Mortar refers to construction engineering material prepared proportionally by cementitious material, granular fine aggregate, mineral admixture, water, and various additives as required.
Commercial mortar refers to a granular or powdery mixture produced by a specialized manufacturer that has been dried and sieved with fine aggregate and cementitious materials, mineral admixtures, and various mortar additives in a particular proportion. It can be pre-mixed with water in the factory and then transported to the construction site by a specific tank truck for use, or it can be transported to the construction site in the form of packaging after dry–mixed in the factory and then used after unpacking and mixing with water. As a new type of building material, commercial mortar has the advantages of high performance, stable quality, convenient construction, and no environmental impact. It is another new trend after commercial concrete’s rapid and steady development. The emergence of commercial mortar is a breakthrough from concept to technology for traditional building materials, and it is a brand-new solution to the technical bottleneck of the construction industry.
Commercial mortar can be divided into ready-mixed mortar and dry-mixed mortar according to its supply form (whether it has been mixed with water) when it leaves the factory. Ready-mixed mortar, or wet-mixed mortar, refers to the composition of cementitious materials, fine aggregates, polymer-modified materials, water-retaining thickening materials, mineral admixture materials, chemical admixtures, fiber materials, and pigments. It is mixed in a professional factory with water to form a final product with specific construction properties according to a particular mix ratio. It is transported to the construction site by a particular mixer truck, stored in a sealed container, and used within the specified time. A type of mortar mixture, dry-mixed mortar, refers to inorganic cementitious materials, fine aggregates, and polymer-modified materials produced by professional manufacturers after drying and screening. All kinds of materials, such as water-retaining thickening materials, mineral and chemical admixtures, fiber materials, pigments, and other components, are mixed according to a certain proportion of a granular or powdery mixture, which can be used in bulk form by unique. It is a type of mortar mixture that is transported to the construction site by tank truck and then mixed with water, or it can be transported to the construction site in the form of bags, or barrels and combined with water.
Commodity mortar can be divided into several categories according to its use, such as masonry mortar, plastering mortar, and bonding mortar. It can be subdivided into ready-mixed mortar and dry-mixed mortar for masonry, plastering, and bonding.
Commodity mortar can be divided into general commodity mortar and special commodity mortar according to use. Ordinary mortar refers to standard masonry mortar, ordinary plastering mortar, and ordinary bonding mortar commonly used in construction sites. Special commodity mortar is produced and supplied in the form of dry-mixed mortar due to its particular use, small amount, poor storage stability, and short construction time; In contrast, ordinary mortar is used in large amounts, and its storage stability within a specified time is better so that it can be supplied in the form of dry—mixed mortar which is very suitable for ready-mixed mortar. Commodity mortar can be divided into ground mortar, thermal insulation and energy-saving mortar, decorative mortar, fiber anti-crack mortar, waterproof mortar, anti-corrosion mortar, anti-radiation mortar, anti-static mortar, wave-absorbing mortar, and so on according to its function.
The essential characteristics of commercial mortar
(1) Workability of commercial mortar mixture
The mortar mixture should have good workability, and the mortar with good workability can not quickly produce stratification and segregation. It can be spread into a uniform thin layer on the rough masonry surface to be well integrated with the base bonding to facilitate construction operations and ensure project quality. The workability of the mortar mixture mainly manifests in fluidity and water retention.
1. Fluidity of mortar
The fluidity of mortar, also known as consistency, refers to the property of the mortar mixture to flow under its own weight or external force. The fluidity of the mortar can be expressed by the consistency value (mm) or the sinking degree. A mortar consistency tester usually measures mortar consistency, with a considerable consistency value indicating better fluidity.
There are many factors affecting the fluidity of mortar, which are mainly related to the type and amount of external admixtures and admixtures mixed in the mortar, as well as the type and amount of cementitious materials, water consumption, particle shape, degree of fineness of fine aggregate, and grading. To high the fluidity of the mortar, the amount of cement and water should be large, the sand should be well-graded, the edges and corners should be few, and the particles should be coarse.
2. Water retention of mortar
Choosing mortar with suitable fluidity can improve construction efficiency and help ensure quality. The choice of mortar fluidity is related to construction methods and weather conditions. For porous masonry materials in dry and hot weather, the fluidity of the mortar should be more significant. In contrast, its fluidity should be smaller for dense non-absorbent materials in wet and cold weather.
The water retention of mortar refers to the ability of mortar to retain water, that is, the power of freshly mixed mortar to maintain its internal moisture without leakage.
During the mortar transportation and construction, it should separate the mortar components from each other and avoid occurring water separation and bleeding. Suppose there are poor water retention conditions, such as bleeding and slurry during transportation and use; in this case, it will inevitably bring about two consequences: First, the mortar will produce bleeding and segregation during storage, transportation, and construction. After being built on the base layer, the water is easily absorbed by the base layer, resulting in dry-mixed mortar, which is not convenient for construction, and it is not easy to lay a uniform and dense mortar thin layer; secondly, the water is absorbed by the mortar, which will affect the regular hydration of cement and coagulation hardening, so that the strength and cohesion of the mortar are reduced. The above two points will eventually lead to a decline in the quality of the masonry. An appropriate amount of plasticizer or microfoam can be added instead of increasing the cement to make the mortar have good water retention.
(2) Properties of commeercial mortar after hardening
Masonry mortar is to bond blocks into masonry and mainly plays the role of transferring load in masonry; plastering mortar is firmly bonded to the substrate and plays the role of protection, decoration, and improvement of certain functions. Whether it is masonry mortar or plastering mortar, it must withstand the long-term effects of the environment during use. The hardened mortar should have particular compressive strength, bonding strength, tensile strength, and durability.
1. Strength of mortar
Strength is the main physical and mechanical property of mortar, and masonry mortar takes compressive strength as its strength index. The higher the strength of the mortar, the greater its cohesive force. For plastering mortar, only if the mortar has sufficient cohesive force can it be guaranteed not to be empty or fall off.
2. Cohesion and deformation properties of mortar
Cohesion and deformation properties are essential properties of plastering mortar. Plastering mortar does not bear loads, but to improve its bonding strength, it is often necessary to increase the strength level of the mortar.
The cohesive force of mortar increases with the rise of its compressive strength. The cohesive force is also related to many factors, such as the base surface’s roughness, cleanliness, wetness, and construction maintenance conditions. The bonding between the mortar and the base layer is good when used on the surface and under good maintenance. In addition, the workability of the mortar should be adjusted according to the requirements of layered plastering. The middle and surface layers can be smaller; 7 cm ~ 9cm is appropriate.
When the mortar is subjected to load, temperature, and humidity changes during the hardening process, it is prone to deformation. If the deformation is too large or uneven, it will reduce the quality of masonry and plastering, resulting in subsidence or cracking. Please take the following measures to improve the crack resistance of mortar and reduce its shrinkage value: control the particle size and content of sand. Coarser sand and more sand content can reduce the dry shrinkage of mortar; Under the premise of strength and strength requirements, it should limit the number of cementitious materials as much as possible and control water consumption as well; mix the appropriate amount of fiber materials, and divide plastered in layers, and the larger wall surface into grids. Uniform dehydration can reduce the relative shrinkage value of mortar.
