Magnesium Sulphate Attacks on Mortars  - Influence of Temperature, Type of Sand and Type of Cement

For conservation interventions of historic masonry generally lime-based mortars such as pure air lime mortars, lime-pozzolan mortars, natural hydraulic lime mortars and ternary mortars (lime-pozzolan-cement) are used. The main reason is that their hygric and mechanical (strength and ductility) performance are easy to adapt to most existing historic masonry (compatibility requirements). Although the basic appropriateness of lime-based mortars for restoration is undisputed, there are also some limitations in the application of these mortars. In this report a review is given of the theoretical backgrounds and further of laboratory research developments in the field of lime-based binders and mortars over the past decades. Furthermore, practical experiences in positive and negative sense (damage cases) are elaborated. Drawbacks and points of attention are being dealt with, which are essential for a durable application of lime-based mortars for the conservation of historic masonry. In general, it is concluded that points of attention should be addressed through a thorough evaluation of their potential and through testing of their suitability. For these mortars, even more than for modern cement-based mortars, specifically, environmental exposure conditions and application conditions should be considered.

show abstract

“…If Mg 2? ions are also present, the leaching of C-S-H phases occur, and thus the mortar loses structural integrity [115].…”

Section: Weak Trass-lime Repointing Mortarsmentioning

confidence: 99%

RILEM TC 277-LHS report: lime-based mortars for restoration–a review on long-term durability aspects and experience from practice

et al. 2022

View full text Add to dashboard Cite

show abstract

“…On the other hand, the leaching of the calcium from the C-S-H phases leads to the loss of the mechanical resistance of the paste. The literature has shown that the presence of Mg 2+ ions (in case of attack by magnesium sulfate) cause decalcification of C-S-H (by ion substitution), increasing the degree of alteration [72].…”

Section: Water Vapor Permeability and Water Absorptionmentioning

confidence: 99%

“…The presence of non-carbonated portlandite prevents the formation of expansive sulfates, possibly due to the precipitation of magnesium hydroxide (brucite) and avoiding the Ca-leaching of the C-S-H gel. As a consequence, the lasting of the samples increased [71][72][73]. Freeze-thaw cycles…”

Section: Water Vapor Permeability and Water Absorptionmentioning

confidence: 99%

Improving lime-based rendering mortars with admixtures

González-Sánchez

Fernández

Navarro-Blasco

et al. 2021

Construction and Building Materials

View full text Add to dashboard Cite

“…Chlorides are known to be accelerators of compressive strength development in mortars or concrete [1]. On the other hand, WLI was found to have a higher sulphate concentration than SW. Mortar prisms subjected to it were expected to suffer more from sulphate attack [36][37][38]; this was observed in this study.…”

Section: Chemical Analysis Of Sw and Wlimentioning

confidence: 65%

Effect of Sulphate and Chloride Ingress on Selected Cements Mortar Prisms Immersed in Seawater and Leather Industry Effluent

Wachira

Ngari

Thiong’o

et al. 2019

Advances in Civil Engineering

View full text Add to dashboard Cite

Cement structures are major capital investments globally. However, exposure of cement-based materials to aggressive media such as chloride- and sulphate-laden environments such as coastal areas affects their performance. Ordinary Portland cement (OPC) is the main cement used in buildings and civil structures such as dams and bridges. This paper reports the findings of an experimental investigation on the effect of ingress of Cl− and SO42− on compressive strength development and the ions’ diffusivity in selected OPC brands in Kenya. The aggressive media used included seawater (SW) and wastewater from leather industry (WLI). Three brands of commonly used cements of OPC in Kenya were used. Mortar prisms were prepared from each brand of cement at different water-to-cement ratios (w/c) of 0.5, 0.6, 0.65, and 0.7 and allowed to cure for 28 days in a highly humid environment. The aggressive ions’ ingress in the mortar prisms was accelerated using a potential difference of 12 V ± 0.1 V. Analysis of diffusivity and diffusion coefficient of Cl− and SO42− was finally done. Compressive strength analysis was done before (at the 2nd, 7th, 14th, and 28th day) and after exposure to the aggressive ions. The results showed that the diffusivity of chlorides was more pronounced than that of sulphates. Diffusivity was observed to be higher at higher w/c ratios for all cement categories. It was observed that compressive strength increased with curing age, with the highest observed at 28 days. Cement A was generally found to have the highest compressive strength for all w/c ratios. The compressive strength was observed to increase after the mortar prisms were exposed to SW as opposed to the ones exposed to WLI. Generally, it was also observed that the strength gain increased with increase in w/c. The loss in strength was also observed to increase with increase in w/c.

show abstract

Magnesium Sulphate Attacks on Mortars - Influence of Temperature, Type of Sand and Type of Cement

Cited by 6 publications

References 29 publications

RILEM TC 277-LHS report: lime-based mortars for restoration–a review on long-term durability aspects and experience from practice

RILEM TC 277-LHS report: lime-based mortars for restoration–a review on long-term durability aspects and experience from practice

Improving lime-based rendering mortars with admixtures

Effect of Sulphate and Chloride Ingress on Selected Cements Mortar Prisms Immersed in Seawater and Leather Industry Effluent

Contact Info

Product

Resources

About