Papers by Luis Evangelista
Case Studies in Construction Materials, 2019
Currently, the disposal of used tires is a worldwide challenge, due to their nondegradability. Th... more Currently, the disposal of used tires is a worldwide challenge, due to their nondegradability. Therefore, recycling has become a potential solution for managing such waste. During recycling, materials such as rubber and steel are recovered from the used tires. The use of steel fibres, recovered from tire waste, as a raw material to reinforce concrete is an environmentally friendly and economically viable solution to manage the end-products of tire recycling. Few studies have been carried out to study the behaviour of fibre-reinforced concrete made using steel fibres recovered from tire waste. However, it has been found that there is the potential to reuse steel fibres recovered from tire waste (RF) as an alternative building material to manufactured steel fibres (SF). Nevertheless, more research is needed to verify that the structural performance of recycled fibre reinforced concrete (RFRC) is similar to that of manufactured fibre reinforced concrete (SFRC). Therefore, this study focuses on the laboratory testing of the mechanical properties of RFRC and compares them with those of SFRC. Moreover, the flexural performance of reinforced concrete beams cast with RF and SF have been tested to compare their performance.
ACI Materials Journal, 2012
ABSTRACT This paper presents the main results of experiments conducted to ascertain the influence... more ABSTRACT This paper presents the main results of experiments conducted to ascertain the influence of different curing conditions on the durability of recycled aggregate concrete (RAC) made with coarse crushed concrete. Four different curing conditions representing a wide range of quality control production, ranging from uncontrolled outer environment conditions to standard defined temperature humidity curing conditions, were tested. The properties analyzed were shrinkage, water absorption by immersion and capillarity, carbonation, and chloride penetration. The general conclusion is that RAC is affected by curing conditions in much the same way as conventional concrete (CC).
Construction and Building Materials, 2021
The high cement content of high-performance concrete (HPC) results in improved strength, but also... more The high cement content of high-performance concrete (HPC) results in improved strength, but also in large shrinkage. The substitution of natural aggregates (NA) with recycled aggregates (RA) notably affects these properties in conventional concrete. This study intends to analyse the effect of the content of RA and their maturity (time elapsed between casting and crushing of the parent concrete from which RA are obtained) on these properties of HPC. To this end, five mixes were manufactured with 0%, 25%, and 100% of coarse and fine RA of different maturities, 7 days (early-age RA) and 6 months (matured RA). The mechanical properties and the autogenous, drying, and total shrinkage of all mixes were determined. Both the increase of RA content and the lower stiffness and strength of early-age RA relative to matured RA worsened the mechanical behaviour of HPC. Regarding shrinkage, the lower stiffness and higher water absorption of matured RA compared to NA decreased autogenous shrinkage by 20%, but increased drying and total shrinkage. The lower stiffness of early-age RA and their shrinkage amplified all types of shrinkage of HPC around 10–20%. Nevertheless, the hydration of their unhydrated cement particles during the mixing process reduced those increases from what was expected. Total shrinkage of early-age recycled aggregate HPC could be estimated from the shrinkage of both a HPC mix of identical composition but with matured RA and the parent concrete. Overall, it can be concluded that RA's maturity affects the mechanical performance and, especially, the shrinkage of HPC, so it should be considered when using this type of aggregate.
Construction and Building Materials, 2021
PtJrpo~e+ To ¢l'mra¢lenzo tbe d~]me I.~THK) and {~fe el i~Iftlal wall thlckefllrl~J stlt~e(Itlenl... more PtJrpo~e+ To ¢l'mra¢lenzo tbe d~]me I.~THK) and {~fe el i~Iftlal wall thlckefllrl~J stlt~e(Itlenl to ablaPon using in~r~i~!ffi~¢ echoeardlogr~Dhy (ICE/ Meft!o(~: ICE (9 MH~I lmao*ng gu~le(t catheter ab~af~r~s *n the ~Oht (RAI a~ ~lt afrll.a~rt (LA) were pedw/ne~ in ;' Closed c.hest SWit~ (~120 kg) ~n~rgy ,~l~¢~Im~ Irnamroa! powe~-empmc, temperate rrl feeDing.pas
Engineering Structures, 2019
The model uncertainty of the shear resistance equations of three design codes {the current Euroco... more The model uncertainty of the shear resistance equations of three design codes {the current Eurocode 2 (2004), Model Code (2010), and the final draft of the Eurocode 2 (2020)} was investigated for coarse natural and recycled aggregate concrete beams. Databases of beams with and without shear reinforcement were made with clearly defined criteria. The statistics of the model uncertainty of natural and recycled concrete beams were compared and it was found that recycled aggregate incorporation has detrimental effects on the model uncertainty of shear design. Surprisingly, recycled concrete aggregate beams designed following the current version of Eurocode 2 (2004) are safer than those designed using the other codes. This is due to the shear resistance equations of the latter overestimating the aggregate interlock of recycled aggregate. A preliminary partial factor was proposed, offsetting the influence of recycled aggregate on the safety of beam designs. The database of beams with shear reinforcement lacks representativeness but hinted that recycled aggregate incorporation also reduces the safety of this type of shear design. The paper finishes presenting suggestions of experiments that would complement the current knowledge on this topic.
Construction and Building Materials, 2019
h i g h l i g h t s Benchmark of the statistics of Portuguese ready-mixed concrete plants. Slump ... more h i g h l i g h t s Benchmark of the statistics of Portuguese ready-mixed concrete plants. Slump and 28-day compressive strength compliance were investigated. Probabilistic modelling of a bias factor for the 28-day compressive strength. Low bias factors may result in rejected concrete even if the concrete has low variability. Non-uniform bias factor dependent on plant and specified compressive strength.
Construction and Building Materials, 2018
h i g h l i g h t s Superplasticizers as a means to produce durable recycled aggregates concrete.... more h i g h l i g h t s Superplasticizers as a means to produce durable recycled aggregates concrete. Effect of recycled aggregates composition and incorporation ratio on concrete. Comparison of concrete with and without superplasticizer. Recycled aggregate characteristics limit the efficiency of superplasticizers. Superplasticizers improve durability except when chloride ingress is a concern.
Construction and Building Materials, 2018
h i g h l i g h t s Using coarse recycled aggregates (RA) from recycled aggregate concrete is via... more h i g h l i g h t s Using coarse recycled aggregates (RA) from recycled aggregate concrete is viable. The properties of the RA tend to stabilize as the total recycling cycles increase. The mechanical properties RAC tend also to stabilize with the number of cycles. Three recycling cycles are required to achieve stable thresholds for most properties.
Cement and Concrete Composites, 2018
This study intends to analyse the effects of the incorporation of recycled aggregates (RA) and de... more This study intends to analyse the effects of the incorporation of recycled aggregates (RA) and densified silica fume (SF) on the durability of high performance concrete (HPC). Considering that the mortar adhered to the RA strongly influences the behaviour of the concrete made with it, the source of these aggregates was restricted to precast mixes with target compressive strengths of 75 MPa and subjected to a primary plus a secondary crushing process. With regard to SF, a certified commercial product was used, which was incorporated in the concrete as an additional material to cement. The experimental campaign included the production of 12 types of concrete, which were evaluated by means of water absorption by immersion, water absorption by capillarity, resistance to carbonation, resistance to chloride penetration and permeability to oxygen tests. The results show that it is possible to produce HPC with significant quantities of fine and coarse recycled aggregates (FRA and CRA) as replacement of traditional fine and coarse natural aggregates (FNA and CNA). Ultimately, considering the properties analysed, it seems possible to produce HPC without incorporating natural aggregates (NA). The incorporation of densified silica fume contributed to an increase of concrete's performance through the use of a mixing process developed by the authors that minimized the previously endured dispersion difficulties associated with this product.
Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada, Jan 23, 2015
This paper intends to analyze the microstructure of concrete with recycled aggregates (RA) from c... more This paper intends to analyze the microstructure of concrete with recycled aggregates (RA) from construction and demolition waste from various Portuguese recycling plants. To that effect, several scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyses were performed. Various concrete mixes were evaluated in order to analyze the influence of the RA's collection point and consequently of their composition on the mixes' characteristics. Afterward all the mixes were subjected to the capillary water absorption test in order to quantitatively evaluate their porosity. Results from the SEM/EDS analysis were compared with those from capillary water absorption test. The SEM/EDS analysis showed that the bond capacity of aggregates to the new cement paste is greatly influenced by the RA's nature. On the other hand, there was an increase in porosity with the incorporation of RA.
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Papers by Luis Evangelista