Tag Archives: Concrete


Concor Buildings is synonymous with delivering fast track projects to the desired quality, on time and most importantly within budget.

Martin Muller, contracts manager at Concor Buildings, ascribes this characteristic as one of the reasons why the company secured the contract to construct the new student housing accommodation in Streatley Avenue, Auckland Park.

Being developed by Century Property Developments, The Campus, when completed at the end of 2018, will provide accommodation for 800 students predominantly from Wits and UJ. This will mitigate some of the shortages being experienced with student accommodation close to the tertiary education institutions.

Construction work started in January this year and practical completion is targeted for November 2018. This will allow the finishing trades access to ready the apartments for occupation in early 2019.

Designed with an industrial look and feel, The Campus is a four and six storey building with two basement levels. The multi-storey structure will house several communal areas including study rooms, computer labs, conference rooms, a games room and a gym facility.

Significantly, The Campus will be pursuing an EDGE Sustainability Certificate through the Green Building Council of South Africa. This international rating system looks at three key areas being energy, water and materials.

Describing the construction methodologies being used, Muller says that an in-situ cast concrete base structure was cast up to the ground floor transfer slab and that everything above this level is a combination of load bearing brickwork with precast slab elements and various steel finishes.

The sections above the transfer slab vary from four storey to six storey structures with eight apartment blocks in total. The design of the complex features a central core area which will house the access lifts, a pool and gym, a canteen and other services. The basement area will accommodate both parking and storage facilities for the students. All apartments will be fully furnished making it an easy rental for students.

Once the load bearing brickwork is completed, the precast slab elements which include floor slabs and staircases will follow.

An interesting challenge for the contractor is that the construction site is taking place within a residential area which is rich in heritage and care has to be taken at all times to adhere to the local bylaws and residents’ requests.

Adding to this factor, there are additional logistical challenges as the site itself is spread over 235 metres with an extremely narrow roadway making access to site challenging. To mitigate materials handling activities, Concor Buildings erected two tower cranes which were strategically placed to service the entire construction site.

“Fast track projects are challenging at the best of times but with these logistical factors at play we have had to pay even more attention to detail in planning,” Muller says. “It is critical that materials are delivered at the correct time to the correct location as there is no space for the stockpiling of materials on site. This means delivery of all bulk materials must dovetail accurately with the construction programme.”

He explains that during the detailed planning process, the team used resource linking to the various activities to ensure sufficient resources are available when and where needed. In this manner, the company has been able to mitigate most issues.

“It is this level of planning and the control of information flow that makes a fast track project a success, and it also calls for close communication between the client, the professional team, us and the many sub-contractors that are on site,” Muller says.

Majority of the finishing trades will be done by selected sub-contractors, and Muller says that the focus here has been on ensuring overall quality while controlling the cost. The polished concrete floor and ceilings will have an off-shutter finish from the slab elements above. The walls will be mostly whitewashed, and the furniture and finishes will be modular with a modern industrial look.

Safety, as always, is a non-negotiable on Concor Buildings’ projects but constructing within a residential area has required an even more focussed approach. Maintaining absolute safety on the roadway is vital and additional personnel have been put in place to ensure this.

Another important factor is working at height, especially on a project which is fast track in nature. Skilled tower crane operators are essential and Muller says that they will play an important role when it comes to lifting and positioning the precast elements.

Concor Buildings’ Visible Felt Leadership strategy can be seen on site, and management often takes part in the daily safety task instructions briefings showing solid leadership and commitment to the company’s safety objectives.

“We are synonymous with delivering fast track projects on time, within budget and to the required specifications, and to be able to do this is all about team work and understanding what is required of each individual. We have a cohesive team and ongoing communication is vital. The team includes a lot of strong young professionals who bring energy to the project,” Muller concludes.


Extensive realignment and rebuilding of the R72 route from Port Alfred to the Fish River by Concor Infrastructure will make this busy route safer and more suited to heavier traffic.

Concor Infrastructure, previously known as Murray & Roberts Infrastructure, is part of Concor Construction which was recently acquired by a consortium led by Southern Palace Group.

According to Concor Infrastructure project manager Bennie Hook, the road has become much busier in recent years with vehicle numbers climbing to about 5,500 a day. Up to 40% of this traffic is commercial or heavy transport trucks.

The Concor Infrastructure contract awarded by the South African National Roads Agency SOC Limited (SANRAL) covers the 27.5 km between Port Alfred and the Fish River Bridge, and includes the addition of alternate passing lanes in each direction. The project is expected to be completed by October 2018.

Hook says the work begins in Port Alfred, and will improve the urban road through the town, and also add shoulders, kerbs, drains and even pedestrian walkways in places. The bulk of the work is taking place on the rural road with rebuilding, broadening and realigning to make it stronger, safer and longer lasting.

The roadworks include the building of a completely new roadway alongside the existing route.

SANRAL required that the project be implemented in such a way as to avoid the ‘stop-and-go’ traffic management method as far as possible, due to the traffic disruption this causes as well as the associated safety hazards. The project roll-out first proceeded on the ‘left-hand side’ (facing west towards the Fish River), and will move over to the other side only when traffic can flow on the new lanes.

The Fish River Bridge – the easterly limit of Concor’s R72-route project – will receive minor refurbishments and a precast concrete rail to replace the missing steel railings.

Concor Infrastructure site agent, Michael Stiebel says an important improvement on the new road will be better ‘line-of-sight’ for drivers.

“The existing road was constructed essentially along the lie of the land,” says Stiebel, “The realignment gives motorists a much better view of the road’s contours and bends, as well as on-coming traffic at a distance.”

Some of the vertical realignments have been up to three metres in height. The volume of crushed stone comes mainly from a new quarry at Shaw Park, which has produced about 1,5 million tonnes of crushed stone including aggregate, rock fill, drain stone and slurry dust.

Ensuring a better rideability of the road is another priority that has influenced the execution of this project, with the help of some high-tech equipment, says Hook.

“Our graders are equipped with Trimble grade control systems to help achieve these higher rideability levels,” says Hook. “We use the model that employs global positioning system (GPS) technology, and have now also employed an upgraded model that works from a robotic total station.”

The realigned new road will comprise a 300 mm thick selected sub-grade layer and a 300 mm thick crushed G4 sub-base layer, stabilised with 2,5-3% of AfriSam 32.5 Roadstab bagged cement. On top of that comes a 150 mm base layer, and a final 20 mm Cape Seal on the rural road; the section through Port Alfred will receive an asphalt wearing course after widening and strengthening.


Botes & Kennedy Manyano offered Petra Diamonds a practical workable solution for the rehabilitation of three concrete silos at its Finsch Diamond Mine in the Northern Cape.

The design and construct project was aimed at restoring the structural integrity of the silos while addressing issues such as concrete and liner wear inside the structures.

Mantie du Toit, contracts manager at Botes & Kennedy Manyano, says that most importantly the solution provided an option whereby the concrete repair work would be done by taking one silo out of production at a time and recommissioning it before work would start on the next silo causing as little impact on the plant operation as possible.

Du Toit says that prior to the concrete repair work and construction taking place, Botes & Kennedy Manyano through the help of contracted consultants, was also responsible for the stability analysis of the structures. This formed part of the risk analysis phase of the project.

Construction work on this project started April 2016, and involved surface concrete repair work on the external faces of the three silos as well as on the internal faces. The spalled surfaces were repaired using various techniques depending on the severity of the damage.

Each silo has an external diameter (OD) of 13,4 metres and an internal diameter (ID) of 12,8 metres. The total height of the silo which includes a conical section at the bottom stands at 22,8 metres; the cylindrical storage section is 13 metres.

Access into the silos is restricted to entry from the top of the structure and the bottom outlet of the silo, and at the time of starting the repair work, each silo was filled to the top with kimberlite ore. The ore levels were discharged in a controlled way to a predetermine level in the silo to facilitate the concrete repair work. Use was made of a working platform lowered from the top entry giving access to the different levels going down at 2 metre increments. This was done by emptying the silos using the bottom draw point.

Outside access was facilitated through the use of scaffolding that was erected to the required height.

“During the project each of the silos was taken offline for a limited period of time, and this meant that the necessary resources had to be available to ensure optimum productivity was achieved, while still operating safely within the operational plant,” Du Toit says.

Mitigating the challenges faced by working at height required careful planning and stringent safety systems were implemented. All personnel received specific working at height training to ensure that all were competent and understood the working at height procedures. Du Toit says that the project safety statistics underpin the commitment show by the team.

Concrete repair generates a large amount of dust, and this was further aggravated by the work being done inside a silo. To mitigate this, ventilation ducting was installed to extract the dust and fumes, facilitating a much safer working environment for the personnel.

In addition to the concrete repair work on the inside of the silos, Botes & Kennedy Manyano was also tasked with increasing the wearability of these internal surfaces. This was achieved using a special epoxy product that will increase the abrasion resistance of the concrete surface

The scope of work also included the rehabilitation of the bottom cone section of each silo. Prior to this work beginning, custom carbon steel liner plates were manufactured and later installed to perform the function of protecting the concrete surfaces at the cone section. These also acted as an external shutter face to facilitate the casting of a concrete lining to strengthen the cone section of the silo. As the installation of the steel liner progressed upwards, the casting of the new 300 mm concrete lining followed the installation operation.

This was a labour intensive operation and to facilitate greater productivity in areas not subjected to interfacing with the mine, a bagged prepacked concrete mix was decided on. The bags were raised to the deck located at the top of the silo, where batching of the concrete was done in a portable concrete mixer. The concrete was then lowered from the deck level through a centre access, using a working platform with filled buckets of concrete placed on it, lowering it to the level of cast. The concrete was hand placed using the buckets and then densified. A retarder was used to lengthen the window of cast to prevent dry joints.

Attention to detail during planning as well as execution was essential to ensure that the safety of personnel was at not put at risk during this operation, and that the quality of the final product was not compromised. Some 64 m3 of concrete was used for the cone section of each silo.

A circular concrete beam was cast on the outside circumference of each silo to increase the strength and stability of the storage structure. This was done above the cone section of the silo.

Once all the concrete repair work had been completed, post tensioning was done on the outside of the structures. In total 58 strands, spaced vertically at predetermined intervals, were stressed. And this could only be done once all the repair work, both internal and external, had been completed.

Du Toit says that generally, concrete repair methods are application-specific and the solutions recommended and applied depend on the individual requirements. “We have the necessary technical expertise and experience to assess the best course of action in each circumstance and to develop a sustainable solution such as the one applied at Finsch to rectify any issues and maximise the useful life of the structure,” he concludes.

A top view from the roof inlet showing the liner plate stripping in progress in the cone section.