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.

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.

Precautions To Reduce Health Risks In Concrete Work

Precautions To Reduce Health Risks In Concrete Work

As with many other materials, there are potential risks involved in handling or working with portland cement or mixes made using portland cement. Here Bryan Perrie, MD of The Concrete Institute, provides guidance on how to avoid the effects of unprotected exposure.

Water in concrete mix can cause alkali burns and safety measures should be observed

The composition of portland cement is such that when dry cement is exposed to water a chemical reaction called hydration takes place, releasing a very strongly alkaline (and caustic) fluid. This can cause alkali burns and safety measures should be observed. Appropriate precautions are advised to prevent tissue damage when handling fresh mixes containing water and portland cement.

Cement dust, dusts from handling aggregates and from cutting concrete are easily inhaled. Prolonged or regular exposure to these dusts should be avoided.

Portland cement is a complex combination of compounds that includes minute quantities of trace elements. Although South African cements typically contain less than two parts per million of Hexavalent Chrome (widely regarded as a safe level), it may serve as an aggravating factor in cases of exposure to alkaline fluids. There have been some reports of allergic dermatitis after exposure to these fluids.

When fresh concrete or its bleed water comes into contact with human skin, the alkalis react with the oils and fats in the skin as well as the proteins in the skin itself causing tissue damage. Other organic tissue (e.g. mucous membrane) can also be attacked by strong alkalies leading to burns that can sometimes be severe, and users should try to avoid all unnecessary contact with these fluids. Where such contact is unavoidable, suitable precautions should be taken.

Roughness and dryness of the hands after working with concrete is a typical consequence of loss of these oils and fats. More prolonged exposure could result in irritant dermatitis. It is possible that the effects of trace elements may aggravate the condition and lead to an allergic dermatitis. To safeguard against accidental exposure, appropriate protective equipment is strongly recommended.

Impermeable gauntlet type rubber gloves and high length rubber boots should be worn to prevent direct contact with skin. Trousers should overlap the boots rather than be tucked into them. Hydrophobic alkali-resistant barrier creams should be applied to hands and any areas of skin likely to be in contact with fresh concrete. Ordinary barrier creams are likely to be inadequate.

These precautions may be ineffective if the skin itself is not clean and free of concrete residue. Even a tiny trace of cement dust remaining in contact with wet skin will raise the pH significantly. For this reason, some authorities recommend the use of disposable gloves and discourage reusable gloves.

Regularly wash (at least daily) protective clothing and keep it clean and free of concrete and wash any areas that have been accidentally splashed with wet concrete as soon as possible with large quantities of clean water. Ensure that normal and protective clothing does not become soaked with wet concrete or concrete fluids as this could result in exposure over an extended period, resulting in tissue damage.

Cement is an abrasive fine powder, and when handled, some dust may become suspended in the air in the working area. Users should avoid inhaling cement dust as this may cause irritation of the nose and throat. Cement dust may also cause irritation of the eyes. This will occur because of the chemical reaction of the suspended dust with the moist mucous membranes. Airborne cement dust should be kept to a minimum to avoid these problems. Should this be impractical, then the use of goggles and dust masks is strongly recommended.

Many of the aggregates used in concrete have high silica contents. The fine silica dusts created when crushing or handling these aggregates could cause lung problems, and precautions should be observed to avoid breathing in such dusts.

Dust from demolishing or cutting hardened concrete may contain unhydrated cement and could cause respiratory problems as outlined above. In addition, if the coarse or fine aggregate used in making the concrete contains crystalline silica, then inhalation of these fine silica particles could expose workers to the risk of developing silicosis. A concerted effort should be made to avoid generating such dusts. If this is not possible, the use of suitable respiratory protective equipment is recommended.

Site workers should also not kneel on fresh concrete during placing, compacting and finishing operations. If kneeling is unavoidable, thick waterproof kneepads should be worn with a kneeling board to prevent the pads sinking into the fresh concrete. In severe cases of alkali burns, a medical practitioner should be consulted as soon as possible.

Cement industry to appeal for protection against imports

Cement industry to appeal for protection against imports

The Concrete Institute (TCI) will be lodging an appeal to the International Trade Administration Commission (ITAC) of SA to impose import tariffs on cement imports to protect producers from the mass importation of cheaper cements from countries such as China and Vietnam.

Bryan Perrie, MD of The Concrete Institute – which has as funding members the major cement producers, PPC, AfriSam, Lafarge, Sephaku and Natal Portland Cement – says the approach to the International Trade Administration Commission (ITAC) of SA will plead for the imposition of import tariffs and a possible ban on imports for a limited period.

The increase in imports of cement is affecting demand for locally produced cement to such an extent that SA manufacturers are considering mothballing plants, retrenching staff and putting expansion plans on hold. The effect of the cheap imports on SA cement producers is exacerbated by a slump of unprecedented proportions in the local construction sector with former giants in the industry already having shut or struggling for survival,” Perrie says.

Chinese and Vietnamese cement started pouring into South Africa after ITAC had – after an appeal from local cement producers – agreed that there was a need to protect the industry against the dumping of bagged Pakistani cement. ITAC then introduced heavy import duties of up to 77% for Pakistani cement which successfully cut dumping volumes. “However, imports from China have been rising steadily in 2016 and 2017 and last year Vietnam joined the fray, with more than a million tons of cement being imported into South Africa. These huge volumes are not required as the local cement industry already has annual spare capacity of around 5 million tons,” Perrie explains.

As Competition Commission rulings prohibit sharing company statistical information, The Concrete Institute has had to appoint an independent team of attorneys to confidentially collate sales, production and employment data of the various producers to include in the application to ITAC to try and curb cement imports.

After the cement industry had successfully lobbied for government protection against the dumping of Pakistani cement, the volumes of the imports from that country dropped from over 1 400 000 tons in 2014 to about 400 000 tons in 2016. “The construction industry is now in a far greater slump than during that period so need protection from imported cement even more,” Perrie adds.

Rob Rein, chairman of The Concrete Institute and Group Executive Sales and Marketing of PPC, says cement is a vital industry for the country and needs government protection at this critical survival stage in the construction sector. “The cement, concrete and affiliated industries employ thousands of South Africans whose jobs would be on the line if the government does not step in to protect local cement production,” Rein adds.

How to handle hot weather concreting

Summer’s blazing weather poses challenges when it comes to concrete placement and finishing

How to handle hot weather concreting

Summer’s high temperatures can cause problems with concrete placement and finishing so it is important to take precautions to minimise the potential adverse effects when placing concrete in hot weather conditions.

Bryan Perrie, MD of The Concrete Institute, offers some guidelines on minimising the effect of hot weather concrete:

The first option to be considered in exceptionally hot weather conditions is whether to postpone the placement of concrete. It is often better to wait than risk costly repairs, or even replacement of defective work and dissatisfied clients seeking compensation. If work is to proceed, proper planning from careful selection of materials to procedures for hot weather work is essential if risks are to be minimised.

Bryan Perrie, MD of The Concrete Institute

As stated, planning for hot weather conditions is essential because of the potential effects on fresh and recently placed concrete. For plastic concrete, these include increased water demand and risk of plastic shrinkage cracking, greater slump loss, faster setting and difficulty in controlling entrained air content. For hardened concrete, the risks include lower strength, reduced durability and increased drying shrinkage.

Because aggregates can be the hottest part of the mix, they have the greatest effect on the initial temperature of the freshly mixed concrete. However, the temperature of the aggregates is difficult to control. It may help to shade stockpiles from the sun and keep them wet with sprinklers and cold water but keeping aggregates cool is not an easy task.

The mix water is easiest to cool, particularly by adding crushed ice to it.

The temperature of the cement does not usually contribute much to the temperature of freshly mixed concrete because of its low specific heat and relatively small mass in the mix. Liquid nitrogen, injected into the concrete while mixing, may be useful. Latent thermal energy on vaporisation to gas can cool the concrete substantially without adverse effect on the treated concrete. This process is usually economical only on major projects involving construction of large concrete elements.

Adding some admixtures to the mix can help in hot weather conditions. Water reducers (plasticisers) will reduce the water content and aid workability. Set-retarders can provide more time to place and finish flatwork but beware: the retarders can make the surface look ready for finishing but the concrete below may still be plastic from the retarder. This can lead to cracking of the finished surface and affect the uniformity of the surface finish.

The water component of a concrete mix is the easiest to cool during hot weather concreting: simply add crushed ice

Selection of a particular cement type may also help. Slower hydration cements with lower rate of heat development can provide extra time for placing and finishing while reducing the concrete temperature and the risk of thermal cracking upon cooling of the concrete.

Painting silos and readymix trucks white or silver can also help reduce concrete temperatures.

In hot weather concreting, problems can arise when site personnel are not aware of the effect of weather conditions, or if weather conditions change during the placing and finishing of the concrete. The builders and sub-contractors should be ready for all possibilities and when hot weather conditions are likely consult the concrete supplier as early as possible. It will also be useful to have standby equipment and manpower for all stages and use the largest size and amount of coarse aggregate possible for the job.

In determining the slumps of the concrete, consider scheduling concreting for the cooler parts of the day, or even do night placement if possible. Plan the locations of construction joints ahead of time with hot weather contingencies in mind and consider spacing contraction joints at slightly smaller intervals than when concreting at lower temperatures. Even consider using sunshades or windbreaks and the use of high-pressure mist sprayers during placing of slabs on the ground or for pavement construction.

As concrete will set more rapidly and have a shorter finishing time in hot weather, perform all operations rapidly – but don’t finish slabs prematurely such as while bleed water is still on the surface.

It is essential that all surfaces be kept continuously moist by curing the concrete. As drying, even intermittently, can produce drying shrinkage and crazing type cracking on the concrete surface, curing should start immediately after the slab has been finished, and is particularly important during the first day after placement and in hot or windy conditions.

Curing methods include ponding with water, use of wet hessian or cotton mats, continuous spray mist, covering with plastic sheeting or spraying on curing compounds. Adequate curing of the concrete must still be provided once final finishing has been completed.

Students: Prepare now for the 2021 Advanced Concrete Technology course

Students: Prepare now for the 2021 Advanced Concrete Technology course

The Zeitz MOCAA Museum of Contemporary Art Africa in Cape Town – the epitome of applied concrete technology Photos: Gareth Griffiths

South African cement and concrete industry professionals should be preparing now to be accepted as 2021 students for the SCT50 Advanced Concrete Technology (ACT) course, a certificate globally accepted as the pinnacle in concrete technology.

This is the advice of John Roxburgh, lecturer at The Concrete Institute’s School of Concrete Technology.

The School of Concrete Technology (SCT) has confirmed that it will again offer tuition for the SCT50 Advanced Concrete Technology (ACT) course in January and February 2021. The School offers this highly prestigious course every two years and enrolment for the 2019 presentation has already closed.

The Advanced Concrete Technology examinations and diploma – presented by the School on behalf of the Institute of Concrete Technology in London – is a challenging course, with examinations covering over 60 topics in concrete technology. So, extensive and intensive preparation is needed simply to start the studies.

Advance preparation

The School of Concrete Technology therefore recommends that in the two year lead-up to the 2021 ACT course, prospective students should enrol for and complete three courses offered by the School: SCT30 Concrete Technology, followed by two important concrete technology and construction courses: SCT41 General Principles and SCT42 Practical Applications.”

Roxburgh says the SCT30 course covers important concrete technology concepts to prepare students for SCT41 and SCT42. “These are essential firm foundations from which attempts at the ACT diploma should be launched. Both provide sound general introduction to most of the topics covered in the ACT. In fact, a prerequisite for being accepted for the SCT50 Advanced Concrete Technology course is a pass in both the SCT41 and SCT42 courses.”

He says it therefore makes sense to use the two years ahead to become fully prepared technologically before the School starts its 2021 Advanced Concrete Technology training.

The School’s broader 2019 Education Programme is now available and contains full details about the above and all other courses to be presented in Midrand, Cape Town and Durban next year. alloescort.ch

For full details, phone 011 315 0300 or email sct@theconcreteinstitute.org.za or visit www.theconcreteinstitute.org.za

Concrete versatility and sustainability important for infrastructural development

Concrete versatility and sustainability important for infrastructural development

Bryan Perrie, managing director of The Concrete Institute

The versatility of concrete boosts the building material’s sustainable merits and should be a decisive factor when maximum quality and longevity are aimed for in infrastructural projects, says Bryan Perrie, managing director of The Concrete Institute (TCI).

Perrie says the user or designer can basically decide what type of concrete he or she needs. “Concrete can be designed and proportioned to meet an extremely wide range of specific requirements including consistencies, flows, setting times, and hardened properties. The product is flexible enough to produce varying strengths at early or late stages, different types of strengths in general, pre-determined densities, as well as the required levels of abrasion resistance and shrinkage.”

When building with concrete, some of the many flexibility benefits include:

  • Concrete can be produced on the building site using a wide variety of transport and placing mechanisms;
  • It can be transported from batch plants to the construction site via a myriad of means ranging from simple wheelbarrows, to heavy engineering vehicles and equipment such as dumpers, trucks, conveyors, cranes and pumps;
  • Concrete can be placed by cranes, pumps, trunks, spraying equipment, and tremies (large metal hoppers and pipes used to place freshly mixed concrete underwater); and
  • Self-compacting concrete (SCC) offers additional flexibility in the placing of concrete and the achievement of excellent off-shutter finishes.

    Versatile concrete in its pre-cast form is used for storm water drainage, water and sewage reticulation pipes

Concrete has the advantage over other materials in that concrete elements such as walls, columns, beams, trusses, and slabs can be constructed in situ as part of the structure being erected, or pre-cast on site on the ground and lifted into their final position via the tilt up and stack casting methods. As a hybrid of pre-cast and in situ concrete, concrete can also be pre-cast kilometres away in a pre-cast yard and transported to site and placed into position there.

An additional benefit is that all of the above options can be combined on one project. This may mean that some elements are constructed in situ, while others may be pre-cast on site and still other pre-cast off-site,” Perrie adds.

Dealing with the versatility of pre-cast concrete, he says this economical construction product is derived by casting concrete into a reusable mould or form which is then cured in a controlled environment, transported to the construction site to be lifted into place as opposed to standard concrete which is poured into site-specific forms and cured on site.

By producing pre-cast concrete in a controlled environment – the so-called ‘pre-cast yard’ – it is possible to monitor and control all stages of production, including ensuring that adequate curing is carried out to ensure that the final products fully comply with strength requirements.”

Pre-cast yards may be established, operational factories or can be created on site. The pre-cast concrete is generally cast at ground level which helps with safety and productivity throughout a project. “As stated, there is greater control of the quality of materials and workmanship in a pre-cast yard than when concrete is cast in situ. Pre-cast yard production tends to lead to increased better durability and when the products and structure last longer, the end-result is cost saving in maintenance, materials and energy – not to mention eliminating inconvenience. The forms used in a pre-cast plant may be reused hundreds to thousands of times before they have to be replaced which ensures that the cost of formwork per unit is lower than for in situ construction.”

Concrete can be pre-cast on site on the ground and lifted into their final position via the tilt up and stack casting methods

Furthermore, if the structure has been appropriately designed, pre-cast products can be removed and reused after the structure has reached the end of its life and is to be replaced.

Perrie says there are many forms of pre-cast concrete products, including:

  • Pre-cast architectural panels used to clad all or part of a building;
  • Storm water drainage, water and sewage reticulation pipes, culverts, manholes, sumps and tunnels;
  • Pre-cast building components used architecturally as cladding, trimmings, accessories and curtain walls;
  • Pre-cast concrete’s structural applications include bricks, blocks, foundations, beams, floors, walls and other similar components; and
  • Pre-cast concrete products are also used in the building, safety and site protection of various transportation systems in the form of culverts, bridge beams and segments, railway sleepers, sound walls or barriers, safety barriers and kerbs.

The increased control of pre-cast concrete in the production phase ensures fewer reject products and consequent saving of raw materials, as well as speeding up construction on site. Well-situated, highly sophisticated pre-cast yards produce pre-cast products to very high tolerances resulting in significant time-savings on site. Examples of this were the pre-cast plants that manufactured the thousands of pre-cast concrete tunnel and bridge segments of the Gautrain infrastructure.”

Perrie adds: “The social contribution of concrete to civilisation cannot be overestimated. It is the second most used resource in the world after water and contributes significantly to human standard of living including the houses we live in, the schools and universities we attend, the offices we work in, the infrastructure of water reticulation and sewers, the dams that hold our water, and the roads that fulfil the needs of mankind globally.”

Concrete Conference unites the industry

AfriSam, main sponsor of The Concrete Conference, staged an impressive exhibit

A united industry is a stronger one that is better able to represent its members through periods of high growth while maintaining its solid structure in times of adversity.

This was the overriding message of The Concrete Conference 2018, which was held in Boksburg recently as the first of its kind to fully involve representative organisations of the concrete and cement industries. The events therefore gave local and international speakers the ability to address a combined audience of members of The Concrete Institute (TCI), Concrete Society of Southern Africa (CSSA), Concrete Manufacturers Association (CMA), Southern Africa Readymix Association (SARMA) and the Association of Cementitious Material Producers (ACMP).

Richard Tomes, Executive: Sales and Marketing, AfriSam opened The Concrete Conference proceedings

In opening the conference, Richard Tomes of AfriSam, the main sponsor, said that a unified industry is essential for the industry to make headway. “The entire construction industry needs to plan for the future and map a way forward that involves all professionals’ bodies within the industry. It is therefore so important that the concrete industry finds its unified voice to help shape construction in future and to address challenges that face this end of the sector.

Strong voice

If we don’t get our act together soon our infrastructure will collapse, and it has already started at some levels within our municipalities and state-owned enterprises. But, in order to make positive changes we need everyone to be on board. We need to support industry associations such as these here today and obtain funding to keep them going.

The Concrete Conference 2018 in Boksburg was the first of its kind to fully involve representative organisations of the concrete and cement industries

For example, AfriSam is the only cement producer that is a member of SARMA right now and, in my opinion, it is just not right that it funds this association by itself. It is time other role players and suppliers to these industries start to contribute. If not, we will also eventually be forced to withdraw our funding and the industry’s own association may be faced with closure as a result. It is time for other role players to step up and support all our concrete professional bodies,” said Tomes.

SARMA’s Johan van Wyk, agreed adding that associations have to move with the times and become more relevant with added benefits for members and a louder voice within policy and economic frameworks. By combining the strengths of the industry bodies, it will be possible to provide more value for members. “What excites us unites us!”

Long road

Adding to the discussion, TCI’s Bryan Perrie, continued saying that the pooled resources of the five associations will make for a robust organisation that will have different agendas for different disciplines, but the same end goal to make concrete the building material of choice.

At present the individual industry bodies draw funding from the same major stakeholders and these cannot continue to fund them as they had in the past. Whereas a single coordinated body is more agile and eliminates duplicated costs, it can still continue to provide the key activities that had previously been provided and more.”

In closing he said that a lot of work still needs to be done to unify the concrete associations and that consultations with members and business studies were still being conducted to work out the finer details.