The industrial production of lime generates greenhouse gases, which contributes to increase the global warming. Therefore, the present study evaluated the feasibility of replacing lime by ornamental rock waste (ORW) as a by-product of the related stone industry, and developed a cost-effective mortars. These new low-costing mortars are intended as fresh fluid paste coatings to be applied on walls by the mechanized projection technique. The ornamental rock waste was collected from a marble and granite industry as ground stone. It was finely crushed before mixing with cement, sand, water and superplasticizer in amounts of 1.0% (R01), 1.2% (R02) and 1.3% (R03), to prepare the mortars, which had the mixture, cement: ORW: sand, 1:1:4 in wt.%. These novel mortars were characterized in both fresh, for well projection, and hardened state, to evaluate the properties after curing performance. The results showed that mortar R03, achieved the best results and did not present cracks in the hardened state. Its water retention was found above 30%. Both tensile strength of 0.312 MPa and compressive strength 7.88 MPa, which are above the corresponding minimum required by the standard for external coating. Water absorption by immersion of 19.37% and void content of 20.23% were close to the corresponding values for hydrated lime mortar. Dry shrinkage showed that the new R03 mortar reached more than 90% of their total retraction at 7 days of cure without sign of cracking. These findings revealed the R03/ornamental rock waste -based mortar applied by mechanized projection as a promising sustainable substitute for common lime-based mortar.

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Resumo Os resíduos produzidos em diferentes atividades agroindustriais acarretam um elevado custo às empresas, seja em relação ao transporte ou em relação ao descarte. Uma forma de reaproveitamento, que beneficia não somente economicamente, mas também ao meio ambiente, é a incorporação desses resíduos nas argamassas. Esse processo torna-se vantajoso e viável, uma vez que alguns desses materiais possui alto teor de sílica (SiO 2) em sua composição. Nesta pesquisa fez-se a comparação entre o uso em argamassas de dois desses resíduos em substituição ao cimento em diferentes proporções: a cinza da casca do arroz e a cinza do bagaço da cana de açúcar. Aanálise dos resultados mostrou que as cinzas podem ser incorporadas às argamassas com significativo aumento na densidade de massa e na resistência mecânica à compressão. Palavras-chave:argamassa, cinza da casca do arroz, cinza do bagaço da cana de açúcar. INFLUENCE OF INCORPORATION OF RESIDUES IN MORTARS Abstract The residues produced in different agroindustry activities carry excessive cost to the companies, either in relation to the transport or in relation to the discard. One form of reuse, which benefits not only economically but also environmentally, is the incorporation of these residues into mortars. This process becomes advantageous and feasible, since some of these materials have high silica (SiO2) content in their composition. In this research the comparison was made between the use of mortar of two of these residues in substitution of the cement in different proportions: the rice husk ash and the sugarcane bagasse ash. Analysis of the results showed that ashes can be incorporated into mortars with significant increase in mass density and mechanical resistance to compression.