Frost Resistance Number to Assess Freeze and Thaw Resistance of Non-Autoclaved Aerated Concretes Containing Ground Granulated Blast-Furnace Slag and Micro-Silica.

Eldar Sharafutdinov,Dichuan Zhang,Chang-Seon Shon,Saltanat Bagitova,Chul-Woo Chung,Jong Kim

doi:10.3390/ma12244151

Abstract

Aerated concrete (AC), such as cellular concrete, autoclaved aerated concrete (AAC), and non-autoclaved aerated concrete (NAAC), having excellent insulation properties, is commonly used in buildings located in cold regions, such as Nur-Sultan in Kazakhstan, the second coldest capital city in the world, because it can contribute to a large energy saving. However, when the AC is directly exposed to the repeated freeze and thaw (F-T) cycles, its F-T resistance can be critical because of lower density and scaling resistance of the AC. Moreover, the evaluation of the F-T resistance of the AC based on the durability factor (DF) calculated by using the relative dynamic modulus of elasticity may overestimate the frost resistance of the AC due to the millions of evenly distributed air voids in spite of its weak scaling resistance. In the present study, the F-T resistance of NAAC mixtures with various binary or ternary combinations of ground granulated blast-furnace slag (GGBFS) and micro-silica was assessed mainly using the ASTM C 1262/C1262M-16 Standard Test Method for Evaluating the Freeze-Thaw Durability of Dry-Cast Segmental Retaining Wall Units and Related Concrete Units. Critical parameters to affect the F-T resistance performance of the NAAC mixture such as compressive strength, density, water absorption, air–void ratio (VR), moisture uptake, durability factor (DF), weight loss (Wloss), the degree of saturation (Sd), and residual strength (Sres) were determined. Based on the determined parameter values, frost resistance number (FRN) has been developed to evaluate the F-T resistance of the NAAC mixture. Test results showed that all NAAC mixtures had good F-T resistance when they were evaluated with DF. Binary NAAC mixtures generally showed higher Sd and Wloss and lower DF and Sres than those of ternary NAAC mixtures. It was determined that the Sd was a key factor for the F-T resistance of NAAC mixtures. Finally, the developed FRN could be an appropriate tool to evaluate the F-T resistance of the NAAC mixture.

Highlights

Aerated concrete (AC) originated in Europe as one of the widely used types of lightweight concrete (LWC)
The high porous characteristics of the AC give it excellent insulation properties contributing to a reduction in the energy consumption related to heating, ventilation, and air conditioning (HVAC) systems suited for severe environments [6,7,8]
With a decrease in density and an increase in the void ratio, the water absorption increases [12]. These properties play a critical role in the durability performance of the non-autoclaved aerated concrete (NAAC) when it is mainly exposed to wet and freeze and thaw (F-T) environmental conditions

Summary

Introduction

Aerated concrete (AC) originated in Europe as one of the widely used types of lightweight concrete (LWC). Aluminum powder reacts with alkalis in the cement and forms millions of evenly distributed and uniformly sized small air bubbles in the concrete matrix required for the generation of the porous structure [2]. As any LWC, the AC, due to the unique highly porous structure, possesses better sound absorption caused by the converted air-borne sound energy in the minute channels of the concrete [3,4,5]. The high porous characteristics of the AC give it excellent insulation properties contributing to a reduction in the energy consumption related to heating, ventilation, and air conditioning (HVAC) systems suited for severe environments [6,7,8]. In order to overcome these shortcomings and obtain a good quantity of pores and evenly distributed pores, an autoclaved curing under high pressure and temperature is required [9]

Results

Discussion

Conclusion