How to determine whether the quality of thermal insulation mortar is good or not
Release Time:
2015-08-18
Source:
How to determine whether the quality of thermal insulation mortar is good or not
Thermal insulation mortar It is a thermal-insulation masonry mortar formulated with cement, as-received fly ash, and ordinary sand. Thanks to its well-graded aggregate composition, the mortar achieves higher density and excellent thermal insulation performance, while its cost is lower than that of cement mortars of the corresponding grade. Polystyrene-bead thermal-insulation mortar is composed of composite cementitious materials and aggregates with specific particle sizes and gradation. It is composed of expanded polystyrene particles and other components, with the volume fraction of expanded polystyrene particles accounting for no less than 80% of the dry-mixed mortar. During the molding and production of thermal insulation mortar, the quality of test specimens is significantly influenced by human factors; in particular, when producing adhesive-powder-based expanded polystyrene particle thermal insulation mortar, two main issues require attention.
When preparing thermal insulation mortar, the powder, expanded polystyrene beads, and water are mixed in a specified proportion and thoroughly blended. To facilitate on-site application, some manufacturers pre-mix the powder with the expanded polystyrene beads before shipment. However, due to differences in density and particle size, these two components tend to separate during handling, resulting in the powder… The material tends to settle at the bottom of the bag. If the powder content is too high, the measured thermal conductivity and compressive strength will be overestimated; conversely, if the polystyrene beads are in excess, the thermal conductivity and compressive strength will be underestimated. In such cases, the first step is to thoroughly mix the polystyrene beads with the powder, then add water and stir vigorously until the polystyrene Ensure thorough mixing of the granules, powder, and water. If, upon commissioning a test, the polystyrene granules and powder are supplied separately, first thoroughly mix the powder with water according to the specified mix ratio, then add the polystyrene granules and mix until uniformly blended.
When fabricating 300 mm × 300 mm × 300 mm test specimens, three modular bottomless metal molds are used; it is preferable to line the horizontal surface with a polyethylene film as the bottom frame rather than using glass. If the bottomless metal molds are placed directly on glass, even after applying a generous amount of release agent to the glass, demolding remains difficult, and the specimen surface will adhere to the glass. Many release agents increase the grinding workload; if the grinding is uneven, it will introduce errors into subsequent thermal conductivity measurements. In contrast, polyethylene film is much more convenient to use—only a small amount of release agent needs to be applied with a brush to achieve easy demolding. During specimen preparation, special attention must also be paid to preventing voids from forming in the slurry; a putty knife should be used to ensure the standard slurry Fill the mold layer by layer, slightly overfilling to ensure full compaction. For 100 mm × 100 mm × 100 mm test cubes, use a tamping rod to uniformly tamp 25 times, working from the outside toward the center, and then use a putty knife to score the mold walls several times before smoothing the surface. Because test cubes demolded after 7 days of curing at laboratory temperature exhibit relatively low strength and stiffness, care must be taken during demolding. Pen. Removing the formwork too quickly or applying excessive force can easily damage the test specimens; moreover, freshly removed specimens must be placed on a level surface, as failure to do so may result in gradual deformation during curing, potentially leading to specimen damage.
Testing of polystyrene-bead-insulated mortar and vitrified microsphere-insulated mortar: Polystyrene-bead-insulated mortar consists of polymer powder and expanded polystyrene beads, while vitrified microsphere-insulated mortar is a single-component dry-mix mortar formed by uniformly blending vitrified microspheres as the aggregate with a modified dry-powder binder. During application, water is added and the mixture is thoroughly stirred before being troweled or sprayed. On the base-layer wall surface, both the thermal insulation performance and the mechanical properties are closely related to the dry density. The specimen dimensions for dry-density testing are as follows: for the polymer-bonded polystyrene-bead insulation slurry, 300 mm × 300 mm × 30 mm; for the vitrified microsphere insulation slurry, 70.7 mm × 70.7 mm × 70.7 mm; and for the compressive strength tests, all specimens measure 100 mm × 100 mm × 100 mm. Prepared To prepare standard test specimens of thermal insulation mortar, the mixture shall be prepared by mixing and stirring according to the proportions specified in the product manual or the water-to-material ratio recommended by the manufacturer. The mixture shall be thoroughly stirred in accordance with the mixing procedures prescribed in the relevant standards. It is permissible to use a putty knife to tamp the mixture several times, after which any excess material on the top surface of the test mold shall be trimmed and smoothed. After the specimens are formed, Cover with polyethylene film and cure as specified.
The above tests essentially reveal the performance and quality of the thermal insulation mortar; however, given the varying test conditions, specific comparative evaluations must be conducted based on actual site conditions.
