Orthogonal Experimental Study on the Factors Affecting the Mechanical Properties of Alkali-Activated Slag Materials

Blast furnace slag is one of the largest solid wastes in the world. The slag-based geopolymer obtained by alkali activation has many advantages, such as a high strength, a good corrosion resistance, low carbon and environmental protection. Existing studies have shown that the mechanical properties of slag-based geopolymers are related to the combined effects of many factors, but there is still a lack of reliable conclusions on the primary and secondary influence degree of each factor, which greatly affects the scientific preparation and application of slag-based geopolymers. In order to solve this problem, we choose to proceed from the two perspectives of the mix ratio of the alkali activator and the elemental composition of raw materials. Through the orthogonal analysis method, this paper studies the influence of the modulus of the alkali activator, the solid-to-liquid ratio of the activator, the water-cement ratio and the metakaolin replacement rate on the uniaxial compressive strength of a slag-based geopolymer. The results show that when the solid-liquid ratio is about 0.25, the modulus of the alkali activator is 1.3~1.5, the water-cement ratio is about 0.4 and the samples with higher strength can be prepared. With the addition of metakaolin, a new gel phase NASH was formed in the system, which significantly promoted the late strength and toughness growth of the sample. The research results comprehensively analyze the influence of different factors on the mechanical properties of the slag-based geopolymer, which can provide a valuable reference for the engineering application of alkali-activated slag materials.