![]() ![]() Other differences are more substantial, such as compressed earth/clay products whose visual appearance mimics that of concrete masonry but with few other similarities. Some of the material differences are small, such as units that are manufactured with small amounts of recycled or by-product materials that are similar in nature to constituent materials traditionally used in production. The introduction of new manufacturing technologies, alternative or non-traditional constituent materials, unique unit configurations, and ever-expanding market-driven applications has in recent years pushed the boundaries of what has conventionally been known as a “concrete masonry unit” into areas where some, or most, would no longer associate a given product with historical definitions for these units. Further, regardless of whether you are studying a newly constructed building or a 100 year old foundation – those concrete units are concrete masonry units, CMU, concrete block…or if you prefer, cinder block – although it is nearly impossible to tell visually if a given unit contains actual cinders. The reality is that all concrete masonry units used in construction must meet minimum requirements established by building codes, regardless of whether they contain cinders or not. Consequently, some associate cinder block with inconsistent or poor quality units produced in early 20 th century, which has led some to believe that cinder block are not permitted to be used to construct buildings today. Likewise, codes and standards have evolved through the years to comprehensively address minimum physical requirements for concrete masonry to ensure the long-term durability and performance of these products. What has changed over the past 100 years is the technology used today to produce concrete masonry results in a consistently high-quality product with uniform properties. As previously discussed, cinders (both volcanic and coal combustion by-products) continue to be used in block production today – as such, there is no differentiating a concrete block from a cinder block based upon its age. As such, the density of a block is not an indication of whether it has been manufactured with or without cinders.įor many the term cinder block is associated with older concrete masonry presumably manufactured during the first half of the 20 th century. While it is true that a concrete block manufactured with cinders will tend to have a lower density compared to a concrete block manufactured with stone aggregate, there are many other lightweight aggregate types (both natural and man-made) that are commonly used in block production. Yet, using cinder aggregates as a lightweight alternative to stone and gravel aggregate may have inadvertently led to another common misconception regarding the term cinder block: that cinder block are lighter (have a lower density) compared to concrete masonry units. The practice of incorporating coal combustion cinders (as well as other waste by-products) into concrete masonry units continues today. The use of waste by-products such as coal cinders effectively made concrete masonry the first construction material to adopt green, sustainable practices a century before it was fashionable to do so. Soon after, the terms “cinder” and “block” were perpetually linked. Cinders, which include both waste by-products of coal combustion as well as volcanic cinders, were an ideal, cost- effective, lightweight aggregate that was readily available in many areas of the country. To reduce the unit weight, many producers (but not all) incorporated cinders into their block as an alternative to conventional stone aggregate. In the early years of the 20 th century as concrete masonry units were beginning to be used with more frequency, producers were looking for ways to reduce the weight of the units to facilitate their use in construction and increase mason productivity. The reality, however, is that these masonry units are essentially the same product produced with the same three basic constituent materials: water, cement, and aggregate. There are many, many opinions and theories that have been proposed through the years (and continue to circulate) that attempt to explain the difference between a “concrete block” and “cinder block”. ![]() Related concrete products, manufactured using similar materials and production methods but used in different applications, include products such as concrete pavers, segmental retaining wall units, and articulating concrete block. Concrete masonry units are colloquially known by many names, most predominately “concrete block”, “cinder block”, “CMU”, or simply “block”. ![]()
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