(1) Workability of waterproof mortar mixture
With good workability, the mortar mixture will not quickly produce delamination and segregation; it can be spread into a uniform thin layer on the rough masonry surface and connected well with the base layer, bonding to facilitate construction operations and ensure project quality. The workability of mortar mixtures is mainly reflected 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 mortar can be expressed by the consistency value (mm) or sinking degree. Mortar consistency is usually measured using a mortar consistency meter. A mortar with a more considerable consistency value indicates better fluidity.
Many factors affect the fluidity of mortar, which are mainly related to the types and amounts of external admixtures and admixtures added to the mortar. They are also related to the type and amount of cementitious materials, water consumption, and the type, particle shape, and thickness of fine aggregates. These factors are related to grading. More cement and water are used, the sand is well-graded, and there are fewer edges and corners. The coarser the particles, the more fluid the mortar will be.
Choosing mortar with suitable fluidity can improve construction efficiency and help ensure construction quality. The choice of mortar fluidity is related to the type of masonry, construction method, and weather conditions. For porous water-absorbent masonry materials and dry and hot weather, the fluidity of the mortar should be more significant, while for dense non-water-absorbent materials and wet and cold weather, the fluidity should be smaller.
2. Water retention
A mortar’s water retention refers to its ability to retain moisture, that is, the ability of freshly mixed mortar to maintain its internal moisture without leakage and loss.
During the process of mortar transportation and construction, it is required that the components of the mortar do not separate from each other and that water separation and bleeding do not occur. If poor water retention, such as bleeding and slurry, happens during transportation and use, it will inevitably bring about two consequences: First, the mortar will bleed and segregate during storage, transportation, and construction. After it is built on the base layer, the water is quickly absorbed by the base layer, resulting in dry mortar, which is inconvenient for construction and difficult to spread into a uniform and dense thin mortar. Secondly, the water is absorbed by the mortar, which will affect the regular hydration and hydration of the cement. Condensation hardens, thereby reducing the strength and adhesion of the mortar. The above two points will eventually lead to a decline in masonry quality. To ensure that the mortar has good water retention, an appropriate amount of plasticizer or micro-foaming agent can be added, but increasing the amount of cement is not advisable.
The water retention of mortar is expressed as delamination degree (mm) and measured using a mortar delamination degree tester. After calculating the consistency of the evenly stirred mortar, put it into a layered cylinder with an inner diameter of 150mm and a height of 300mm. Then, let the mortar rest for 30 minutes, remove the mortar from the upper 2/3 of the cylinder, and measure the remaining 1/3. The consistency of the mortar, the difference in consistency measured before and after, is the layering degree of the mortar.
Generally, the delamination value is 10 to 30 mm. Within this range, it can be used for masonry or plastering. If the delamination is too extensive, the mortar is prone to delamination and segregation, which is inconvenient for construction and cement hardening. The delamination degree For example, mortar larger than 30mm has poor water retention due to segregation; mortar with too little or close to zero stratification has strong water retention and no segregation, but this kind of mortar often uses too much cementitious material or If the fine aggregate is too fine, the dry shrinkage value of the mortar after hardening will be significant, and dry shrinkage cracks will quickly occur. It is especially unsuitable for plastering mortar, so the layering degree of the mortar should be at least 10mm.
(2) Properties of waterproof mortar after hardening
Masonry mortar bonds the blocks into masonry and play a significant role in transmitting loads in the masonry; plastering mortar is firmly bonded to the matrix and plays the role of protection, decoration, and improvement of certain functions. During use, whether it is masonry mortar or plastering mortar, it must withstand the long-term effects of the environment. The hardened mortar should have specific compressive strength, bonding strength, tensile strength, and durability.
1. Strength of mortar
Strength is the main physical and mechanical property of mortar. The compressive strength of masonry mortar is used as the strength index; standard specimens (cubes with a side length of 70.5mm) are used, and a set of six pieces is used. The cement mortar is cured for 28 days at a standard temperature of (20±3)℃ and a relative humidity of more than 90%; the cement-lime mixed mortar is cured for 28 days at a standard temperature of (20±3)℃ and a relative humidity of 60%~80%. The average value of its compressive strength (MPa). The higher the strength of the mortar, the greater its bonding force. For plastering mortar, only if the mortar has sufficient bonding force can it be ensured that it will not hollow out or fall off.
The strength of mortar is affected by the composition of the mortar itself and the mix ratio. When the mix ratio is the same, the strength of the mortar is also adjusted according to the surface roughness, cleanliness, moisture status, and maintenance conditions of the base material. The bottom mortar’s sinking degree is 10-12cm, while the middle layer and surface layer can be smaller; 7-9cm is suitable.
It is easy to deform when the mortar is subjected to load, temperature, and humidity changes during the hardening process. If the deformation is too large or uneven, it will reduce the quality of the masonry and plastering, leading to subsidence or cracking. To improve the crack resistance of mortar and reduce its shrinkage value, the following measures can be taken: control the particle size and dosage of sand. Coarse sand and more significant amounts of sand can reduce the dry shrinkage of the mortar while satisfying the workability. Under the premise of strength requirements, the amount of cementitious materials should be limited as much as possible, and water consumption should be controlled; appropriate amounts of fiber materials should be incorporated, plastering should be done in layers, more enormous walls should be divided into sections, and the curing speed should be controlled to make the mortar Dehydration can be slow and even reduce the relative shrinkage value of mortar.
3. Anti-seepage pressure
Anti-seepage pressure is a crucial indicator of polymer cement waterproof mortar products. It indicates whether the product can have excellent waterproofing and anti-seepage effects after application and whether it can withstand the anti-seepage pressure on the front or back surface.
4. Flexural strength
Waterproof mortar products require a certain anti-seepage pressure and a certain degree of compressive and flexural strength to ensure the long-term application efficiency of waterproofing and anti-seepage projects. The 28d flexural strength is generally ≥8.0MPa.
