| Geopolymer is a kind of new cementitious material of a 3-D dimensional framework structure consisted of linked SiO4 and AlO4 tetrahedra. Geopolymeric materials has many advantages, such as wide sources of raw materials, simple manufacture process, low energy consumption, few emissions of CO2, excellent properties of strength, anti-corrosion and radiation resistance. Therefore it has wide application prospect of engineering. However, in the practice of application, it has been found many defects such as geopolymer new mix slurry has poor workability, very difficult to control setting time at different temperatures,etc. which greatly restricted application.In this paper, the rheological characteristics of geopolymer slurry(GS) and the internal influence factors on the workability of geopolymer was analysed and studied. The setting phenomenon of geopolymer slurry in different temperature was measured and controlled by retarder at high temperature and accelerator at room temperature. On the basis, a new two-component geopolymer coating which has good corrosion resistant, high temperature resistant, good adornment performance and low cost is suitable for surface brushing, rolling and other processes was developed.High plastic viscosity, low yield stress and too long setting time at room temperature directly affect the workability of geopolymer slurry during the construction process. Effectively controlling the viscosity of geopolymer slurry is very important for its workability. In this paper, the rheological characteristics in the condition of temperature, concentration,modulus of sodium silicate solution (VSS) and GS were analyzed. The results show that in ambient temperature the viscosity of VSS got the minimum value while the modulus was 2.2; but the effect of modulus on viscosity of VSS was gradually weaker with ascend of temperature. When VSS was in the true solution(high-ionized) zone, the difference of GS viscosity of different VSS modulus was little; while in the water glass (SiO2-polymerized) zone, plastic viscosity of GS increase sharply with the increase of modulus of VSS. With increasing of the concentration of VSS, both viscosity of GS and VSS was all increased. Plastic viscosity of GS got the minimum value at 30℃in different modulus. This paper attempts the method that reducing the viscosity of sodium silicate solution in order to reduce the viscosity of GS, which could improve the workability of GS. And ultrasonic treatment of VSS could be taken to improve the properties of GS. And ultrasonic treatment of VSS could be improved the fluidity of GS and augment the compressive strength of geopolymer. It is recommended that the viscosity of sodium silicate solution used in the production process should be in a reasonable range, if necessary, modified by ultrasonic treatment, to reduce the viscosity of GS and augment the compressive strength of geopolymer.Setting time of geopolymer was affected by many factors, and the most important of them is temperature. Geopolymer sets too fast at high temperature but too slow at room temperature,which seriously affect the orderly construction, and is difficult to guarantee the product quality of geopolymer. To solve those problems, the retarder at high temperature and accelerant at room temperature were found to control setting time at different temperature. Meanwhile, reasonable processes were made in the process of production. The results show that the effect of retarder ZA and BA on geopolymer slurry at high temperature was obvious, and with the mix amount increase, retarding effects improve. To control the setting time of geopolymer slurry at high temperature was achived. Retarding mechanism at high temperature were discussed, and it was considered that the reaction between BA or ZA and sodium silicate solution was rapid, and the surface of metakaolin was wrapped with reaction product, which hindered the dissolution of metakaolin structure and effectively extended the setting time. However, the integument suffered destruction as the geopolymeric reaction happened, without damage long-term strength of geopolymer. The effect of accelerant AB and CB on GS at room temperature was obvious, and with the mix amount increase, accelerate effects improve. To control the setting time of GS at room temperature was achived. Accelerating mechanism at room temperature was analyzed, and it was considered that the reaction between CB and AB and sodium silicate solution quickly generated auxiliary products in the same period, and made the geopolymer structure generate fast, so setting time became much shorter. It was found that geopolymer slurry was pseudoplastic fluid with low yield stress, which had thixotropy. The flow characteristics of geopolymer slurry which had increased the yield stress value, was much suitable for the preparation of coating. For the unique property of geopolymer slurry and previous repeated properties improvement, the building coating of geopolymer was developed, and then the national patent of invention was applied for. Corrosion resistance, freezing and thawing resistance of geopolymer coating have reached the national standard. It also has good high temperature resistance and durability, which is a excellent green building coating. Due to the problem of bad coating appear (such as smooth, flat and dry cracking level), relative solutions were proposed. The flatness of geopolymer coating was improved by adding the compound of bentonite and sodium carboxymethyl cellulose as suspension. Dry cracking resistance of coating got improved due to adding filler powers with wide bimodal size distribution. The smoothness of coating got improved by adding talc. Geopolymer coating had good corrosion and heat resistant with non-toxic and harmful gases release during the process of construction and use in public places.
|
PDF Full Text Request