Influence of natural zeolite and crushed brick on properties of lime mortars for restoration of historical buildings

Током XX века сазнања о своjствима, начинима справљања и могућностима примене кречних малтера су у великоj мери изгубљена. Ипак, током последњих тридесетак година, ови материjали се користе у санациjама и рестаурациjама историjских обjеката, како због компатибилности са постоjећим материjалима коришћеним за зидање и облагање, тако и због повољних физичко-механичких своjстава. За потребе ове дисертациjе изабрани су локално доступни компонентни материjали, у циљу справљања малтера компатибилних са кречним малтерима за малтерисање, коришћеним на простору Србиjе до средине XIX века. У свим малтерима испитиваним у склопу експерименталног рада као везиво jе коришћено кречно тесто одлежало 6 месеци и речни песак "дунавац", у две различите фракциjе: крупниjи (0/4 mm) и ситниjи (0/0,5 mm). У првом делу експеримента испитиване су две групе малтера: малтери у коjима jе креч делимично замењен природним зеолитом и малтери у коjима jе речни песак делимично или потпуно замењен дробљеном опеком. Ове врсте малтера справљане су за два односа креча и агрегата, 1:3 и 1:1 (запремински), коришћењем два начина неге. На укупно 19 мешавина су вршена испитивања у свежем и очврслом стању при различитим старостима (пре свега хидрофизичка, микроструктурна и механичка своjства). У другом делу експеримента на одабраним малтерима са додатком зеолита, нанетим на подлогу од природног камена, користећи иновативну методу припреме узорака, извршена су испитивања траjности (отпорности на деjство мраза и отпорности на деjство растворљивих соли). Показано jе да оба коришћена додатка, када су малтери неговани у влажноj средини, утичу на повећање чврстоће при притиску, укупне порозности и коефициjента капиларног упиjања и доводе до промена у микроструктури кречних малтера. Показано jе да jе предложени начин формирања композитних узорака адекватан за извођење испитивања траjности ових материjала.In the course of XX century, the knowledge on the properties, preparation methods and the possibilities for the application of lime mortars has been lost to a large degree. However, during the last three decades these materials have been used in the reparations and restorations of historical buildings, both for their compatibility with the existing mortars used for building and rendering, and for their favorable physico-mechanical properties. Locally available component materials were chosen for the purposes of this dissertation, with the aim of preparing the mortars compatible with lime mortars that were used for rendering on the territory of Serbia until the first half of XIX century. The lime putty, aged for six months, and river sand “Dunavac” were used as binders in two different fractions: with larger grains (0/4 mm) and with smaller grains (0-0,5 mm) in all the investigated mortars examined within the experimental part of work. In the first part of the experiment were investigated two groups of mortars: the mortars in which the lime was partially replaced with natural zeolite and the mortars in which the river sand was partially or completely replaced with crushed brick. These mortar types were prepared for two lime/aggregate ratios, 1:3 and 1:1 (volume), using two types of care. Investigations were performed on 19 mixtures in total, in fresh and hardened states, at different ages (mainly hydrophysical, microstructural and mechanical properties). In the second part of the experiment durability tests (resistance to the effects of frost and soluble salts) were performed. It has been shown that both additions that were used, when the mortars were cured in the humid environment, affected the strength increase with the pressure increase, total porosity and the coefficient of capilary absorption. Both additions induced changes in the lime mortars microstructure. It was concluded that the suggested method of preparation of composite samples was adequate for performance of investigations of the durability of these materials

FORMING A CORRELATION AMONG THE PROPERTIES OF FRESH SELF-COMPACTING CONCRETE USING FUZZY LEAST SQUARES MODEL

The research presented in this paper was motivated by two problems regarding the properties of fresh self-compacting concrete (SCC). The first problem is that mixture properties can vary owing to different factors (composition, materials, ambient, etc.) and the second problem is that there is usually a restricted group of experimental results. Because of the importance of the properties of fresh SCC mixtures, different tests for determining its passing and filling ability, as well as segregation resistance, have been developed. In this paper, results from V-funnel and slump flow tests conducted on seven different concrete mixtures are presented. As a correlation between the measurements of V-funnel period tv and the slump flow period t500 is usually strong, in this paper, it was expanded using approximate-distance fuzzy least squares method. The goal was to perceive the possible range of these properties and, when applicable, to reduce the number of tests necessary during the production of SCC

Solidified waste water treated sludge as partial replacement of cement in concete composites

In this research, tests of mortar and porous concrete made with solidified waste water treatment sludge (SWWTS) used in two forms as a partial replacement of cement were carried out. SWWTS mainly consisted out of CaCO3 and Ca(OH)2, having no pozzolanic properties. For this reason, it was used both, as produced, and modified by adding Al2O3 and Mg3Si4O10(OH)2 in certain percentages. One mortar type and two types of porous concrete were tested. For each of the three products two mixtures were prepared: the reference mixture and the mixture made with 30% replacement of cement, while the other components remained the same. Based on the given comparative analysis, conclusions were drawn regarding the structure of porous concrete slabs, which refer to individual analyzed properties, but also to the possibility of applying energy-efficient materials. The obtained results point to the conclusion that the use of SWWTS reduces the values of almost all tested properties of porous concrete (flexural and compressive strength, pull-off strength, abrasion resistance), but also that the modification of SWWTS led to a smaller difference in the results of the samples made with 30% of cement replacement and the reference samples. Although, the use of SWWTS led to the reduction of mechancal properties of concretes, the most important benefit is development of possible way for reuse of this waste material and avoid its disposal in the landfills

Correlation Between Dynamic Modulus of Elasticity and Compressive Strength for Self-Compacting Mortars

Application of non-destructive testing methods in defining the mechanical properties of mortar and concrete is continually developing. Self-compacting or self-leveling mortars are already widely applied in construction of new structures. As self-compacting mortars are finding their place in rehabilitation and repair of reinforced concrete structures, it is of high importance to design mixtures with compressive strength and modulus of elasticity compatible with existing concrete. Ten mortar series with variation of component materials (fly ash, recycled concrete aggregate, crushed brick aggregate and crushed brick filler) were the subject of following tests: resonant frequency, ultrasonic pulse velocity and compressive strength of mortar. Dynamic modulus of elasticity was calculated using the first two methods mentioned. Results from resonant frequency measurements were then used for calculating compressive strength of the mixtures through different models developed for ordinary concrete and available in the literature. It was shown that the model proposed by Gardner is closest to describing the behavior of mixtures with different component materials, but would need some corrections in order to be used for these purposes

Forming a correlation among the properties of fresh self-compacting concrete using fuzzy least squares model

The research presented in this paper was motivated by two problems regarding the properties of fresh self-compacting concrete (SCC). The first problem is that mixture properties can vary owing to different factors (composition, materials, ambient, etc.) and the second problem is that there is usually a restricted group of experimental results. Because of the importance of the properties of fresh SCC mixtures, different tests for determining its passing and filling ability, as well as segregation resistance, have been developed. In this paper, results from V-funnel and slump flow tests conducted on seven different concrete mixtures are presented. As a correlation between the measurements of V-funnel period t(v) and the slump flow period t(500) is usually strong, in this paper, it was expanded using approximate-distance fuzzy least squares method. The goal was to perceive the possible range of these properties and, when applicable, to reduce the number of tests necessary during the production of SCC

Ispitivanje svojstava materijala i sistema za unutrašnje oblaganje kupole Spomen hrama svetog Save

Prema projektu, za unutrašnje oblaganje kupole Spomen hrama svetog Save predviđena je izrada mozaika. U radu su prikazani rezultati ispitivanja osnovnih fizičko-mehaničkih svojstava materijala, odabranih kao podloga za postavljanje mozaika: dve vrste reparaturnih maltera i jedna vrsta lepka proizvođača „Mapei“, Italija. Posebna pažnja posvećena je ispitivanjima adhezije predmetnih materijala za betonsku podlogu, korišćenjem „Pull-off“ metode. Ispitivanja su vršena, kako u laboratoriji, tako i na probnim poljima izvedenim unutar kupole hrama. Osim na pojedinačnim materijalima, ispitivanja su vršena i na višeslojnim sistemima odabranim od strane Projektanta, u svemu prema propisanim tehničkim uslovima

Physical, mechanical and durability aspects of lime-based coatings with addition of natural zeolite

Lime-based renders were usually placed in several layers, each of them having specific role and composition. In this paper, physical and mechanical properties of lime mortars for the final layer (coating) at the age of 90 and 180 days were presented. Durability aspect of the tested mortars was considered through testing of their behavior in the presence of the soluble salts. Four mortar mixtures were tested (one reference mortar and three mortars with partial replacement of lime with natural zeolite). For all mortars tested it can be seen that there was no improvement in strength between two tested ages. Mortar with 30% of lime replaced with zeolite reached higher value of compressive strength and almost the same value of capillary water coefficient as reference mortar. Vapor permeability grew with the increase of the natural zeolite content. Mortars showed good resistivity to the presence of sodium-chloride and developed cracks and loss of compressive strength when exposed to the solution of sodium-sulfate

Properties of SCC Mixtures with Coarse Recycled Aggregate

Paper presents the results of physical and mechanical testing of concrete mixtures prepared with recycled concrete aggregate. Four series of Self-Compacting Concrete (SCC) were made, with the use of recycled concrete aggregate (RCA), as a substitute for both natural coarse aggregate fractions. These series were designed using the Two Stage Mixing Approach (TSMA), and the properties of the obtained concrete mixtures in fresh and hardened state were recorded. Flowability of fresh mix was determined using slump flow test, while V-funnel and L-box tests were also performed. Compressive strength and also flexural, splitting and bond (pull-off) strength were determined. All of the mixtures showed favourable properties, proving the possibility of the recycled concrete aggregate use for production of worthy SCC

Primena in-situ metoda ispitivanja u cilju sanacije betonskih konstrukcija

U radu je prikazana ocena stanja armiranobetonske (AB) konstrikcije primenom nedestruktivnih i destruktivnih in-situ metoda ispitivanja. Analziriana je zavisnost rezultata dobijenih primenom pomenutih metoda u skladu sa važećom tehničkom regulativom. Za AB grede i stubove kod kojih nije ostvarena projektovana marka betona dati su primeri sprovedenih sanacionih mera. U prikazanim primerima detaljno su opisani svi relevantni aspekti praktične pirmene sprovedenih sanacionih mera karbonskim trakama i betoniranjem