• Land and Housing Review
• /
• v.1 no.1
• /
• pp.35-42
• /
• 2010

Most of the dredged sand generated from the sewage pipe maintenance project and the government's four-river project are disposed depending on abandonment and filling-up. This is caused by the lack of related recycling technology using dredged sand appropriately and high absorption rate and micro-particles of dredged sand producted from existing sand production system. Thus, this study carried out a quality assessment for the dredged sand produced through the optimum washing and sorting system supplementing problems of existing dredged sand production system as a part of research to examine performance of removing micro-particles and foreign substances. As a result of the assessment, the dredged sand produced through the cleaning and sorting system showed a wide quality improvement effect in absorption rate, 0.08 mm sieve pass amount, clay lump volume and organic impurity content, and it turned out to satisfy both the quality standards of this study, KS F 2573(recycled aggregate for concrete) and KS F 2526(aggregate for concrete) so it could be confirmed that it would be able to be used as an aggregate for concrete in the future.

• Journal of the Korea Institute of Building Construction
• /
• v.24 no.4
• /
• pp.393-402
• /
• 2024

The Korean Industrial Standard(KS) KS F 2527("Aggregates for Concrete") does not explicitly define criteria for clay mineral content in aggregates. This lack of clear quality standards and testing methodologies is further compounded by a scarcity of relevant research within both academic and industrial spheres. Consequently, the construction industry, encompassing both aggregate production and utilization, often overlooks the management of clay mineral content due to its perceived economic implications. This study addresses this gap by investigating the current state of regulations concerning clay mineral content in aggregates, exploring the causes of its occurrence, and evaluating its impact on concrete performance. The chemical composition of the clay minerals was determined to primarily consist of Al₂O₃, Fe₂O₃, and SiO₂, which are commonly found in clay. X-ray diffraction(XRD) analysis revealed that the predominant clay minerals were montmorillonite and illite, both known for their high absorption capacity. An examination of domestic and international standards for clay mineral content in aggregates demonstrated that the density and absorption rate specifications outlined in KS F 2527("Aggregates for Concrete") only offer indirect estimations of clay mineral levels. Furthermore, the investigation into the influence of clay mineral content on concrete performance suggests that a higher clay mineral content necessitates a corresponding increase in the unit quantity of aggregates to maintain adequate workability. This, however, has a detrimental effect on the compressive strength of the concrete.

• Journal of the Korea Institute of Building Construction
• /
• v.14 no.1
• /
• pp.21-28
• /
• 2014

The purpose of this study is to investigate the mechanical properties and carbonation resistance of concretes using lightweight aggregate coated surface finishing materials. To evaluate the mechanical properties and carbonation resistance of concrete, slump, air amount, air-dried unit volume weight, compressive strength, and carbonation depth are tested. In terms of the unit volume weight of concrete, air-dried unit volume weight of concrete using coating lightweight aggregate was measured as $1,739{\sim}1,806kg/m^3$. When using coating aggregate, compressive strength of concrete at 28 days was measured as much as 82.7~95.9% of the compressive strength using non-coating aggregate. It is found that compressive strength tends to decrease with coating lightweight aggregate. However, all concretes using coating lightweight aggregate except O-LWAC satisfied the criteria for 28-day compressive strength suggested in KS. The measurement of carbonation depth when the water-repellent agent was used found that carbonation depth was reduced by as much as 2.6~6.1%. On the other hand, when using polymer waterproof agent, carbonation depth was reduced by as much as 8.6~12.0%. Consequently, to improve carbonation resistance, polymer waterproof agent was more effective than water-repellent agent. In particular, epoxy showed the most outstanding performance.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.3
• /
• pp.246-252
• /
• 2021

The basic properties and volume stability of the ultra-rapid setting cement mortar containing low-quality recycled aggregate with a higher water absorption and lower specific gravity than relavent Korea Standard were experimentally confirmed. The mix proportion without recycled aggregate followed that of the general repair mortar used in the fields. 15% and 30% of the fine aggregate was substituted by the recycled aggregate in the mixtures with and without latex emulsion, and properties and characteristics of the mortar including mortar flow, setting time, compressive and flexural strength, and linear deformation under sealed and unsealed conditions were evaluated. It was confirmed that when low-quality recycled aggregate was used by 30%, there were risks of decrease in the early-age strength by up to 50% within 24h and increases in drying shrinkage by up to 2 times for 2 weeks compared to the the mixtures without the recycled aggregate.

• Resources Recycling
• /
• v.15 no.2 s.70
• /
• pp.24-31
• /
• 2006

The duality of recycled fine aggregate (RS) which was produced at the waste concrete crushing was investigated. The compressive strength, flexural strength and absorption of mortar utilized with RS were examined. It was evaluated on the application of RS as precast concrete aggregate. The density and absorption of RS were $2.31g/cm^3$ and 8.07% respectively, the quality of RS was satisfied with the criterion of KS F 2573 type 2. The maximum 28days compressive strength of mortar mixed with blended cement MRS1, MRS2 and MRS3 were developed with 15.8, 27.4 and 48.7MPa respectively, in condition to curing temperature $40^{\circ}C$ and water-cement ratio 37.5%. When blended cement MRS1 and MRS2 were used, the maximum flexural strength of mortar was developed at curing temperature $40^{\circ}C$ and water-cement ratio 35.0%. When blended cement MRS3 was used, the maximum flexural strength of mortar was developed at curing temperature $40^{\circ}C$ and water-cement ratio 37.5%. The absorption of mortar mixed with blended cement MRS1, MRS2 and MRS3 were indicated the range of $8.3{\sim}7.3%,\;6.5{\sim}8.5%$ and $3.5{\sim}6%$ respectively. Therefore, when the ratio of blended cement and RS is appropriately centre]led, it would be expected that MRS1, MRS2 and MRS3 will be able to apply the variable low strength, medium strength and high strength precaste concrete.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.18 no.2
• /
• pp.117-125
• /
• 2014

This paper examines the fundamental properties of alkali-activated slag cement (AASC) activated by sodium hydroxide (NaOH). The water to binder (W/B) ratio was 0.4 and 0.5. And concentration of activator were 2M and 4M. Five mix design of each W/B ratios was considered. The N0 mixture was KS L 5109 method and N1~N4 were varied in different mixing time, mix step and entering points of fine aggregate. Test results clearly showed that the flow value, strength and drying shrinkage development of AASC were significantly dependent on the entering point of fine aggregate. The flow value tended to decreases with delaying entering point of fine aggregate. The compressive strength and flexural strength increases with delaying entering point. Moreover, the XRD analysis confirmed that there were sustain these results. The drying shrinkage increases with delaying entering point of fine aggregate. Futhermore, a modified mixing method incorporating all hereby experimentally derived parameters, is proposed to improvement the physical properties of AASC.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.2 no.2
• /
• pp.137-144
• /
• 2014

The PHC pile utilizing the air-cooled blast-furnace slag as coarse aggregate was studied. This research was progressed with the range from the indoor mixing design evaluation into the actual goods production. The physical properties of the PHC pile are determined to satisfy through the appropriate mixing design adjustments. However, it should eliminate the aggregates including CaO and MgO in SG when it utilize in an AC (autoclave) type manufacturing process. It satisfied the bending moment, shear strength, and compressive strength of KS F 4306 except the surface states of the pile.

• Applied Chemistry for Engineering
• /
• v.25 no.4
• /
• pp.409-413
• /
• 2014

This study was carried out to design the optimum mixing ratio of aggregate, cyclic aggregate, and binder (moisture, emulsified asphalt, and emulsion type additives) and produce recycling cold asphalt paving mixture satisfying site work standard. The cyclic aggregate satisfying KS F 2572 was collected from waste asphalt by adequate processing. As the moisture content increased, the shearing strength was decreased. The maximum marshall stability was shown at the 3.0 wt% moisture content. So the optimum moisture content was 3.0 wt%. The marshall stability and flow value with the amount of emulsified asphalt was satisfied in the range of 0.5~2.5 wt%, and the porosity was satisfied in the range of 0.7~2.5 wt%. So the optimum amount of emulsified asphalt was 1.6 wt%. The optimum amount of emulsion type additive was 0.1 wt% in the light of marshall stability and degree of saturation of recycling cold asphalt mixture.

• Journal of Power System Engineering
• /
• v.17 no.2
• /
• pp.108-113
• /
• 2013

In this study, lightweight aggregate was made from basalt stone powder sludge. Clay and glass powder were respectively added from 0 to 20 wt% and from 0 to 100 wt%. The glass powder helped to form glassy phase which trapped generating gas in the materials. $CaCO_3$ helping bloating process was added from 0 to 10 wt%. It was possible to produce lightweight aggregate at range from $1150^{\circ}C$ to $1200^{\circ}C$. The specimen was heated in furnace at 1100, 1150 and $1200^{\circ}C$ for 15 min, respectively, to sinter aggregates. Chemical composition of materials were determined, and characteristics were analyzed, including specific gravity, water absorption. Lightweight aggregate which was heated at $1200^{\circ}C$ had specific gravity of $0.53g/cm^3$, water absorption of 3.08%, and this value satisfied KS L 8551 standard.

• Journal of Advanced Engineering and Technology
• /
• v.11 no.4
• /
• pp.295-301
• /
• 2018

In this study, freezing-thawing resistance of concrete using steel slag as coarse aggregate(steel slag concrete) from Gwangyang Iron Co. was estimated to offer basic data for utilization of much more steel slag. Freezing-thawing test of concrete using crushed stone as coarse aggregate(crushed stone concrete) whose compressive strength and air contents are as close as possible to those of the steel slag concrete was performed. Because they are main two factors that affect of freezing-thawing resistance. The test was carried out up to 400 cycles according to KS F 2456. The compressive strength and weight of two concretes were measured and compared. As a result, the freezing-thawing resistance of steel slag concrete curing in water was almost the same with that of crushed stone concrete. But the resistance of steel slag concrete curing in air dry condition was weaker than that of crushed stone concrete. Also, the steel slag concrete which has more than 60% of W/C ratio showed much more surface degradation when compared to crushed stone concrete.