A METHOD FOR PRODUCTION OF CONCRETE, LIGHT BALLAST CONCRETE OR MORTAR, HAVING HEAT INSULATING PROPERTIES, AND USE THEREOF

Abstract: Method for production of concrete, air entrained aggregate concrete or mortar having heat insulating characteristics and including a hydraulic binding agent with or without reactive mineral flux materials such as puzzolants, fine aggregate particles in the form of sand, with a grain size less than 2 mm, water and air pore generating agent as well as coarse aggregate. According to the invention as fine aggregate material is used in main granulated sand with amorphous (glassy or vitreous) structure and with massive, non porous grains with a grain fraction of 0.1-2 mm, a density > 2200 kg/m<3>, a coefficient of thermal conductivity ( lambda ) < 1.7 W/mK preferably < 1.2 W/mK and a volume part of 4-13 volume %. The invention also refers to use of fine aggregate material in accordance to the above stated specification.

Description: A METHOD FOR PRODUCTION OF CONCRETE, LIGHT BALLAST CON¬ CRETE OR MORTAR, HAVING HEAT INSULATING PROPERTIES, AND USE THEREOF The present invention refers to a method for production of concrete, air entrained aggregate concrete or mortar having heat insulating characteristics and including a hydraulic binding agent with or without reactive mineral flux materi- als such as puzzolants, fine aggregate particles in the form of sand, with a grain size less than 2 mm, water and air pore generating agent as well as coarse aggregate. BACKGROUND OF THE INVENTION Conventional non reinforced or reinforced concrete has a density which normally lies in the range of 2300-2400 g/m 3 and the coefficient of thermal conductivity of which in practice is indicated to 1,7 W/m K. For dry concrete the average thermal conductivity of the material is 0,9-1,3 W/m K. The concrete is therefore a rather good heat conductor. This characteristic can primarily be attributed the heat conducting ability of the aggregate material. To reduce the normal heat conduction of the concrete to values which in practice can be of importance to technical solutions without at the same time negatively influence other characteristics, for example the compression strength, is not possible with existent techniques. It is known that several concrete type have been developed in primary purpose to be heat insulating, but the heat insu¬ lating property has been caused by the concrete being sup¬ plied a considerable air void volume, either in the aggrega- te, outside this or both. The total volume part air in the concrete gives the concrete low thermal conductivity. Area- ted concrete normally contains no aggregate, but the solid material is a binding agent, in which a large volume part pores has been created with some void forming procedure in the fresh state, for example through gas generation or fro¬ thing. The porosity for this material is generally 75-90%. Areated concrete with densities in the range 300-600 kg/m 3 and void concrete with lightweight aggregate in the density range 600-1000 kg/πv* are concrete types that have low heat conduction. For areated concrete the coefficient of thermal conductivity is 0 r 15-0,35 W/m K, and for air entrained aggregate concrete with void structure 0,35-0,37 W/m K, As a result of the high porosity of these concrete types the compression strength is low 1,5-5 N/mm 2 for areated'concrete and 3-8 N/mm 2 for air entrained aggregate concrete. To further reduce the thermal conductivity in these concrete type is scarcely of interest, neither from technical or economical point of view. To exchange the lightweight aggre- gate in void concrete for some other lightweight aggregate with lower thermal conductivity and with unaltered particle density, at the highest may reduce the coefficient of ther¬ mal conductivity with some few percent. The binding agent in the concrete is constituted by hydrau¬ lic types of binding agents such as Portland cement, calcium aluminate cement, slag cement and different types of blended cement to concrete which continuously resists temperatures up to at least 300"C- In the binding agent mineral flux material with among others reactive characteristics can be contained, so called puzzolants. Example of these are flying ashes, micro silica (even named silica, condensed silica, silicon powder), granulated, ground slags and natural puzzolants such as trass and santorin earth. Through DE-A-2307734 a building material blend is known, intended for manufacture of lightweight concrete and consis¬ ting of about 1/3 fine aggregate and 2/3 coarse aggregate. The fine aggregate is constituted by pumice sand with a grain size below 4 mm. The pumice sand is characterized by large porosity and thereby has good heat insulating charac¬ teristics. The porosity however also entails that the stren¬ gth of the grains of the pumice sand is low. DE-A1-2543110 describes a heat insulating and sound- absorbing plaster mortar or construction lightweight con¬ crete. In order to achieve the attained heat insulating pro¬ perties it is recommended to replace the earlier used nature sand and the stone dust with filter ashes with 90 volume % glassy constituents and with a grain fraction of 32-40 μm. The main purpose of the filter ashes is to save cement and to improve the viscous characteristics of the water-cement paste. The heat insulation capability is obtained primarily through involvement of slag, which by its amorphous struc- ture exhibits good heat insulating characteristics. PURPOSE AND MOST ESSENTIAL FEATURES OF THE INVENTION The object of the present invention is to achieve a con¬ crete, air entrained aggregate concrete or a mortar, which has appreciably lower thermal conductivity than conventional material of this type without at the same time alter other characteristics and then especially the compression streng- th, as well as the casting properties of the concrete and the flexibility of the mortar respectively. These tasks have been solved in that as solid fine aggregate material was used in main granulated sand with amorphous (vitreous or vitreous) structure and with massive, non porous grains, with a grain fraction of 0,1-2 mm, a density > 2200 Kg/m 3 , a coefficient of thermal conductivity ( Λ ) < 1,7 W/mK preferably < 1,2 W/mK and a volume part of 4-13 volume %. SPECIFICATION OF EMBODIMENTS Air entrained aggregate concrete according to the invention consists of cement mortar, that is a composition of cement, " water and sand, in which also an air void volume is included which lies within the range 5-15 % of the total concrete volume as well as light aggregate particles as coarse aggre¬ gate of organic and/or inorganic origin. The smaller light- weight aggregate particles that are counted among the fine aggregate and which to a larger or smaller share are in¬ cluded in the cement mortar, should preferably be chosen spherical, exceptionally light, non water absorbing and deformation stable for moderate and small hydraulic over¬ pressures. The marginal size for fine and coarse aggregate in the present concrete type has been set to 2 mm. Low water absorption of the fine aggregate is important, partly be¬ cause it should be possible to hold the water content in the concrete low, which gives less building moisture and lower weight in fresh condition, partly to avoid a too quick setting of the consistency of the concrete during the first time when the concrete is fresh. The novelty and the purpose of the present invention is to reduce the coefficient of -thermal conductivity in a con¬ siderable way for monolithic air entrained aggregate con¬ crete without changing remaining concrete properties. The principle is based on that aggregate particles of crystal- line kinds of rock are wholly or partly exchanged for par¬ ticles of vitreous, amorphous structure. Primarily this affects an exchange of sand fractions that have a grain size being smaller than 2 mm. Only to a smaller extent certain grains can have larger particle size. Remaining coarse aggregate particles which are larger than 2 mm likewise are constituted by lightweight aggregate particles. They may be industrially manufactured from for example burnt expanded clay or consist of nature materials, such as pumice stone and the like. The thermal conductivity in glassy (amorphous, vitreous) and in certain micro crystalline mineral and kinds of rock as well as material with disturbed crystalline structure is appreciably less than in crystalline materials with the same composition. An example of mineral that has amorphous structure is opal which is a stiff silicon dioxide gel, Si0 2 «nH 2 0. An example of a vitreous or amorphous kind of rock is volcanic glass, designated obsidian. Its composition is rhyolitic (sour). An other common non crystalline materi¬ al is flint which also can be characterized as micro cry¬ stalline silicon-dioxide with gel structure so called chalcedony with crypto crystalline character. Amorphous silicate mineral such as opal or flint mentioned, are not suitable to be used together with cement that contains moderate to high contents of alkalies, at chemical concrete analysis indicated as disodium and dipotassium oxide. Only very special types of portland cement in such case may come in question. The glassy materials which are possible, are of the type granulated slags, for example blast furnace slags and foundry slags. Ground, granulated (basic) blast furnace slags or foundry slags in more than hundred years have been used as binding agent for concrete manufacture. The reactiv¬ ity has increased with more or less admixture of calcium hydroxide (lime), sulphates (gypsum) or portland cement. In amorphous materials such as silicate minerals the struc¬ ture lacks remote order. However close order exists for example in the form of silicon oxide tetrahedrons with four oxygen atoms in the corners of the tetrahedron. Each oxygen atom thereby is bound to two silicon atoms. Remote order implies that crystals have been formed. Glass is an example of an amorphous structure where remote order is lacking. Blast furnace slag can be used as aggregate in concrete or be ground to be used as a binding agent. The character of the slag is altered strongly with the cooling conditions during the granulation process. A rapid cooling of the smelted slag for example such that one lets the slag flow direct down into water, makes the slag decompose to sand or gravel like form. The method is called granulation. The structure becomes frozen in a glassy state and the slag then obtains general reactive characteristics. The slag fundamentally may be characterized as a latent hydraulic binding agent with a composition that is similar to portland cement. If the slag on the other hand cools slowly for example in air the structure becomes much more crystalline and the slag loses its reactive characteristics. Ih such cases the cooling slag has to be crushed if it is going to be used as gravel or rock material. A number of procedures which have been used in connection with cooling of slag has resulted in slag material with more or less high void volu- me. In certain cases the density can be as low as approxima¬ tely 150-200 kg/m 3 . By means of a relatively new procedure so called pelletized slag has been produced. The slag there¬ by obtains to a big part amorphous structure through quick cooling. Pelletized slag obtains particle sizes which prima¬ rily are larger than 2 mm and a grain density which mostly exceeds 1500 kg/m 3 . In portland cement more or less amount alkalies occur, designated by Na 2 0 and K 2 0. Taken together these are indica¬ ted by equivalent Na 2 0-content. Equivalent disodium oxide content is the sum of Na 2 0 and 0,658«K 2 O. If alkali soluble aggregate is present in the concrete so called alkali silica acid reactions might be obtained if the alkali content is too high in the cement. The reactions may result in swelling of the concrete that can be more than 0,5 %. The cracking gradually degrades the concrete. Degrading of the structure is caused by generation and swelling of a gel consisting of sodium and potassium silicate, in other terms silicon-diox- ide becomes water soluble at high concentration of OH-ions. The limit for the content of alkalies in cement usually has been set to 0,6 % ekv. Na 2 0. If this limit is exceeded there is a great risk that silic acid reactions shall happen. A secure value sometimes is regarded to be 0,4 % ekv. Na 2 0. Alkali reactions occur in amorphous and micro crystalline silicon dioxide mineral and kinds of rock with among others presence of opal. Structure degrading swelling reactions in aggregate because of high alkali content can be obtained if the aggregate is coarse-crystalline dolomite. Granulated blast furnace slag with amorphous structure however gives no alkali silic acid swelling that degrades the concrete and reduces its durability. The granulated slag is influenced chemically by alkalies but the reactions instead gives a hydrogenation and no expansion. To use vitreous slag sand generally is unproblematic and independent of the content of alkalies of the cement, or after possible supply of alkalies from the outside at a later occasion. Activation of ground, granulated slag with alkalies is utilized for manufacture of a binding agent for concrete. For such concrete naturally no alkali silic acid reactive aggregate can be used. Alkali reactive kinds of rock can be rhyolitic, dacitic and andesitic tuff and phyllites. In the types of coarse aggre- gate particles with high porosity, which are utilized in the present invention, a possible alkali expansion entails no inconveniences. The reason why there is accommodation enough for generated gel in the void system, can be found in the air voids of the concrete as well as in the pores of the aggregate. Granulated slag can even have substantial advantages in combination with other binding agents than portland cemen . Calcium aiuminate cement that is used as binding agent in concrete for high temperatures so called refractory con¬ crete, thus can be utilized together with slag for concrete that continuously resists temperatures up to 800°C instead of aggregate that contains quartz. The reason is that quartz goes through a non negligible expansion at 573°C that can destroy the structure of the concrete if this temperature mentioned is exceeded. With pirns stone as lightweight aggre¬ gate an air entrained aggregate concrete for rather high temperatures with monolithic structure can be manufactured with particularly low thermal conductivity. Instead of granulated slag even portland clinker can be used as aggregate material in the sand fraction. The clinker has proved to have surprisingly low thermal conductivity, even lower than the glassy slag. To use crushed ground cement clinker is however in most cases no economic solution. To reduce the thermal conductivity of so called lightweight concrete which already contains a large total air void volume without further increasing the air void volume and thereby decrease the strength can only be done by exchanging the solid material for equivalent material referring to strength which have low thermal conductivity. In this case it means for concrete that crystalline material is substitu¬ ted with amorphous and foremost in such a way that the chemical composition is not appreciably changed or that at least not other concrete properties are changed in negative direction. The coefficient of thermal conductivity for usual aggregate materials that are used for concrete such as granite, gneiss and limestone lies in the range 2,5 to 3,5 W/m K. The high value applies to sour - to basic magmatic, metamorphous and sedimentary silicate rocks with crystalline structure. For lime rocks the value is even lower than 2,5 W/m K, for example 2,0-2,4 W/m K. Certain minerals that are of volcanic origin can be wholly or partly amorphous or micro crystalline such as obsidian. Kinds of rock with existence of opal and chalcedony are quite inappropriate to be used together with ordinary ortland cement as the concrete has free access to water that is outdoors. Opal is harmful in quantities of 0,25 % and chalcedony of 0,5 % calculated on the aggregate weight. Only special types of portland cement contains so low con¬ tents of alkalies that the risk for alkali silic acid reac¬ tions do not occur together with reactive aggregate. Other negative characteristics furthermore accompany such that these cement types are low heat and in general not economi- cal. Aggregate particles of a very limited number of min¬ erals and kinds of rock can be glassy without the risk of alkali reactions. Pumice and pearlite are examples of these. Natural non porous aggregate material with a coefficient of thermal conductivity smaller than approximately 1,2 W/m K and which can not cause alkali silic acid reactions in concrete with normal composition of portland cement included is very seldom occurring. Instead one is forced to change to artificial material or industrial rest products. The materi¬ als can originate from some process or be demolition materi¬ al such as crushed brick. Referring to costs aggregate material from the latter the group is most favourable. In air entrained aggregate concrete it is only the sand frac- tion that wholly or partly replaces the nature sand. In certain cases it may be appropriate not to replace the nature sand with larger part than necessary with respect to the demand of the magnitude of the coefficient of thermal conductivity for the concrete. In practice one wishes in general to minimize the number ingredients in the concrete why the fine material is selected from merely one single sort, for example granulated blast furnace slag with sui¬ table grain distribution. Granulated blast furnace slag at the granulation process as coarse-grained sand. The grain composition is normally not suitable as concrete sand with the upper grain limit for example 2-3 mm. Therefore one is forced in some way to. process further the granulated slag, to attain a certain particle distribution. One method is to compose the sands of one part granulated blast furnace slag in original form with a certain part processed slag. The processing can consist of milling or crushing to a predetermined particle distribu- tion. All granulated slag must be dried since water con¬ taining reactive slag within a relative short period of time self bonds to a hard mass. Use of burnt clay that has been crushed to aggregate for manufacture of concrete goes at least as far back as to the architecture of the romans. Tile which is a ceramics has several unique characteristics, such as good properties against chemical degrading. The most important property of the tile material and which was utilized in antiquity was the puzzolanic properties of tile powder. The thermal con¬ ductivity of tile is remarkably low, 0,6 W/m K. As aggrega¬ te in concrete, in particular fine aggregate, it is a mate¬ rial that can be equated with amorphous silicates to reduce the thermal conductivity of air entrained aggregate concrete according to the present invention. Alkali silic acid - and alkali silicate reactions arise when reactive minerals, and kinds of rock as earlier mentio¬ ned are found available together with high concentration of OH-ions. Existence of natrium and potassium ions from con¬ crete or from other source therefore is necessary. At acces¬ sible amount of water a gel is formed that gives overpressu¬ re on the locations where the gel is formed such as about reactive aggregate particles. The pressure increases and cracks appears. Available water for swelling of the gel may originate from capillary transported water from the outside as well as from water absorption that has arisen at capil¬ lary condensation when the environment has high relative air moisture. The reaction velocity is controlled by the " tempe¬ rature. Small reactive particles such as dispersed micro silica or atomized puzzolants bond sodium and potassium ions. Thereby harmful expansion is avoided since high alkali contents are found in for example cement.- The harmful overpressure in the gel can be avoided with a system of air voids. The principle can be placed on an equality with effect of system of air voids in connection with freezing of water in the concrete structure. Harmful increase of pressure is avoided with the air voids as expansion vessel. The concrete that is compri¬ sed in the present invention has a system of air voids that prevents injuries of possible alkali silic acid reactions from reactive fine aggregate particles. For the concrete the following can be valid: - The concrete shall have high air void volume, at least 8% of the concrete volume, - have relative high permeability against fluid over- pressure, - have partly water-repellent capillary walls and - shall contain a relatively small volume of fine aggregate material, sand, which constitutes the amorphous material. The volume should be less than 15% of the concrete volume. The permeability is a function of the water-cement ratio and possibly the content of micro filler such as silica par¬ ticles. Therefore it may involve a certain risk to choose low water-cement ratio and large amounts of additives of micro silica for concrete in environments with continuous and exceptionally high relative air moistures. PREFERRED EMBODIMENT The concrete types that are included in the present inven¬ tion has the fundamental composition stated below. The limits between the different partial components should not be understood as absolutely sharp but a certain overlapping can occur in practice. The partial materials are quite naturally determined by what that is found available in each individual case and compromises regarding the composition are inevitable. At proportionating it is supposed that the compacted fresh concrete has the volume 1 m 3 . Each individual component included in the concrete is indicated in volume. For prac- tical reasons the materials are added to the mixture after weight why the particle densities of the materials must be known. Binding agent 90 - 120 litre/m 3 concrete Water 150 - 200 Fine aggregate 1 50 - 150 Fine aggregate 2 50 - 150 Coarse aggregate (grain > 2mm) 100 - 400 Air voids 60 - 150 The binding agent can be of different types of portland cement such as standard hardening, rapid hardening, slow hardening, blended cement wherein ground granulated blast furnace slag (20-80% of the binding agent), aluminate cement and modified portland cement (10-30% flying ashes) can be contained. In the binding agent reactive mineral additives (puzzolants) such as micro silica, flying ashes and natural puzzolanic material also should be included. Material with merely filler effect is not comprised in the binding agent. To the fine aggregate is counted aggregate material the particle diameter of which in main is smaller than 2 mm. One part of this aggregate, here named fine aggregate 1, con¬ sists of mineralic massive particles, chiefly granulated blast furnace.slag sand and nature sand. The mutual parts between these both is determined by the demand of the coef¬ ficient of thermal conductivity for the concrete. Fine aggregate 2 is particles that have extremely low particle density. The grains may actually be characterized as geomet- rically stable air voids and with a size that clearly lies above the intrinsic air voids formed during the mixing of the concrete after addition of air pore creating agents. The particles can suitably consist of expanded polymer particles of materials such as polystyrene and with a grain diameter in the range of 0,5-8,0 mm, preferably 1-4 mm with the density 10-100 kg/m 3 , preferably 20-60 kg/m 3 . The purpose of the admixture of light particles in the sand dimension range is to obtain low concrete density and give the concrete monolithic structure and good casting properties. As far as the lightweight concrete is concerned the coarse aggregate is particles with high porosity. They can be of natural origin, pumice, as well as artificial such as ex¬ panded burnt clay or flying ashes, expanded pearlite, slate and the like. Primarily the size of the particles lies within 2 to 16 mm. The combined size distribution of the aggregate particles must be without great particle jumps and preferably follow a continuous curve in resemblance with what a Fuller curve gives. The volume of grains < 0,125 mm calculated on whole aggregate particle volume should lie between 3 to 8 %. It is not all times possible to fully comply with demands on the particle composition without a certain discontinuity must be accepted, i.e one or a couple of smaller particle jumps can occur. The air voids are created during the mixing of the concrete. In order to both stabilize and create a suitable void struc¬ ture in the system of air voids some kind of air void gene¬ rator has to be added. The size and distribution of the air voids in the hardening concrete is essential for the durabi¬ lity of the concrete, for example frost resistance. The volume air voids is larger than what is present in standard concrete. The function of the air void volume in contrast to standard concrete is to reduce the concrete density. Even if there should be a less appropriate void distribution of the air voids their aggregate volume will compensate for the void system quality reduction what concerns pore charac¬ teristics. The concrete is intended to be used for manufacture of supporting structures with particularly great demands for concrete heat insulating ability. The fresh concrete shall have such rheologic characteristics that it is possible to use common casting procedures. The consistency should lie within the ' extension measure 350-600 mm. For horizontal castings the extension measure 380-450 mm should be approp- riate and for castings of vertical elements 400-550 mm. It is known that crushed sand has large negative influence on the consistency and workability of the concrete. To retain unaltered casting properties standard concrete an extra cement quantity has to be added. Among others the price of concrete will increase. Therefore crushed aggregate is not used for concrete if one is not forced thereto. Granulated blast furnace slag can partly be equated with crushed aggregate in the sand fraction range. The grains are angular and may require extra cement quantity in a cement mortar in comparison with nature sand. However the concrete of the ' present invention gives no negative influence on the concrete consistency partly by the volume of the glassy slag sand being limited, about the volume of the cement, partly by the well sized the air void volume removing impact of angular sand particles. Below a number of examples of compositions of different concrete types are shown from which the effect of the aggre¬ gate material on the coefficient of thermal conductivity of the concrete appear. The recipes applies for a cubic metre of fresh packed concrete. The value ( λ-value) of the coef¬ ficient of thermal conductivity is indicated in columns where A refers to measured -value at 28 twenty-four hour age and after drying up to equilibrium in 105 α C. B refers to calculated Λ-value under the assumption that the concrete is fresh. C refers to calculated λ-value at moisture equilib¬ rium in 60 % relative air moisture. = coefficient of thermal conductivity W/mK 3 = grain density kg/m 3 /X = indicates J -values when only the fine aggregate (0-2mm) was replaced with slag sand EXAMPLE 1. Standard concrete, quality class C 20/25 N/mm 2 Coefficient of thermal conductivity W/m K Type of aggregate A B C EXAMPLE 2. Standard concrete, quality class C 40/50 N/mm 2 Coefficient of thermal conductivity W/m K Type of aggregate A B C EXAMPLE 3. Air entrained aggregate concrete, quality class LC 14/16 N/mm 2 (3L-concrete, d freεh = 1270 kg/m 3 , άrγ =1150 kg/m 3 ) Cement Water Air voids Sand Leca Coefficient of thermal conductivity W/m K Type of aggregate A B C Leca (2 - 10 mm) 0 ~ 46 O 52 0,49 EXAMPLE 4. Air entrained aggregate concrete, quality class LC 10/12 N/mm 2 (XL-CONCRETE, r f*resh = 1130 kg/m 3 , ' dry = 1020 kg/m J ) Coefficient of thermal conductivity W/m K Type of aggregate A B C Leca (2 - 10 mm) 0,34 0,38 0,36 EXAMPLE 5. Air entrained aggregate concrete, quality class LC 10/12 N/mm 2 y ( HI-CONCRETE, ^ freεh = 1150 kg/m 3 , dry = 1035 kg/m 3 ) Coefficient of thermal conductivity W/m K Type of aggregate A B C Leca (2 - 10 mm) 0,23 0,27 0,25 If the slag product in example 5 is substituted by ground portland concrete clinker, appropriately dis¬ tributed in the fraction range 0.125-2.0 mm, a result is obtained according to example 6. EXAMPLE 6. Air entrained aggregate concrete, quality class LC 10/12 N/mm 2 (HI-CONCRETE, <T fresh = 1150 kg/m 3 , f dry = 1035 kg/m 3 Coefficient of thermal conductivity W/m K Type of aggregate A B C Leca (2 - 10 mm) 0,19 0,24 0,21 EXAMPLE 7. Air entrained aggregate concrete, quality class LC 6/8 N/mm 2 (HI-CONCRETE, cT fresh = 980 kg/m 3 , ' άry = 860 kg/m 3 ) Coefficient of thermal conductivity W/m K Type of aggregate A B Leca (2 - 10 mm) 0,18 0,22 0,20 EXAMPLE 8. Air entrained aggregate concrete, quality class LC 6/i N/mm' (HI-CONCRETE, kg/m 3 ) Cement Water Air voids Polystyrene Clinker sand Leca litre) Coefficient of thermal conductivity W/m K Type of aggregate A B Leca (2 - 10 mm 0,16 0,20 0,18 (Clinker sand constitutes of crushed/ground portland clinker with coefficient of thermal conductivity 0,6 W/m K) EXAMPLE 9. Air entrained aggregate concrete, quality class LC 6/8 N/mm 2 ( HI-CONCRETE , ό fτesh = 900 kg/m 3 , 0 dry = 780 kg/m 3 ) Coefficient of thermal conductivity W/m K Type of aggregate A B C Leca (2 - 10 mm) 0,18 0,22 0,20 (Bulk density of the leca-materiai is 310 kg/m 3 ) EXAMPLE 10. Air entrained aggregate concrete, quality class LC 8/10 N/mm 2 ^ (HI-CONCRETE, / fresh = 970 kg/m 3 , dry = 850 kg/m 3 ) Coefficient of thermal conductivity W/m K Type of ' aggregate A B C Leca (2 - 10 mm) 0,19 0,23 0,21 (Bulk density of the leca-material is 345 kg/m 3 ) EXAMPLE 11. Air entrained aggregate concrete, quality class LC 10/12 Nmm 2 ( HI-CONCRETE, 0 freεh = 1110 kg/m 3 , i άτγ = 990 kg/m 3 ) Cement Water Air voids Polystyrene Slag sand Leca Coefficient of thermal conductivity W/m K Type of aggregate A B C Leca (2 - 10 mm) 0,22 0,26 0,24 (Bulk density with The Leca-material is 400 kg/m 3 ) Certain initial experiments were made with "clean" cement mortar. For testing of the characteristics of the cement a standard sand ( Λ = 3.3 W/mK) was used. The composition, converted into kg/m 3 is shown * in examples 12-14. The slag sand used was constituted by ground slag, to corresponding fraction. The measured ^ - value of the slag = 1.1 W/m 3 . EXAMPLE 12. Standard mortar, 1:3 (1 part cement 3 parts standard sand 0-2 mm). Cement 524 kg Water 262 1 Air voids (1 vol%) Sand 1572 kg Coefficient of thermal conductivity W/m K Type of aggregate A B C EXAMPLE 13. Standard mortar, 1:3 (1/3 of the sands exchanged for fine air (30-600μm), corresponding 3L-mortar). Cement 524 kg Water 262 1 Air voids (18 vol%) Sand 1050kg Coefficient of thermal conductivity W/m K Type of aggregate A B C EXAMPLE 14. Standard mortar, 1:3 (1/3 of the sands exchanged for fine air (30-600μm), 1/3 exchanged for expanded polys¬ tyrene (0.5-2 mm) corresponding XL-MORTAR). Coefficient of thermal conductivity W/m K Type of aggregate A B C In the examples above has stated the lightweight aggregate material Leca. Other lightweight aggregate material such as Liapor (expanded burnt clay) or pumice can as well be used. The slag is granulated blast furnace slag with the density 2710 kg/m 3 . In the examples 2-11 air voids occur in volume from 9 to 13 volume!. The air voids has has been achieved during mixing of the concrete with an air pore generating agent of combination type. The hardening concrete through the action of the additive becomes waterproof and water repel¬ lent in addition to becoming salt frost resistant.

Claims: CLAIMS Method for production of concrete, air entrained aggregate concrete or mortar having heat insulating characteristics and including a hydraulic binding agent with or without reactive mineral flux materials such as puzzolants, fine aggregate particles in the form of sand, with a grain size less than 2 mm, water and air pore generating agent as well as coarse aggregate, c h a r a c t e r i z e d t h e r e i n, that as solid fine aggregate material is used in main granu¬ lated sand with amorphous (glassy or vitreous) structure and with massive, non porous grains with a grain fraction of 0,1-2 mm, a density > 2200 Kg/m 3 , a coefficient of thermal conductivity ( / \ ) < 1,7 W/mK preferably < 1,2 W/mK and a volume part of 4-13 volume%. 2. Method according to claim 1, c h a r a c t e r i z e d t h e r e i n, that the fine aggregate material is constituted by granula- ted, ground foundry or blast furnace slag, crushed, burnt clay (tile) and/or slag cement and/or portland clinker as sand fraction. 3. Method according to claim 1, c h a r a c t e r i z e d t h e r e i n, that the cement is high alkali portland cement or that the total the amount of alkali in the concrete is larger than what corresponds to 0,6 % equivalent disodium oxide (Na 2 0) of the weight of cement. 4. Method according to claim 1, c h a r a c t e r i z e d t h e r e i n , that the coefficient of thermal conductivity of the concrete in dried up condition can be reduced with up to 40% with admixture of amorphous fine aggregate with coefficient of thermal conductivity 1.2 W/m K such as granulated slag and up to 45% when the fine aggregate as entirety consists of cement clinker. 5. Method according to claim 1, c h a r a c t e r i z e d t h e r e i n, that the fine aggregate in addition comprises expanded polymer particles of materials such as polystyrene, polyet- hylene, polyurethane and others with a grain density of 10- 50 kg/m 3 and with a grain diameter in the range 0,5-8,0 mm, preferably 1-4 mm. 6. Use of granulated sand with massive, non porous grain with a grain fraction of 0,1-2 mm, a density > 2200 Kg/m 3 , a coe ficient of thermal conductivity ( A ) < 1,2 W/mK and a volume part of 4-13 volume % as solid fine aggregate material for concrete, air entrained aggregate concrete or mortar for reduction of the thermal conductivity without at the same time negatively influence other characteristics, such as compression strength and casting properties.

Inventors: BERNTSSON LEIF, HEDBERG BENGT, BERNTSSON, LEIF, HEDBERG, BENGT
Applicants: DELCON AB CONCRETE DEV, DELCON AB CONCRETE DEVELOPMENT
Application year: 1992
Main classification: C04B18
IPC codes: C04B7, C04B14, C04B18, C04B20, C04B28, C04B38