Lightweight cement-based materials

Abstract

Nowadays, different properties are expected for building materials. Durability and high resistance are the common requirements, but every day more applications demand reduced weight as a required property. As a means of reducing environmental impact, sustainable construction requires considering not only the type of materials used, but also the way they affect the building process and the long-term performance of the structure. Lightweight materials are known for their insulating properties, thus low-energy conditioning of housing is one of the main reasons for their use in construction. However, these materials usually have poor mechanical properties. For this reason, lightweight materials are mostly used in nonstructural applications, such as covering mortars for walls, flat roof insulation, or concrete sandwich wall panels. In these cases, different approaches to lower the density of cement-based materials can be considered, such as using lightweight/low-strength aggregates, like expanded polystyrene (EPS), or increasing the water-to-cement ratio.Despite these approaches that tend to reduce the mechanical properties, it is also possible to reduce the density of a material and maintain a satisfactory strength. For example, cement can be replaced with lightweight/high-strength aggregates such as hollow glass microspheres (HGMSs), which are widely used for oil well lightweight cement slurries. These slurries usually require low density, as the pressure they exert over the formation when pumping it, which directly depends on density, is a limiting variable for its application. Another way to obtain lightweight cementbased materials with acceptable resistance is to enhance the mechanical properties of the binder.This chapter reviews three techniques for lightening cement-based materials: using EPS, HGMSs, and additives known in the oil well industry as extenders. Both insulating and mechanical properties are specially studied.