wet cement starts heating up, this process is referred to as the Heat of Hydration which sees to it that large bodies of wet cement can emit a fair temperature increase as it hydrate, set and cures.(up to 70OC in certain cases of mass concrete)
Built to last a lifetime and more
With an astounding compressive strength, it’s no surprise that some of the oldest standing constructs were originally made from earlier forms of concrete. Known as the largest unreinforced concrete dome said to have been made from a blend of lime and volcanic ash from Mount Vesuvius erected in 126AD, the Pantheon is an excellent reminder of just how steadfast and durable concrete can be. Another impressive example and a little closer to home; the Western Cape’s Castle of Good Hope is known as the oldest colonial building in South Africa and one of the world’s best preserved examples of the Dutch East India Company’s 17th century architecture. Built between 1666 and 1679 it has been explained that the cement used to erect this historic landmark was made by burning shells in lime kilns until it formed lime which was then once again mixed with shells and sand to create a concrete.
As big as it is heavy
Some of the world’s largest and heaviest structures have been built using concrete including the Three Gorges Dam in China weighing in as the heaviest concrete structure in the world at a weight of 144,309,356,753.51 pounds. The amount of material used in the building of the Three Gorges Project is staggering. Consuming 28 million cubic meters of concrete. The Three Gorges Dam is the world's largest capacity hydroelectric power station with 34 generators: 32 main generators, each with a capacity of 700 MW, and two plant power generators, each with capacity of 50 MW, making a total capacity of 22,500 MW. Meanwhile the Empire State Building in New York, United states, was built using 62,000 cubic yards of concrete and was known as the world’s tallest building until the rise of the Burj Khalifa in Dubai 2010. At over 828 metres (2,716.5 feet) and more than 160 stories, Burj Khalifa holds the following records: Tallest building in the world. Tallest free-standing structure in the world. Highest number of stories in the world. Locally the Carlton Centre a 50 storey skyscraper in downtown Johannesburg was formerly known as Africa’s tallest building but has since relinquished its title to the 55 reinforced concrete floors of the Leonardo Hotel in Sandton Johannesburg.
The most widely employed material in construction world-wide.
It’s a concrete fact that cement is the most commonly used material across the globe. After the Washington Post estimated that China’s use of concrete between the period of 2011 and 2013 exceeded the USA’s use of this popular building material throughout the entire 100 years of the 20th century, it has since been predicted that the global demand for cement will increase by almost 5% year on year calculating that the construction industry will have consumed some 4.2 billion tons of cement in 2019
(Back in 1995, the total global production of cement amounted to just 1.39 billion tons, which indicates the extent to which the construction industry and therefore the consumption of cement has grown since then.)
Concrete 3D Printing
What was once largely limited to the use of molten plastic and metal, 3D Printing technology has evolved to now employ the use of wet cement blends. Revolutionising the architecture and construction industry in leaps and bounds, concrete 3D printing technology offers an efficient and cost effective alternative in basic construction. Using a method similar to fused deposition modelling (FDM), concrete 3D printing takes place using an automated and repetitive methodology that directs a print head through a sequence of rotations. While designs may still be limited to more modest forms, concrete 3D printing can be extremely effective in the construction of high density, low cost housing in areas of high demand.
From historic concrete landmarks to more modern constructs, see how concrete has been shaping South Africa’s landscape for centuries gone by. A material so durable that today it is one of the most widely used building materials in construction, using a blend of Portland cement, various textured aggregate and water, join us as we explore various concrete constructs that line South African horizons.
- The Castle of Good Hope - Cape Town
Set against the backdrop of the Table Mountain in the Cape Town CBD the Castle of Good Hope was erected by the Dutch East India Company between 1666 and 1679 and is said to be the oldest colonial building in South Africa still standing today. Building materials used to construct this historic monument included cement created from burning shells in lime kilns which was then blended with crushed shells and sand to a durable concrete.
- Table Mountain Cable Way – Cape Town
An engineering project that saw construction workers having to carry equipment and materials to the top of the mountain before construction could begin, the Cape Town cable way took four years to build and was first opened in 1929. Making use of a temporary ropeway and an open box called the " Soapbox" to carry cement and other building materials as well as workers up and down the mountain, surprisingly the Table Mountain Aerial Cableway has remained accident free for more than 90 years.
- Orlando Towers – Johannesburg
Completed in 1951 The Orlando Towers were originally built as part of a coal fired power station which took 20 years to build due to delays attributed to World War II. Decommissioned in 1998 the towers are today a defining landmark in Soweto where both concrete constructs stand 33 storeys tall, painted with images of township culture and welcome an abundance of local and international tourists to extreme sporting and cultural attractions.
- Ponte Tower – Johannesburg
Still the tallest residential apartment building in Africa, Ponte Tower was completed in 1957 standing 54 storeys and 173 meters high. A recognisable landmark against the infamous Johannesburg CBD skyline, Ponte Tower is a reinforced concrete tube complete with an open-air centre that was originally intended to allow more light into the cylindrical construct.
- Concrete Dolos - East London
Designed by a world famous South African harbour draughtsman Aubrey Kruger, the dolos sea buffer system of interlocking concrete is still used today to dissipate waves at rough breakwaters all around the world. Having based the design on the dubbeltjie thorn (Devils Thorn), original dolosse were cast into unreinforced geometric concrete designs weighing up to 20 tons per piece and placed in an interlocking matrix. Extremely effective in reducing the force of breakwater waves these designs are still used today some 50 years after conceptualisation.
- The Administration Buildings of UNISA – Pretoria
Known to many as "Die Skip" (the Ship) the Administration Building of the University of Pretoria UNISA makes for a striking backdrop when entering the capital city of Pretoria. The three-pointed star shaped building was completed in 1968 but later expanded to accommodate for more office space and features a magnificent concrete facade on the northwest wall adding texture and drama to the already commanding concrete construct.
Using a general purpose, normal strength cement such as Sephaku 32,5N or Sephaku 42,5N for the more serious builder, Sephaku Cement shares a step by step process on how to make DIY concrete bricks.
The most commonly used material in both the formal and informal construction industry; Portland Cement, offers the industry a durable and longer lasting building solution to any other material used in foundations, mortar, paving, roofing and flooring. Historically bricks were more commonly made from clay and clay derivatives, but making use of concrete bricks was a means to more cost effective masonry work, concrete bricks are now widely used in construction depending on the desired finish.
To follow, see how to make your own concrete bricks using Sephaku Cement with these simple steps.
- Step One: Preparing a Timber Casting Mould
With the help of a very simple wooden framework making your own concrete bricks is a walk in the park. With this step being as complicated as its going to get, using timber boards measured and cut to size together with a plywood backing reinforced by plastic sheeting to prevent leaking, nail together a wooden casting mould used to shape your concrete bricks into the appropriate dimensions.
While you can create a casting mould and bricks as large or small as you’d prefer, the following specifications are measured to make a mould that will result in a batch of eight cement bricks at a time, each measuring dimensions of
5.1cm wide, 22,9cm long and 8.9cm deep.
Erect your timber casting mould that will resemble that of a wooden ladder with equidistant steps and a plywood backing by measuring your timber with two sides of 1.2 m long and nine “steps” measuring 22.9 cm in length, spaced 5.1cm (4 inches) apart.
Using plastic sheeting as a backing, place your stepladder framework on the plywood backing which will help prevent the wet concrete from oozing through the cracks/joints once poured into the frame. It’s also recommended that you spray each mould with an aerosol lubricant or oil to assist in the removal of the bricks once cured.
- Step Two: Mixing Brick Cement
Making use of a normal strength cement such as Sephaku 32,5N or Sephaku 42,5N, begin by blending the cement together with a mixture of coarse and fine river sand aggregate measured at typical rations of cement to sand mixtures of 1:7, 1:8 or 1:9. Before mixing with water blend together the dry ingredients ensuring that the aggregate and cement is completely combined. Next create a well in the centre of the concrete blend and following the applicable water rations detailed on the bag of cement, very slowly add water to the mix to wet the mixture little by little as to not over wet the mixture. The mixture must be dry but not crumbly.(able to be easily squeezed into a ball)
- Step Three: Pouring and Curing Cement
Carefully fill your timber mould with wet concrete doing so more effectively using a spade instead of pouring it into the cast. Pay careful attention in making sure that the corners of each mould are filled or your bricks will not cure with perpendicular edges. Once each brick mould is filled gently tap all around the timber mould which will help to settle the concrete mixture into the corners. Using a straight edged trowel smooth out the surface of the concrete bricks levelling the surface as you go and then cover with a plastic sheet which will help to regulate the rate at which the brick cures during the first 24 hr period. The brick can be taken out of the mould very carefully and could be cured further after taking them out of the moulds by keeping them wet and covered with plastic sheeting. Once cured, The DIY brick can be used for your project.
As 3D printing, also known as additive manufacturing, continues to revolutionise a growing number of industries, Sephaku Cement explores how Concrete 3D printing is put to task in architecture and construction. Having already successfully created a number of prototypes and extremely technical products such as the intricate parts used in aerospace and aviation, as well as medical products including implants and artificial organs, 3D prints continues to pave the way as manufacturing and production marches into the 4th industrial revolution.
There are three common methods used in 3D printing technology, these include;
- Fused filament fabrication (FFF) or fused deposition modelling (FDM) which makes use of plastic materials that are heated and then pressed through a nozzle while following a pre-mapped design path
- Stereo-lithography (SLA) makes use of UV light to cure resin type materials one layer at a time
- Selective laser sintering (SLS) is more commonly used in industrial production and uses lasers to fuse powdered materials together one layer at a time.
From the design to the engineering and manufacturing, concrete 3D printing technology offers an efficient and cost effective alternative in the construction of a number of concrete applications. While initially limited to the use of molten plastic and metals, as 3D printing tech continues to advance, alternative materials are being employed including the likes of cement/concrete.
While concrete 3D printers are fairly significant in size especially for the construction industry, their mobility allows for basic concrete construction printing to occur almost anywhere and under various types of conditions.
Making use of a method similar to the Fused Filament Fabrication (FFF) or Fused Deposition Modelling (FDM) mentioned above, concrete 3D printing takes place using an automated and repetitive methodology that directs the print head through a sequence of rotations. While designs may still be a little basic and limited to more modest forms, concrete 3D printing can be extremely effective in the construction of high density, low cost housing in areas of high demand.
Basic Steps in the Concrete 3D Printing Process:
- As with any construction project, contractors begin by flattening the subgrade surfaces and placing sound foundations to work from.
- Once the foundations are in place, 3D printing technologists map the repetitive route that the 3D printer will follow using rail-like pathways that mimic the design. The 3D printer is then secured to the pathway rails and further guided by pillars for additional reinforcement.
- Once the design has been finalised and the printer’s route mapped out by the rails, a premixed concrete truck is connected to the 3D printer nozzle. The concrete mix used must be both fast curing as well as easy to pour, bonding to each layer as the concrete mix is pressed out of the printer. Making use of both superplasticizers as well as reinforcing fibres the ideal concrete mix can be achieved with the correct blend of chemicals and additives combined in the concrete
- The concrete 3D printer is now ready to begin following its repetitive path along the guiding rails depositing the exact amounts of concrete mix layer on layer.
With some concern that these concrete construction “bots” may eventually replace their human counterparts, concrete 3D technology is not without its shortfalls, although exciting technology is but only in its infancy, and will need much more development in future and will never fully replace the hand of construction contractors, workmen and architects.