For many years, it has been a tradition to kick off the new construction season in January with the SCHWENK concrete seminars. Not so this year. For the first time in the summer, nearly 600 participants accepted the invitation to attend the concrete seminars hosted by SCHWENK Zement GmbH & Co. KG at the three locations in Schweinfurt, Heidenheim, and Leipzig in late June and early July. Last year, due to the pandemic, interested parties were able to learn about developments within the corporate group in a condensed, digital format via a two-hour livestream.
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The in-person events organized by SCHWENK Bauberatung are a regular fixture on the calendars of clients, concrete manufacturers, construction companies, government officials, architectural and engineering firms, and representatives from universities. They all took advantage of this industry gathering to learn about current topics related to cement and concrete as building materials and to reconnect in person.

Once again, the major themes of decarbonization, climate change, energy costs, and sustainability ran like a common thread through the seminar program. These are the key challenges facing cement and concrete manufacturers now and in the future.

Werner Rothenbacher, head of SCHWENK Construction Consulting, led the seminar program and moderated the discussions. He expressed his delight that the seminars could finally be held in person again.

Dr. Hendrik Möller, a member of the management board of SCHWENK Zement GmbH & Co. KG, welcomed the participants and delivered the opening presentation, “Current Developments at SCHWENK and in the Industry.” The industry currently faces far-reaching decisions that inevitably lead to tensions and strains in its relationships with customers and partners. Much of this is quite complex and requires explanation.

In a retrospective analysis within a historical context, Möller demonstrated that the company has had to overcome many crises since its founding in 1847 and has nevertheless continued to grow over time. SCHWENK, as a company, is therefore well-tested in the face of crises. Setbacks have been embraced as challenges and successfully overcome. In this respect, looking back on 175 years of company history can help put the current situation into perspective, putting certain problems into perspective and, to some extent, offering encouragement. Due to skyrocketing energy prices and supply chain issues, the development of the construction industry currently appears to be at risk. As part of an energy-intensive industry, the sharp rise in electricity costs has a direct impact on manufacturing costs.

Regarding natural gas and crude oil, it was explained that SCHWENK switched the fueling of its cement kilns to nearly 100% alternative fuels years ago. Nevertheless, the impact is directly evident in the high material costs, as illustrated by the example of “refractory material” used for the lining of rotary kilns. Similar to the ceramics and glass industries, these products must be manufactured at high temperatures using virtually ash-free fuel. The refractory bricks are therefore produced at very high temperatures using natural gas. Further price increases, some of them drastic, have occurred for explosives, grinding aids, and NO_x reduction agents.

In the rest of his presentation, he clearly and transparently demonstrates how energy production and CO₂ emissions trading are closely linked, and which scenarios lead to what effects on the cost side.

Finally, an update was provided on the current status of the Celitement flagship project. Last year, the third expansion phase of the pilot plant in Eggenstein-Leopoldshafen was successfully completed. Now that research on this novel binder has been finalized, the project has entered the final phase of market preparation. To provide innovators with sufficient quantities of test material, the existing pilot plant was expanded to a capacity of up to 5 tons per week. Celitement offers unique combinations of properties that were previously unknown for conventional binders. These include very low hydration heat coupled with very rapid strength development, and this is further combined with very high sulfate resistance. Celitement consists of pure CSH phases and is not a binder that fits within the cement standard. For this reason, an application for general building authority approval has now been submitted to the DIBt in Berlin. Experts are currently still deliberating on the very extensive testing plan. According to the current schedule, the first industrial reference plant is expected to begin producing material with building authority approval for the market starting in 2025.

This product innovation offers hope for a breakthrough in the production of additional binders with a low carbon footprint. In this context, Celitement stands on equal footing with well-known Portland cements—developed over 175 years to deliver peak performance and featuring a wide range of properties.

Under the theme “Clinker-efficient cements: balancing availability and performance,” construction consultants Dipl.-Ing. Heiko Zimmermann in Heidenheim and M.Sc. Christian Fratscher in Schweinfurt and Leipzig discussed the challenges facing the cement industry on the path to achieving carbon neutrality by 2050. Particular attention was paid to new binders, future additives, and the planned CI4C plant (Cement Innovation for Climate) in Mergelstetten.

In southern Germany, SCHWENK is in the process of establishing a CEM II/B-M (V-LL) 42.5 N (az) (Allmendingen plant) as a bulk cement for ready-mix concrete. The cement has a general building approval (abZ) in the form of an application approval from the German Institute for Building Technology (DIBt) and can be used for all exposure classes according to DIN 1045-2 / DIN EN 206-1. CEM II/C-M cements in accordance with the new DIN EN 197-5 enable a further step toward CO₂ reduction. These cements, with a content of 36–50 M.-% of two additional main components in addition to clinker, feature a further reduced clinker content. SCHWENK was one of the first manufacturers to receive general building authority approval for a CEM II/C-M (S-LL) 42.5 N (Karlstadt plant) and a CEM II/C-M (V-LL) 42.5 N (Allmendingen plant). These cements demonstrate good performance and are currently suitable for use in all exposure classes except XF2 through XF4. An extension of the approval for the S-LL variant is expected later this year, which will allow for use in all exposure classes. In the future, however, cements such as CEM II/B-LL may be subject to application restrictions or specific application rules. It is therefore essential that concrete manufacturers create storage capacity to be able to use clinker-reduced binders in a component-specific manner and tailored to the exposure classes.

In addition to changes in binding agents, increasing digitalization, material savings in design, and the use of alternative reinforcement, optimized structural systems, and high-performance concrete will play a major role in achieving climate neutrality by 2050.

A far-reaching and comprehensive revision of the regulations governing concrete is on the horizon. The head of the Werner Rothenbacher, Dipl.-Ing., of Bauberatung, provided an overview of the drafts of Parts 1 through 4, as well as the overarching Part 1000, “Fundamentals and Concrete Quality Classes (BBQ),” of DIN 1045. The goal is to categorize the complexity of construction tasks into different concrete quality classes and to clearly define the interfaces between planning, concrete production, and construction execution. The need for communication is to be strengthened; therefore, the intensity of BBQ-N (normal requirements), BBQ-E (increased requirements), and BBQ-S (requirements to be specifically defined) is increasing. Planning and construction were also guided by this tiered system. The classification regarding concrete construction quality depends significantly on the use of the structure, the applicable exposure classes, strengths, and construction methods/curing. Sample classifications provided participants with clarity on the system.

To increase sedimentation stability and thus the durability of concrete, a table specifying a minimum binder volume—based on maximum aggregate size and consistency class—will be introduced in the future. Using calculation examples, Rothenbacher demonstrated that standard, field-proven mix designs generally meet these minimum values. Further additions were made in the area of concrete with recycled aggregates (R-concrete). Accordingly, the provisions of the DAfStb guideline have now been incorporated into the standard and supplemented in some areas. This enables the co-use of Type 1 recycled sand under defined conditions. If everything goes according to plan, the introduction of the regulatory package is expected in 2023. SCHWENK will actively support its customers in implementing these changes within their companies through training and resources.

Due to the increasing effects of climate change, those involved in construction will increasingly need to address the challenge of “concrete construction in hot temperatures.” Construction consultants Dipl.-Ing. Kai Fischer (at the Schweinfurt and Heidenheim venues) and Dipl.-Ing. Sven Mellwitz in Leipzig discussed the measures, possibilities, and limitations in their presentation. They provided an overview of the projected increase in summer and hot days in the medium term, as well as the range of direct effects that fresh concrete temperature has on setting behavior, changes in concrete consistency, plastic shrinkage, and strength development. Since 1978, German regulations have generally limited the fresh concrete temperature to 30 °C on an empirical basis. Specifically, the Additional Technical Contract Conditions (ZTV) in civil or hydraulic engineering sometimes permit only 25 °C. Other countries in Europe and internationally often consider 35 °C as the general upper temperature limit. The cement data sheets and the DBV data sheet “Summer and Winter Concrete Works,” which specifies the “appropriate measures” of DIN 1045-3, are helpful for practical application.

Figure 2: Sven Mellwitz, B.S. in Engineering, © SCHWENK

The speakers supplemented the recommendations with helpful insights from their consulting experience. When developing a special summer mix design—and this is the good news—clinker-efficient cements of the CEM II/B-M, CEM II/C-M, or CEM III types with strength development classes N or L offer technical advantages. For massive structural elements, the addition of admixtures in combination with LH cements can further reduce the heat of hydration within the element. The presentation also provided guidance on the optimal timing for concrete placement and outlined the various options for cooling the three primary concrete raw materials as well as the fresh concrete, e.g., using liquid nitrogen. On the SCHWENK Bauberatung website, a calculation program can be used to determine the effects of cooling measures. Based on data from completed construction projects, the costs and efficiency of the various measures were objectively presented, along with their advantages and disadvantages.

The highly complex and costly process of internal concrete cooling—which involves embedding stainless steel pipes in the concrete and using a cooling water circuit to reduce the core temperature or maintain a temperature difference between the surface and the core of< 15 Kelvin—was demonstrated using the example of the pylon base of the Elbe River Bridge in Magdeburg. Looking ahead, initial results from the research project conducted by the Universities of Bochum and Hannover on the strength development and durability of concrete at fresh concrete and curing temperatures of 20, 30, and 40 °C were presented. It appears that known concrete properties and sufficient durability are likely to be achieved up to 35 °C. Further investigations in a follow-up project will now examine the scientifically interesting range between 35 and 40 °C in greater detail, thereby paving the way for establishing a higher permissible fresh concrete temperature in the regulations.

Concrete construction in hot weather is successful when the necessary tests and organizational measures are carried out in advance by the concrete supplier and the construction site, in close coordination and with a fair distribution of risk.

Using well-founded data and facts on the topic of “The Sustainability of Concrete – Concrete vs. Wood,” the managing director of the Concrete Information Center (IZB), Ulrich Nolting, M.Sc. (Eng.), demonstrated in Schweinfurt and Heidenheim how the two building materials—concrete and wood—are portrayed in stark contrast to one another in the media and among the public, and what potential for the use of wood fundamentally exists. He emphasized that both building materials have their technical merits and stressed how important it is to communicate the advantages and strengths of concrete construction. The one-sided political bias in favor of wood is of little help in this regard.

About 31% of Germany’s land area consists of forest, of which only about 4% cannot be used for logging due to conservation regulations or unfavorable terrain conditions. In 2020, approximately 80 million cubic meters of wood were harvested from the forests. Due to the drought and storm events of recent years, this consists predominantly of damaged timber, mainly spruce, fir, or other conifers. Interestingly, 60% of the harvested wood is used for energy production, while only about 13% actually goes into the construction sector. Since 2006, the share of timber construction in single- and two-family home construction—which accounts for 11% of cement consumption—has grown from 12.8% to 19.7% (2020). For multi-family homes and non-residential construction, the shares remain relatively constant at 2% and 6.6%, respectively. These two sectors account for 21% and 34% of cement consumption in Germany, respectively. To make an accurate estimate of future wood demand, an average wood consumption of approximately 0.3 m^³/m² of gross floor area can be assumed. Based on various evaluated studies, the IZB estimated the future development of the timber construction share and the amount of concrete substituted in building construction using its own calculations. According to these estimates, assuming a doubling of the current timber construction share across the entire building construction sector, a 4% decline in concrete volume is expected.

Despite the modest decline, the mineral-based building materials industry cannot afford to rest on its laurels; rather, it is called upon to meet its climate targets and drive transformation while maintaining open communication. This can be achieved successfully through collaborative action across the value chain, a concrete plan with specific goals, and an open approach to technology. Whether it’s renewable energy, urban development, or infrastructure, Nolting is certain of one thing: the future will certainly not be possible without concrete.

Dr. Thomas Richter, Head of Engineering at IZB, gave the presentation in Leipzig.

Figure 2: Speakers in Heidenheim (from left to right: Dr. Möller, Rothenbacher, Löhr, Zimmermann, Fischer, Nolting), © SCHWENK

During the lunch that followed, all participants had the opportunity to recharge their batteries and discuss the presentations among themselves or with the speakers.

The afternoon at the Concrete Seminars is dedicated to the well-known speakers and experts who present interesting topics beyond the building materials cement and concrete.

In Schweinfurt, Urs Meier—a former referee, soccer expert, and entrepreneur from Switzerland—entertained the audience with his anecdotes and expertise on the topic “Between the Front Lines: Making Decisions Under Pressure.” Using examples from his career as a referee, he demonstrated how he made decisions in a fraction of a second, relying on his experience and gut instinct.

In his talk in Heidenheim, Jörg Löhr, a former national handball player and management coach from Augsburg, gave an engaging presentation on how to achieve “success and motivation in times of change.” Employee motivation is the key to this. He offered tips on how to successfully achieve personal goals with the right mindset.

Neuroscientist Prof. Volker Busch, M.D., from Regensburg captivated the audience in Leipzig with his presentation titled “The Brain Under Pressure.” A look inside the brain reveals ways to deal wisely with sensory overload, multitasking, and our digital daily lives. He shared tips and tricks on how each of us can break free from this cycle.

With up-to-date technical presentations by expert speakers on the topics and challenges facing the building materials industry, this year’s SCHWENK concrete seminars were once again a resounding success. And everyone is already looking forward to the upcoming concrete seminars, which will feature interesting topics in a relaxed atmosphere—in person, of course.