Investigation on Durability Behaviour and Optimization of Concrete with Triple‐Admixtures Subjected to Freeze‐Thaw Cycles in Salt Solution

Abstract

In the seasonal frozen area of northeast China, cement concrete is usually in a working environment of cold climate and chlorine erosion coupling effect. In general, with a reasonable addition of air entraining agent (AEA) and multimineral admixtures such as fly ash, blast furnace slag, and silica fume, the durability of cement concrete under the effects of freeze-thaw and salt solution can be significantly improved in cold regions. However, due to several more compositions of cement concrete with multiple mineral admixtures, it would take excessive trial mixtures to select the desired mixture proportion based on the conventional method. This means a great deal of costs of raw materials and laboratory experimental time. In this paper, the experimental scheme of mixture proportion for air-entrained concrete with multimineral admixtures was designed based on the orthogonal experiment design method. Based on the compressive strength, rapid chloride permeability, and weight loss and relative dynamic elastic modulus after salt freeze-thaw cycles, the influence of different mineral admixtures and their dosages on the durability of concrete subjected to freeze-thaw in salt solution was analyzed. After that, based on genetic algorithm, an optimization of mixture proportion was proposed, which only requires less trial mixes and accessible optimization process. The test results indicated the superiority of air-entrained concrete with multimineral admixtures when serving in salt freeze-thaw environment. Eventually, it was also verified that the optimized concrete in this paper could achieve pleasurable durability performances under salt freeze-thaw cycles.

Durability Evaluation of Concrete with Multiadmixtures under Salt Freeze‐Thaw Cycles Based on Surface Resistivity

“…From Figure 5(b), it can be seen that the 28-day flexural strength of control cement concrete is 4.95 MPa, and the flexural strength of cement concrete is 4.48 MPa, 4.25 MPa, and 3.92 MPa when the FA contents are 10%, 20%, and 30%, which indicates that the flexural strength of cement concrete decreases with the increase of FA content, which is line with the findings of Mardani-Aghabaglou et al [51]. It can be seen from Figure 5(c) that the surface resistivity increases with the increase of FA content, and the surface resistivity changes slightly with the increase of FA content in the range of 10%∼ 20%, as previously described in [59]. In Figure 5(d), the rapid chloride permeability of control cement concrete in 28 days is 1951.5 C. With the increase of FA content, the rapid chloride permeability decreases.…”

“…It can be seen from Figure 8(d) that the rapid chloride permeability of concrete can be effectively reduced in the case of double mixing, but when 6% SF is added, the rapid chloride permeability is only 287.5 C, which indicates that SF can effectively reduce the rapid chloride permeability of concrete. is is similar to the previous research results [39,43,59]. e results showed that the mechanical properties of the concrete are better than that of the control cement concrete, which indicates that the hydration and secondary hydration of mineral admixtures are sufficient in the process of strength formation, which can provide strength for the concrete [1,34,58].…”

“…e test results indicate that compressive strength and flexural strength are consistent with previous study [43,59,60]. From Figure 6(c), it can be seen that the surface resistivity of concrete increases fastest when the BFS content is 0%∼10% and slows down when the BFS content is 10%∼30%, which indicates that adding a small amount of BFS can improve the surface resistivity of concrete [59]. It can be seen from Figure 6(d) that the rapid chloride permeability of cement concrete decreases linearly with the increase of BFS content in the content range of 0%∼30%.…”

“…When the SF content is 6%, the flexural strength of concrete has a maximum value. e strength results are consistent with the analysis results [50,51,59]. It can be seen from Figure 7(c) that with the increase of SF content, the surface resistivity of concrete increases.…”

“…When the FA content is within 0%∼10%, the rapid chloride permeability decreases the most. When the FA content is higher than 10%, the reduction range of rapid chloride permeability becomes smaller, which indicates that the appropriate content of FA can effectively reduce the rapid chloride permeability of concrete [59].…”