## 1 Introduction  
Ordinary Portland cement (OPC) is made of blends of mineral admixtures and its usage as a binder of concrete material [1]. Although cement can provide the main strength source of OPC, its manufacturing process also greatly affects the environmental pollution. The carbon dioxide emissions produced each year also account for 6% of the global total [2]. For the maintenance of the global environmental climate, Scholars from all over the world are eager to find alternative cements, hoping to find environmentally friendly materials that can have the same benefits as cement under the premise of resource reuse. geopolymer is an engineering material term coined by [PERSON] in 1978. It describes this kind of material as a geotechnical material with similar adhesive properties and can have the conditions to replace cement [3; 4; 5; 6]. The main reaction of geopolymerization is to produce two chemical reactions with sodium hydroxide (NaOH) through silicon (Si) or aluminum (Al). The first reaction will destroy the structure of its chemical chain and cause Si or Al to be released from the material; The two reactions will become anhydrous calcium silicate and initiate the polymerization reaction [7]. Using industrial byproducts such as fly ash, slag and metakaolin, as materials for producing geopolymers [8; 9; 10; 11; 12] enables waste recycling and the production of new materials, as well as reduces the use of cement in concrete to decrease global carbon emissions [13; 14]. Geopolymers possess excellent thermal stability as well as decent mechanical and physical functions, making them a type of green cement with properties similar to that of Portland cement [15] that can be used in precast concrete products during infrastructure development [16; 17]. As an environmentally friendly material, geopolymers have been found to be ideal substitutes for ordinary Portland cement (OPC) [18; 19; 20; 21; 22]. Under the research and promotion of many scholars, it is generally believed that geopolymer concrete can provide better mechanical properties, durability and environmental protection than ordinary concrete. Because of the emergence of novel materials, it is of considerable help to the civil engineering community. Many scholars have also studied geopolymers. One of the main reasons is that the silicon and aluminum elements reacted in it can be obtained from industrial by-products [23; 24]. Using nickel slag to replace 20% and sodium silicate modulus between 1.0 and 2.0 can obtain the best compressive strength and the lowest shrinkage [25]. Rice hull ash can increase the bonding strength of the Si-O-Si chain. When the substitution amount is 35% and the geopolymer produced by 10-M NaOH solution has a very dense crystal structure under the observation of scanning electron microscope (SEM) [26]. The addition of nano-silica helps to increase the high-calcium fly ash polymer's martensitic strength and flexural strength. When adding one to two percent, the structure observed under the microscope will be denser [27]. Because of the distinct source of materials used, the base material will also indirectly influence the properties of the geopolymer. The most serious problem in terms of the durability of concrete structures is sulfate attack. The deterioration of cement paste is caused by expansion, peeling and embrittlement depending on the conditions of sulfate attack. By contrast, geopolymer concrete possesses a higher resistance against sulfate attack [28]. geopolymers are high-strength alkali cementing materials that do not rely on calcium and are formed under high-alkali conditions through the blending of aluminosilicate materials with an alkali-metal-silicate solution [29].