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The built environment contributes to over 40% of global greenhouse gas emissions[1]. To change this, construction professionals should aim to reduce the sector's environmental impact while meeting humanity’s needs. 

So, where does this big leap to greener construction and buildings start? Could it be with innovative but untested technologies? Improving building codes, a practice that has proven almost impossible to implement? Or could it all start by simply using lower-impact, organic building materials? 

Hempcrete has been touted as one such solution. But what the hell is it? In this article, we’ll demystify this cutting-edge material and help you understand how it could end up on your next project.

Could hempcrete replace existing CO₂ offenders?

Over half of all global raw materials consumed are used in the construction of buildings and roads[2], and the most popular ones have a pretty dirty record - we’re looking at your reinforced concrete! Greenhouse gas emissions associated with these materials arise throughout the extraction, fabrication, construction, and disposal. Compounded together, this process embeds massive amounts of carbon into the material’s footprint and significantly contributes to climate change.

In contrast, the hemp plant is a natural resource that has been used for thousands of years. It was initially spun into textiles and more recently is used in clothing, fabrics, biofuels, animal feed, and even biodegradable plastics. But over the past few years, researchers have found an even more exciting use for it as a construction material! That’s right, hemp, combined with a lime-based binder, is now being used as a composite construction material and has been used in various applications. 

Hempcrete’s unique and durable natural properties allow for its use in many building applications, being particularly effective as an insulating material within wall cavities. Hempcrete as an insulator offers an alternative to commonly used fiberglass or polymer-based insulators in walls, roofs, or floors. 

Hempcrete can also be used in place of drywall and plaster by directly casting it around primary or secondary structural frames. This allows designers to incorporate its unique thermal performance (high thermal mass) and aesthetic properties whilst also acting as an all-in-one sealant from the elements.

 is even underway to assess the effectiveness of using hemp-based elements in place of steel rebars in RC construction! This would both cut carbon emissions and address the problem of rebar corrosion that often leads to the premature decay of structures. This would be a pretty crazy game-changer for the sector, but whether or not it’s viable at scale remains to be seen…

When hemp is harvested, its fibers are stripped off, leaving the woody hemp core or stalk behind. After chopping it finely, it is mixed with a lime binder to produce lightweight concrete. This gives hempcrete its modest structural and compressive strength and stiffness. However, for now, its unique properties are primarily suited to non-load-bearing applications as part of timber or other framed buildings in smaller-scale construction. 

Whilst it is a very lightweight material, hempcrete has the characteristics of a heavier material that can both insulate and store heat. By varying the mixed quantities, hemp-lime materials can be used in denser or lighter composites for insulation due to their remarkable thermal and acoustic performance. This is what gives it its versatility.

How people experience a building, feeling hot, cold, or just right, is a measure of a building’s thermal comfort. Hempcrete’s high thermal mass and insulation, thermal inertia, and air-tightness structure can play a significant role in how one experiences their home. This means that not only can hempcrete replace structural elements, but it can also be an effective tool for MEP engineers too. 

And the kicker? It’s great for the environment as well! We’ll get into that next… 

Hempcrete comes with considerable sustainability credentials. During its rapid growth cycle, hemp absorbs carbon dioxide, and even during construction, hempcrete is actively capturing and storing CO₂ in the structure. 

Growing hemp, in general, helps in the process of regenerating agriculture and replenishing the soil. The energy and water used in planting, harvesting, and processing hemp are low. In addition, the low-value parts of the hemp plant (the woody hemp core or hemp shiv) are required to make hempcrete. So, the hemp leaf itself can still be used for other applications. Thereby hempcrete replaces many quarried materials as an aggregate. Compared to traditional aggregates like stone and gravel, the environmental impacts of hempcrete aggregate extraction are negligible.

As we saw above, as an insulator, hempcrete can also replace more common synthetic fossil fuel-based materials, which consume a lot of energy and emit toxic chemicals during manufacture. As a structural finish to internal surfaces, hempcrete can regulate humidity, helping to eliminate toxic mould growth; it can insulate and store heat, creating comfortable and healthy interior environments.

While hempcrete has so far been used primarily in residential applications, there are a few innovative examples of hempcrete being used in commercial settings. 

European countries have more readily adopted hempcrete construction in buildings for several decades; the uptake has been slower in countries like the United States and Australia. However, hempcrete is a strong contender for mass adoption as industries look for sustainable and practical alternatives that can cut embodied carbon.

Architects completed France’s first public building made of hemp, the 4,000-square-foot Pierre 

. This was an opportunity to test the limits of what can be achieved with hemp and be at the forefront of something new. The walls of the sports center are infilled with hempcrete blocks clad in cement-fiber panels to protect them from the elements.

On the other side of the pond, Canadian startup 

 has created a modular building system based on structural blocks that, according to the company, can ‘outperform virtually all existing and alternative buildings’. The cores of these structural blocks are made from hempcrete 

 portland cement, all encased within load-bearing blocks. Industrial hemp and lime binder have been integrated into pioneering structural solutions that advance visions of sustainability, resilience, longevity, functionality, and healthy living. 

The ‘Harmless Home’ with Just BioFiber’s blocks for the exterior walls (

Opportunities to minimize transport emissions, reduce embodied carbon, unlock sustainable design, and contribute to local economies are some of the reasons why CalcTree loves hemp. It blazes the way forward to more innovative and sustainable products in the construction industry. 

A quick dive into the web helped us find a few up-and-coming start-ups occupying the innovation space in material technology. We’ve chosen two that are currently developing hempcrete solutions and technologies:

In the United States, Hempitecture produced hemp-based solutions and materials specifically for the building and construction sector. Its mission is to integrate hemp-based products into our built environments, positively impacting people and the planet by reducing emissions and regenerating farmland.  

An Australian, female-owned hempcrete construction start-up that works with licensed hemp farmers to convert what are usually hemp waste products into saleable materials, focusing on building materials and much more!

“Engineers have three books: wood, concrete, and steel. That’s it.”  

-Terry Brooks, vice-president of Just BioFiber


Alongside developments in hempcrete, recent studies have been advancing research in supplementary cementitious materials (SCM) to reduce the carbon footprint of one of the industry’s biggest CO₂ offenders: Portland Cement. The use of virgin aggregates or waste materials has been experimented with, but the research is patchy and still pretty immature. In any case, advances in engineering techniques, design, and innovations will have to keep pace with breakthroughs in alternative sustainable materials.

Hempcrete: Building smart, green and for the future

Urban expansion, population growth, and resource constraints question the established and conventional delivery of structural systems and the design and construction of our built environments. Indeed, what can sustainable cities look like? Rapidly growing urban centers are putting immense pressure on having an answer to this question. The answer will evolve, but it might be right under our noses right now!

Our ability to address emerging space and resource constraints and action climate change mitigation in a resilient and sustainable way will be tested. This has become a catalyst for new solutions and innovations in delivering projects. It has also sparked a resurgence in research and the popularity of one of our oldest and most reliable building materials: 

Mass Timber projects or heavy timber projects have proven to stack up to traditional construction methods in the building sector (Look outside: steel and concrete buildings are everywhere!) across all factors: cost, productivity, buildability, functionality, and reliability. 

With a move towards engineered timber design and mass timber products, the industry can:

By and large, mass timber is here and here to stay, for now at least. Why? Well, it is a tenable alternative to conventional construction and building types. It is also making impressive headway across the whole construction industry ecosystem and genuinely impacts the competitive marketplace. Simply put, engineered wood products can encompass a wide array of building members and elements from typically low-value but fast-growing softwood trees and turn them into building materials that can rival concrete and steel in strength, durability, and commercial outcomes. All this whilst being a carbon-cutting alternative gives mass timber its appeal. 

Recent changes to Australia’s National Construction Code (NCC) have streamlined approvals for up to 8 stories for mass timber structures. There has also been a significant market expansion for locally and internationally sourced and produced mass timber products to deliver and support evolving construction types within the Australian market.

Currently, the most common types of heavy timber in use are: 

As international building codes evolve in a space that hopes to build taller but more sustainable, we will see timber-frame structures, design, and construction follow suit. We expect national building codes worldwide to drive this trend in 2023 and beyond.

Possibly the biggest draw of mass timber is its green credentials. As governments eventually transition to regulating carbon and supporting CO2 abatement, businesses will follow suit (conversely, companies could put pressure on the government) and be empowered and incentivized to move toward a clean energy future. This would propel the building sector to research and develop more sustainable construction materials. Currently, the environmental impact of construction is unsustainable. Cement and steel production is high energy and fossil fuel-intensive, with 7% of global CO2 emissions originating from the steel industry alone and cement production accounting for 8% of total global CO2 emissions.

Furthermore, unlike wood, cement cannot be reused or salvaged. While steel can be multi-cycled, it still requires high-temperature processing. Unlike concrete, steel cannot always be manufactured locally; it is typically transported over significant distances, further contributing to carbon emissions.

The resources we extract and the materials we manufacture for different building types contribute enormously to greenhouse gas emissions. Whilst initiatives have been undertaken in these industries to improve energy efficiency, difficulties in transitioning towards a lower carbon footprint have hindered wood construction and mass timber projects. One can argue that end-of-life disposal of wood products and the need to source timbers cut from forests may not be the most appealing third alternative. However, now, timber is one of the only renewable construction materials used today. By its very nature, timber sequesters and removes CO2 from the atmosphere, reducing carbon emissions significantly before and even during construction.

Adding to its clean record, mass timber construction is a speedy build.  Prefabricated and modular construction are popular design methods in the construction sector. Prefabricated buildings comprise components and elements manufactured in remote factories, transported on-site, and assembled into buildings. Studies have already shown that productivity will substantially increase by increasing the proportion of prefabricated elements in a construction project. This will result in faster construction, less waste, noise, disruption, and lower unit and operational costs.

There are many benefits to prefabricated mass timbers as well. Prefabricated cross-laminated timbers offer higher dimensional stability and structural integrity than traditional timber-framed systems. Further, the fact that wood is such a lightweight, versatile, and flexible material means that factory handling, transportation, and assembly of elements are substantially more straightforward. While direct cost comparisons still have concrete buildings at an advantage over wood buildings, prefabricated timber’s lightweight nature and the opportunity to speed up construction time and optimize erection programs shift the cost balance.

We can expect significant workforce upskilling in the mass timber construction market to deliver on the promise of significantly shorter construction programs (up to 20-50%) and cut schedules due to advances in modular construction types and prefabrication.

Interest is growing in building tall and pushing the limits of innovation with structural timber. However, timber in construction is far from a new technique, so is a throwback worth it? Well, it turns out it can be. Research and advances in material science are looking at wood modifications to address timber’s dimensional stability, durability, fire resistance, longevity, and UV sensitivity. The aim is to open up new ways of making timber’s structural performance even more optimized, workable, safe, and sustainable. Fracture mechanics, clear-coating processes, prestressed timbers, timber hybrids, and composites are all spaces we watch keenly.

The construction sector as a whole is at the precipice of significant innovations that are mainly in the form of new design tools such as Building Information Modelling (BIM), 3D rendering software, Augmented Reality (AR), Design for Manufacturing and Assembly (DfMA) and data integration technologies. These innovations themselves further expand the possibilities for mass timber construction and design. These tools aim to find solutions to common and emerging constraints within the construction sector, making room for efficiency, productivity, reliability, safety, and sustainability advances. They open the door for designers and engineers to address problems in a more integrated way. These emerging and sophisticated approaches could boost its market share and consolidate the fact that timber is indeed well-suited to these new business models.

Wood and wellbeing: time to ‘spruce’ up our living and working spaces.

Humans have used wood as a building material for millennia. Trees are essential in promoting biodiversity, reducing the heat island effect and noise, and cleaning surrounding air and water, even in urban settings. Yet the role of wood as a factor in better health and well-being in both external and internal environments has been anecdotal for a long time. Only now are wood’s biophilic benefits being seriously researched and understood.

Inside our homes, work, or public spaces, access to natural materials like wood has led to decreased occupant stress, greater confidence, and better social integration. A study commissioned by Forest and Wood Products Australia, focusing on the impact of wood in the workplace and on people, found a correlation between employees’ physical, mental, and emotional health and the presence of wood. Benefits included overall worker satisfaction, lower absenteeism, and enhanced productivity. Evidence-based research is making strides in quantifying how people’s access to nature inside and around the workplace or the home contributes to measurable social and economic benefits. 

Well, quite a lot. Quantifying how our built environment can improve productivity, efficiency, and overall quality of life would significantly impact the building sector and design and construction priorities. Currently, building rating schemes such as WELLs incentivize building designs to promote physical and emotional occupant health. Following that, architects and designers will be encouraged to make holistic decisions based on biophilic design and material choices, which then reverberate in engineering design.

Sustainability and mass timber construction: top of mind and leading edge

The construction industry is experiencing increasing demand to address climate change and remediate the enormous impacts the sector has had on the natural environment. Ensuring a healthy planet, vibrant and resilient communities, regenerating natural systems, and designing-out waste and pollution should be at the core of any sustainability framework.

The built environment contributes a substantial chunk of global CO₂ emissions, with the construction industry accounting for nearly 40% of global energy and GHG emissions. Some of the industry’s most popular materials, steel and concrete, contribute 7% and 8% of total global CO₂ emissions, respectively [1]. The implications, reach, and magnitude of the impacts are well-researched, and it’s safe to say that the environmental impacts of construction are unsustainable.

Making the construction industry more eco-friendly will require research, innovation, and new techniques and technologies. In our article listing the 

Top 10 ways to decarbonize the built environment

, we concluded that a diverse range of inextricably connected approaches is required. One strategy that did stand out is to replace traditional materials with recycled, recyclable, or biobased materials; we’ve written articles on 

 to showcase this. But the industry is constantly evolving, and the potential doesn’t stop there, so we’ve decided to explore more of these solutions by listing the Top 5 most sustainable materials used in construction.

Zero carbon cement is cement produced in a way that produces zero emissions. Portland cement has been a global standard in cement production since the early 19th century. Cement production is the world’s biggest industrial carbon pollution culprit, contributing to approximately 8% of global emissions, equivalent to all the cars on earth combined [2]!

So, the time has come to rethink cement. Cement mostly acts as the binder between aggregates in forming concrete, yet it’s almost exclusively responsible for the resulting CO₂ emissions of concrete. But its affordable, durable, and versatile properties have made it the world’s second-most consumed substance after water [3].

The chemical reactions turning limestone into cement, the energy needed to produce high temperatures, and transportation costs must all be addressed. Alternative fuels, waste, or the electrification of kilns can drive out fossil fuels required to power cement production. The infrastructure used to transport cement can also be decarbonized. Substituting emitting ingredients in cement with alternative coarse and fine aggregates such as crushed rock sand, industrial by-products, glass, or plastics can make concrete more sustainable. Where cement is used, maximizing its efficiency should be top of mind through recycling and reuse.

Taking full advantage of passive solar energy is an integral part of sustainable design, and this concept has been gaining momentum in more and more residential and commercial projects. Read our article on 

how Passive House design can improve building energy efficiency and reduce carbon footprints.

Smart windows can help maximize passive design. In short, smart windows use specialized glass that adjusts their tint based on ambient temperatures. This allows them to retain heat during winter and dissipate heat during summer. 

Smart window technology is not new; it’s been employed in airplanes, boats, and cars but is slowly making incursions into homes, offices, and airport terminals. Chemical reactions in smart windows between suspended particle devices, electrochromic materials, or polymer liquid crystals and heat or light levels are the secret to their color-changing properties. They can be the new secret to reducing energy consumption in buildings.

Perhaps one of the most promising materials in the charge towards sustainability goals is mycelium brick. Mycelium is a natural fungus material produced from the root-like fibrous material of fungi underneath the ground. When processed and dried, this natural material has industrial-level strength. Mycelium bricks can be grown when organic waste, like straw, is put into contact with mycelium. The fungus grows and digests the waste leaving behind a solid brick. It takes a few days, and all that’s required is waste at room temperature! It’s 100% organic, compostable, biodegradable, and fire and water-resistant, and its use as a building block for future buildings is promising. It has been used before for packaging purposes and in other disciplines, but its potential to be exploited as a building material in the construction industry is expanding. 

While it may not have all the functional characteristics required for construction, such as high strength and durability, mycelium can be exploited for other functions like insulation. It can be used to create airtight insulation between wooden panels. Despite some limitations, there is excellent potential, so watch this space!

Timber as a commercial construction material is going mainstream; projects like the 

 in Sydney, the world’s tallest hybrid timber tower, signal new heights and bold sustainable solutions using this natural material.

Bamboo is no exception; while it technically falls into the category of plant grasses, it can be harvested more sustainably and replenished quicker than any other timber. Also, in the way that it grows, it does not require pesticides, irrigation, or fertilizers. Some species can even grow up to a meter per day.

But what about its building properties? Bamboo has a high compressive strength and is an extremely lightweight material. Bamboo has a higher tensile strength than steel due to its axial fibres. Bamboo is substantially fire resistant and can withstand temperatures up to 4000 C due to its high silica content and water.

Bamboo is used to construct walls, partitions, flooring, and scaffolding, adding stability, strength, and protection. Bamboos are easy to install and highly cost-effective.

Reusing, recycling, and repurposing materials automatically boost the sustainability credentials of any project. Steel is by no means an environmentally friendly material, and it is not renewable. However, it remains a lightweight, durable, and versatile material. The upside is that steel is multi-cyclable, which means it can be reused, repurposed, and pass through the supply chain in multiple forms almost indefinitely. Even after being recycled numerous times, steel keeps its original metallurgical properties. Recycling steel also means 75% less energy is used compared to making new steel products [4]. Energy and natural resources are saved, and carbon emissions are reduced.

Similarly, recycling materials like rubber, which can be used for paving surfaces as granules in asphalt, also improve the sustainability quotient of many projects.

Finally, like recycled steel, timber, and wood can be reclaimed from old projects and reused in new ones. Salvaging wood from old structures such as buildings, barns, warehouses, bridges, or old forestry logs can be reused in other settings without reprocessing into a different product. Wood products can also be recycled through milling, cutting, coating, or sanding to create a new product. Growing momentum in preserving forests and reducing deforestation will only boost the appeal of reclaimed and recycled timbers.

Decarbonizing the construction industry is no easy task, and we recognize that many of the interdependencies that can make it happen will need to work together in harmony. But, we also know that the road to net zero will be bumpy if we don’t actively work towards making the building sector more sustainable. 

Top 5 Innovative & Sustainable Materials that should be mainstream in the construction industry.

Concrete is, without a doubt, one of the most widely used construction materials. After all, large cities lined with towering skyscrapers are known to be 

jungles for a reason. The carefully curated mixture of cement, water, and aggregates form the structures of many buildings around us today. This isn't surprising, given concrete is a highly durable, economical, and increasingly sustainable construction material. Check out our article 

 for more info on sustainable materials and concrete.

While concrete is becoming more sustainable, we aren't at a stage where concrete production is carbon neutral, but there is research into 

 and efficient production processes. To understand how concrete ties into sustainability, we have to dive a bit deeper into the workings of cement, the core ingredient that forms concrete.

Cement is a fine powder that, when mixed with water, undergoes a hydration reaction to form a binding paste. It is then combined with a mixture of coarse and fine aggregates to create the concrete we use in construction.

Cement powder is generally made from lime, silica, alumina, and iron oxide [1]. The raw minerals are mined and processed through a rotary kiln, as is in the case of the most commonly used Portland Cement. The rotary kiln dries the mixture of raw materials. It produces clinker by subjecting the raw materials to high enough temperatures that the chemical bonds break apart and reform. This can be achieved either through the Wet Process, whereby the minerals are supplied as a wet slurry, or the preferred Dry Process, where minerals are provided as a dry mixture and preheated before entering the kiln.

After the clinker is produced from the rotary kiln, it is cooled, grounded, and mixed with gypsum and other admixtures to form the final cement powder. The final product mainly consists of calcium silicates and aluminates. The proportion of clinker present in the cement to gypsum and other constituent minerals defines the final 

The types of cement we commonly use in construction

Cement used in construction is typically classified by its physical properties, which come from how it is manufactured and its constituent minerals. The standard designation of cement is based on several factors:

From AS 3972, cement is grouped into six major types across two categories:

Cement is typically used for its high compressive strength. However, it suffers from a far weaker tensile strength, so concrete structures typically accompany steel reinforcement. Steel is strong in tension and compression, which can compensate for the lack of tensile strength in concrete.

Properties of Ordinary Portland Cement Paste:

Properties of Ordinary Portland Cement concrete:

Chemical symbols used in the notation for cement compounds are abbreviated accordingly [11]:

The four main compounds of Portland cement are:

How do these chemical compounds contribute to cement properties?

Alites in Portland cement are mainly responsible for determining the initial 

 in the first week of hardening. Belite determines the hardening of the concrete in the remainder of the 28 days of concrete hardening.

Concrete formation involves mixing cement with water, fine aggregates, and coarse aggregates. Cement serves as the adhesive to concrete, binding all the materials together. However, it lacks material strength, resulting in weak tensile strength of concrete. The aggregates are the components that determine the compressive strength of concrete instead. Coarse aggregates support the majority of compressive loading. Sand also contributes to compressive strength but mainly fills in the gaps of the crushed aggregates. Finally, water mixes with cement to help bind all the materials together and provides the workability of concrete during construction. Below are the associated mixing ratios for different concrete strength grades and their applications: 

Remember how in the beginning, we mentioned concrete is becoming more sustainable? Yes, there is plenty of discourse on the sustainability of concrete in construction, and a big concern is centered around cement manufacturing.

During the production of Portland cement, the kiln is heated up to 1450 degrees Celsius, which requires large amounts of energy. At this stage, calcination occurs in the mixture of minerals. The calcium carbonate within the limestones is converted to calcium oxide, producing carbon dioxide as a byproduct and releasing it. The empirical expression for this reaction is as shown:

5CaCO3 + 2SiO2 → (3CaO,SiO2)(2CaO,SiO2) + 5CO2

Calcium Carbonate + Kaolinite -> Alite*Dicalcium Silicate + Carbon Dioxide

‍❗Producing 1 tonne of Portland clinker will also directly yield 0.55 tonnes of carbon dioxide gas as a product [14].

Let's consider the amount of fuel it needs to generate the energy to raise the kiln to 1450 degrees Celsius. We are looking at about another 0.40 tonnes of extra carbon dioxide produced. This would mean an associated 0.95 tonnes of carbon dioxide per tonne of Portland clinker produced.

This process alone accounts for half of the carbon emissions in cement production and 4% of the globe's total carbon emissions. The other half of carbon emissions in cement production comes from creating energy to fuel the process [15].

It's a given that sustainability is a big issue within the construction industry. So, what's the solution?

We can tackle it in two ways: reduce carbon emissions by addressing the carbon in the materials or reduce the carbon from production.

Let's go with the latter first. There is a rising carbon minimization strategy in the form of Carbon Capture and Storage (CCS). The idea is to capture all the carbon dioxide released in the cement production process and transport them to an underground storage system [16]. The process involves combusting the fuel in oxygen to allow for the greatest concentration of CO2 in its emissions. The emissions are then captured and compressed into a liquid before finally getting transported through pipelines into the storage system. 

There are some limitations to this method. CCS does not entirely rid cement production of carbon dioxide; CCS has yet to be tested on an industrial scale. About 72-90% of CO2 is produced, with the remainder coming from energy costs.

If Portland cement isn't the way to go, what will it be?

Hope is far from lost. While Portland cement is still the most popular cement option in construction, we currently have areas where we can continue toward a carbon-neutral future. One answer is geopolymer cement. Geopolymer is made from alkali aluminosilicate in waste materials being put through polycondensation [15]. Such materials include fly ash from coal burning, ground-granulated blast-furnace slag, and clay, all abundant in Australia.

Geopolymer concrete produces up to 80% fewer carbon emissions than Portland cement as it does not rely on calcium carbonate [14]. It also primarily uses the waste materials mentioned above instead of raw minerals.

Geopolymer cement also has performance benefits in the production of concrete and construction. Initial and final setting times increase as the cement is produced with a high alkali concentration. Its initial compressive strengths are lower than Ordinary Portland Cement. However, strength increases through concrete aging. It has been shown that the final compressive strength can match that of Portland Cement and, at times, even higher strengths [17].

Research around geopolymer cement and sustainable concrete has been conducted in the construction industry for a while. We are still transitioning into a future that is less reliant on Portland cement. It's not an easy path, for sure. Still, there are plans and studies on integrating more environmentally friendly cement into the industry from an engineering and business perspective.

These strategies lead Australia to a carbon-neutral future for cement production and beyond.

A report by Beyond Zero Emissions in 2017 proposes a 5-step process by which Australia can transition our cement production to a carbon-neutral future with the possibility to venture into carbon-negativity [15].‍

Geopolymer cement has been known for a while. Still, despite its commonly accepted environmental and strength benefits, it faces challenges in its adoption into the construction industry. With Alkali Activated Materials (AAM) generally, the first is the high costs associated with the sodium silicate and sodium hydroxide used to activate the materials [18]. These activators are costly and corrosive, requiring special handling instead of large-scale transportation for Portland Cement.

Other than the properties of the activators, geopolymer cement has short setting times and high curing temperatures [18]. Temperatures of 60 to 80 degrees Celsius are required for geopolymer concrete to achieve the same strength as Portland cement. Thus, geopolymer cement is limited in its practicality in large applications outside precast concrete production, where production conditions are more easily controlled.  

We probably won't be seeing a carbon-neutral cement industry very soon. Still, based on recent works in geopolymer cement, it has cemented itself as a vital alternative to Portland cement in producing concrete structures.