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[Abstract:] Concrete is the most widely used construction material in the world; as such, the best way to promote a more sustainable construction industry is to improve the environmental performance of this material. Since cement production is the main source of the high environmental impact of concrete, due to the high calcination temperature that clinker requires, replacing this binder with recycled cement would allow for the establishment of a new concrete design with a much lower ecological footprint. This research intends to analyse the mechanical performance of mortars with recycled cement and fly ash. Mixes with two replacement ratios of recycled cement (5% and 10%) were studied separately or in combination with fly ash (10% and 20%). An exhaustive experimental programme was designed to assess the variation in air content, density, compressive and flexural strengths, modulus of elasticity, and ultrasonic pulse velocity. The results suggest that the simultaneous use of recycled cement and fly ash improves the mechanical performance of mortars relative to those with recycled cement only or fly ash only.

This research investigates complete recycling and utilization of waste concrete to produce new structural concrete through geopolymerization. The investigation was conducted through both macro-and micro/nano-scale studies. First the geopolymer paste synthesized using a mixture of waste concrete fines (WCF) and class F fly ash (FA) as the source material and a mixture of NaOH solution (N) and Na2SiO3 solution (SS) as the alkaline activating agent was studied. Various NaOH concentrations, SS/N ratios, and WCF contents were used to produce geopolymer paste specimens in order to study their effect on the properties of the geopolymer paste. Uniaxial compression tests were conducted to measure the strength of the geopolymer paste specimens. X-ray diffraction (XRD), scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX), and Fourier transform infrared spectroscopy (FTIR) analyses were performed to investigate the micro/nano-structure, morphology and phase/surface elemental compositions of the geopolymer paste and the effect of calcium (Ca) on them. The results indicate that by using 10 M NaOH solution, SS/N of 2 and 50% WCF, the highest geopolymer paste strength can be obtained. Second, the interfacial transition zones (ITZs) between geopolymer (GP) and recycled aggregates (RA) were studied. Considering that RA consist of the stone particles and the attached paste/mortar from the original ordinary Portland cement (OPC) concrete, both the ITZs between GP and natural aggregate (NA) and those between GP and residual OPC paste/mortar (ROPM) were studied. For comparison, the ITZs between OPC paste and NA and those between OPC paste and ROPM were also investigated. 4-point bending tests were conducted to measure the bonding strength of the different types of ITZs at water to solid (W/S) ratio of 0.30, 0.35 and 0.40 for the geopolymer and OPC pastes after 7 and 14 days curing, respectively. SEM imaging was performed to investigate the microstructure of the IT

Population increase and economic developments can lead to construction as well as demolition of infrastructures such as buildings, bridges, roads, etc resulting in used concrete as a primary waste product. Recycling of waste concrete to obtain the recycled concrete aggregates (RCA) for base and/or sub-base materials in road construction is a foremost application to be promoted to gain economical and sustainability benefits. As the mortar, bricks, glass and reclaimed asphalt pavement (RAP) present as constituents in RCA, it exhibits inconsistent properties and performance. In this study, six different types of RCA samples were subjected classification tests such as particle size distribution, plasticity, compaction test, unconfined compressive strength (UCS) and California bearing ratio (CBR) tests. Results were compared with those of the standard road materials used in Queensland, Australia. It was found that material type ‘RM1-100/RM3-0’ and ‘RM1-80/RM3-20’ samples are in the margin of the minimum required specifications of base materials used for high volume unbound granular roads while others are lower than that the minimum requirement.

Storage of mine tailings and waste concrete imposes economical and environmental impacts. Researchers have attempted to reuse wastes as construction material by utilizing ordinary Portland cement (OPC) to stabilize them. This method, however, has a number of limitations related to OPC. In this research, a recent technology called geopolymerization is used to stabilize mine tailings and concrete waste so that they can be completely recycled and reused. The research includes three main parts. The first part studies the effect of different factors on the mechanical properties, micro/nano structure, and elemental and phase composition of mine tailings-based geopolymer binder. The second part investigates the feasibility of producing geopolymer bricks using mine tailings. The physical and mechanical properties, micro/nano structure, durability, and environmental performance of the produced bricks are studied in a systematic way. Moreover, the enhancement of the mine tailings-based geopolymer bricks by adding cement kiln dust (CKD) is studied. The third part of the research investigates the recycling of the fines fraction of crushed waste concrete to produce binder through geopolymerization in order to completely recycle concrete waste. The results indicate the viability of geopolymerization of mine tailings by optimizing the synthesis conditions. By properly selecting these factors, mine tailings-based geopolymer bricks can be produced to meet the ASTM standard requirements and to be environmentally safe by effectively immobilizing the heavy metals in the mine tailings. The physical and mechanical properties and durability of the mine tailings-based geopolymer bricks can be further enhanced by adding a small amount of CKD. The results also show that the fines fraction of crushed waste concrete can be used together with fly ash to produce high performance geopolymer binder. Incorporation of calcium in the geopolymer structure and coexistence of the calcium products such a

Tato diplomová práce se zabývá problematikou použití drobných frakcí betonového recyklátu. V práci jsou popsány teorie k mletí a principy mechanické aktivace při vysokoenergickém mletí. Dále jsou okomentovány články, ve kterých autoři s úspěchem zaktivovali betonové recykláty. V experimentální části diplomové práce bylo navrženo a testováno 11 receptur malt s jemně mletým betonovým recyklátem a 3 receptury betonů. Je provedeno zhodnocení přínosu použití jemně mletého recyklátu jako možná náhrada části cementu., This diploma thesis deals with the issue of using fine powder of concrete recyclate. In this thesis, the theoretical expectations of milling are summarized as well as high energy milling. Afterwards professional articles, in which fine powder of concrete recyclate is successfully activated, are described and commented on. In the experimental part, there are 11 recipes of cement mortar and 3 recipes of concrete mixed. The benefit of using fine powder of concrete recyclate as a possible substitute for part of the cement is evaluated.

Tato diplomová práce se zabývá problematikou použití drobných frakcí betonového recyklátu. V práci jsou popsány teorie k mletí a principy mechanické aktivace při vysokoenergickém mletí. Dále jsou okomentovány články, ve kterých autoři s úspěchem zaktivovali betonové recykláty. V experimentální části diplomové práce bylo navrženo a testováno 11 receptur malt s jemně mletým betonovým recyklátem a 3 receptury betonů. Je provedeno zhodnocení přínosu použití jemně mletého recyklátu jako možná náhrada části cementu., This diploma thesis deals with the issue of using fine powder of concrete recyclate. In this thesis, the theoretical expectations of milling are summarized as well as high energy milling. Afterwards professional articles, in which fine powder of concrete recyclate is successfully activated, are described and commented on. In the experimental part, there are 11 recipes of cement mortar and 3 recipes of concrete mixed. The benefit of using fine powder of concrete recyclate as a possible substitute for part of the cement is evaluated.

Tato diplomová práce se zabývá problematikou použití drobných frakcí betonového recyklátu. V práci jsou popsány teorie k mletí a principy mechanické aktivace při vysokoenergickém mletí. Dále jsou okomentovány články, ve kterých autoři s úspěchem zaktivovali betonové recykláty. V experimentální části diplomové práce bylo navrženo a testováno 11 receptur malt s jemně mletým betonovým recyklátem a 3 receptury betonů. Je provedeno zhodnocení přínosu použití jemně mletého recyklátu jako možná náhrada části cementu., This diploma thesis deals with the issue of using fine powder of concrete recyclate. In this thesis, the theoretical expectations of milling are summarized as well as high energy milling. Afterwards professional articles, in which fine powder of concrete recyclate is successfully activated, are described and commented on. In the experimental part, there are 11 recipes of cement mortar and 3 recipes of concrete mixed. The benefit of using fine powder of concrete recyclate as a possible substitute for part of the cement is evaluated.

Tato diplomová práce se zabývá problematikou použití drobných frakcí betonového recyklátu. V práci jsou popsány teorie k mletí a principy mechanické aktivace při vysokoenergickém mletí. Dále jsou okomentovány články, ve kterých autoři s úspěchem zaktivovali betonové recykláty. V experimentální části diplomové práce bylo navrženo a testováno 11 receptur malt s jemně mletým betonovým recyklátem a 3 receptury betonů. Je provedeno zhodnocení přínosu použití jemně mletého recyklátu jako možná náhrada části cementu., This diploma thesis deals with the issue of using fine powder of concrete recyclate. In this thesis, the theoretical expectations of milling are summarized as well as high energy milling. Afterwards professional articles, in which fine powder of concrete recyclate is successfully activated, are described and commented on. In the experimental part, there are 11 recipes of cement mortar and 3 recipes of concrete mixed. The benefit of using fine powder of concrete recyclate as a possible substitute for part of the cement is evaluated.

Tato diplomová práce se zabývá problematikou použití drobných frakcí betonového recyklátu. V práci jsou popsány teorie k mletí a principy mechanické aktivace při vysokoenergickém mletí. Dále jsou okomentovány články, ve kterých autoři s úspěchem zaktivovali betonové recykláty. V experimentální části diplomové práce bylo navrženo a testováno 11 receptur malt s jemně mletým betonovým recyklátem a 3 receptury betonů. Je provedeno zhodnocení přínosu použití jemně mletého recyklátu jako možná náhrada části cementu., This diploma thesis deals with the issue of using fine powder of concrete recyclate. In this thesis, the theoretical expectations of milling are summarized as well as high energy milling. Afterwards professional articles, in which fine powder of concrete recyclate is successfully activated, are described and commented on. In the experimental part, there are 11 recipes of cement mortar and 3 recipes of concrete mixed. The benefit of using fine powder of concrete recyclate as a possible substitute for part of the cement is evaluated.

Tato diplomová práce se zabývá problematikou použití drobných frakcí betonového recyklátu. V práci jsou popsány teorie k mletí a principy mechanické aktivace při vysokoenergickém mletí. Dále jsou okomentovány články, ve kterých autoři s úspěchem zaktivovali betonové recykláty. V experimentální části diplomové práce bylo navrženo a testováno 11 receptur malt s jemně mletým betonovým recyklátem a 3 receptury betonů. Je provedeno zhodnocení přínosu použití jemně mletého recyklátu jako možná náhrada části cementu., This diploma thesis deals with the issue of using fine powder of concrete recyclate. In this thesis, the theoretical expectations of milling are summarized as well as high energy milling. Afterwards professional articles, in which fine powder of concrete recyclate is successfully activated, are described and commented on. In the experimental part, there are 11 recipes of cement mortar and 3 recipes of concrete mixed. The benefit of using fine powder of concrete recyclate as a possible substitute for part of the cement is evaluated.

The dumping cost of wasted concrete including the rejected units in precast concrete plants is expected to keep rising as the production increases. The waste material from precast concrete hollow core floors (hcu) is high grade and uncontaminated material. This research work was carried out to investigate mainly the strength and other engineering properties of high strength concrete made with recycled concrete aggregate derived from rejected hcu. Three major categories (based on a questionnaire) were investigated: (i) Type of crushers and the crushing method, (ii) The properties of RCA output from these crushers, (iii) The performance of fresh and hardened concrete, including prestressed concrete, with these RCA. The input material for the crushers was from the same origin of disposed hcu's. The waste concrete was crushed to -14 mm using three different types of crushers - the cone, impact and jaw crushers. The recycled material was separated into fractions of 14 mm, 10 mm and - 5 mm, and tested for physical and mechanical properties relevant to use in concrete. Concrete was then made using zero (control mix), 20% and 50% replacement of recycled coarse (RCCA), recycled fine (RCFA) and mixed (RCCA+RCFA) aggregates. All three crushers produced acceptable shape and strength of RCCA. Some properties are competitive to that of natural limestone aggregate. RCFA was much coarser than river gravel and just complied with the British Standard coarse grading limits. The impact crusher performed best with regard to most aggregate properties, e. g. flakiness, strength and water absorption, but has a disadvantage in producing a large amount of fine-to-coarse RCA. Concerning shape and strength, RCA showed similar properties, and in some cases better, than the conventional limestone aggregate. The water absorption for RCA is 3 to 4 times greater than the natural aggregates. For that reason an extra amount of water (called free water) will be added to the mix to compensate the water

The emerging sustainable development movement in the construction industry requires the recycling of waste materials to reduce the negative environmental impact of construction activities. In many countries, old concrete, a major waste stream generated from the demolition of obsolete buildings/structures, is being recycled. However, for various reasons, progress toward concrete recycling varies from country to country. This paper discusses the current status of concrete recycling in the U.S. construction industry based on results from a two-part questionnaire survey. The first part of the survey collects information on the recycling practices of surveyed concrete companies. The second part adapts questions from a study conducted in Australia and Japan to examine the awareness, benefits, difficulties, and recommended methods related to concrete recycling. The findings showed that although recycling old concrete is common in the U.S., its application is mostly limited to backfill and pavement base; using waste concrete in new concrete production is not widely applied. There are also similarities and differences in the perceptions of concrete recycling between U.S. concrete companies and their counterparts in Australia and Japan.

The dumping cost of wasted concrete including the rejected units in precast concrete plants is expected to keep rising as the production increases. The waste material from precast concrete hollow core floors (hcu) is high grade and uncontaminated material. This research work was carried out to investigate mainly the strength and other engineering properties of high strength concrete made with recycled concrete aggregate derived from rejected hcu. Three major categories (based on a questionnaire) were investigated: (i) Type of crushers and the crushing method, (ii) The properties of RCA output from these crushers, (iii) The performance of fresh and hardened concrete, including prestressed concrete, with these RCA. The input material for the crushers was from the same origin of disposed hcu's. The waste concrete was crushed to -14 mm using three different types of crushers - the cone, impact and jaw crushers. The recycled material was separated into fractions of 14 mm, 10 mm and - 5 mm, and tested for physical and mechanical properties relevant to use in concrete. Concrete was then made using zero (control mix), 20% and 50% replacement of recycled coarse (RCCA), recycled fine (RCFA) and mixed (RCCA+RCFA) aggregates. All three crushers produced acceptable shape and strength of RCCA. Some properties are competitive to that of natural limestone aggregate. RCFA was much coarser than river gravel and just complied with the British Standard coarse grading limits. The impact crusher performed best with regard to most aggregate properties, e. g. flakiness, strength and water absorption, but has a disadvantage in producing a large amount of fine-to-coarse RCA. Concerning shape and strength, RCA showed similar properties, and in some cases better, than the conventional limestone aggregate. The water absorption for RCA is 3 to 4 times greater than the natural aggregates. For that reason an extra amount of water (called free water) will be added to the mix to compensate the water

The emerging sustainable development movement in the construction industry requires the recycling of waste materials to reduce the negative environmental impact of construction activities. In many countries, old concrete, a major waste stream generated from the demolition of obsolete buildings/structures, is being recycled. However, for various reasons, progress toward concrete recycling varies from country to country. This paper discusses the current status of concrete recycling in the U.S. construction industry based on results from a two-part questionnaire survey. The first part of the survey collects information on the recycling practices of surveyed concrete companies. The second part adapts questions from a study conducted in Australia and Japan to examine the awareness, benefits, difficulties, and recommended methods related to concrete recycling. The findings showed that although recycling old concrete is common in the U.S., its application is mostly limited to backfill and pavement base; using waste concrete in new concrete production is not widely applied. There are also similarities and differences in the perceptions of concrete recycling between U.S. concrete companies and their counterparts in Australia and Japan.

The emerging sustainable development movement in the construction industry requires the recycling of waste materials to reduce the negative environmental impact of construction activities. In many countries, old concrete, a major waste stream generated from the demolition of obsolete buildings/structures, is being recycled. However, for various reasons, progress toward concrete recycling varies from country to country. This paper discusses the current status of concrete recycling in the U.S. construction industry based on results from a two-part questionnaire survey. The first part of the survey collects information on the recycling practices of surveyed concrete companies. The second part adapts questions from a study conducted in Australia and Japan to examine the awareness, benefits, difficulties, and recommended methods related to concrete recycling. The findings showed that although recycling old concrete is common in the U.S., its application is mostly limited to backfill and pavement base; using waste concrete in new concrete production is not widely applied. There are also similarities and differences in the perceptions of concrete recycling between U.S. concrete companies and their counterparts in Australia and Japan.