PSI - Issue 23

Aneta Nowak-Michta et al. / Procedia Structural Integrity 23 (2019) 77–82 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

5

81

= 1  = 1

(1)

(2)

Fig. 3. I D in NAEC and AEC.

Fig. 4.  f c in NAEC and AEC.

The liquefaction NAEC mixes (S2, S3 and S4) by SP contributed to: the increase in slumps, the decrease in the air content (both in concrete mixes Vp and in hardened concretes A - tables 3 and 4), the increase in density by 2.13, 0.94 and 1.38% (Fig. 3) and consequently the increase in strength by 13-14% (Fig. 4). As the SP content and liquefaction of concrete mixes increased, the specific surface area of the pore ( α ) and the micropore content (A 300 ) decreased (Table 4). The decrease in the total air content A (table 4) by 1.2, 1.7 and 1.5 were confirmed by I D (Fig.3) and shows that SP liquefies the concrete mix to a certain level as well as densifies it (S2 and S3) by reducing the technological pore content. However, the significant liquefaction (S4) reveals a negative effect in the form of additional AE. As a consequence, when the consistency changed from S1 to S2, the compressive strength increased by 13%, from S2 to S3 by only 1%, and with the transition in consistency from S3 to S4 did not change f c (Fig. 4). In case of AEC mixtures, the problem expands to the effect of AEA. The use of AEA practically did not cause consistency changes of the SN1-SN4 mixtures in relation to the S1-S4 mixes. At a constant dose of AEA, the Vp in the mixes decreased with the SP content (Vp = 4.66% -SN1, 3.61% -SN2, 3.95% -SN3, 3.66% -SN4). In relation to the NAEC with the same SP dose, Vp content in SN1 and SN2 increased by 3.1 and 2.9%, while in SN3 mix increased by 2.6% and in SN4 by only 1.3%. The porosity structure also changed. As SP content increased, α and A 300 decreased, L increased, which indicates an increase in the content of large pores (Nowak-Michta 2015). The obtained results Vp, A, α , A 300 and L confirm the decrease in the effectiveness of AEA as the SP content increases (liquefaction of the mixture). AEA, by AE the mixture, causes a slight I D drop. In relation to NAEC with consistency S1, the I D fall is 0.83%, with the consistency of S2 - 3.47%, S3 - 2.17% and S4 - 1.66%. These compaction changes were confirmed by strength drop (  f c ), which decreases along with the increase in SP (liquefaction) (Fig. 4). As the content of SP increased, the compressive strength of AEC increased by 1, 7 and 13% respectively. The increase in air content in SN1-SN4 AEC mixtures in relation to NAEC mixes S1-S4 was 3.1, 2.9, 2.6 and 1.3% respectively and in case of  f c was equal to 5, 17, 12 and 6%. Converting to 1% of air, strength falls  f c = 1.6, 6.5, 4.6 and 4.6%. The obtained results for concretes SN2, SN3 and SN4 confirm the literature data (ACI 201.2R-01 2001, ACI Education Bulletin E4-03 2003, Du and Folliard 2005, Fagerlund 1997, Łukowski 2016, Neville 2012, Pigeon et al. 1996, Ramachandran 2001), which state that 1% of the introduced air causes a 5.5% drop in strength. However, the decrease obtained for SN1 concrete is significantly different from the literature data. Moreover, assuming S1 concrete as a comparison, only AE of SN1 and SN2 concretes resulted in strength decrease by 5 and 4%, while in SN3 and SN4 concretes strength increase by 2 and 8%.