Pestud paekivisõelmete katsetamine TTK teedelaboris

Teekonstruktsioonide katseseadme kasutamine käesolevas uuringus aitas selgitada ja põhjendada paesõelmetega seonduvaid probleeme. Katse käigus tehtud järeldused aitasid anda vastuseid küsimustele, mis on takistanud paesõelmete kasutamist teedeehituses. Paesõelmed olid katsekonstruktsioonis pestud kujul ehk paeliivana, kus peenosis on materjalist eemaldatud. Pikaajalise vastupidamise kommenteerimine on katseoludes raske, kuigi tuli ikkagi välja, et tarindi sees olles paeliiv purunes. Muldkeha ülemises osas olnud paeliiv oli Geotehnika laboris tehtud terastikulise koostise määramise põhjal purunenud, mis tähendab, et pikaajaline vastupidamine paeliival on küsitav. Tunduvalt paremini pidas vastu paeliiva ja kvartsliiva segu, millest võeti samuti proovid ja tehti samad analüüsid, aga seal polnud purunemist praktiliselt olnudki. Mis kinnitab, et kvartsliivaga segatult võiks paeliiva teekonstruktsioonis kasutada. Siin rõhutatakse paeliiv, sest sealt on peenosised välja pestud. Külmutamiskatse käigus saadi jätkuvalt kinnitust sellele, et paeliiv on külmakartlik materjal, sest muldkeha ülemises osas hakkasid pinged muutuma suuremaks pärast sulamist. Enne külmutamiskatset ei näidanud need suuri pingeid. Lisaks kinnitasid andurid, mis olid 50/50 materjalisegust ehitatud dreenkihis, pingete tõusu pärast konstruktsiooni täielikku külmumist. Tegu oli niiskust täis materjali paisumisega, mis tekitas pingeandurites muutusi. Paeliiva kasutamine nii puhtalt kui ka kvartsliivaga segatult on ohtlik külmumispiirist ülevalpool. See võib tekitada teedel külmakerkeid. Katseseadme kasutamise käigus selgus, et pideva pikaajalise koormamise tõttu tõusid samuti konstruktsioonis pinged, mis tähendab, et katsetingimustes ei pea konstruktsioon sellisele koormusele vastu, vaid annab järgi. Siit tehti järeldus, et katseseadme kasutamisel on vaja läbi mõelda tsüklite tekitamine, seda oleks vaja teha läbimõeldumalt. Edaspidi ei tohiks tarindit nii pikalt järjest koormata, sest see võib tekitada eksitavaid järeldusi. Antud uuringu käigus saadi peale paesõelmeid puudutavat informatsiooni, ka taaskord õppida katseseadet veel paremini tundma ja kasutama selle võimalusi. Tulevastes katsetes saab kõik need küsimused ja kitsaskohad lahendatud, mis selle katse käigus katseseadme kohta õhku jäid. Edaspidi saab andmeid ja vaatluses saadud järeldusi kiiremini ja efektiivsemalt analüüsida.

The purpose of this investigation is to research about the use of mining residue in road construction. One of the main material in road construction in Estonia is limestone, what is used as primary goods to produce crushed stone. After getting crushed stone out of limestone, there is also side-product what is called limestone screenings. The amount of limestone screenings in quarries is remarkable and it is wise to find different possibilitys of implementing it. Currently are the limestone screenings considered as residue of crushed stone-producing process, but actually limestone screenings have been used widely in road construction earlier. Since the requirements of road projection and construction are getting more demanding, the limestone screenings are being forgotten as a potential road construction material. The reason why current road constructors, road projectors and developers would not dare to use limestone screenings, is associated with characteristics of the material. It is known that the durability of limestone screenings is questionable. Firstly the investigation focuses on finding an answer to a question, how durable can limestone screenings as a road construcion material be? Secondly the study deals with the problem of this materials ability to absorb water. Problem is caused by the fines content that bind itself with humidity. Is it possible to solve this problem and how? This research was carried out in the laboratory of Tallinns University of Applied Sciences. The laboratory has a testing device which helps to test road constructions. The device is basically a vehicles tire with the mass of 2.5 tons. The wheel is driven on the testing road to study durability of the road construction and to give as realistic conditions as possible. The testing process contained five different tests, within was studied different road constructions which were built out of sand of limestone (fines content removed) and silicia sand. The different mixtures of these sands were in the ratios of 30/70 (30% of silicia sand and 70% sand of limestone) and another 50/50. Notes being made during the tests are considered in this studies analytical chapters. Furthermore, there were tension sensors built in the construction and the information from these sensors is also analyzed in this investigation. Finally, a material sample was taken of the construction and it was sent to other laboratories for studing. The results have been analyzed in this study. After testing period, an analysis was carried out. The results of tests showed that the durability of limestones-sand is questionable, because the material samples confirmed that the construction breaks. Mixes which consisted silicia sand were more efficent. Sand of limestone mixed with silicia sand was not substantially broken, so it has resulted that using these mixtures in road constructions is reasonable and it helps to increase limestones-sand life expectancy. The studies also confirmed that the sand of limestone as a material does not bear cold well. In the so-called freezing test, the tension sensors showed that the tension increased, because the material dilated. After melting there were increased tensions in the construction. This phenomenon was noted due to the excessive humidity. The conclusions of this study point out that it is not reasonable to use sand of limestone in road construction above the freezing level. Its expansion may damage the construction. Current investigation confirmed the knowledge about problems with sand of limestone in use of road construction material and showed different causes why that is. Also, some solutions are offered in this research to eliminate some of the problems. This investigation could be an additional research to road projectors, road constructors and developers – it gives ideas how to use limestone screenings wisely and rationally.