The cement industry is energy intensive and produces significant quantities of greenhouse gases. It accounted for 2-2.5 gigatonnes of CO2 emissions in 2013, or 6.5% of the estimated total worldwide anthropogenic emissions of 37 gigatonnes, according to figures from the Intergovernmental Panel on Climate Change and the International Energy Agency. Some 60% of the CO2 emissions in cement manufacturing are generated during the high-temperature transformation of limestone, a process known as ‘decarbonation’.
The EU has set itself a target of reducing greenhouse gas emissions by 40% by 2030 compared to 1990 levels and a long-term goal of reducing emissions by 80-95% by 2050. Aware of the environmental impacts, cement producers have already taken major measures to reduce cement production-related CO2 emissions. However, such approaches are reaching their limits. The industry must develop new products and technologies that mitigate CO2 emissions in order for it to meet the requirements of EU climate change mitigation policy and to contribute to the transition towards a low emission and climate-resilient economy.
The SOLID LIFE project aimed to demonstrate the feasibility of producing low-emission cement and concrete products on an industrial scale in existing industrial installations. The new products would have cost the same to make as the conventional Portland cement but have superior performance and reduce CO2 emissions by 70%.
The project planned to make use of a low-calcite and non-hydraulic binder called Solidia, which has been under development by the beneficiary since 2013 and subject to testing in Germany, Hungary and the US. The objective was to validate the CO2 savings observed at laboratory scale, through pilot-scale and industrial trials in real cement production facilities, and then in precasting facilities requiring adapted curing chambers with CO2 input. The project also aimed to increase stakeholders’ awareness of the potential emissions reductions and climate action benefits, in line with European policy targets.
The Solidia breakthrough cement/concrete technology was developed in line with the project proposal. While the project proved that the Solidia solution can deliver expected performances and be economically viable (depending on the implementation context), the pace of development was slower than expected, which led to significant departures from the original plans and the reduced scales of the results and impact of the project.
On the other hand, the calculations made during the project showed that a shift from a conventional technology (e.g. Portland cements) to Solidia can reduce carbon footprint by 32% to 67% (cement production and concrete production). This confirms the ambition indicated in the project proposal. Although it is not sufficiently clear at this stage, the project beneficiaries say that this shift will be pursued in the near future, with several pilot and semi-industrial trials foreseen on the short term at European concrete precasters. This indicates that Solidia can penetrate the market in the future.
The project assessed more than 30 different European clinker production lines from LafargeHolcim for Solidia clinker production, carrying out thermodynamic simulations for each plant based on the available raw materials. From these results, the project team then estimated the feasibility of their production. A total of five raw mixes were tested at laboratory scale with materials from the LafargeHolcim plants in Koromacno, Croatia, and Malagoszcz, Poland. Limestone and marls (as calcium sources) were tested with different sands as silica sources. Using the X-ray fluorescence technique (XRF) technique, the raw materials were analysed and milled in the right proportions to reach the targeted chemistries. Lab static kilns were used to assess the potential clinker quality. The obtained results confirmed the predictions of thermodynamics simulations. Similar trials were then performed at pilot scale at IbuTec facilities in Germany, using a two stages pre-heater kiln equipped with a rotary cooler; two tonnes of each clinker were produced. In this way, the project confirmed the robustness of the solution for clinker production and its production in rotary kilns.
Solidia Technologies created concrete specimens from two different concrete mixes with similar mix design (one Solidia cement and one Portland cement reference concrete). Tests showed that their resistance to abrasion and freeze thaw was good and very similar in both mixes. The Solidia concrete showed significantly less creep deformation and lower drying shrinkage than the PC (Portland cement) reference mix.
Two types of concrete block paver products were then produced in plant trials by a UK pre-caster and placed by the AB BRE (as an independent body) into exposure conditions for long-term exposure to natural weathering and in aggressive solutions. Specimens had also been stored in air or water for assessment of long-term shrinkage or expansion. A combination of visual monitoring of deterioration, strength changes, composition and monitoring dimensional changes will be carried out, depending on the exposure conditions.
Mortar specimens, which were prepared from Solidia binder in the CTEC LafargeHolcim’s lab were subjected to various tests to evaluate the behaviour under different environmental surrounding. All tests were carried out in comparison to OPC (Portland) standard mortar specimens, as required for the European Technical Approval. The impact of chemical attack by sulfate solution, acidic or alkali environment was studied over weeks – without detection of inferior resistance of the Solidia specimens. In standard tests using temperature-controlled climate chambers, the specimens’ behaviour in harsh winter condition was assessed by repeated freezing and thawing of the specimens in water and in the presence of salt solution. All these results were regrouped and used to build a European Assessment Document on the Solidia binder.
Furthermore, the project carried out pilot precast trials in Belgium, France, Italy, Sweden and UK. These tests showed that the solution was more aesthetically appealing and had greater strength. Moreover, it also reduces C02 emissions by 70% and allows for 80% of the process water to be recycled, while the equipment used in its production is quicker to clean and leads to less concrete waste. After one of the pilot precast trials, a UK precaster installed an industrial curing chamber on its production site. More than 30 production runs were performed to assess the solution on a larger scale. One run represents 110 boards of pavers and 15 tonnes of concrete. Strengths and freeze-thaw requirements were achieved for some of the runs.
Further information on the project can be found in the project's layman report (see "Read more" section).Prior to the Solid Life project, the beneficiary had drawn up a business model for capitalising on the advantages of the use of Solidia cement over Portland cement. The project then carried out a range of studies, especially related to CO2, which represents a cost for the technology. A mapping study of European sources demonstrated that CO2 costs could be reduced by capturing it directly from industrial flue gases and using it in a gaseous phase. The Solid Life project contributed to EU objectives for GHG emission mitigation (e.g. Climate and energy package). Indeed, the beneficiaries expect that the use of Solidia technology for concrete production could lead to a CO2 reduction of up to 70% compared to Ordinary Portland Cement use. The project, however, is just one important step in a long-term process, and significant challenges lie ahead for commercialising the technology.