Ecocem GGBS Cement

“Ground granulated blastfurnace slag (GGBS) cement is a by-product of the manufacture of iron. Because GGBS cement originates from burnt limestone, as does OPC its chemistry is similar to OPC. These similarities permit GGBS cement to replace up to 70% of OPC in concrete, on an equal-part basis. But the minor differences between GGBS and OPC also give enhanced durability to concrete made with GGBS. For most farm applications the most durable concrete will be obtained using a 50:50 blend of GGBS and OPC. In the most aggressive environments the use of 60–70% GGBS might be required.”

Protective Characteristics of Ecocem GGBS

Increased Resistance to Acids
Concrete made with GGBS cement has a lower porosity and permeability than concrete made with Ordinary Portland Cement (OPC) only. Pore sizes are smaller and less numerous. This reduces the rate of penetration of acids into the concrete, giving enhanced protection from acids, erosion and abrasion damage.
Greater Long Term Strength
Concrete made with GGBS has greater long-term strength than concrete made with OPC, due to the denser cement matrix of GGBS concrete. The same 28-day strength will be achieved in concrete with 50% GGBS as concrete made with 100% OPC. However beyond 28 days, GGBS concrete continues to hydrate and gain in strength more than concrete made only with OPC.
Increased Resistance to Sulphates
Sulphates can be present in slurry, manure and wastewater. Sulphates react with C3A and Ca(OH)2 present in OPC concrete, causing the concrete to expand and crack. GGBS is a sulphate-resisting cement. Specifying GGBS at 50%–70% content gives optimum protection against sulphate attack.
Increased Resistance to De-icing Salt
De-icing salts and seawater can cause corrosion of reinforcement in concrete leading to cracking of concrete. The presence of GGBS reduces the rate and degree to which chlorides penetrate through concrete, enhancing the service life of concrete exposed to these salts.

Environmental Benefits of GGBS

Ecocem GGBS cement is a recycled product. It is much more environmentally friendly and has a much lower CO2 footprint than CEM II or CEM I cements. The CO2 footprint of Ecocem is just 29kg/tonne (audited by NSAI), whereas that of CEM II cement is in the order of 700kg/tonne.Using a 50% blend of GGBS in concrete saves 1 tonne of CO2 per truck load of concrete delivered.On an average farm slab of 500 m2, with two silage pits, this will result in a saving in the order of 100 tonnes of CO2—equivalent to the annual greenhouse gas emissions of a herd of 40 dairy cows.

Working with GGBS Concrete

Placing and Compacting

The requirements for placing concrete with GGBS are the same as that of ordinary concrete. It is essential that all concrete should be fully compacted to ensure long-term durability. The concrete should be mechanically vibrated using a vibrating poker or vibrating screed. Compaction by hand tamping will not lead to the same quality results and may reduce the life of the concrete. It is not permitted to add water to concrete on site—doing so will significantly damage the integrity of the concrete.It is important to permit bleed water to evaporate from the concrete surface before the final finishing. Finishing the concrete whilst there is bleed water lying on the surface remixes the bleed water into the top surface of the concrete, leading to the formation of a weak layer on the top of the concrete.


Proper curing is particularly important in farm concrete. The purpose of curing is to ensure that sufficient moisture is available for hydration of the concrete in the first 7 days. Great care must be taken to ensure concrete does not dry out during this period. This can be achieved by covering the concrete with a fabric that is kept moist; covering the concrete with plastic sheeting; using a curing compound; or regular spraying with water. Failure to cure properly will result in a lower strength and more porous surface layer of concrete. This will make the concrete more susceptible to abrasion, acid attack and frost damage, and will shorten the life of the concrete. It is also important to protect fresh concrete from heavy rainfall, and from frost.

B. McCaffrey’s Experience with GGBS

Having over three years experience in production and delivery of GGBS concrete, it is also incorporated in our block production due to its beneficial properties (reduced efflorescence). Individual mix designs can be devised to the customers needs on request. Have extensively used this cement type with large wind turbine bases, pavement grade concrete and starting to expand into the shuttering market, it is a versatile product with many beneficial properties.DSC_0349                       Wind Turbine Base.

Wind Turbine Base.