Over the last decades, concrete has been excessively prone to cracks resulting from shrinkage. These dimensional changes can be affected by the incorporation of supplementary cementitious materials. This work used olive waste ash (OWA), which could substantially tackle this problem and achieve sustainability goals. For this issue, five cement paste mixes were prepared by replacing cement with OWA at different percentages varying from 0 to 20% by weight with a constant increment of 5%. The water-to-cement ratio was 0.45 for all mixes. Compressive strength and flexural strength were investigated at 7, 28, and 90 days. In addition, three shrinkage tests (drying, autogenous, and chemical) and expansion tests were also conducted for each mix and measured during 90 days of curing. The experimental findings indicated that there was a loss in compressive and flexural strength in the existence of OWA. Among all mixes containing OWA, the samples incorporating 10% OWA exhibited maximum strength values. Furthermore, the chemical and autogenous shrinkage decreased with the incorporation of OWA. However, the drying shrinkage decreased at lower levels of substitutions and increased at higher replacement levels. In addition, there was a growth in expansion rates for up to 10% of OWA content, followed by a decrease at higher levels (beyond 10%). Additionally, correlations between these volumetric stability tests were performed. It was shown that a positive linear correlation existed between chemical shrinkage and autogenous and drying shrinkage; however, there was a negative relationship between chemical shrinkage and expansion.

In recent decades, adopting alternative resources in infrastructure applications has garnered global attention to address environmental concerns. Olive waste ash (OWA), a locally available byproduct obtained from the olive oil production process, is a promising green material that plays a vital role as a partial cement substitute. This paper evaluates the mechanical and durability properties of cement paste—a key component of paving blocks—incorporating OWA at replacement levels of 0, 5, 10, 15, and 20%, with a constant water-to-cementitious ratio of 0.45. Density, compressive strength, and flexural strength are assessed at 1, 7, 28, and 90 days, while total water absorption (TWA) and capillary water absorption (CWA) are measured at 28 days. The results reveal that OWA slightly reduces density, compressive strength, and flexural strength, with the optimal results observed at a substitution level of 10%. At 90 days, the compressive strength of the control cement paste is 50 MPa, whereas the 10% OWA mixture exhibits a value of 46 MPa, corresponding to only an 8% reduction. Additionally, two predictive models are proposed: the hyperbolic model for compressive strength variation with curing time and the capillary-diffusive model for capillary water absorption as a function of time. Both models demonstrate a strong fit with experimental data. Correlations between different properties indicate a strong correlation between compressive strength, density, and flexural strength, while a negative linear relationship exists between compressive strength and water absorption. This study underscores OWA’s potential to improve sustainable paving blocks by providing suitable mechanical and durability characteristics, offering both environmental and economic benefits.