稻壳灰生态混凝土的力学及植生性能

Mechanical and vegetation properties of rice husk ash ecological concrete

【目的】利用工业发电过程中产生的废弃稻壳灰替代硅灰制备稻壳灰生态混凝土,改善生态混凝土的强度和植生性能,降低生态混凝土制造成本的同时保护生态环境。【方法】采用稻壳灰部分代替硅灰作为胶凝材料,保持硅灰和稻壳灰质量之和不变,对稻壳灰代替硅灰进行第1次配比设计,研究水和胶凝材料的质量比(水胶比)、稻壳灰替代率对稻壳灰生态混凝土强度的影响,确定最佳水胶比和稻壳灰替代率的取值范围;进行第2次配比设计,采用Design Expert软件进行响应面分析,研究水胶比、稻壳灰替代率和孔隙率对稻壳灰生态混凝土抗压强度和抗折强度等力学性能的影响,确定最佳水胶比和稻壳灰代替率,并采用狗牙根、黑麦草、高羊茅3种草本植物验证稻壳灰生态混凝土的植生性能。【结果】随着稻壳灰替代率的增大,稻壳灰生态混凝土的强度呈现先增大后减小的趋势,最佳稻壳灰替代率为55%;3种草本植物均能够在稻壳灰生态混凝土中正常生长,高羊茅植生性能最佳。【结论】稻壳灰可以替代硅灰用作胶凝材料,制备的稻壳灰生态混凝土具有良好的力学性能和植生性能。

Objective In order to enhance the strength and planting performance of ecological concrete, while effectively utilizing the waste rice husk ash generated from industrial power generation.Methods In this study,the mix design was conducted in two stages using the volume method. Initially,the first mix design focused on investigating the water-binder ratio and the proportion of rice husk ash replacing silica fume as influencing factors. Different water-binder ratios( 0. 20, 0. 25, 0. 30, 0. 35) were chosen,and the substitution ratesofrice husk ash for silica fume varied from 0% to 100%(0,20%, 40%, 60%, 80%, 100%), with a porosity of 20%and 7. 5% silica fume content. Subsequently, the second mix design was carried out using response surface methodology, considering influencing factors such as porosity, water-binder ratio, and rice husk ash substitution rate. The objective was to optimize the mix design based on mechanical properties through multifactor analysis. Additionally, the planting performance was validated using three herbaceous plants: bermuda grass, ryegrass and tall fescue.Results and Discussion At 7 days, as the substitution rate of rice husk ash increases, the strength of ecological concrete decreases gradually under the three different water-binder ratios. This is due to the larger specific surface area of rice husk ash compared to silica fume, resulting in higher water demand that affects the early hydration process of cement. Rice husk ash, acting as a reactant for the secondary hydration reaction within the concrete, has a limited impact in the early stages. At 28 days, with the increase in rice husk ash substitution rate, both compressive and flexural strengths first increase and then decrease. In the compressive strength test, under water-binder ratios of 0. 25 and 0. 35, the compressive strength of ecological concrete gradually increases from 0 to 60% substitution rate. At a water-binder ratio of 0. 3, lower rice husk ash substitution rates( 0 to 40%) lead to gradual strength enhancement of ecological concrete due to sufficient curing age allowing full hydration of the cementitious materials, resulting in additional formation of calcium silicate hydrate gel. However, under the water-binder ratio of 0. 25 and 0. 35 during the increase in rice husk ash substitution rate from 60% to 100%, and at a water-binder ratio of 0. 3 during the increase in rice husk ash substitution rate from 40% to 100%, the compressive strength of ecological concrete decreases with higher rice husk ash substitution rates. In contrast, the flexural strength at 28 days exhibits similar patterns among the three water-binder ratios: an increase in ecological concrete's flexural strength from 0 to 60% substitution rate, followed by a decrease in strength from 60% to 100% substitution rate of rice husk ash.Conclusion In this study, rice husk ash is investigated as a potential replacementfor silica fume in the preparation of ecological concrete,which exhibits good mechanical properties and planting performance. Using the response surface analysis, the factors such as water-binder ratio, rice husk ash substitution rate and porosity significantly affect on the concrete's strength, with the porosity exhibiting the most significant effect on the strength change.