Dry construction composition wet-sprayable by means of a screw pump and containing a binder and a biosourced filler, and preparation and uses of such a composition

A dry mortar composition, wet-sprayable by means of a screw pump, enabling the production of an insulating mortar, the dry mortar composition comprising:

• —A— at least one binder, itself comprising:
• —A1— at least one primary binder comprising lime and at least one alumina source, wherein a dry weight ratio of the alumina source to the lime is less than or equal to 1.5;
• —A2— at least one water-retaining agent;
• —B— at least one biosourced filler of plant origin;
• the B/A ratio—the volume of dry filler —B— in litres/mass of dry binder —A— in kg—being comprised between 4 and 7.9 L/kg;
• wherein
• the dry mortar composition is configured such that when it is mixed with water at a water/A weight ratio comprised between 0.8 and 5, it forms a wet-sprayable composition that is pumpable in a screw pump, the wet-sprayable composition having a setting time of between 1 and 24 hours that is effective to produce an insulating mortar that has a thermal conductivity λ of less than or equal to 0.1 W/m·K;
• the biosourced filler —B— of plant origin, is essentially composed of cellulose, hemicellulose and/or lignin, said filler comprising
• at least one component, fibres, fibrils, dust, powder, chips
• said component originating
• from at least part of at least one plant raw material,
• in at least one particulate form,
• the at least one plant raw material is hemp;
• and
• the binder —A— comprises—in dry weight/weight %—:
• the at least one primary binder—A1—:
• 5-95;
• of which:
• the lime:
• 10-95;
• the at least one alumina source:
• 1-90;
• the at least one water-retaining agent—A2—:
• 0.1-5;
• —A3— surfactant:
• 0.01-1;
• —A4— secondary binder 0-85;
• —A5— lubricating mineral filler with a particle size d90 less than 100 μm:
• 0-40;
• —A6— mineral spacing filler with a particle size d90 greater than or equal to 100 μm:
• 0-40;
• —A7— water-repellent additive:
• 0-1.5;
• —A8— retarding additive:
• 0-3;
• —A9— accelerating additive:
• 0-3;
• and
• —A10— thickening additive:
• 0-2.