• Journal of the Korean Recycled Construction Resources Institute
• /
• v.6 no.4
• /
• pp.304-310
• /
• 2018

The aim of the research is to provide possibility of quality controlling by rheological properties for lightweight foamed concrete. The lightweight foamed concrete achieves its low density by containing air bubbles (foam) produced during the mixing process. Therefore, containing foamed volume during setting period is critical for the securing the performance as an insulating material. In this research, regarding foam collapse during the setting period, rheolgocial properties of fresh state lightweight foamed concrete were assessed to get its relationship with volume stability, or foam stability. For the experiment regarding foaming factors including mixing time, mix design of contents for materials, rheological properties of fresh state lightweight foamed concrete were tested with its density and settling depth. Based on the settling depth with various factors, relationship with rheological properties was analyzed, and especially, close relationship of plastic viscosity and settling depth was found. Therefore, from the results of this research, it is considered to contribute on suggesting a new approach of quality controlling for lightweight foamed concrete using rheological test method.

• Journal of the Korea Institute of Building Construction
• /
• v.12 no.1
• /
• pp.22-30
• /
• 2012

Four types of foaming agents, including Alcohol Ethoxy Sulfate (AES), Alpha Olefin Sulfonate (AOS), Vegetable Soap (VS), and Fe-Protein (FP), are widely used in the construction field. These have different surface tensions and viscosities in water of the same concentration, affecting the flow speed of liquid, size and distribution of foam, and foam stability. However, there is a lack of data regarding the properties of foam concrete using various foam agents. The purpose of this study is to investigate influence of foaming agents on the properties of foamed concretes with various densities. We find that the foaming agent type has little effect on the density, compressive strength, and thermal conductivity of foam concrete, but considerably affects the unit weight of foam, flow and flexural strength of foamed concrete. While almost all properties of foam concrete are affected by density in fresh or hardened state, the potential energy changed by slurry density and the viscosity of foam are dominant factors in the flowability of foam slurry.

• Advances in concrete construction
• /
• v.15 no.3
• /
• pp.179-190
• /
• 2023

The effect of glass fibres (GF) and polypropylene fibres (PPF) on the fresh properties and mechanical properties of lightweight concrete (LWC) exposed to high temperatures is investigated in this study. In this study, fifteen LWC mixtures were carried out in three different groups reinforced with PPF or GF fibers by 0%, 0.2%, and 0.4% by volume of concrete. The first group included aluminum powder (AP) as an air agent at 0.03% with the normal weight coarse aggregate (NWCA) by 100% of the weight of coarse aggregate. In the second group, 33% of the NWCA weight was replaced by lightweight coarse aggregate (LWCA). In the third group, 67% of the NWCA weight was replaced by LWCA. The slump, unit weight, Compressive strength (CS), tensile strength (TS), and flexural strength (FS) were examined. For two hours, the CS and FS were subjected to elevated temperatures of 200℃, 400℃, and 600℃, in addition to microstructure analysis of concrete. In comparison to the reference mixture, the fresh properties and bulk density of LWC decreased with the use of the air agent or the replacement of 67% of the NWCA with LWCA. As a result of the fiber addition, both the slump test and the bulk density decreased. The addition of fibers increased the CS; the highest CS was 38.5 MPa when 0.4% GF was added, compared to 28.9 MPa for the reference mixture at the test age of 28 days. In addition, flexural and TS increased by 53% and 38%, respectively, for 0.4% GF mixes. As well as, adding 0.4% GF to LWC maintained a higher CS than other mixtures.

• Advances in concrete construction
• /
• v.5 no.6
• /
• pp.575-586
• /
• 2017

The disposal of polythene waste and fly ash is causing serious threat to the environment. Aim of this study is to decrease environmental pollution by using polythene waste and fly ash in concrete. In this study, cement was partially replaced with 0%, 5%, 10%, 15% and 20% fly ash (by weight) and plastic waste was added in shredded form at 0.6% by weight of concrete. The specimens were prepared for the concrete mix of M25 grade and water to cementitious material ratio (w/c) was maintained as 0.45. Fresh concrete property like workability was examined during casting the specimens. Hardened properties were found out by carrying out the experimental work on cubes, cylinders and beams which were cast in laboratory and their behavior under test were observed at 7 & 28 days for compressive strength and at 28 days for density, flexural strength, dynamic modulus of elasticity, abrasion resistance, water permeability and impact resistance. Overall results of this study show that addition of 0.6% (by weight of the concrete) plastic waste with 10% (by weight of cement) replacement of cement by fly ash result an improvement in properties of the concrete than conventional mix.

• Advances in concrete construction
• /
• v.12 no.6
• /
• pp.461-467
• /
• 2021

Polyethylene-terephthalate (PET) from bottle waste and linear low-density polyethylene (LLDPE) from barrels and tanks waste are widely available and need to be recycled. Recycling them in concrete and mortar is an alternative solution for their disposal. In this study various quantities of sand (5%, 10%, 15% and 20%) were substituted by powder from LLDPE waste. In addition, PET waste fibers (corrugated, straight) were added to the mortar with different percentages (0.5%, 1%, 1.5% and 2%) of cement mass. This paper evaluate the mechanical and physical properties of the composites in fresh (workability, air content and density) and hardened state (compressive and flexural strength, water absorption and total shrinkage). From the experimental results, it can be concluded that the strengthening in tensile of the mortar with plastic waste corrugated fibers is improved. Other important results are that the water absorption and the density rate are less than that of the ordinary mortar.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1993.04a
• /
• pp.34-39
• /
• 1993

Recently inappropriate aggregates are used as a raw material for ready-mixed concretes, due to the shortage of natural aggregate resources and the prohibition of their extraction for the environmental protection. We, therefore, have conducted experiments to obtain some knowledge of properties of domestic aggregates and to investigate subsequent changes in the properties of the fresh and hardened concretes. To this end, aggregates currently used in 13 domestic ready-mixed concrete plants were collected. Most of aggregate used in this experiment satisfied the KS in density and unit weight. But some of the aggregates have the particle size distribution that can effect bad influence on concrete. In this experiment the aggregates are found to have a bad particle size distribution, resulting in high amount of a unit water content and a unit cement content in concrete.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2011.11a
• /
• pp.199-200
• /
• 2011

Absorption of lightweight aggregate affects the properties of fresh and hardened concrete, so care must be taken. In this study, according to KS F 2533 absorption is measured to aggregate size, submerged time, holding time and practically ways to maintain a constant absorption was to seek. The findings for quality control of the lightweight aggregate concrete mixture is saturation of the surface-dry aggregate humidity 100% after 24 hours immersion in the environment has been stored for more than two days to absorb the state was able to define. Dry density at the surface of the lightweight aggregate and lightweight concrete mix design and placement is possible for it to apply.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.11a
• /
• pp.861-864
• /
• 2006

This study investigates the properties of light weight foamed concrete with variances in incorporating ratio of cement kiln dust(CKD). Test showed that an increase of CKD incorporating ratio decreased the fluidity of fresh concrete and increased the unit weight. A sinking depth of specimens incorporating CKD decreased, compared with that of control. As for the compressive strength, it firstly increased and then slightly decreased when incorporated CKD. Tensile strength values were similar to the values of compressive strength, but the ratio of comp. to tens. strength increased. Appearances density of specimens were all raged in KS and the thermal conductivity was also satisfied in KS; less than 0.05-0.160W/($m{\cdot}k$).

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.30 no.6A
• /
• pp.573-580
• /
• 2010

This paper presents the development of self-consolidating concrete (SCC) using lightweight aggregates. SCC using Lightweight aggregate properties have been evaluated in terms of flowability, segregation resistance and filling capacity of fresh concrete as per the standards of the Japanese Society of Civil Engineering (JSCE). The measurement of the mechanical properties of hardened SCC using lightweight aggregate, including compressive strength, splitting tensile strength, elastic moduli and density, as well as its dry shrinkage and carbonation properties were also carried out. The characteristics of SCC using lightweight aggregate at the fresh state showed that as the use of the lightweight aggregate, the flowability improves without exception of Mix No. 9 but the segregation resistance tends to decrease without exception of Mix No. 3, 4 and 5. The 28 days compressive strength of the SCC using lightweight aggregate was found to be 30 MPa or higher. The relationship between the compressive strength and the splitting tensile strength was found to be similar to the expression presented by CEB-FIP, and the relationship between the compressive strength and the elastic moduli was found to be similar to the expression suggested by ACI 318-08 which takes into consideration the density of concrete. The density of the SCC using lightweight aggregate decreased by up to 26% compared to that of the control SCC. Also, The dry shrinkage and carbonation depth of the SCC using lightweight aggregate increased compared to that of the control SCC.

• Journal of the Korea Concrete Institute
• /
• v.17 no.6 s.90
• /
• pp.923-930
• /
• 2005

This paper was to evaluate the high strength lightweight self-compacting concrete(HLSCC) manufactured by Nan-Su, which main factor, Packing Factor(PF) for mixing design, has been modified and improved. We have examined HLSCC performance at its fresh condition as well as its mechanical properties at the hardened condition. The evaluation of HLSCC fluidity has been conducted per the standard of second class rating of JSCE, by three categories of flowability(slump-flow), segregation resistance ability(time required to reach 500mm of slump-flow and time required to flow through V-funnel) and filling ability(U-box test) of fresh concrete. The compressive strength of HLSSC at 28 days has come out to more than 30MPa in all mixes. The relationship between the compressive strength-splitting tensile strength and compressive strength-modulus of elasticity of HLSSC were similar those of typical lightweight concrete. Compressive strength and dry density of HLSCC at 28 days from the multiple regression analysis resulted as $f_c=-0.16LC-0.008LS+50.05(R=0.83)\;and\;f_d=-3.598LC-2.244LS+2,310(R=0.99)$, respectively.