Illinois Roofing Practice Exam

Which of these most accurately describes the makeup of structural lightweight concrete?

1. Only composed of cement and water.

2. Includes only organic aggregates.

3. Portland cement and water with aggregates such as shale, clay, or slate.

4. Primarily consists of steel fibers for reinforcement.

The correct answer is: Portland cement and water with aggregates such as shale, clay, or slate.

The choice stating that structural lightweight concrete consists of portland cement and water with aggregates such as shale, clay, or slate is correct because this accurately outlines the components that contribute to its lightweight characteristics. Structural lightweight concrete is specifically designed to achieve a lower density compared to traditional concrete while still maintaining structural strength. The inclusion of aggregates like shale, clay, or slate plays a crucial role, as they are naturally lighter than standard aggregates like gravel or sand. This blend of materials not only provides strength but also enhances the thermal properties and reduces the overall weight, which can be beneficial for a variety of construction applications. The method used to produce lightweight aggregates involves heating these materials to create air pockets, which further reduces density without compromising structural integrity. Other options focus on incomplete or incorrect elements of lightweight concrete composition. For example, asserting that it is made only of cement and water overlooks the critical role that aggregates play in defining its lightweight nature. Similarly, stating that it includes only organic aggregates is misleading, as structural lightweight concrete typically utilizes inorganic materials. Lastly, emphasizing steel fibers as the primary component misrepresents the fundamental makeup of lightweight concrete, which relies predominantly on specific aggregates and not just reinforcement elements.