PURPOSES : Recently, the generation of industrial by-products has been increased owing to the increase in electrical power consumption. This experimental study investigated a special mortar development using outstanding benefits of porous structures in heavy oil fly ash (HOFA) and bottom ash (BA) to reduce heat transfer and weight of tunnel repair mortar. METHODS : Based on the concept of materials usable for this objective being porous and light, the physical and chemical properties of heavy oil fly ash and bottom ash were analyzed to determine the application possibility for tunnel repair mortar. In addition to satisfying this primary requirement, the research aimed at determining the relationships between the characteristics of porous structures and effectiveness of reducing weight and thermal conductivity. This study was undertaken on the use of bottom ash as fine aggregate and heavy oil ash as filler in mortar mix proportion. Four different levels of bottom ash (25%, 50%, 75%, 100%, and 5%), and 10%, 15%, and 20% of heavy oil fly ash were investigated to determine the proper replacement amount within the designed specification. According to the analytic results on the effectiveness of both by-products and chemical additives, the repair mortar with optimum mixture proportion was investigated using various tests including thermal conductivity and porosity. RESULTS : The use of porous by-products increased the demand for mixing water in obtaining the required flowability, but the compressive strength did not decrease significantly in proportion by adding an amount of bottom ash. Based on the results, bottom ash can be replaced with aggregate as much as 50%, but adding an amount of heavy oil ash is suggested as below 10% in formulation. CONCLUSIONS : The optimized repair mortar, which was produced by conclusive formulation, was evaluated as a high-performance material to repair tunnels with the effectiveness of porous and remarkable physical properties.

Since it was developed by Joseph Aspdin, cement has been a common construction materials up to the present time.However, there are trace constituents in cement clinker. One of the trace constituents included in cement clinker, chromium,has become prominent and highly noticed lately as a social issue both inside and outside of this country because it affects thehuman body negatively. The aim of the present study was to investigate the concentration of water-soluble hexavalent chromiumin cement clinker by using industrial by-products. For that reason, raw materials were prepared to add different SiO2 , Al2O3,and Fe2O3 sources. After the raw materials such as the limestone, the sand and the clay, iron ore was pulverized and mixed,and the raw meal was burnt at about 1450oC in a furnace with an oxidizing atmosphere. The part in the raw materials of theclinker was substituted with slag, sludge, etc. and this was used to manufacturing cement clinker. To investigate the water-soluble hexavalent chromium content in clinker, raw meal was prepared by changing the modulus, the type, and the contentof clinker materials and tested concentrations of hexavalent chromium in the clinkers. To determine Cr+6 formation of theclinker, tests were done with raw meals adding chromium by using different industrial by-products. Consequently because thechromium was to be included in the raw materials of the clinker, production of Portland cement clinker was included with thechromium. Also, the chromium was converted into hexavalent chromium in the burning process.

We investigated the effects of heavy metals in cement in the last 3 years and the amount of waste in the cement manufacturing process. The result shows that the average Cr6+ content in cement products is controlled at 10 mg/kg. Cu and Pb have lower detection tendency in white cement than in ordinary portland cement. In addition, heavy metals such as Cd show a certain level of detection regardless of the input wastes. Copper slag and phosphate gypsum are the main influencing factors on the heavy metals in cement products. In auxiliary fuels, plastics waste and wood waste are considered to affect heavy metals in cement products. Alternative raw materials are considered to be affected by the alternative raw materials managed as byproducts. In the case of supplementary fuels, auxiliary fuels managed as waste instead of auxiliary fuels managed as byproducts affect the heavy metals in cement. This study examined the input amount without considering the heavy metals in each waste. Therefore, the result may vary in different situations, and further research must be conducted to supplement the findings. However, if the heavy-metal contents in the waste are constant, it can be used as a reference material for the control of heavy metals in cement products.

In this study, we analyzed the content of five hazardous heavy metals (Pb, As, Hg, Cd, and Cu) in cement products distributed in Korea over the last five years. The types and amounts of waste inputted into a cement kiln or added as alternative fuels and secondary raw materials were investigated, and the correlation between heavy metal content and input waste were analyzed. The measured heavy metal content in cement products were 26.9-95.0 mg/kg for lead, 6.08-19.15 mg/kg for arsenic, 0.0339-0.2617 mg/kg for mercury, 2.937-4.392 mg/kg for cadmium, and 22.25-267.42 mg/kg for copper. In addition, based on correlation analysis results between the heavy metal content of cement products and added input wastes, major wastes that affected the heavy metal content among the 11 types of waste were iron, coal ash, waste tires, waste plaster, desulfurization gypsum, and waste synthetic resin.