• Journal of the Korea Concrete Institute
• /
• v.16 no.5 s.83
• /
• pp.651-657
• /
• 2004

The effects of polymer-cement ratio, antifoamer content and shrinkage-reducing agent content on the air content, setting time, drying shrinkage and strength of high-fluidity polymer-modified mortars using redispersible polymer powder are examined. As a result, the air content of the polymer-modified mortars using redispersible polymer powder tends to decrease nth increasing polymer-cement ratio and antifoamer content. Regardless of the antifoamer content, the setting time of the polymer-modified mortars using redispersible polymer powder tends to delayed with increasing polymer-cement ratio. Irrespective of the antifoamer content, the drying shrinkage of the polymer-modified mortars using redispersible polymer powder tend to decrease with increasing polymer-cement ratio and shrinkage-reducing agent content. Regardless of the antifoamer content, the flexural and tensile strengths of the polymer-modified mortars using redispersible polymer powder tends to increase with increasing polymer-cement ratio, and tend to decrease with increasing shrinkage-reducing agent content. However, the compressive strength of the polymer-modified mortars using redispersible polymer powder decreases with increasing polymer-cement ratio and shrinkage-reducing agent content.

• Journal of the Korea Concrete Institute
• /
• v.15 no.3
• /
• pp.409-416
• /
• 2003

The effects of polymer-cement ratio, antifoamer content and shrinkage-reducing agent content on the air content, setting time, drying shrinkage and strength of polymer-modified mortars using redispersible polymer powder are examined. As a result, the air content of the polymer-modified mortars using redispersible polymer powder tend to decrease with increasing polymer-cement ratio and antifoamer content. Regardless of the antifoamer content, the setting time of the polymer-modified mortars using redispersible polymer powder tend to delayed with increasing polymer-cement ratio. Irrespective of the antifoamer content, the drying shrinkage of the polymer-modified mortars using redispersible polymer powder tend to decrease with increasing polymer-cement ratio and shrinkage-reducing agent content. Regardless of the antifoamer content, the flexural and tensile strengths of the ultrarapid-hardening polymer-modified mortars using redispersible polymer powder tend to increase with increasing polymer-cement ratio, and tend to decrease with increasing shrinkage-reducing agent content. However, the compressive strength of the ultrarapid-hardening polymer-modified mortars using redispersible polymer powder decrease with increasing polymer-cement ratio and shrinkage-reducing agent content.

• Geomechanics and Engineering
• /
• v.16 no.4
• /
• pp.375-384
• /
• 2018

Unconfined compressive strength (UCS) of high plasticity clayey soil mixed with 5 and 10 % of Portland cement and four chemical agents such as sodium hexametaphosphate, aluminum sulfate, sodium carbonate, and sodium silicate with 0, 5, 10, and 20% concentrations was comparatively evaluated. The individual and combined effects of the cement and chemical agents on the UCS of the soil mixture were investigated. The strength of the soil-cement mixture generally increases with increasing the cement content. However, if the chemical agent is added to the mixture, the strength of the cement-chemical agent-soil mixture tends to vary depending on the type and the amount of the chemical agent. At low concentrations of 5% of aluminum sulfate and 5% and 10% of sodium carbonate, the average UCS of the cement-chemical agent-soil mixture slightly increased compared to pure clay due to increasing the flocculation of the clay in the mixture. However, at high concentrations (20%) of all chemical agents, the UCS significantly decreased compared to the pure clay and clay-cement mixtures. In the case of high cement content, the rate of UCS reduction is the highest among all cement-chemical agent-soil mixtures, which is more than three times higher in comparison to the soil-chemical agent mixtures without cement. Therefore, in the mixture with high cement (> 10%), the reduction of the USC is very sensitive when the chemical agent is added.

• Environmental Engineering Research
• /
• v.25 no.3
• /
• pp.409-417
• /
• 2020

Investigation was carried out to assess the effect of cement dust deposition on the physico-chemical properties of soil near some cement plants in Jaintia Hills, Meghalaya. Soil samples were collected and analysed and compared with the control site. Comparison of various soil physico-chemical parameters revealed that cement dust emanating from cement plants has changed the soil quality in the surrounding areas of cement plants. The normal soil pH in the area is generally acidic. However, due to the continuous deposition of cement dust soil pH was found slightly alkaline near the cement plants. The higher values of soil parameters such as electrical conductivity and bulk density were also noticed near the cement plants. However, lower values of water holding capacity, soil moisture content, soil organic carbon and total nitrogen content were found compared to the control sites. The effect of cement dust deposition on soil is more in areas nearer to the cement plants. At present the changes may not be so serious but if this trend continues, soil properties of a vast area around the cement plants are likely to change leading to multiple effects on flora, fauna and socio-economy of the area.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1994.10a
• /
• pp.133-136
• /
• 1994

This study is to investigate properties of the ultra high-strength concrete using silica rume and fly ash. For this purpose, the properties of fresh concrete and hardened concrete are examined with varing water-cement ratio, silica fume and fly ash content and so on. From these test results, it is possible to maunfacture the miximum strength of 1, 200kg/$\textrm{cm}^2$ with cement content 800kg/$\textrm{m}^3$, 18% water-cement ratio, 105 silica fume content.

• Journal of the Korean Ceramic Society
• /
• v.26 no.5
• /
• pp.698-704
• /
• 1989

Basic investigation for the flexural strength and water stability of hardened cement pastes using ordinary portland cement with water-soluble polyer (hydroxypropyl methyl cellulose ; HPMC) was carried out with 0.2 of water cement ratio. For molding of the specimen, the paste was mixed by twin roll mill. According to increase in the content of HPMC, the setting time of cement paste was delayed and the flexural strength was increased. The maximum flexural strength of hardened cement paste with 5.0wt% of HPMC was about 330 kg/$\textrm{cm}^2$. The expansion of the hardened cement paste immersed in water was increased with the content of water soluble polymer(HPMC). Consequently, the strength and the water stability of the hardened cement pastes were remarkably reduced by the expansion of them.

• Proceedings of the Korean Society of Agricultural Engineers Conference
• /
• 2003.10a
• /
• pp.195-198
• /
• 2003

A small amount of cement can be added to the soil with high water content to improve its engineering properties. It is difficult to point out the exact time when liquified state of soil is transformed into semi-plastic or plastic states when high water content soil is hydrated by cement. In this study fall cone penetration are used to explain the phase change and compactable status of soil cement. And engineering properties of soil cement compacted in plastic state are investigated. Results reveal that fall cone penetration depth of 1mm or less is judged to a compactable state of soil-cement. Permeability and CBR values of soil cement increased with mixing ratio increased.

• Journal of the Korean Ceramic Society
• /
• v.34 no.10
• /
• pp.1037-1044
• /
• 1997

Mechanical properties and water stability of HAC/PVA based MDF cement composite were investigated using polyurethane(PU) resin, silane coupling agent and various PVA. The results were as follows ; The flexural strength of MDF cement composite increased as increasing with PVA content. Low-viscosity PVA developed higher flexural strength than high-viscosity PVA under a drying curing condition. But the strength of water immersed specimen decreased. Water stability of MDF cement improved as increasing with content of PU. Consequently, water stability of polyurethane 7% added MDF cement was about 2 times higher than that of the controlled specimen. Furthermore, the strength and water stability of diamine group based silane couling agent in using MDF cement increased and improved dramatically.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2020.11a
• /
• pp.102-103
• /
• 2020

In this study, the effect of the change in the cement contents on the basic properties of the concrete and the estimation of the cement contents of hardened concretes using the hydrochloric acid melting heat. As a result of the study, as the cement contents increased, the fluidity and compressive strength increased, and there was no significant difference in the air contents and the unit volume mass. In addition, it showed a high correlation when compared with the estimated cement contents derived using the hydrochloric acid melting and the cement contents at the time of mixing. Therefore, it is considered that the hydrochloric acid melting is possible as a method of estimating the cement contents of concrete.

• International Journal of Highway Engineering
• /
• v.11 no.3
• /
• pp.51-60
• /
• 2009

This study investigates the fresh state characteristics, strength, chloride ion penetration resistance and freeze-thaw resistance of the suggested high strength-high durability cement concrete pavement. The required workability and air content could be achieved by using an appropriate admixtures. However its dosage should be carefully determined through field trial batches. Compressive strength increased with the increased cement content and, in particular, high cement volume concrete continuously developed strength up to 90 days. No clear relationship, however, existed between flexural strength and cement content. Chloride penetration resistance seemed as a function of curing age rather than the cement content. Freeze-thaw resistance test was conducted using two different coolants, tap water and 4% NaCl solution. When the tap water was used no severe damage was observed up to 300 cycles regardless the air content. Under 4% NaCl solution, specimens of 326kg/$m^3$ cement content showed severe damage with surface scaling. Based on the experimental investigations herein, it is highly recommended that the cement content be greater than 400kg/$m^3$ for strength-high durability cement concrete pavement structures.