MDF cement compositions with improved impact strength
AssigneeItalcementi S.p.A.
InventorsRosa Di Maggio, Marcello Franchini, Gianluca Guerrini, Claudio Migliaresi, Stefano Poli
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Abstract
The invention concerns a MDF cement material showing better impact strength meant as an increase in the breaking total energy, by fibers addition.
Claims24
In a macro defect free cement composition comprising a hydraulic cement, water, an organic polymer soluble or dispersable in water, and at least one 3D randomly dispersed alkali resistant discontinuous fiber, wherein 3D randomly dispersed refers to fibers uniformly dispersed inside the cement matrix, an alkali resistant fiber is a fiber which when exposed to an alkaline environment (pH 12.8) at 80.degree. C. for 3000 hours in a cement slurry maintain at least 80% of mechanical characteristics with respect to not exposed fibers, wherein said macro defect free cement composition is homogenized by means of high shear stress mixing, the improvement of which comprises using fibers which after homogenization by high shear stress mixing maintain an aspect ratio L/Ed ranging from 50 and 700, wherein L stands for fiber length and Ed stands for equivalent diameter, said equivalent diameter being selected from the group consisting of fiber diameter, when the fiber has a circular section, and the quantity ##EQU2## wherein A is the area of the fiber cross section, when the fiber is not circular.
A process for preparing a macro defect free (MDF) cement composition having pseudo-ductile characteristics, wherein pseudo-ductile means showing an improved post fracture impact strength when stressed by a flexure load, said composition comprising a hydraulic cement, water, an organic polymer soluble or dispersable in water and at least one 3D randomly dispersed alkali resistant discontinuous fiber, wherein 3D randomly dispersed refers to fibers uniformly dispersed inside the cement matrix, an alkali resistant fiber is a fiber which when exposed to an alkaline environment (pH 12.8) at 80.degree. C. for 3000 hours in a cement slurry maintain at least 80% of mechanical characteristics with respect to not exposed fibers, wherein said fiber is a fiber able to maintain an aspect ratio L/Ed ranging from 50 to 700 after homogenization by high shear mixing wherein L stands for fiber length and Ed stands for equivalent diameter, said equivalent diameter being selected from the group consisting of fiber diameter, when the fiber has a circular section, and the quantity ##EQU3## wherein A is the area of the fiber cross section, when the fiber is not circular, said process comprising first homogenizing by high shear stress mixing the composition, and later subjecting the resulting mixture to a hardening phase, after optional insertion of at least one polymeric net between two layers of fiber-reinforced material.
In a macro defect free cement composition comprising an hydraulic cement, water, an organic polymer soluble or dispersable in water, and at least one 3D randomly dispersed discontinuous fiber selected from the group consisting of polyethylene, polypropylene and polyvinylalcohol fibers, wherein 3D randomly dispersed refers to fibers uniformly dispersed inside the cement matrix, wherein said macro defect free cement composition is homogenized by means of high shear stress mixing, the improvement of which comprises using fibers which after homogenization by high shearing stress mixing maintain an aspect ratio L/Ed ranging from 50 and 700, wherein L stands for fiber length and Ed stands for equivalent diameter, said equivalent diameter being selected from the group consisting of fiber diameter, when the fiber has a circular section, and the quantity ##EQU4## wherein A is the area of the fiber cross section, when the fiber is not circular.
A process for preparing a macro defect free composition which comprises a hydraulic cement, water, an organic polymer soluble or dispersible in water, and at least one 3D randomly dispersed alkali resistant fiber which maintains an aspect ratio L/Ed ranging from 50 to 700 after homogenization by means of high shear stress mixing, wherein 3D randomly dispersed refers to fibers uniformly dispersed inside the cement matrix, an alkali resistant fiber is a fiber which when exposed to an alkaline environment (pH 12.8) at 80.degree. C. for 3000 hours in a cement slurry maintain at least 80% of mechanical characteristics with respect to not exposed fibers, wherein L stands for fiber length and Ed stands for equivalent diameter, said equivalent diameter being selected from the group consisting of fiber diameter, when the fiber has a circular section, and the quantity ##EQU5## wherein A is the area of the fiber cross section, when the fiber is not circular, said process comprising homogenizing by high shear mixing the mixture of ingredients of the composition.
Dependencies are inferred from the claim text.