Mortar is a strong binding material that seals the gaps between bricks and other blocks used in construction. Without it, these materials would break apart, allowing moisture to penetrate your home’s facade.
Traditional mortar consists of a blend of Portland cement, hydrated lime, and sand. A proprietary substance called “masonry cement” can replace these ingredients in some areas.
Strength
Mortar embeds masonry units and forms wall-finishing materials (plaster and render). It also binds bricks or stones together so water cannot get through them.
Many types of mortar are produced. Each type has its specific properties. Some of these include bond strength, flexibility, and compressive strength.
A high-strength mortar must have plenty of cement, good-quality aggregates, and the correct water content. Adding too much or too little water can change the consistency and weaken the mortar.
In addition, it has been found that the flexural strength of mortar increases with curing time. This is particularly true of the samples prepared per the manufacturer’s recommendations using 4 L of water per 25 kg dry mix.
Water retentivity
Water plays a vital role in mortar strength and workability. It is required for the hydration of cement and contributes to its workability, as it helps the mortar to become stiff enough to hold masonry units. At the same time, they’re being positioned and shaped.
Good workability and strength require a balance of water, sand, and cementitious materials. This is accomplished through thorough mixing, a quality grade of sand, and using mortar with good water retentivity.
Mortars are measured for their ability to retain water by a laboratory test method that measures “initial flow” and “flow after suction,” using a specialized pump. Initial flow is the percentage increase in diameter when a mortar sample is dropped 25 times in 15 seconds.
The retentivity of mortars is a key factor in choosing a suitable formulation as a function of the substrate, climatic conditions, industrial applications, etc. It also influences the strength and durability of masonry, especially for walls subjected to severe stress or weathering.
Workability
Mortar is a workable paste that hardens to bind building blocks such as stones, bricks, and concrete masonry units. It also fills irregular gaps between building blocks, spreads the weight of the blocks evenly, and sometimes adds decorative colors or patterns to masonry walls.
Typically, mortars are made of cementitious materials, aggregates, and water. Some admixtures or coloring agents may be added, as well.
The workability of mortar depends on the admixtures used to make it. For example, it is less workable when using fiber reinforcement.
It is also less workable when using sand and clay instead of marble waste in the mixture because the particles do not behave homogeneously when the mortar is fresh.
A typical mixture is 1 part Portland cement, 1 part lime, and six parts standard sand m. This mix has medium compressive strength.
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Setting speed
Mortar is an effective building material that binds bricks and stones to provide a tight joint that water cannot penetrate. This mortar is made of cement and lime with the addition of a fine aggregate such as sand or clay.
Setting speed is the time required to harden a mortar or concrete completely. This is measured using various methods, including the penetration resistance test and the calorimetry test-based method.
The setting time can be increased by adding a hydraulic lime, which sets on contact with water. Alternatively, a pozzolanic material may be added to the mortar mix, which will also help to increase its set speed.
A polymer-modified mortar is a type of mortar that is made of organic polymers as an admixture. The polymers in the mortar mix quickly rearrange to form a thin layer of protective film, which traps water inside the mixture and helps fill capillary pores formed during curing. This film is responsible for the mortar’s high strength, toughness, and tensile properties.
