School of Civil Engineering, Suranaree University of Technology, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand.
School of Civil Engineering, Suranaree University of Technology, 111 University Avenue, Muang District, Nakhon Ratchasima 30000, Thailand; Center of Excellence in Innovation for Sustainable Infrastructure Development, Suranaree University of Technology, Thailand.
Sci Total Environ. 2016 Dec 15;573:19-26. doi: 10.1016/j.scitotenv.2016.08.078. Epub 2016 Aug 19.
In this research, a low-carbon stabilization method was studied using Recycled Asphalt Pavement (RAP) and Fly Ash (FA) geopolymers as a sustainable pavement material. The liquid alkaline activator (L) is a mixture of sodium silicate (NaSiO) and sodium hydroxide (NaOH), and high calcium FA is used as a precursor to synthesize the FA-RAP geopolymers. Unconfined Compressive Strength (UCS) of RAP-FA blend and RAP-FA geopolymer are investigated and compared with the requirement of the national road authorities of Thailand. The leachability of the heavy metals is measured by Toxicity Characteristic Leaching Procedure (TCLP) and compared with international standards. The Scanning Electron Microscopy (SEM) analysis of RAP-FA blend indicates the Calcium Aluminate (Silicate) Hydrate (C-A-S-H) formation, which is due to a reaction between the high calcium in RAP and high silica and alumina in FA. The low geopolymerization products (N-A-S-H) of RAP-FA geopolymer at NaOH/NaSiO=100:0 are detected at the early 7days of curing, hence its UCS is lower than that of RAP-FA blend. The 28-day UCS of RAP-FA geopolymers at various NaOH/NaSiO ratios are significantly higher than that of the RAP-FA blend, which can be attributed to the development of geopolymerization reactions. With the input of NaSiO, the highly soluble silica from NaSiO reacted with leached silica and alumina from FA and RAP and with free calcium from FA and RAP; hence the coexistence of N-A-S-H gel and C-A-S-H products. Therefore, the 7-day UCS values of RAP-FA geopolymers increase with decreasing NaOH/NaSiO ratio. TCLP results demonstrated that there is no environmental risk for both RAP-FA blends and RAP-FA geopolymers in road construction. The geopolymer binder reduces the leaching of heavy metal in RAP-FA mixture. The outcomes from this research will promote the move toward increased applications of recycled materials in a sustainable manner in road construction.
在这项研究中，研究了一种使用再生沥青路面（RAP）和粉煤灰（FA）地聚合物作为可持续路面材料的低碳稳定方法。液体碱性激活剂（L）是硅酸钠（NaSiO）和氢氧化钠（NaOH）的混合物，高钙粉煤灰（FA）用作合成 FA-RAP 地聚合物的前体。研究了 RAP-FA 混合物和 RAP-FA 地聚合物的无侧限抗压强度（UCS），并将其与泰国国家道路当局的要求进行了比较。通过毒性特征浸出程序（TCLP）测量重金属的浸出率，并与国际标准进行比较。RAP-FA 混合物的扫描电子显微镜（SEM）分析表明形成了钙铝酸盐（硅酸盐）水合物（C-A-S-H），这是由于 RAP 中的高钙与 FA 中的高硅和氧化铝之间的反应所致。在固化的早期 7 天内，RAP-FA 地聚合物中的低地聚合物化产物（N-A-S-H）在 NaOH/NaSiO=100:0 时检测到，因此其 UCS 低于 RAP-FA 混合物。在各种 NaOH/NaSiO 比下，RAP-FA 地聚合物的 28 天 UCS 明显高于 RAP-FA 混合物，这归因于地聚合反应的发展。随着 NaSiO 的投入，NaSiO 中高可溶性硅与 FA 和 RAP 中浸出的硅和氧化铝以及 FA 和 RAP 中游离钙反应；因此，存在 N-A-S-H 凝胶和 C-A-S-H 产物共存。因此，RAP-FA 地聚合物的 7 天 UCS 值随 NaOH/NaSiO 比的降低而增加。TCLP 结果表明，在道路建设中，RAP-FA 混合物和 RAP-FA 地聚合物都没有环境风险。地聚合物粘合剂减少了 RAP-FA 混合物中重金属的浸出。这项研究的结果将促进以可持续的方式增加回收材料在道路建设中的应用。
