# Durability of Mortars with Partial Cement Replacement by Recycled Brick Powder
## 1 Introduction
Despite these examples, relatively few studies have investigated the durability-related characteristics of concretes in which OPC has been partially replaced with RBP. Notably, in most cases, water-accessible porosity was the primary parameter assessed [60; 61]. [PERSON] et al. demonstrated that the incorporation of RBP can reduce the material's porosity and identified 17% as the optimal substitution level [50]. Several authors have also reported reductions in water-accessible porosity, with decreases of 5% for a 10% substitution level [62], 25% for a 20% substitution level [56], and 8% for a 40% substitution level [63]. Studies that evaluated this property using MIP tests likewise recorded porosity reductions ranging from 7.8% to 21.7%, even at substitution levels of up to 30% [64]. Very few studies have focused on examining other properties, such as electrical resistivity or resistance to chloride penetration, and those that have done so report highly variable results [57; 59; 65; 66; 67]. These variations can be attributed to differences in the mixed proportions, substitution levels, and testing methodologies employed across studies. Conversely, other studies in the literature address broader case scenarios, where mixtures incorporating RBP and additives such as fly ash are investigated, or RBP is combined with other SCMs or powders (e.g., those derived from the grinding of concrete blocks or stones), making it challenging to establish a clear comparative framework [68; 69; 70; 71; 72; 73]. In addition to the aforementioned factors, certain studies present particular cases in which recycled brick powder is used as a supplementary cementitious material (SCM), while simultaneously incorporating crushed brick as a partial replacement for both coarse and fine aggregates [74; 75]. This dual substitution further complicates the interpretation and comparison of results across different investigations. The limited number of studies focusing on the durability of mortars and concretes incorporating a partial replacement of OPC with RBP, combined with the uncertainty surrounding the data available in the literature, currently prevents this SCM from being utilised on a larger scale. Furthermore, the fact that many studies investigate RBP alongside other additions, such as FA or SF, or other waste materials used as SCMs, hinders the establishment of a clear comparative framework to distinctly identify the advantages or disadvantages of RBP. This study was conceived in response to these limitations and aims to address the existing gap in the literature. The research presented includes an analysis of mortars in which up to 45% of OPC was replaced with RBP, with its results compared to those of a reference concrete made with 100% Portland cement. The tests conducted focused on evaluating various indirect durability-related properties, including the following: (a) porosity, as it directly affects the penetration of aggressive substances into the concrete; (b) chloride penetration resistance; (c) carbonation resistance, since both chloride penetration and carbonation contribute to reinforcement corrosion, one of the primary causes of deterioration in reinforced concrete structures; and (d) resistivity, which influences the material's capacity to transport electric charges, a key factor in the ohmic control of reinforcement corrosion processes. Additionally, the effect of RBP incorporation on compressive strength was examined, and the pozzolanic reactivity of the RBP was also evaluated.