• Journal of the Korea Institute of Building Construction
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• v.15 no.5
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• pp.451-456
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• 2015

This study aimed to evaluate of the hardened properties (mortar consistency, setting time, absorption properties, drying shrinkage, and bond strength) of the basalt powder sludge mortar recycling a basalt powder sludge occurred during the manufacture process of basalt stone as a replacing material for the sea-sand used to cement filling compound for surface preparation. The hardened mortar made of the basalt powder sludge showed an enhanced performance or similar with the properties of normal mortar used to cement filling compound for surface preparation. But, the drying shrinkage was increased more than a normal cement mortar in the hardened mortar made of the basalt powder sludge since curing 8 - 9days. And the bond strength is low in the hardened mortar used the basalt powder sludge. On the whole, properties of the hardened mortar used the basalt powder sludge correspond to the required minimum quality criterion in the KS F 4716 'cement filling compound for surface preparation'.

• Applied Chemistry for Engineering
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• v.8 no.5
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• pp.822-829
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• 1997

When $Al_2(SO_4)_3$ as an accelerator was added to $\beta$-hemihydrate gypsum, the setting time, mobility and compressive strength properties of $\beta$-hemihydrate gypsum were examined with the adding of two types grounded gypsum crushed by ball mill. By 15wt% adding of 7% $Al_2(SO_4)_3$ dilute solution, the setting time of $\beta$-hemihydrate gypsum was sharply accelerated than that of non-added $\beta$-hemihydrate gypsum. When ground phospho gypsum(PG) and chemical gypsum(CG) were added to $\beta$-hemihydrate gypsum, the initial and final setting time of $\beta$-hemihydrate gypsum were accelerated markedly with the increasing of grinding time and added amount of ground phospho gypsum. Especially, this trend largely presented when ground phospho gypsum was added to $\beta$-hemihydrate gypsum. The compressive strength of $\beta$-hemihydrate gypsum added by ground phospho and chemical gypsum was largely increased at initial curing time such as 1, 3 days. Particularly, the compressive strength of $\beta$-hemihydrate gypsum added by ground phospho gypsum was increased by 15~20% than that of ground chemical gypsum.

• Cement Symposium
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• s.39
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• pp.103-110
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• 2012

• Journal of the Korea Concrete Institute
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• v.14 no.4
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• pp.589-596
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• 2002

In this paper, setting and strength performances of concrete containing saccharic type super retarding agents are investigated under various kinds and contents of super retarding agents. According to test results, as super retarding agents contents increase, slump shows to be increased, while air contents decrease about 1∼2％. Setting time shows to be retarded considerably with increase of super retarding agents. It takes 20 days after mixing to reach final setting in case of concrete containing gluconic acid more than 0.3％. And 10 days after mixing in case of enhancing sucrose, white and brown sugar. Compressive strength of concrete containing super retarding agents is lower than that of plain concrete at early age. However, it keeps up with and exceeds the compressive strength of plain concrete at later age. White sugar md brown sugar shows positive performances in delaying setting time and strength compared to existing super retarding agents. n further investigations on durability are conducted, it is thought that application of white sugar as super retarding agent is available.

• Journal of the Korea Institute of Building Construction
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• v.15 no.1
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• pp.25-33
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• 2015

In this study, initial crack index was evaluated by FEM analysis to find the crack propagation from hydration heat in precast concrete. As results, as the usage of hardening accelerator increased, initial compressive strength increased and setting time was shortened. Additionally, as amounts of hardening accelerators increased, the central temperature of concrete increased and the time to reach the highest temperature was shortened. It was demonstrated that the hardening accelerators accelerated the hydration reaction of cement, and caused the increase of hydration heat within the short period of time. Furthermore, the crack index for evaluating the heat level was performed by FEM. As results, there was no problem about the cracks, despite of the growth of initial high hydration heat. This is because of the increased tensile strength that is large enough to sustain the thermally induced-stress.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.89-90
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• 2018

In recent years, harmful substances and fine dust in the air are caused by respiratory and cardiovascular diseases through various mechanisms when they are introduced into the human body through respiration, thereby exacerbating human health and causing cancer by prolonged exposure do. In order to prevent such fine dust from being introduced into the room and to improve indoor air quality, improvement of air quality has attracted attention. Among indoor air pollutants, fine dust and CO₂ are pollutants that are directly affected by indoor number and activity. The purpose of this study is to evaluate the basic performance of cement matrix using photosynthetic bacteria as a basic study of fine dust and CO₂ adsorption type matrix to suppress indoor air pollution and improve air quality.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.323-328
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• 2002

Rapid set accelerators are widely used in tunnel construction, however quality criteria of and dosage are not well established. The density and solid content of admixtures, setting time and compressive strength of paste and mortar with admixtures were investigated to establish the quality criteria. While the early strength of mortar with sodium-silicate, sodium-aluminate and calcium aluminate type admixtures that have high alkali content are very high, but long-term strength are low. Aggregates of shotcrete has to be carefully selected. Sodium-silicate type admixture need longer setting time than the others.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.545-548
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• 2008

In this study aluminium sulfate, Ca(OH)$_2$, K-R Slag and $Na_2SO_4$ were used as active admixtures and their concentration 1, 3, 5, 7 weight percent in cement. The physical properties of active admixtures cement mortar were investigated by flow test and compressive strength. It was found that the resulting active admixtures exhibited the higher compressive strength than OPC mortar up. From the test results, cement mortars added active admixture have a good fundamental property.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.105-111
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• 2020

The present study examined the effect of the silica-based accelerating agents on the setting time and compressive strength gain of biomimetic glycocalix coating materials that has been developed for protecting the substrate of concrete exposed to chemical and microbiological attacks. The accelerating agent contents varied from 10mL/L to 40mL/L in the mixtures of glycocalix coating materials determined for shotcrete and lining techniques. Test results showed that the setting time of coating materials containing accelerating agents was affected by the contents of the bacteria carrier. When the accelerating agent content was 40mL/L, the final setting time was 80 minutes for shotcrete mixtures and 318 minutes for lining mixtures. Meanwhile, the compressive strength gain of coating materials with accelerating agents tended to be lower than that of counterpart materials without accelerating agents.

• Journal of the Korea Concrete Institute
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• v.25 no.2
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• pp.201-207
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• 2013

When hot weather concrete is utilized, the cooling methods of cooling pipe, liquid nitrogen, ice, etc., are used to prevent the poor consistency and cold joint due to high temperature. These methods, however, spike the production cost and energy consumption, and make quality control difficult. Among these methods is one that involves the use of a retarder. Although economical, retarder is caused difficulty of retarded hardening and setting time control due to inaccurate weighing and poor working condition. Therefore, how to make a tablet for hot weather concrete, as with the existing pharmacy and foods, is discussed in this study, including the following items: mortar setting time, flow test by elapsed time, physical and mechanical properties of concrete. As a result, gluconic acid is superior to lignosulfonic acid and the possibility of using them for such purpose without quality degradation was confirmed in this study, when retarder is tabletting.