Oral Presentation of the Past

Without the past what would we become?  

Whilst searching the archives of Aran’s technical papers this week we located a transportation planning study for Brisbane City, published in 1965. The insights into population growth and infrastructure development demands were surprisingly accurate.

Planned projects, costed to pounds and pence, with grade and alignment designs, many of which have been constructed in various forms. Some are still needed. Some abandoned for the preservation of urban lifestyle. It was fascinating to reflect on Aran’s contribution to the development of Brisbane’s road network for over 40 years.  Click the pic for the 2004 Program.

Click Here for the Full Oral History Report.

This interview is an excerpt from a Report which was commissioned by the New South Wales State Road Authority (RTA Roads and Traffic Authority) in Australia. This report was commissioned in 1997 to investigate various topics, based on 28 hours of digitally recorded interviews from 23 participants. Trevor Dunstan, Aran Founder, was interviewed to talk about the introduction of mobile pugmills.

Today, Aran’s legacy has been paved around the world and continues to be a reliable contributor to the world’s building infrastructure.

Continuous Volumetric Metering

Aran Mixer Effectiveness Index History and Report

The history and origination of the Continuous Mixer began in the mid 1980’s.

Aran was founded on a solid focus of excellence in engineered solutions. This is not only apparent in the robust design of the equipment, but a collaborative scientific approach to developing industry standards and construction methods. One example of this is the development of a rationale and equation to objectively measure the effectiveness of mixer types for mixing cementitious materials.

1985, Dutch Stephenson, founder and owner for Stephensons Construction of Washington, bought the second Aran ASR200 mobile pugmill to be used in the USA. Dutch was a pioneer in mixing RCC and CTB, with his first project at the Burlington Northern Railroad in Denver. RCC was still in its infancy in 1985, with some contractors attempting to produce RCC with inadequate equipment. Some projects were poorly completed. It was necessary to prove that the Aran pugmill and material metering feeders had the accuracy and mixing effectiveness necessary to produce a quality RCC mix. Collaborating with Aran and the Portland Cement Association (PCA) Stephenson tested the Aran pugmill in Tacoma, WA with several mix designs. The testing proved the Aran plant could not only produce RCC, but also various traditional designs of slump concrete. Stephenson raised the challenge to Aran to develop a plant primarily focused on Concrete.

In 1986 Aran released the ASR280C (C for Concrete) mobile pugmill. This machine included many new features to improve its capability of material dosing and mixing concrete. These features included a larger cement metering feeder with negative pressure silo, improved aggregate hopper and metering feeder and most importantly, the mixer with a new blade phasing arrangement and various other flexible operating features. To prove the new design Aran invested in ~$300,000 testing program at the Monnier Hard Rock Quarry in Redbank, QLD Australia. Construction Testing Pty Ltd of Brisbane were engaged in June 1986 to test materials produced by the new Aran ASR280C pugmill. The results were also reviewed and ratified by Golder Associates.

Testing included the following samples:
10-30mpa Pavement Type Concretes to assess the following plant performance metrics:

  • Consistency of mix over time, collecting material at 40 second intervals from the start to the end of a production cycle (Batch).
  • Consistency across the mixer and discharge belt from batch to batch. Samples taken at the centre and each edge of the static belt.
  • Consistency – short run reliability of mix at 15 second and 30 second batch run intervals.
  • Air Entrainment evaluation with samples taken at 10, 20, 30 then 15 sec intervals over 90 second total sample production runs, at 10-30mm slump and 50-60mm slump.
  • Water Reducing agent evaluation with the same intervals. 

A large database of records collect confirmed that Aran ASR280C:

  • Demonstrated uniformity of cement feed, whilst the silo was being filled and at various levels.
  • Demonstrated sufficient mixing time and mixing thoroughness by material testing and using colour additives
  • Demonstrated effectiveness of admixtures
  • Slump uniformity

During the trials, Aran tested several mixing blade phasing patterns, blade angles, mixer shaft speeds and entire mixing chamber angles. Some adjustments to mechanical or operational characteristics made very little difference, others made a significant difference in mix quality.

On the strength of these positive test results, Dutch Stephenson ordered another Aran machine, an ASR280C delivered in September 1986.

These testing program results aroused elevated interest in the unique Aran pugmill design and its capacity to produce high quality product, at high instantaneous production rates. It was important to prove the Aran pugmill credentials, differentiating it from other mixing systems traditionally employed.

In October 1986, Trevor Dunstan developed, what is now known at the Mixer Effectiveness Equation or Mixer Effectiveness Index (MEI). Written as an appendix to his white paper titled “Continuous Volumetric Metering of Concrete Ingredients, The Aran Equipment Approach to Accuracy – How it Works”. This paper was presented at various conferences and industry meetings in Australia, USA, China and Europe during the remainder of the 1980’s and early 1990’s. The MEI was later updated in 2006 to include other input data necessary to give a reliable measure for applications when mixers are processing slurries and clays. The original Mixer Effectiveness Index is still used by many designers and contractors today.

Site Visits, Inspections and Condition Reports

Aran performs routine Site Visits for a variety of purposes and is regularly called to perform plant inspections & condition reports, where customers recognize the manufacturer has the best understanding of the equipment. As we are the original continuous mixing manufacturer Aran ensures user equipment is configured for trouble free operations and personnel are adequately trained to ensure owners get the production & durability they have come to expect from their continuous mixing equipment.  These visits not only enable customers by providing them with the tools to improve mixer output and overall performance but Aran utilizes information collected to continue to innovate our continuous mixing equipment, staying ahead of the industry. From parts to training Aran extends their services beyond the scope of just a sale.

Productivity and Safety for over a decade at Indonesian mine.

Productivity and Safety for over a decade at Indonesian mine.

Paste Discharge

We recently visited an Aran modular mixing plant which has proven its weight in gold, producing cemented backfill for the Gossowong underground mine on remote Halmahera island in Indonesia.  Aran visited this remote mine site to perform a condition review of the plant and make recommendations for to ensure its continued successful operation for another decade.

It was impressive to see how well this machine has been maintained after 10 years of highly ulitized operation.  Producing up to 150m3/hr of backfill for schedule critical mining, this plant is an excellent example of high availability as a result robust equipment design and good attention to cleaning and maintenance.

The Gossowong gold mine extracts ore from very narrow seems in areas of fractured and highly stressed rock.  Located in a highly seismic region, this underground mine is presented with many risks to the safety of underground workers.   In order to safely and efficiently extract ore, narrow stopes are created, then quickly filled with cemented paste.  This cemented paste must be strong enough in allow continued mining operations.  Target strengths in some areas can be as high at 2mpa in 7days.   This strength requirement can demand a mix recipe with up to 24% cement for a 230-260mm slump paste.

The Gossowong mine utilises volcanic dust, Tuff, as the primary product in the fill material.  This fine dust like material is incredibly porous, capable of holding up to 35% moisture.  When wet, it can be somewhat challenging to handle.  Additionally the water retained within the Tuff can make the goal of optimising the cement to water ratio, difficult.   Accurate cement addition to the paste backfill mix is critical, not only to ensure fill underground is structurally competent, but cost of the fill is tightly contained.

The Aran backfill plant receives screened Tuff material into a metering hopper which accurately meters the material into the mixer.   Cement, delivered to the mine site in bulk bags, is unloaded and transferred into the mixing plant silo.  Accurately metered cement is then added to the mixer with water for mixing.  The Aran twin shaft, high intensity mixer combines these ingredients, before delivery into the underground reticulation pipeline system.

Whilst the machine’s external appearance represents a plant exposed to the tropics for ten years, mechanically and electrically it is still in excellent condition.   Of course, over ten years of product development, there are many possible upgrades which can be installed on this older machine however, what currently exists on this site is a credit to the owners and operators passion for care and maintenance.  Very few system and hardware upgrades are needed.

If you would like to learn more about what makes Aran mixing systems so accurate and reliable, please ask us.   If you have a project challenge you are confronted with, we would like to listen to your story.


10 year old plant in the tropics of Indonesia

Ten year old plant in the tropics of Indonesia

Aran Cement Bag unloading and transfer system

Aran cement bag unloading and transfer system



Ipswich, Queensland, Australia

Year: 2009

Machine Number:  1081

Customer: Origin Alliance
Location: Ipswich, Queensland, Australia

The upgrade of the Ipswich motorway has been a landmark infrastructure project in Queensland during 2009 to 2010.

An Aran paste backfill plant (MODUMIX II-P) was used to produce mine fill paste and slurry for filling abandoned underground coal mine stopes and tunnels which lay under the new motorway alignment.

Backfill was delivered around the construction site in mixer trucks for pumping underground. The backfill product was based on flyash reclaimed from a local thermal power station, crusher dust, cement, and treated water.

Highly fluctuating moisture contents in the flyash were accommodated in Aran’s intuitive computer control system.