Partial replacement of coarse aggregate in portland cement concrete with Expanded Polystyrene Thermocol (EPT)

Abstract

Normally, non-biodegradable solid waste material produced in South Africa is disposed off through landfilling, intriguingly, the country has limited landfill space and a high demand for affordable solid waste material for use in construction. The demand for affordable material in the construction industry suggest that there is a need to consider the reuse of solid waste materials. This research aimed to evolve lightweight concrete by partially replacing coarse aggregate with Expanded Polystyrene Thermocol (EPT), hence reducing the amount of EPT that goes to landfills while producing concrete with enhanced properties. In this study, EPT was used to partially replace granite aggregate at varying levels: 0, 5, 10, 15, 20, 25, and 50 % by volume of aggregate. The water to cement ratio adopted was 0.58 and the specimens were cured for 7 and 28 days before testing. The effect of EPT on workability, compressive strength, and flexural strength of concrete was determined. Results showed that incorporation of EPT in concrete reduces the compressive and the flexural strength but increases the workability when compared to the control mix (0% EPT replacement). It was observed that when the percentage of EPT is higher, the compressive and flexural strengths were lower with corresponding improvement in workability. The average compressive strength and flexural strength of 50% replacement was 15.43 and 2.22 MPa, respectively, after 28 days, while that for control mix was 38.63 and 3.78 MPa, respectively, a strength reduction of approximately 40%. The heat conductivity at 50% EPT replacement reduced by 34% from normal concrete. Overall, the results show that one way to dispose EPT is to use it in concrete. It is therefore recommended that it is possible to replace 25% of coarse aggregate by EPT for structural concrete while higher percentage replacement can be deemed for non-structural applications.

Ngenxa yendawo elinganiselwe yokulahla imfucumfucu eNingizimu Afrika yokulahla imfucuza engaboli kanye nesidingo esikhulu sezinto zokwakha ezithengekayo, kunesidingo esinamandla sokuphinda kusetshenziswe imfucuza eqinile embonini yezokwakha. Lezi zinhloso zocwaningo ziveza ukhonkolo ongasindi ngokufaka ingxenye ehlanganisiwe ye-Expanded Polystyrene Thermocol (EPT), ngaleyo ndlela kwehliswe inani le-EPT eliya ezindaweni zokulahla imfucumfucu futhi ngesikhathi esifanayo kukhiqizwe ukhonkolo onezinto ezithuthukisiwe. Kulolu cwaningo, i-EPT yasetshenziselwa ukufaka ingxenye ye-granite aggregate emazingeni ahlukahlukene: 0, 5, 10, 15, 20, 25 kanye no-50 % ngesisindo, ngokulandelana. Isilinganiso sikasimende samanzi esamukelwe singu-0.58 kanti izibonelo zelashwa izinsuku eziyi-7 nezingama-28 ngaphambi kokuhlolwa. Umphumela we-EPT ekusebenzeni, amandla okucindezela kanye namandla okuguquguquka kwekhonkrithi kwanqunywa. Ucwaningo lubonise ukuthi ukufakwa kwe-EPT kukhonkolo kunciphisa ukucindezela namandla okuguquguqukayo kodwa kwandisa ukusebenza uma kuqhathaniswa nokuxuba kokulawula (i-0% EPT esikhundleni). Kwaphawulwa ukuthi amaphesenti aphezulu e-EPT, aphansi amandla okucindezela nokuguquguquka nokuthuthukiswa okuhambisanayo ekusebenzeni. Amandla acindezelayo amaphakathi namandla aguquguqukayo we-50 % esikhundleni atholwe angu-15.43 no-2.22 MPa ngokulandelana ngemva kwezinsuku ezingu-28, kuyilapho leyo yokuxuba kokulawula ingu-38.63 no-3.78 MPa ngokulandelanayo, ukuncipha kwamandla cishe ku-40%. I-conductivity yokushisa ku-50% EPT esikhundleni sehliswe ngo-34% kusuka kukhonkolo evamile. Ngenhloso yokusebenzisa i-EPT kukhonkolo njengendlela yokulahla futhi isenokhonkolo onezinto ezamukelekayo, ngakho-ke kunconywa ukuthi kuthathelwe indawo u-25 % wesamba esimahhadla nge-EPT ukuze uthole ukhonkolo wesakhiwo kuyilapho ukushintshwa kwamaphesenti aphezulu kungathathwa njengezinhlelo zokusebenza ezingezona ezesakhiwo.