Materials and Structures/Materiaux et Constructions(2024 - 2024)
Verification of the presence of superabsorbent polymers (SAP) in fresh concrete: results of an interlaboratory study of RILEM TC 260-RSC
Wyrzykowski M.; Schroefl C.; Toropovs N.; Lura P.; Snoeck D.; Bettencourt Ribeiro A.; Kara De Maeijer P.; Moon J.; Assmann A.; Igarashi S.-I.; Klemm A.; Almeida F.C.R.; Boshoff B.; Erk K.A.; Falikman V.; Agostinho L.B.; Mechtcherine V.
Materials and Structures/Materiaux et Constructions, International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM), Vol.57, 2024, MAY.
(https://doi.org/10.1617/s11527-024-02334-w)
Abstract
New methods are proposed for the verification of the presence of superabsorbent polymers (SAP) in freshly mixed concrete and estimation of SAP quantity. The methods are in general based on flushing concrete with excess water. They allow separating the light, water-sorbed hydrogel particles from the mineral components in the fresh concrete and making these particles available for further tests. Two types of tests are proposed: Test 1 serves for a visual verification of the presence of SAP (qualitative test), while Test 2 enables quantifying the mass of the collected SAP as a proxy of their concentration in concrete (quantitative test). Different procedures are proposed for these two test methods and their performance is evaluated. The testing procedures were scrutinized in an interlaboratory study carried out by 14 participants from 12 countries. All participating groups detected the presence of SAP in the mix using the qualitative procedures (Test 1). Based on this outcome, we suggest that this method should be applied in the field. In contrast, while most participants obtained reasonably reliable results with the quantification procedure of Test 2, some participants reported large errors. Therefore, the quantification method needs to be further refined, starting from the experience gained in this interlaboratory study. c The Author(s) 2024.
Crack-filling effect of gel on time-dependent mechanical behavior of concrete damaged by alkali?silica reaction
Joo H.E.; Takahashi Y.
Materials and Structures/Materiaux et Constructions, International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM), Vol.57, 2024, APR.
(https://doi.org/10.1617/s11527-024-02308-y)
Abstract
This study aims to investigate the crack-filling effect of gel generated by the alkali?silica reaction (ASR) on the mechanical behavior of concrete and propose an analytical model to predict the compression behavior of ASR-damaged concrete. To identify the mechanical contribution of the gel-filling cracks, the distribution of the chemical compositions and elastic moduli of the crack-filling gels were observed using SEM?EDS analysis and nano-indentation tests. The experimental results showed that the elastic modulus of the gel with a high-calcium composition ranged from 30 to 40?GPa, which is comparable to the elastic modulus of concrete. In addition, through literature reviews of the time-dependent compression behaviors of ASR-affected concrete, it was hypothesized that crack-filling gels can contribute to the recovery of ASR damage, and that the mechanical contribution of gels depends on the ASR crack patterns and changes with time. Based on these assumptions, the resistance of the gels filling the cracks in the compression, shear, and recontact behaviors of ASR-damaged concrete was reflected in the proposed model, in which the gel resistance increased with time and became larger as the ratio of microcracks to total cracks increased. The proposed model was verified through a comprehensive comparison of analysis and test results of compression behavior of ASR-damaged specimens, and it appeared that the change in mechanical properties of concrete according to the degree of damage (ASR expansion) and time was well simulated by the proposed model. c The Author(s) 2024.