• Journal of the Korea Institute of Building Construction
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• 제18권4호
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• pp.329-335
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• 2018

The objective of this study is to develop a mortar mixture with high workability and adhesive strength for section jacketing in seismic strengthening technology of existing concrete structures. To achieve targeted requirements of the mortars (initial flow exceeding 200 mm, compressive strength of 30MPa, and adhesive strength exceeding 1MPa), step-by-step tests were conducted under the variation of the following mixture parameters: water-to-binder ratio, sand-to-binder ratio, polymer-to-binder ratio, dosage of viscosity agent, and content of ultra-rapid-hardening cement. The adhesive strength of the mortars was also estimated with respect to the various surface treatment states of existing concrete. Based on the test results, the mortar mixture with the polymer-to-binder ratio of 10% and the content of ultra-rapid-hardening cement of 5% can be recommended for the section jacketing materials. The recommended mortar mixture satisfied the targeted requirements as follows: initial flow of 220 mm, high-early strength gain, 28-day compressive strength of 35MPa, and adhesive strength exceeding 1.2MPa.

• Computers and Concrete
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• 제9권6호
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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 Korea Concrete Institute
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• 제15권6호
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• pp.888-893
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• 2003

The purpose of this study is to make clear the durability of the polymer films formed in the autoclaved polymer-modified mortars and concretes. The polymer films prepared with polymer dispersions such as a styrene-butadiene rubber (SBR) latex, a poly (ethylene-vinyl acetate)(EVA) emulsion and a polyacrylic ester (PAE) emulsion for polymeric admixtures are exposed to autoclaving at 18$0^{\circ}C$ in temperature and 1.01 MPa in vapor pressure, and subjected to tensile test and infrared spectroscopy. The durability of the polymer films is evaluated from the application of autoclaving to the polymer films under saturated Ca(OH)$_2$ solution immersion causes no degradation for SBR films and a significant degradation due to the saponification of the polymers for EVA and PAE films. Accordingly, in the application of autoclaving to polymer-modified mortars and concretes, it is suggested that SBR-modified mortars and concretes are hardly degraded but EVA- and PAE-modified mortars and concretes are markedly degraded by the saponification of the polymers.

• Computers and Concrete
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• 제19권3호
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• pp.275-282
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• 2017

The aim of this study is to build Machine Learning models to evaluate the effect of blast furnace slag (BFS) and waste tire rubber powder (WTRP) on the compressive strength of cement mortars. In order to develop these models, 12 different mixes with 288 specimens of the 2, 7, 28, and 90 days compressive strength experimental results of cement mortars containing BFS, WTRP and BFS+WTRP were used in training and testing by Random Forest, Ada Boost, SVM and Bayes classifier machine learning models, which implement standard cement tests. The machine learning models were trained with 288 data that acquired from experimental results. The models had four input parameters that cover the amount of Portland cement, BFS, WTRP and sample ages. Furthermore, it had one output parameter which is compressive strength of cement mortars. Experimental observations from compressive strength tests were compared with predictions of machine learning methods. In order to do predictive experimentation, we exploit R programming language and corresponding packages. During experimentation on the dataset, Random Forest, Ada Boost and SVM models have produced notable good outputs with higher coefficients of determination of R2, RMS and MAPE. Among the machine learning algorithms, Ada Boost presented the best R2, RMS and MAPE values, which are 0.9831, 5.2425 and 0.1105, respectively. As a result, in the model, the testing results indicated that experimental data can be estimated to a notable close extent by the model.

• Polymer(Korea)
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• 제33권4호
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• pp.342-346
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• 2009

The effects of the monomer ratios on the typical properties of polymer modified mortars that contain styrene and butyl acrylate latexes was investigated. Basic data was also obtained that is necessary for the development of appropriate latexes for cement modifiers. Polymer modified mortars that contain styrene and butyl acrylate latexes polymerized with various monomer ratios were prepared for different polymer-cement ratios. They were then tested to obtain the particle size of the polymer latexes, air contents, water-cement ratios, flexural and compressive strengths, water absorption, and chloride-ion penetration. From the test results, the polymer modified mortars that have styrene and butyl acrylate latexes (with the mix proportions of synthesis having monomer ratios of between 40:60 to 60:40 for the appropriate mix proportions) could be recommended for practical applications. The basic properties of the polymer modified mortars were more affected by the polymer-cement ratio than by the monomer ratio, and were improved over unmodified mortar.

• KIEAE Journal
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• 제10권5호
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• pp.131-137
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• 2010

The building industry must aim at high-durability and sustainability. A holistic life cycle based approach is recommended to reduce the environmental load. In recent years, technical innovations in the construction industry have advanced to a great extent, and caused the active research and development of high-performance and multifunctional construction materials. Nowadays, various polymer powders have been commercialized to manufacture construction materials in the form of prepackaged-type products, which have rapidly been developed for lack of skilled workmen in construction sites. Recently, terpolymer powders of improved quality have been developed and commercialized as cement modifiers. And, hydrocalumite is a material that can adsorb the chloride ions (Cl-) causing the corrosion of reinforcing bars and liberate the nitrite ions (NO2-) inhibiting the corrosion in reinforced concrete, and can provide a self-corrosion inhibition function to the reinforced concrete. The purpose of this study is to ascertain the self-corrosion inhibition function of polymer-modified mortars using redispersible powders with hydrocalumite. Polymer-modified mortars using VA/E/MMA and VAE redispersible powders are prepared with various calumite contents and polymer-binder ratios, and tested for chloride ion penetration depth, corrosion inhibition. As a result, regardless of the polymer-binder ratio, the replacement of ordinary portland cement with hydrocalumite has a marked effect on the corrosion-inhibiting property of the polymer-modified mortars. Anti-corrosion effect of polymer-modified mortars using VA/E/MMA terpolymer powder with hydrocalumite is higher than that of VAE copolymer powder.

• Advances in concrete construction
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• 제15권3호
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• pp.191-202
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• 2023

Palm oil fuel ash (POFA) is a newly emerging pozzolanic material having high amount of silica content. Various forms of POFA were used in cement-based materials (CBMs) in replacement of cement in different dosages of low and high volume. Although, there are many researches on POFA to be used in concrete and mortar, however, this material was not practically used in the construction industry. Engineers and designers need to be confident to use any new developed materials by knowing all engineering properties at short and long terms. As durability concern, concrete pH value is one of the most important properties. Portland cement produces are alkaline initially, however, it may be reduced due to aging and its components. It is believed that by incorporation of supplementary cementitious materials in CBMs the pH value reduces due to utilization of Ca(OH)₂ in pozzolanic reaction. This study is the first attempts to understand the pH value of mortars containing up to 30% POFA under different curing conditions and its changes with time. The results were also compared with the pH of ground granulated ballast furnace slag (GGBFS) and fly ash (FA) content mortars. In addition, the compressive strength of different mortars under different curing conditions were also studied. The results showed that the pH value of control mix (without cementitious materials) was more than all the blended cement mortars indifferent curing conditions at the same ages. However, there was a reducing trend in the pH value of all mortar mixes containing POFA.

• Magazine of the Korean Society of Agricultural Engineers
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• 제27권1호
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• pp.46-61
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• 1985

This study was performed to obtain the basic data which can be applied to the use of foaming mortars. The data was based on the properties of foaming mortars depending upon various mixing ratios and addings to compare those of cement mortar. The foaming agents which was used at this experiment were pre-foamed type and mix-foaming type which is being used as mortar structures. The foaming mortar, mixing ratios of cement to fine aggregate were 1:1, 1: 2, 1 : 3 and 1 : 4. The addings of foaming agents were 0.0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5% and 3.0% of cement weight. The results obtained were summarized as follows; 1. At the mixing ratio of 1 : 1, the lowest water-cement ratios were showed by foaming mortars, respectively. But it gradually was increased in poorer mixing ratio and decreased in more addition of foaming agent. The water-cement ratios were decreased up to 1. 8~22. 0% by G, 2. 2~24. 1 % by U and 0. 7~53. 1% by J foaming mortar than cement mortar. 2, At the mixing ratio of 1 : 1, the highest bulk densities were showed by foaming mortars, respectively. But, it gradually was decreased in poorer mixing ratio and more addition of foaming agent. The bulk densities were decreased up to 1. 4~20. 7% by G, 2. 3~23. 7% by U and 26. 5~56. 5% by J foaming mortar than cement mortar. Therefore, foaming mortar could be utilized to the constructions which need low strengths. 3. At the mixing ratio of 1:1, the lowest absorption rates were showed by foaming mortars, respectively. But, it gradually was increased in poorer mixing ratio and more addition of foaming agent. Specially, according to the absorption rate when immersed in 72 hours, the absorption rates were showed up to 1. 01~1. 24 times by G, 1. 03~1. 58 times by U and 1. 10~5. 91 times by J foaming mortar than cement mortar. It was significantly higher at the early stage of immersed time than cement mortar. 4. At the mixing ratio of 1:1, the lowest air contents were showed by foaming mortars, respectively. But, it gradually was increased in poorer mixing ratio and more addition of foaming agent. Air contents were contented up to 4. 0~17. 2 times by G, 5. 2~23. 2 times by U and 23. 8~74. 5 times by J foaming mortar than cement mortar. 5. At the mixing ratio of 1 : 1, the lowest decreasing rates of strengths were showed by foaming mortars, respectively. But, it gradually was increased in poorer mixing ratio and more addition of foaming agent. Specially, the strengths of 28 days were decreased 0. 4~2. 2% than those of 7 days by foaming mortar, respectively. Also, the correlations between compressive and tensile strength, compressive and ending strength, tensile and bending strength were highly significant as a straight line shaped, respectively. 6. The correlations between absorption rate, air content, compressive strength and bulk density, absorption rate, compressive strength and air content were highly significant, respectively. The multiple regression equations of water-cement ratio, bulk density, absorption ate, air content, compressive strength, tensile strength and bending strength were computed depending on a function of mixing ratio and addition of foaming agent. It was highly significant, respectively. 7. At the mixing ratio of 1 : 1, the highest strengths were showed by cement mortar and foaming mortars, by chemical reagents. But, it gradually was decreased in poorer mixing ratio. The decreasing rates of strengths were in order of H $_2$S0 $_4$, HNO$_3$ and HCI, J,U,G foaming mortar and cement mortar. Specially, at the each mixing ratio, each chemical reagent and 3.0% of foaming agent, J foaming mortar was collapsed obviously. Therefore, for the structures requiring acid resistence, adding of foaming agent should be lower than 3.0%.

• Magazine of the Korean Society of Agricultural Engineers
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• 제21권4호
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• pp.99-107
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• 1979

In order to investigate the utilization of industrial waste and briquette ash for concrete production, briquette ash was used as fine aggregate for mortar production and three different kinds mortars were produced by mixing carbide and bottom aches with cement. These products were compared with mortar, produced by standard sand, in the respects of compressive, tensil and bending strengths. Further study on the economic aspect of utilization of briquette ash is needed but the results obtained from our preliminary study are summarized as follows : 1. The compressive strengths at the age of seven days of mortars, made of one to two ratios of cement to briquette ash, (cement+carbide ash) to briquette ash and(cement+bottom ash) to briquette ash were 70%, 61% and 58%, respectively, of the mortar made of standard sand. The compressive strengths of those mortars at the age of 28 days were 56%, 49% and 48% of the mortar made standard sand. 2. The compressive strengths at the age of seven days of the mortar made of one to two ratios of cement to briquette ash, (cement+carbide ash) to briquette ash and (cement+bottom ash) to briquette ash were 84%, 73%, and 70% of the mortar which was produced according to Korean Standard Value. The compressive strengths of those mortars at the age of 28 days were 85%, 73% and 73% of the mortar of the Korean Standard value. 3. The tensil strengths at the age of seven days of the mortars made of one to two ratios of cement to briquette ash, (cement+carbide ash) to briquette ash, and (cement+bottom ash) to briquette ash were 64%, 36%, and 36%, respectively, of the mortar of standard sand. The tensil strengths of those mortars at the age of 28 days were 70%, 47%, and 39%, respectively, of the standard mortar. The mortars made of one to two ratios of cement to briquette ash at the age of seven and 28 days were higher than the mortars of Korean Standard. The other mortars were 61 to 62% at the age of seven days and 75 to 90% at the age of 28 days of the Korean Standard mortar, respectively. 4. The bending strengths at the age of seven days of mortar made of one to two ratios of cement to briquette ash, (cement+carbide ash) to briquette ash, and (cement+bottom ash) to briquette ash were 46%, 53% and 50% of the mortar of standard sand. The bending strengths of those mortars at the age of 28 days were 90%, 77% and 69%, respectively of the mortar of standard sand. 5. The mortar of briquette ash which was lower in strengths compared with the mortar of cement have shown possibility of its secondary products of cement and concrete. The uses of briquette ash and industrial waste as construction materials would contribute toward solving various pollution problems caused by industrial wastes and saving labor costs needed to cleaning up. Furthermore, the effective use of briquette ash would greatly save the aggregate resources.

• Computers and Concrete
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• 제21권2호
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• pp.149-156
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• 2018

This paper investigated the influence of binary and ternary blends of mineral admixtures in self-compacted mortar (SCM) on the fresh, mechanical and durability properties. For this purpose, 25 mortar mixtures were prepared having a total binder content of $640kg/cm^3$ and water/binder ratio between 0.41 and 0.50. All the mixtures consisted of Portland cement (PC), fly ash (FA) and silica fume (SF) as binary and ternary blends and air-entrained admixture wasn't used while control mixture contained only PC. The compressive and tensile strength tests were conducted for 28 and 91 days as well as slump-flow and V-funnel time tests whilst freeze-thaw (F-T) resistance and capillary water absorption tests were made for 91-day. Finally, in general, the use of SF with FA as ternary blends improved the tensile strength of mortars at 28- and 91-day while the use of SF15 with FA increased the compressive strength of the mortars compared to binary blends of FA. SCM mixtures with ternary blends had lower the sorptivity values than that of the mortars with binary blends of FA and the control mixture due to the beneficial properties of SF while the use of FA with SF as ternary blends induced the F-T resistance enhancement.