Ultracem 10% Limestone Cement

Holcim’s Ultracem cement has taken a significant step along the path of greater environmental sustainability.  A change in the Ultracem cement composition brings potential savings of 15,000 tonnes of carbon emissions per annum.

This environmental benefit has been made possible by a significant investment in local research and development, inspired by Holcim’s global experience in the increase of the mineral composition of cement.

The change in cement composition has been the addition of extra limestone to the mix. With the cement industry in New Zealand adopting international best practise with the change to New Zealand Standard NZS 3122, mineral additions in cement can increase from 5% to 10%.  The change to the standard is to enable reduction of the clinker factor, thereby improving industry sustainability.  The production of clinker is energy intensive.  Reducing the clinker factor reduces the carbon footprint of cement, making concrete a more sustainable material.

Harvey Tyler, Technical Sales Manager (South Island) for Holcim New Zealand explains, “We now have the potential to reduce the carbon footprint of ready mix concrete by around 11kg of CO2 per cubic metre.  The use of limestone at 10% will bring construction projects closer to earning green building credits under NZGBC Green Star certification.”

“Very pleasing for us has been that our trials have shown comparable performance with current Ultracem and improved performance in some aspects too.  Ultracem 10% limestone cement concrete actually offers better workability, meaning improved finishing for contractors on site,” said Harvey.

The agreement on a revised standard was the culmination of considerable work by the Portland Cement Association of New Zealand and other key industry organisations. Holcim New Zealand has engaged in intensive research and development to reach the point where the market and stakeholders can be assured that there are no disadvantages in adopting the new standard and in the resulting cement performance.

Time-consuming trials were required to establish and prove the new production process. It involved an iterative process of changing one variable per trial.  The trials assessed the impact of changes to the chemistry, hardness and moisture content of the raw materials.  In the milling process, factors such as temperature and quality, fineness, airflow and output rates all had to be carefully controlled to ensure the optimum quality of the product.

Product development field trials were undertaken with concrete contractors and Allied Concrete, one of New Zealand’s largest manufacturers of ready mixed concrete, and Holcim Concrete who collaborated in trials to assess the new cement for chuting, raking, screeding, trowelling and power float.  Viblock Ltd  tested and proved the use of the cement in masonry blocks, whilst Hynds Concrete Products and Stahlton assessed precast and pipes. Cement with 10% limestone addition was proven to maintain the same strengths at all ages as the old 5% mix.  Setting time, drying shrinkage and compressive strength all match or exceed the performance of the 5% product.  Mixing and batching procedures are unchanged.

According to Harvey Tyler, Holcim’s international experience was a huge advantage to Holcim New Zealand in developing the new Ultracem composition.

“We received direct input from Holcim people who were involved in the development of cement for projects such as the Telecom Tower in Germany where 600 tonnes of limestone cement was used and the 57km Gotthard rail tunnel in Switzerland where limestone cement was used for paving throughout,” said Harvey.  “That is the sort of intellectual property that simply is not available to anyone else in New Zealand.”

In Europe, limestone cement (at 6-20% of mix) has been used for some years in many general purpose applications.

Holcim’s international experience and close working relationships with New Zealand stakeholders has been instrumental in achieving the change to cement standard NZS 3122:2009.  The Standards Committee consisted of the University of Canterbury, Portland Cement Association members, the New Zealand Ready Mix Concrete Association, the Institute of Professional Engineers of New Zealand, Standards New Zealand, the New Zealand Concrete Society and the Ministry of the Environment.

Murray Dickson, Holcim National Sales Manager - Cement, confirms, “Reducing clinker factor is a key environmental goal for Holcim.  A 5% reduction in clinker factor is significant, and we will now continue with our research towards achieving cement with an even lower carbon footprint in the future.”