DE202013102906U1 - Concrete product with clinker brick appearance - Google Patents

Abstract

Concrete product (10, 20, 30, 40 50, 60) with clinker brick appearance, characterized in that the cement paste comprises at least a partial volume (16), in particular of the entire concrete volume fireclay (18), in particular clinker particles, wherein the surface of the concrete product (10, 20, 30, 40 50, 60) by mechanical finishing an adjustable surface texturing, molding of an adjustable surface texturing and / or surface design has.

Description

STATE OF THE ART

The invention relates to a concrete product in which a clinker brick optics can be achieved by admixing fireclay particles

For the building material concrete, granules such as sand and gravel and, if necessary, concrete admixtures are added. Cement glue is a viscous mixture of cement and water and forms the basis for concrete.

Concrete admixtures are water-soluble or slurried chemical substances that can be admixed to the concrete in order to enhance, by physical and / or chemical effects, the properties of the fresh or hardened concrete, i. the cement paste, such. As workability, setting behavior, hardening or durability to change. Concrete additives are usually added in liquid form and in small amounts. The addition, based on the cement weight, is generally in the range of 0.2-2%.

The main additives are concrete plasticizer (BV) and plasticizer (FM), air entraining agent (LP), accelerator and retarder (VZ).

Generic concrete or paving stone products usually have a core (core concrete) and a surface layer (facing layer, top layer), which is also referred to as facing concrete. The facing layer is the visible layer of the concrete product that determines the visual appearance of a building to be created. The intent or cover layer is selected by the choice of cement usually as white or gray cement in the form, color and size of the aggregate depending on the application and may contain pigments for color design of the surface. Pigment size and aggregate size, color and size can be varied. The aggregate is usually chosen so that a dense grain packing is formed and the attachment layer is as water and airtight as possible. The core layer is the non-visible layer below the facing layer, which is responsible for the volume and weight of the concrete product and its stability. The core concrete is in its formulation and consistency usually coarser than the facing layer, since the core concrete in the installed state does not determine the appearance of the product and must meet only the mechanical requirements.

The known concrete products have an unsightly substantially homogeneous smooth "concrete surface" and are to embellish especially in the visually sophisticated interior design only by high effort by post-processing or disguise attractively.

The DE 3621838 C1 describes a fired concrete block with glass slag flour as an additive, wherein the glass slag flour originates as a waste utilization from a glass jet plant. The concrete block is characterized by a low lime content, a large proportion of trass cement and chamotte.

The mixture of trass cement is approx. 5%, chamotte approx. 5-20% and approx. 50% water, as well as the remainder clinker cement for the raw material. The concrete block is fired and is very light, but not very strong, the strength can be adjusted by the proportion of chamotte.

The concrete block can be poured and glazed during production. It is well suited for use in tunneling, in power plants of the chemical industry, for interior fittings, furnace construction or façade elements. However, the concrete block neither has an attractive clinker brick appearance, nor are its mechanical properties satisfactory.

The object of the invention is to overcome the above-mentioned disadvantages of the prior art and to produce a concrete with an appearance of a clinker.

DISCLOSURE OF THE INVENTION

According to the invention, the object is achieved by proposing a concrete product with clinker brick appearance, the cement paste comprising at least a partial volume, in particular the entire concrete volume of fireclay particles, in particular clinker particles. For this purpose, the surface of the concrete product by mechanical finishing an adjustable surface texturing and / or surface design. By means of a mechanical reworking, for example a brushing, stamping or the like, a texturing of the surface can be achieved. The texturing may also be done by taking an adjustable surface texturing impression, which may be microfine, i. Structures <1mm, in particular <100μm may have. Thus, a flat stamp or a surface-structured plate can be pressed into the surface of the not yet cured concrete product, or achieve a structuring after curing by a pressing operation.

One aspect of the invention is the addition of chamottes in the cement paste. Fireclay are made of refractory bricks, and mostly made of sintered clay. The addition of chamotte brings together the technical and design properties of concrete and clinker.

As a result, a concrete block can be made with the appearance of clinker, in which at least in the facing concrete fireclay particles are incorporated. Fireclay are basically fired clay or kaolin.

• – Einsatz eines maschinellen Verfahrens des Darüberstreichens, bzw. Einsatz eines Stempels,
• – die Herstellung eines sehr feinen Vorsatzes, damit die Schamottsteinchen zur Geltung kommen,.

A visual change of concrete surfaces by the addition of chamotte, especially in the facing layer in conjunction with the post-processing of Drüberstreichens to achieve the effect of clinker optics can be achieved by:

• Use of a mechanical method of sweeping, or use of a stamp,
• - The production of a very fine intent, so that the fireclay stones come to bear ,.

If the concrete product is multi-layered, a core concrete can be placed in a mold and a layer of facing concrete with fireclay particles deposited thereon. Thus, in an advantageous development, at least one cover layer consists of a cover layer concrete and a core layer of a core concrete, wherein only in the cement paste of the top layer concrete fireclay particles are included, and the cover layer by mechanical finishing an adjustable surface texturing and / or surface design. The excessive amount of concrete product can be used with unchanged base formulation, i. Cement, water, and aggregate can be produced, and both in appearance and in the construction of the core concrete and the facing layer to be maintained in order to maintain a low price of the concrete product. The facing concrete can be colored, brushed or mechanically processed, the fireclay particles lead to a clinker appearance of the concrete block.

With regard to the cement size, the hydraulic binder of the cement advantageously comprises alite (tricalcium silicate-3CaO-SiO ₂ ), belite (decalcium silicate-2CaO-SiO ₂ ) or brownmillerite (dicalcium aluminate ferrite-2CaO-Al ₂ O ₃ or 2CaO-Fe ₂ O ₃ ), respectively in conjunction with calcium aluminate and free calcium, ie lime.

According to an advantageous development, the cement paste can amount to at least 15% to 21% by weight of at least one partial volume, in particular of the total concrete volume. The cement paste usually consists of a mixture of trass cement and water. Accordingly, the maximum content of fireclay particles is 79 to 85% by weight of the part of the concrete product or concrete product produced from clinker concrete. By a variation of the fireclay content, the concrete strength and the associated dense surface is adjustable. Furthermore, the chamotte particles can advantageously comprise highly fired clinker particles which are fired at temperatures> 1,300 ° C., in particular at 1,350 to 1,450 ° C. Thus, a binary system of silicon oxide and aluminum oxide SiO ₂ -Al ₂ O _{3 is} proposed.

In the cement hydraulic binder, chamotte or clinker are preferably introduced in a proportion by weight of 20% to 70%, which thus have the following advantages over conventional concrete products:
With regard to the solid-state structure, the combination of the phases of cement and chamotte / clinker has the advantages that the individual phases influence one another and create an improved microstructure and macrostructure in comparison with fireclay or clinker products per se. In the case of suitable machine-usable production forms, instead of conventional concrete paving stones, unfired clinker paving stones, bricks, facade stones can be produced, wherein no additional color or coloring of the concrete matrix must be used. Production of a facing layer with conventional core concrete layer or exclusive use of the clinker concrete as a facing layer is possible, so that the strength and characteristics of ordinary concrete block products and the appearance of clinker products can be achieved. The clinker concrete block products correspond to optically fired clinker bricks, whereby less fired clay and thus less energy must be used in the production per unit volume. The fireclay can be made from recycled clinker bricks, bricks or brick dust so that no clay has to be rebuilt and thus no additional firing energy has to be used for new clinker concrete blocks. Thus, the clinker particles can come from both new production and from a secondary raw material, such as brick and clinker bricks. As a result, a clinker-type concrete block can be provided at a much lower cost in large quantities, with prices well below 50% of the production price of a pure clinker brick can be achieved.

Due to the proportion of fireclay, the thermal conductivity of cement is significantly reduced, so that the proposed clinker concrete product reaches a significantly higher thermal resistance than a conventional concrete product. Thus, the thermal conductivity of concrete is typically λ = 2.1 W / (m · K), and clinker or brick a thermal conductivity of λ = 1.2 W / (m · K) based on a product density of 2200kg / m ³ . Furthermore, advantageously, the thermal conductivity by a additional use of pore-forming agent or slag can be additionally improved.

As a further advantage, the reduced heat storage of the clinker concrete product compared to conventional concrete products, especially in buildings for a heat and heat protection can be called. Also, in terms of fire protection, the heat resistance of the construction product against fire is improved by the addition of fireclay particles.

According to an advantageous development, the fireclay cement paste may comprise, as an essential component, polyurethane which is mixed with the fireclay in order, in particular in the open-pore range, to increase the freeze-thaw resistance of the concrete to freezing and frost. Instead of finished cement can thus be used in conjunction with chamotte polyurethane.

Under texture or texturing is understood below a surface design that is carried out by a targeted three-dimensional surface structuring. This can be achieved with a cement paste of a not yet cured concrete product by pressing or stamping means of a corresponding negative mold. Also, a mechanical post-processing such as shot blasting, sandblasting, grinding and the like can specifically change the surface of the concrete product, i. texturing.

According to an advantageous development, the fireclay cement paste can be prepared by adding chamotte particles, in particular clinker particles with a grain size of 0 mm to 2 mm, preferably 0 mm to 0.5 mm, in particular in the grain size 0 mm to 0.1 mm, preferably further Additives, preferably fine sand, in particular in the grain size 0 mm to 0.2 mm is added. The chamotte is composed here of a fine grain, from 0 mm to 0.5 mm, in particular 0mm to 0.1 mm and from 0 mm to 2 mm grain size. The fine grain is responsible for the density of the cement paste, the coarser grain size up to 2mm, especially for structuring the concrete surface. This advantageous size of the fireclay particles achieves uniform calcite and mullite phase formation, in particular web formation with mullite phases in the cement-stone matrix, whereby a dense concrete-stone matrix can be obtained which enables a micro-fine texture mapping and which reproduces the typical sharp-edged fracture behavior of brickstones. Additional aggregate grains, preferably chippings in grain sizes of 1 to 3 mm, can be added.

According to an advantageous development, the cast concrete product, (in particular the fireclay cement paste of the cover layer) can be colored by a subsequent application with oxides, preferably natural materials such as titanium dioxide and iron oxides are used, which may be embedded in acrylates, wherein the macro layer in color is accentuated.

In this way, any coloring or improved coloring of the concrete product can be achieved, so that the surface reaches a high color fidelity even with high mechanical stress in the long term.

According to an advantageous development, the cast concrete product can be used unfired cured, as would otherwise be necessary for ceramic, which would have to be fired first. Thus, a ceramic-like concrete product can be provided without performing additional costly and time-consuming firing and curing processes.

According to an advantageous development, the surface texturing can be produced by a mechanical brushing, brushing, wiping or stamping process, in particular by a mechanically produced texturing process. The texturing can be produced, in particular, by molding a stamp, and / or by molding a base board made of wood or a metal substrate, in particular a drawing sheet, and / or a mold bottom and / or by mold walls. If, for example, the underside of the concrete product, which is made only of top layer concrete, textured, the product underside is the top of the surface to be laid. The stone product is thus rotatable.

A subsequent surface finishing by milling, grinding or other common surface modification such as sandblast or shot peening can be performed. The viewed in the production process as the bottom side surface of the concrete block product can be textured by a pad board and used as the top in the laying or in the use. It is particularly suitable to texture the surface of a stamp and / or mold side walls and / or a mold bottom in such a way, ie to design the surface design of the curing of the concrete product such that the desired surface design can be achieved. The surface design of the stamp or of the mold walls or the mold bottom can be produced by a Holzmaserstrukturierung, an arbitrarily adjustable plastic or Steinoberflächentexturierung or metal surface texturing. Furthermore, plastic coatings, such as two- or three-dimensionally designed net-like or foil-like coatings of the surfaces are conceivable with which a desired adjustable Texturing of the concrete product surface can be generated. Textile or mesh surfaces as well as fiber-structured surfaces may also be conceivable for introducing a surface texturing.

According to an advantageous development, the surface of the concrete product may be finished with a surface protection in order to obtain a color brilliance. Thus, a surface coating, such as a nanoparticle and / or color coat, can provide improved dewatering or resistance to contamination, thus increasing longevity and cleanliness of the product surface. The surface protection may include acrylates, sol-gel coatings, general-purpose plastics and other surface protection systems for concrete block products. Known impregnations, sealants and coating systems for concrete block products can be used for surface protection.

Alternatively or in addition to a surface protection, color-permeable substances can be applied to the surface of the concrete product during the cement mixture, the hardening process or when the concrete product has already hardened by mixing, spraying, spraying or rolling on. Thus, it has been shown in the curing of the clinker concrete that lighten the color of the concrete product sets by the existing free lime in the cement matrix and by the evaporation of the free water. In order to maintain and improve the clinker optics, color enhancement substances can already be mixed in during the curing process or subsequently applied, in particular on or sprayed in, mixed in or rolled on, in order to reinforce and preserve color tones during the curing process. Thus, advantageously color-enhancing and color-retaining dispersions containing, for example, synthetic resins, acrylates, plastics, and which are suitable for spraying, brushing, dipping or rolling. These should be applied when applied to the surface of the concrete product for permanent and sustainable color enhancement with an application rate of 50 to 100 mg / m ² , in particular 60 to 80 mg / m ² . Advantageously, when mixing in the top layer of the concrete product dispersing additives in a proportion of 0.1% to 0.8%, in particular 0.4% to 0.6% based on the cement content and on the binder in the top layer concrete mix for the outer concrete cover layer are mixed , Alternatively, the dispersing additives may be blended in the above weight ratio into the cement for the entire concrete product.

According to an advantageous development, in addition to the fireclay particles, the refractory cement paste may comprise IR-reflecting and / or photocatalytic additional particles, in particular mica, metal powder pigments and / or a metallic semiconductor compound, in particular metal-tin oxides.

According to an advantageous refinement, heat-insulating and / or impact-sound-absorbing additive particles, in particular polystyrene particles, expanded clay or expanded glass particles can also be included in the cover layer and / or in the core layer. Thus, additional properties such as the insulating effect, radiation of heat, etc. can be achieved by IR-reflecting particles, photocatalysis and self-cleaning by titanium dioxide particles.

According to an advantageous development, the fireclay particles can account for 10% to 80% by weight, in particular 20 to 67% by weight of the fireclay cement paste, with preferably up to twice the amount by weight of fireclay particles being added to the usual cement dust.

According to an advantageous development of the cover layer concrete may have a thickness of 3 to 20 mm, preferably 5 mm to 10 mm, and the top layer concrete by mixing the fireclay into a cement slurry produced and applied to an already cast core layer and curable, the core layer substantially Volume, shape and stability of the concrete product provides.

Finally, in an advantageous embodiment, the concrete product may be designed as a paving stone, as an external facade stone, as a brick or as a roof tile. Especially at high mechanical loads, such as roadway or Fußplanbepflasterung can be achieved by mixing the particles in the matrix of Decksichtbetons a high longevity and attractive appearance compared to ordinary concrete surfaces.

• – Nachstellung der Klinkeroptik mit geringem, technischen Aufwand;
• – Tonige, erdige Farbgebung;
• – Kombinationsmöglichkeit mit natürlichen Oxiden;
• – Aufnahmefähigkeit des Wassergehaltes im Anmischprozess
• – Wärmedämmfähigkeit;
• – Vielfältige Produkte sind unabhängig von Brennprozessen möglich;
• – Brandschutz, feuerfest;
• – Widerstandsfähigkeit aus Aggressivwässer;

Advantages of the invention in terms of concrete properties are:

• - Adjustment of clinker optics with little technical effort;
• - Tonal, earthy coloring;
• - possibility of combining with natural oxides;
• - Absorbency of the water content in the mixing process
• - thermal insulation capability;
• - Diverse products are possible regardless of firing processes;
• - fire protection, fireproof;
• - resistance from aggressive waters;

In a secondary aspect, the invention relates to a cement mixture, which can be ready for processing, for example, as ready-mixed concrete, or as a cement, for example as bagged goods, wherein the cement mixture comprises fireclay particles for producing the cement paste for an aforementioned concrete product. The cement mixture is prepared ready for use according to the properties of the concrete product described above and intended to be used as a cement paste, for example dissolved in water for producing at least a partial volume, in particular a cover layer or partial volume of the concrete product. The cement mixture is thus an essential element for producing the concrete product with clinker brick appearance and its composition determines the clinker brick appearance of the concrete product to be produced. The chamotte particles admixed with the cement or polyurethane may have the abovementioned properties and may contain coloring particles, in particular colored sands, oxides, IR-reflecting and / or photocatalytic, heat and / or impact sound absorbing additive particles or the like. The cement mix provides a ready-to-use mix for the simple and cost-effective production of any concrete products that can be pre-produced as well as used directly on a construction site for customizing a concrete product.

DRAWINGS

Further advantages result from the present description of the drawing.

In the drawings, embodiments of the invention are shown. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

Show it:

1 a paving stone of an embodiment according to the invention of a concrete product with an enlarged fireclay structure of the cover layer concrete;

2 an embodiment of a piling stone according to the invention;

3 an embodiment of a capstone according to the invention;

4 an embodiment of a jacket stone according to the invention;

5 an embodiment of a brick according to the invention;

6 an embodiment of a solid casing stone according to the invention.

EMBODIMENTS OF THE INVENTION

In the figures, the same or similar components are numbered with the same reference numerals.

1 shows a paving stone 10 that's made of a core layer 12 and a cover layer 14 consists. The cover layer 14 is made of durable and abrasion-resistant concrete, which is impermeable to air and water, and of a slight thickness compared to the core layer 12 having. In the matrix 16 of the top layer concrete 12 are fireclay particles 18 mixed, which cause a clinker-optically pleasing appearance.

Such a paving stone 10 can be designed as a brick NF with the dimensions 24 × 11.5 × 7.1 cm. The ratio of the component thickness to the thermal conductivity of such a brick would be R = 7.1 cm / (2.1 W / (m · K)) = 3.38 when using concrete. By using a clinker concrete, this ratio can be improved to R = 4.43 with a thermal conductivity of λ = 1.6 W / (m · K).

In the 2 to 6 other concrete products for different applications are shown. So shows 2 a piling stone, as he can serve as a paragraph stone for a roadway or a pedestrian crossing, for example, and on two sides a cover layer 14 made of shamot concrete around a core made of core-layer concrete 12 having.

In 3 a capstone is shown, as it can be used for example as a roof crown or as a crown, and on the surface and on both sides of a clinker-optical cover layer 14 having.

4 shows a coat stone 40 For example, for the construction of a free-standing stile or stone strut fully encased with a cover layer 14 is clad in clinker-optical material.

5 shows a brick 50 as it can be used to build a Einziegelmauer, on both sides of a clinker-optical coating 14 wearing.

Finally shows 6 a solid shell stone or full volume stone 60 how it can be universally used for all types of concrete block product. Both the top 24 as well as the bottom 22 of the paving stone 10 can be textured, with both bottom 22 as well as top 24 can be used as a visible side for a paving, this simplifies the handling of the paving stone 10 while processing.

The texturing on at least one of the side surface, in particular the underside 22 can be done by means of a paper board made of wood, metal or plastic, wherein the texturing of the cured in the manufacturing process or in the curing process paving stone 10 by own weight or a pressing process of the paving stone 10 can be done on the document board. The underside textured by this 22 can be used as a top when processing the paving stone in a paving or as a brick.

A texturing can be done by a surface design of the stamp, the mold bottom and / or the mold side walls. It is conceivable to use various forms for laying concrete slabs, e.g. for façade cladding or footpaths. Thus, molds for concrete slabs with a single texturing side can be provided as a visible surface in which there is texturing of the stamp or of the mold bottom. Other shapes are provided for texturing both the viewing surface and edge or corner panels in which the visual surface and one edge, or two, three or more edges, can be textured by appropriately shaped mold sidewalls upon curing of the cement paste. As a result, lying in a plane plates only have a Sichtoberflächentexturierung and untextured edge surfaces, while edge or corner plates in the side view have a desired texturing. The texturing may have microscopic dimensions, but may also be macroscopic, and may include random structures or represent ordered structures, particularly symbols, images, characters, or the like.

It is also conceivable to use a concrete product as a roof tile, which consists essentially of a core concrete, and a thin top layer with clinker-optical Schamottpartikeln 18 contains, by a roof surface is very resistant, looks visually appealing and, for example, by adding more IR-reflecting particles, a large part of solar heat can throw back into the atmosphere.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 3621838 C1 [0007]

Claims (15)

Concrete product ( 10 . 20 . 30 . 40 50 . 60 ) with clinker brick appearance, characterized in that the cement paste of at least a partial volume ( 16 ), in particular the total volume of concrete fireclay ( 18 ), in particular clinker particles, wherein the surface of the concrete product ( 10 . 20 . 30 . 40 50 . 60 ) has an adjustable surface texturing, impression of an adjustable surface texturing and / or surface design by mechanical post-processing. Concrete product ( 10 . 20 . 30 . 40 50 . 60 ) with clinker brick optics according to claim 1, characterized in that the cement paste contains at least 15% to 21% by weight of at least one partial volume ( 16 ), in particular the total concrete volume and the fireclay ( 18 ) high fired clinker particles fired at temperatures> 1,300 ° C, especially at 1,350 to 1,450 ° C include. Concrete product according to claim 1 or 2, characterized in that at least one cover layer ( 14 ) from a cover layer concrete ( 16 ) and a core layer ( 12 ) consist of a core concrete, wherein only in the cement paste of the cover layer concrete ( 16 ) Fireclay particles ( 18 ) are included. Concrete product according to one of the preceding claims, characterized in that the fireclay cement paste comprises as an essential component polyurethane with the addition of the fireclay particles in order to increase the freezing and freeze-thaw resistance of the concrete, especially in the open-pore area. Concrete product according to one of the preceding claims, characterized in that the fireclay cement paste by addition of fireclay ( 18 ), in particular clinker particles with a grain size of 0 mm to 2 mm, preferably 0 mm to 0.5 mm, in particular in the grain size 0 mm to 0.1 mm can be produced, preferably further additives, preferably fine sand, in particular in the grain 0 mm is added to 0.2 mm. Concrete product according to one of the preceding claims, characterized in that the concrete product ( 10 . 20 . 30 . 40 50 . 60 ), in particular the fireclay cement paste of the top layer ( 14 )) is colored by a subsequent application with oxides, wherein preferably natural substances, such as titanium dioxide and iron oxides are used, which are embedded in acrylates, whereby the macro layer is accentuated in color. Concrete product according to one of the preceding claims, characterized in that the concrete product ( 10 . 20 . 30 . 40 50 . 60 ) can be used unfired cured. Concrete product according to one of the preceding claims, characterized in that the surface texturing by a mechanical brushing, brushing, wiping or stamping process, in particular by a machine-processable texturing, by molding a stamp, and / or by molding a pad board made of wood or a Metal underlay, in particular a drawing sheet, and / or a mold bottom and / or can be generated by mold walls. Concrete product according to one of the preceding claims, characterized in that the surface is refined during the cement mixture, during the curing process or subsequently by Farbvertiefersubstanzen and / or a surface protection in order to obtain a color brilliance. Concrete product according to one of the preceding claims, characterized in that in the fireclay cement paste in addition to the fireclay ( 18 ) IR-reflecting and / or photocatalytic additive particles, in particular mica, metal powder pigments and / or a metallic semiconductor compound, in particular metal-zinc oxides are included. Concrete product according to one of the preceding claims, characterized in that in the cover layer ( 14 ) and / or in the core layer ( 18 ) Furthermore, heat and / or impact sound absorbing additive particles, in particular polystyrene particles, expanded clay or expanded glass particles are included. Concrete product according to one of the preceding claims, characterized in that the fireclay particles ( 18 ) Make up 10% to 80% by weight, in particular 20% to 67% by weight, of the fireclay cement paste, with preferably up to twice the amount by weight of fireclay particles being added to the usual cement dust. Concrete product according to one of the preceding claims 2 to 12, characterized in that the cover layer concrete ( 16 ) has a thickness of 3 mm to 20 mm, preferably 5 mm to 10 mm, and the cover layer concrete ( 16 ) by mixing the fireclay particles ( 18 ) in a cement slurry and on an already cast core layer ( 12 ) is coatable and curable, the core layer ( 12 ) provides substantially volume, shape and stability of the concrete product. Concrete product according to one of the preceding claims, characterized in that the concrete product ( 10 . 20 . 30 . 40 50 . 60 ) one Paving stone, an exterior façade stone, a brick or a roof tile. Cement mixture for producing a concrete product according to any one of the preceding claims, characterized in that the cement mixture fireclay ( 18 ) for producing the cement paste.

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