• Korean Journal of Environmental Agriculture
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• v.13 no.2
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• pp.223-230
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• 1994

A practical study on a drying and fermentation system equipped with a stirring machine operated mechanically, of pig manure was conducted to prove the efficiency of and practicability to an ordinary pig farm. The type of the drying bed was a round-shaped (r=3m) concrete structure and the stirring machine was adopted to stir and transfer dried pig manure to the fermentation tank. The dried pig manure was put into a fermentation tank ($V=18m^3$), which was aerated from pipe lines installed at the bottom. While water content of pig manure passing through a drying bed was remarkably reduced than before drying, the drying efficiency of this system decreased in winter. However, the temperature of pig manure piled up in the fermentation room in winter reached over $60^{\circ}C$ and excess water of pig manure was removed during the fermentation process. The reduction rate of water content of pig manure, to which dried pig manure was added as bulking material on the drying bed, was 52.1%, but when dried without bulking material it was only 19.7%. Although the content of $P_2O_5$ of dried pig manure was slightly higher than that of fresh pig manure, progressive changes in chemical composition between fresh and dried pig manure made no great difference. Among the contents of minerals of fresh and dried pig manure, CaO was the highest and the rest were in the decreasing order of $K_2O$, MgO, and $Na_2O$. Population density of E. coli and Streptococci of dried pig manure was reduced by 142 and 236 times that of fresh pig manure, respectively. The installation cost of this drying and fermentation system was 4,185,630 won (approximately 5,232 US $) and operating cost per year was 190,000 won (237.5US $) on the basis of self-labor condition.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.2
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• pp.235-244
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• 2020

This study conducted a series of studies to offer a novel method of using CBS-dust that produced as by-product in the manufacture of cement. Four different contents of BS and CBS-dust were adopted for test parameters of this study. Mortar with 50% of W/B was fabricated. First, in the case of the fresh mortar, the flow decreased as the CBS-dust replacement rate increased, but the binder composition ratio BS 45% and 65% showed higher fl ow than Pl ain when repl acing CBS-dust 5%. In the case of air content, overall, the tendency was proportional to the CBS-dust replacement rate, and chloride tended to exceed the reference value at all replacement rates except for the CBS-dust 0% replacement. The compressive strength of the hardened mortar shows the resul t that the strength is improved when the CBS-dust is repl aced by 5% to 10%, and the CSH gel and structure formation is confirmed by microstructure analysis through the hydration reaction when the CBS-dust is replaced. Therefore, for a given condition CBS-dust is used as a early-strength admixture in a concrete secondary product that uses a large amount of admixture without reinforcing bars it can be an effective method for enhancing the strength of concrete as an alkali activator.

• Computers and Concrete
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• v.17 no.3
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• pp.423-433
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• 2016

After the industrial of steelmaking by-products are processed properly, they can be used in civil engineering, not only as a substitute for natural resources and to reduce costs, but also to provide environmental protection. This study used different amounts (10%, 20%, 30%, 40%,and 50%) of desulphurization slag to replace natural fine aggregates in ready-mixed soil materials, and tested the physical and fresh properties (slump, slump flow, tube flow, initial setting time, and bleeding) and hardened properties (compressive strength, ball drop, ultrasonic pulse velocity) of the materials. The variations between the performances of the materials with different mix proportions were discussed. When desulphurization slag is used in RMSM, the workability can be enhanced obviously significantly. When the replacement of desulphurization slag is 50%, the slump flow is increased by 110mm compared with the control group, and the initial setting time increases as the replacement increases, because of bleeding. When the replacement is 10% and 20%, the compressive strength at various ages is higher than that of the control group. When the replacement is 10%, the compressive strength at 7 days is higher than that of the control group by 60%, and the ultrasonic pulse velocity is proportional to the compressive strength, which increases with age and decrease as the replacement increases. An appropriate replacement can effectively accelerate construction, and allow projects to be finished ahead of schedule; therefore, an appropriate replacement, is applicable for ready-mixed soil materials.

• Structural Engineering and Mechanics
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• v.49 no.4
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• pp.491-498
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• 2014

During the past years, the protection of the environment has become a major concern out passing the state frontiers to reach a planetary dimension. Depository waste sites have become a serious problem in terms of their locations and costs. On the other hand, the construction industry has a leading place in terms of quantities of waste produced from the start to the end of each construction site, by the large amounts of raw materials used and their respective consequences on the environment. The recycling of quarry wastes products, of demolished concrete, bricks and large quantities of waste resulting from the transformation of marble blocks can provide ideal solutions and advantages for the preservation of the environment, to become a supplementary source of aggregates. The main purpose of this study is to show technically the possibility of recuperating the aggregates of marble wastes as a partial substitute or total in the mortars. The aggregates used in this study is a sand of marble wastes (excess loads of sand exposed to bad weather conditions) of the quarry derived from Fil-fila marble (Skikda, east of Algeria). To achieve this work, we have studied the effect of sand substitution of marble wastes in the mortar with rates of (25, 50, 75, 100%); comparing the results obtained with reference samples (0%), the properties when the samples are fresh, and the mechanical performances of mortars at solid state (loss and gain of weight, dimensional variations). The introduction of recycled sand in the mortars gives good results and can be used as granulates.

• Computers and Concrete
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• v.9 no.6
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• pp.427-437
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• 2012

This article presents the effect of replacement fly ash (FA) with diatomite (DE) on the properties of geopolymer mortars. DE was used to partially replace FA at the levels of 0, 60, 80 and 100% by weight of binder. Sodium silicate ($Na_2SiO_3$) and sodium hydroxide (NaOH) solutions were used as the liquid portion in the mixture in order to activate the geopolymerization. The NaOH concentrations of 15M, $Na_2SiO_3$/NaOH ratios of 1.5 by weight, and the alkaline liquid/binder (LB) ratios by weight of 0.40, 0.50, 0.60 and 0.70 were used. The curing at temperature of $75^{\circ}C$ for 24 h was used to accelerate the geopolymerization. The flows of all fresh geopolymer mortars were tested. The compressive strengths and the stress-strain characteristics of the mortar at the age of 7 days, and the unit weights were also tested. The results revealed that the use of DE to replace part of FA as source material in making geopolymer mortars resulted in the increased in the workability, and strain capacity of mortar specimens and in the reductions in the unit weights and compressive strengths. The strain capacity of the mortar increased from 0.0028 to 0.0150 with the increase in the DE replacement levels from 0 to 100%. The mixes with 15M NaOH, $Na_2SiO_3$/NaOH of 1.5, LB ratio of 0.50, and using $75^{\circ}C$ curing temperature showed 7 days compressive strengths 22.0-81.0 MPa which are in the range of normal to high strength mortars.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.78-83
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• 2010

This paper presents the feasibility of incorporating ultrafine particles collected in the separator bag filter (separator bag filter cement, SBFC) during the cement manufacturing process as an substitution material for cement. SBFC does not require additional processes needed in the existing processes to manufacture high early strength cement such as modifying mineral components and adjusting the firing temperature. Moreover, it can also solve the issue of efficiency decrease resulted from the increase of the grinding time applied in the existing process of manufacturing microcement. Therefore, this research has examined the characteristics of SBFC and fresh properties and mechanical properties after making paste and mortar using SBFC in order to use SBFC as a material to gain early strength of concrete. For results, analyzing the chemical composition and physical properties of SBFC, its blaine value was $6,953cm^3/g$, about double than that of OPC, but its chemical composition showed no significant difference. According to the result of the paste and mortar examination, the paste and mortar mixed with SBFC showed a lower flowability, earlier setting time, and higher compressive strength than that with OPC. The result of microstructure analysis of paste, the paste mixed with SBFC indicated about 9% lower internal porosity at an early age than that of OPC. The compressive strength and flexural strength of mortar were higher in the order of SBFC ratio of 100, 50 and 0% SBFC.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.4
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• pp.474-480
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• 2017

In this study, the evolution of electrical impedance of electric nodes was investigated to determine the setting time of cement paste using the electrical impedance spectroscopy method. The electric nodes were embedded in fresh cement paste and the electrical impedance signatures were continuously monitored. Vicat needle test and semi-adiabatic calorimetry test were also conducted to validate the electrical impedance spectroscopy method. During hydration period of cement paste, the magnitude of conductance gradually increased, and then started to decrease rapidly at a first certain time. After that, the magnitude of conductance gradually decreased at a second certain time. The times of turning point in the curves of magnitude of conductance seem to be related with the setting time by Vicat needle test. Also, the setting times by the electrical impedance spectroscopy method are well posed within the setting period estimated by the semi-adiabatic calorimetry test. Based on the results, it can be concluded that the setting time of cement paste can be effectively monitored through the electrical impedance spectroscopy method.

• Computers and Concrete
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• v.17 no.6
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• pp.787-799
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• 2016

Climate anomalies in recent years, numerous natural disasters caused by landslides and a large amount of entrained sands and stones in Taiwan have created significant disasters and greater difficulties in subsequent reconstruction. How to respond to these problems efficaciously is an important issue. In this study, the sands and stones were doped with recycled materials (waste LCD glass sand, slag powder), and material was mixed for recycled ready-mixed soil. The study is based on security and economic principles, using flowability test to determine the water-binder ratio (W/B=2.4, 2.6, and 2.8), a fixed soil: sand ratio of 6:4 and a soil: sand: glass ratio of 6:2:2 as fine aggregate. Slag (at concentrations of 0%, 20%, and 40%) replaced the cement. The following tests were conducted: flowability, initial setting time, unit weight, drop-weight and compressive strength. The results show that the slump values are 220 -290 mm, the slump flow values are 460 -1030 mm, and the tube flow values are 240-590 mm, all conforming to the objectives of the design. The initial setting times are 945-1695 min. The unit weight deviations are 0.1-0.6%. The three groups of mixtures conform to the specification, being below 7.6 cm in the drop-weight test. In the compressive strength test, the water-binder ratios for 2.4 are optimal ($13.78-17.84kgf/cm^2$). The results show that Recycled ready-mixed soil materials (RRMSM) possesses excellent flowability. The other properties, applied to backfill engineering, can effectively save costs and are conducive to environmental protection.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.5
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• pp.23-29
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• 2019

This study applies to the surface modification technique by coating the surface of aggregates using the modified paste such as cementitious materials in order to develop completely recycling technology of coarse aggregate. In this case, coating thickness of modified aggregate can be considered that the decision is dependent on the viscosity and tenacity of modified paste. In this study identify the flow properties of the fresh modified paste, and examined for the coating thickness of modified aggregate. As a result, it was possible to design a quantitative coating thickness of modified paste assuming that a modified paste to a Bingham Fluid and consider by excess paste theory and rheology constant (yield value). Accordingly, it is considered that the quantitative mix design of concrete using by surface modified aggregates will be possible.

• Advances in concrete construction
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• v.13 no.1
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• pp.71-81
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• 2022

Aluminosilicate materials as precursors are heterogenous in nature, consisting of inert and partially reactive portion, and have varying proportions depending upon source materials. It is essential to assess the reactivity of precursor prior to synthesize geopolymers. Moreover, reactivity may act as decisive factor for setting molar concentration of NaOH, curing temperature and setting proportion of different precursors. In this experimental work, the reactivities of two precursors, low calcium (fly ash (FA)) and high calcium (ground granulated blast furnace slag (GGBS)), were assessed through the dissolution of aluminosilicate at (i) three molar concentrations (8, 12, and 16 M) of NaOH solution, (ii) 6 to 24 h dissolution time, and (iii) 20-100℃. Based on paratermeters influencing the reactivity, different proportions of ternary binders (two precursors and ordinary cement) were activated by the combined NaOH and Na2SiO3 solutions with two alkaline activators to precursor ratios, to synthesize the geopolymer. Reactivity results revealed that GGBS was 20-30% more reactive than FA at 20℃, at all three molar concentrations, but its reactivity decreased by 32-46% with increasing temperature due to the high calcium content. Setting time of geopolymer paste was reduced by adding GGBS due to its fast reactivity. Both GGBS and cement promoted the formation of all types of gels (i.e., C-S-H, C-A-S-H, and N-A-S-H). As a result, it was found that a specified mixing proportion could be used to improve the compressive strength over 30 MPa at both the ambient and hot curing conditions.