Mortar Injection Research Articles

Effectiveness of mortar injection repair activity on an existing prestressed bridge girder

This paper reports the results of an experimental test performed on a prestressed reinforced concrete bridge girder, extracted from an existing bridge of the Italian highway network. The element exhibited cracks damage along the curved tendons of the prestressing system, probably due to the rainwater infiltration into the protecting duct. The experiment consists of a three-point bending test, where a point vertical load is located at mid-span and cyclically increased until bending collapse occurs. Before the test, the cracks pattern has been repaired by high-pressure injection of high-resistance mortar. The test results demonstrate the effectiveness of the mortar injection repair intervention.

Identification and Mitigation of Subsidence and Collapse Hazards in Karstic Areas: A Case Study in Alcalá de Ebro (Spain)

Sinkholes are a severe problem in urban areas located in karstic regions, especially where evaporitic rocks such as gypsum exist. Identification and proposal of mitigation measures are needed to reduce this geo-hazard effect on buildings and social urban living. This paper presents a case study of the town of Alcalá de Ebro (Spain), which is located in the highest sinkhole risk region of Europe. The identification and mitigation of a series of sinkholes that appeared are analyzed. The former involves a geological investigation, including boreholes, field tests and geophysics. The latter is addressed by the use of geogrids, mortar injections and polyurethane injections. A complementary finite element analysis is carried out to set the ground behavior associated with the sinking process and assess its future evolution. The Ebro River appears to be the main cause of sinkholes, and results show that ground treatments applied were successful in their purpose, as there are no apparent deformations indicating that the subsidence or sinking process is still active in the area. The use of different techniques depending on the size of the sinkhole, the objectives pursued and the element affected is discussed.

Experience of strengthening the soil base with parallel lifting of the foundation structure

The article shows the positive experience of fixing the soil base and strengthening the foundation with the parallel restoration of the normative state of the underground and above-ground structures of the facility. The accidents at the considered objects is caused by the formation of significant voids under the foundation. Foundations at the objects are represented by monolithic reinforced concrete slab and strip. Recommendations are given on the development of design solutions, organization of work, and the compositions of injection mortars are analyzed. Injection compositions were presented on the basis of cement and sand-cement mixture, the argumentation of the use of these compositions on specific engineering-geological conditions is given. Stabilization of the foundation was additionally made by strengthening with "Atlant" piles. The variants of the object geometric position correction by mortar injection into the contact layer and into the active soil strata are presented. The development of a reliable solution for reinforcement is possible only if there are an accurate data of the geotechnical conditions of the construction site, a detailed visual and instrumental survey of building structures. The processes of fixing soil foundations with parallel lifting of underground and above-ground structures are provided today with the necessary level of equipment development. However, it is necessary to ensure its technologically correct use, adapted to a specific situation. The options for solving emergency situations considered in the article can be used as proven design solutions at facilities with similar engineering and geological conditions and foundation structures.

The sands of medium density and sandy loam density differences investigation while cement injection and pressuremetry crimping

The article focuses on the study of medium density sand and sandy loam density changes during water-cement solute injection and pressiometer expansion. Cement mortar injection is performed into boreholes under small pressure of up to 300 KPa resulting in radial well expansion. This expansion process also takes place during pressiometer studies. A cavity of compacted soil is formed around the expended boreholes in radial direction; the anchor and pile load determine field studies of the load, which they can perceive along lateral surface. It is worth noting that they frequently do not coincide with the calculated values. Following field anchor excavations, it was observed that root shearing can occur both directly at the contact between the cement root and the soil and at some distance from it. Subsequent laboratory studies revealed that when the soil is pressed, its density can change along a sinusoid, comprising pressed zones and decompaction zones. This gives rise to the displacement of the shear zone at the contact between the root and the soil.

Enhancement of Bond Performance of Advanced Composite Materials Used in Cable Bridge Structures Based on Tensile Tests.

Structural steel and concrete are essential materials for the construction of social infrastructures. However, these materials undergo degradation over time, thereby causing steel corrosion. To address this problem, a fiber-reinforced polymer (FRP) is used for reinforcement. In this study, tensile tests were performed to evaluate the material properties for the application of the FRP to cable bridge structures. These tests aimed to investigate various parameters to improve bond performance. Based on experiments with different parameters, sufficient bond performance could be achieved if the following conditions are met: mortar water ≤16%, regardless of the manufacturer; a depth of splitting and steel pipe length ratio ≥75%; upward/downward directions for the mortar injection; and the use of fiber-sheet reinforcement. In addition, the steel pipe used in the test (length of 410 mm and outer diameter of 42.7 mm) performed the best in terms of workability and cost effectiveness. By conducting more accurate tests to study the basic properties of materials, more accurate conditions to accomplish sufficient bond performance can likely be achieved. This will contribute to improved cost effectiveness and safety in the use of carbon FRP cables in cable bridge constructions.

STRESS-DEFORMED STATE OF THE FOUNDATION OF HYDRAULIC STRUCTURES AT CONTROLLED COMPENSATION DISCHARGE

Nnumerical simulation of the process of injection of mortar into the thickness of the sandy base during the work on lifting and leveling the structure by the method of compensatory injection is carried out. An author's program has been developed that implements the finite element method (FEM) in a spatial formulation, taking into account the elastic-plastic nature of soil deformation, in which a special element in the form of a spheroid has been developed to describe the expanding area at the location of the injector, which changes its volume during the injection of mortar. During the verification of the program, the results of mathematical modeling were compared with the data of a physical experiment conducted by PhD Luca Masini from the University of La Sapienza (Rome, Italy). Numerical modeling of the stress-strain state of the base of the structure during repair work is considered by the example of lifting the foundation plate of the Zagorskaya PSPP-2. A number of tasks are being solved related to minimizing the number of injection columns, their location, the pitch of the cuffs, the selection of portions of the injected solution, taking into account the requirements for uniform lifting of the foundation plate in order to avoid additional cracking.

The use of piles with an adjustable operation mode to restraint the shaft sinking systems’ supporting structures

The article deals with the problem of ensuring the stability of grillages and pile foundations used to hold shaft sinking systems during the construction of vertical subway shafts. The features of such foundations’ operation in the process of shaft sinking are investigated, in contrast to similar structures that receive pressure from a building under construction. The importance of taking into account the mutual influence of shaft sinking and pile foundations of the shaft sinking systems’ supporting structures is shown. The design of bored piles and the technological scheme of mortar injection are proposed, which provide a change in the operating mode of pile foundations and regulation of its bearing capacity.

Fiber Reinforced Cementitious Matrix (FRCM) for strengthening historical stone masonry structures: Experiments and computations

Seismic events highlight the inherent fragility and vulnerability of stone masonry buildings, which represent a large part of the existing historical and artistic heritage. In order to preserve these structures, numerous reinforcement techniques are typically used on masonry walls, including mortar injections, reinforced drilling, and reinforced concrete plaster. Nowadays new and less invasive strengthening techniques are preferred; among them Fiber Reinforced Cementitious Matrix (FRCM) system with lime-based mortar, which is considered to be more compatible with the intrinsic properties of these ancient structures as compared to cement-based mortar. This work aims to investigate experimentally and computationally FRCM applied as reinforcement to ancient stone masonry. In particular, the paper presents results from diagonal compression tests carried out at the University of L’Aquila (Italy) on stone masonry specimens strengthened with layers of Glass-FRCM (GFRCM). In comparison with unreinforced panels, those strengthened by the GFRCM exhibited a significant increase in shear modulus and shear strength. A computational framework based on the Lattice Discrete Particle Model (LDPM) was then used to reproduce the experimental results. The fracture behavior and the damage evolution in masonry panels were investigated under different assumptions on the GFRCM system features (bond behavior, mortar thickness, fiber anchors and fiber grid). The good agreement between experimental results and the LDPM simulations show that this approach predicts well the mechanical behavior and the damage evolution in stone masonry under quasi-static loading conditions. Moreover, it can be considered a viable tool for engineers in developing effective reinforcement techniques.

Complex resistivity survey for the evaluation of ground reinforcement in a karst area

A complex resistivity (CR) survey was used to evaluate ground reinforcement following the injection of mortar, which is rich in clay minerals known to show strong induced polarization effects. CR surveys were used to determine the distribution of injected mortar along six survey lines parallel to a road in a karst area in Yongweol-ri, Muan-gun, Korea, which had suffered from ground subsidence and had been reinforced. CR data were collected at 0.125 Hz along each survey line and inverted to find two phase anomalies. We show that the phase anomalies indicate the accumulation of injected mortar. This interpretation was confirmed according to the amount of mortar injected at each borehole, and the time-lapse (TL) direct current data obtained during the reinforcement process. Furthermore, the CR data were three-dimensionally inverted, with the results compared to those of a two-dimensional (2-D) inversion, to demonstrate that 3-D inversion can provide more detailed information than 2-D analysis. A CR survey is an effective tool to determine the distribution of injected mortar.

Experimental studies on the moisture-dependent spread of injection agents

Additional horizontal sealing in mineral building materials often produce insufficient or varying results despite the application of the injection agent being carried out according to the manufacturers’ specifications. There is no current scientific explanation for this effect, which prompted this research. The main idea was to solve the question of whether the increasing filling of the capillary pores of mineral building materials with water (and therefore the degree of moisture penetration) can be connected to the varying spread of the injection agent. After developing a test procedure, different degrees of moisture penetration were applied to samples of bricks and mortar cubes and hydrophobic injection agents were applied to the test specimens. The results showed that the degree of spreading of the injection agent was inversely proportional to the degree of moisture penetration. Consequently there is a dependence of the above mentioned parameters (the existing degree of moisture penetration and the spr...

Reinforcement of the foundation base of the building with horizontal elements of increased rigidity

A method for reducing the uneven deformations of a two-story building, which provides improving the construction properties of weak soils that lie at the base, by reinforcing them with horizontal soil-cement elements (SCE) of increased rigidity, carried out using a sand mixing technology, is described. SCEs are created in the mass under the base of the foundations and are formed as a result of the destruction of soil natural structure with its simultaneous mixing and injection of cement mortar under pressure. It has been established that the manufacture of SCE has a number of advantages: using of local soil as a material for their manufacture; adding to the soil only water and a binder, without additional aggregate; installation of elements on the site.

Assessing preferential seepage and monitoring mortar injection through an earthen dam settled over a gypsiferous substrate using combined geophysical methods

For several decades the Sant Llorenç de Montgai reservoir has experienced different problems that could affect the safety of the engineering structure. For this reason, several corrective actions have been taken over the years. Here, we present a study involving complementary geophysical methods including electrical resistivity tomography, seismic refraction tomography and frequency-domain electromagnetic surveys.The analysis of the inverted electrical resistivity tomography cross-sections combined with the seismic refraction results and land subsidence monitoring data show the likely mechanism of abnormal seepage. The areas where mortar injections were applied as a corrective measure are also clearly delineated.In addition, the evolution of the state of the embankment has been established from two successive electrical resistivity tomography surveys in the last two decades. The results show areas where corrective mortar injections have been effective, while in other areas new abnormal seepage has been detected.The lithological heterogeneity of the bedrock, especially the dissolution of gypsum-rich rocks, induced subsidence effects and caused abnormal seepage in different areas along the embankment. Our results indicate how corrective solutions can be optimized to reduce the cost of corrective engineering interventions.

Effect of daily changing temperature on the curling behavior and interface stress of slab track in construction stage

Interface damage, which even happens in construction phase, has become a major problem for China Railway Track System (CRTS-II) slab track. The slab track in construction stage is a block structure and sensitive to daily changing temperature. In order to reveal the temperature behavior of the slab track and provide meaningful information to the control of early interface damage, a three-dimensional finite element model of slab track was developed to study the deformation and interface stress of the slab track under daily changing temperature in this paper. The daily changing temperature was measured on a testing platform constructed in open field, and imported to the model using user-defined subroutines UTEMP. Based on the developed model, the effect of initial temperature and construction seasons were then investigated. The analysis indicates that the slab deformation and stress change with time obviously and the positions of maximum interface stresses are near the slab corner, which is consistent with the location of interface disease. Initial temperature has significant influence on the slab temperature behavior. The initial temperature at 14:00 induces the largest interface tensile stress exceeding the interface bonding strength, while the interface stresses are relatively small from 19:00 to 24:00. Therefore, it is suggested that CA mortar injection should be finished before midnight. Additionally, as the overall temperature variation and temperature gradient are very obvious in summer, spring and autumn, the grouting operation of CA mortar in these three seasons is required to pay equal attention.

EVALUASI SAMBUNGAN MUR-BAUT STRUKTUR PORTAL TRUSS “THE GREAT HALL” OBI ECO CAMPUS - JATILUHUR

Abstract- Bolt joint is one of the common joineries in a modern bamboo construction. The usage of the bolt joints in bamboo joinery are believed to be the most efficient therefore the bolt joint was used regardless of the various kind of different forces in every bamboo joinery. One of the disadvantage of the bolt joints in bamboo construction in the force that flow parallel to the bamboo fibers therefore some of joineries needed to be strengthen to prevent the joinery failure. The Great Hall OBI Eco Campus is one of the building which the joineries entirely connected by the bolt joints, through different forces in every joinery some of the joinery in the building are strengthen by rope. The bolt joints have many other combinations to strengthen the joinery that could be an option, they are bolt joint with clamping and with mortar injection. Key Words: Bolt Joint, parallel forcee to the bamboo fiber, strengthen by rope, “The Great Hall” OBI Eco Campus, Clamping, Mortar Injection

Estimates for the stiffness, strength and drift capacity of stone masonry walls based on 123 quasi-static cyclic tests reported in the literature

This paper summarises 123 existing quasi-static shear–compression tests on stone masonry walls and evaluates the results to provide the input required for the displacement-based assessment of stone masonry buildings. Based on the collected data, existing criteria for estimating lateral strength and stiffness of stone masonry walls are reviewed and improvements proposed. The drift capacity of stone masonry walls is evaluated at six different limit states that characterise the response from the onset of cracking to the collapse of the wall. To provide input data for probabilistic assessments of stone masonry buildings, not only median values but also the corresponding coefficients of variation are determined. In addition, analytical expressions that estimate the ultimate drift capacity either as a function of masonry typology and failure mode or as a function of masonry typology, shear span and axial load ratio are proposed. The paper provides also estimates of the uncertainty related to the natural variability of stone masonry by analysing repeated tests and investigates the effect of mortar injections and the effect of the loading history (monotonic vs cyclic) on stiffness, strength and drift capacities. The data set is made publicly available.

Generation of stress-strain state in combined strip pile foundation beds through pressing of soil

When erecting high-rise buildings, weak underlying soils cause a number of problems in design and construction. In order to ensure the required non-exceedance of the ultimate limit settlements, the combined strip pile foundation has been developed allowing the soil bed to be pre-stressed. This is achieved by injection of pressurized mortar (pressing). The paper analyzes the effect of soil pre-stressing followed by pressing of foundation with the cement mortar, as applied to existing structures using the Plaxis 3D software package in conditions of volume deformation and the Hardening Soil Model. Variable order of foundation pressing allows the required parameters of soil bed to be achieved in plan and depth, thus improving interaction with the foundation and superstructure.

EXPERIMENTAL AND NUMERICAL INVESTIGATIONS ON HISTORICAL MASONRY WALL SPECIMENS TESTED IN SHEAR-COMPRESSION CONFIGURATION

The paper presents the experimental investigation carried out on wall specimens reproducing the ancient masonry of several monumental building located in the old city centre of L'Aquila (Italy) and damaged by the April 2009 earthquake. The wall specimens were prepared in accordance with the traditional technique, using original stone elements and typical poor mortar. Subsequently, the specimens were consolidated with mortar injections. Other specimens were also reinforced with Ultra High Tensile Strength Steel wires applied as coating technique (not wrapped). Shear-compression tests were carried out on the wall specimens to evaluate the effects of the reinforcements both in terms of final stiffness and strength of the specimens. A non-linear Finite Element Model (FEM) was developed to reproduce the experimental tests and to better understand the damage phenomena. The load-displacement curves predicted by the FEM compared quite well with the experimental ones. The failure mode of the specimens was properly captured by the FEM. The effectiveness of the external reinforcement was proved to strictly depend on the coating adhesiveness to the walls surface. The premature debonding of the external reinforcement was demonstrated to cause the fragile post-peak behaviour during both the actual experimental test and the numerical simulations.

Recent Development and Application of Polymers in Concrete Technology in Singapore

Polymer has been extensively used in construction in Singapore during the past few decades and has become a necessary component of some building materials including polymer modified cement mortar, epoxy or Polyurethane (PU) floor screed and injection materials, and fiber-reinforced plastic (FRP) materials. Compare with conventional concrete, polymer concrete composites may achieve remarkable advantages, such as high tension, high flexural strength, high ductility, ability to absorb energy, and high resistance to chemical attack, corrosion, freezing and thawing, and consequently gain more research interest for the scientific community. There are numerous possibilities for incorporation of these materials, such as latex, natural resources, fibers, nanomaterials and laminates. The presence of polymer makes it suitable for wide applications. The various categories of polymer concrete composites are widely used in Singapore’s public and private projects. To ensure and maintain the high standards of the building quality, independent testing and inspection plays a very important role. The present paper reviews recent research and development activities, and applications of polymer concrete composites in Singapore. The innovations and new approaches are reviewed. The development of the requirements and specifications for various polymer concrete composite products are described and discussed. The effect of different factors on the polymer concrete composite and material selection are also described. In addition, the paper also outlines the methods and measures used to inspect and control the quality of application.

LCA-based study on structural retrofit options for masonry buildings

Over the last decade, the rehabilitation/renovation of existing buildings has increasingly attracted the attention of scientific community. Many studies focus intensely on the mechanical and energy performance of retrofitted/renovated existing structures, while few works address the environmental impact of such operations. In the present study, the environmental impact of typical retrofit operations, referred to masonry structures, is assessed. In particular, four different structural options are investigated: local replacement of damaged masonry, mortar injection, steel chain installation, and grid-reinforced mortar application. Each different option is analyzed with reference to proper normalized quantities. Thus, the results of this analysis can be used to compute the environmental impact of real large-scale retrofit operations, once the amount/extension of them is defined in the design stage. The final purpose is to give to designers the opportunity to monitor the environmental impact of different retrofit strategies and, once structural requirements are satisfied, identify for each real case the most suitable retrofit option. The environmental impact of the structural retrofit options is assessed by means of a life-cycle assessment (LCA) approach. A cradle to grave system boundary is considered for each retrofit process. The results of the environmental analysis are presented according to the data format of the Environmental Product Declaration (EPD) standard. Indeed, the environmental outcomes are expressed through six impact categories: global warming, ozone depletion, eutrophication, acidification, photochemical oxidation, and nonrenewable energy. For each retrofit option, the interpretation analysis is conducted in order to define which element, material, or process mainly influenced the LCA results. In addition, the results revealed that the recycling of waste materials provides environmental benefits in all the categories of the LCA outcomes. It is also pointed out that a comparison between the four investigated options would be meaningful only once the exact amount of each operation is defined for a specific retrofit case. This paper provides a systematic approach and environmental data to drive the selection and identification of structural retrofit options for existing buildings, in terms of sustainability performance. The final aim of this work is also to provide researchers and practitioners, with a better understanding of the sustainability aspects of retrofit operations. In fact, the environmental impacts of the retrofit options here investigated can be used for future research/practical activities, to monitor and control the environmental impact of structural retrofit operations of existing masonry buildings.

Review on Application of Polymer Concrete in Singapore

Singapore is a small island country, but has won renown as uncorrupted government and high quality products. Independent testing and inspection played a very important role for this achievement[1]. The Housing and Development Board (HDB) is the sole public authority in Singapore and was set up as a statutory on 1 February 1960. Within 45 years, it built more than 700,000 flats housing approximately 86% of the population. Every year, around 40,000 new flats (about 400 blocks) are built up to meet the demands. In March 1992, HDB launched the 15-year main upgrading programme (MUP) to vying the finishes and facilities of old estates up to the standard of those in the new towns. The upgrading programme is a conscious effort by the government to provide a better living environment, strengthen existing community ties and enhance the value of our flats. The potential size of the upgrading program is approximately 370,000 units spread across 20 years, which works out to be 350 blocks per year. To ensure and maintain the high standards of the housing quality, Polymer concrete materials including polymer modified cement mortar, epoxy or PU floor screed and injection materials, and fibre-reinforced plastic (FRP) materials are extensively used in the new and upgrading projects. In this paper, the various applications of polymer concrete composites in Singapore are described and discussed. The various categories of polymer concrete composites are extensively used in Singapore’s public and private projects. To ensure and maintain the high standards of the building quality, independent testing and inspection plays a very important role. Through implementing a quality control program to ensure high standards in product quality and performance requirements, Housing & Development Board (HDB), Singapore's public housing authority and statutory board under the Ministry of National Development, screens and provides a comprehensive selection of quality products needed for HDB construction projects through HDB's Materials List [2] with a set of product evaluation requirement. The development of the requirements and specifications for various polymer concrete composite products are also described and discussed