Who we are
Green Construct ALS Limited (GCALS)
We adopt innovative and environmentally friendly construction practices, assuring quality construction materials and support services to the general public and keep the green economy agenda on track
Learn MoreFrom Lab to Industry
CALCINED ALUM SLUDGE
We use wasted alum sludge as replacement for clinker. This has the potential to stabilize the prices of cement locally and also could save Ghana some forex.
Dig DeeperProcess Highlight
Grinding of the Dried Sludge
During further processing, the dried alum sludge is milled and ground to the desired texture in our labs.
Get Started01
Quality Standards
Construction materials such as concrete and sandcrete blocks can be tested for strength and other qualities and results delivered within 72 hours. We do site-testing or off site (lab testing). Informal block producers subscribe to our quality services and certification to increase their market penetration
02
SDGs Aligned
Specifically, we contribute to Goals 8, 9, 11, 12, 13, 14 and 15
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Built Environment Focused
Innovative and environmentally friendly solutions for Construction Sector
why calcined alum sludge?
Reducing Clinker Importation
Cutting CO2 Emissions
Reducing clinker importation and trade is a sure way of cutting CO2 emissions, producing more sustainable construction materials and bringing in low-carbon path for cement production.
We are working with international partners. Funding support is provided mainly by the Netherlands Enterprise Agency (RVO). Our partners include:
Spaak CS
Royal HaskoningDHV
Netherlands Enterprise Agency
Ghana Standards Authority
Ghana Water Company
The GoodRoll
AT A GLANCE
What is
Calcined Alum Sludge?
Alum sludge is a by-product of drinking water treatment in water treatment plants where aluminium salt is used as a coagulant. AS is an aggregate of organic matter, humic particles and colloidal suspended solids.
Toxic to Aquatic Habitats
Poses ecological risk according to United States Environmental Protection Agency (USEPA)
Portland Cement Clinker Replacement and/or Viable Binding Material
The product can replace up to 25% of Portland cement clinker and/or has the capacity to replace up to 15% of the binding material for sandcrete block production
Our Footprint
We Aim for Global Presence
Where we are now
Ghana
We are currently operating from our Ghana office where we are actively carrying out Research and Product Development (R&D). Scaling up and commercialization is expected in 2026.
What Our Partners are Saying about us
USEPAUnited States Environmental Protection Agency
Ghana Water Company-WeijaStation Manager
Want to Learn more about our work?
We are delighted that you take an interest in what we do. You can get more information about our research, key milestones, industry partners and more. Contact us via email: info@greenconstructals.com
Key Facts & Stats
Potential of Calcined Alum Sludge
Of Portland Cement Clinker Replacement
Of Cement Replacement as Binding Material
Events & Latest News
Get all the events and latest news about the work of Green Construct ALS Limited (GCALS). We will carry you along in this exciting journey of innovation into a green sustainable society.
This week’s heavy rains were yet another painful reminder: Ghana’s urban infrastructure
Mr. Asiedu Evans (second from the left) At Green Construct ALS Ghana
At GCALS, we are dedicated to transforming Ghana’s construction industry by promoting
The building sector accounts for over 40% of global energy use and
