Sodium sulfate and magnesium sulfate resistances of mortar with multi-binder systems of calcined kaolinite clay, fly ash, and limestone powder

Abstract

This study aimed to assess the durability of mortars subjected to sulfate solutions (specifically Na₂SO₄ and MgSO₄). The effectiveness of cement replacement materials (CRMs) such as calcined kaolinite clay (C), high CaO fly ash (F), and limestone powder (L) in multi-binder systems was studied. The pastes’ microstructure, phase assemblage, and elemental profiles were examined. The results showed that mortars containing calcined kaolinite clay and high CaO fly ash (C30F15) had the lowest expansion when exposed to Na₂SO₄ and MgSO₄. This was caused by the decreased portlandite and expansive products, improved mortar’s compressive strength, and refined pore structure (smallest pore size and lowest pore volume). However, the use of the CRMs, especially when calcined kaolinite clay was combined with fly ash or limestone powder, raised the weight loss and surface deterioration of mortars in a MgSO₄ solution because of the lowered pH in the pore solution and formation of MSH.

Keywords:

• calcined kaolinite clay
• fly ash
• limestone powder
• sodium sulfate
• magnesium sulfate

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Data will be made available on request.

Additional information

Funding

This study was supported by the Thammasat Postdoctoral Fellowship to the first author. This research was also partially funded by the National Research Council of Thailand (NRCT) as well as with support from the Center of Construction Technology and Traffic Management (CONTRA) and the Burapha Construction and Maintenance Technology Research Unit (BCONTEC), Burapha University, Thailand.