With the recent earthquake in Kaikoura and the damage to buildings in Wellington there was a lot of media debate around the appropriateness of our standards. Thankfully with the improvements since the Christchurch earthquake NZS3101, our main concrete design code, is as current as it could possibly be. Earthquakes don’t read codes and the effects in Wellington from the recent quake were beyond the current code earthquake. These quakes are giving us the opportunity to see how the code design works in real earthquakes and update where appropriate.
So NZS3101 is current but this cannot be said for many of our other codes in the concrete space. We have standards that are very old. NZS3114 on the finishes to concrete is from 1987. We have recently seen with the issues around mesh what impact poor out of date standards can cause. The problem being that any changes have to be funded by industry which generally means they are not updated. The Government stepped out of standards and this action is coming back to haunt us with a raft of standards in need of updating.
We have all seen the slow degradation of infrastructure caused by lack of investment over many years. Particularly in the US this is a major headache. This is what we have with our standards. Its effectively a serious train crash at very slow speed. You don’t notice for years until you wake up one day to see litigation through the industry and fights over quality.
Times are good in the construction industry as they are in the Government coffers and we must use this boom to gain the funding to ensure that our standards are brought up to date. From a company involved in concrete finish and tolerances we’d suggest a good start would be with NZS3114:1987.
Beware the season of cracked slabs is upon us. For those pouring externally you are at risk during the coming months. Windy conditions with low humidity and considerable temperature changes overnight bring with it the risk of cracking prior to crack control measures being effective. In fact most cracking is not due to loading or design issues it is due to detailing of restraint or to these early environmental effects on the construction. Too often concrete contractors have not put the relevant protections in place and rely on the old excuse of “all concrete cracks”. Without question concrete shrinks but it needn’t randomly crack. To find out more read the article: Random-Cracking in Spring
A common detail by engineers is to show every second bar of secondary reinforcement (generally top mesh) cut at sawcut joints. Conslabs view is that this is just plain wrong.
The engineer wants to ensure the crack occurs at the swat joint and not as a random crack but in doing so they are reducing the load carrying capacity of the slab and setting the slab up for ongoing maintenance as they increase the likelihood of a dominant joint. It highlights a fundamental misunderstanding of the reason for having secondary mesh in the slab in the first place.
To help construction companies and engineers avoid this pitfall we’ve written a small article outlining why we have mesh in the slab and what is going on at a sawcut joint.
To find out more read the article: The-Practice-of-Cutting-Reinforcing-at-Sawcuts
The tolerances called up in table 5.2 NZS3109 “Tolerances for in-situ construction” are not achievable on elevated concrete floors. The relationship to datum is specified as +/-10mm. With deflection and ongoing creep this is not going to be acheived. Then for flatness it references NZS3114 requirements. 5mm in 3m is also not going to be achieved 100% of occasions and if you have thin tiles such that the specification is 3mm over 3m then you are in trouble if the client measures the tolerances. Don’t expose your firm to the risk.
What we recommend is that for the relationship to datum you tag to +/-20mm from datum. All measurements to be taken within 72 hours and if propped the measurements must be taken prior to removal of propping.
For the flatness criteria we recommend using the British standard SR2 although the UK Concrete Society guide on elevated floors notes that SR2 will not be achievable everywhere. Thus we recommend changing this to 90% of readings meeting SR2. SR2 is 5mm measured over 2m.
Be up front with the engineer so that he is involved in the conversation early. Don’t wait until post construction when you may discover you have a very expensive bill for levelling screed.
We are delighted to inform you that we have agreed a business merger between Conslab Ltd and Euro Corporation Ltd.
As of January 01, 2016, Conslab and Euro Corporation have been merged and Conslab will operate as a separate division of Euro Corporation.
Our key managers Tim Walker, Andrew Dallas, Brian Mooney and Glyn Sutton, will all stay on in key management positions in the merged business.
Tim will continue as General Manager for the Conslab business on a day to day basis reporting to the Managing Director of Euro Corp – Randal McKenzie. Brian will continue in his current role of Operations Manager for Conslab reporting to Tim. Glyn will lead the growth of the Conslab operations in Auckland. Jeff Palmer has been appointed as South Island Manager for Conslab taking over from Glyn. Andrew will become Technical & Business Development Manager for the wider Euro business.
We are entering a very exciting period for the New Zealand construction industry. Strategically this is an important move for both businesses during a period of rapid growth. Euro Corporation have a strong track record of innovation and consequently have been one of our key suppliers of mesh and reinforcing bar. They have extensive capability in “full service” supply, cut, bend and install of reinforcing and have invested heavily in capacity. This capability and experience will form an integral part of our growing business. Euro Corporation will supply Conslab cut, bend and installation services as well as stock reinforcing and mesh products making us even more competitive.
This merger further demonstrates Conslab’s commitment to being the leading concrete floor provider in New Zealand and providing our clients the best value for their projects, delivered on time and hassle free. We believe in this merger as Conslab and Euro both share the same goal of working to transform the productivity of NZ’s construction sector and ultimately improve NZ’s infrastructure.
Conslab submitted the construction of the floors for the JPL Distribution Centre into this years NZ Concrete Society Awards and took out a commendation in the Technology Awards. Tim Walker (left) Conslab GM and Andrew Dallas (centre) the technical director are seen here receiving the award from the Concrete Society President Jeff Mathews.
To read in detail as to how Conslab undertook a world first hybrid approach to constructing VNA floors follow the link to the paper Tim Walker presented to the conference. Tims paper also received a commendation from the judges who award the Sandy Cormack prize for the best paper at the conference.
Acid staining at the entrance to a battery charging area.
Acid and concrete floors just don’t go. The acid eats into the paste of the concrete floor gradually degrading the surface. Where we see a lot of this is in the battery charging rooms for warehouses. We get told that the new forklifts don’t have this issue but before long an older forklift is being used and we are called in to repair the concrete floor surface. It gets worse in that the acid is tracked out into the warehouse causing degradation of the surface out there. This surface dusts and causes further problems. What is common is an unsightly brown staining associated with the acid.
It makes sense when building a new warehouse to epoxy coat the concrete floor in the battery charging area prior to bring in the forklifts. Doing it later once you have degraded the top of the floor just adds to the cost. The concrete has to be ground down to a solid base before the epoxy coating can be applied to ensure it has a good bond. Apply an epoxy coating early when the building is new to ensure the concrete floor remains in top condition. Conslab have a range of epoxy coatings for concrete floors that can provide ongoing protection against acid attack as well as being able to provide a non slip surface if required.
Epoxy coating protects and enhances the concrete floor
Thick concrete raft slabs generate enormous heat from the hydration of the cement. Slabs such as this will be getting up to 60-70 degrees internally and will take weeks to cool down. Consideration has to be given to using as low a cement content as possible. Use 56 days strengths or use a fly ash or GGBFS mixes. Use mixes with large aggregates, 40mm maximum size for instance, if possible and practical The pours take planning in terms of the logistics of getting the concrete in there with pre pour meetings between all the parties involved to ensure you have backup at plants and for the pumps, can you reach all the site, where do you park the trucks waiting to get onto the pumps? Have you got the staff necessary for both ensuring trucks don’t run out of driver hours and the staff on site won’t get too tired. Following the pour you need to monitor the temperatures at the surface and in the middle to avoid a significant temperature differential (20 degrees)from the inside to the outside. To avoid that difference requires insulation and you can play the temperature, removing the insulation to help the slab cool and covering again once the difference gets up towards 20 degrees. Conslab’s manager in Christchurch Glyn Sutton is an expert in the practicalities of these large pours.
View our largest concrete pour to date being the 1850m3 pour for Leighs Construction (Video courtesy of Leighs) in Christchurch on the ANZ building, Firth supplying the concrete with JFC Pumps pumping. Click on the link below.
ANZ Centre concrete 3 720
In October in Rotorua at the NZ Concrete Industries Conference in Rotorua Tim Walker is presenting a paper on the concrete floor for the JPL Distribution Centre. We have included his full paper here.
The JPL distribution centre in East Tamaki incorporates a 25,000 m2 post-tensioned ground floor, designed to facilitate the use of cutting edge logistics technology such as 16 m high Very Narrow Aisle Racking. The project required balancing the owner’s requirement for an extremely durable and low maintenance surface with the need to optimize the floor flatness to support the day to day operation of the most modern material handling equipment in the world. Very Narrow Aisle facilities are becoming much more prevalent in New Zealand and the JPL distribution centre offers an excellent case study for examining some of the design and construction challenges these buildings pose, while also reviewing the marrying of New Zealand construction techniques with international best practice and recent global innovations in industrial flooring. For the full paper follow the link below.
World Leading Concrete Flooring
We were pleased to receive this glowing testimonial From Macrennie Commercial Construction recently regarding Conslab’s Health and Safety knowledge and procedures. H&S is of the utmost importance to our organisation and it’s fantastic to have this recognised by a long term partner.
“We have worked with Conslab for nearly 15 years, reviewing their Site Specific Safety Plans, auditing their procedures and observing their working methods.
When we review a company’s safety documentation and safety behavior we look for certain elements :-
1. Have they clearly stated the task they will undertake?
2. Have they identified the hazards associated with each task and assigned controls?
3. Do they have competent staff to undertake this work and ensure all controls are activated?
In all cases we have found Conslab fulfilled the above requirements in a professional manner.
In all the years on large or small sites we have never had to:-
1. Chase them for paperwork.
2. Issue them with a nonconformance notice.
3. Issue any warnings to any of their staff.
One of the main traits we have noticed with Conslab is that every worker from tradesman, operators ,finishers, supervisory staff is that everyone understands their safety methodologies and requirements.
In our H & S and management meetings – it has been confirmed on many occasions that we have rated them our number one (1) contractor.
Contractors like Conslab make our job that much easier and contributes to Macrennie maintaining an incredible H & S record.”
Macrennie Commercial Construction Ltd