• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.34 no.4
• /
• pp.1095-1104
• /
• 2014

This paper presents the results of experimental work on both strength characteristics and durability of concrete or mortar having 50% ground granulate blastfurnace slag(GBS) with different fineness levels (4,450, 6,000 and $8,000cm^2/g$). Compressive and split tensile strength test results indicated that the concrete with a higher fineness level of GBS exhibited a better strength development due to the acceleration of latent hydraulic property at the later curing stage compared with ordinary portland cement concrete. Meanwhile, it was found that a higher fineness level of GBS showed some negative effects on the resistance against freezing-thawing action. However, incorporation of GBS to concrete, irrespective of fineness levels, significantly enhanced the chloride ions penetration resistance. The resistance against sulfate attack of mortar with GBS was greatly dependent on the attacking sources from sulfate environments.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.12 no.1
• /
• pp.94-101
• /
• 2024

In this paper, the performance of air pollution reduction by coating the photocatalyst solution on the mortar surface was analyzed to ensure the possibility of applying the photocatalyst to structures with a large specific surface area. The photocatalytic concentrations of the coating solution were set to 1.5 % and 3.0 %, and the types of binders were considered as experimental variables, such as ultra-high performance concrete (UHPC), ordinary portland cement (OPC), and blast furnace slag. As the photocatalyst concentration increases, the air pollution reduction performance increases. In addition, as a result of the air pollution reduction performance, the NO_x concentration reduction rate was the highest for UHPC, and the air pollution reduction performance increased as the blast furnace slag was replaced. Therefore, the amount of TiO₂ remaining on the surface varies depending on the density of the tissue due to the difference in particles caused by the difference in the amount of TiO₂ remaining on the surface.

• Journal of the Korean Ceramic Society
• /
• v.28 no.11
• /
• pp.917-925
• /
• 1991

For the present experiment five Portland cement mortars are in order: mortars with two different water/ cement ratios (W/C=0.45 and 0.50, each having no chemical additive), and those with an additive such as superplasticizer, air-entraining agent or water-repelling agent. We fix the W/C ratio of mortars having additive so that their pastes can yield the same workability as that of the cement mortar of W/C=0.50 with no additive. It is shown that the freeze-thaw resistivity depends heavily on the characteristic of wide pores. Despite a good deal of wide pores, the air-entrained specimen shows a good freeze-thaw resistivity due to appropriate air-pores. And also the specimen with water-repelling agent, which proves to cause the microstructure to become hydrophobic, make good resistance to freeze-thaw cycles in spite of its high wide-porosity. Our suggestion is that the freeze-thaw durability of Portland cement mortar/concrete can be more effectively enhanced by using air-entraining agent or water-repelling agent, and simutaneously by taking proper measures against foaming and/or the increased tendency of wide-pore building due to additive.

• Journal of the Korea Institute of Building Construction
• /
• v.18 no.5
• /
• pp.429-437
• /
• 2018

The aim of the research is to analyze a feasibility of rapid evaluation method for cement fineness by the relation analysis between density measurement using hydrometer and fineness of ordinary Portland cement. Additionally, based on the commercially available cement product, relation between a series of fundamental properties of cement mortar and fineness of cement powder was analyzed. As an experimental result, the actually measured fineness value of cement powder showed a good correlation with the fineness value obtained by hydrometer while there was poor correlation with the fineness value on specification. Especially, the density measurement in three minutes showed the closest relation with cement powder fineness, thus rapid quality evaluation of cement powder can be possible by using the regression equation obtained from the three minutes density measurement. Additionally, there was a high relation between cement powder fineness with a fundamental properties of the cement mortar such as fluidity, air content, setting time, and strength development.

• Journal of the Korea Concrete Institute
• /
• v.26 no.2
• /
• pp.117-124
• /
• 2014

Globally, there are environmental problems due to greenhouse gas emissions. $CO_2$ emissions rate of the cement industry is very high, but the continued demand of cement is needed in the future. In this study, in order to reduce the environmental impact of $CO_2$ emissions from cement production. The experiments were carried out for the development of non-sintered cement (have not undergone firing burning) by granulated ground blast furnace slag. In order to compare the characteristics by curing, an experiment was conducted by changing the curing conditions such as atmospheric steam curing, observe the mechanical properties for the measurement of flexural compressive strength by mortar, observe the chemical properties such as acid resistance, $Cl^-$ penetrate resistance and analyzed the mechanism of hydration by XRD, SEM experiments. From the experimental results, as compared with portland cement usually confirm the mechanical and chemical properties excellent, it is expected be possible to apply to the undersea, underwater and underground structures that require superior durability. In addition, based on the excellent compressive strength by steam curing, it is expected to be possible to utilize as a cement replacement material in the secondary product of concrete. In the future, to solve the problem through continued research, it will be expected to reduce the effect of environmental load and to be excellent economics.

• Journal of the Korea Concrete Institute
• /
• v.27 no.3
• /
• pp.237-244
• /
• 2015

Entering the 20th century since the industrial revolution, the cement has been widely used in the field of construction and civil engineering due to the remarkable development of construction industry. However, result from that development, each kind of industrial by-products and waste and the carbon dioxide generated in the process of cement production cause air pollution and environmental damage so earth is getting sick now slowly. Therefore, we have to recognize importance about this. It means that the time taking specific and long-term measures have come. In this research paper, as substitution of the cement generating environmental pollution, we investigate the hydration reaction of non-Sintered Cement mortar mixed with GBFS, active stimulant of alkaline and sulphate series by using SEM and XRD, mechanical and chemical properties according to the curing method. As a result of this experiment, NSC realized outstanding strength for water curing and steam curing. It means that it has a good possibility as substitution of cement. From now on, it can be used for structure satisfying specific standard. We expect to find a substitution of outstanding cement by progressing continuous research making the best use of pros and cons according to the curing method.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.2
• /
• pp.86-93
• /
• 2020

Shotcrete concrete is generally used in the form of ready-mixed concrete products using type I ordinary portland cement(hereinafter referred to as OPC) and about 5% of accelerator mixed separately in the field. In this study, we tested the effect of addition of slag powder(SP) and limestone powder(LSP) on a penetration resistance, compressive strength of binder for shotcrete using calcium aluminate type accerlerator. And we analysed hydrates and pore structure effects on mortar performance. In the future, it is expected to be useful for manufacturing optimized composite cement as a binder for shotcrete.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.6 no.1
• /
• pp.111-119
• /
• 2011

Recently, urban redevelopment programs and expansion of social infrastructure have caused massive amounts of construction waste in construction fields, and the mounds of it keep increasing every year. The disposal of construction waste is emerging as a national and social issue and the recycled powder generated by the treatment process of waste concrete is all being abolished or buried. Therefore, the purpose of this study is to utilize waste sludge generated by the wet-type treatment process of waste concrete as materials(binder, filler) for cement composite. This study evaluates physical and mechanical properties of mortar using recycled powder according to heating temperature, contents and applications. As a result of the chemical analysis, recycled powder is composed mainly of CaO and $SiO_2$, and that it is even lower in the content of CaO than OPC. The charateristics of mortar using recycled powder, according to drying and heating temperature, shows that as the heating temperature increases, flow decreases. Also, compressive strength and porosity of mortar using recycled powder was superior when heating temperature was $600^{\circ}C$. Thus, it is revealed that an effective development of recycled powder is possible since the binder by cement composite recovers a hydraulic property during heating at $600^{\circ}C$.

• Journal of the Korea Institute of Building Construction
• /
• v.16 no.1
• /
• pp.59-65
• /
• 2016

This study examined the compressive strength development and pH values of alpha-calcium sulfate hemihydrate(${\alpha}-CH$)-based binders developed for vegetation concrete with neutral pH between 6~7. Considering cost down and strength enhancement of the prepared binders, the ${\alpha}-CH$ was partially replaced by ground granulated blast furnace slag(GGBS), fly ash(FA), or ordinary Portland cement(OPC) by 25% and 50%. The compressive strength of mortars using 100% ${\alpha}-CH$ was 50% lower than that of 100% OPC mortars. With the increase of the replacement level of GGBS or FA, the compressive strength of ${\alpha}-CH$-based mortars tended to decrease, whereas the pH values were maintained to be 6.5~7.5. The main hydration products of ${\alpha}-CH$-based binders with GGBS or FA were a gypsum($CaSO_4$), whereas portlandite($Ca(OH)_2$) was not observed in such binders. Meanwhile, the pH values of ${\alpha}-CH$-based binders with OPC exceeded 11.5 due to the formation of $Ca(OH)_2$ phase as a hydration product. From the thermogravimetric analysis, the amount of $Ca(OH)_2$ in ${\alpha}-CH$-based binders with OPC was evaluated to be approximately 10% of the cement content.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.1A
• /
• pp.75-84
• /
• 2009

The present study assesses the chloride threshold level for corrosion of steel in concrete by examining the properties of four different binders used for blended concrete in terms of chloride binding, buffering of cement matrix to a pH fall and the corrosion behaviour. As binders, ordinary Portland cement (OPC), 30% pulverised fuel ash (PFA), 60% ground granulated blast furnace slag (GGBS) and 10% silica fume (SF) were used in a concrete mix. Testing for chloride binding was carried out using the water extraction method, the buffering of cement matrix was assessed by measuring the resistance to an artificial acidification of nitric acid, and the corrosion rate of steel in mortar with chlorides in cast was measured at 28 days using an anodic polarisation technique. Results show that the chloride binding capacity was much affected by $C_{3}A$ content and physical adsorption, and its order was 60% GGBS>30% PFA>OPC>10% SF. The buffering of cement matrix to a pH fall was varied with binder type and given values of the pH. From the result of corrosion test, it was found that the chloride threshold ranged 1.03, 0.65, 0.45 and 0.98% by weight of cement for OPC, 30% PFA, 60% GGBS and 10% SF respectively, assuming that corrosion starts at the corrosion rate of $0.1-0.2{\mu}A/cm^{2}$. The mole ratio of [$Cl^{-}$]:[$H^{+}$], as a new presentation of the chloride threshold, indicated the value of 0.008-0.009, irrespective of binder, which would be indicative of the inhibitive characteristic of binder.