A Research on Durability Degradation of Mineral Admixture Concrete

Abstract

In order to study the degradation laws and mechanisms of admixture concretes with single-added SO42− and composite of Mg2+ and SO42−, respectively, the durability tests were conducted on three types of mineral admixture concretes (concretes with single-added metakaolin (MK), single-added ultra-fine fly ash (UFA), and composite of metakaolin and ultra-fine fly ash (MF), and one reference concrete. In these tests, the 10% Na2SO4 solution and the 10% MgSO4 solution were used as the erosion medium, and the drying-wetting circle method was applied. It can be seen from the compressive tests and grey relational analysis that the MK admixture can improve the anti-Na2SO4-erosion capability of the concrete significantly, but weaken its anti-MgSO4-erosion capability; the UFA admixture can improve both the anti-Na2SO4-erosion and the anti-MgSO4-erosion capability of the concrete; and the composite admixture has superimposed effects and can enhance erosion resistance against these two erosion mediums. The phase composition and the changes of the macro morphology and the micro structure during the erosion process caused by mono sulfate ions and complex ions has been observed through X-ray diffraction (XRD), FTIR spectrum (FTIR), and scanning electron microscope (SEM), based on which it was determined that the erosion of single-added SO42− ions can produce erosive outputs of ettringite, gypsum, and mirabilite in the concrete, and cause corner scaling or deformation. Mg2+ and SO42− reacted in the concrete and produced brucite, M-S-H, ettringite, and gypsum, etc. The erosion of complex ions can cause scaling of the cement mortar and aggregate from the surface or the desquamation of corners.

Experimental Study on the Strength and Hydration Products of Cement Mortar with Hybrid Recycled Powders Based Industrial-Construction Residue Cement Stabilization of Crushed Aggregate

“…Consequently, this process effectively mitigates the decline in later compressive strength of the concrete [ 51 ]. Li [ 52 ] and others found that the combination of RBP, slag, and fly ash can effectively improve the 28 d flexural strength of mortar; Chen [ 53 ] and others believed that the mixture of RBP and fly ash could decrease the porosity of the composite cementitious material and increase enhanced erosion resistance.…”

Influence of chloride and sulfate solution on the long‐term durability of modified rubberized concrete

“…The expanding forces created by sulfate interacting with the calcium aluminum hydrates to form ettringite caused expansion and cracking. [8][9][10] The P-wave velocity of RuC increases as the immersion period of concrete in NaCl solution increases. RuC's mechanical characteristics improved as rubber particle size increased from 1-3 mm to 3-6 mm but decreased when rubber content increased.…”

“…Expansion, cracking, and M‐S‐H (magnesium silicate hydrate) production contributed to the reduction in compressive strength. The expanding forces created by sulfate interacting with the calcium aluminum hydrates to form ettringite caused expansion and cracking 8–10 . The P‐wave velocity of RuC increases as the immersion period of concrete in NaCl solution increases.…”

Effect of Chlorine Salt on Durability of Mineral Admixture Concrete under Different Conditions

“…The fly ash and slag in traditional mineral admixtures have adverse effects on the mechanical performance of concrete at early stages [25]. However, because of its high pozzolanic activity, metakaolin can promote cement hydration, considerably improving the mechanical performance of concrete at the early stage [26]. Ultra-fine fly ash (UFA) is obtained by processing waste from coal-fired power plants.…”