Concrete Crack Control Research Articles

Experimental Investigations on the On-Site Crack Control of Pier Concrete in High-Altitude Environments

Concrete structures in high-altitude environments face many challenges. Establishing concrete crack control methods in high-altitude environments is crucial for enhancing the service capacity of concrete structures. In this study, a multi-field (hydration-temperature–humidity-constraint) coupling model was used to quantitatively assess the cracking risk of pier bodies at high altitude. On-site crack control tests were conducted on pier bodies using a micro-expansion anti-cracking agent to demonstrate the effectiveness of deformation shrinkage compensation in crack control at high altitudes. The results indicated that there was a risk of cracking in the pier body at high-altitude conditions, especially within 0.3 m from the pile cap and ±2.5 m from the center of the pier side surface. Compared with conventional piers, the micro-expansion anti-cracking agent approximately doubled the unit expansion deflection of piers at high temperatures while reducing the unit shrinkage deflection of piers by 11% to 12% at low temperatures. The concrete in conventional pier bodies was in a tension state after long-term hardening, while the concrete treated with the micro-expansive anti-cracking agent was in compression. Therefore, the deformation compensation effect of the micro-expansive anti-cracking agent was significant and reduced the risk of concrete cracking. In addition, early freezing had a significant impact on concrete strength, underscoring the importance of effective temperature control during the early stages of concrete placement in high-altitude environments.

Effect of multi-scale reinforcement on fracture property of ultra-high performance concrete

This paper aims to achieve multi-scale crack control of concrete by using graphene oxide (GO) and macroscopic steel fiber in combination, and to reveal the multi-scale collaborative reinforcement mechanism of GO and steel fiber. A three-point bending fracture mechanics test was employed to analyze the macroscopic fracture properties of ultra-high performance concrete (UHPC) reinforced by GO, and a single fiber pull-out test was utilized to assess the impact of GO on the fiber–matrix interface properties. The results showed that 0.04% GO reinforced UHPC had the best fracture property, and steel fiber and GO showed good synergistic crack control effect. GO directly acted on controlling the cracking of concrete matrix at the nanoscale, thus improving the fracture energy of UHPC matrix by 14% from 73.08 N/mm to 83.39 N/mm. This micro-scale matrix reinforcement provided by GO further improved the pull-out property of steel fibers, and the pull-out energy dissipation of straight steel fibers and hook-end fibers was increased by 43.7% and 31.5%. A micromechanical prediction model for fracture energy of straight steel fiber UHPC was established, which could construct the quantitative relationship between UHPC fracture energy and micromechanical parameters. The model showed that the initial fiber–matrix bond strength (τ0) and slip hardening coefficient (k0) had a powerful influence on the UHPC fracture energy.

Experimental and numerical investigation of lightweight foamed reinforced concrete deep beams with steel fibers

This paper aims to experimentally and numerically study the effect of steel fiber on the behavior of Lightweight Foamed Reinforced Concrete (LWFRC) deep beams and its mechanism to improve the mechanical properties and crack control of concrete. In addition to this, steel fibers compensate for the lack of resistance due to the use of lightweight foamed concrete (LWFC). This paper will also address the effect of some variable parameters on the structural behavior such as: (1) volume of fiber; (2) fiber aspect ratio; (3) longitudinal reinforcement ratio.The experimental program consists of four groups; each group comprises two beams compared to the control specimen. All beams have an overall depth of 800 mm, width of 150 mm, and total length of 2200 mm with span of 2000 mm. Tests were performed under two points load with constant shear-span to depth ratio equal to one. The used LWFC has an average cubic, cylindrical compressive strength and splitting tensile strength of 33, 28 and 3.10 MPa, respectively. Hooked end steel fibers with length 40, 50, and 60 mm and 0.8 mm diameter were used with 0%, 0.5%, 0.75% and 1.0% volumetric ratio.The obtained results indicated that the cracking and the ultimate load has increased by 18.5% and 25.5%, respectively due to use steel fibers. Furthermore, the displacement ductility and toughness has increased by 38% and 56%, respectively. The failure mode of LWFRC deep beams is shear brittle failure.Shear capacity of all deep beams based on ECP 203–2017 (ECP-203, 2017) is calculated and compared with that from ACI 318–19 (ACI 318-19, 2018) which is based on strut and tie model (STM). Comparing the experimental results with STM results showed that ECP 203–2017 (ECP-203, 201) is slightly conservative in calculating the ultimate capacity than ACI 318–19 (ACI 318-19, 2018) for the range of the studied variables in this research and not in general. Finally, as the STMs are debatable, ANSYS 15 software was used to numerically study the behavior of LWFRC deep beams. Verification of numerical models has been done by comparing the results of the load deflection curves, cracks and ultimate loads with the experimental ones.

Experimental and Analytical Study on Pull-out Force of Steel Fiber-Reinforced Concrete Blocks

Reinforcing bar bonding in concrete is essential for reinforcing bar anchoring and reinforced concrete cracking control. A pull out test of a reinforcing bar embedded in a concrete block is commonly used to determine it. When compared to plain concrete, steel fiber enhanced the mechanical properties of reinforced concrete. This paper presents experimental and analytical study on pull-out force of steel fiber-reinforced concrete blocks. Experimental program consists of six specimens. Two parameters are considered in this study, which are steel bar diameter and content of steel fiber. The numerical analysis was conducted by the finite element ANSYS software and was carried out on the experimental specimens. An analytical analysis was conducted to investigate the developing of the shear stress in surrounding concrete in XZ-plan and stresses in steel bar. Test results show that the steel fibers had significant influence on the increase of the pull-out force. The pull-out force increased by 3%, 4% and 15%, for CS1, CS2 and CS3 compared with specimens without steel fiber C1, C2, and C3 respectively.

Analysis of Concrete Crack Control in Subway Construction

Analysis of Concrete Crack Control in Subway Construction

Probability-Based Crack Width Estimation Model for Flexural Members of Underground RC Box Culverts

Crack control for slabs and beams in current design practices in Korea are based on the Frosch’s model, which is adapted in ACI 318. It is more difficult to have consistent quality control in underground construction sites, such as the RC box culverts used for electric power distribution built below the ground level. There are more discrepancies between the as-built dimensions and the design dimensions provided in drawings in these structures. Due to this variability in construction error, the crack widths measured in such structures have higher potential to have more differences than the calculated values. Although crack control is a serviceability concern, if the owner chooses to have a target crack width that needs better control, crack width estimations can be improved by considering such construction variability. The probability-based crack width model suggested in this study will allow minimizing the discrepancies between the measured and calculated crack widths and provide reliable estimations of crack widths. Typical size of slabs and beams ranging between 300 mm (12 in.) to 500 mm (20 in.) used in underground RC box culverts in Korea were tested under the four-point bending test program. The thicker specimens had smaller bar spacings which created more cracks with smaller crack widths. However, with smaller crack widths generated in these specimens, there were more errors between the measurements and calculated values. From site investigations in Korea, the thickness of slabs in underground box culverts varied the most among all parameters. As a result, the bottom concrete covers had the highest variability. Bottom concrete covers and bar spacings are the two most important parameters in concrete crack control. A probability-based crack width estimation model for flexural members was developed in this study to consider this construction variability. Monte Carlo simulations were performed to evaluate the probabilistic characteristics of the design surface crack widths with a target width of either 0.3 mm (12 mils) or 0.5 mm (20 mils). The probabilistic models of design variables included in the crack width estimation model were generated based on field-collected information from construction sites in Korea. Because the surface crack widths in RC flexural members are sensitive to the construction errors of concrete cover depths, and since there are differences between the assumed and actual stress distribution closer to the reinforcing bars, the probability of having surface cracks of 0.3 mm width (12 mils) is found to be quite high, such as 89% at the positive moment region (mid-span, bottom surface) of the top slab in RC box culverts and 45% for the negative moment region (support area, top surface) of the top slab with current design practice. In order to ensure crack widths to be smaller than the design target width, probability-based crack width factors are recommended in this study to improve estimations depending on the selected target reliability levels.

Analysis of Concrete Crack Control Technology in Water Conservancy Construction

Analysis of Concrete Crack Control Technology in Water Conservancy Construction

Study on the Concrete Crack Control in Subway Civil Construction

Study on the Concrete Crack Control in Subway Civil Construction

Discussion on Concrete Crack Control Technology in Water Conservancy Construction Engineering

Discussion on Concrete Crack Control Technology in Water Conservancy Construction Engineering

Finite Element Analysis on Lining Structure of Diversion Tunnel in a Hydropower Station

Aiming at the high internal and external water pressure tunnels built in unfavorable geological bodies, this study proposes a novel type of composite support structure in which steel plates are poured inside concrete linings. Compared with traditional structures, it has the advantages of higher tensile strength, better crack resistance, and impermeability. Taking the diversion tunnel of a hydropower station as an example, based on linear and non-linear finite element simulations, mechanical properties of the steelconcrete composite lining structure for a hydraulic tunnel in soft surrounding rocks are analyzed. On this basis, the concrete crack control under this supporting condition is verified. Research results can provide a reference for the selection of reasonable steel plate thicknesses and reinforcement types in design.

Concrete Cracking Control of Chamber wall in Jiepai Ship-lock Project

Based on analysis of crack problem of chamber wall ship lock expansion project in Jiepai province, the related research of countermeasures have been made, to solve the cracks occurs in the structure. The countermeasure of cracks are analysed by monitoring internal-external temperature and shrinkage stress of chamber wall. It is provided that the rational measures could make less cracks occur, including fiber lattice with curing of insulation and moisture materials and optimization of proportion mix. A series of investigations are carried out insitu and prove countermeasures of cracking control effectively. This paper states the technical details and developing of inner temperature and shrinkage in chamber wall by adopting above measures.

A comparative study of combined treatments for enhanced early-age cracking control of self-consolidating concrete

Concrete bridge deck and other concrete civil structures often experience severe early-age cracks, mainly due to thermal and shrinkage stresses during concrete curation and hydration. Nowadays, several treatments for crack control of concrete (e.g., the incorporation of PP fiber, internal curing materials, or expansive agent) have been proposed and proved effective, but there are very limited studies on the combined effect of PP fiber, internal curing material and expansive agent. Therefore, this study tended to provide a comprehensively comparative investigation of individual treatment and their combined effects on effectiveness of crack control. A total of 18 mixture proportions of self-consolidating concrete (SCC) with different ratios (or dosages) of three treatments were designed and were quantified for their early age cracking control. The results showed that the combined treatments provided different perspectives for effectively cracking control for SCC samples, as compared to individual ones. The results demonstrated that either PP fiber with EA or LWA with EA offered considerably improved cracking control, as compared to those of individual treatments. Particularly, when at low PP fiber content (i.e., 0.05% vol.), the cracking control of SCC was significantly improved to a certain extent with increase of LWA ratio. However, at higher PP fiber content of 0.1% vol., LWA did not show significant effect on improving concrete cracking control.

Improvement of Mechanical Properties of Concrete by Using Polyproplene Fibers and Admixure

Concrete is considered a low tensile resistance material and a weak material against cracking. The weak properties of concrete has been enhanced by utilizing fibers to reinforce it. In this research, the effects of the polypropylene fibers on several properties of plain concrete have been studied. It was found that the polypropylene fibers has enhanced the concrete ductility and the concrete crack control. The compressive strength of plain concrete has been increased by adding polypropylene fibers to it and also the flexural and splitting strengths. The best results were at fibers ratio of 1%. When the polypropylene fibers ratio has changed different effects on concrete properties have been obtained.

THE MYTH OF SAW-CUT JOINTS IN CONCRETE SLABS AND WALLS

This paper is concerned with the world-wide practice of providing shallow saw-cut joints or v-grooves at regular spacing, for structural purposes, in concrete walkway slabs, slabs-on-grade, and parapet walls. The primary purpose of this paper is to raise awareness among engineers that the practice is a myth and has no structural advantages, and for the engineers to think of a better and more positive/reliable approach to concrete crack control. The other purpose is to make aware the need for engineers to think and observe actual behavior of existing structures, and use that observation to improve future design, and not repeat unsound or useless practices. Elimination of useless saw-cut joints in future construction would save the whole world billions of dollars. The author demonstrates that the saw cuts have no structural impact by showing the pictures taken in New York of typical cracks seen on walkway slabs and parapet walls, and on garage floor slabs that were built with saw-cut joints. Note that this type of actual field observation is more representative than the crack observation on small concrete models tested in any engineering laboratories. For comparison, the author shows the examples of crack-free, maintenance-free garage floor slabs and parapet walls without any saw cuts that have been in service in Thailand for the past 30 years.

Finite element simulation of prevention thermal cracking in mass concrete

The mass concrete structures play a very important role in civil engineering. The cracking of concrete is regarded as one of the biggest engineering problems. Therefore, it is very necessary for the cracking of mass concrete to do the control analysis. Some factors should be considered in mass concrete crack control analysis, mainly including the heat releases model of concrete, the mechanical model to the concrete, the process of temperature control in the pipe model. Differential evolution algorithm and equivalent algorithm are adopted to solve the coefficient of adiabatic temperature and cool water effect. In the paper, stress field calculation, back analysis calculations, and cooling pipe processing create secondary development based on the ABAQUS software platform. The second development of the code is used to reasonably solve the problem with one actual aqueduct in hydraulic engineering.

Effective Crack Control of Concrete by Self-Healing of Cementitious Composites Using Synthetic Fiber.

Although concrete is one of the most widely used construction materials, it is characterized by substantially low tensile strength in comparison to its compression strength, and the occurrence of cracks is unavoidable. In addition, cracks progress due to environmental conditions including damage by freezing, neutralization, and salt, etc. Moreover, detrimental damage can occur in concrete structures due to the permeation of deteriorating elements such as Cl− and CO2. Meanwhile, under an environment in which moisture is being supplied and if the width of the crack is small, a phenomenon of self-healing, in which a portion of the crack is filled in due to the rehydration of the cement particles and precipitation of CaCO3, is been confirmed. In this study, cracks in cementitious composite materials are effectively dispersed using synthetic fibers, and for cracks with a width of more than 0.1 mm, a review of the optimal self-healing conditions is conducted along with the review of a diverse range of self-healing performance factors. As a result, it was confirmed that the effective restoration of watertightness through the production of the majority of self-healing products was achieved by CaCO3 and the use of synthetic fibers with polarity, along with the effect of inducing a multiple number of hairline cracks. In addition, it was confirmed that the self-healing conditions of saturated Ca(OH)2 solution, which supplied CO2 micro-bubbles, displayed the most effective self-healing performance in the surface and internal sections of the cracks.

Concrete integral abutment bridges with reinforced concrete piles

AbstractThe use of reinforced concrete (RC) piles in integral abutment bridges (IABs) has not been widespread due to concerns over pile flexibility and the potential for concrete cracking. This is the reason why the use of steel piles is the preferred solution in the United States. However, in various countries where IABs are still seldom used, RC piles are more readily available and economical. Hence, an understanding of the behaviour of IABs with RC piles can lead to a wider implementation of integral solutions. This paper presents the results of a parametric study conducted to evaluate how both the design variables and the accuracy of the modelling approach influence the potential use of integral solutions with RC piles in prestressed concrete bridges up to 200 m long. Finite element modelling was used and four levels of approximation (LoA) were established for the analyses, ranging from simple linear‐elastic to more complex non‐linear models. The results show that existing concerns over concrete cracking control can be overcome if adequate options in design are used together with the adequate LoAs in structural analysis. Integral solutions with RC piles for bridges up to 200 m long can generally be adopted, although in comparisons with non‐integral designs a significant additional amount of prestressing steel is to be expected. The results also include a set of charts with practical estimates to help designers in their first approach to the preliminary design of an IAB.

Crack Control Technology for Concrete of Super-Large Section Precast Immersed Tube

As the complex structure, large size, hot climate, aggressive corrosive environment and high concrete strength grade for Super-large Section Precast Immersed Tube of Hong Kong-Zhuhai-Macao Bridge, crack control of concrete was difficult. On the basis of simulating analysis on thermal stress, temperature control design was carried out. Harmful crack could be effective controlled by series of treatment measures during construction period such as optimization of raw materials, preparation of low heat and shrinkage concrete, controlling concrete raw material temperature, mixing concrete with ice shavings and cooling water, setting up automatic maintenance system and automatic temperature monitoring system. From the monitoring results, the temperature monitoring results were consistent with the simulation data, and the maximum temperature and the temperature difference between concrete surface and internal concrete were met the requirement of temperature control standard. Moreover, the precast immersed tube didn’t appear harmful crack.

Research on early Concrete Crack Control of Shijiazhuang Subway Construction in Winter

The control of concrete cracking is a complicated and difficult problem for civil engineering. It is more difficult to control the cracking of the concrete poured in the winter. Thorough the analysis of the construction of the Shijiazhuang subway in winter, several methods are integrally applied. Frost proof and decreasing the temperature stress of concrete is considered together. The construction quality of the concrete arrive a satisfied level and the cracking of the concrete is successfully handled.

Concrete Crack Control in Monolithic Concrete Bed Construction of High-Speed Railway in Northwest Area of China

There were some reasons which cause the concrete cracks in monolithic concrete bed construction of high-speed railway. In this paper, combined with the specific situation of monolithic concrete bed construction of high-speed railway in northwest area of China, the states and causes of two kinds of cracks in monolithic concrete bed of high-speed railway were analyzed, the concrete cracking control measures were discussed from the concrete mixture ratio, construction technology and maintenance measures and other aspects, and the corresponding views were put forward. The study results had the important guiding significance on crack controls of concrete structure during the construction process of northwest area.