Alkali-Resistant (AR) Glass Fibre vs Standard Glass Fibre in GRC: Composition, Service Life, and Cost

The differences fall in three places: composition (AR fibre carries zirconia ≥16% + a dedicated alkali-resistant sizing; standard fibre has neither), service life (in cement alkalinity, AR fibre holds strength for 50 years; standard fibre is corroded and loses its reinforcing effect in 2–3 years — the component then powders and cracks), and price (AR fibre runs about 3× standard). Visually, the two are nearly indistinguishable; the only reliable identification is lab fibre composition analysis + selecting a traceable, reputable supplier.

Core Points

1. Composition: AR fibre has zirconia ≥16%; standard fibre has no alkali-resistant formulation
2. Service life: 50 years vs 2–3 years (alkali corrosion)
3. Price: ~3× — this is the first place low-cost GRC cuts corners

I. Corrosion Mechanism: Why "Cement Eats" Standard Fibre

Cement hydration generates large amounts of calcium hydroxide, leaving the pore solution strongly alkaline. Standard E-glass fibre's silicate skeleton is hydrolysed in that alkali — the fibre surface corrodes and thins, strength collapses; at the same time, alkali reacts at the fibre interface to form swelling products, prying the fibre loose from the matrix. The zirconia in AR fibre forms an alkali-resistant barrier inside the glass network, and the surface sizing cuts the corrosion rate by roughly two orders of magnitude. That is the materials-science basis of the "50-year design life" claim.

II. Price Gap and Adulteration: The Industry's Grey Zone

AR fibre costs about 3× standard fibre and takes a large share of GRC material cost — which makes it the first target for low-price suppliers: blending in standard fibre or doing a half-and-half mix. Both appearance and early strength look normal (corrosion is a chronic process), so acceptance inspection finds nothing. Detection means: ① lab composition testing for zirconia content; ② cross-section SEM/chemical analysis on samples; ③ choosing suppliers with traceable fibre purchase records and batch tracking.

III. Standards and Selection: Locking Risk into the Contract

Standards basis: the JGJ/T423-2018 system explicitly mandates alkali-resistant glass fibre for GRC; international standards (such as the GRCA system) equally take AR fibre as the premise.

Procurement moves: ① contractually specify "AR alkali-resistant glass fibre, zirconia content ≥16%"; ② require fibre purchase certificates (brand and batch traceable); ③ on-arrival, sample-test fibre content and composition per batch.

Notes

Historical footnote: early GRC was put on the obsolete-materials list precisely because ordinary fibre was used; only after AR fibre became mainstream did the industry truly mature — hence the rule "ask whether the fibre is AR alkali-resistant" when selecting GRC.

Myth: "They are all glass fibres; the difference is not big." Cement pore solution pH reaches 12.5–13.5 — for standard E-glass that is a strong-corrosion environment. Fibre diameters erode and thin, the interface debonds, and the component's "rebar" disappears within two years. This is not a performance discount; it is the failure of the entire reinforcing system.