This paper investigates the properties of cement mortar containing recycled concrete powder (RCP) as sand replacement. Two types of model RCP prepared with designated water-to-cement (W/C) ratios in the laboratory, including recycled cement paste powder (RCPP) and recycled cement mortar powder (RCMP), were utilised in the mortar. The physical, mechanical and drying shrinkage properties of the mortars with various amounts of RCP were investigated, and their microstructure was characterised. The results indicate that increasing the RCP content increases the water demand and decreases the dry bulk density of mortars due to the inferior characteristics of RCP. Replacing sand by up to 10% RCPP prepared with various original W/C ratios or 20% RCMP has a negligible or slightly positive impact on the mechanical properties of mortars. This is mainly attributed to the decreased volume fraction of large capillary pores, air voids and total porosity, which overcomes the negative effects induced by RCP. Specifically, incorporating RCP can reduce the fraction of large voids through its filling effect and slightly promote hydration in mortars. Besides, the drying shrinkage of the mortars increases with the RCP replacement ratio due to the increased volume fraction of mesopores in the RCP mortars. However, an excessive amount of RCP increases the volume fraction of capillary pores and the total porosity of mortars due to the combined action of the decreased packing density and the high porousness of RCP particles, which subsequently decreases the mechanical properties and further increases the drying shrinkage of RCP mortars. In general, incorporating a proper amount of RCP as sand replacement can enhance the sustainability of mortars without compromising their mechanical properties.

本文研究了含有再生混凝土粉末 (RCP) 的水泥砂浆作为砂替代物的性能。砂浆中使用了在实验室中以指定的水灰比 (W/C) 制备的两种模型 RCP，包括再生水泥浆粉 (RCPP) 和再生水泥砂浆粉 (RCMP)。物理、机械和干燥收缩研究了具有不同 RCP 量的砂浆的性能，并对其微观结构进行了表征。结果表明，由于RCP的劣质特性，增加RCP含量会增加需水量并降低砂浆的干容重。用不同原始 W/C 比或 20% RCMP 制备的高达 10% RCPP 替代沙子对砂浆的机械性能的影响可以忽略不计或略有积极影响。这主要是由于大毛细孔、气孔和总孔隙度的体积分数降低，克服了RCP引起的负面影响。具体来说，加入 RCP 可以通过其填充效果减少大空隙的比例，并略微促进砂浆中的水合作用。除了，由于RCP砂浆中介孔体积分数的增加，砂浆的干缩随着RCP置换率的增加而增加。然而，过量的 RCP 会增加毛细孔的体积分数和砂浆的总孔隙率，这是由于填料密度降低和高孔隙率的共同作用。RCP 颗粒，随后会降低机械性能并进一步增加 RCP 砂浆的干燥收缩。一般来说，加入适量的 RCP 作为砂替代物可以提高砂浆的可持续性，而不会影响其力学性能。