Water absorptivity and frost resistance performance of self-ignition coal gangue autoclaved aerated concrete

Xinyu Cong,Zhaojia Wang,Yiqiu Tan,Tianyong Huang,Shuang Lu

doi:10.1186/s43065-021-00031-4

Abstract

Self-ignition coal gangue (SCG) used as one of precursors to fabricate autoclaved aerated concrete (AAC). Aiming at studying water absorptivity and frost resistance performance of SCG-based AAC (SCGAAC), three-period water absorption tests and freeze-thaw tests were carried out and the corresponding results were recorded and analyzed. In order to modify the water absorptivity of SCGAAC, foam stabilizer was applied to adjust pore structure while calcium stearate was expected to change hydrophilic feature of SCG. It was demonstrated that the compressive strength of SCGAAC containing foam stabilizer or calcium stearate declined at different levels. For water absorption, foam stabilizer failed to decrease the water content and even increased water absorption rates. Calcium stearate controlled water absorption rate successfully although the ultimate water content hardly reduced. All of the SCGAAC samples exhibited intact appearance after 50 freeze-thaw cycles and showed excellent frost resistance performance. Three models were proposed to predict water absorptivity and frost resistance performance of SCGAAC and the corresponding prediction results matched test resulted well.

Highlights

Autoclaved aerated concrete (AAC) has been commonly used as construction material by virtue of its functional performance [1,2,3,4,5,6], in particular, thermal insulation and energy efficiency [7,8,9]
The water absorptivity WR can be calculated as Eq (1): Fig. 1 Super depth of field microscope (SDFM) images for pore characterization of SCG-based AAC (SCGAAC): a) black-painting slice vs. original slice; b) pore-filling slice; c) capture image thawing cycle contained two stages: the water-soaked samples froze in air at − 20 ± 2 °C for 4 h; and the temperature rose to 20 ± 2 °C and the samples immerged in water for 4 h to thaw
Pore structure of SCGAAC According to the captured pictures of SCGAAC slices, three main pore parameters were computed by the OLYMPUS Stream software connected with the SDFM, including porosity, pore-size distribution and average length-width ratio (ALwR) of the pores

Summary

Introduction

Autoclaved aerated concrete (AAC) has been commonly used as construction material by virtue of its functional performance [1,2,3,4,5,6], in particular, thermal insulation and energy efficiency [7,8,9]. Two different chemical agents were used to improve SCGAAC performance on water absorption and frost resistance. A foam stabilizer (F) was used to reduce bubble cracking during the stirring process and optimize pore structure of hardened AAC. In order to improve the pore structure of AAC, the foam stabilizer was applied to avoid bubbles merging and to reduce interconnected pores. The water absorptivity WR can be calculated as Eq (1): Fig. 1 Super depth of field microscope (SDFM) images for pore characterization of SCGAAC: a) black-painting slice vs original slice; b) pore-filling slice; c) capture image thawing cycle contained two stages: the water-soaked samples froze in air at − 20 ± 2 °C for 4 h; and the temperature rose to 20 ± 2 °C and the samples immerged in water for 4 h to thaw. The compressive strength and mass change were recorded after the SCGAAC samples were subjected to 50 freezing and thawing cycles

Results and discussion

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Conclusions