Fire behaviour of plastic bottle ecobricks as an infill building material

Sander, Zara Rose (2022-04)

Thesis (MEng)--Stellenbosch University, 2022.

Thesis

ENGLISH ABSTRACT: A global increased awareness of plastic pollution, and the consequences of not addressing said problem, has led to increased interest and adoption of ecobricks as a building material. Ecobricks consist of any size plastic beverage bottle, densely filled with dry, non-recyclable plastic. As a result, places such as schools, shops and crèches around the world are collecting them and using them as an infill material in the construction of private and municipal projects. Construction projects incorporating ecobricks involve placing the plastic bricks inside a timber or reinforced concrete frame. The frame is sometimes covered with steel mesh (“chicken wire”) and plastered with various plaster-mixes. Ecobrick structures have gained popularity, with over 200 schools in Guatemala having been built using ecobricks. With plastics being highly flammable, it is important that the construction and fire engineering industries understand how they may perform when exposed to fire. The problem this thesis aims to answer is: how do ecobrick walls behave when exposed to fire, and how can they be built to ensure that they are safe? As construction using ecobricks is relatively new, minimal research has been done regarding fire safety. Two of the most common methods for constructing homes out of ecobricks were identified. One consists of laying ecobricks horizontally between cob (a clay-straw-sand-mortar mix). The alternative was to stack them vertically and encase them with a mesh and plaster. In this work, various plaster systems were tested, including, (a) traditional cement-sand mortar, (b) lime mortar, and (c) cob. This thesis investigates the placement of bottles, the application of plaster, and the use of mesh layers in relation to the thermal performance of ecobricks in a standard fire test. Six wall samples were built to represent the two different construction methods and three different plasters. The samples were tested in a large-scale furnace where the temperatures were measured through the cross-section of each wall. The temperatures were then compared against 2D thermal modelled wall samples to understand the thermal behaviour of the plaster and ecobricks. The plaster of each wall sample proved to be critical in the fire behaviour of the samples. The most favourable ecobrick and plaster combination, a cob plaster of 40 mm on the horizontal ecobrick wall sample, was able to achieve a one-hour fire rating, where the ecobricks did not melt or ignite. Samples tested with a vertical ecobrick and cement mortar experienced severe flaming and failed after 56 minutes, with some samples failing significantly faster. The lime plaster delaminated early on resulting in rapid failure. Preliminary guidelines for ensuring suitable fire behaviour are presented.

AFRIKAANSE OPSOMMING: n Wêreldwye toenemende bewustheid van plastiekbesoedeling en die gevolge rakende die feit dat die probleem nie aangespreek word nie, het gelei tot toenemende belangstelling en die gebruik van “ecobricks” vir boumateriaal. “Ecobricks” bestaan uit enige grootte plastiekbottels, dig gevul met droë, nie-herwinbare plastiek. As gevolg hiervan, versamel plekke soos skole, winkels en kleuterskole regoor die wêreld en gebruik dit as 'n aanvullingsmateriaal vir die bou van private en munisipale projekte. Bouprojekte wat “ecobricks” insluit, behels die plaas van die plastiekstene in 'n raam van hout of gewapende beton. Die raam is soms bedek met staalgaas ("hoenderdraad") en met verskillende pleister mengsels gepleister. “Ecobrick” strukture se gewildheid neem toe. Meer as 200 skole in Guatemala is reeds met aanvulling van “ecobricks” gebou. Omdat plastiek hoogs ontvlambaar is, is dit belangrik dat die konstruksie- en brandingenieursbedrywe verstaan hoe dit presteer as dit aan vuur blootgestel word. Die probleem wat hierdie proefskrif wil beantwoord, is: hoe “ecobrick” mure reageer as hulle aan vuur blootgestel word, en hoe dit veilig in bouprojekte gebruik kan word. Aangesien konstruksie met behulp van “ecobricks” relatief nuut is, is daar nog minimale navorsing gedoen oor brandveiligheid. Twee van die mees algemene metodes om huise uit “ecobricks” te bou, is reeds geïdentifiseer. Die een bestaan daaruit om “ecobricks” horisontaal tussen die sand-klei mengsel te lê ('n mengsel van klei-strooi-sand-mortier). Die alternatief is om dit vertikaal te stapel en dit met 'n gaas en gips te omhul. In hierdie projek is verskillende gipsstelsels getoets, waaronder (a) tradisionele sement-sandpleister, (b) kalkpleister en (c) sand-klei pleister. Hierdie tesis ondersoek die plasing van ‘ecobricks’, die aanbring van gips en die gebruik van gaaslae in verhouding met die termiese reaksie van “ecobricks” in 'n standaard vuurtoets. Ses toets mure is gebou om die twee verskillende konstruksiemetodes en drie verskillende pleistersoorte te ondersoek. Alle monsters is getoets in 'n groot toetsoond waarin die temperature in die deursnit van elke muur gemeet is. Die temperature is daarna vergelyk met 2D termiese gemodelleerde muurmonsters om die termiese reaksie van die gips en “ecobricks” te verstaan. Die gips van elke muurmonster was van kritieke belang om die reaksie van die monsters in ‘n brand te meet. Die beste kombinasie van “ecobricks” en ‘n pleisterlaag van 40 mm op die horisontale monster van die ecobrick-muur, kon 'n vuurklas (vuurweerstand) van een-uur behaal, waartydens die “ecobricks” nie gesmelt of ontvlam het nie. Monsters wat met 'n vertikale “ecobrick” en sementpleister getoets is, het erg ontvlam en het na 56 minute misluk. Die monsters het aansienlik vinniger misluk. Die kalkpleister het vroeg reeds begin delamineer, wat 'n vroeë mislukking tot gevolg gehad het. Voorlopige riglyne vir die versekering van geskikte brandgedrag word aangebied.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/124637
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