Natural zeolite is a honeycomb-structured aluminosilicate mineral with an open crystalline structure which makes it suitable for a variety of applications. Given the beneficial effects of zeolites on the properties of cementitious materials, the present paper aims to summarize the recent findings reported in the scientific literature on the use of zeolites in cement-based construction materials. This paper limits the analysis to natural zeolites. The influence of natural zeolites on the workability and setting time of cement-based construction materials revealed that increasing the zeolite content led to a reduction in workability compared to the control mixes. At the same time, the initial and final setting times of cement pastes showed a decreasing trend with an increase in the replacement percentage. The slow pozzolanic reaction of clinoptilolite zeolite results in lower flexural strength and compressive strength values of mortars at the age of 28 days. Blending zeolites with other supplementary cementitious materials resulted in improved values of the mechanical properties of mortar and concrete. The findings regarding the impact of zeolite on the durability of concrete suggest that zeolite shows promise as a viable alternative to cement, with positive effects on various aspects of durability. The majority of the durability factors are interconnected. The presence of conflicting findings is particularly significant in this context, highlighting the need for a comprehensive approach to address these challenges in the future.

In the past decades, nanomaterials have become one of the focal points in civil engineering research. When added to cement-based construction materials (e.g., concrete), it results in significant improvements in their strength and other important properties. However, the final mix characteristics depend on many variables that must be taken into account. As such, there is no general consensus regarding the influence upon the original material of certain nano-sized additives, the optimum dosage or the synergistic effect of two or more nano-materials. This is also the case for titanium dioxide (TiO₂) and nanoclay (NC). The paper focuses on reporting the existing research data on the use of the above-mentioned materials when added to mortar and concrete. The collected data is summarized and presented in terms of strength and durability properties of cement mortar and concrete containing either TiO₂ or NC. Both nano-materials have been proven, by various studies, to increase the strength of the composite, at both room and elevated temperature, when added by themselves in 0.5%~12% for TiO₂ and 0.25%~6% for NC. It can be inferred that a combination of the two with the cementitious matrix can be beneficial and may lead to obtaining a new material with improved strength, elastic and durability properties that can be applied in the construction industry, with implications at the economic, social and environmental levels.

The continuous development of urban areas around the world led to an increase in construction material use and demand, with concrete seeing significant market uptake. Although significant progress has been made to reduce the environmental impact of concrete, there is still a stringent need for improvement. One of the most widely used methods to reduce the environmental impact of the cement industry and the construction industry alike is the replacement of ordinary Portland cement (OPC) by supplementary cementitious materials (SCM). Aside from by-products of industry, SCMs could also come from natural sources. Taking into account the porous structure of zeolites and their contribution to the improvement of the mechanical and durability properties of cement-based materials, the analysis of pore structure in cement pastes incorporating micronized natural zeolite is deemed necessary. In this research, the OPC was replaced by zeolite in three different percentages: 10%, 20%, and 30% by mass. The evolution of pore structure was investigated by means of nuclear magnetic resonance relaxometry at the curing ages of 1, 7, and 28 days. The microstructure of cement pastes was assessed by scanning electron microscopy investigations at 1, 7, 14, 21, and 28 days. The obtained results show that smaller pore sizes are present in cement pastes containing zeolites during the first 7 days. However, at the age of 28 days, the reference mix exhibits a similar pore structure to the mix containing 10% micronized zeolite due to the presence of larger amounts of hydration products. Increasing the replacement percentage to 30% results in larger pores, as indicated by larger values of the relaxation time.