Engineering behavior of ambient-cured geopolymer concrete activated by an alternative silicate from rice husk ash

Manufacturing of commercialized silicate is a highly polluting source in geopolymer production. To reduce these emissions, rice husk ash has been considered as an option for synthesizing alternative silicate. However, available research has been focused on the study of geopolymer pastes and mortars, but unknowns remain on its reliability to manufacture plain geopolymer concrete, motivating this research. Goals were synthesizing an unfiltered-alternative sodium silicate from rice husk ash at room conditions (21 °C − 65 ± 5%RH − atmospheric pressure) for manufacturing plain ambient-cured geopolymer concrete and assess its engineering properties. Results shown that the proposed concrete reached 21 MPa, 17959 MPa, 0.183, and 2.13 MPa for 28-day compressive strength, modulus of elasticity, Poisson’s ratio, and splitting tensile capacity, respectively. Results also portrayed that all these properties of the proposed concrete were comparable to those of geopolymer concrete with commercial silicate and traditional Portland-cement concrete. Its elasticity modulus was 44% higher than that of the geopolymer concrete with commercial silicate, which is considered as serviceability proxy. Based on the results, three equation models were developed to predict the engineering properties of the proposed concrete. Results demonstrate that the use of alternative silicate from rice husk ash provides an innovative-cheaper and eco-friendlier geopolymer concrete exhibiting suitable properties for structural applications.HIGHLIGHTSAlternative sodium silicate from rice husk ash has not been assessed in geopolymer concreteAn alternative sodium silicate from rice husk ash was prepared at room temperatureGeopolymer concrete shows 44% higher modulus of elasticity with alternative silicateEmpirical models were developed to predict the engineering properties of the geopolymer concrete with alternative silicateGeopolymer concrete with alternative silicate is reliable for structural applications Alternative sodium silicate from rice husk ash has not been assessed in geopolymer concrete An alternative sodium silicate from rice husk ash was prepared at room temperature Geopolymer concrete shows 44% higher modulus of elasticity with alternative silicate Empirical models were developed to predict the engineering properties of the geopolymer concrete with alternative silicate Geopolymer concrete with alternative silicate is reliable for structural applications

商业化硅酸盐的生产是地质聚合物（geopolymer）生产过程中的高污染来源。为降低此类排放，稻壳灰（rice husk ash）被视为合成替代型硅酸盐的可选原料。然而，现有研究多聚焦于地质聚合物净浆与砂浆的相关研究，而素型常温养护地质聚合物混凝土的可靠性仍存在未知，这也成为本研究的开展动因。
本研究的目标为在室温条件（21℃，相对湿度65±5%，大气压）下，从稻壳灰中合成未过滤的替代硅酸钠（sodium silicate），用于制备素型常温养护地质聚合物混凝土，并评估其工程性能。
研究结果表明，该制备的混凝土28天抗压强度达21MPa、弹性模量（modulus of elasticity）为17959MPa、泊松比（Poisson’s ratio）为0.183、劈裂抗拉承载力为2.13MPa。该混凝土的各项工程性能均与商业化硅酸盐地质聚合物混凝土及传统硅酸盐水泥混凝土相当；其弹性模量较商业化硅酸盐地质聚合物混凝土高出44%，该特性可作为服役适用性的代用评价指标。基于上述结果，本研究开发了三个方程模型，用于预测该混凝土的工程性能。结果显示，采用稻壳灰基替代硅酸盐可制备出兼具创新性、低成本与环境友好性的地质聚合物混凝土，其性能满足结构应用要求。
#### 研究亮点
1. 稻壳灰基替代硅酸钠此前未在地质聚合物混凝土中得到应用评估；
2. 成功在室温条件下制备了稻壳灰基替代硅酸钠；
3. 采用该替代硅酸钠的地质聚合物混凝土弹性模量较商业化硅酸盐组提升44%；
4. 开发了经验模型（empirical models）以预测该替代硅酸钠地质聚合物混凝土的工程性能；
5. 稻壳灰基替代硅酸钠制备的地质聚合物混凝土可可靠应用于结构工程领域。