Benefits of Cement with Additives
There is a widespread myth among cement consumers in Ukraine that the presence of active mineral additives in cement means its low quality and, consequently, strength. This opinion has no practical confirmation. Moreover, today the world cement market prefers cement containing mineral additives because they improve cement and concrete's physical and mechanical properties.
In Ukraine, the most often used mineral additive to cement is blast furnace granulated slag, and in recent years the use of limestone has been gaining in popularity.
Cement with mineral additives can ensure increased concrete durability, better resistance to aggressive environments, lower heat evolution, and a reduced risk of cracking in mass concrete structures. Granulated blast furnace slag and limestone are among the common mineral components. Their effect on cement and concrete properties depends on the type and amount of additive, cement composition, and application conditions.
What mineral additives are used in cement?
Blast furnace granulated slag
is a by-product of the metallurgical industry. By its origin, slag is a burnt residue of waste iron ore, which contains compounds similar in chemical composition to the minerals of portland cement clinker. These compounds are formed due to high-temperature treatment and subsequent rapid cooling. One of the strong arguments favouring this material for cement production is its hydraulic properties. The binding properties of blast furnace granulated slag are activated in the course of grinding in cement mills and as a result of chemical interaction with clinker minerals and gypsum.
Limestone
in the aquatic environment becomes chemically active towards certain elements of portland cement clinker and chemically reacts with its minerals. Eventually, strong compounds are formed in the contact zones.
Benefits of cement with mineral additives:
Higher frost resistance, water impermeability and durability of concrete
Concretes made with cement with additives have a denser structure. When cement with granulated blast furnace slag is used, both clinker and slag are involved in the setting process, so the reaction results in more complex minerals than cement without additives. Meanwhile, fine limestone fills the voids between cement grains, improves the reaction between them and the water, and promotes the formation of denser cement stone by reducing the total porosity.
Even greater strength over the years
In the initial stages, blast furnace slag cement gains strength slightly more slowly than ordinary portland cement. However, after two weeks, strength gaining is accelerated. From the 7th month, it increases to 50% of the declared strength class (depending on the blast furnace granulated slag content in the cement).
Lower risk of cracks during the construction of solid structures
The presence of blast furnace granulated slag in cement helps to reduce the hydration temperature, decreasing the temperature difference during the construction of solid structures and, consequently, reducing the risk of cracking.
Lower risk of efflorescence
Cement with active mineral additives contains less soluble substances that, in the process of hydration (interaction of cement with water), migrate to the surface of the concrete product to form efflorescence.
More convenient pouring of concrete
The concrete based on cement containing blast furnace granulated slag sets more slowly due to blast furnace slag cement's slowed down the setting process and the lower hydration temperature. That is why it is recommended to use cement with slag in hot weather. Cement without additives quickly loses workability at high temperatures.
High resistance to aggressive environments
Blast furnace granulated slag increases the resistance of cement stone to aggressive environments: sulphate resistance, acid resistance, resistance to alkaline aggressions, seawater, carbonisation, etc. All this is due to a reduced content of Ca(OH)₂ and the hydration products of the aluminate phase of the portland cement clinker in the cement stone.
Caring about the environment
Clinker production involves quarrying for minerals and then burning them, which leads to СО₂ emissions. The production of 1 t of clinker is accompanied by the release of 1 t of СО₂. When part of the clinker in cement is replaced with active mineral additives, it helps reduce СО₂ emissions and solve environmental problems such as global warming and depletion of natural reserves.
How mineral additives affect concrete properties
| Property | Вплив мінеральних добавок | Практичне значення |
| Durability | promote the formation of a denser structure in the hardened cement paste | increased water impermeability and frost resistance |
| Strength gain | slag cements continue to gain strength at later ages | ensuring necessary structural performance over the long term |
| Heat evolution | granulated blast-furnace slag helps lower the heat of hydration | reduced risk of thermal cracking in mass concrete structures |
| Eflorescence | reduces the amount of soluble substances capable of leaching to the surface | reduced risk of efflorescence appearance |
| Hot-weather operations | concrete retains workability longer | more convenient concrete placement |
| Aggressive environments | increases resistance of the hardened cement paste to aggressive actions | application in conditions exposed to sulfates, seawater, and other aggressive environments |
| Environmental impact | part of the clinker is replaced with mineral components | eduction in clinker usage and associated CO₂ emissions from its production |
FAQ about cement with mineral additives
| The presence of mineral additives alone does not mean lower cement strength. The properties of cement are determined by its composition, strength class, and compliance with regulatory requirements. |