Clay Brick vs. Concrete Block
When compared to other forms of construction, the durability and resistance of masonry structures is seldom questioned. Masonry systems have stood the test of time, and rightfully earned a reputation for resilience against the elements. Considering even man-made perils, such as fire, masonry still consistently outperforms all other constructions; resisting against outright destruction which is characteristic of wood frame buildings, and outlasting the warping and ultimate collapse of steel-skeleton structures. Notwithstanding these irrefutable benefits, a masonry structure’s environmental and mechanical resistance will naturally vary and depend on the construction method and the materials employed.
Undoubtedly one of the most fundamental and durable building materials ever invented, clay bricks have been used in construction for thousands of years. The method of construction and materials have been perfected over centuries, and the durability of clay brick is dependent on the following five factors:
1. The quality of the raw/fabrication material;
2. The manufacturing process and firing condition;
3. The resultant properties of the hardened brick;
4. The conditions to which the bricks were exposed since construction; and
5. The rate of maintenance and repair.
The naturally-occurring raw material known as raw clay consists of a complex mixture of minerals in varying proportions. Production begins with selection of the clay materials and ends with the firing of the clay units; with mixing, molding and drying occurring in between. Optimal proportions of sand, clay and water along with the drying and firing temperature are integral to the quality of the hardened brick.
The clay’s composition and the manufacturing process significantly affect the dimension and distribution of the brick’s pores which has a significant impact on its durability. Consequently, treatments to enhance durability after construction is reduced to acting on external conditions – as changing the brick’s composition post-production is not possible. Preventing the invasion of water in to the brick’s mass, controlling moisture and managing the brick’s salt content are the main methods of managing the brick’s exposure to harmful conditions and increasing its durability.
Unlike clay brickwork, concrete block masonry is a relatively recent development which started being used as a building material in the mid-19th century. Concrete block walls provide sound structural resistance along with thermal and acoustic insulation all while accommodating for fast and easy installations – facilitated by the block’s precise unit measurements and modular characteristics.
Concrete blocks are composed of Portland cement, aggregates and water with production being highly automated in large industrial plants. The mix of materials is placed in a metallic mold, vibrated in to shape, and cured at an average temperature of 70°C for up to 18 hours. The durability of concrete block masonry is less dependant on externalities, and more on design and construction errors. While concrete can fall susceptible to things like efflorescence (the migration of salts from the interior to the surface material of the masonry) the effects are mainly aesthetic, and without compromise to structural integrity. Furthermore, pathologies can be prevented by deploying low-absorption blocks with high compressive strength and rebar protection.
While both concrete blocks and clay bricks can serve similar functions, skilled masons understand the inherent strengths and weaknesses which influence the conditions in which they are deployed.
Source: Ghiassi, Bahman, and Lourenc̦o Paulo B. Long-Term Performance and Durability of Masonry Structures: Degradation Mechanisms, Health Monitoring and Service Life Design. Woodhead Publishing, 2019.