Influence of Rheological Properties of Lightweight Foamed Concrete on Preventing Foam Collapse

경량 기포 콘크리트의 레올로지 특성이 소포억제에 미치는 영향

Abstract

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.

본 연구에서는 경량 기포 콘크리트의 부피 안정성을 확보하기 위해 소포를 저감시킬 수 있는 요소들을 레올로지 특성을 연계하여 분석하였다. 실험계획으로는 비빔시간, 물-결합재비, 증점제, 기포제, 폐지 첨가량에 대한 변화로 각 요인을 통해 실험하였다. 먼저 과도한 비빔과 기포제의 첨가량에 의해 발생한 다량은 기포는 슬러리 내에서 불안정한 상태로 존재하여 침하를 발생시킨다. 특히 기포제의 경우 계면활성제로써 물에 영향을 미치므로 배합 계획 시 물에 대한 질량비로 계획해야할 것으로 판단된다. 또한 레올로지 특성을 통해 경량 기포 콘크리트의 소성점도와 소포량이 반비례관계를 가진 것을 확인할 수 있었다. 따라서 본 연구의 결과는 경량 기포 콘크리트의 소포를 저감시킬 수 있는 요소들을 분석함으로써 경량 기포 콘크리트의 배합 조건에 대한 기초적인 자료를 제공될 것으로 판단된다.

Fig. 1. Rheological test setting

Fig. 2. Influence of mixing time on slurry and dry densities of lightweight foamed concrete

Fig. 3. Influence of W/B on slurry and dry densities of lightweight foamed concrete

Fig. 4. Influence of viscosity agent on slurry and dry densities of lightweight foamed concrete

Fig. 5. Influence of foaming agent on slurry and dry densities of lightweight foamed concrete

Fig. 6. Influence of waste paper on slurry and dry densities of lightweight foamed concrete

Fig. 7. Shape of foam on the surface of the specimen according to the amount of the waste paper

Fig. 8. The relationship between air content in the slurry condition and settling depth

Fig. 9. The relationship between plastic viscosity and settling depth

Fig. 10. The relationship between ratio of SLS/Water and settling depth

Table 1. Experimental plan

Table 2. Physical properties of normal portland cement

Table 3. Result value of plastic viscosity, ratio of foaming agent/water and settling depth by experimental factor