Hydration of newly synthesized belite cement with mineral additives

[J. Nešković]

226 listova

Rudarsko inženjerstvo - Mineralne i reciklažne tehnologije, Inženjerstvo materijala / Mining engineering - Mineral and recycling technologies, Materials engineering

Eksperimentalna istraživanja koja su izvedena u okviru ove doktorske disertacije pod nazivom „Hidratacija novosintetizovanog belitnog cementa sa mineralnim dodacima” imala su za cilj pripremu novih vrsta alitnih i belitnih maltera koji u svom sastavu sadrže pepeo i zguru kao industrijske otpadne mineralne dodatke. Nakon veštački izazvanih pukotina na njima, sprovedena su lečenja na tri načina: 1) produženom hidratacijom u uslovima česmenske i Dunavske vode 2) potapanjem u suspenziju lekovitog agensa (10 mas% suspenzije novosintetizovanog belita u destilovanoj vodi) 3) bio-indukovanim zaceljenjem spoljašnjom aplikacijom lekovitog agensa (suspenzija bakterije Sporosarcina pasteurii DSM 33) u kontrolisanim uslovima sterilne demineralizovane i Dunavske vode Analizom dobijenih rezultata opšežnih eksperimenata izvedeni su sledeći zaključci po fazama eksperimentalnog rada: Mineralni dodaci, pepeo i zgura, koji su korišćeni u ispitivanjima mogu uspešno da se primenjuju kao dodatak cementu nakon prethodne mikronizacije, jer po svim ispitanim fizičko-hemijskim osobinama ispunjavaju uslove koje propisuju standardi iz ove oblasti. Analizom čvrstoća na pritisak alitnih maltera, utvrđeno je da je količina od 10 mas% mineralnih dodataka (pepela/zgure) optimalna za naredna ispitivanja, jer su dobijene vrednosti bile bliske vrednostima za CEM I koja je u ovim ispitivanjima iznosila 59,33 MPa nakon 28 dana. Tačnije, dodatkom pepela u količini od 10 mas% vrednost čvrstoće na pritisak iznosila je 62,5 MPa, a dodatkom zgure u istom masenom udelu čvrstoća na pritisak je iznosila 58,61 MPa. Dodatkom belita (1, 5 i 10 mas%) u odabrane sisteme alitnih maltera (sa 10 mas% mineralnog dodatka) vrednosti čvrstoća na pritisak su bile niže, a pokazale su trend porasta sa povećanjem masenog udela belita za sve sisteme sa mineralnim dodacima. Tako je sistem sa pepelom i belitom (oba po 10 mas%) imao najveću vrednost čvrstoće na pritisak od 61,62 MPa, a sistem sa zgurom i belitom (oba po 10 mas%) imao vrednost čvrstoće od 53,72 MPa. Izuzetak trenda je imao sistem CEM I sa belitom bez mineralnog dodatka gde je vrednost opadala sa povećanjem masenog udela belita. Na osnovu ovih zaključaka za dalja istraživanja bio-indukovanog zaceljenja je usvojeno maseno učešće belita od 10 mas%. Produženom hidratacijom nakon 240 dana u uslovima negovanja u česmenskoj i Dunavskoj vodi ovim istraživanjem je dokazano da je moguće aktivirati mehanizam autogenog zaceljenja. Nakon perioda produžene hidratacije od 240 dana zaceljenje u sistemu CEM I (alitni sistem) je bilo potpuno za početne širine pukotine od 0,315 mm negovanih u Dunavskoj vodi, a 0,21 mm za početne širine pukotine uzoraka negovanih u česmenskoj vodi. Za alitne sisteme sa mineralnim dodacima, zaceljenja uzoraka negovanih u česmenskoj vodi su pokazala manju efikasnost u odnosu na zaceljenja na uzorcima negovanih u Dunavskoj vodi. Alitni sistem sa 10 mas% pepela je pokazao zaceljenje od 42,98 % u uslovima negovanja u Dunavskoj vodi za početnu širinu pukotine od 0,235 mm. Alitni sistem sa dodatkom zgure od 15 mas% i početnom širinom pukotine od 0,621 mm zacelio je 37,84 % takođe u uslovima negovanja u Dunavskoj vodi. Nakon perioda produžene hidratacije od 240 dana belitni sistemi sa 1 mas% belita bez mineralnog dodatka mogli su u potpunosti da zacele u uslovima negovanja u Dunavskoj vodi za početnu širinu pukotine od 0,479 mm. Kod belitnih sistema (5 mas% i 10 mas%) sa zgurom efikasnost zaceljenja je bila ista i u uslovima negovanja u česmenskoj i u Dunavskoj vodi. Širine pukotina od 0,456 mm zacelile su do 37,92 % pri masenom udelu belita od 5 mas%. Sistem sa pepelom i belitom od 10 mas% u uslovima negovanja u česmenskoj vodi je zacelio i do 75,66 % za početne širine pukotina od 0,229 mm, dok su početne širine pukotina manjih dimenzija od 0,09 mm potpuno zacelile. Eksperimentom potapanja u suspenziju belita (10 mas% belita u destilovanoj vodi) kao lekovitog agensa je takođe dokazano da je proces zaceljenja moguć za posmatrani period od 28 i 150 dana. Za razliku od autogenog zaceljenja produženom hidratacijom, i bio- indukovanog zaceljenja bakterijskom kulturom, zaceljenje potapanjem u suspenziju lekovitog agensa je dalo bolju efikasnost za sve odabrane sisteme. Ova metoda se u ovim istraživanjima pokazala kao najdelotvornija. Kod sistema CEM I sa belitom bez mineralnog dodatka, suspenzija je najbolji učinak ostvarila pri masenom učešću belita od 1 mas% gde je zaceljenje pukotine širine od 0,445 mm bilo 52,81 % nakon 28 dana posmatranog perioda. Kod sistema CEM I sa belitom i dodatkom pepela najbolji učinak je takođe bio u sistemu sa 1 mas% belita, gde je ostvarena efikasnost od 48,1 % sa početnom širinom pukotine od 0,21 mm već nakon 14 dana delovanja suspenzije. Sistem CEM I i belit sa zgurom (5 mas% belita) je zacelio u suspenziji belita za 55,36% pri početnoj širini pukotine od 0,168 mm ali za nešto duži period delovanja suspenzije od 150 dana. Za razliku od standardnih dimenzija uzoraka, kod laboratorijskih uzoraka gde su pukotine bile površinske i nisu prelaze 0,5 mm dubine, zaceljenje je bilo potpuno kod svih sistema već nakon 7 dana delovanja suspenzije. Kod bio-indukovanog zaceljenja spoljašnjom aplikacijom suspenzije bakterije S. pasteurii DSM 33 najbolju efikasnost su ostvarili alitni sistem sa 10 mas% zgure i belitni sistem čistog belita nakon 7 dana negovanja u kontrolisanim uslovima sa bakterijskom kulturom u sterilnoj demineralizovanoj i Dunavskoj vodi. Efikasnost koja je ostvarena u sistemu CEM I sa 10 mas% zgure je iznosila 28,12 % za početne širine pukotina od 0,504 mm dok je efikasnost kod sistema čistog belita iznosila 36,98 % za početne širine pukotina od 0,789 mm. Nakon završenih istraživanja bio-indukovanog zaceljenja izvršena je klasifikacija svih snimljenih slika sistema CEM I sa 10 mas% zgure koji je pored sistema čistog belita, sistem sa najuspešnijim rezultatima. Konačna tačnost klasifikacije korišćenjem programskog jezika MATLAB 2023A i podprograma ResNet 50, kao modela dubokog učenja je iznosila 91,55% što je potvrđeno i računskim putem. Uzimajući u obzir sve dobijene rezultate u okviru doktorske disertacije moguće je konstatovati nekoliko značajnih naučnih dostignuća u odnosu na postojeće publikacije, kako na nacionalnom tako i na međunarodnom nivou. Ove novine se pre svega ogledaju u činjenici da je proces samozaceljena praćen u prisustvu bakterijske kulture na standardnim cementinim malterima sa mineralnim dodacima, kao i na belitnim malterima koji u svom sastavu takođe imaju mineralne dodatke. Naime, u dostupnoj naučnoj literaturi istraživači su se uglavnom bavili ili uticajem mineralnih dodataka na proces samozaceljenja, ili uticajem bakterijskih kultura na standardnim cementnim malterima i betonima. Takođe, značajnu novinu predstavlja i negovanje maltera u suspenziji novosintetizovanog belita, a naročito negovanje maltera tokom procesa bio-indukovanog samozaceljenja u Dunavskoj vodi, što je značajan korak u prelasku naučnih rezultata sa laboratorijskog nivoa na realne sisteme. Na kraju, rezultati imaju izraziti multidisciplinarni karakter jer iako veštačke neuronske mreže imaju široku primenu u mnogim oblastima društvenih i tehničkih nauka još uvek su u fazi razvoja u oblasti primene praćenja efikasnosti bio-indukovanog zaceljenja cementnih maltera.

The experimental research carried out as part of this doctoral dissertation entitled "Hydration of newly synthesized belite cement with mineral additives" aimed to prepare new types of alite and belite mortars that contain fly ash and blast furnace slag as industrial waste mineral additives. After artificially induced cracks, they were treated in three ways: 1) prolonged hydration in the conditions of tap water and Danube water, 2) by immersion in a suspension of the healing agent (10 mass% suspension of newly synthesized belite in distilled water) and 3) bio-induced healing by application of external healing agent, a suspension of the bacteria Sporosarcina pasteurii DSM 33 in controlled conditions of sterile demineralized and Danube water. By analyzing the results of general experiments, the following conclusions were drawn according to the phases of the experimental work: Mineral additives, fly ash and blast furnace slag, which were used in the experiments, can be successfully applied as an additive to cement after previous micronization, because according to all the physical and chemical properties tested, they meet the conditions prescribed by the standards in this field. By analyzing the compressive strength of alite mortars, it was determined that the amount of 10 mass% of mineral additives (ash/slag) was optimal for subsequent tests, because the obtained values were close to the values for CEM I, which in these tests was 59.33 MPa after 28 of the day. More precisely, with the addition of ash in the amount of 10% by mass, the compressive strength value was 62.5 MPa, and with the addition of slag in the same mass fraction, the compressive strength was 58.61 MPa. With the addition of belite (1, 5 and 10 mass%) to the selected alite mortar systems (with 10 mass% mineral additive), the compressive strength values were lower, and they showed an increasing trend with the increase in the mass fraction of belite for all systems with mineral additives. Thus, the system with ash and belite (both 10 mass%) had the highest compressive strength value of 61.62 MPa, and the system with slag and belite (both 10 mass%) had a strength value of 53.72 MPa. The exception to the trend was the CEM I system with belite without mineral addition, where the value decreased with increasing mass fraction of belite. On the basis of these conclusions, a mass participation of 10 mass% of white was adopted for further research on bio-induced healing. With extended hydration after 240 days in conditions of curing in tap water and Danube water, this research has proven that it is possible to activate the mechanism of autogenous healing. After a period of prolonged hydration of 240 days, the healing in the CEM I system (alite system) was complete for the initial crack widths of 0.315 mm treated in Danube water, and 0.21 mm for the initial crack widths of the samples treated in tap water. For alite systems with mineral additives, the healing of samples treated in tap water showed lower efficiency compared to the healing of samples treated in Danube water. The alite system with 10 mass% ash showed a healing of 42.98% under conditions of treatment in Danube water for initial crack widths of 0.235 mm. The alite system with the addition of slag of 15 mass% and the initial crack width of 0.621 mm healed 37.84 % also in the conditions of treatment in Danube water. After a period of prolonged hydration of 240 days, belite systems with 1 mass% belite without mineral addition could fully heal under conditions of curing in Danube water for initial crack widths of 0.479 mm. In the case of belite systems (5 mass% and 10 mass%) with slag, the healing efficiency was the same under conditions of maintenance in tap and Danube water. Crack widths of 0.456 mm healed up to 37.92% at a mass fraction of belite of 5 mass%. The system with ash and belite of 10 mass% under conditions of curing in tap water healed up to 75.66% for initial crack widths of 0.229 mm, while initial crack widths of smaller dimensions of 0.09 mm were completely healed. The experiment of immersion in belite suspension (10 mass% belite in distilled water) as a healing agent also proved that the healing process was possible for the observed period of 28 and 150 days. In contrast to autogenous healing by prolonged hydration, and bio- induced healing by bacterial culture, healing by immersion in a healing agent suspension gave better efficacy for all selected systems. This method proved to be the most effective in these studies. In the case of the CEM I system and belite without mineral addition, the suspension achieved the best performance with a mass percentage of belite of 1 mass%, where the healing of a crack with a width of 0.445 mm was 52.81% after 28 days of the observed period. In the CEM I system and belite with added ash, the best performance was also in the system with 1 mass% of belite, where an efficiency of 48.1% was achieved with an initial crack width of 0.21 mm already after 14 days of suspension action. The CEM I system and belite with slag (5 mass% belite) healed in the belite suspension by 55.36% at an initial crack width of 0.168 mm, but for a slightly longer suspension period of 150 days. In contrast to the standard dimensions of the samples, in laboratory samples where the cracks were superficial and did not exceed 0.5 mm in depth, healing was complete in all systems already after 7 days of suspension action. In bio-induced healing by external application of the S. pasteurii DSM 33 suspension, the best efficiency was achieved by the alite system with 10 mass% slag and the belite system of pure belite after 7 days in controlled conditions with bacterial culture in a sterile demineralized and Danube water. The efficiency achieved in the system with CEM I and 10 mass% slag was 28.12% for initial crack widths of 0.504 mm, while the efficiency of the system of pure belite was 36.98% for initial crack widths of 0.789 mm. After the bio-induced healing research was completed, a classification was made of all the recorded images of the CEM I system with 10 mass% slag, which, next to the pure belite system, is the system with the most successful results. The final classification accuracy using the MATLAB 2023A and the ResNet 50 as a deep learning model was 91.55%, which was also confirmed by calculation. Taking into account all of the obtained results within the doctoral dissertation, it is possible to state several significant scientific achievements in relation to existing publications both at the national and international level. This novelty is primarily reflected in the fact that the self-healing process was monitored in the presence of bacterial culture on standard cement mortars with mineral additives as well as on belite mortars that also have mineral additives in their composition. Namely, in the available scientific literature, researchers mainly dealt with either the influence of mineral additives on the self-healing process, or the influence of bacterial cultures on standard cement mortars and concretes. Also, a significant novelty is the curing of mortar in a suspension of newly synthesized belite, and especially the curing of mortar during the process of bio-induced self-healing in Danube water, which is a significant step in the transfer of scientific results from the laboratory level to real systems. In the end, the results have a distinct multidisciplinary character because although artificial neural networks are widely used in many areas of social and technical sciences, they are still in the development phase in the field of application of monitoring the effectiveness of bio- induced healing of cement mortars.

pepeo, zgura, samozaceljenje, suspenzija lekovitog agensa, suspenzija S. pasteurii DSM 33, Dunavska voda.

ash, slag, self-healing, healing agent, bacteria culture S. pasteurii DSM 33, Danube river water.

666.971.4:620.16(043.3)

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