•Concrete with fibre reinforcement shows better strength and ductility.•Hybrid steel wire mesh and steel fibre reinforcement improves beam shear capacity.•Beam with hybrid reinforcement shows ...exceptional energy absorption capacity.•Slab with hybrid reinforcement survives 12kg TNT detonation at 1.5m standoff distance.•Numerical model confirms the charge shape effect in the blast tests.
Structural responses and damages under blast loading environments are critical to structural and personnel safety. The blast scenarios involving close-in detonations are attracting increasingly more attentions over the last few decades due to the rising of terrorism. Under close-in detonations, structural elements tend to fail in a brittle mode including shear, concrete crater and spall. In such loading scenarios, the structural designated loading capacity which is usually based on flexural deformation assumption is not fully developed. To provide high-level structural protection, high performance concretes with varying fibre additions are now widely investigated and used in blast resistance designs. In the present study, field blast tests results on reinforced concrete slabs under close-in detonations are presented. Performances of slabs made of normal strength concrete and steel fibre reinforced concrete are compared and discussed. Besides conventional steel rebar reinforcement, new reinforcement scheme i.e. hybrid steel wire mesh-micro steel fibre reinforcement is investigated through the laboratory static tests and field blast tests. Furthermore, a numerical study based on Multi-Material ALE and Lagrangian algorithm is carried out to further investigate the field tests’ phenomenon.
•Concurrent effects of recycled aggregates and polypropylene fibers on internal friction.•Quantifying the magnitude of internal friction on workability of SCC.•Changes in SCC rheological properties ...and passing ability due to RAC and PPF.•Assessing key strength properties due to RAC and PPF.
The concurrent effects of recycled concrete aggregate (RCA) and polypropylene fibers (PPF) on workability of self-consolidating concrete (SCC) are not quantified in literature. Different SCC series containing 25% to 100% RCA and 0.25% to 1.75% PPF are investigated in this study; the water-to-binder ratio varied from 0.38 to 0.5, while high-range water reducer adjusted to maintain slump flow at 700 ± 25 mm. Flowability, cohesiveness, passing ability, and segregation resistance were evaluated and compared with the limitations specified by the European Guidelines for SCC. Test results have shown that SCC rheological properties and passing ability dramatically curtailed with PPF inclusions, especially when mixtures are proportioned with higher RCA replacement rates. This was attributed to combined effects of fiber additions that hinder the cement matrix deformation together with increased RCA surface roughness that accentuates internal friction and resistance to flow. Mixtures containing increased RCA and PPF concentrations exhibited better stability, reflected by reduced aggregate segregation. Series of regression models were proposed to predict the coupled effects of RCA and PPF additions on SCC workability responses.
Digital fabrication represents innovative, computer-controlled processes and technologies with the potential to expand the boundaries of conventional construction. Their use in construction is ...currently restricted to complex and iconic structures, but the growth potential is large. This paper aims to investigate the environmental opportunities of digital fabrication methods, particularly when applied to complex concrete geometries. A case study of a novel robotic additive process that is applied to a wall structure is evaluated with the Life Cycle Assessment (LCA) method. The results of the assessment demonstrate that digital fabrication provides environmental benefits when applied to complex structures. The results also confirm that additional complexity is achieved through digital fabrication without additional environmental costs. This study provides a quantitative argument to position digital fabrication at the beginning of a new era, which is often called the Digital Age in many other disciplines.
•LCA comparison between robotic fabrication and conventional construction.•Mesh Mould construction process analysed from an environmental point of view.•Environmental benefits of digital fabrication when applied to complex structures.•Justification of complexity from a sustainable perspective.
A comprehensive analysis is performed to study the effect of adding carbon nanotubes (CNTs) on the thermal conductivity of short steel fiber (SSF)-reinforced concrete. The role of the CNT dispersion ...and the CNT/concrete interfacial thermal resistance in the SSF/CNT-reinforced concrete thermal conducting behavior is investigated. A good agreement is observed between the model predictions and available experiment. Also, the influences of the SSF aspect ratio, volume fraction and placement type; and the CNT volume fraction, length, diameter and directional behavior on the concrete thermal conductivities are examined. The results reveal that if the CNTs to be uniformly distributed, and the CNT/concrete interface bonding to be perfect, then the concrete effective thermal conductivity is significantly improved. The increasing both volume fraction and length of the CNT leads to the concrete thermal conductivity enhancement too. The CNT diameter and transverse thermal conductivity cannot affect the SSF/CNT-reinforced concrete thermal conducting behavior as well.
•A physics-based hierarchical model is proposed to analyze the thermal conductivity of steel filler/CNT-reinforced concrete.•Both of the CNT/matrix interfacial thermal resistance and CNT agglomeration are speculated in the methodology.•Adding CNTs within the steel fiber-reinforced concrete can improve the effective thermal conductivities.•The maximal thermal conductivity is achieved by forming the interface perfect bonding, and dispersing the CNTs uniformly.
Penelitian ini bertujuan untuk menganalisis kuat tekan beton karakteristik dan nilai faktor koreksi pengujian kuat tekan beton karakteristik pada sisi-sisi paving blok terhadap kubus beton normal ...dengan menggunakan tiga komposisi perbandingan pasir-semen yaitu 25% : 75%, 50% : 50% dan 75% : 25% dengan capaian mutu beton K.300 kg/cm2. Berdasarkan hasil pengujian kubus beton dengan nilai tertinggi kuat tekan beton karakteristik sebesar 323,61 kg/cm2, selanjutnya dibuat cetakan paving blok dengan jumlah sampel masing-masing 20 sampel dengan total keseluruhan 60 sampel untuk ketiga sisi. Dengan menggunakan metode trial and error selanjutnya dilakukan pengujian terhadap sisi masing-masing paving blok setelah umur paving blok sudah mencapai 28 hari. Hasil pengujian kuat tekan beton karakteristik masing-masing diperoleh yaitu sisi memanjang, kuat tekan beton karakteristik sebesar 52,16 kg/cm2 dengan nilai faktor koreksi 4,32, sisi lebar sebesar 408,86 kg/cm2 dengan nilai faktor koreksi 0,64 dan sisi tebal sebesar 406,55 kg/cm2 dengan nilai faktor koreksi 0,61.
The excessive consumption of river sand as a construction material has led to its acute scarcity. Researchers across the globe have attempted to utilize waste of copper slag, rubber tyre, recycled ...glass, pond ash, foundry sand, plastic, stone etc. as a partial or complete substitute of river sand in concrete. The present study investigates the feasibility of using granite cutting waste (GCW) as a partial substitute of river sand in high strength concrete based on strength, durability & microstructural attributes. Eighteen concrete mixes were cast at 0.30, 0.35 and 0.40 water cement ratios (w/c) by substituting 0%, 10%, 25%, 40%, 55% and 70% river sand by GCW. The concrete mixes were tested for compressive, flexural strength, abrasive resistance, permeability, water absorption, carbonation, corrosion and microstructure; changes in morphology and hydration were also studied. Test results suggested that 25–40% river sand can be substituted by the GCW with a favourable influence on the investigated parameters. The optimum amount of GCW to be used in concrete depends significantly upon water-cement ratio of concrete.
•Mechanical and durability parameters of high strength concrete containing granite cutting waste (GCW) are reported.•The study was conducted at three water-cement ratios (0.30, 0.35 and 0.40).•Study concluded that 25–40% GCW can be used as a sand substitute in concrete, depending upon water-cement ratios.
•The effect of steel and forta-ferro fibers on the mechanical properties of high-strength concrete was investigated.•The effect of silica fume and nano-silica on the mechanical properties of the ...fiber-reinforced concrete was studied.•Equations for predicting the strength and the modulus of elasticity of fibrous concrete were proposed.
This paper first addresses the effect of steel and forta-ferro fibers on the mechanical properties of high-strength concrete, and then, investigates the effect of silica fume and nano-silica on the mechanical properties of the fiber-reinforced concrete. In total, 230 concrete specimens were produced in two stages and subsequently tested; in the first stage of specimen production, hooked-end steel fibers with Vf of 0.5%, 0.75%, 1%, 1.25%, and 1.5%, and forta-ferro fibers with Vf of 0.2%, 0.35%, 0.5%, 0.65%, and 0.8% were added to concrete mixture, and in the second stage, silica fume with the weight percentage of 8%, 10%, and 12%, and nano-silica with that of 1%, 2%, and 3% were replaced the cement in mixtures with a fixed volume fraction of both fibers. The aim was to study the mechanical properties of the fiber-reinforced concrete including compressive strength, tensile strength, modulus of elasticity, water absorption, and density, and to propose equations for predicting the compressive and tensile strength and the modulus of elasticity of the fiber-reinforced concrete with no pozzolan.
This study addresses the effects of accelerated hydration in recycled aggregate concrete (RAC) due to the incorporation of High Early Strength Cement (HESC) and employing the steam curing method. The ...RAC was formulated by the complete replacement of natural aggregates with recycled aggregates. The resulting compressive strength, elastic modulus, and shrinkage strain results at early-ages were assessed and compared with concretes incorporating natural aggregates and ordinary Portland cement (OPC). By employing steam curing with HESC as binder, 70% of the design strength could be achieved in one day, however for the contemporary concretes with OPC as binder, the 1-day strength was about 60% of design strength. With HESC as binder, the change in mechanical properties was found to be minimal after 48 h of casting whereas such change was observed at 72 h age for OPC containing concretes. Utilizing recycled aggregates led to a lower net shrinkage strain indicating improvement against early-age cracking. The cost-benefit analysis showed that for accelerated hydration in concrete, utilizing recycled aggregates leads to lower associated CO2 emissions at reduced cost. Replacing OPC with HESC improves the resulting early – age properties, but the production cost also increases. The study suggests RAC and HESC are beneficial for concrete elements with larger surface area to depth ratio, like road pavements, floorings, reinforced concrete slabs, and precast elements.
•A LCCA was performed for structural concrete using seawater and recycled aggregates.•Glass fiber reinforced polymer displaced black steel as the reinforcement material.•The proposed combination ...achieved a 50% cost saving over a 100-year life cycle.•GFRP was more cost effective as reinforcement than black steel and stainless steel.•Results are most sensitive to the selected discount rate and construction costs.
Using seawater and recycled concrete aggregate (RCA) in a concrete mix is potentially advantageous from a sustainability perspective. However, the high chloride levels expected in such a case demands the use of non-corrosive reinforcement in lieu of normal black steel to avoid corrosion problems. Glass fiber reinforced polymer (GFRP) is considered promising as an alternative reinforcement owing to its corrosion resistance and acceptable mechanical properties that minimize maintenance and repairs and extend service life. However, the relatively high initial cost of GFRP bars may mitigate its potential use. To account for these factors, a life cycle cost analysis (LCCA) has been conducted to establish the relative cost savings of structural concrete combining seawater, RCA, and GFRP reinforcement in high-rise buildings compared with a traditional concrete mix and other reinforcement materials, such as black steel and stainless steel.
The proposed combination of seawater, RCA, and GFRP in structural concrete was found to achieve cost savings over a 20-year period following initial construction. The life cycle cost (LCC) obtained for the proposed combination was approximately 50% less than that of the conventional counterpart (i.e. concrete with freshwater, natural aggregates, and black steel) based on a 100-year study period. The use of stainless-steel reinforcement to enhance durability was also found to be potentially advantageous but less cost-effective than using GFRP. The LCC of stainless-steel reinforced concrete was estimated to be 15% lower than that of the traditional steel-reinforced counterpart, with a payback period of 50 years.
Results were found to be highly sensitive to the assumed discount rate and construction costs. The proposed combination achieved cost savings only with a real discount rate (r) of 5.9% or higher. Likewise, using stainless-steel reinforcement was found cost-effective at r⩽1.35% and nominal construction costs exceeding 85% of the material cost. The differences in concrete mixture cost, however, appeared to have insignificant influence on the ultimate LCCA results compared to those obtained from altering the reinforcement material.
Background:
The tensile strength of the plain concrete is weak. Thus, fibres are embedded in concrete to improve its ductility. However, pulling out steel fibres from concrete structures is one of ...the most encountered issues in the fiber-reinforced concrete, which hinders using their maximum capacities.
Objectives:
Thus, closed steel fibres (square shape) were incorporated into concrete mixes to evaluate their impacts against the pulling-out effects and assess the feasibility of applying Closed Steel Fibres (CSFs) on the fresh and hardened concrete properties. Hooked end and straight steel fibres were also investigated for comparison.
Methods:
The utilized steel fibres were incorporated with lengths of 20, 30, and 40 mm, and volume fractions of 0.25%, 0.50%, and 0.75%. Silica Fume (SF) was involved in the fibre-reinforced concrete mixtures at 7% of the cement weight.
Results:
Paper outcomes stated that the inclusion of steel fibres involved different impacts on the concrete compressive strength depending on the applied fibre geometries and content.
Conclusion:
CSFs exhibited better performance against the pulling-out effect from the surrounding concrete structure than those of hooked end and straight steel fibres. However, the addition of CSFs has increased the concrete permeability due to their poor space-filling capacity.
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