According to media reports, two new cement varieties with low clinker content will be added to the European Union cement standard EN197-1 recently. In addition, as early as 2011, some cement industry research institutes in Germany proposed that the clinker content in Portland cement could be reduced to 50%, and continuous experimental research was carried out.
The original intention of adding new low-clinker cement varieties in the EU is very simple. According to the report, the cement industry is facing tremendous pressure to save high-quality fossil fuels and reduce CO2 emissions. At present, there is no new cementitious material that can completely replace Portland cement (Portland cement in China), so the development of low-clinker multi-component Portland cement is undoubtedly an important energy-saving and emission-reduction measure.
Interestingly, under the background that the European Union is carrying out research and developing low-clinker cement varieties to reduce clinker consumption, the opposite trend has emerged in China.
According to the No.2 Amendment to the National Standard GB175-2007 General Purpose Portland Cement approved and issued by the Standardization Administration of the People's Republic of China in December 2014, 32.5 composite Portland cement was cancelled from December 1, 2015 (32.5R early strength composite Portland cement was retained).
In addition, not long ago on December 9, the mobilization meeting to stop the production of 32.5 composite Portland cement was held in Beijing, and the domestic cement industry giants further confirmed their determination to eliminate 32.5 composite Portland cement. At the same time, according to Song Zhiping, chairman of China Building Materials Group, the revised draft of the standard to cancel 32.5R is also in the process of approval.
In the process of eliminating P.C32.5, Xinjiang is in the forefront of the country. Xinjiang eliminated 32.5 R composite Portland cement from July 1, 2016, and will cancel all 32.5 grade Portland cement from May 1, 2017.
The change of EU cement standards reflects their emphasis on energy saving and consumption reduction in the cement industry, as well as their responsibility for environmental carrying capacity. Does the domestic cement industry have too much energy and limestone to use up? Or is there not enough carbon dioxide emissions?
In fact, as far as the fine control technology of cement production is concerned, there is no advantage between China and foreign countries, and even many enterprises have higher energy consumption. In addition, based on the huge scale of cement production in China, the annual energy consumption is extremely huge. Based on the national clinker output of 1.335 billion tons in 2015, 150 million tons of coal will be consumed in the whole year. In addition, according to the current average international clinker CO2 emission coefficient of 853 kg/TCL, the clinker production alone brings 1.139 billion tons of carbon dioxide emissions every year.
From this point of view, the domestic cement industry is actually facing severe pressure of energy conservation and emission reduction, especially after the release of the opinions of the Central Committee of the Communist Party of China and the State Council on accelerating the construction of ecological civilization, the cement industry, as a major energy consumer and carbon emitter, has a great responsibility for energy conservation and emission reduction.
Of course, one of the important reasons for the cancellation of 32.5 cement in China is that we hope to improve the performance of concrete by using high-grade cement, which is actually a false proposition.
On the one hand, the performance of concrete is restricted by various factors, such as the quality of sand and stone, the performance of admixtures, the construction environment, the later maintenance and so on. A single enhancement of cement strength can not fundamentally solve the problem; On the other hand, different grades of cement have different functions in actual production and application, and the use of low-grade cement has more advantages and environmental protection in the case of plastering without too high requirements for strength.
For example, in the European Union, slag and pozzolan are not called cement additives or admixtures, but are collectively referred to as the main components of cement (content ≥ 5%), because these materials have their own advantages in improving and regulating the performance of cement and concrete. Granulated blast furnace slag can improve the late strength of cement and the compactness of concrete structure, but the early strength is low. The addition of finely ground limestone powder can improve the early strength of this kind of cement and prevent the bleeding of concrete, especially when coarse sand and PCE based water reducer are used.
Therefore, from the point of view of the update of EU standards, multi-component and less clinker is one of the development directions of Portland cement. The content and particle distribution of these components should be adjusted according to the performance requirements of cement and concrete, and cement plants should produce and supply more special cement.
Of course, at present, there are many voices of doubt about the cancellation of P.C32.5 cement in China, and there are many reasons. Here, the author will not repeat them one by one, but simply deal with them on their own merits. Under the background of paying equal attention to the obligation and responsibility of energy saving and emission reduction of domestic cement, is it really reasonable to cancel P.C32.5 cement and increase clinker consumption to resolve overcapacity? Is there any requirement for the construction of ecological civilization? Instead of alleviating overcapacity at the expense of resources and environment, it is better to put capacity removal into practice and gradually reduce the scale of industry capacity.
浙公网安备33010802003254号