Alkali-activated slag foamed concrete with lightweight glass aggregates

Paper i proceeding, 2015

Alkali activated slag foamed concrete (AASFC) is considered as an environmentally friendly lightweight cementitious material alternatives to similar materials based on Portland cement. However, due to the lack of understanding of important properties, the use of this type of materials is still very limited. The purpose of the study is to design alkali-activated slag foam concretes with bulk densities in the range of 300- 1100 kg m-3 and thermal conductivities ranging from 0.1 to 0.35 W m-1 K-1. Properties, such as consistency, mechanical strength, drying shrinkage and thermal conductivity, were investigated. In addition, two types of lightweight glass aggregates were used for improving the properties and to reduce the amount of paste in the material. The results shows that the wet bulk density of the AASFC is consistent with the designed value if prepared with suitable volume of foam and water/slag ratio. For these materials, the compressive strength is between 0.1 and 7 MPa and the thermal conductivity ranges from 0.09 to 0.35 W m-1K-1. However, the foam concretes display quite huge drying shrinkage. Furthermore, it is shown that the use of lightweight glass aggregates (LGA) in AASFC can reduce the amount of paste by 50% (by volume) without any negative influence on mechanical properties, although the concretes showed poorer flowability. The aggregates are also beneficial to lower the thermal conductivity and to improve the resistance of drying shrinkage. The expanded LGA showed better effect on both the consistency and the hardened properties of the material than the simply foamed LGA.