• Advances in concrete construction
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• v.11 no.5
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• pp.419-428
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• 2021

The pH of cement-based materials (CBMs) is an important factor for their durability, sustainability, and long service life. Currently, the use of supplementary cementitious materials (SCMs) is becoming mandatory due to economic, environmental, and sustainable issues. There is a decreasing trend in pH of CBMs due to incorporation of SCMs. The determination of numerical values of pH is very important for various low and high volume SCMs blended cement mortars for the better understanding of different defects and durability issues during their service life. In addition, the effect of cement hydration and pozzolanic reaction of SCMs on the pH should be determined at initial and later ages. In this study, the effect of low and high-volume fly ash (FA) and ground granulated ballast furnace slag (GGBFS) cement mortars in different curing conditions on their pH values has been determined. Thermal gravimetric analysis (TGA) was carried out to support the findings from pH measurements. In addition, thermal conductivity (k-value) and strength activity indices of these cement mortars were discussed. The results showed that pH values of all blended cement mortars were less than ordinary Portland cement (OPC) mortar in all curing conditions used. There was a decreasing tendency in pH of all mortars with passage of time. In addition, the pH of cement mortars was not only dependent on the quantity of Ca(OH)₂. The effect of adding SCMs on the pH value of cement mortar should be monitored and measured for both short and long terms.

• Journal of the Korea Institute of Building Construction
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• v.18 no.1
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• pp.33-40
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• 2018

Currently, in South Korea, because of reducing the construction period or treating wasted water, there are some cases of missing wet curing for concrete structure even though for high strength concrete. This air curing conditions is considered to cause increased possibility of compressive strength decrease, and increasing drying or autogenous shrinkages. As a solution of shrinkage of concrete, The authors' research team conducted the research on improving durability of concrete with decreasing autogenous shrinkage by adding the oil or fat to induce the saponification. Therefore, in this research, the influence of curing method on compressive strength, shrinkage on evaporation rate of high strength mortar including high volume supplementary cementitious materials (SCMs) was evaluated depending on various curing methods such as air curing, drying after painting emulsified refined cooking oil (ERCO), and drying after 7 and 28 days' wet curing. The experimental result showed the air curing method caused approximately 50% of decreased compressive strength and 1.9 times of increased shrinkage rather than the 28-day-wet curing method, thus it was known that the wet curing significantly influences on performance of high strength mortar using high volume SCMs. However, the ERCO painting curing caused decreased performance of concrete rather than drying after 7 days curing while it caused improved performance of concrete than entire period air curing.

• Journal of the Korea Institute of Building Construction
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• v.19 no.3
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• pp.219-228
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• 2019

The aim of the research is to provide a fundamental data of low viscosity typed superplasticizer (SP) on cement-based materials incorporating various supplementary cementitious materials (SCMs). As a relatively new product, low-viscosity typed SP has introduced for high performance concrete with high viscosity due to its high solid volume fraction with various SCMs. However, there are not enough research or reports on the performance of the low viscosity typed SP with cement-based materials incorporting SCMs. hence, in this research, for cement paste and mortar, fluidity and rheological properties were evaluated when the mixtures contained various SCMs such as fly ash, blast furnace slag, and silica fume. From the experiment conducted, it was checked that the low viscosity typed superplasticizer decreased the plastic viscosity of the mixture as well as the yield stress. From the results of this research, it is expected to contribute on introduction of new type SP for high performance concrete or high-viscous cementitious materials.

• Advances in concrete construction
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• v.16 no.6
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• pp.303-316
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• 2023

Using industrial wastes and construction and demolition (C&D) wastes is potentially advantageous for concrete production in terms of sustainability improvement. In this paper, a sustainable Self-Compacting Concrete (SCC) made with industrial wastes and C&D wastes was proposed by considerably replacing natural counterparts with recycled coarse aggregates (RCAs) and supplementary cementitious materials (SCMs) (i.e., Fly ash (FA), ground granulated blast furnace slag (GGBS) and silica fume (SF)). A total of 12 SCC mixes with various RCAs and different combination SCMs were prepared, which comprise binary, ternary and quaternary mixes. The mechanical properties in terms of compressive strength and static elasticity modulus of recycled aggregates (RA-SCC) mixes were determined and analyzed. Microstructural study was implemented to analyze the reason of improvement on mechanical properties. By means of life cycle assessment (LCA) method, the environmental impacts of RA-SCC with various RCAs and SCMs were quantified, analyzed and compared in the system boundary of "cradle-to-gate". In addition, the comparison of LCA results with respect to mechanical properties was conducted. The results demonstrate that the addition of proposed combination SCMs leads to significant improvement in mechanical properties of quaternary RA-SCC mixes with FA, GGBS and SF. Furthermore, quaternary RA-SCC mixes emit lowest environmental burdens without compromising mechanical properties. Thus, using the combination of FA, GGBS and SF as cement substitution to manufacture RA-SCC significantly improves the sustainability of SCC by minimizing the depletion of cement and non-renewable natural resources.

• International Journal of Concrete Structures and Materials
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• v.7 no.2
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• pp.155-163
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• 2013

The use of sustainable technologies such as supplementary cementitious materials (SCMs), and/or recycled materials is expected to positively affect the performance of concrete mixtures. However, it is imperative to qualify and implement such mixtures in practice, if the required specifications of their intended application are met. This paper presents the results of a laboratory investigation of self-consolidating concrete (SCC) containing sustainable technologies. Twelve mixes were prepared with different combinations of fly ash, slag, and recycled asphalt pavement (RAP). Fresh and hardened concrete properties were measured, as expected the inclusion of the sustainable technologies affected both fresh and hardened concrete properties. Analysis of the experimental data indicated that inclusion of RAP not only reduces the ultimate strength, but it also affected the compressive strength development rate. The addition of RAP to mixes showed a consistent effect, with a drop in strength after 3, 14, and 28 days as the RAP content increased from 0 to 50 %. However, most of the mixes satisfied SCC fresh properties requirements, including mixes with up to 50 % RAP. Moreover, several mixes satisfied compressive strength requirement for pavements and bridges, those mixes included relatively high percentages of SCMs and RAP.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.126-127
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• 2016

In this research, the optimum combination of fly ash (FA) and blast furnace slag (BS) was deduced by analyzing the performance of high volume supplementary cementitious materials (SCMs) cement mortar depending on various combinations of cement, FA, and BS. As a result, increased workability was shown with increased the portion of FA, while air content, setting time, and compressive strength were decreased.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.133-134
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• 2014

As a previous research, improved durability of concrete by filling capillary pores with waste cooking oil was suggested as a method of controlling carbonation of the concrete replaced high volume of SCMs. on the other hand, the emulsified refined waste cooking oil for better mixing performance had a drawback of reducing air content related with decreasing freeze-thawing resistance. As a solution of this problem, surface applying method was suggested instead of adding in mixing process, and in this research, the performance regarding concrete durability are evaluated comparing emulsified refined cooking oil with water-repelling agent.

• Computers and Concrete
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• v.22 no.2
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• pp.183-196
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• 2018

The rheological behaviour of high strength self compacting concrete (HS-SCC) studied through an experimental investigation is presented in this paper. The effect of variation in supplementary cementitious materials (SCM) $vis-{\grave{a}}-vis$ four different types of processed crushed sand as fine aggregates is studied. Apart from the ordinary Portland cement (OPC), the SCMs such as fly ash (FA), ground granulated blast furnace slag (GGBS) ultrafine slag (UFS) and micro-silica (MS) are used in different percentages keeping the mix -paste volume and flow of concrete, constant. The combinations of rheology, strength and durability are equally important for selection of mixes in respect of high-rise building constructions. These combinations are referred to as the rheo-strength and rheo-durability which is scientifically linked to performance based rating. The findings show that the fineness of the sands and types of SCM affects the rheo-strength and rheo-durability performance of HS-SCC. The high amount of fines often seen in fine aggregates contributes to the higher yield stress. Further, the mixes with processed sand is found to offer better rheology as compared to that of mixes made using unwashed crushed sand, washed plaster sand, washed fine natural sand. The micro silica and ultra-fine slag conjunction with washed crushed sand can be a good solution for high rise construction in terms of rheo-strength and rheo-durability performance.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.3
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• pp.228-236
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• 2015

In this research, the influence of painting materials and applying timing on carbonation and chloride resistances of high volume SCMs concrete was evaluated. As a durability improving method, comparative tests were conducted with painting materials of ERCO (emulsified refined cooking oil), RCO (refined cooking oil), WR (water repellent agent), and ERCO + WR and with painting timings of right after demolding, and 28 days after the wet curing. From the experiment results, in the case of carbonation and chloride resistance, the carbonation depth and chloride penetration depth were decreased when the painting materials were applied in 28 days of wet curing. Additionally, for painting materials, with the order of ERCO, RCO, ERCO+WR, and WR, the carbonation and chloride penentration was delayed. Hence it is considered that ERCO shows the most favorable performance of resistance against carbonation and chloride penetration.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.292-298
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• 2016

In this research, considering the practical situation of separated placing method for mass concrete structure, an efficient method of controlling the heat of hydration is suggested by comparing between the simulated values and actual measurements conducted with the optimum mix design obtained from the various mix conditions with different types and amount of supplementary cementitious materials(SCMs). As the result of the research, firstly, the optimum mix designs for top and bottom layers were determined by Midas gen as OPC to FA of 85 to 15, and OPC to FA to BS of 50 to 20 to 30, respectively. The concrete mixtures prepared with the mix designs determined from the simulation satisfied the target performance range in slump, air content and compressive strength. Additionally, from temperature measurement for the actual mass concrete placed during spring, the maximum temperature difference between surface and core was about $10^{\circ}C$ with 59 and $49^{\circ}C$ for top and bottom layers, respectively, and 1.4 of cracking index was obtained. Therefore, considering the practical conditions of mass concrete construction, it is considered that the different heat of hydration method using different mix designs with SCMs can be an efficient method for controlling thermal cracking and settling cracking of mass concrete.