Since the United Nations Framework Convention on Climate Change(UNFCCC) to prevent global warming was adopted in Rio de Janeiro, Brazil in 1992, the world has prepared on how to cope with global warming which was highlighted as a mankind issue. The Kyoto Protocol that was adopted in Kyoto, Japan in ...
Since the United Nations Framework Convention on Climate Change(UNFCCC) to prevent global warming was adopted in Rio de Janeiro, Brazil in 1992, the world has prepared on how to cope with global warming which was highlighted as a mankind issue. The Kyoto Protocol that was adopted in Kyoto, Japan in 1997 specifies that advanced countries should reduce the discharge of greenhouse gas(GHG) by 5.2% every year comparing with the year 1990 over 5 years from the year 2008. Accordingly, GHG reduction will be highlighted as the most pending question in the cement industry in future because the production of Portland cement not only consumes limestone, clay, coal, and electricity, but also release waste gases such as CO_(2), SO_(3), and NO_(x), which can contribute to the greenhouse effect and acid rain. However, the world's cement demand is anticipated to increase about 2.55.8% every year until the fist half of the 21st century. To meet the increase of cement demand and simultaneously comply with the Kyoto Protocol, cement that gives less carbon dioxide(CO_(2)) discharge should be urgently developed. If cement can be manufactured with industrial byproducts such as granulated blast furnace slag(GBFS), phosphogypsum(PG), and waste lime(WL) instead of clinker as its counterproposal, there would be many advantages including maximum use of these industrial byproducts for high value-added resources, conservation of natural resources and energy by omitting the use of clinker, minimized environmental pollution problems caused by CO_(2) discharge, and reduction of the production cost. GBFS is a byproduct generated from the iron manufacture process. It does not become hydrated upon contact with water, but it tends to be hydrated and hardened when adding activators such as alkali or sulfate. In Korea, 25 million tons of PG and 4 million tons of WL have been accumulated as wastes. Their disposal has become a serious social issue. This study aims to manufacture non-sintering cement(NSC) by adding PG and WL to GBFS as sulfate and alkali activators. This study also investigates the basic physical properties and quality of NSC, and evaluates its reusing possibility as construction material. As a measure to save resources and energy and reuse industrial byproducts in the cement industry, this study evaluated the basic properties of NSC cement using industrial byproducts, focusing on its hydration, strength and durability. The results are as follows : 1) GBFS was affected by SO_(4)^(2-) in waste PGand stimuli under wet condition, left slag components, created Ettringite and CSH and AH_(3) gels, and eventually started being hydrated. These hydrated creations formed dense structures like CSH based on Ettringite and contributed in allowing the mortar to reveal high strength. 2) If the initial strength of NSC was not considered when manufacturing NSC, the proper use of waste gypsum(dihydrate gypsum) and WL, which were both industrial byproducts and had simple pre-processing, would reduce the mixing amount of GBFS fine powder and would also result in the manufacture of high value-added cement. 3) The compressive strength, flexural strength, and tensile strength of the concrete which used NSC increase linearly with progress of a curing age, and the increase tendencies are alike. At curing age of 3day, the strengths of the concrete which used NSC are lower than the strengths of the concrete which used OPC. However, From seven day or later, the strengths of the concrete using NSC appeared more highly than those of the concrete which used OPC. Although the increase in the strengths of concrete using OPC becomes slow from curing age of 28 day or later, the strengths of concrete using NSC tend to increase continuously also after curing age of 28 day. 4) The result of experiment of pore structure properties, showed no considerable difference for total pore volume by cement mixing ratio but shows a large distinction in distribution of pore diameter. On the whole, pore-diameter of paste of NSC show that occupation ratio of pore diameter below 100mm is larger and is smaller than OPC at pore diameter of over 100nm. 5) Since the heat of hydration of NSC is low, it can be utilized for mass concrete and high-strength concrete. When moisture is fully supplied at the first stage curing age, there is effect which carries out abundant generation of the ettringite which is an expansion nature mineral, and compensates for contraction with a chemical free stress concept. 6) Since the hardened object using NSC has very precise internal formation, air transmissivity and its chloride ion penetration are very low. 7) The hardened object using NSC does not generate Ca(OH)2 because NSC is very excellent in acid resistance and seawater resistance, can be utilized as low-alkali cement. 8) Carbonation is the largest problem when using NSC for reinforced cement concrete structure, therefore the use of NSC of such as an underwater concrete structure with the low concentration of carbon dioxide), an underground structure, etc. are recommended. Moreover, when applying to a ground structure, it is thought that carbonation preventive measures, for example a suitable surface treatment, are required. 9) Since the capability of fixing a chloride and a heavy metal is excellent, NSC is utilizable as solidification material of waste(waste which contained especially Pb so much). 10) NSC which discovers high strength and high durability is utilizable to manufactures of the structure which requires durability, or the secondary concrete product, etc. as alternative material of OPC. since NSC does not have sintering process in manufacture process and it can come out and can manufacture by distribution and Mixture process, manufacture expense is very low and the initial cost of equipment is also very economical. Since distribution and Mixture process can be simplified and necessary materials also use an industrial by-product instead of limestone with the main material, large cost reduction effect is expected.
Since the United Nations Framework Convention on Climate Change(UNFCCC) to prevent global warming was adopted in Rio de Janeiro, Brazil in 1992, the world has prepared on how to cope with global warming which was highlighted as a mankind issue. The Kyoto Protocol that was adopted in Kyoto, Japan in 1997 specifies that advanced countries should reduce the discharge of greenhouse gas(GHG) by 5.2% every year comparing with the year 1990 over 5 years from the year 2008. Accordingly, GHG reduction will be highlighted as the most pending question in the cement industry in future because the production of Portland cement not only consumes limestone, clay, coal, and electricity, but also release waste gases such as CO_(2), SO_(3), and NO_(x), which can contribute to the greenhouse effect and acid rain. However, the world's cement demand is anticipated to increase about 2.55.8% every year until the fist half of the 21st century. To meet the increase of cement demand and simultaneously comply with the Kyoto Protocol, cement that gives less carbon dioxide(CO_(2)) discharge should be urgently developed. If cement can be manufactured with industrial byproducts such as granulated blast furnace slag(GBFS), phosphogypsum(PG), and waste lime(WL) instead of clinker as its counterproposal, there would be many advantages including maximum use of these industrial byproducts for high value-added resources, conservation of natural resources and energy by omitting the use of clinker, minimized environmental pollution problems caused by CO_(2) discharge, and reduction of the production cost. GBFS is a byproduct generated from the iron manufacture process. It does not become hydrated upon contact with water, but it tends to be hydrated and hardened when adding activators such as alkali or sulfate. In Korea, 25 million tons of PG and 4 million tons of WL have been accumulated as wastes. Their disposal has become a serious social issue. This study aims to manufacture non-sintering cement(NSC) by adding PG and WL to GBFS as sulfate and alkali activators. This study also investigates the basic physical properties and quality of NSC, and evaluates its reusing possibility as construction material. As a measure to save resources and energy and reuse industrial byproducts in the cement industry, this study evaluated the basic properties of NSC cement using industrial byproducts, focusing on its hydration, strength and durability. The results are as follows : 1) GBFS was affected by SO_(4)^(2-) in waste PGand stimuli under wet condition, left slag components, created Ettringite and CSH and AH_(3) gels, and eventually started being hydrated. These hydrated creations formed dense structures like CSH based on Ettringite and contributed in allowing the mortar to reveal high strength. 2) If the initial strength of NSC was not considered when manufacturing NSC, the proper use of waste gypsum(dihydrate gypsum) and WL, which were both industrial byproducts and had simple pre-processing, would reduce the mixing amount of GBFS fine powder and would also result in the manufacture of high value-added cement. 3) The compressive strength, flexural strength, and tensile strength of the concrete which used NSC increase linearly with progress of a curing age, and the increase tendencies are alike. At curing age of 3day, the strengths of the concrete which used NSC are lower than the strengths of the concrete which used OPC. However, From seven day or later, the strengths of the concrete using NSC appeared more highly than those of the concrete which used OPC. Although the increase in the strengths of concrete using OPC becomes slow from curing age of 28 day or later, the strengths of concrete using NSC tend to increase continuously also after curing age of 28 day. 4) The result of experiment of pore structure properties, showed no considerable difference for total pore volume by cement mixing ratio but shows a large distinction in distribution of pore diameter. On the whole, pore-diameter of paste of NSC show that occupation ratio of pore diameter below 100mm is larger and is smaller than OPC at pore diameter of over 100nm. 5) Since the heat of hydration of NSC is low, it can be utilized for mass concrete and high-strength concrete. When moisture is fully supplied at the first stage curing age, there is effect which carries out abundant generation of the ettringite which is an expansion nature mineral, and compensates for contraction with a chemical free stress concept. 6) Since the hardened object using NSC has very precise internal formation, air transmissivity and its chloride ion penetration are very low. 7) The hardened object using NSC does not generate Ca(OH)2 because NSC is very excellent in acid resistance and seawater resistance, can be utilized as low-alkali cement. 8) Carbonation is the largest problem when using NSC for reinforced cement concrete structure, therefore the use of NSC of such as an underwater concrete structure with the low concentration of carbon dioxide), an underground structure, etc. are recommended. Moreover, when applying to a ground structure, it is thought that carbonation preventive measures, for example a suitable surface treatment, are required. 9) Since the capability of fixing a chloride and a heavy metal is excellent, NSC is utilizable as solidification material of waste(waste which contained especially Pb so much). 10) NSC which discovers high strength and high durability is utilizable to manufactures of the structure which requires durability, or the secondary concrete product, etc. as alternative material of OPC. since NSC does not have sintering process in manufacture process and it can come out and can manufacture by distribution and Mixture process, manufacture expense is very low and the initial cost of equipment is also very economical. Since distribution and Mixture process can be simplified and necessary materials also use an industrial by-product instead of limestone with the main material, large cost reduction effect is expected.
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