PROCESS AND PLANT FOR THE PRODUCTION OF TOUGH CEMENT-CONCRETE

Abstract: The invention consists of a mixing process where the known technique of forced mixing of the materials, in order to obtain homogeneity and penetration, is exchanged for a technique of mixing by the flow implying the use of the peculiarities of the materials, developed during the mixing process and that the peculiarity of the coarse fraction to develop a continuous flow in the mixer is utilized for spreading the other materials in even layers over the surface of the coarse fraction, were the water phase as a first layer on the coarse fractions surface, has the peculiarity to bind, to the surface of the flowing coarse fraction, an even layer of cement and filler and to penetrate the layer and thereafter spread layer of the fine fraction in one step and develop a continuous phase through the skeleton of aggregate particles and thereby disperse both large and small particles in a combined volume of suspension whereupon the peculiarities of dispersed particles develop the toughness in the glue phase of the cement concrete.

Description: PROCESS AND PLANT FOR THE PRODUCTION TO TOUGH CEMENT-CONCRETE The invention concerns a mixing process for production of cement concrete where the g lue phase is made tough from dispersed filler and fine fraction particl es and that incl udes at least 1 ) aggregate material divi ded in a coarse and a fine fraction, 2) cement phase and 3) a water phase. Characteristic of the invention is that the effect is obtained through the pecul iarities of the coarse fraction, the water phase , the cement and the fine fraction devel oped during the mixing process. These peculiari ties are: O The coarse fracti on has the peculiarity of maintaining the material in the mixer at a continuous flow. The flow is used to spread the other terials in even layers over the surface area of the coarse fraction. 2) . __ water phase, when mixing with the coarse fraction, has the peculiarity of, through the penetration, binding an even layer of cement and f iller to the surface of the, in the mixer, fl owing coarse fraction and, furthermore an even layer of fi ne f raction materi al, and to devel op a continuous phase through the skeleton of the aggregate particles and thereby disperse all, both l arge and small aggregate particles in a combined volume of suspension. 3) The filler and the fi ne fraction particles have the peculiarities, in dispersed state, of developing toughness both in the water phase of the fresh concrete and in the glue phase of the hardened cement concrete. In the conventional production of cement concrete, the material is fil led into the mixer wi th no consideration to the peculiarities of the i ndividual materials or the rel ation between the thickness of the l ayer of the different materials and the penetration of the water phase. Penetration of the water through the cement, the filler, the coarse and the fine fraction, is obtained through the principle of forced mixing. A suspension can either be unstable or stable. The term unstable here indicates that a suspension develops during the mixing process, or through vibration, but returns to sedimentary state when the mi x i s at rest. The suspension of the mix of the invention is stable, which implies that the casted cement concrete maintains a state of suspensi on until hardened, a condi tion at which the glue phase develops toughness from dispersed particles. The homogenit in material distri bution and penetrati on of the water through the material is obtained by the principle of mixing by flow. The cement concrete of the i nvention differs from the conventional cement concrete in that the property of elongation is linear with the strength, thus reducing or eliminating the tendency of the concrete to crack. The property of elongati on of conventional concrete is a reversed function of strength, thus providing the concrete with the tendency to crack at load or at changes in the temperature of the concrete. The tendency of the concrete to crack is revealed in studies of the elongation in the primary-and secondary zone of the load-to-break test. The primary elongation develops within the limi ts of the el asti city of the material and the deformation in the material gl ue phase is reversible, whereas the elongation in the secondary zone of conventional cement concrete lead to crack in the material. The cement concrete of the invention el ongate through the secondary zone wi thout formi ng of cracks. For materials that crack at elongation in the secondary zone of deformation, the glue phase is hard and brittle, two properties that provide the material with the tendency to crack at changes in temperature and at ageing. Materials that elongate in the secondary zone without forming crack have a tough glue phase. The toughness is a natural protection against forming of cracks. The development of a tough glue phase requires that the glue phase is both ductile and cohesive. See appendix, figures 1 a) and b) . The reason for the invention is that at the use of the patent nr EP 0126105 (International publication nr = WO 84/0191 8), the fine fraction particles become incapsulated in the first developed suspension of the cement and if used, fill er particles. The present invention secures a further step in the development of cement concrete by the development of a combi ned suspension of cement filler and fine fraction i n one step thus resulting in the glue phase becoming tough by the influence of dispersed particles. Characteristic for the cement concrete plant of the invation to operate in accordance with the principle of mixing by the flow, is as follows: 1 ) The free choice of time intervals between opening and closing of the i nlets; gates, conveyer belts, screws and other means, for discharge of the cement, the fi ller and the fine fraction and 2) free choice of flow rates when discharging cement, filler and fine fraction material . The functioning of the mentioned devices are the means of the invention used to optimize the distribution of the cement, the filler and the fine fraction materials in even layers on the flowing surface area of the coarse fraction. The invention is depending on that the inlets are desi gned and positioned so that the streams of cement, filler and fine fraction joins the continuous flow of the coarse fraction in the mixer, in the same manner as one stream of water joins another stream. The devices on conventional cement concrete plants are made for quick discharge of the cement and the filler into the mixer and without the even distribution obtained at di scharge in accordance wi th the invention. The di stri buti on and penetration are obtai ned through forced mixing of the materials, resulting i n insufficient homogenity and penetration to hold the aggregate particles in a closed volume of liquid. Instead the liquid is divi ded on the surface of the aggregate particl es, clustering the particles together. The glue becomes hard and bri ttle, which explains the tendency of the conventional concrete to crack from influence of cl imate and at low age. When fill er is included, this is discharged into the mixer with the cement. Flui dizer, when used, i s added to the mixer before the fine fraction. The mixing procedure of the invention can be utilized with modified cement and other chemical addetives.

Claims: Claim 1 ~ + Process for production of cement concrete with tough glue phase obtained from dispersed particles, consisting of at least aggregate material devided in a coarse and a fine fraction, cement phase and a water phase is c hara¬ c te ri ze d by that on the flowing coarse fractions surface in the mixer, first distribute the water phase and after optimized interval of time and with optimized flow rate spray the cement together if used, the filler, for binding this material in an even layer to the surface of the coarse fraction by penetration of the water phase whereopon, after an optimized interval of time and at optimized rate of flow, the fine fraction material is spread in a layer over the filler covered surface of the coarse fraction, in the mentioned order, and that the discharge of the fine fraction particles starts before the water phase breaks through the layer of cement particles and filler if used. Claim 2 Process in accordance with claim 1 is c h ara c t e ri ze d by that the distribution in even layers of cement and fine fraction on the surface of the coarse fraction are optimized by the choice of interval by time and the time for spreading the materials when discharged. Claim 3 Process in accordance with claim s c h a rac t eri z e d by that if filler is included in the mix this material is spread in the mixer together with the cement phase. Claim 4 Process in accordance with claim 1 is ch ara c t eri z e d by that the glue phase consisting of water, cement and fine fraction develops into a suspension in one step through discharge of cement and fine fraction in two steps. Claim 5 Process in accordance with claim 1 is c h a r a c t e r i z e d by that liquidizer if used, is added to the mixer before the discharge of the fine fraction. Claim 6 Plant to be used with application of process in accordance with claim 1 and 2 is charac te ri z ed by that inlets; gates, conveyer belts, screws or other means for feeding of cement, filler and fine fraction to the mixer have adjustable flow rates to be used when optimizing the distribution in even layers of the materials over the surface of the coarse fraction. Claim 7 5 Plant to be used with application of the process in accordance with claim 1 and 2 is cha ract eri zed by that inlets; gates, conveyer belts, screws or other means for feeding of cement, filler and fine fraction have adjustable intervals of time for disaharge of the individual materials, used when optimizing the distribution of the materials in even layers over the surface of the coarse fractions. Claim 8 Plant to be used with application of the process in accordance with claim 1 for discharge of cement, filler and fine fraction to the mixer is charac t e r i z e d by that the stream of cement, filler and fine fraction is connected with the continuous flowing coarse fraction in the mixer.

Inventors: OHLSON KARL GUNNAR, OHLSON KARL, GUNNAR
Applicants: OHLSON KARL GUNNAR, OHLSON KARL, GUNNAR
Application year: 1995
Main classification: B28C5
IPC codes: B28C5, C04B40