7th International VDZ Congress - Verein Deutscher Zementwerke e. V. - ebook

7th International VDZ Congress ebook

Verein Deutscher Zementwerke e. V.

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In September 2013 the VDZ extended a warm welcome to the delegates of the 7th International VDZ Congress "Process Technology of Cement Manufacturing". From 25 - 27 September the congress again served as a forum for the cement industry, with engineers, researchers and equipment suppliers sharing their knowledge on state-of-the-art cement manufacturing technology. Nearly forty speakers from around the world reported on their specialist fields. More than six hundred participants from almost 50 countries heard lectures on topics of high relevance to those working along the value chain of cement and concrete. In times of an about-turn in energy policy, sustainability, energy efficiency and the use of natural resources were again key topics, as well as technical advancement in grinding and burning technology. An outlook on future developments in the global cement and energy markets and research reports on new cements completed the congress programme. Even if the global economy is still facing enormous challenges and the economic growth of the emerging countries has slowed down, cement remains a building material without which modern society could not function. Technological progress and the predicted increase in global demand for cement are the basis for the future growth of our industry. The VDZ Congress 2013 has once again illustrated how cement producers and users, researchers and equipment suppliers can work together to successfully master the challenges our industry faces.

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VDZ Congress 2013Process Technology of Cement Manufacturing

VDZ Congress 2013Process Technology of Cement Manufacturing

Verein Deutscher Zementwerke e.V.P. O. Box 30 10 63, 40410 Duesseldorf, GermanyTannenstrasse 2, 40476 Duesseldorf, GermanyPhone: +49 (0) 211 45 78-1Fax: +49 (0) 211 45 [email protected]

Congress Advisory Board

Klaus BauerEckhard BohlmannWerner CordesWolfgang DienemannBernward GoedeckeGerhard HirthVolker HoenigGernot KirchnerPeter LyhsHendrik MöllerChristoph MüllerMartin OerterJörg RickertStefan SchäferMartin SchneiderVolker SchneiderPeter Scur

SCHWENK Zement KGHeidelbergCement AGPortlandzementwerk WittekindHeidelbergCement Technology Center GmbHDyckerhoff AGSCHWENK Zement KGVDZLafarge Zement GmbHCEMEX Deutschland AGSCHWENK Zement KGVDZVDZVDZVDZVDZHeidelbergCement Technology Center GmbHCEMEX Deutschland AG

VLB-Meldung

Verein Deutscher Zementwerke e.V. (Hrsg.):VDZ Congress 2013Process Technology of Cement ManufacturingDuesseldorf: Verlag Bau+Technik GmbH, 2013

ISBN 978-3-7640-0583-2eISBN 978-3-7640-0593-1

© by Verlag Bau+Technik GmbH, Duesseldorf 2013Produktion: Verlag Bau+Technik GmbH,P. O. Box 12 01 10, 40601 Duesseldorf, Germanywww.verlagbt.de

Klimaneutral gedruckt

Content

Foreword

General Reports

Current Developments and Outlook in Energy Markets

Cecilia Tam, Co-Autor Laura Cozzi

Developments in the Global Cement Market

Joachim Harder

Modern Cement: Requirements as seen from the Construction Industry

Andreas Schaab

Technology Developments in the Cement Industry

Martin Schneider

Theme Session: Future Challenges and Visions of Cement Process Technology

How will the Industry move ahead in Cooperation with the Equipment Suppliers?

Sten Stoltze, Co-Autor Kevin Happ

Customer Focused Clean Technology

Jouni Salo, Co-Author Heiko Schürmann

A Chinese Solution to Change Investment Return Model

Wang Wei

ThyssenKrupp Resource Technologies: A New Company Rich in Tradition

Frank Ruoss

Theme Session: Environmental Technology

High Efficiency SNCR for Non-Calciner Kilns: Potentials and Limits

Rüdiger Matheis, Co-Authors Bernward Goedecke, Dietrich Locher, Markus Pohl

High-Dust SCR Technology: Operational Experience with Catalytic NOx Abatement

Detlef Edelkott

Semi-Dust SCR: Lafarge Plant Mannersdorf (Austria)

Bernhard Köck

Tail-End SCR Technology for the Mitigation of NOx and NH3: Operational Experience at Rohrdorfer Zement

Helmut Leibinger

The New Regenerative Thermal Oxidation (RTO) with Integrated NOx Reduction at the Cement Plant Wopfing, Austria

Gerhard Philipp

Mercury Emissions and Abatement Measures

Daniel Crowley

Theme Session: Sustainability, Use of Energy and Resources

Protection of Biodiversity in Quarries: A Contribution to the Long-Term Sustainability of Natural Resources

Michael Rademacher

Experiences with Waste Heat at Plant Untervaz

Fabio Wider

Waste Heat Recovery and Power Generation in Cement Clinker Production: An Energetic Comparison

Andreas Werner, Co-Author Helmut Leibinger

Energy Efficiency of Cement Production: Levers, Potentials and Limitations

Gernot Kirchner, Co-Author Volker Hoenig

Motivating, Efficient and Flexible: VDZ’s Enhanced Cement Training

Stefan Schäfer, Co-Autor Ludger Thomas

Mill Audits: Tools to Increase Grinding Efficiency

Philipp Fleiger

Theme Session: Grinding Technology

OK Mill: The Optimized and Versatile Grinder

Jesper Havn Eriksen, Co-Autor Luis Petersen

Operational Experience from India’s First MVR Vertical Roller Mill for Cement Grinding

Robert Schnatz, Co-Authors Caroline Woywadt, V.K. Jain

VRM Grinding Technology: A Comprehensive Approach

Daniel Strohmeyer

QUADROPOL RD: The World’s First Vertical Roller Mill with Driven Rollers

Thomas Schmitz

Production of Slag-Containing Cements by Separate Grinding of the Components Portland-Cement and GGBF Slag and Subsequent Mixing

Anton Kollmann

HFCG Roller Press Grinding Systems and their Applications

Bao Wei, Co-Autors Gao Lin, Ding Hao

Theme Session: Burning Technology

From Municipal Solid Waste (MSW) to Energy

Sandro Buzzi

Improved RDF Quality and Combustion due to the Drum Drier, Chelm, Poland

Jaroslaw Sawecki

New 3000 tpd Line in Rezzato, Italy: Innovation for Sustainable Production

Giovanni Cinti, Co-Autor Joys Riva

How to Protect the Kiln Shell against Corrosion

Marcel Bieri

Low Temperature Corrosion in Cement Plants

Christian Suchak, Co-Author Volker Hoenig

Theme Session: Cement and Concrete

Low Clinker Ternary Cements: Performance and Standardization

Michel Delort

10 Years of Nanocem: Research Highlights

Karen Scrivener

Belite Calciumsulfoaluminate Ternesite (BCT): A New Low Carbon Clinker Technology

Wolfgang Dienemann, Co-Authors Mohsen Ben Haha, Frank Bullerjahn, Dirk Schmitt

Belite Rich Portland Cement and Concrete

Sui Tongbo, Co-Authors Fan, Lei, Wang, Jing, Wen Zhailun

Celitement: Where do we stand?

Hendrik Möller

Durability Requirements for Concrete Today and in the Future

Christoph Müller

Foreword

In September 2013 the VDZ extended a warm welcome to the delegates of the 7th International VDZ Congress “Process Technology of Cement Manufacturing“. From 25 - 27 September the congress again served as a forum for the cement industry, with engineers, researchers and equipment suppliers sharing their knowledge on state-of-the-art cement manufacturing technology.

Nearly forty speakers from around the world reported on their specialist fields. More than six hundred participants from almost 50 countries heard lectures on topics of high relevance to those working along the value chain of cement and concrete. In times of an about-turn in energy policy, sustainability, energy efficiency and the use of natural resources were again key topics, as well as technical advancement in grinding and burning technology. An outlook on future developments in the global cement and energy markets and research reports on new cements completed the congress programme.

Even if the global economy is still facing enormous challenges and the economic growth of the emerging countries has slowed down, cement remains a building material without which modern society could not function. Technological progress and the predicted increase in global demand for cement are the basis for the future growth of our industry. The VDZ Congress 2013 has once again illustrated how cement producers and users, researchers and equipment suppliers can work together to successfully master the challenges our industry faces.

The VDZ would like to express special thanks to all those who played a part in the success of the congress. In particular, the VDZ thanks the Congress Advisory Board under the leadership of Volker Schneider, the HeidelbergCement Technology Center and the VDZ Board. Special thanks are extended to all authors and coauthors and the organizing team of the VDZ Research Institute in Duesseldorf, without whom the congress would not have been possible.

Gerhard HirthPresident VDZ

Duesseldorf, October 2013

General Reports

Current Developments and Outlook in Energy Markets

Cecilia Tam; Laura Cozzi,International Energy Agency,Paris, France

1 Introduction

The global energy map is changing, with potentially far-reaching consequences for energy markets and trade. It is being redrawn by the resurgence in oil and gas production in the United States and could be further reshaped by a retreat from nuclear power in some countries, continued rapid growth in the use of wind and solar technologies and by the global spread of unconventional gas production. Taking all new developments and policies into account, the world is still failing to put the global energy system onto a more sustainable path. Global energy demand grows by more than one-third over the period to 2035 in the New Policies Scenario (the IEA’s central scenario), with China, India and the Middle East accounting for 60 % of the increase. Energy demand barely rises in OECD countries, although there is a pronounced shift away from oil, coal (and, in some countries, nuclear) towards natural gas and renewables. Despite the growth in low carbon sources of energy, fossil fuels remain dominant in the global energy mix.

2 Outlook for fossil fuels

Energy developments in the United States are profound and their effect will be felt well beyond North America – and the energy sector. The recent rebound in US oil and gas production, driven by upstream technologies that are unlocking light tight oil and shale gas resources, is spurring economic activity – with less expensive gas and electricity prices giving industry a competitive edge – and steadily changing the role of North America in global energy trade. By around 2020, the United States is projected to become the largest global oil producer (overtaking Saudi Arabia until the mid-2020s) and starts to see the impact of new fuel-efficiency measures in transport. The result is a continued fall in US oil imports, to the extent that North America becomes a net oil exporter around 2030. This accelerates the switch in direction of international oil trade towards Asia, putting a focus on the security of the strategic routes that bring Middle East oil to Asian markets. The United States, which currently imports around 20 % of its total energy needs, becomes all but self-sufficient in net terms – a dramatic reversal of the trend seen in most other energy importing countries.

No country is an energy “island” and the interactions between different fuels, markets and prices are intensifying. Most oil consumers are used to the effects of worldwide fluctuations in price (reducing its oil imports will not insulate the United States from developments in international markets), but consumers can expect to see growing linkages in other areas. A current example is how low-priced natural gas is reducing coal use in the United States, freeing up coal for export to Europe (where, in turn, it has displaced higher priced gas). At its lowest level in 2012, natural gas in the United States traded at around one-fifth of import prices in Europe and one-eighth of those in Japan. Going forward, price relationships between regional gas markets are set to strengthen as liquefied natural gas trade becomes more flexible and contract terms evolve, meaning that changes in one part of the world are more quickly felt elsewhere. Within individual countries and regions, competitive power markets are creating stronger links between gas and coal markets, while these markets also need to adapt to the increasing role of renewables and, in some cases, to the reduced role of nuclear power.

Natural gas is the only fossil fuel for which global demand grows in all scenarios, showing that it fares well under different policy conditions; but the outlook varies by region. Demand growth in China, India and the Middle East is strong: active policy support and regulatory reforms push China’s consumption up from around 130 billion cubic metres (bcm) in 2011 to 545 bcm in 2035. In the United States, low prices and abundant supply see gas overtake oil around 2030 to become the largest fuel in the energy mix. Europe takes almost a decade to get back to 2010 levels of gas demand: the growth in Japan is similarly limited by higher gas prices and a policy emphasis on renewables and energy efficiency.

Unconventional gas accounts for nearly half of the increase in global gas production to 2035, with most of the increase coming from China, the United States and Australia. But the unconventional gas business is still in its formative years, with uncertainty in many countries about the extent and quality of the resource base. There are also concerns about the environmental impact of producing unconventional gas that, if not properly addressed, could halt the unconventional gas revolution in its tracks. Public confidence can be underpinned by robust regulatory frameworks and exemplary industry performance.

Coal has met nearly half of the rise in global energy demand over the last decade, growing faster even than total renewables. Whether coal demand carries on rising strongly or changes course will depend on the strength of policy measures that favour lower-emissions energy sources, the deployment of more efficient coal-burning technologies and, especially important in the longer term, CCS. The policy decisions carrying the most weight for the global coal balance will be taken in Beijing and New Delhi – China and India account for almost three-quarters of projected non-OECD coal demand growth (OECD coal use declines). China’s demand peaks around 2020 and is then steady to 2035; coal use in India continues to rise and, by 2025, it overtakes the United States as the world’s second-largest user of coal.

3 Trends in the power sector

The growth in renewable power technologies continued in 2012 despite economic, policy and industry turbulence. Solar PV capacity grew by an estimated 42 %, and wind by 19 % compared with 2011 cumulative levels. Markets for renewable energy are broadening well beyond OECD countries, which is very positive.

This reflects generally rising ambitions in clean energy although developments are not homogenous. For instance, China and Japan strengthened policies and targets for renewables in 2012 while other governments (e.g. Germany, Italy and Spain) scaled back incentives. Coal technologies continue to dominate growth in power generation, despite rapid growth in renewable power technologies. This is a major reason why the amount of CO2 emitted for each unit of energy supplied has fallen by less than 1 % since 1990.

The world’s demand for electricity grows almost twice as fast as its total energy consumption, and the challenge to meet this demand is heightened by the investment needed to replace ageing power sector infrastructure. Of the new generation capacity that is built to 2035, around one-third is needed to replace plants that are retired. Half of all new capacity is based on renewable sources of energy, although coal remains the leading global fuel for power generation. The growth in China’s electricity demand over the period to 2035 is greater than total current electricity demand in the United States and Japan. China’s coalfired output increases almost as much as its generation from nuclear, wind and hydropower combined. Average global electricity prices increase by 15 % to 2035 in real terms, driven higher by increased fuel input costs, a shift to more capital-intensive generating capacity, subsidies to renewables and CO2 pricing in some countries. There are significant regiosnal price variations, with the highest prices persisting in the European Union and Japan, well above those in the United States and China.

The anticipated role of nuclear power has been scaled back as countries have reviewed policies in the wake of the 2011 accident at the Fukushima Daiichi nuclear power station. Japan and France have recently joined the countries with intentions to reduce their use of nuclear power, while its competitiveness in the United States and Canada is being challenged by relatively cheap natural gas. Our projections for growth in installed nuclear capacity have declined and while nuclear output still grows in absolute terms (driven by expanded generation in China, Korea, India and Russia), its share in the global electricity mix falls slightly over time.

Renewables become an indispensable part of the global energy mix and by 2035, account for almost one-third of total electricity output. Solar grows more rapidly than any other renewable technology. By 2015, renewables are the world’s second-largest source of power generation (roughly half that of coal) and, by 2035, they approach coal as the primary source of global electricity. Consumption of biomass (for power generation) and biofuels grows four-fold, with increasing volumes being traded internationally. The rapid increase in renewable energy is underpinned by falling technology costs, rising fossil-fuel prices and carbon pricing, but mainly by continued subsidies: from $88 billion globally in 2011, they rise to nearly $240 billion in 2035. Subsidy measures to support new renewable energy projects need to be adjusted over time as capacity increases and as the costs of renewable technologies fall, to avoid excessive burdens on governments and consumers.

4 Energy and emissions in the cement sector

Growth in global energy demand will be closely linked with industrial activity and efforts to improve energy efficiency will be central to keeping emissions from industry under control. As the third-largest industrial energy user (13 EJ in 2010 equal to energy consumption of Japan) and second largest industrial CO2 emitter (2.1 Gt CO2 in 2010 equal to emissions of India1 and the United Kingdom combined ), developments in the cement industry can have wider impacts on the energy sector and future of climate change. To achieve ambitious energy and emissions reduction in the sector will require the use of alternative fuels, clinker subtitles and CCS, as well as raising thermal and electric efficiency. Progress on energy efficiency over the last decade is encouraging, but could still be improved by an estimated 2.5 EJ (around 25 % of 2010 levels) by applying best available technology globally. Significant reduction in emissions will require demonstrating CCS over the next decade and rapid deployment thereafter.

5 References

IEA (International Energy Agency) 2013, Tracking Clean Energy Progress 2013, IEA/OECD Paris

IEA 2012, World Energy Outlook 2012, IEA/OECD, Paris

IEA 2012, Energy Technology Perspectives 2012, IEA/OECD, Paris

1 From fuel combustions.

Developments in the Global Cement Market

Joachim Harder,Onestone Consulting SL,Barcelona, Spain

1 Summary

At the moment, all eyes in the cement industry are directed at the emerging countries, because these are practically the only markets showing a growth in cement consumption. But what markets will follow the so-called BRIC countries? Here forecasts for the period up to 2030 will be presented. Additionally two examples will be given, how the equipment markets and market shares of suppliers have changed in recent years. The one example is on grinding equipment in the cement industry, the other is on waste heat recovery (WHR) systems.

2 Introduction

The so-called BRIC countries Brazil, Russia, India and China lost some of their shine in 2012. Fund managers are now arguing about who has the best proposal regarding the countries that will follow BRIC. Will it be the so-called CIVETS (Columbia, Indonesia, Vietnam, Egypt, Turkey and South Africa)? Or maybe the "Next Eleven" with Bangladesh, Egypt, Indonesia, Iran, Mexico, Nigeria, Pakistan, the Philippines, Turkey, South Africa and Vietnam?

The cement industry is well advised not to lose sight of the main cement markets, because economic growth and average income, taken alone, do not possess enough informative value to form a sound basis for cement consumption forecasts. Important information regarding the future development of demand for cement can be derived from the development of the rate of investments, the per-capita consumption, the population development, the buying power of the middle class, the rate of urbanization and the housing requirements.

However, it must not be forgotten that there have been many examples where cement demand forecasts have been proven wrong by actual developments.

Major issues under discussion:

■   Cement companies and suppliers want to be well prepared for the future, but what will the future look like?

■   All eyes in the cement industry are directed to “Emerging” markets. But what will come after the BRIC-countries? Is it the CIVETS or something different?

■   The expansion of cement capacity forms the basis of new growth, but what about the market dynamics and how much growth will be possible?

■   The cement equipment market is undergoing a change. What are the prospects for the future and what will it look like e.g. for grinding equipment, which today has the largest market potential of all cement equipment categories?

■   Cement equipment was mainly introduced by Western suppliers, but is this also true e.g. for waste heat recovery systems, which have now became a major investment issue?

3 Cement market outlook 2030

Figure 1 shows the expected global cement production figures up to 2030 categorized by groups of countries. The mature markets are those of Western European countries, the USA, Canada, Japan, Australia and New Zealand. The BRIC-countries Brazil, Russia, India and China have already been introduced. The SETIVIM countries are Saudi Arabia, Egypt, Turkey, Iran, Vietnam, Indonesia and Mexico. These seven countries all have a cement production rate exceeding 30 million tons per year (Mta) and have strongly increased their production capacities in recent years.

Figure 1: Global cement production by 2030.

The category "Next7" is used for the emerging countries Algeria, Morocco, Nigeria, Pakistan, Malaysia, Thailand and the Philippines, who all have cement production rates of 10 Mta to 30 Mta. The "others" include so-called transition countries such as South Africa, South Korea, Taiwan, Singapore, the United Arab Emirates and Central European countries like Poland, the Czech Republic and Hungary, as well as emerging countries like Ethiopia, Bangladesh, Columbia, Kazakhstan and Myanmar.

The main factor influencing global cement production up to 2030 will be the further development of the BRIC countries, particularly India and China. The latest figures indicate that cement production will rise from 3,270 Mta in 2010 to 4,370 Mta in 2020, i.e. with an average growth rate of only 2.9 %. The expected cement production in 2030 is 4,830 Mta, i.e. the average annual worldwide growth rate will then be only 1 %. Over the entire period, the mature markets will show practically no growth at all. Between 2020 and 2030, production in the BRIC countries will only rise from 2,900 Mta to 2,910 Mta. This will have a drastic effect on the growth of the global cement industry. The highest percentage growth rates will be achieved by the SETIVIM countries, the Next7 and the other emerging countries. The cement production rate of these 3 groups of countries will increase from 701 Mta in 2010 to 1,510 Mta in 2030. The compound annual growth rate of these countries will be 4.3 % in the period 2010-2020 and 3.5 in the period 2020-2030.

The cement production capacities of the BRIC countries have been massively expanded, particularly in China and India. More recently, Brazil and Russia have also implemented capacity expansion measures, but on a smaller scale. In India, it can be presumed that cement production capacity will reach a level of around 340 Mta in 2013, after 290 Mta in 2011. By 2016, the country's cement production capacity is expected to rise to 405 Mta. In China, a total of 238 new clinker production lines were constructed in 2011 and 2012, representing a new capacity of 325 Mta. However, in the coming years the rise in new production capacity is expected to be significantly lower, even though uneconomical plants with a capacity of around 250 Mta are due to be shut down between 2013 and 2015.

Figure 2 presents a cement production forecast for the BRIC countries up to the year 2030. According to this forecast, China will produce approx. 2,350 Mta of cement in 2020. This figure is only slightly higher than that for 2012 (2,210 Mta). This forecast is based on the expectation that cement production in China will only go on increasing until 2016/2017 at a maximum, and will then start declining. In 2011 the country's rate of production increase was still 11.7 %, but in 2012 it had slowed to 5.7 %. For 2030, it is anticipated that China's cement production will decrease to 2140 Mta. India's production rate was 212 Mta in 2010. It is expected to rise to 400 Mta in 2020 and to around 580 Mta in 2030. Brazil may be able to almost double its 2010 production volume of 59 Mta to 105 Mta in 2030. However, this year the country's cement sales are showing a distinctly lower rate of increase. Sales in the first 5 months of 2013 only rose by 1.3 % compared to 2012. In contrast, cement production in Russia rose by 12.8 % in the first 4 months of 2013. However, the country's production figures for 2020 and 2030 are difficult to forecast with confidence, due to previous market slumps.

Figure 2: Cement production of the BRIC countries by 2030.

The compound annual growth rates of cement production in the BRIC countries are depicted in Figure 3. Due to the enormous growth in China, the 4 countries achieved a CAGR of 10.7 % in the period 2000-2012. From 2010-2020, growth will decline to 2.9 %, and the period 2020-2030 will even be marked by zero growth. The decline in China will mainly be compensated by growth in India.

Figure 3: CAGR in cement production of the BRIC countries by 2030.

The definition of the SETIVIM countries is a OneStone Consulting suggestion. The seven countries Saudi Arabia, Egypt, Turkey, Iran, Vietnam, Indonesia and Mexico are - as far as the cement industry is concerned -almost on the same level as Russia and Brazil, and have experienced an above-average cement production growth in recent years. Among the cement producing countries that are currently showing the strongest growth are Indonesia [1] and Iran. Of the 7 countries, Mexico and Egypt are somewhat behind the others. Mexico was more severely affected by the real estate crisis in the USA and the subsequent global slump than other countries. In Egypt, the pro-democracy uprising brought the country to the brink of a national crisis. Nevertheless, the cement industries in both countries have recovered well and - like the other countries Vietnam, Saudi Arabia and Turkey can look forward to a prosperous future.

Figure 4 is a cement production forecast for these countries up to 2030. The quantity produced will more than double, from 330 Mta in 2010 to 720 Mta in 2030. The biggest increases are expected for Indonesia (+98 Mta) and Iran (+75 Mta), while Saudi Arabia and Egypt should have increases of +60 Mta and +57 Mta. The remaining countries have growth rates of less than 40 Mta: Vietnam (+36 Mta), Mexico and Turkey (+32 Mta each). In Indonesia, cement consumption rose by 8.6 % in the first 4 months of 2013 compared to the preceding year.

Figure 4: Cement production of the SETIVIM countries by 2030.

Turkey even achieved a cement production growth of 38 % in the 1st quarter of 2013. In Saudi Arabia cement production increased by 7.4 % in the first 5 months of 2013. In the same period of 2013, Vietnam's cement production rose by 19 % over the previous year, although 2012 had concluded with a negative growth of 3.5 %. Iran raised her cement production by 7.1 % last year and in 2013 is aiming to increase cement exports by almost 40 %.

Figure 5 provides the forecast data for the CAGR of cement production in the SETIVIM countries. In the period 2010-2020 the expected average growth of all the countries is 4.7 %. The subsequent annual growth in the period 2020-2030 is forecast to be 3.3 %. Indonesia, Saudi Arabia and Iran will enjoy the highest growth rates, while the smallest future growth rates are expected to take place in Turkey, Mexico and Vietnam. Vietnam has undergone a distinct loss of vitality compared to the high growth rates of the years up to 2010.

Figure 5: CAGR in cement production of the SETIVIM countries by 2030.

The group of "Next7" countries comprises Algeria, Morocco, Nigeria, Pakistan, Malaysia, Thailand and the Philippines. Apart from the fact that these countries all have cement production quantities of 10 to 30 Mta, they have few common points. The country that is currently hitting the headlines in a big way because of its rapid expansion of production capacity is Nigeria. However, in 2010 Nigeria only had a cement production rate of 10 Mta. In contrast, Pakistan had a cement output of 27 Mta in 2010, but since that year its production capacity has been a constant 44.8 Mta.

In Thailand the situation is similar, in that the cement production capacity of 56.6 Mta has remained the same for years, as the country's cement industry has a large surplus capacity and only manages a capacity utilization rate of 50 %. On the Philippines, the cement consumption and cement production rates have also stagnated in recent years, and are lagging far behind expectations. The North African flagship countries Algeria and Morocco have also disappointed expectations in recent years.

Figure 6 presents the cement production forecast for the Next7 countries up to 2030. This prediction sees a significant increase in the cement production output of these countries from 132 Mta in 2010 to 201 Mta in 2020 and 287 Mta in 2030. Nigeria looks set to have the biggest absolute increase of +30 Mta, followed by Pakistan (+25 Mta), Morocco (+22 Mta), Algeria and Thailand (+20 Mta each), and Malaysia and the Philippines (+19 Mta each).

Figure 6: Cement production of the “Next7” countries by 2030.

However for some of the countries it will probably be difficult to achieve the desired growth targets. In Morocco, for example, cement sales grew by 10.7 % from 2011 to 2012. However, in 2012 cement sales dropped by 1.6 % and in the first 5 months of 2013 they have declined further by 14.5 % compared to the preceding year. This scenario had not been expected by even the worst pessimists in 2011. A stark contrast to this is presented by the current cement consumption in Nigeria, which has shown an average annual increase of 10.2 % from 2007 to 2012.

The CAGR of the Next7 countries is depicted in Figure 7. According to this forecast, the cement production of these countries will increase by 4.3 % in the period 2010-2020 and by 3.6 % from 2020 to 2030. Nigeria has the biggest forecast growth rate of 7.7 % (2010-2020) and 6.7 % (2020-2030). Large growth rates of between 4 and 5 % are also forecast for Algeria and Morocco. Malaysia, the Philippines and Pakistan will have a rate of 3-4 %, while that of Thailand will remain below 3 %.

Figure 7: CAGR in cement production of the “Next7” countries by 2030.

3.1 Grinding market development

A new market report on the grinding equipment for the cement industry was published in June 2013. The market data were mainly received from the reference lists (supply records) of the cement industry mill suppliers. The market data were split into the local market in China and the market in the Rest of the World (RoW) [2].

The number of orders in RoW peaked in 2008 with 289 (Figure 8). In 2009 there was a decline by 41.2 % to 170 units. A significant recovery was in 2010 with 200 mill orders, respectively an increase of 17.6 %, when compared with 2009. From 2011 on the mill orders were about constant and well under 200 units.

Figure 8: Mill orders in cement industry, excl. local supply in China.

Figure 9 indicated that the RoW market is dominated by vertical roller mills (VRM), although their number declined from 171 units in 2008 to 113 units in 2012. High pressure grinding rollers (HPGR) have been on the same order level in 2008 and 2011/2012 with 27 units, although they peaked in 2010 with 50 units. Ball mills (tube mills) declined from 88 units in 2008 to 51 units in 2012. Only one Horomill was ordered from 2010 on.

Figure 9: Mill orders by mill type, excl. local supply in China.

The local mill orders in China were significantly above those of the RoW. Just from 2010 to 2012 about 1611 mills have been ordered by the Chinese cement industry from local suppliers (Figure 10). The market figures were derived from the new clinker production lines becoming operational with 1 year lead time and 4.8 mills on average per production line. Nevertheless in the coming years the orders will be significantly lower because less new cement and clinker capacity will be made operational.

Figure 10: Local mill orders in China, excl. foreign supply.

The mill supply to China by foreign mill manufacturers has declined since 2008 (Figure 11). After 43 orders in 2008, only 12 orders were awarded to foreign suppliers in 2012. Most of the mills ordered are for clinker and slag grinding. VRM have a share of 98 %. Two Horomills and no ball mills and no HPGR were supplied to China.

Figure 11: Foreign mill supply to China, excl. local supply.

The market potential for new grinding equipment, excl. the local market in China, peaked in 2008 with about 2.5 US$bn (Figure 12). In 2009 only a market volume of 1.45 US$bn has been achieved, in 2012 the figure was at about 1.63 US$bn. Most of the market potential, respectively 53 % is for clinker grinding, 31 % for raw materials grinding, 13 % for slag grinding and only 4 % is for coal grinding. For the coming years it is expected that the share for clinker and slag grinding will further increase, while raw materials and coal grinding will decrease due to a decreasing clinker factor and the fact that the clinker capacity will grow slower than the cement/cementitious grinding capacity.

Figure 12: Market potential for new mills, excl. local market in China.

3.2 WHR market development

In recent years, power generation from waste heat has become an important topic in the cement industry. The main reasons for this are rising electrical power costs, improvements in the economy of plant operation, the need to reduce power consumption and, finally, environmental protection and the reduction of CO2 emissions.

An analysis of the available technologies for power generation from waste heat shows that there are 3 different processes, which all have their advantages and disadvantages:

1.  Steam Rankine Cycle (conventional steam process)

2.  Organic Rankine Cycle (ORC)

3.  Kalina Cycle

Conventional steam processes utilize the waste heat from the exhaust air of the preheater and clinker cooler to produce steam in waste heat boilers. The superheated steam then drives steam turbines and generates electricity in a similar manner to power stations. However, while modern power stations achieve net efficiency rates of approx. 60 %, WHR systems operating with substantially lower pressure and temperature profiles only reach an efficiency range of 20-25 %. In the ORC process, an organic fluid is used instead of the water/steam circuit in order to improve the efficiency of the low-temperature power generation. The Kalina process makes use of an ammonia/water mixture as the process fluid. This enables the utilization of even lower exhaust gas temperatures than the ORC process.

Figure 13: WHR systems by technology (2012).

At the moment, China has 739 systems, which represents a share of 85.4 % of the global market. The TOP5 user countries: China, India, Japan, Thailand and Pakistan have 810 systems, which represents almost 95 % of the market. Asia alone, excluding the Middle East, accounts for 96.5 %, while the Middle East has 1.7 % and the rest of the world with Europe, America, Africa and Oceania has 1.8 % (Figure 14). Aside from the above-named countries, there are meanwhile a number of WHR systems in service or under construction in Taiwan, South Korea, Vietnam, the Philippines, Turkey, Saudi Arabia, the Emirates, Germany and Switzerland. Orders for WHR systems outside of China have significantly increased in the last three years. While in 2010 only seven WHR systems were ordered outside of China, the number had already risen to 17 in 2011 and a total of 19 in 2012.

Figure 14: WHR units by region/country (2012).

These figures only represent the number of generator systems and not the number of waste heat boilers, which is far higher.

Figure 15 shows how the figures for China have developed since 2005. This overview only includes the systems that are actually in operation. After relatively low numbers in the initial years, 2009 was a boom year with 181 systems put into operation. Since then, the number of new systems has steadily decreased.

Figure 15: WHR units in China.

In China, WHR systems have hitherto been installed in 60 % of modern kiln lines. Individual cement producers like Anhui Conch have already equipped practically all their modern kiln lines with WHR systems. Up to April 2013, Conch had 61 systems in operation with a nominal capacity of almost 700 MW. The average annual plant availability was at the high level of 97.9 %. In total, Chinese cement plants had a nominal WHR system capacity of 6575 MW by the end of 2012, i.e. the average system size is 8.9 MW.

The capital costs for WHR systems depend on a variety of parameters. A Holcim publication stated that the specific system costs primarily depend on the system capacity and the economy of scale respectively [4]. Correspondingly, the required investments range from 2 million US$ per MW for system capacities of 25 MWel up to 7 million US$ per MW for system capacities of 2 MWel. HeidelbergCement calculated the capital expenditure for Chinese systems supplied in 2010 in different regions [5] (Figure 16). The price levels are valid for a 5000 t/d clinker production line equipped with a 4 to 5-stage preheater and with raw material moisture contents of 3-4 %, i.e. WHR system capacities of around 9 MW. The data show that the price level in China is only about half as high as that prevailing in Europe.

Figure 16: Price level of Chinese WHR technology for 5,000 tpd, 4-5 stage preheater, 3-4 % moisture (Heidelberg-Cement).

Due to the low capital cost of the Steam Rankine process, ORC and Kalina systems still have a competitive disadvantage. Turboden [6] states that the capital cost for ORC systems are € 2.5 m per MW in the most inexpensive case (10 MW capacity), ranging up to € 4.5 m in the most expensive case (1 MW capacity). However, the big monetary advantage of ORC systems is that their operating costs and maintenance expenses (O+M) are very low by comparison, at only € 0.035 m per MW and year.

4 Conclusion

The main factor influencing global cement production up to 2030 will be the further development of the BRIC countries, particularly China and India.

Highest percentage growth rates will be achieved by SETIVIM countries, the Next7 and other emerging countries. CAGR of these countries will be 4.3 % in the period 2010-2020 and 3.5 % in the period 2020-2030.

Equipment markets show (e.g. grinding sector) that peak orders of 2008 could not be achieved any more. The market share of VRMs has increased in the last few years, while the market shares of the other mills (especially the ball mills) have decreased. There is also a trend to clinker and slag grinding, while raw material grinding and coal will further decline, due to the worldwide trend of lower clinker factors in cement.

The market share of Chinese suppliers in international markets has significantly increased and it is expected that this trend will continue with the growing market shares of the Chinese EPC contractors and the increasing mill references of Chinese suppliers.

The WHR market has expanded dynamically in China and other Asian markets. About 865 WHR systems have be in operation or under construction by 2012. Market leaders are mainly from China, supplying conventional steam cycle technology, while non-conventional technology is offered by Western suppliers.

5 References

[1]   Harder, J.: Cement Markets in the BRIC Countries and other Emerging Markets up to 2030. ZKG International 8/2013

[2]   OneStone Consulting: Grinding Market in Cement by 2017. Multi-Client Market Report, June 2013, Barcelona, Spain

[3]   Harder, J.: Latest Waste Heat Utilisation Trends in Cement Plants. ZKG International 6/2013

[4]   HOLCIM (2011): Waste Heat Recovery Pilot Installation at Untervaz Plant. HGRS-CMS/ECT Meeting, 7-8th June, 2011, Holderbank, Switzerland

[5]   Theulen, J. (2012): WHPG @ HeidelbergCement: Potential Evaluation & Operational Experience. Presentation at Global CemPower. 14-15 June 2012, London, UK

[6]   Turboden (2013): Turboden Plants for Industrial Heat Recovery. Document 11-COM.P-18-rev.21, 23/01/2013, Brescia, Italy

Modern Cement: Requirements as seen from the Construction Industry

Andreas Schaab,HOCHTIEF SOLUTIONS AG,Consult Materials,Mörfelden-Walldorf, Germany

1 The initial situation

The production of cement for concrete began about 160 years ago. Since then, significant changes in technology have been made in both cement manufacturing and in the production of concrete. Initially, the production of cement and its compressive strength properties were in the focus of development. Back then, similar to cement production, the main focus when producing concrete was the manufacturing process and its compressive strength properties.

A rapid development in the manufacturing of cement and concrete was triggered for preparations of the Second World War and the reconstruction of Europe after this war. The concrete production became increasingly industrialized, therefore, concrete was produced less locally and more in the central regions as ready-mix concrete and delivered to the construction site. The concrete pump was used to replace the crane bucket more frequently and the use of precast concrete allowed rapid progress.

Further development in the manufacturing technologies and consequent modernization allowed the cement production in West Germany to reach its peak in the early 1970’s.

The following decades were marked by the first oil crisis which triggered the economic crisis with strong orientations on energy efficiency, environmental protection and process cost optimization in both, cement and concrete production. In cement production the fuel oil was then substituted back to coal and secondary fuels were used more and more.

At the same time, a progressively larger proportion of cement clinker was replaced by other main constituents. The use of different main constituents and secondary fuels makes the production of evenly high-quality cements more ambitious.

At the same time, concrete requirements have been increased and intensified due to new concrete admixtures. By including life cycle cost as well as the service life of the construction itself in the planning, even more and stronger requirements were made for the concrete.

The development in the chemical industry also changed the concrete technology. Concrete admixtures were previously mainly produced from waste materials of other production sectors. However, since the last millennium, more and more synthetic concrete admixtures for specific application profiles were produced. This makes it easier to produce concrete with lower water/cement ratios in order to improve the durability or to increase the compressive strength of the concrete. In addition to this development, it can be observed that a trend towards softer concrete consistencies is made to enhance performance and improve the quality of concrete workability. These previously shown tendencies almost inevitably lead to increased sensitivity of the concrete mix. This has lead to an increase in the sensitivity to variations such as the concrete constituents, the manufacturing process or the temperature.

The temporal changes of the source materials show most evidently in changes in the properties of fresh concrete, which partially exceed the acceptable level because they change the properties of the hardened concrete or lead to significant loss of productivity or to a process change.

Therefore, the uniformity of the concrete constituents is an elementary key ingredient in the production chain of concrete particularly for infrastructure and industrial structures such as roads, bridges, tunnels, hydraulic structures, water treatment plants, sewers, buildings for the chemical industry, agriculture and constructions for power generation (power plants, cooling towers, waste bunkers, etc.). The durability requirements and availability of such structures are generally very high. In addition, these structures must be built industrially in shorter construction times, often under difficult work conditions and limited production space. Considering that cement is used as the main source material for concrete, increasingly extended and additional requirements must be made to meet the global demands of the durability of concrete structures even under the present conditions.

Therefore, by using some examples from the construction practice, problems with the uniformity of the main constituents that are partially damaging the reputation of all involved in the construction process and the conditions under which this can lead to problems is demonstrated. Finally, some suggestions are given on how to reduce these problems.

2 Construction practice examples with uniformity of source materials

2.1 Wet shotcrete with alkali-free accelerator

The requirements for shotcrete, in addition to the applicable national standards and guidelines, are described very extensively in the contract. The contracts for requirements of the young shotcrete are often set by default according to the strength development of geology or the construction method. Usually for this purpose, the requirements in the guideline of the ÖBBT "shotcrete" [1] and the current valid national standards e.g. DIN 18551 [2] are used.

The compressive strength development of shotcrete, within the first 24 hours after the application, is divided into early strength classes.

In the contract, the other properties of the hardened shotcrete such as compressive strength, water penetration, sulfate resistance or the drainage blocking potential are defined. Before the initiation of the construction work in aptitude and initial testing, all these properties are required to show. For this purpose, experiments at different temperatures and dosages of accelerators must be performed. The required material properties are tested during the construction phase. The definition of inspection intervals for these mostly carried out in self-responsibility of the contractors conformity tests are also regulated in the contract. These tests are controlled by independent identity checks or third party control. With all these properties in place and making them part of the contract, one can then provide the client with a contract target.

2.1.1 Changes in the cement properties, fluctuations in C3A content

During a tunnel construction with multiple parallel tunnel drifts, a steady increase of the dosage of accelerators was necessary to achieve the contractually required early strength of the concrete. Two different accelerators were used.

The mixture had the same recipe, but it was produced in two different mixing plants. After the dosage, regardless of the type of production and accelerator that increased steadily upward, a root cause analysis was conducted (Figure 1).

Figure 1: Dosage amount of accelerator to achieve the J2 early strength of the concrete.

Firstly, it is the responsibility of the construction site to carry out the verification procedures, such as controlling the dosage quantities of the accelerator and the appropriation mixture that were used with the shotcrete machine. Furthermore, the temperature of the appropriation mixture and the accelerator were observed more frequently.

After these measures showed no signs of significant improvement, the suppliers of concrete, accelerators and the manufacturer of the cement were invited for a meeting to evaluate possible causes. It was, as one might expect, confirmed by all the suppliers and manufacturers that their own quality monitoring revealed no possible evidence of the changes observed in the shotcrete. Deeper investigations of the appropriation mixture, the cement and accelerators were commissioned by the construction site.

As Table 1 shows, it was determined on the basis of a cement analysis that the current total content of C3A, originally about 10, 6 %, declined to 7.4 % in about 9 months.

Table 1: Cement analysis (XRD) of three cement samples.

   

Sample 1dated13.01.2006

Sample 2dated16.10.2006

Sample 3spray tests22.11.2006

SiO2

21,5

21,8

22,1

A12o3

7,0

6,0

6,4

Fe2o3

2,6

2,9

2,8

CaO

59,2

60,1

60,2

MgO

4,1

3,6

3,9

SO3

3,3

3,3

3,3

K2O

0,92

0,9

0,94

Na2O

0,45

0,4

0,43

P2O3

0,11

0,09

0,09

TiO2

0,33

0,31

0,32

Cl

0,03

0,03

0,03

C3S

54,1

50,3

49,4

C2S

10,0

12,8

13,9

c-C3A

7,0

5,1

5,1

o-C3A

3,6

2,5

2,3

C4AF

4,6

6,7

6,6

MgO

3,0

2,4

2,3

K2SO4

0,9

1,0

1,1

calcit

2,1

2,0

2,1

gypsum

1,1

1,1

1,0

hemihydrite

2,0

1,6

1,5

anhydrite

2,3

2,5

2,3

blastfurnace slag

12,0

12,0

12,0

Looking at the chemical reaction of the alkali-free accelerator at the early stages of hydration of the cement, as it was described for example by Qi Xu [3], the change of the cement confirmed a possible cause.

As shown in Figure 2, the major reaction product between Portland cement and alkali-free accelerator are short fine prismatic ettringite crystals. These formations now occupy the cement clinker grains and interstices. By interlinking/gearing of the needlelike ettringite crystals, it is possible to obtain a first measurable strength. In addition to the reaction, a large amount of water is consumed. In this chemical reaction, a large proportion of the cement is bound in C3A. Figure 2 is an example of Qi Xu [3] that is used to show investigations on Portland cement. It is nicely observed that this reaction has achieved, within the first few minutes, a high percentage breakdown of the C3A content as a result of the reaction with the accelerator (Figure 3).

Figure 2: Schematic representation of the sequence of hydration of Portland cement with alkali-free accelerator [3].

Figure 3: Temporal reduction of the C3A content of an accelerated and non-accelerated portland cement [3].

The changes in the C3A content of the cement were mainly caused by changes in temperature conditions in the rotary kiln. By adapting the firing process, a quick remedy was made by the cement manufacturers.

The fresh concrete properties of the appropriation mixture and the hardened concrete properties of the shotcrete were hardly affected. The problem did not occur again up to the end of the construction.

2.1.2 Changes in cement properties and fluctuations of the sulfate carrier

In another case, fluctuating properties of the shotcrete were observed. Firstly, these showed an unsatisfactory spray pattern, during shotcreting the reinforcement. There were distinct blind spots behind the reinforcement due to the rapid reaction between the accelerator and concrete. They were so extremely strong that the shotcrete mostly remained on the reinforcement layers and one could literally reach behind the reinforcement (Figure 4).

Figure 4: Spray shadows due to rapid solidification of the shotcrete.

Due to the rapidly changing spray characteristics, it was not possible to produce a uniform spray pattern.

The second difficulty was the adherence of the required early strength class JII*. By reducing the amount of accelerator, an improved (but not satisfactory) spray pattern could be achieved. However, the early strengths (up till 3 hours afterwards) were insufficient and did not meet the contractual requirements.

In another case during the same period, the shotcrete was applied well. The reinforcement was imbedded completely and the requirements of the early strength in the period to 3 hours were obtained. However, the requirements of the early strength class JII* were below the requirements for the period between 12 and 24 hours.

The construction site was threatened by the Construction supervision services to stop the tunnel excavation operations if there are no significant quality improvements.

Also in this case, the fluctuating properties of the cement were the cause of the pronounced processing problems.

Based on the described and self-observed processing differences, suspicions of a possible alteration in the composition of the calcium sulfate in the cement were drawn quickly.

These changes can occur due to different temperature in the cement mill, when gypsum (CaSO4 * 2 H2O) is used. At higher temperatures in the mill, it can lead to a hemihydrate (CaSO4 * 0.5 H2O). The dissolution rate is significantly changed. Due to the fast hydration of the cement, the reaction rate will also be accelerated with the alkali-free accelerator to ettringite. Analysis of the composition of the calcium sulfate by means of X-ray fluorescence analysis of various cement samples from this period (Figure 5) confirmed these observations.

Figure 5: Changes in the composition of calcium sulfate of CEM II A-S 42,5 R within one year.

The fluctuations of the shotcrete properties can be explained by these results. The problem was solved by using a different type of cement that is used exclusively anhydrite. Anhydrite contains no bound water and therefore cannot be drained differently by variable mill temperatures. Therefore, the rate of dissolution remains unchanged. Again, these problems did not resurface.

2.1.3 Discussion on possible solutions in shotcrete

The examples show that an aimed quality-controlled process in the manufacturing process of shotcrete with alkali-free accelerator is currently not guaranteed in all cases. The customary division of labour process complicates not only technically, but also contracted aspects to finding solutions, because the cement and accelerator are not in the responsibility of the manufacturer of the product and they often have no direct contractual relationship. Both manufacturers produce according to the respective applicable material standards and mostly by their own more stringent quality requirements. They must also consider the cost of their own production process. The actual standard method for the production of shotcrete regulates a variety of method steps through analysis. The two direct reactants, cement and accelerator are still lacking sufficiently safe limits for the composition and their fluctuation for individual important material parameters. This is partly due to the history of the procedural standards with the alkaline accelerators used at that time, which were less sensitive in the system. But the increased quality requirements and shorter construction times require higher standards which have to be documented.

Finally, the question arises whether additional material standards for cement for wet shotcrete with tighter limits or ranges of variation of the individual parameters lead to a satisfactory solution for everyone. It will have to be clarified which parameters have to be regulated and how the fluctuation of these parameters should be set.

Also suitable test methods for practical implementation need to be developed that can verify these essential requirements in terms of acceptance testing on site quickly and meaningfully. For this purpose, a joint effort of the cement and admixture industries and the organizations involved in the standardization process, including the research at colleges and universities are needed. The test methods and their criteria should then be fixed in the standards.

2.2 Interaction between admixtures and cement in construction concrete

2.2.1 Case study

As already described, concrete for infrastructure constructions have generally high requirements in terms of durability and workability, this normally leads to a quite low water/cement ratio. Additionally the requirements of the construction itself lead to complications, such as long transport routes, long pumping distances, high or low temperatures and additionally the already high standards.

The combination of all requirements can now be met mostly thanks to the new plasticizing admixtures in combination with the correct cement and a broad recipe composition. For this purpose, usually at the beginning, a variety of recipes for different conditions, such as different environmental temperatures, different amounts of water, different conveyor lengths, have to be tested in advance. At the end of this extensive optimization and aptitude tests one or more recipes are defined for the production.

In almost all the examples at the construction sites, there were more or less severe problems because of fluctuation, especially in the fresh concrete properties, despite the effort with the production.

In many cases this leads to conveyor or installation problems due to demixing by after-liquefaction during the transport or when premature or delayed stiffening of the concrete takes place.

In the following example, the causes and the effects could be determined afterwards.

On a large tunnel construction site, for some time now a proven recipe for an inner leaf was used for the first time in a new formwork carrier.

Shortly after completion of the concreting, a strong tremor and kinking of some bracing cross studs took place. (Figures 6 and 7).

Figure 6: Installation of a formwork carrier.

Figure 7: Broken cross stud of the formwork carrier.

Construction defects of the formwork carrier or a too high concreting speed were first suspected to be the cause of damage, but investigations showed that this was not the case.

Due to abnormalities in other concrete recipes, it was suspected that the concrete recipe could be the cause. Sourced on reference cement samples this assumption was confirmed to be the cause of damage, because the setting behavior showed a delay of approximately 3.5 hours in the setting characteristics (Figures 8 and 9).

Figure 8: Workability of different concrete mixes with two different reference samples of cement.

Figure 9: Early strength development of concrete mixes with two different reference samples of cement.

A significant change that occurred within one day of the calcium sulfate caused this (Figure 10).

Figure 10: Cement analysis (XRD) of four cement samples taken on different dates of the same cement.

2.2.2 Discussion and Solutions

The example above shows how much the changes in the properties of concrete can be when the composition of the sulfate carrier changes. This phenomenon occurs mainly in combination with the newer plasticizers type on polycarboxylate ether (PCE). This is due to change in the mode of action over the traditional plasticizers. These traditional plasticizers like lingosulfonate (LS), polymerized melamine sulfonate (PMS) and polymerized naphthalene sulfonate (PNS), have a liquefying effect, because electrostatic repulsion forces act between the fine solid particles. However, the plasticizing effect and the consistency preservation of these admixtures are significantly lower as with the new PCE, so this will also often be used especially for concrete for infrastructure projects. Plasticizers sourced on PCE react relatively sensitively to changes in the solubility, the total amount of sulfate and changes in the C3A modifications. As demonstrated in this application, it is recommended when using PCE plasticizers to use cement with a high uniformity with regard to the solubility of the particular sulfate carrier and the composition of the C3A modification. This necessary increased uniformity is not guaranteed for many types of cement, considered over a longer period. Therefore, currently it still requires additional agreements with the cement manufacturer. For this purpose, it is recommended as early as possible to meet with the cement manufacturer to find solutions constructively.

This approach has been successfully practiced on a large construction site in Switzerland, after some of the problems described above have led to serious discussions. This pragmatic constructive way was now in retrospect a success for all sides, the cement manufacturers and the cement users.

Sourced on enhanced quality control of the cement, for the critical attributes of the composition and the solubility of the calcium sulfate and the C3A modification limits were defined. If these limits had been reached or just exceeded, before a delivery a report was made to the cement users. It was jointly decided how to proceed in each case.

Additionally it helped in the evaluation to do a regular rheological performance test of cement and admixtures. This additional information and a targeted silo allocation in concrete production led to cement partially used only for certain concrete recipes, and also that the cement was used as planned in the concrete recipes, but with initially increased self-monitoring.

Through these corresponding measures, consisting of amplified output control of the cement combined with a regulated and pragmatic mutual information policy problems with the fresh concrete, caused by interactions with the admixture were significantly reduced, almost excluded. This brought for the contractor, a more uniform production with a significant reduction of disturbances and the cement supplier could bring all his cement production in use without complaints.

This described solution, which led to a win-win situation due to the size and volume of cement delivery of the construction site for both, the cement manufacturers and the logistics, made the implementation easier than on construction sites which cannot use these boundary conditions.

Nevertheless, one can hold on to the basic principles that lead to improvements. These are first of all, an improved output control of the composition of the cement paired with a corresponding mutual information policy. The experience from other processes show that often improved or deepened quality control already leads to an improvement and uniformity of the production process and product quality.

Additional information about the cement composition and the single scattering widths should be specified in technical product data sheets. Automated customer information of relevant variation values would be desirable.

This enhanced quality control is especially important in regard to the increasingly complex cement production processes with multi-component systems, both in the burning process of clinker production as well as in cement production using other main constituents. It is for process and quality optimization indispensable. An increase in scientific efforts should be made to the cement and admixtures making interaction less sensitive, but without the loss of efficiency.

3 Summary

The case studies presented above should demonstrate why, from the perspective of a construction company, a uniformity of concrete properties over the entire construction period is necessary. Uniform properties of all constituents are essential. The uniform composition of the cement is important, because the cement reacts not only with water but also with the concrete admixtures. The interaction of these concrete admixtures with the cement very quickly leads to undesirable negative reactions, if changes in the composition of the cement occur. Clearly visible on the basis of the case examples, are false reactions due to temporal changes in the sulfate carrier composition or the C3A modification in combination with the concrete admixture. This can lead to significant changes in properties of the fresh concrete and depending on the construction process it may even lead to a stop of construction works. It should therefore be the target of all involved in the construction process, to avoid this situation associated with loss of reputation and increased cost and claims.

Individual solutions in the quality control plan specified bilateral property evidences or certificates of the compositions may be a solution in the short term. They are not for everyone a practical solution, because they do not consider the difficulties of the work-sharing process with various contractual partners, cement manufacturers, ready-mix concrete producers, contractors and the end customers. Therefore a practical solution requires a normative regulation of the uniformity of the cement properties for concrete monitoring classes 2 and 3 in Germany.

This will not always be possible without changes in cement production, but the historical development of cement and concrete production also shows that positive changes in the process adjustments for the common good have always been possible. Therefore it is up to all involved to make the future task solution-orientated and positive itself.

4 References

[1]   Guideline Sprayed Concrete; Austrian Society for Construction Technology

[2]   DIN 18551 Shotcrete; National rules for series DIN EN 14487 and rules for design of shotcrete constructions.