• Journal of the Korea Concrete Institute
• /
• v.18 no.2 s.92
• /
• pp.227-232
• /
• 2006

This article presents the results of experimental study that investigates the effect of filler and shrinkage reducing agent influencing on the strength properties of MMA-modified polymer paste that was produced to develop the surface-repair and coating materials of the concrete structures. Results show that the flexural and compressive strengths of the polymer paste increased 29 and 27%, respectively, when the aluminum hydroxide completely replaced the calcium carbonate as the filler Furthermore, when the shrinkage reducing agent was used 30%, both strengths decreased about 29% comparing to when the agent was not used. As in the cases of flexural and compressive strengths, the adhesive strength increased as the content of aluminum hydroxide as the filler increased, and it decreased as the content of shrinkage reducing agent increased. The adhesive strength with a dry concrete substrate turned out to be $30{\sim}40%$ higher than that with a wet concrete substrate.

• Journal of the Korea Concrete Institute
• /
• v.28 no.1
• /
• pp.41-48
• /
• 2016

This research investigates the effects of shrinkage reducing agent (SRA) on the mechanical behavior of strain-hardening cement composite (SHCC). SHCC material with specified compressive strength of 50 MPa was mixed and tested in this study. All SHCC mixes reinforced with volume fraction of 2.2% polyvinyl alcohol (PVA) fiber and test variables are type and dosage of shrinkage reducing agents. The shrinkage reducing materials used in this study are phase change material as the thermal stress reducing materials that have the ability to absorb or release the heat. The effect of SRA was examined based on the change in length caused by shrinkage and hardened mechanical properties, specially compressive, tensile and flexural behaviors, of SHCC material. It was noted that SRA reduces change in length caused by shrinkage at early age. SRA can also improve the tensile and flexural strengths and toughness of SHCC material used in this study.

• Journal of the Korea Concrete Institute
• /
• v.13 no.1
• /
• pp.30-37
• /
• 2001

Generally, polymer mortar made with unsaturated polyester(UP) resin has a high curing shrinkage. This is an inadequate as repair material and construction products that have been widely used for years recently. To overcome these problems, polymer researchers and engineers have used shrinkage-reducing additives, which are usually specific thermoplastic polymers. The objective of this study is to evaluate the effects of shrinkage-reducing additive on the curing shrinkage and strengths of UP mortar. UP mortars are prepared with expanded polystyrene(EPS) ratio in styrene monomer(SM), (EPS/PS, PS=EPS+SM), and the ratio of total polystyrene resin(PS) to UP resin, (PS/UP). And it is tested for viscosity of UP resin, slump-flow, working life, flexural and compressive strengths, and curing shrinkage tests. From the test results, viscosity of resin for UP mortar increases with increasing PS content. Curing shrinkage of UP mortar is considerably smaller than that of plain UP mortar, nevertheless, reduction in the strengths is not recognized according to adding PS resin. In this study, we can obtain the optimum mix proportions of UP mortar using PS resin which made of waste expanded polystyrene.

• Journal of the Korea Concrete Institute
• /
• v.23 no.4
• /
• pp.441-448
• /
• 2011

In this study, experimental tests of chemical and autogenous shrinkage were performed to evaluate the early age shrinkage behaviors of ultra high performance cementitious composites (UHPCC) with various replacement ratios of silica fume (SF), shrinkage reducing agent (SRA), expansive admixture (EA), and superplasticizer (SP). Starting time of self-desiccation, was analyzed by comparing the setting times and the deviated point of chemical and autogenous shrinkage strains. The test results indicated that both SF and SRA augment the early age chemical shrinkage, whereas SP delays the hydration reaction between cement particles and water, and reduces chemical shrinkage. About 49% of autogenous shrinkage was depleted by synergetic effect of SRA and EA. The hardening of UHPCC was catalyzed by containing EA. Self-desiccation of UHPCC occurred prior to the initial setting due to the high volume fraction of fibers and low water-binder ratio (W/B).

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.11a
• /
• pp.919-922
• /
• 2008

This paper reports the physical and shrinkage properties of concrete using expansive additive(E) and three shrinkage reducing admixtures(SRA1, 2, 3) in order to reduce shrinkage of concrete. For the properties of fresh concrete, the use of SRA1, 2, 3 results in a increase in fluidity and decrease in the dosage of super plasticizer as much as 0.05$\sim$0.1%. And For the properties of hardened concrete, the use of SRA1, 2, 3 results in a decrease in compressive, tensile and flexural strength slightly. For drying shrinkage properties, the use of SRA3 is the most effective for reduction of shrinkage, and the next best way to reduce shrinkage is combination with expansive additive(E) and shrinkage reducing admixture(SRA) or the using of expansive additive(E).

• Journal of the Korea Concrete Institute
• /
• v.18 no.4 s.94
• /
• pp.553-558
• /
• 2006

In this study, fluorine-silicate hybrid type crack reducing agent(FS) consisted of fluorine and silicate compounds applied to concrete mix(specification : 25-30-18) between 0.5% and 2.0% at intervals of 0.5% based on cement weight. Experiments for material properties of concrete such as slump, air content and bleeding with elapsed time were performed. Experiment and elucidation for shrinkage crack resistance as well as adiabatic hydration temperature were also carried out. It was appeared that FS addition contributed to lower bleeding and hydration temperature without disturbance of fresh properties of concrete such as slump and air content compared to non-added concrete. Especially, shrinkage crack resistance of concrete resulted from plastic and drying shrinkage could be effectively reduced by the addition of FS ranging from 1.0% to 1.5%.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.6 no.3
• /
• pp.110-117
• /
• 2011

This study investigated possibilities for a new reducing shrinkage method of soybean oil(SO) and waste oil(WO) to compare with shrinkage reducing agent(RS) and expansion additive(EA). There was no big difference to flow, air contents, and compressive strength of plain to use SO and WO. For the reducing shrinkage performance, SO and WO was more effective than RS and EA, because their fatty acid reacted with calcium hydroxide of concrete to turn soap. For the pore distribution by porosimter, $0.01{\sim}0.1{\mu}m$ pores of SO and WO were 0 ml/g, and $10{\sim}100{\mu}m$ also remarkably lower than any others. In these results, it inferred that they filled up capillary pore and mitigated autogenous shrinkage by their saponification of their fatty acid and calcium hydroxide.

• Journal of the Korea Concrete Institute
• /
• v.18 no.2 s.92
• /
• pp.205-211
• /
• 2006

The objective of this study was to evaluate the durability of low shrinkage high performance concrete(LSHPC), which was combined with expansive additives and shrinkage reducing admixtures. We tested for not only LSHPC but also high performance concrete(HPC) and normal concrete(NC) to be compared with the durability of LSHPC. HPC was made in the same water-binder ratio of LSHPC without expansive additives and shrinkage reducing admixture. As a result, it was found that LSHPC had higher compressive and tensile strength than that of HPC. LSHPC showed more excellent performance than HPC and NC in the case of resistance to chloride ion penetration and resistance to carbonation and also showed nearly 100 durability factor in the freeze-thawing test with 500 cycles. From the examination about the watertightness and the pore distribution, it was found that the durability of LSHPC was improved because its hardened cement paste is organized closer. So we can conclude that when LSHPC is applied to structures in field, it is possible to reduce the shrinkage and crack in concrete and improve the durability.

• Journal of the Korea Concrete Institute
• /
• v.18 no.5 s.95
• /
• pp.631-637
• /
• 2006

In this study, fundamental properties such as fresh and hardened performance of concrete mix(specification : 25-24-18) added fluorine-silicate hybrid based crack reducing agent(FS) were measured. Addition of FS ranged from 0.5% to 2.0% at intervals 0.5% based on cement weight. Adequate dosage(0.5%) of FS derived from basic properties measurements applied and compared resistance for shrinkage crack. The permeability of concrete in the absence(24-S-0.0) and presence(24-S-0.5) of evaluated at a mock-up sized concrete. Concrete added FS improved resistance for shrinkage crack and consequently crack number, length and area decreased to $50{\sim}74.4%$ compared non-added. As well, by the addition of FS, the resistance for permeability and penetration depth to concrete surface region increased 67% and 40%, respectively. Therefore it was confirmed that shrinkage crack resistance and permeability of concrete could be improved by the addition of FS.

• International Journal of Highway Engineering
• /
• v.11 no.2
• /
• pp.99-109
• /
• 2009

Fine-size exposed aggregate portland cement concrete pavements (FEACP) have surface texture of exposed aggregate by removing upper 2$\sim$3mm mortar of surface of which curing is delayed by using delay-setting agent. FEACPs have advantages of maintaining low-noise and adequate skid-resistance level during the performance period than general portland cement concrete pavements. It is necessary to ensure the durability environmental loading to prevent unexpected distress during the service life of FEACP. In the process of curing, volume change accompanied change in by moisture and temperature could be an important cause of crack in concrete to construct for successful FEACP, The use of chloride containing deicer may accelerate defects of concrete pavement, such as crack and scaling. This study aim to evaluate environmental loading resistance of FEACP, based on the estimation of shrinkage-crack-control-capability by moisture evaporation and scaling by deicer in freeze-thaw reaction.