The aim of this work was to study the influence of the type of activator on the formulation of modified fly ash based geopolymer mortars. Geopolymer and alkali-activated materials (AAM) were made from fly ashes derived from coal and biomass combustion in thermal power plants. Basic activators (NaOH, CaO, and Na2SiO3) were mixed with fly ashes in order to develop binding properties other than those resulting from the use of Portland cement. The results showed that the mortars with 5 mol/dm3 of NaOH and 100 g of Na2SiO3 (N5-S22) gave a greater compressive strength than other mixes. The compressive strengths of analyzed fly ash mortars with activators N5-S22 and N5-C10 (5 mol/dm3 NaOH and 10% CaO) varied from 14.3 MPa to 5.9 MPa. The better properties of alkali-activated mortars with regular fly ash were influenced by a larger amount of amorphous silica and alumina phases. Scanning electron microscopy and calorimetry analysis provided a better understanding of the observed mechanisms.

No abstract

No abstract

No abstract

Fre eze-thaw at tack is the ma in corro sion pro cess of con cre te in Poland. It is a pro gres si ve phe no menon in cre asing with the num ber of frost cyc les. Mo re over, in con nec tion with de -icing salt, the frost at tack is much stronger. On ly 50 years of du ra bi li ty of con crete is as su red by PN -EN 206:2014, but the PWR nuc le ar struc tu res li fe is exten ded to 80 and even 100 years. The re fo re the RCC -CW De sign and con struc tion ru les for ci vil works in PWR nuc le ar is lands [17] is mo re re stric ted. It is ba sed on French expe rien ce and tech ni cal me asu res that are de fi ned for dif fe rent frost expo su re classes (re qu ire ments for con cre te com po si tion and per for man ce). In ma ny co un tries, in clu ding Po land, the con di tions and experien ce (espe cial ly the test me thods and quali fi ca tion pro ce du res) are dif fe rent [6] so it is wor thy to pre sent the se re gu la tions. Freeze-thaw durability according to PN-EN 206:2014In PN -EN 206: 2014 if con cre te is exposed to si gni fi cant at tack by fre eze-thaw cyc les whilst wet, the envi ron men tal action is clas si fied as XF1 to XF4 expo sure clas ses for risk of fre eze-thaw at tack:• XF1 Moderate water saturation, without de-icing agent, e.g. vertical concrete surfaces exposed to rain and freezing;• XF2 Mo de ra te wa ter sa tu ra tion, with de -icing agent, e.g. ver ti cal con crete sur fa ces of ro ad struc tu res expo sed to fre ezing and air bor ne de -icing agents;• XF3 High water saturation, without de-icing agent, e.g. horizontal concrete surfaces exposed to rain and freezing;• XF4 High water saturation, with de-icing agent or sea water, e.g. road and bridge decks exposed to de-icing agents; concrete surfaces exposed to direct spray containing de-icing agents and freezing; splash zones of marine structures exposed to freezing.Due to this clas si fi ca tion the re commen ded li mi ting va lu es for com po si tion and pro per ties of con cre te are spe ci fied in An nex F. In RCC -CW the se va lu es are mo re re stric ted: ■ for XF2: w/c ratio decreased from 0,55 to 0,50 and minimum strength class increased from C25/30 to C30/37; ■ for XF4: minimum strength class increased from C30/37 to C35/45.Additional requirements are given in PN-EN 206:2014 as well:• for all XF clas ses: an ag gre gate sho uld be in ac cor dan ce with PN -EN 12620+A1:2010 with suf fi cient fre eze/thaw re si stan ce;• for XF2, XF3 and XF4: mi ni mum air con tent is li mi ted to 4,0% and where the con cre te is not air en tra ined, the per for man ce of con cre te sho uld be tested ac cor ding to an ap pro pria te test me thod in com pa ri son with a con cre te for which fre eze-thaw re si stan ce for the re le vant expo su re class is pro ven.In the bibliography of PN-EN 206:2014 there are two standards given for this purpose.In PKN -CEN/TS 12390-9:2007 [15] it is re com men ded the use of "slab test" (ba sed on the Swe dish stan dard SS 13 72 44 [18], so --cal led Borås me thod) as a re fe ren ce. The other two me thods: on...