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Raw clay is used in construction as a binder in mortars, in straw and shive-based composites, or in the production of unfired bricks. The problem with its use is its high susceptibility to drying shrinkage, low water resistance and low mechanical strength, which limits its use. The aim of the research was to assess the possibility of improving selected physical and mechanical properties of clay-sand mixtures by using methylcellulose (MC) in the amount of 0.2%, 0.4%, 0.6% of the clay mass. The glauconite clay used in the research is an industrial waste from the extraction of sand for the production of building materials. Selected properties of the fresh mixture and the parameters of the hardened material were examined, such as flexural and compressive strength, water resistance, shrinkage, drying kinetics, density and pore distribution. Additionally, SEM observation is described. The addition of methylcellulose thickened the mixture, retaining some of the mixing water. MC had a positive effect on reducing shrinkage by a maximum of 20.2%, reduced the weight loss after exposure to water by a maximum of 93.6%, and improved the flexural and compressive strength by a maximum of 22.8 and 34.9%, respectively, compared to the mortar without the admixture. The best results were obtained with an admixture of 0.4%, and increasing the content resulted in deterioration of the parameters. The beneficial effect of using MC can extend the use of glauconite clay in the unfired state, leaving the green in color. The results obtained prove that the developed mixtures can be the basis for making unfired bricks with load-bearing properties, mortars and plasters, including external ones. However, further research is necessary, such as moisture sorption and vapor permeability, which are important when using clay-sand mixtures as an external wall layer. © 2024 Elsevier Ltd
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