Arcosa Lightweight’s expanded shale and clay aggregates add significant value to LWT CMU beyond reducing weight. The ceramic-like lightweight aggregate is made by expanding selected raw shale or clay minerals in a rotary kiln at temperatures over 2000°F. This expansion process creates an aggregate that is structurally strong, durable, inert, and lightweight, benefiting concrete masonry units at all stages of design, construction, and operation.

All CMU offer very good fire resistance ratings and perform as designed in real-life fire situations. LWT CMU perform even better because the expanded shale or clay LWAs in them contain trapped air bubbles, which act as an insulator. As a result, less concrete is required to achieve the fire resistance ratings when making LWT CMU versus normal weight CMU.

LWT CMU can easily and economically achieve two, three, and four-hour fire ratings based on the minimum equivalent thickness required by building codes. Because the LWAs in LWT CMU act as insulators, less concrete is required to withstand fire conditions. Additionally, more LWT CMU can be stacked on a single pallet, reducing the number of truckloads required for transportation, which in turn lowers fossil fuel consumption and benefits the environment.

According to ASTM C90, regular LWT CMU made with concrete weighing no more than 105 pounds per cubic foot (pcf) are required to have a minimum compressive strength of 2,000 pounds per square inch (psi). However, SmartWall units exceed both the minimum ASTM C90 density and strength requirements.

SmartWall blocks have a concrete density less than or equal to 93 pcf, a minimum compressive strength of 2500 psi, and are made using an optimized gradation of Arcosa Lightweight aggregates combined with regular aggregates. Higher strength allows structural engineers to design even more efficient load-bearing structures, and the lighter weight of these units improves mason productivity and can shorten construction schedules.

Depending on the number of cross webs and web thicknesses, insulated LWT CMU can have R-values that are 2-3 times higher than identical NWT CMU. These higher R-values make meeting energy codes easier. It is recommended to use COMCheck software to determine energy code compliance for commercial buildings.

Whole building computer modeling studies have shown that LWT CMU, including traditional 3-web and newer 2-web units, perform well in all eight climate zones, especially in schools, supermarkets, and big-box retail stores.

Using lightweight CMU benefits not only the design team but also masons and subcontractors. The 30-40 percent lighter weight of LWT CMU speeds up the construction of CMU walls and reduces back and musculoskeletal injuries. Reducing job site injuries significantly lowers Worker Compensation Claims, which in turn reduces insurance premiums for mason contractors and wall costs for building owners.

In most regions of the U.S., mason wages have reached a point where placing just two additional blocks per hour into the wall offsets the higher cost of LWT CMU. Since project owners are paying for a finished wall, if the finished cost is the same or less with LWT CMU, why not use it? LWT CMU provides a better product, enhances mason productivity, and preserves health and wellbeing, allowing contractors to complete more projects while delivering a superior product.

LWT CMU made with Arcosa Lightweight aggregates benefits all stakeholders involved in the design, manufacturing, construction, and operational phases of a building’s life.