Alkali-Silica-Reaction (ASR) of glass aggregates in dry-mix concrete block

Due to the lack of a glass manufacturing industry, waste glass beverage bottles generated in Hong Kong are normally disposed of at landfills. The use of crushed waste glass beverage bottles as fine aggregates in concrete... [ view full abstract ]

Due to the lack of a glass manufacturing industry, waste glass beverage bottles generated in Hong Kong are normally disposed of at landfills. The use of crushed waste glass beverage bottles as fine aggregates in concrete products is an effective method to recycle the waste glass and conserve the depleting river sand resources. However, Alkali-Silica-Reaction (ASR) of glass aggregates impairs the use of glass aggregates in concrete. This paper reports a study on investigating the mechanism of ASR of the dry-mix glass concrete blocks and related mechanical properties. The ASR expansion of the dry-mix glass concrete blocks using up to 100% waste glass cullet as fine aggregates all met the limited value specified by ASTM C1260 accelerated mortar bar test. The reduction of compressive strength of the all the dry-mix glass concrete blocks was less than 6% after the ASR test. Scanning electron microscopy (SEM) studies of the dry-mix glass concrete blocks before and after the accelerated mortar test revealed that initial cracks were present inside the glass aggregates due to the fabrication process of the dry-mix concrete product which used a compaction moulding method. After the ASR test, the ASR gel was formed both in the original internal cracks of the glass particles and between the cement paste and the glass aggregates. But no crack was observed in the cement paste due to the presence of larger voids in the dry-mix concrete product which could accommodate the formed ASR gel. This is contrary to the excessive expansion and cracking that normally occur in glass concrete products produced by the traditional we-mix method. The dry-mix glass concrete production method paves a new way to allow the wider use of waste glass in concrete products.