Material characterisation and response modelling of recycled concrete and masonry in pavements

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Stellenbosch : Stellenbosch University
ENGLISH ABSTRACT: The global quest for sustainability has intensified the requirement for waste recycling in a number of countries. Waste recycle includes Construction and Demolition Waste (CDW), which emanates from the demolition of buildings and other civil engineering structures. In Europe, the United States, China, and Australia, waste recycling has proven to be successful, both structurally and functionally. In particular, the consideration and /or use of CDW in pavement layers remain on the increase. However, in Southern Africa the use and/or application of CDW and its allied practice is limited; the abundant natural aggregates, the lack of knowledge and technical expertise besides the availability of suitable CDW remain the prominent reasons for its limited consideration. In this research, recycled material infers to Construction and Demolition Waste pertaining to Recycled Concrete and Masonry (RCM). The quality and the type of RCM vary from region to region and as a result, quality control measures aimed at limiting the inconsistency are usually required. Results revealed that secondary crushing influences the physical and mechanical behaviour of RCM aggregates; this information remains insightful in terms of material gradation, performance and viability. The compaction protocol followed and its findings revealed that the initial material grading lightly changed after compaction. However, the 10% FACT results showed that the RCM aggregates exhibit less degradation due to crushing when dry than when they are wet. It is eminent that compaction and/or densification are a cheaper method to improve the pavement layer structural capacity. However, this is reliant on material characteristics, quality, and type. With this cognisance, an experimental program in line with RCM aimed at assessing the mechanical behaviour was developed. The experimental variables include mix composition, mixing and compaction moisture as well as degree of compaction and/or compactive effort. In general, the laboratory evaluation and analysis of the results showed that the mix composition in addition to compaction moisture and the degree of compaction were influential to the obtained shear strength, resilient modulus and Poisson Ratio. Particularly, mix composition exhibited relatively higher influence on the resilient modulus while the compaction moisture effect on the Poisson Ratio dominated other investigated variables such as mix composition and the degree of compaction. Shear strength and resilient response results show that RCM exhibits significant shear strength due to its cohesion, and satisfactory resilient modulus. Pavement analysis and design using multi-layer linear-elastic model and transfer functions in pavement layers where RCM is used also revealed that this material could perform satisfactorily. It was deduced that RCM is a viable material type to consider in the construction of pavement layers that carry low to moderate levels of traffic.
AFRIKAANSE OPSOMMING: Die globale beweging na meer onderhoubare aktiwiteite het gelei tot die ʼn toename in vereistes met betrekking tot herwinning van rommel. Rommelherwinning sluit materiaal van bouwerke en ander siviele strukture in. In Europa, Amerika, China en Australië het die herwinning van afval materiaal tot groot sukses gelei. Spesifiek die gebruik van geselekteerde bourommel in padlae bleik om toe te neem. In Suid -Afrika word die materiaal net in enkele geïsoleerde gevalle gebruik as gevolg van die onderbreking van tegniese kennis met betrekking tot die toeganklikheid en bruikbaarheid van die materiaal. Ook, tans geniet die gebruik van gebreekte klip voorrang omdat die verbruiker glo dat daar nog baie van hierdie materiaal beskikbaar is. In hierdie navorsing verwys bourommel spesifiek na herwinde beton en boustene. Die “kwaliteit” van boustene in verskillende gebiede varieer en as ‘n gevolg moet kwaliteitskontroles toegepas word om hierdie te beperk. Resultate in diè navorsing het gewys dat sekondêre klipbreking/vergruising die fisiese en meganiese gedrag van “bourommel aggregaat” beïnvloed. Die 10% FACT (Fynstof Aggregaat Breekwaarde) resultate het ook gewys dat geselekteerde bourommel minder degradasie ondervind as dit droog is in vergelyking met nat materiaal. Goeie kompaksie van die tipe materiale word erken as een van die goedkoopste maniere om die gedrag daarvan in plaveisellae te verbeter. Dit is wel afhanklik van materiaal karakteristieke, kwaliteit en tipe materiaal. Hierdie faktore is ingesluit in die eksperimentele plan wat eienskappe soos mengsel komposisie, meng en kompaksie voginhoud sowel as graad van kompaksie insluit. Die resultate van die laboratorium analise het gewys dat die mengkomposisie, vog tydens kompaksie en graad van kompaksie ʼn invloed op die skuifsterkte, veerkragsmodulus en die Poisson verhouding het. Veral die mengkomposisie het ʼn merkwaardige invloed op die veerkragmodulus gehad, terwyl die voginhoud tydens kompaksie die grootste invloed op die Poissonverhouding gehad het. Die skuifsterkte (agv hoë kohesie) en veerkragsmodulus van geselekteerde bourommel dui aanvaarbare resultate vir die gebruik in paaie, spesifiek in padlae waar lae spanningsvlakke ondervind word,soos deur liniere elastiese berekeninge gewys is.
Thesis (MEng)--Stellenbosch University, 2014.
Construction and demolition debris, Recycling (Waste, etc.), Concrete and masonry -- Recycling, Pavements, Concrete, Dissertations -- Civil engineering, Compacting, UCTD