Glass fibres used alone in concrete suffer surface degradation by hydrated cement paste. The unit attributes this to:

1. Glass fibres come in rovings, strands or woven/chopped strand mats. 2. The unit identifies surface degradation as a major problem in their long-term use. 3. The degradation is caused by the high alkalinity of hydrated cement paste. 4. The fix is to use alkali resistant glass fibres, which are commercially available. 5. The chemistry is alkali attack, not acid attack, heat or carbonation. _Source: IGNOU Concrete Technology, Unit 11 "Special Concrete" (Light Weight, Aerated, No-Fines, High Density, Fibre Reinforced, Polymer Concrete)._