**3. Designing repair mortars**

Usually, a detailed analysis of the authentic building materials is performed to establish an opinion about the materials and techniques used during the construction phase [2]. Based on the results of this analysis, the design and laboratory production of some materials follows [14, 37]. The destructive consequences from the use of

#### *The Role of Sand in Mortar's Properties DOI: http://dx.doi.org/10.5772/intechopen.102489*

incompatible repair materials are related to different physical, chemical, and elastic characteristics that many new materials possess in relation to the old lime-based ones. For this reason, the quality of the materials used in intervention works is of primary importance for the longevity and economy of interventions. However, standard test methods and recommendations have not yet been developed despite the effort at the European level.

As river sand remains as one of the most widely used fine aggregates due to its desirable properties an increased tendency to use and it is observed. With an increase in construction activities, the demand for river sand has also been increasing. As a result, it has been mined at a high rate, depleting its natural resources and causing serious environmental issues. Also, owing to the excess cost of transportation, the natural river sand has become expensive. Hence, industries are shifting to other materials, such as crushed sand. But as the demand for building materials will continue to increase, their sources for crushed sand might also get exhausted. Therefore, there is a need to replace the fine aggregate either completely or partially with an alternative material that can satisfy the properties required for concrete, which is cost-effective and at the same time sustainable. Finding an alternative material to river sand has now become imperative.

The incentive to use sand from building demolition in repairing mortars derives from different needs. Natural sand originating from rivers is becoming rare, while the extraction of aggregates from quarries carries an increased administrative cost due to new strict legislations.

Both practices are not considered environmental friendly and, thus, the criteria and legislation for sand extraction are becoming stricter and demanding, while in some places, good quality natural sands are not available. On the other hand, the increased waste production offers the availability of large volumes of recycled materials and public concern about the environment pushes toward their utilization. The possibility of incorporating fine recycled sand originating from construction and demolition waste in lime-based traditional mortars. The study showed that the recycled sand had an even grain distribution, without any hazardous material and low content of soluble salts [38]. The mortars mixtures with recycled sand showed increased water demand and reduced workability compared to mortars with natural sands, even when superplasticizer was used [39]. The mechanical strength measured at 28 and 90 days showed good results as the mortars with lime and recycled sand had higher compressive strength compared to mortars with natural sands [40].

Additionally, several industrial wastes, (fly ash, demolition waste, slag, glass, brick waste, and plastic), have been shown to be suitable as construction materials and readily follow the design requirements. The substitution of the siliceous aggregate with plastic sand leads to a decrease in mechanical properties, opportunities in the use of these materials are not affected, especially for applications that do not require a structural function [41].

### **4. Conclusions**

The mechanical and physical properties of a mortar both at fresh state, but also long-term, depend on multiple factors, including binder type, curing time, binder aggregate and binder—water ratios, nature, shape, and grading of aggregates, the compaction degree, and also the environment in which they function. As mortars are composite materials, each component has a special role in the ultimate quality of the material. Aggregates, being of great volume in the mortar mass, significantly

influence the structure and the properties achieved in all states of mortar production. The analyses of old mortars revealed the continued presence of sand in the mortars from pre-history up to the cement era. Coarser grains were also used in the technology of mortars. Generally, it is accepted that the strongest mortar mixes are produced from well-graded, clean, and angular aggregates. Usually, they were of local origin following principles of ecology and economy.

The same principles should be applied today having the technological evolution as an alley to protect the environment and work on the benefit of the constructions. Understanding the mechanisms of action and the parameters affecting significant properties in mortars, a well-engineered mixture can be achieved utilizing alternative solutions to protect natural resources and at the same time bring to the market highquality innovative mortars. Recycled sands are promising materials in construction as after specific tests, they can be utilized either in repairing old structures or even in preparing new cement-based mortars.
