New Clinker and Cements Obtained from an Eco-efficient Process. Building Materials- Materials. Technology Transfer Office

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CSIC NM037- New Clinker and Cements Obtained from an Eco-efficient Process

Three Spanish Research Centers have patented a new belite cement clinker from coal combustion fly ash of high lime content, and new belite cement. This new process brings back important energetic and environmental advantages, such as a dramatic reduction of the processing temperature, a clear reduction of the grinding needs, a lower CO2 emission and the elimination of an industrial by product. They are looking for Industrial Partners to license agreement.

Specification sheet:

DESCRIPTION

This invention is related to a new belite cement clinker from coal combustion fly ash of high lime content, which is formed mainly by the alpha prime of low temperature dicalcium silicate (?’ L-Ca2SiO4), and containing elements such as Fe, Al, Mg, Na and K that increased the reactivity of ?’ L-Ca2SiO4 .

The main characteristics of that clinker are the following: (1) Fly ash of coal combustion of high lime content is used as raw material providing the elements that increase the reactivity of belite phase together with the CaSO4 that act as regulator of setting. The CaO/SiO2 molar ratio of the fly ash must be at least 2, introducing additional amounts of CaO in the case of minor CaO/SiO2 molar ratio. (2) It is not necessary to incorporate lattice stabilizers in the raw mix, such as Fe, Al, Na or K, since they are present in the fly ash. (3) It is not necessary an excessive grinding, due to both the low synthesis temperature (800ºC) at which it is not reached the fusion of phases and the high surface area of the fly ash. (4) It can be used directly as cement without additional CaSO4.

The main characteristics of the belite cement from coal combustion fly ash of high lime content are the following: (1) it is formed 100% from the previous clinker, (2) during its hydration a minimum amount of Ca(OH)2 is formed, ensuring a good durability in those aggressive ambient in which the Ca(OH)2 produces expansive reactions, as it is the case of sulphate attack. (3) The standard mortars produced from this belite cement reach similar strength at 7 days as usual mortars produced from OPC, provided that belite cement mortars are cured at 40 ºC and water reducing additives are used.

Furthermore, this new cement provides important energetic and environmental advantages during its fabrication since both the synthesis temperature (800ºC vs 1450ºC) and CO2 emissions (0 CO2 emissions under certain conditions) are drastically reduced. Besides a waste and its landfills storage are avoided. The worldwide production of fly ash is about 600 mega tons per year, which will increase exponentially in the near future due to the energy demand for industrial and domestic uses. As a consequence, these advantages will have an important economic repercussion due to the reduction of the implicated costs.

INNOVATIVE ASPECTS

The main innovative aspect of the belite cement clinker is the use of fly ash of coal combustion of high lime content as principal raw material. The technical characteristics are: i) ?’ L-Ca2SiO4 is the main component, ii) it contents elements such as Fe, Al, Mg, Na and K that increase its reactivity, ii) it does not need to be ground excessively, and iii) it can be used as cement directly without additional CaSO4, since fly ash already contains it.

By an accelerating curing at 40ºC and the employment of water reducers, so made belite mortars can reach at 7 days mechanical strengths similar to those achieved by their Portland counterparts.

COMPETITIVE ADVANTAGES

The production process of this product affords cost reductions for the following reasons:

There is a radical reduction of the temperature of the synthesis (800 ?C vs 1450 ?C)

There is a reduction of the needs for the grinding process

There is a CO2 emission reduction during the furnace process. The CO2 emission could even get to be 0. This fact can be a key factor towards the fulfillment of the Kioto Protocol (and thus avoid the purchase of emission rights)

Waste from an industrial process is used as raw material. This implies a reduction in the exploitation of natural resources and therefore a cutback in quarry exploitation expenses.

From an energetic perspective, one has to bear in mind that the energy demand for industrial and domestic uses will significantly increase in the near future. This will give rise to dramatic environmental problems caused by the storage of that fly ash (the worldwide production of fly ash is about 600 mega tons per year). Therefore, the production process of this cement provides several advantages. First of all, this process reuses the waste of an industrial process thus contributing to the sustainable development. It also uses the fly ash rubbish dumps produced by the combustion of high lime content coal.

KEYWORDS

Belite cement clinker, fly ash of coal combustion of high lime content, Eco-efficient Process.

002006001 Building Materials, Components and Methods

002007002 Building Marterials

010002001 Air Pollution

PATENT

200301504, applied for at 2003-06-27

CONTACT

JOSE MARIA BIELZA DE ORY
email: M.Bielza@orgc.csic.es
phone: +34 915616800 (ext. 3231)

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