Carbonation Resistance of Fly Ash-Slag Based Geopolymer Concrete
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摘要:
F级粉煤灰-矿渣基地聚物混凝土，即GPC-10（矿渣掺量10%，80 °C高温养护）和GPC-50（矿渣掺量50%，标准养护）力学性能良好，为进一步研究其抗碳化性能, 首先，对这两种地聚物混凝土进行了快速碳化试验，并与作为对照组的普通水泥混凝土(OPCC)进行了比较，通过抗压强度和劈裂抗拉强度评价了碳化对混凝土的损伤；其次，为分析损伤原因，分别通过X射线能谱分析（EDS）和压汞测试（MIP），对碳化后的成分和孔结构进行了研究；最后，建立了两种地聚物混凝土的碳化模型. 研究结果表明：相比OPCC，地聚物混凝土的抗碳化能力薄弱，尤其是钙含量较高的GPC-50，其主要产物C—A—S—H会与CO2反应而发生分解，导致孔隙率增大，进而加快了碳化速率，且碳化深度与时间呈线性关系；OPCC、GPC-10以及GPC-50的28 d碳化深度分别达到了2.0、9.2、18.8 mm.
Abstract:Two kinds of Class F fly ash-slag based geopolymer concrete, namely GPC-10 (10% slag content, 80 °C high-temperature curing) and GPC-50 (50% slag content, standard curing), are characterized by good mechanical properties. To understand better their carbonation resistance, rapid carbonation tests were carried out on the two kinds of geopolymer concrete in comparison with the ordinary Portland cement concrete (OPCC). The damage of concrete was evaluated in terms of compressive strength and splitting tensile strength. To analyze the damage cause, the composition and pore structure of the carbonized materials were investigated using X-ray energy spectroscopy (EDS) and mercury intrusion test (MIP), respectively. On this basis, carbonation models of the two kinds of concrete were established. The results show that compared with the OPCC, the geopolymer concrete has a weak carbonation resistance, especially for GPC-50, the type with high calcium content, in which the main product C—A—S—H was decomposed during carbonation, leading to an increase in porosity and thus accelerating the carbonation rate, and the carbonation depth has a linear relation with time. The 28 d carbonization depth of OPCC, GPC-10 and GPC-50 reached 2.0, 9.2 and 18.8 mm, respectively.
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Key words:
- class F fly ash /
- slag /
- geopolymer concrete /
- rapid carbonation test /
- pore structure /
- carbonation models
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图 1 3种混凝土的pH值变化（0、3、14、28 d）
Figure 1. pH changes of three types of concrete （0、3、14、28 d）
图 2 碳化对混凝土力学性能的影响
Figure 2. Effect of carbonation on mechanical properties of concrete
表 1 粉煤灰、矿渣及水泥化学成分
Table 1. Compositions ratios of fly ash，slag and cement
% 类型 SiO2 Al2O3 Fe2O3 CaO P2O5 Na2O K2O MnO MgO SO3 Tio2 SrO 粉煤灰 62.04 25.5 4.28 3.96 0.31 0.46 1.27 0.73 1.33 0.12 矿渣 34.11 15.36 0.83 35.99 0.40 0.62 1.07 6.58 2.50 2.41 0.12 水泥 20.01 5.68 3.20 65.89 0.08 0.09 1.17 0.19 0.81 2.00 
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表 2 混凝土配合比设计
Table 2. Mix proportion design and numbering of the concrete specimens
kg/m3 编号 粉煤灰 炉渣 水泥 沙 砾石 Na2SiO3 NaOH 水 减水剂 养护条件 GPC-10 346.7 38.5 601.7 1203.5 165.7 66.2 80 ℃ sealed GPC-50 192.6 192.6 601.7 1203.5 165.7 66.2 标准 OPCC 56.0 56.0 448.0 626.0 1022.0 174.7 2.5 标准
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表 3 碳化对混凝土力学性能的影响
Table 3. Effect of carbonation on mechanical properties of concrete
编号 3 d 7 d 14 d 21 d 28 d GPC-50 
GPC-10 
OPCC 
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表 4 原子相对数量
Table 4. Relative number of atoms
% 编号 O C Si Al Na Ca Ca/Na Si/Al GPC-10 59.80 18.10 11.80 3.30 3.90 3.10 0.79 3.60 GPC-50 54.10 29.40 5.80 6.50 0.70 3.40 4.80 0.89
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