Yes, this is one of the points where the somewhat lower pH when compared with Portland cement could be of interest in practice. Numerous preliminary trials indicate that a combination of Celitement with natural fibres, such as cellulose fibres, is highly suitable. There is a very good bond between the binder matrix and the fibres. Natural fibres often have a durability problem in a classical Portland cement matrix because of the very high pH values. Some natural fibres tend to decompose at a pH above 13. We have in fact only carried out preliminary exploratory trials here in the laboratory but in principle we consider this combination to be very interesting.
Yes, there is nothing against the use of Celitement in concrete made with recycled aggregate. The good sulfate resistance might even offer new opportunities here as the exposure of many recycled building materials to sulfates often represents a durability problem. In this case Celitement would certainly have advantages over Portland cement.
Celitement can be processed like classical cement so it can also be used to produce concrete furniture or decorative articles. We ourselves have already produced some fairly small articles, such as pencils holders and models of mixer trucks or road tankers made of fine mortar, with Celitement for advertising purposes. They are popular “homemade” gifts.
Yes, Celitements could form an even better bond than a classical hardened cement paste matrix. The lower calcium content reduces the formation of the portlandite double layer on the surfaces of fibres or reinforcement that disrupts the adhesive bond. However, this still has to be tested in detail. Celitements have already been used for concretes with steel reinforcement, carbon fibres, basalt fibres, steel fibres and plastic fibres. The great fineness of Celitement has also had a positive effect with some fibre fabrics as the particles can penetrate well into the intervening spaces between the fibres and in this way facilitate a good bond. However, this applies of course quite generally to any binding agents with high ultrafine fractions.
Yes, fibre-reinforced cement slabs have already been produced with Celitements. Trials were carried out in laboratories and pilot plants.
Yes, as part of university research projects we have already used Celitements for additive manufacture, e.g. for 3D printing by the extrusion method. However, 3D printing applications normally require specially formulated binding agent mixes that have been adapted to suit the task.
Yes, from our point of view there is nothing against the use of Celitement for producing railway sleepers. Celitement could even be extremely suitable for this purpose as it is, if required, a fully sulfate-free binding agent that also has no aluminate or aluminoferrite phases that lead to expansion phenomena during heat treatment (curing). However, the strict requirements for early strength must also be fulfilled.
Yes, we have proved through production trials in plants for producing concrete products such as paving stones that, in this case, Celitement can replace the cement. This can be in the high-grade face concrete as well as in the backing concrete. High-grade hermetic panels have also been produced with Celitements. It is, of course, always necessary to make adjustments, mainly to fulfil the strict durability requirements in this sector. However, in principle the existing plant technology and the established production expertise from the production of concrete products can be employed when using Celitement.
No, plain Celitements are not yet commercially available. The quantities currently produced in the pilot plant are not sufficient for this.
No, not yet, as such an approval is normally only granted for material from a defined industrial plant. We have in fact held discussions about approval issues but it is still too early to start a building authority approval procedure for structural applications. First of all our associate Schwenk, or some other building materials producer, will have to come to a decision about investment in an industrial plant. A location and the large quantity of materials needed for further practical trials, approval tests and first reference projects will then be available.
Yes, we have also tested Celitements in combination with a wide variety of interground materials from traditional cement production. Depending on the nature and quantity it is possible to produce composite building materials with differing performances in the same way as with Portland cement clinker. The big advantage of Celitement lies in the specific, much larger amount of C-S-H (the “glue” in mortar and concrete) which in principle can be formed from one ton of Celitement. Finally, with Celitement (hCHS) we have a pure preliminary stage for C-S-H. Theoretically (degree of conversion to hCHS 100% and degree of hydration in the application 100%) about 1,144 kg of C-S-H could be obtained from one ton of pure Celitement. Let us compare that to the composition of one tonne of average CEM I Portland cement. It consists of approximately 770 kg of two calcium silicates from which C-S-H can also be formed. The mineral names are tri- and dicalcium silicate, C3S and C2S respectively. If on the addition of water the total of these 770 kg calcium silicates were also completely converted into C-S-H, you would get about 477 kg C-S-H and an additional 472 kg of portlandite [Ca(OH)2]. In order to compare the potential performance of composite cements made from Celtement or Portland cement, we consider the amounts of “glue” (C-S-H) that result when mixing the binder with e.g. limestone powder. The fully hydrated variant of such a composite cement with 50% Celitement and 50% limestone powder for example could lead to the formation of 572 kg of C-S-H on application. This means 20% more “adhesive” (C-S-H) than a fully hydrated CEM I! Of course, this is only a theoretical value, but at least we have assumed ideal boundary conditions for both cases. In the future it might be possible therefore to use Celitement to produce composite cements that have significantly more C-S-H (and thus performance) than their counterparts based on Portland cement. This is one reason why we never tire of pointing out that not only the GWP (greenhouse warming potential – CO2) of the pure binding agent is looked at. It is important to consider the performance in the respective application or in combination with other constituents. Not only for Celitement but for many alternative binder concepts, lies a great potential that could be exploited in the future.
Yes, this is possible provided that these precast concrete elements are not intended for structural use. However, the amounts produced by the pilot plant are currently not sufficient for commercial precast element production. Industrial precast element production will only be possible after the industrial plant has been commissioned. The production of precast concrete elements with Celitement even offers some advantages. In addition to the high early strength and low heat of hydration the light colour of Celitement is also helpful for producing outstanding grades of fair-faced concrete.
We have identified a total of 20 areas of application for Celitements in which we expect relatively rapid entry to the market. Six of these areas are at present only at the “exploratory” stage. Different Celitements (this involves a whole class of hydraulically active calcium hydroxysilicates –hCHS-) have already been used in a wide variety of concretes (normal concrete, UHPC, steel fibre reinforced concretes, insulating concretes, etc.), mortars, tile adhesives, filler compounds, plasters, fibre-reinforced cement slabs, aerated concrete, concrete products and small prefabricated elements as well as for the production of insulating aggregates. When dealing with the fields of use of cement one is repeatedly astonished at the number of different applications in which this hydraulic binding agent is now being successfully used. With Celitement we are going to try to gain a foothold wherever Portland cement has already proved successful although we may gradually also open up some completely new applications.
No, because Celitement is not a standardized building material. It may therefore only be used in constructive applications with an approval by the national building inspectorate. The respective tests, as part of the official approval process from the German Institute for Building Technology (DIBt) , have already started. Material from the pilot plant is expected to be approved in early 2025 and a few months later we expect approval for material from the first industrial plant. Until then, you have to be patient for use in constructive components or apply for an object specific approval.
It should be noted here that in many applications it is in fact often very easy to use Portland cement which is one of the reasons for its outstanding success. However, there are numerous applications in which Portland cements are used that only function satisfactorily if there is a very good understanding about precisely how the different clinker phases interact with each other and with other additions. Even now not every developer or concrete technologist is able, with basically the same available starting materials, to produce equally efficient building materials (e.g. concretes). This also applies to the use of Celitements. In principle, Celitement is just as easy or difficult to use as Portland cement. However, the end result can differ depending on the mix formulation of the binder system, the inventiveness and skill of the developer and sometimes also simply the luck with the formulation. In most cases the best results have been obtained by the innovators who have re-thought the application when using Celitement and not just simply interchanged the binding agents. A simple interchange can be successful but is not necessarily the best way to utilize the potential of Celitement.
From the material point of view Celitements are probably suitable for this purpose. However, we haven’t yet gathered any experience in this very specialized field. As a rule, special cements based on apatite are used for dentistry. These cements differ very widely in material content from Celitement. Approvals for medical applications are also very time-consuming and expensive so at the present we have not developed any activities in this field. However, we would be happy to make sample material available for research purposes.
No, Celitement is not yet commercially available. The quantities currently produced in the pilot plant are not sufficient for this.
This is the almost unbeatable price/performance ratio of classical Portland cement and the enormous amount of experience with it that its users have collected over the last 150 years. Portland cement and the “glue” produced with it in concretes and mortars, the C-S-H phases, are even now still not fully understood in every detail. This is astonishing for a building material of which about 4 billion tonnes are produced worldwide every year. It is therefore very difficult for a completely new binding agent like Celitement to be successful in the market when “only” the ecological footprint is better. Many users of classical Portland cement are also hesitant to change their proven mix formulations and replace what they consider to be safe system solutions, sometimes with practical knowledge gathered over many years, by a new system. We are therefore banking on the technological added value of Celitements and the advisory service that this will require.
No, Celitements can be supplied, stored and processed exactly like classical cements.