Exploring Alternative Cement-Free Masonry Mortars

August 7th 2023 in Sustainability
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Introduction

Cement-based mortars have dominated masonry construction, over the last 100 years. However, growing concerns about the environmental impact and sustainability of cement production have driven the development of alternative masonry mortar options, that are cement-free.

These alternatives aim to reduce the carbon footprint of construction while maintaining structural integrity and durability.

In this article, we will explore various alternative cement-free masonry mortars, that have emerged as viable options for sustainable construction.

The Need for Cement-Free Masonry Mortars

Cement production is a major contributor to carbon dioxide emissions, a primary driver of climate change. Additionally, traditional cement-based mortars have limitations related to cracking, shrinkage and environmental degradation.

To address these issues, researchers and builders are seeking alternative mortar options that are more sustainable and environmentally friendly.

Types of Alternative Cement-Free Masonry Mortars

1. Lime-Based Mortars 

Lime mortar is a time-tested alternative to cement-based mortar. 

The development of a 'modern-day' lime mortar, suitable for the demands of 21st Century construction, is made from hydrated lime, sand and water. 

Lime-based mortars offer several advantages, including: 

Reduced carbon footprint: Lime production emits fewer greenhouse gases compared to cement. 

Compatibility with historic buildings: Lime mortars are often used in historic restoration projects because they closely mimic traditional mortar properties. 

Flexibility and breathability: Lime mortars are more elastic than cement mortars, reducing the risk of cracking. They also allow buildings to "breathe," preventing moisture-related damage. 

2. Clay-Based Mortars 

Clay mortars utilise natural clay as a binding agent. They are gaining popularity for their sustainability and compatibility with earthen construction techniques. 

Key benefits of clay-based mortars include: 

Low embodied energy: Clay is abundant and requires minimal processing, leading to a low carbon footprint. 

Thermal properties: Clay mortars offer excellent thermal insulation, contributing to energy efficiency in buildings. 

Chemical-free: Clay mortars are non-toxic and do not release harmful chemicals over time. However, clay mortars may not be suitable for all building types and can be vulnerable to erosion when exposed to heavy rain. 

3. Magnesium Oxide (MgO) 

Mortars MgO mortars are an emerging alternative that utilises magnesium oxide as the binder. This material has gained attention for its potential to reduce the carbon footprint of construction. 

Key features of MgO mortars include: 

Rapid carbonation: MgO absorbs carbon dioxide from the atmosphere during curing, resulting in a net carbon-negative material. 

Fire resistance: MgO mortars have excellent fire resistance properties. 

Durability: They exhibit good durability and resistance to weathering. 

However, MgO mortars are less commonly available and may have limitations in certain applications. 

4. Geopolymer Mortars 

Geopolymer mortars are an innovative alternative that relies on geopolymers as the binding agent. 

Geopolymers are typically made from industrial by-products or naturally occurring materials, reducing the environmental impact. 

Key advantages of geopolymer mortars include: 

Low carbon footprint: Geopolymers often use industrial waste materials, diverting them from landfills and reducing the need for traditional cement. 

High durability: Geopolymer mortars can exhibit excellent resistance to chemical corrosion and weathering. 

Rapid setting: They can offer quick setting times, which may improve construction efficiency. 

However, the use of geopolymers may require specialised knowledge and quality control during mixing and application. 

Considerations and Limitations

When selecting an alternative cement-free masonry mortar, builders and architects should consider several factors: 

Compatibility with existing structures: Historic and traditional buildings may require specific mortar types to maintain structural integrity. 

Local availability: The availability of materials may vary by region, affecting the feasibility of using certain mortar types. 

Performance requirements: The intended use of the mortar and the specific requirements of the project should guide the choice of alternative mortar. 

Cost considerations: Some alternative mortars may be more expensive than traditional cement-based mortars. 

Conclusion

Alternative, cement-free masonry mortars, including lime-based mortars, clay-based mortars, magnesium oxide mortars and geopolymer mortars, offer sustainable and environmentally friendly options for modern construction. 

Each mortar type has its unique advantages and limitations, making it essential for builders and architects to carefully assess the suitability of these alternatives for their specific projects. 

As the construction industry continues to evolve towards greater sustainability, these alternatives, particularly hydraulic lime mortars, will play a crucial role in reducing the carbon footprint of masonry construction, while ensuring durability and performance.

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