• Journal of the Korean Geotechnical Society
• /
• v.29 no.1
• /
• pp.39-47
• /
• 2013

With the increase in the application of CLSM using coal ash, we performed a basic research on CLSM material, laying focus on the correlation between compressive strength and unit weight of lightweight foamed CLSM. The unconfined compression strength is a criterion for the judgment of the possibility of re-excavation and an important factor determining the economy, efficiency, and excavation character. However, to know the quantitative compression strength value takes a certain amount of time, because the applicability of unconfined compression strength of CLSM is judged by the standard of 28days. Therefore, in this study the relation between compressive strength and unit weight (foam slurry unit weight, apparent unit weight) is analyzed focusing on lightweight foamed CLSM. We also suggested a formula which can easily predict the 28-day compressive strength only using unit weight value without the need to cure the slurry for 28 days.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.8 no.1
• /
• pp.1-10
• /
• 2013

In this study utilize industry product for OPC(ordinary portland cement) and BFS(blast furnace slag) mixing concrete early age compressive strength elevation and executed study for high strength binder. Association ratio of industry product for high strength binder manufacture is Titanogypsum (4) : Limestone (3) : Waterworks Sludge by ratio of (3) as it is proper move. high strength binder mixing rate appeared that (7~9) % are proper via preliminary test. Could confirm that display high compressive strength incidence rate in early age than plain harmony according as mix high strength binder mixing concrete compressive strength high strength binder. Also, high strength binder generality that give function than high strength binder used in existing displayed more excellent intensity, and compressive strength displayed result that multiply single breadth according as high strength binder substitute that give function increases.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.5 no.1
• /
• pp.117-124
• /
• 2010

The aggregate, which does not satisfy the standard of KS F 2573, was selected for this investigation. The 28day compressive strength of recycled aggregate concrete without pozzolan material was 21.7MPa, which was less than the strength of concrete made with crushed stone. However, the compressive strength at 28 days was improved by mixing early rapid hardening cement to the cement at the weight ratio of 2.5%. Furthermore, the compressive strength at 91 days and 180 days increased significantly by adding fly ash, slag powder, and diatom powder. The tensile strength of recycled aggregate concrete with pozzolan material also increased about 40% compared to the general concrete. Futhermore, the shrinkage and creep of recycled aggregate concrete with fly ash and slag powder was a little decreased that of recycled aggregate concrete with fly ash and diatom powder. Relationship between compressive strength and creep coefficient was shown to the linear relation like as ${\sigma}_c=-30CF+404$.

• Journal of the Korea Institute of Building Construction
• /
• v.16 no.1
• /
• pp.53-58
• /
• 2016

In order to investigate the feasibility of municipal solid waste incineration ash melted slag powder as admixture, an experimental study was performed on cement mortar with municipal solid waste incineration ash melted slag powder. Fresh mortar properties and strength properties with various municipal solid waste incineration ash melted slag powder replacement ratios were estimated. There replacement ratio adopted in this study was 0, 10, 20, 30, 40, 50%. After then flow properties was considered as properties of fresh mortar. And compressive strength was determined 3, 7, 14, 28, 56 days for the hardened mortar specimens. According to the test results, the flow of mortar was increased with in replacement amount of municipal solid waste incineration ash melted slag powder. Furthermore, compressive strength at early age was decreased, whereas the compressive strength at the age of 28, 56day was increased.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.1
• /
• pp.67-73
• /
• 2020

In this study, the self-healing performance of mortar beams containing self-healing materials was evaluated through experiments. Normal mortar beams and self-healing mortar beams were used In the experiments. The self-healing performance was evaluated by comparing the mortar compressive strength, member strength, and self-healing effects of cracks. The experimental results showed that the compressive strength of mortar containing self-healing material was smaller than that of normal mortar, but the ratio of 118 days compressive strength to 28 days compressive strength was the same. The member strength tended to increase with increasing curing period. In normal mortar specimens, the member strength did not recover even if the curing period increased, but the strength of the self-healing mortar specimens tended to recover as reaction products were produced. The crack width tended to decrease after the healing periods in both specimens, but the reaction product was observed only in the self-healing mortar specimens.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.2 no.4
• /
• pp.360-366
• /
• 2014

In this study, effect of types and replacement ratio of alkali activator on compressive strength of ground granulated blast furnace slag mortar has been reviewed. Types of alkali activator are NaOH, $Ca(OH)_2$, $Na_2SO_4$, and KOH. Replacement ratio of alkali activator is 7.5, 10, 12.5, and 15%, respectively. As results, under high temperature curing condition, 1 day compressive strength development with NaOH and KOH was higher than that of $Ca(OH)_2$ and $Na_2SO_4$. Regardless of types of alkali activator, compressive strength increased with increasing pH. This can be explained by the fact that impermeable film on the surface of slag which is generated when slag contacts water has been destroyed by alkali activator, and this promotes hydration reaction. Also, 1 day age compressive strength of specimen with high temperature curing was higher than that of specimen with standard curing. 28 days age compressive strength of specimen with high temperature curing was less than or equal to that of specimen with standard curing.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.5
• /
• pp.1069-1080
• /
• 1994

For complying with the demand of developing high strength concrete, the high strength concrete with higher cement contents and lower water-cement ratio using high range water reducing admixture has been manufactured. In this study, for the purpose of improving the strength of concrete, concrete with silica fume and gypsum was produced so that it was acquired to high compressive strength of $1,058kg/cm^2$, $1,170kg/cm^2$ at age 28 and 91 days, respectively. But neither tensile strength nor modulus of elasticity were highly improved although the compressive strength of the concrete increased. And it was concluded that a higher slump loss of fresh high strength concrete and interior temperature increment of concrete in according to elapsed time than convential concrete should be solved.

• Magazine of the Korea Concrete Institute
• /
• v.7 no.1
• /
• pp.126-135
• /
• 1995

The strength development of PFA concretes were invest~gated in this study. The work undertaken was divided into two parts which considered both the influence of PFA replacement level up to 45% and the effect of cement type at the high PRA leveI(45%). The additiorlal cement considered included a rapdhardemng portland ccnlent. The full range of concrete struc tural grades were studied anti ciight cu~ing contlltiorls covering those 11:ied 111 practlce were examined. The early strength retluced wit11 increasing PFA content. However, post 28days, the reverse was observed. It was posslhle through the use of rapid hardening portland cement at the high PFA level to achieve similar early strength to OPC concrete, with the same benefits noted above also being obtained post 28 days. The compressive strength uf hlgh PYA content concrt:tes at hgh temperature m s found to be higher than the ccmtrol at all ages hoth in water and alr. The same trends were observed at low t.ernperature in air. However, the reverse occur-ed at the low temperature In water.

• Korean Journal of Agricultural Science
• /
• v.6 no.2
• /
• pp.185-191
• /
• 1979

Compressive and tensile strengths of commonly being used mortar and mortar specially hardened by adding 1%, 2% and 3% of $CaCl_2$ were compared under the different mixing ratio of mortar and ages to investigate the effect of $CaCl_2$ which is being used as a promotor for coagulation and hardness, on the strength of mortar. The results obtained were as follows: 1. The compressive strength of mortar hardened by addition of $CaCl_2$ was higher than that of commonly being used mortar. The highest compressive strength of mortar was obtained when 2% of $CaCl_2$ were added. 2. The tensile strength of mortar, which was made by adding $CaCl_2$ and aged for seven days, was higher than that of commonly being used mortar. The highest tensile strength of mortar was obtained when 1% of $CaCl_2$ was added and aged for 28 days. And the tensile strength of mortar with 2% of $CaCl_2$ was lower than that of commonly being used mortar. 3. When the amount of $CaCl_2$ added was higher than 3%, the mortar was abruptly hardened and thereby occurred crack was considered lowering strength of mortar. 4. The rich mix was effective for the increasing the compressive and tensile strength before seven days of age and less effective after seven days of age. Therefore, the addition of one to two per cent of $CaCl_2$ would be effective for promoting initial strength of mortar during winter season.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.6
• /
• pp.82-89
• /
• 2014

The purpose of this study is to propose a simple model to evaluate the compressive strength development of concrete with various supplementary cementitious materials (SCMs) and cured under different temperatures. For the generalization of the model, the ACI 209 parabola equation was modified based on the maturity function and then experimental constants A and B and 28-day compressive strength were determined from the regression analysis using a total of 265 data-sets compiled from the available literature. To verify the proposed model, concrete specimens classified into 3 Groups were prepared according to the SCM level as a partial replacement of cement and curing temperature. The analysis of existing data clearly revealed that the 28-day compressive strength decreases when the curing temperature is higher and/or lower than the reference curing temperature ($20^{\circ}C$). Furthermore, test results showed that the compressive strength development of concrete cured under $20^{\circ}C$ until an early age of 3 days was marginally affected by the curing temperature afterward. The proposed model accurately predicts the compressive strength development of concrete tested, indicating that the mean and standard deviation of the ratios between predictions and experiments are 1.00 and 0.08, respectively.