Concrete Grout Research Articles

Mechanical behavior of a novel compact steel-UHPC joint for hybrid girder bridges: Experimental and numerical investigation

Ultra-high-performance concrete (UHPC) has recently been applied as an alternative to normal concrete in steel-concrete composite structures. In this paper, a novel compact steel-concrete joint with UHPC grout, which utilizes shear connectors, a bearing plate and a simple I-shaped steel girder, is proposed for long-span railway hybrid girder bridges. To investigate the mechanical behavior and force transfer characteristics of the proposed compact steel-UHPC joint (CSUJ), a model test with reduced scale and push-out tests of its main force transfer components were conducted. The specimens' failure model, load-interface slip, and strain development were compared and discussed in detail. Furthermore, a finite element model of the CSUJ was established to investigate the internal damage evolution and the load transfer path. The test results indicated that the steel-UHPC joint possessed excellent axial stiffness and cracking resistance. The axial stiffness before cracking is 2.6 times that of the steel-concrete joint prototype with C60 concrete grout. Upon loading, the filled-in UHPC of the CSUJ was in elastic compression. In the ultimate limit state, the steel-UHPC joint exhibited great integrity, and the ultimate failure mode of the CSUJ was controlled by the adjacent axially loaded steel beam segment. Results of push-out tests showed that the force transfer component with perfobond leiste (PBL) connectors demonstrated greater ductility than other transfer components. In terms of the force transfer rate and uniformity, the proposed CSUJ provides desired stress distribution and force transfer behavior. The shear connectors, bearing plate, and end face of the I-girder transferred 49%, 35%, and 16% of the total axial force, respectively.

Reliability, sustainability, resiliency, and performance investigation of an embedded splice-sleeve connector at high velocity semi-trailer impact

Presently, dynamic impacts occurrences caused by car crashes have been frequently reported. Statistical results from different articles indicate that vehicle crashworthiness of bridge pier supersedes the other events. However, majority of the published articles focusses on sustainability and finding severity of distressed pier due to impact correlating faster construction methods, like accelerated bridge construction (ABC). This article is an attempt to examine post impacted behavior of a commonly used connector in ABC for resisting short duration shock. Static and dynamic performance analyses of a connector embedded within a coupler system has been examined. A representative ABC pier with the standardized and selected material properties collected from manufacturer’s data has been utilized. Coupler composite materials consisting of a hollow uniform cross-section cast iron cylinder filled up with specified concrete grout conforms higher strength. The performance examination has been conducted by numerical modeling using finite element method (FEM). A commercially used software ANSYS has been utilized for carrying out the simulations. To investigate the post impact dynamic behavior, mesh-independent studies seems inevitable and hence are executed to evaluate dynamic impact factor (DIF). Sensitivity studies are carried out for validating results in precision. The DIF of the main reinforcing tensile steel embedded into the grout placed inside the connector has been determined. Results captured from simulations to identify material properties at plastic stage in sustaining such load have been conducted. The results provide significant information that aids opting for selecting suitable connectors for attaining help the design offices.

Sustainability and Resiliency Investigation of Grouted Coupler Embedded in RC ABC Bridge Pier at Vehicle Impact

Increased occurrences of natural and man-made dynamic loading caused by high strain rate dynamic impact load have been recently reported. Different statistical results indicate that vehicular impacts occur more frequently compared to the other dynamic loads. However, existing literature primarily focuses on enhancing survivability and determining damage levels specifically in relation to faster bridge construction methods used as an accelerated bridge construction (ABC). In this context, the present study investigates the dynamic behavior of a commonly used connection type in ABC, namely grouted coupler that connects pre-cast elements like bridge piers and foundations. To execute the research, both the static and dynamic performance of grouted couplers embedded in pier foundation subjected to high strain rate loading incurred by high velocity vehicular impact are examined. A representative non-traditional reinforced concrete (RC) bridge pier is selected for the study with the standardized geometry and selected material properties. The use of splice sleeves as coupler materials and specified cross-sectional hollow cast iron cylinders filled with high strength concrete grout is employed for developing Finite Element (FE) modeling, extracting data from published journals. A commercial software, ANSYS, has been utilized to develop FE models to capture post impact respective static and dynamic behaviors, and the simulation results are then compared with the analytical. This also includes determining material performance via FE simulations. By considering dynamic loading, the dynamic impact factor (DIF) has been evaluated for the reinforcing steel bar adjacent and embedded into the coupler. In addition, dynamic simulations, and material modulus in demand to sustain impact are determined. Thus, the research necessitates mesh-independent sensitivity studies to investigate DIF corresponding to the precise outcomes. The findings of this study manifests valuable information that aids to opt for the suitable coupler connections, considering material properties, and adequate post impact execution. Consequently, it will serve as a useful design tool for design offices, structural practitioners, and forensic structural engineers.

Shear behavior of prestressed concrete T-beams strengthened by steel plate-concrete composite

The shear performance of prestressed concrete T-beam strengthened by steel plate-concrete composite is experimentally and numerically investigated in this research. Two specimens are designed and tested before and after strengthening. It is observed that the shear performance and ductility of the strengthened specimen are improved. Failure of the strengthened specimen is caused by the detachment of the strengthening portion. Nonlinear finite element models are developed and benchmarked with test results. Parametric analysis is conducted to study the effect of the connection strength and material strength. It is found that the shear strength of the member increases with increasing connection strength, while the strength of the grout concrete and steel plate also affects the shear strength. The test results and finite element results show that the proposed strengthening technique effectively improves the shear performance of the specimen, and its improvement effect is governed by the connection strength between the existing and grout concrete.

<i>Retracted: </i>Performance of Grouted Coupler Embedded in Reinforced Concrete ABC Bridge Pier at Vehicle Impact

Increased occurrence of dynamic loading on bridge piers caused by seismic, blast and vehicular impact incidences have been increasingly reported. Statistical data shows that while seismic and blast have received significant attention in the literature, whereas the frequency of occurrence of vehicular impact is remarkably higher but contemplating little consideration. With the newer construction methods like accelerated bridge construction (ABC) and its response against vehicle impact performance needs an additional study before widespread use. Static and dynamic performances of the coupler are investigated. A representative circular RC bridge with circular cross-section is considered and hollow cylindrical splice-sleeves filled up with concrete grout is embedded in the foundation. Finite element model (FEM) of single grouted coupler is developed based on the manufacturer data. Apportioned load through load ratio is considered and applied to the individual coupler. Numerical simulations are also performed using commercial finite element software package, ANSYS. This research is led by mesh independent studies to precisely accomplish sensitivity analyses. The results from numerical simulations are compared with the corresponding analytical solution. Stress-strain resulted from conservative dynamic simulation are plotted followed by integrity analyses to capture material performance at high deformation. Quasi-static strain rates are utilized for steel re-bars with connected coupler and validated with the finite element (FE) results to determine dynamic impact factor (DIF) of steel. This is further validated through utilizing experimental data from published journal. This study instills a good agreement by providing valuable information to aid in the selection of appropriate coupler connections, addressing material properties at various performance level, and contributes useful guidelines for the researchers, practitioners, and structural engineers.

Effect of Fiber Content on Mechanical Properties and Microstructural Characteristics of Alkali Resistant Glass Fiber Reinforced Concrete

Owing to its enhanced strength, ductility, and resistance to harsh environments, increasing research attention has been paid to alkali-resistant glass fiber reinforced concrete (ARGFRC). This paper presents experimental studies concerning the effects of fiber content on the mechanical properties and microstructural characteristics of ARGFRC. The amount of glass fiber was considered at levels of 0.0, 0.3, 0.5, 0.8, 1.0, 1.3, and 1.5% of the concrete volume. The compression, flexural, impact resistance, scanning electron microscopy, and energy dispersive spectroscopy tests were conducted. The flexural load-deflection curve, flexural strength, flexural toughness index, flexural fracture energy, postcracking stiffness, postpeak stiffness, and impact resistance energy absorption were obtained. Then the changing law affected by fiber content on these mechanical properties was further analyzed, and the corresponding equation was fitted. When fiber content was 1.5%, the flexural toughness index I5, I10, and I20 values were 4.0, 5.9, and 8.9, respectively, and increased by 3.0∼7.9 times. Glass fiber incorporation could increase the ductility and delay the brittle failure when the fiber content reached 0.8%. The largest postcracking stiffness was calculated at 36.174 kN/mm with a fiber content of 0.8%. The higher the fiber content, the larger the postpeak stiffness of the tested beams. Impact resistance test results demonstrated that the optimum fiber content was 1.3%. As the fiber content increased, the effect of the concrete grout on the fiber packaging decreased, according to the scanning electron microscopy analysis. The energy dispersive spectroscopy observation proved that adding a certain fiber content did not affect the concrete hydration reaction.

Experimental and analytical assessment on rubberized concrete interlocking grouted masonry walls under eccentric loading

In this study, the concept of interlocking masonry is modified by introducing waste materials, fly ash (FA) and crumb rubber (CR), to overcome the issues of mortared walls and conventional interlocking walls. Therefore, this research is aimed to investigate the behavior of rubberized concrete interlocking grouted masonry walls (RCIGMWs) subjected to eccentric compression loading experimentally. Twelve RCIGMWs of size 1260 mm height × 625 mm width × 125 mm thickness were constructed, by stacking RCIBs in running bond on top of one another without the use of mortar layers, however, the center cores (holes) of the wall panels were filled by pouring the concrete grout into. RCIGMWs were then tested under four axial compression eccentric loading levels including e=0, e=t/6, e=t/3, and e=t/2.5 where the top of the wall panels was considered for eccentricity while the end was maintained flat as a fixed. The bottom support was fixed while the upper end was free. The structural responses including the efficiencyof the walls, axial displacement and lateral deformation, and failure mechanisms were investigated. The experimental findings show that higher compressive eccentricities adversely impacted the behavior responses of RCIGMWs. Under eccentricities greater than kern distance, walls suffered significant loss of their load-bearing capacity. Moreover, higher lateral deflection was recorded at higher eccentricity levels as a result of the developed wall’s bending moment. Vertical splitting failure was observed between the webs and brick shells, which was followed by localized spalling. A global buckling was formed at higher eccentricity levels where the wall bent and the dry bed joint at the upper height of the wall opened and failed prematurely. Analytically, the EC-6 and ACI-530 are able to calculate the load-bearing capacity of the RCIGMWs, however, they tend to underestimate it with increasing the eccentricity while BS 5628–1 provides approximately 90 % precision.

Parametric study on seismic performance of prefabricated bridge piers connected by ultra‐high performance concrete grout

AbstractIn this study, a novel prefabricated pier connected by ultra‐high performance concrete (UHPC) connection is introduced based on an actual project, and several seismic preformance related parametric analyses were conducted based on the validated numerical models. The objective of this research is to evaluate the impact of several critical parameters on the seismic performance of the novel prefabricated piers. The validity of the numerical modeling method has been verified based on a cyclic loading test of a relevant large‐scale novel prefabricated pier. Meanwhile, several seismic design‐related parameters are selected, e.g., shear‐span ratio, mechanical properties of UHPC, embedded length of reinforcement bars, etc., to evaluate the seismic performance of UHPC grout connected prefabricated piers. In order to ensure that the novel prefabricated pier exhibits acceptable seismic performance, the shear‐span ratio of the prefabricated bridge piers should be higher than 2.5, the axial compression ratio should be lower than 0.35, the recommended minimum embedded length is 8 times bar diameter and UB or UA UHPC with strain hardening properties should be selected as grouting material. Meanwhile, the reasonable longitudinal reinforcement ratio should be carefully considered according to engineering requirements and seismic design details.

Interfacial Phenomena at the Interface in the System «Carbon Primary Materials-Water Solutions of Surfactants» for Cement Materials

The formation of sustainable concrete is directly relaed to the intensity of the processes occurring at the interface of phases. The study of the surface properties of CNPLUS carbon nanotubes in solutions of various plasticizers was carried out by measuring and calculating adsorption. The applicability of the adsorption value is for forecasting both the efficiency of dispersion and aggregative and sedimentative stability of the obtained dispersion systems. It was stated that two-dimensional pressure arising at the interface of adsorption layers in the dispersive medium with the surfactant Tensafor 2553.2 J/m2 is sufficient to overcome adhesive strength on a small area of the localized contact of carbon nanoparticles CNPLUS, which explains the peptization and stabilization of the particles’ surface. It was established that full stabilization of nanoparticles in the aqueous dispersive medium could be ensured only by means of soap-like surfactants, with the compound potassium naphthalene sulfonate (Tensafor). It ensures formation of the micelle-like structure in coagulation layers that forms a structural and mechanical barrier with the external hydrophilic surface. This leads to the increase in the ultimate tensile strength of the concrete grout specimens by 38%.

Konka Board: a cement-pumice-tow sheathing board

Konka board was a New Zealand invention which combined cement, pumice and flax fibre ("tow") into a fibre-cement board, replacing the imported asbestos-cement sheet. Sold soon after manufacture, Konka, it could be nailed or screwed, and over time it hardened. A waterproof plain or stucco plaster finish provided a resilient, borer proof, fireproof, low maintenance house. Three patents created the Konka system – 34,845 for the fibre-reinforced board, 37,354 for the stud and support system into which a concrete grout was poured to lock the panels in place, and finally 52,50 for metal strips to ensure a smooth final plaster surface. A waterproofing additive in the plaster provided the final part of the system.The company quickly setup a national series of agents, with manufacturing ultimately occurring in Wanganui, Gisborne, Christchurch and Timaru. Patent 34,845 was challenged in 1927, with the Privy Council finding in 1930 that it was invalid, opening the way for similar products to be made. The development in the 1930s of NZSS 95 Model Building By-law allowed Konka to be used nationally, without further evidence as to its performance. However, competitor other products were also included e.g. Excell, Rotorua, Thermax, Duro, Wangan, Walasco and the asbestos based Fibrolite.Konka survived until the 1960s, when flax production was in decline, the high labour costs and manufacturing time meant it was no longer competitive. Even so, in a twist of fate it was a Konka style approach which led to cellulose fibre replacing asbestos in fibre-cement sheeting. In the twenty-first century, Konka could even be considered a desirable product – a natural fibre reinforced, composite sheet.

A new proposal for a grout-tooth connection

The paper deals with the strength characteristics of a grouted connection proposed for the shear transfer between steel elements or steel-to-concrete connections. The connection has been designed and tested at TU Berlin (Technische Universität Berlin) in the chair of Hybrid and Composite structures (Verbundstrukturen). Three types of grout have been used. The commercial names of the grout are BETEC180, COMPONO, and Sikadur-42; BETEC180 belongs to the family of high-performance cementitious grout, whereas COMPONO and Sikadur-42 relate to polymer concrete. The three brands are chosen as an example represents the behavior of such connection using cementitious grout and polymer concrete. Though the compressive strengths of all grouts are close, there are substantial differences in the tensile and shear capacity between the cementitious grout and the polymer concrete grout. To investigate the performance of the connection under shear, three tests for each material are conducted. The average load capacities of the three types of grout (BETEC, COMPONO, and Sikadur-42) are: 67,7 kN, 117,3 kN, and 124,5 kN, respectively. Furthermore, the connection with cementitious grout showed the most brittle performance, and Sikadur-42 connection presents the best behavior in terms of ductility and load capacity. However, the failure mode is comparable in all connections. Three-dimensional nonlinear Finite Element Models (FEM’s), for the three different connections, have been carried out using ANSYS software. The FEMs are in good agreement with the observations in the experiments. The models are useful in explaining the stress development and crack pattern within the grout and the failure mode of the connection.

Experimental and numerical investigations of a timber-concrete dovetail splice joint

Cross-laminated timber panels offer an effective option for timber structures; they allow biaxial load transfer and have good dimensional stability. However, practical transportation and handling limits size of the panel and a stiff connection between the panels is required to effectively utilise biaxial properties. In this paper, a dovetail splice joint for timber panels is presented using cross-banded LVL with cast concrete grout interlayer. The interlayer allows a tight fit, which is important for stiffness, but also avoiding installation problems due to manufacturing tolerances and moisture-induced dimensional changes. The mechanical behaviour of the dovetail joint was investigated experimentally for various geometries. Furthermore, a numerical model was developed that shows a wide agreement with the experiments, especially in the cases with governing failure in the LVL. Using the numerical model, a parameter study was performed where the influence of the connection length (number of dovetails) and the joint geometry on the strength and stiffness properties was investigated. Besides the optimal geometrical configurations of the dovetail joint, also a significant increase of the strength and stiffness properties with increasing connection length was identified.

Evaluation of Chloride Intrusion along Concrete–Grout Interfaces for Post-Tensioned Concrete Durability

A pour-back is a critical component of a post-tensioned concrete system, affecting its durability by protecting anchorages and vents from corrosion. However, the material interface between the grout pour-back and the concrete member may serve as an accelerated pathway for chloride ion intrusion and may lead to premature corrosion of post-tensioning components. This study evaluates the vulnerability of concrete–grout interfaces through two experimental protocols: a novel electrical migration test and the standard electrical resistivity test. The results are used to predict the service life of pour-back systems using a concrete life-cycle assessment model. This research serves as a first step toward defining the chloride permeability of concrete–grout interfaces.

Three-dimensional numerical modeling of water distribution tunnels in karst area

Karst physiognomy is a common terrain in mountainous area. The tunnels constructed through these terrains may suffer from stress maldistribution due to the existence of the karst caves. The lining of water distribution tunnels passing through karst caves suffer from both the outer pressure of surrounding rock and the inner water pressure that could cause cracks of the lining and seepage of the water. This study focuses on the influence of exposed karst caves on water distribution tunnels. In order to assess the risks caused by the karst caves, finite element methods are carried out. Test datum of the tunnel in the Water Distribution Project of Qiandao Lake is used to validate the accuracy of the FEM model. The effects of filling the karst cave with concrete and embedding pre-stress steel strands into the lining are studied, respectively. Results show that filling the karst cave with concrete grout can eliminate the inhomogeneity of the tensile stress of the lining, and embedding the pre-stress steel strands into the lining can resist the inner water pressure effectively. Meanwhile, the most appropriate pre-stressing force and the relationship between the pre-stressing force and the inner water pressure are suggested.

Design of Interlocking Bricks Beam

Interlocking Brick System (IBs) is one of the current technologies used in the construction of load bearing walls. The concepts behind the IBs include the elimination of the mortar layer. The interlocking brick system investigated in this study is load bearing interlocking brick beam system relied on U-shaped hollow bricks in bed row to form beam to transfer load from wall opening. Reinforced concrete grout stiffeners were added in vertical and horizontal directions to enhance the stability and integrity of the beams. Mortar and grout are used as infill material. Generally, in this research, specimens are prepared for full scale testing with different parameters in reinforcement and fillings. The size of interlocking brick is 125 mm x 250 mm x 100 mm and the diameter of reinforcement bar (rebar) used is 12 mm. The dimension of the interlocking bricks beam is 2130 mm length, 125 mm width, and 300 mm height. The arrangement of hollow interlocking brick in bed row will causes a ductile behavior which will be mitigated by the horizontal reinforcement coated by mortar or grout between two layers of hollow brick.

Numerical study on seismic behavior of precast bridge columns with large-diameter bars and UHPC grout considering the bar-slip effect

A novel connection adopting lap-spliced large-diameter bars and ultra-high performance concrete (UHPC) grout was developed to accelerate the assemble progress of precast bridge columns. The precast bridge column adopting the connections was testified to be on a par with the monolithic concrete counterpart in terms of seismic performance in previous research. This paper aims to develop a numerical model to further investigate the seismic behavior of the proposed bridge column considering the bar-slip effect. A finite element model was established for the bridge columns considering deformation components of flexure, shear, and bar-slip. The bond behavior between the deformed bar and UHPC was defined using a new practical model, which was developed based on a pullout test including five specimens in this research. The established finite element model was verified by the cyclic loading test in literature in terms of the overall hysteretic curve and local responses. The validated model was used to conduct parametric analysis to study the contributions of the different deformation components to lateral deformation as well as the effects of large-diameter bars on seismic performance. Results show that all the pullout specimens have the tensile fracture of bars, which indicates that the development length of 5 times bar diameter is sufficient for deformed bars in UHPC when the bar diameter is no more than 32 mm. The practical model is effective to consider the effects of the slip between the deformed bar and UHPC. The finite element model can predict the overall hysteretic curve and local responses at different drift ratios. The bar-slip has a considerable even dominative contribution to the lateral deformation of the proposed bridge column. Larger bar diameter can enhance deformation capacity as well as reduce energy dissipation and residual drift ratio.

Influence of pine resin on thermo-mechanical properties of pumice-cement composites

In this study, aggregate pumices are used to produce new construction materials with low density. Pumices are grinded and then classified according to their maximum grain diameter, namely dmax ≤ 5 mm, dmax ≤ 10 mm and dmax ≤ 20 mm. The cement is added into each group as the binder material. The pumice ratios in the specimens are estimated to be 20, 40, 60 and 80% of the total volume. Moreover, pine resin (approximately 1% of cement + pumice mixture) is added to concrete grout to generate artificial pores in each specimen group. The prepared samples are dried during 28 days at room temperature and then the thermo-mechanical measurements are carried out. It was observed that, as the pumice ratio and particle diameter increase, the porosity and water absorption increase, but density, thermal conductivity and compressive strength decrease. Some artificial pores (in addition to pumice pores) are generated in concrete blocks, leading to improvement of insulation properties of the material. The thermal concutivity respectively decreases as 8-15%, 7-12% and 5-13% for the resin-mixed samples with dmax ≤ 5 mm, dmax ≤ 10 mm and dmax ≤ 20 mm. Similarly, the compressive strength values drop 10–13%, 6–10% and 8–12% respectively for each dimeter group.

In Situ Experimental Study on the Active Support Used for Building Rectification.

There are many vertically deflected building structures in the world that require rectification. Temporary supports installed in the building bearing walls can be used to perform such a rectification. The supports consist of a hydraulic piston jack, a stack of parallelepiped steel elements, and a concrete grout. The structure is unevenly raised and reaches the desired vertical position using such supports. The support in which the piston extension is forced at the given time is an active support. The aim was to determine the stiffness of an active support. The investigations were performed in in situ conditions during experimental building rectification. No such investigations have been performed to date. It has been demonstrated that the stiffness of the investigated support results from the stiffness of the serially connected elements forming the support. In general, the support stiffness depends on the value of the force occurring in the support and is rising linearly along with the load for the investigated range. It was also shown that the force existing in the active support also depends on the stiffness of the building being rectified. The investigations carried out show that it is advantageous to use supports with smaller stiffness for rectification, as forces with smaller values must be induced in them. The application of forces with lower values also allows the avoidance of unfavorable penetration of the unlifted part of the building into the ground.

Kuat Tekan dan Kuat Tarik Mortar sebagai Bahan Graut dengan Faktor Air Semen Optimum

Grout works as a binding agents of wall construction, paste parts on precast concrete, a filler on concrete or crack also sealing a conctrete join. The purpose of this study is knowing optimum concrete grout composition. Grout strength hopefully can fulfill compression and tension strength needed, fulfill slashyness requirements, no bleeding and no segregration. Research began with preliminary test of mortar composition charasteristics. Most of fine aggregate composition using sand with slightly fine sand gradation. The mortar slashyness test using mortar flow and funnel test that flow time of mortar used as slashyness rate. Next tests are compression and tension test of mortars. The variation of mortars composition are using cement : sand ratio in the amount of 1:0,5; 1:1; 1:1,5 and 1:2. The result from each mix with optimum W/C Ratio for the compression strength test in the amount of 1:0,5; 1:1; 1:1,5 and 1:2 consecutively are 45,518 MPa; 37,875 MPa; 34,673 and 28,202 MPa. For the tension strength test are 3,054 MPa; 3,314 MPa; 3,498 Mpa and 1,791 MPa.

Seismic performance of mortarless reinforced masonry walls

Reinforced masonry walls are commonly used as a primary lateral load resisting system in buildings in regions of moderate or high seismicity. Mortarless reinforced masonry (MLRM) walls are constructed using concrete masonry units placed without mortar and then interconnected by concrete grout. The absence of mortar can overcome several issues during the construction of conventional reinforced masonry walls. Previous research mainly focused on mortarless systems using three-dimensional interlocking blocks without vertical reinforcement. In this study, a total of six MLRM walls were constructed and tested under cyclic loadings to investigate their seismic behaviour. Experimental parameters included axial load ratio, shear span ratio, and vertical reinforcement ratio of the walls. Test results showed that the MLRM walls exhibited high stiffness, good deformation capacity, and reasonable energy dissipation capacity. The response of all six walls under cyclic loadings was controlled by 3–4 cracks formed at bed joints between the concrete masonry units, and their failure was dominated by flexure with the occurrence of slight shear sliding. The load-displacement envelope, strength, and energy dissipation of all tested MLRM walls are discussed.