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Supplying aggregate for Hi-Lab

A Huntly quarry owned by Gleeson and Cox is producing aggregate to meet the special requirements of the Hi-Lab road paving being used on sections of the Waikato Expressway. Richard Silcock chats with quarry manager, Shawn McLean.

 A quarry near Huntly, now owned by Gleeson and Cox, has been supplying aggregate for nearly 100 years and, according to quarry manager Shawn McLean, there’s still plenty of rock to be extracted from the site with geotechnical investigations indicating the site has an expected life-span of at least another century.

“Almost a third of our aggregate output is being transported to the various Waikato Expressway sites where the contractors are laying Hi-Lab paving,” says Shawn. (1)

“In addition, we supply all sizes of greywacke aggregate, in any quantities and to most specifications, including rip-rock and rock for gabion walls. Our stockpile range is made up of some 25 products.

“We deliver to site using our own truck and trailer units, and also allow customers to load from our stockpile site. Access to the quarry is easy, as we are just over the river from SH1, and only a few kilometres south of Huntly.”

The quarry was originally owned by the Raglan County Council and mined by the Roose Shipping Company which later purchased it. (2)

In 1981 it was acquired by Stevenson Quarries which, due to the upsurge in road works in the Waikato area at the time, was extracting some 1200 metres of rock per day. The quarry was first profiled in Q&M in the June 2014 issue.

In 1999, new equipment was bought to keep up with demand, increasing the output to 2500 metres of aggregate a day.

“Gleesons took over the quarry in 2018 and it is, again, going through a period of growth as the demand for aggregate in the area has sky-rocketed due to the construction of the 102.2-kilometre Waikato Expressway and other large road projects,” says Shawn.

The land area for the Gleeson Quarry covers an area of over 1000 acres, of which 38 acres is currently being open pit mined.

Shawn has worked on the site since 2005 when it was owned by Stevensons and knows the quarry like the back of his hand. He took over as manager from Pat Wallbank who was killed in a local road accident. In 2016 Shaun was also a recipient of e Q&M Editor’s Choice Award recognising young industry leaders.

“I began my career here as a dump truck driver aged 27 and built up my experience under the watchful eye of Pat Wallbank. I gained my A-Grade Quarry Managers Certificate after studying and putting in some long hours.

“I have a team of 26 reporting to me. We’ve got a good bunch of guys and four women. They all love their job and share a wealth of experience between them. Like me, some have been working here for over 15 years.”

In addition to managing the Huntly quarry Shawn was recently appointed regional quarry manager for the Waikato region, with responsibility for all of Gleeson and Cox’s quarrying activity.

“At Huntly we are running a combination of plant and machinery. We have five CAT and Hitachi excavators, five CAT dump trucks, a number of Volvo loaders, several CAT bulldozers and a grader.

“Our crushing plant consists of two static impact crushers, a Rocktec and a Svedala, each processing 250-300 tonnes of rock per hour. We also have four mobile units made up of several Metsos and a Barmac vertical shaft crusher for product used in concrete, asphalt and road construction applications, along with a Metso scalping unit.

“Altogether we are producing around 500 tonnes of crushed aggregate per hour.

“The new Rocktec pug mill machine [continuous mixing plant] has proven to be a most valuable asset as we are able to provide a wide range of modified aggregates to suit varied specifications.”

Shawn says for the Hi-Lab production the quarry is crushing to a specified 65-millimetre and 40-millimetre diametre using a modified jaw and cone Barmac crusher with four screens.

“The size of this aggregate is super critical, so we monitor and carry out regular quality controls.”

Hi-Lab is a relatively new form of ‘concrete’ paving that was developed in South Africa and tested here by the Transport Agency for use on our motorways.

It requires specially graded aggregate and the process of laying it involves first grading and rolling a layer of sand over the compacted earth foundation and then applying 65-millimetre aggregate blended and bound with fine gravel.

A further layer of 40-millimetre rock and fine gravel is then added over the top, cement and water added and then mechanically hoed to mix it together. Vibrating rollers then compact and roll it to provide a smooth surface.

This is then sprayed with bitumen and sealed with a fine stone chip before being asphalted. The whole process is both aggregate size and time critical as the setting concrete forms the basis of the base layers necessitating the need to complete each section of highway within a tight timeframe. 

“For the Huntly section of the Waikato Expressway, some 300,000 tonnes of aggregate was required in total and for the Hamilton bypass section, which is presently under construction. It is expected even more will be required,” says Shawn.

“We, together with the local Fulton Hogan owned quarry, are supplying most of this material.

“Fletcher, who are constructing the expressway now have their own on-site pugmill so most of our quarried rock is dispatched directly to them, however it is absolutely vital that we supply the aggregate to specification for this project as the Hi-Lab construction method requires the components to be very precise.”

Footnotes

The Hamilton section of the Waikato Expressway is being constructed by City Edge Alliance comprising Fletcher Infrastructure, Higgins Contractors, Coffey Geotech and Beca (as construction design consultants). Hick Brothers Infrastructure is providing the bulk of the earthworks and WSP is acting as principal advisor (refer Contractor July 2020).

Caesar Roose was the owner and operator of this shipping company. He was also a flax and timber miller and later a community leader. He ran a shipping service, based at Mercer, between Port Waikato and Cambridge (Circa 1915) and in 1922 purchased the Huntly mine. He campaigned for the dredging of the Waikato River and constructing a canal between the river and Waiuku.

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