Comparative Study on the Drying Shrinkage and Mechanical Properties of Geopolymer Foam Concrete Incorporating Different Dosages of Fiber, Sand and Foam Agents

A recent innovation, geopolymer foam concrete (GFC), combines the advantages of geopolymer technology and foam concrete, and provides the opportunity to reduce the environmental footprint of construction materials in terms of raw materials, embodied CO2 and operational energy in service. Foam concrete is generally defined as a type of lightweight concrete that consists of a cementitious binder with a high degree of void space, with or without the addition of fine aggregate. One of the main drawbacks of these materials is high drying shrinkage. This paper presents an extensive experimental study to reduce the drying shrinkage in foam geopolymer concrete. Moreover, mechanical properties of foam geopolymer concrete were characterized by compressive and flexural strengths. To reduce the drying shrinkage in foam geopolymer concretes different strategies used, including foam content (0.2%, 0.5%, 0.8%), sand/binder content (0.30, 0.35, 0.40, 0.45, 0.50, 0.75, 1.00, 1.25, 1.50), and using polypropylene (PP) fibers with different lengths (6 mm and 20 mm) and fiber volume fractions (0.2%, 0.6%, 1%, and 1.4%). The obtained results showed that increasing sand content up to 50% reduced the drying shrinkage, while the drying shrinkage increased above this sand content. Additionally, increasing foam content intensified the increase of drying shrinkage. This increase was proportional to foam content. In general, regardless of fiber type and content, reinforcement of foam geopolymer concrete reduced the drying shrinkage and enhanced mechanical properties.