Hawaiian Cement re-crushes waste piles into manufactured sand with HRC8

The largest concrete producer in Hawaii

Hawaiian Cement is a vertically integrated construction material company supplying cement, aggregate and ready-mix concrete in Hawaii. The company operates two central-mix concrete plants and a local quarry called Halawa Valley Operations, which provides aggregates for the concrete plants.

Hawaiian Cement's customers include construction contractors and government agencies. Contractors often require concrete mix designs on short notice, while government projects have strict specifications for infrastructure projects. To remain competitive, Hawaiian Cement must maintain a reliable supply of concrete ingredients at an affordable price.

Halawa Valley Operations quarry produces various products, one of which is ASTM C-33 concrete sand used in the production of concrete mixes. This sand is made from a fractured volcanic basalt rock, starting at 24 inches for base material. The crushing circuit consists of a jaw crusher for primary crushing, a gyratory crusher for the secondary stage, a 300hp cone crusher for tertiary crushing and a VSI crusher for the quaternary crushing stage. The material is then sent to a modular wash material plant.

Costly sand outsourcing and struggle with byproducts

The scarcity of sand is a global issue, and the Hawaiian Island market is no exception. Natural sand resources have either been depleted or protected by the state as natural resources. As a result, Hawaiian Cement was left with only two options for acquiring sand: manufacturing it from native aggregate deposits or outsourcing it. While Hawaiian Cement could manufacture some of the sand required for its ready-mix concrete business, the rest had to be outsourced from as far away as British Columbia, Canada, which significantly increased costs due to the distance involved.

Although Hawaiian Cement was able to manufacture some of the sand it needed, it faced the challenge of also producing tons of unusable byproducts. These fractions presented processing difficulties in converting them into usable products, given their high moisture levels. The production of ASTM C-33 concrete sand is a costly process, sometimes resulting in significant quantities of unusable aggregate fractions. These fractions have a real cost, which has already been incurred but offers no commercial value. Additionally, the surplus byproduct needs to be transported and stockpiled, further increasing the overall costs.

“We have been looking for a good solution to re-process the waste material for years. With Metso’s HRC 8, we were able to decrease the amount of imported sand from 50% to 25%”, Jonathan Esperanza, General Manager, Hawaiian Cement.

For four years, Hawaiian Cement searched extensively around the world for a viable and cost-effective solution to add value to its waste fractions. After other processing trials failed, Hawaiian Cement initiated discussions with Miller Machinery, a distributor of Metso. These conversations with Miller Machinery led to the discovery of a new aggregate crushing technology that is specifically engineered to convert waste fractions into manufactured sand.

Proven in mining and gaining popularity in aggregates applications

The technology under discussion was the Planet positive HRC™ Series high-pressure grinding rolls (HPGR). This crushing technology has already proven its worth in mining applications and is well-established in North America. It consumes up to 50% less power compared to other technologies for the same volume of end products. Now, it is successfully gaining traction in aggregates production and sand manufacturing. The staff at Hawaiian Cement were forward-thinking and open to innovations, so companies soon started looking into the possibilities and opportunities available with HRC technology.

After receiving very promising HRC test results from the York test center, Hawaiian Cement became interested in witnessing the predicted performance in a full-size test with HRC8 crusher. Miller Machinery acquired a new HRC8 crusher, mounted it on a portable chassis, and transported the machine more than 2,600 miles (4,300 km) to Hawaii.

“...the waste fraction challenge is commonplace and ongoing so, we mounted the HRC8 on a wheel chassis to make it easier to move inside the pit and transport to other quarry operations”, explains Dave Laird, General Manager, Miller Machinery.

Limitations of traditional solutions

Traditional compression crushers have limitations, especially when dealing with excessive moisture in the feed material. Moisture can cause “packing” inside the crusher cavity, which could lead to internal damage and potential machine failure. Furthermore, smaller aggregate fractions that make up the feed materials are not suitable for processing through a cone crusher, as the process can generally exceed the force limitations of the crushing technology.

Similarly, traditional VSI crushers are often plagued by excessive impact and slide-abrasion wear costs. As the consumable parts wear and change shape, reduction ratios decrease, and output gradations change. Higher moisture feed materials present a high risk of material packing the chamber of the VSI crusher. In addition, VSI's struggled to impart sufficient energy into each feed particle in smaller fractioned feed materials such as those found in the Hawaiian Cement application. This made it difficult to generate the necessary crushing forces to produce meaningful product yield. Finally, the variability in finished output volumes can cause plant flow challenges as the screen capacity requirements change with fluctuations in VSI output in this type of application.

HRC (HPGR) – superior in wet fine crushing applications

The HRC (HPGR) utilizes a different type of crushing action compared to compression and impact crushers, which eliminates operational frustrations commonly experienced in damp to wet fine crushing applications.

“HRC8 crusher is an ideal solution for this case where the feed material is wet. It has a consistent output volume, low variability in reduction ratio and less wear compared to typical VSI crushers, leading to lower maintenance costs,” says Michael Miller, President, Miller Machinery.

The Metso HRC8 solution provided by Miller Machinery includes no impact to Hawaiian Cement’s operational safety profile as the HRC operates quietly with minimal vibration and dust emissions. This, combined with Hawaiian Cement’s entrepreneurial spirit and tenacity to find the best processing solution resulted in operational and financial success, establishing a new best-practice.