ALKALI SILICA POTENTIAL IN FLY ASH-BASED GEOPOLYMER CONCRETE
Sikandar Hayat, Ali Mutaza Rasool, Asif Hameed
Alkali-Silica Reaction (ASR) is a chemical reaction between hydroxyl ions present in pore solution within
the concrete matrix and reactive silica of the aggregates used in concrete. ASR is harmful which could lead
to strength loss, cracking, volume expansion, and even potential failure of the structures. This research is
intended toinvestigate ASR potential in geopolymer concrete using locally available aggregates from
different querries. Different specimens were prepared using class F fly ash as a binder and sodium
hydroxide and sodium silicate solution as an alkaline activator. ASTM C 1260 was used to explore ASR
potential by measuring the length change in expansion bars up to 150 days. Cubes and prisms were
prepared to find a change in compressive strength and modulus of rupture respectively. For comparison,
OPC samples were also prepared. The experimental results showed that expansion results were far less
than ASTM C 1260 standard limits at 14 and 28 days as compared to OPC samples that showed ASR
expansion. Geopolymer has shown very little expansion (less than 0.025% at 28 days) as compared to
OPC (greater than 0.2% at 28 days) under harsh conditions, especially in the case of the Taunsa and Wana
sources. In terms of compressive and flexural strength, the GPC samples showed an increase from 15%
to 25% t in compression and 5% to 15% in flexure respectively under harsh conditions. While on other hand,
OPC samples have shown a decrease of up to 6% in compression and 5% in flexure respectively under
harsh conditions. From the results, it is concluded that geopolymer concrete has better and excellent
resistance to ASR and has more durability, and can withstand a long life span as compared to OPC.