This book was proposed and organized as a means to present recent developments in the field of testing of materials and elements in civil engineering. For this reason, the articles highlighted in ...this editorial relate to different aspects of testing of different materials and elements in civil engineering, from building materials to building structures. The current trend in the development of testing of materials and elements in civil engineering is mainly concerned with the detection of flaws and defects in concrete elements and structures, and acoustic methods predominate in this field. As in medicine, the trend is towards designing test equipment that allows one to obtain a picture of the inside of the tested element and materials. Interesting results with significance for building practices were obtained.
The main objective of this study is to provide more data on the effects of expanded perlite on the mechanical properties and thermal conductivity of lightweight concrete. In the experimental program, ...mixtures were prepared by partially replacing natural aggregate by expanded perlite and as a result, unit weights of lightweight concretes in fresh state varied between 700 and 2000
kg/m
3. Water to cement ratio was kept constant in all mixtures. Compressive strength, modulus of elasticity, water absorption and capillarity coefficient of the mixtures were determined. Thermal conductivity of the specimens was also obtained. Test results show that the compressive strength and modulus of elasticity decreases with increasing in perlite content. Water absorption and sorptivity coefficient, however, increase with the higher perlite contents. The test results indicate that the thermal conductivity is substantially improved with the use of perlite and a strong relationship between thermal conductivity and unit weight is obtained.
•Adding steel fiber to the concrete beam enhanced the torsional performance.•The post-cracking ultimate moment of SFRC beams shows a significant enhancement.•SFRC beams show high cracked torsional ...toughness with a large cross-section area.
Steel fiber reinforced concrete (SFRC) has obtained attention from researchers and engineers to be employed in various structural applications to improve concrete structures' performance. However, there are limited experimental test results on the impact of the beam cross-section area along with fiber dosage and configuration on the torsional behavior of the SFRC beams. The aim of this study is to examine the effect of beam section sizes on the characteristics of the torsional performance of cracking and ultimate torsional strengths of SFRC beams. Fiber contents of 0.0, 0.5, 1.0, and 1.5 % with two different lengths of steel fiber were mixed with concrete to study fiber lengths and dosage influences on the torsional behavior. Moreover, torsional loads and cracking and ultimate torque equations of SFRC beams with different fiber dosages and lengths were proposed. Results showed that the SFRC beams exhibited higher cracking torsional moment than the control beams. The hooked steel fiber reinforced beam exhibited the highest increase of the total torsional toughness with the large area and 1.5% fiber dosage, while the straight micro steel fiber beams show good performance with a 1.5% fiber dosage with a small cross-section area. The results from past research and the proposed equations of the cracking and ultimate torques exhibited a good correlation.
This study presents a comparative analysis of the effects of lightweight aggregate concrete (LWAC) and foamed concrete (FC), with dry densities of 500, 750 and 1000 kg/m3, on the thermal performance ...of a typical multi-family (residential) building. Typical two-layer walls consisting of an essential layer (LWAC or FC), with an insulating layer of foamed polystyrene were evaluated. To ensure fixed U values for all variants tested, the thicknesses of the support layers were adjusted accordingly, in such a way that in each variant the load-bearing layer had the same value of the thermal resistance, thus ensuring the same thermal transmittance value for the entire wall. Calculations were made for four different climate zones, making it possible to determine the impact of each variant used, in different climatic conditions. For a hot climate, the data for Cairo (Egypt) was used. A moderate, warm climate was represented by Vienna (Austria), a moderate cold climate by Kołobrzeg (Poland) and a cold climate by Tromsoe (Norway). Significant correlations between the type/density of concrete and climate zones were established. The study shows that, despite comparable densities and thermal conductivity values between LWAC and FC, their specific heat and thus dynamic thermal properties are different. Study provides valuable guidelines and knowledge on choice between proper lightweight concrete type depending on the climate zone. Meaningful conclusions were drawn, showing that the pursue for developing the material with “the lowest” thermal conductivity itself is not the key factor to develop a residential building with satisfactory thermal comfort.
•LWAC and FC with densities of 500, 750, and 1000 kg/m3 were used as a structural layer of wall for typical multi-family building model.•144 variants including 4 locations, 3 ventilation rates, 2 cooling system variants were simulated.•Higher specific heat values of LWAC than FC affects positively both thermal admittance and internal heat capacity.•In hot and mild warm climates, thinner walls with lower thermal conductivity reduced the number of hours exceeding internal temperatures.•The use of thicker wall layers with higher thermal conductivity reduces the heating demand in cold and moderate climates.
Self‐compacting concrete (SCC) is a cementitious composite which serves complex formworks without mechanical vibrations with superior deformability and high resistance to segregation. Besides, the ...recycled aggregate concrete (RAC) is also developing rapidly and along with the ever‐increasing sustainable demand for infrastructure. The combination of the fibers, RAC, and SCC may create advantages for the construction industry. In this study, the polypropylene (PP) fiber at 0.1, 0.15, 0.2, and 0.25% volume fractions and steel fibers at 0.25, 0.5, 0.75, and 1% volume fractions are introduced into fiber‐reinforced recycled aggregate self‐compacting concrete (FR‐RASCC). Both fresh property and hardened mechanical performance, comprising compressive and tensile strengths and modulus of elasticity are analyzed. The fibers validate the optimal 0.1% volume fraction for PP fiber and 0.75% volume fraction for steel fiber. In addition, the results are proved to enhance the mechanical properties and reduce cracking despite the negative impact on the fresh property. Moreover, the experimental outcomes are compared with previous researches to establish the linear model, demonstrating the relationship between fiber fraction and the mechanical properties.
•Axial compressive behavior of RAC-encased RACFST composite columns was investigated.•The whole load-deformation curves and mechanical performance of specimens were obtained.•The calculation methods ...of their bearing capacity are presented and compared.
A new type of composite column, recycled aggregate concrete (RAC)-encased recycled aggregate concrete-filled steel tube (RACFST) composite columns, promotes the RAC extensive utilization considering synergistic effect between the RAC and the steel tube, which is an attempt to develop environmentally sustainable concrete in high-rise buildings. In this paper, experimental research investigated the axial compressive behavior of RAC-encased RACFST composite columns. Twenty 1:3-scaled specimens were fabricated to test until failure under axial compressive loading. The main variable parameters affecting the behaviour of specimens were recycled coarse aggregate replacement ratio (range from 0% to 100% with 10% increase), stirrup spacing (s = 50 mm, 70 mm, 100 mm, 120 mm), diameter of steel tube (D = 89 mm, 114 mm), concrete strength grade (RC40, RC60) and longitudinal reinforcement ratio (4▪12, 8▪12). The failure modes, the whole load-deformation curves and the mechanical performance of specimens were also obtained based on static loading experiments and theoretical analysis. It was found that RAC-encased RACFST composite columns, which were subjected to identical axial loads, exhibited more favorable bearing capacity and deformation than those of a comparative reinforced recycled aggregate concrete columns (RACC). The replacement ratio of RCA had a slight effect on the mechanical performance of RAC-encased RACFST composite columns, the optimal substitution ratio of RCA was 50–60%. Based on the previous theory of superposition, the concrete cover is considered, and a calculation formula with double reduction coefficients of the axial load-bearing capacity of composite columns is proposed. Compared to the simplified superimposition method and the Chinese code Technical specification for steel tube-reinforced concrete column structure (CECS188:2005), the calculated results of axial compression bearing capacity by the proposed formula are in more agreement with the experimental values, with errors no greater than 15%.
Impact resistance of Portland cement concrete (PCC) is an essential property in various applications of PCC, such as industrial floors, hydraulic structures, and explosion-proof structures. ...Steel-fiber-fortified high-strength concrete testing was completed using a drop-weight impact assessment for impact strength. One mix was used to manufacture 320 concrete disc specimens cured in both humid and dry conditions. In addition, 30 cubic and 30 cylindrical specimens were used to evaluate the compressive and indirect tensile strengths. Steel fibers with hooked ends of lengths of 20, 30, and 50 mm were used in the concrete mixtures. Data on material strength were collected from impact testing, including the number of post-first-crack blows (INPBs), first-crack strength, and failure strength. Findings from the results concluded that all the steel fibers improved the mechanical properties of concrete. However, hooked steel fibers were more effective than crimped steel fibers in increasing impact strength, even with a smaller length-to-diameter ratio. Concrete samples containing hybrid fibers (hooked + crimped) also had lower compressive strength than the other fibers. Comparisons and analogies drawn between the test results and the static analyses (Kolmogorov–Smirnov and Kruskal–Wallis) show that the p-value of the analyses indicates a more normal distribution for curing in a humid environment. A significant difference was also observed between the energy absorptions of the reinforced mixtures into steel fibers.
•Pull-out tests of 63 specimens of GFRP bars in conventional and seawater sea-sand concrete reinforced with PE fibers.•Two major failure modes (concrete crushing and bar surface delamination) were ...identified.•Adoption of seawater sea-sand concrete has minimal effect in short-term bond strength.•0.5% PE fiber addition in concrete leads to 3–10% enhancement in bond strength.•ACI440.1R-15 has relatively good accuracy in bond strength estimation.
To tackle the challenge of steel corrosion in conventional reinforced concrete (RC) structures, particularly in maritime environment, the implementation of glass fiber reinforced polymer (GFRP) bars in seawater sea-sand concrete (SSC) structures becomes increasingly popular due to their excellence corrosion resistance. However, the bond characteristics of GFRP bars in fiber reinforced ultra-high strength SSC have not been explored. To this end, a series of pull-out tests on 63 specimens were performed in this study to investigate the influences of different GFRP bar diameters of (i.e., 6 mm, 10 mm and 16 mm), anchorage lengths (i.e., 2.5 and 5 times of the bar diameter), concrete types (SSC and conventional concrete), and polyethylene (PE) fiber contents (i.e., 0, 0.5% and 1% volume fraction) on bond characteristics. The results show that similar to FRP-conventional concrete bond joints, larger bar diameter and longer anchorage length would lead to bond strength reductions for FRP-SSC bond joints. A 0.5% PE fiber addition in SSC would lead to a 3–10% increase in bond strength. However, further increase in PE content to 1% may not necessarily result in further increase in bond strength. Furthermore, the assessment of different design codes revealed that, although ACI440.1R-15 yielded relatively more accurate estimations for bond strength than other design codes, the bond strength could be overestimated if the bar diameter is greater than 16 mm or the anchorage length is less than 5 times the bar diameter.
•A large number of FRP tensile specimens were tested after exposure to SWSSC corrosive solution.•Coupling of stress, corrosion and temperature significantly accelerates the degradation of FRP ...bars.•Scanning electrical microscopy (SEM) was adopted to analyse degradation mechanism.•Long-term predictions of BFRP/GFRP bars using the current model are conservative.
Recently, in responding to the resource shortage and steel corrosion, the combination of seawater and sea sand concrete (SWSSC) and fibre reinforced polymer (FRP) bars was proposed to replace the traditional reinforced concrete structures in civil engineering. For FRP bars in the real service condition of concrete structure, the synergistic effect of sustained load and corrosion environment needs to be considered. This paper presents an investigation on the durability of basalt- and glass-fibre reinforced polymer bars exposed to a SWSSC environment under different sustained stress levels. Scanning electron microscopy was employed to study the degradation mechanism of FRP bars.
•Behavior of anchorages in SFRC is experimentally investigated.•Concrete breakout capacity increases due to the presence of fibers.•Anchors can sustain larger displacements in SFRC.•Design ...recommendations are given for the use of anchorages in SFRC.•Proposal for anchor installation parameters in SFRC.
A large number of studies confirm the beneficial effects of the steel fiber reinforcement in concrete structures. The addition of steel fibers to the concrete mix leads to better mechanical and physical concrete properties including higher fracture energy, reduced crack widths, higher impact and abrasion resistance, increased durability. Due to the increasing popularity of using anchorages in steel fiber reinforced concrete (SFRC), it is essential to understand the behavior of anchorages in SFRC and to validate the applicability of the current provisions for the design of anchorages for use in structural concrete. However, there is only little research available on the behavior of anchorages in SFRC. This paper presents the results of experimental investigations on tension and shear loaded steel anchors in normal-strength plain concrete (PC) and in SFRC. The comprehensive test program includes 62 pull-out and shear loading tests on single anchors and on anchor groups. The test results are discussed in detail to emphasize the influence of steel fiber reinforcement on the load-displacement behavior of fastening systems. The results indicate that the fiber content has a positive effect on the load-displacement behavior of the anchorages, in general. A better utilization of fastening systems can be attained due to the more ductile behavior and due to the crack bridging mechanism of the SFRC. Furthermore, in certain applications and parameter combinations the ultimate load in case of concrete failure may be higher in SFRC compared to PC.
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