Use Of Grout Research Articles

Method and experimental study of strengthening circular hollow section T-joints by partial filling with cementitious materials

Circular hollow section truss joints may need to be strengthened for various reasons. This study evaluated a new method for strengthening such joints by partially filling the chords with cementitious materials, including grout and mortar. Taking T-joints as an example, the proposed strengthening process was described and experiments were conducted on six joints (four strengthened and two unstrengthened) under axial compression or tension applied to the braces. The failure modes and structural behaviors of the joints before and after strengthening were compared, and the effects of the strengthened length, filling material, direction of brace loading, and presence of temporary openings in the chord on the performance of the T-joints were investigated. The results demonstrated that: the strengthening method was viable and effective, the T-joint filled with 1d0 grout (mortar) exhibited a 70% (33%) improvement in initial stiffness and a 50% (36%) improvement in ultimate loading capacity; the use of grout was more efficient and convenient for construction than mortar; the initial stiffness and ultimate loading capacity of the strengthened T-joint was also improved when the brace were under tension; the temporary openings cut in the chord during the strengthening process had a little effect on the performance of the T-joint, with reductions of 11% and 9% in initial stiffness and ultimate loading capacity, respectively. Thus, the performance and safety of the joints can be ensured if reasonable design and protection measures are implemented.

LABORATORY INVESTIGATION OF THE EFFECT OF SODIUM SILICATE AND BENTONITE ON THE MECHANICAL PROPERTIES OF THE GROUT BEHIND THE SEGMENT IN MECHANIZED EXCAVATION

Nowadays, the use of Tunnel Boring Machines (TBM) in tunnelling has increased in urban environments. One of the effective parameters in the excavation process is the use of grout behind the segments to prevent ground settlement and penetration into the tunnel. The investigation of the effects of two-component grout (bentonite and sodium silicate) on the mechanical properties of the grout plays a crucial role in mechanized excavation. Therefore, this article aims to investigate the effect of various parameters on the properties of the two-component grout. Eight different mixing designs were considered in this research. Gel-time tests, viscosity test, water bleeding test, uniaxial compressive strength tests (UCS), and direct shear tests were conducted for each mixing design. The UCS tests were performed for eight mixing designs and at four different ages of the grout, while the direct shear test was conducted for five mixing designs at the age of one day. The results showed that increasing the sodium silicate content from 4% to 9.4% reduced the Gel-time to 7 seconds, and increasing the bentonite content from 2.3% to 4.58%, increased the marsh funnel time to 12 seconds. The uniaxial compressive strength of the grout increased to 0.682 MPa at the age of 28 days. Finally, by conducting the direct shear test on the grout and obtaining the parameters of cohesion and internal friction angle, it was determined that these two parameters depend on the values of bentonite and sodium silicate, and they change with the increase or decrease of these grout components.

Investigation of the deterioration mechanisms induced by moisture and soluble salts in the necropolis of Porta Nocera, Pompeii (Italy)

This paper focuses on the diagnosis of damage processes of decorative Roman renders of a group of tombs in the Porta Nocera necropolis in the ancient city of Pompeii, Italy. Unprotected from various climatic events, the tombs keep on deteriorating since they were first excavated in 1954. Extensive on-site and laboratory diagnostics using non-destructive and low-destructive techniques have been able to demonstrate that soluble salts are among the major agents of deterioration, causing damage in the form of render delamination. Gypsum is formed on the surface of the materials by the deposition of sulfur dioxide, resulting in reduced porosity and hardening of the surface. Soluble salts of nitrates and chlorides that penetrate the tombs’ masonry from the ground and are transported through the render layers tend to crystallize in subsurface. The crystallization—dilution cycles of the soluble salts cause major mechanical pressures, leading to the progressive destruction of the renders. Past conservation strategies to secure plasters have shown only limited effectiveness. In light of the data collected regarding salt decay, the authors propose new strategies, questioning the systematic use of grouts and restoration mortars for conservation treatments and focusing on preventive conservation and maintenance to ensure the long-term preservation of masonry and decorative surfaces of the tombs.

Influence of various design parameters of the grouted duct on mono-strand bond behavior in post tensioned members

There are many factors that may affect the concrete-strand and concrete-duct bond behavior in post-tensioned (PT) concrete slabs and beams. The importance of bond strength is to ensure a proper transfer of stresses from strands and ducts to the surrounding concrete. This research focused on bonded post-tensioned (PT) concrete elements, which includes the use of grout and ducts to provide the link between the strand and the concrete. The strength of the grout, the type and geometry of the ducts, and the embedment length of both strands and ducts were investigated through an experimental testing program to disclose the average interface shear stress within the embedded length of PT elements. This work helped in a better understanding of the bond behavior and the corresponding related parameters involved in the design process.

Optimal Support Solution for a Soft Rock Roadway Based on the Drucker–Prager Yield Criteria

Through theoretical calculation, the stress and deformation of surrounding rock can be analyzed, providing guidance for the support design and optimization of soft rock roadways. In this paper, theoretical solutions for both the optimal support pressure and the allowable maximum displacement of surrounding rock are derived from the Drucker–Prager (DP) yield criteria and the steady creep criterion expressed by the third invariant of deviator stress. The DP criterion with different parameters is compared and analyzed with an engineering example. Then, based on the calculation results the effects of long-term strength, cohesion, and internal friction angle of soft rock on the maximum plastic zone radius and allowable maximum displacement of roadway are discussed. The results show that the optimal support solution of soft rock roadways based on the DP criteria can not only reasonably reflect the intermediate principal stress but can also be used to compare and discuss the influence of different DP criteria on the calculation results. The higher the long-term strength of the rock surrounding a roadway is, the smaller the optimal support force is and the larger the allowable maximum displacement is. When the calculated long-term strength of soft rock can ensure that the deformation of the roadway does not exceed the allowable maximum displacement, the roadway can maintain long-term stability without support. With an increase in the cohesion or internal friction angle of soft rock, the radius of the plastic zone decreases gradually and the allowable maximum displacement is reduced by degrees. The use of grouting and other means to improve the strength of surrounding rock can effectively reduce the roadway deformation and save support costs. This new theoretical solution can consider different intermediate principal stress effects and different DP strength criteria, enabling the parameters to become easier to determine. It has a wider range of applications, and the calculation results better demonstrate the strength potential of the surrounding rock.

ОПЫТ ТАМПОНИРОВАНИЯ ШАХТНОГО СТВОЛА В УСЛОВИЯХ ПРОЯВЛЕНИЯ СОВРЕМЕННОЙ ГЕОДИНАМИЧЕСКОЙ АКТИВНОСТИ

The paper presents the results of studying of the effectiveness of water pressure in the shaft of a mine with the use of grouting are presented. The enclosing rock massif is character-ized by simple hydrogeological conditions and moderate manifestation of modern geodynamic activity. Despite the significant volume of the performed backfill measures, the expected result was not obtained due to the underestimation of modern geodynamic processes when choosing the backfill materials. In the conditions of a geodynamically active rock mass, the plugging ma-terial must retain plasticity throughout the entire period of operation.

Use of Grouting to Control Horizontal Tunnel Deformation Induced by Adjacent Excavation

A grouting technique is introduced as a measure to protect tunnels adjacent to a large-scale excavation. Field measurements indicated that this grouting technique reduced the maximum horizontal displacement in the tunnel from 9.2 to 4.6 mm. Based on this application and two field tests, the following recommendations are proposed: (1) the upper boundary of the grouted zone should be set at or below the tunnel; (2) grouting holes should be installed 3–4 m from the tunnel and at an interval of the length of a tunnel ring along the tunnel axis; (3) in a row of grouting holes, grouting should be conducted at an interval of six to eight holes in a day, and the grout volume per hole should be small, such as 0.5 m3; and (4) when using multiple rows of grouting holes, a far-row-first grouting scheme, in which the grouting sequence progresses toward the tunnel, should be adopted.

Proof of concept investigation of unbonded reinforcement in concrete block masonry

The use of grout in conventional reinforced masonry construction increases the cost and time of construction but allows walls subject to out-of-plane loads an enhanced ability to span between lateral support levels. An experimental investigation including a total of 21 walls was conducted in an attempt to identify potential alternatives to conventionally grouted walls. The strength and serviceability of walls containing unbonded reinforcement anchored at its ends was evaluated. All walls were two and a half blocks wide and 14 courses tall and were constructed in running bond using standard 200 mm concrete blocks. Six replicate unreinforced and partially grouted, conventionally reinforced walls served as control specimens. Walls with unbonded reinforcement were determined to be inherently stable with maximum loads approaching those of partially grouted, conventionally reinforced walls. If used in practice, these walls would need to be limited to indoor exposures due to the wide crack widths that develop.

Influence of the vertical grouting in the interface between corbel and beam in beam-to-column connections of precast concrete structures – An experimental analysis

The study of the connection between the elements in precast concrete structures is especially important since the performance of a structural system is directly related to such connections. In this context, an experimental study is presented to investigate structural behavior of a type of semi-rigid interior beam-to-column connection. The type of investigated connection is formed by a precast concrete beam supported on a precast concrete column corbel with the use of grout filling and bending continuity reinforcement bars crossing the column. The main purpose of this paper is to analyze the influence of vertical interface grout filling between the corbel and the beam on the behavior of this type of connection, when it is subjected to negative bending moment. Tests on four specimens were performed: two ones with vertical interface grout filling between the corbel and the beam and two ones without grout filling. The experimental results shown resistance adequate flexural strength capacity of the connections, which exhibited ultimate loads higher than the estimated by usual design of reinforced concrete sections. It was noticed that the vertical interface grout filling contributed to increase in rotational flexural stiffness and flexural strength capacity of the connections, around 5.05 times and 1.4 times, respectively, when compared to the connections without grout filling.

Utilização de graute como capeamento de corpos de prova de concreto para ensaio de resistência à compressão

The Portland cement concrete is the most consumed input in construction in Brazil, thus its quality deserves special attention when it comes to technological control. To assess this material, the compressive strength test is the most widely used. It is conventional the use of cylindrical specimens with dimensions of 10 cm by 20 cm. Due to failures during the molding process, observed in most of the civil works, it is necessary to perform a regularization in the specimen surface, to minimize possible failures during the compressive test. The literature review showed the different types of capping. The most used are: adhered capping (cement paste or sulfur) not adhered (Neoprene) and the top recess (grinding). We know very little about the influence of capping in the compressive strength. It is commonly used the experience of the concrete labs as a criterion for defining the best leveling the bases of cylindrical specimens. This study analyzed through mechanical tests specimens capped with industrial grouting –a type of concrete self-dense bagged– and mortar, used as a capstone in several laboratories of construction materials. There were molded 36 concrete specimens, half of them capped with mortar and half with grout. It was also examined the workability of the capping, analysis of variance (ANOVA) of mechanics results, adhesion and contact print between the top and the press. The results showed no significant difference between the use of mortar and the use of grout. Furthermore, it was found that the capping resistance does not affect the strength of the test specimens. Keywords: Concrete, Compressive Strength Test, Capping Concrete Specimens, Grout.

Comparison of the seismic response of reinforced auger pressure grout and concrete columns

Despite the wide use of grout as a structural material due to easy construction and cost-effectiveness, its seismic performance has rarely been evaluated experimentally. In particular, reinforced grout columns which may experience significant lateral deformation need experimental evidence to validate their adequacy. This paper summarizes findings from a relevant experimental study, which consists of five cyclic tests and one hybrid simulation test conducted at the University of California, Berkeley. The results show that reinforced auger pressure grout columns under cyclic lateral load and high constant axial load can provide ductile and reliable behavior in flexure, comparable to that of similarly configured reinforced concrete (RC) columns. Therefore, these reinforced grout columns can be considered as an adequate alternative to RC columns subjected to medium to high compressive axial loads in regions of high seismicity.

THE IMPACT OF THE TIME WHEN CASTING THE SECOND LAYER OF CONCRETE ON ITS MECHANICAL PROPERTIES

Cold joint is one of concreting problem due to delay of casting the second layer. This is due to glitch of one of mechanical machines such as the concrete mixer, concrete truck, concrete batching plants, concrete pumps, and concrete mobile; that cause the stopping of the casting process which produce forced separator. Forced separation is different from known separators like: construction joint, expansion joint and settlement joint, where its location event and shape cannot be determined moreover the design engineer cannot put that in mind during the design phase of building construction. Therefore, the target in this work is to study the effect of delay in time period when casting the second layer of concrete after 4, 9, and 16 hour for two types of concrete with compressive strength 250 kg/cm2 and 300 kg/cm2. Eexperimental work was performed at laboratory to investigate the mechanical properties of concrete (compressive strength, splitting tensile strength and flexural strength), first when sprinkle the first layer with water before casting and second when coated with a grout material.The results were investigated and it indicates that, in case of delaying in the time period for casting the second layer, there is a great effect on the mechanical properties of concrete and the use of grout coating material in forced separation has a positive impact on improving its mechanical properties.

Special Issue on Nondestructive Evaluation and Testing for Bridge Inspection and Evaluation

Special Issue on Nondestructive Evaluation and Testing for Bridge Inspection and Evaluation

Cable-Stayed Bridges: Case Study for Ambient Vibration-Based Cable Tension Estimation

A cable-stayed bridge recently constructed by the Ohio Department of Transportation incorporates measures put forth by a Federal Highway Administration study to mitigate stay motion. In following recent trends, the stays at this bridge are built without the use of grout for the purposes of inspection and, if necessary, replacement. Several experiments were performed to determine the viability of using traditional vibration techniques, which assume an integral sheath, to estimate cable tension with this new configuration.

Experiment design to evaluate interaction of high-range water-reducer and antiwashout admixture in high-performance cement grout

The injection of cement grout in water-saturated medium and the sealing of anchorages require the use of grout with high resistance to water dilution to enhance in-situ performance. This can be achieved by reducing the W/C and incorporating an antiwashout admixture (AWA) to enhance the stability. Such admixture can increase the viscosity and yield stress and necessitate higher dosage of high-range water-reducer (HRWR) to maintain the desired fluidity. Cement-based grouts with 0.30 to 0.50 W/C and different combinations of AWA and HRWR were evaluated. The study was undertaken to highlight the influence of W/C and dosage of chemical admixtures on fluidity, washout resistance, and residual compressive strength (RCS) of the underwater-cast grout. Statistical models established using a statistical design of experiments indicate that the W/C has greater effect on changes in minislump flow, washout, and RCS than the concentrations of HRWR and AWA. On the other hand, for mixtures prepared with a fixed W/C of 0.40, the models show that measured responses are highly affected by the dosages and interaction of both admixtures. Trade-off between fluidity and washout resistance and means to optimize mixture proportioning to enhance the resistance to water dilution without adversely affecting fluidity are discussed.

Grout Repair of Dent-Damaged Steel Marine Tubulars

A test program consisting of 13 steel tubular brace specimens with dent damage and various diameter-to-thickness ( D/t ) ratios was conducted to assess the residual strength and repair of damaged tubular braces used in offshore platforms. Specimens were inflicted with a dent having a depth of 0.10 D , with internal full grouting and grouted steel clamps, respectively, used to repair specimens. A baseline of unrepaired, damaged specimens subjected to concentric axial loading showed a significant reduction in residual strength due to the dent. A further reduction in axial load capacity was found in specimens subjected to combined loading. The use of grout to repair specimens was found to inhibit a growth in dent depth under axial loading and restore the capacity of the dented member to a level greater than the undamaged strength. A comparison with existing and modified analytical methods for strength prediction of unrepaired and grout repaired braces showed that these methods provided reasonable results.

Potential of grouting methods to prevent and compensate for tunnelling-induced settlement of London Clay

Abstract Tunnelling beneath a congested urban area leads inevitably to the settlement of structures located in the ground above. In the past settlement has been allowed to take place and remedial work has been undertaken to make good any damage which has occurred. Grouting techniques have sometimes been used as a remedial measure to restore structures to their original elevation. Advances in grouting techniques, together with advances in monitoring, have led to the use of grouting in a compensation mode, whereby grout injection is carefully balanced against ground loss, such that settlement is not allowed to reach the surface. This method has been used in the USA and continental Europe, but so far has not been used in the UK. The development of grouting techniques used to remediate or compensate for ground settlement are reviewed and the results presented of a trial undertaken in London to investigate the viability of this technique.

Technology of sealing dams with leading sections of horizontal joints

1. The technology of sealing with the use of grouts with an adjustable fluidity loss time (GAFLT), developed at Gidrospctsproekt and successfully introduced on the construction of the Inguri arch dam, is universal and makes possible high-quality grouting of joints with a high degree of their leakiness. 2. The new technology has indisputable advantages over the existing technology. It provides a high quality of the work and is cost effective, enabling a substantial reduction of labor expenditures and nonproductive losses of cement. 3. The GAFLT technology can be recommended for inclusion in building codes and can be used when scaling concrete dams under construction.

Concrete dam of the Bratsk hydroelectric station

The Bratsk concrete dam was designed and constructed with a sufficient degree of reliability. Settlement of the dam together with the powerhouse developed uniformly under the entire foundation. Two irreversible processes causing aging of the dam have been established by operating observations: leaching of the concrete and decompression of the contact zone of the foundation near the upstream face of the powerhouse sections. The decompression is due to the fact that the powerhouse sections are lighter than the spillway sections. At the present level this process can only be slowed by the combined use of grouting and drainage unloading.

Use of grouting when driving through the rock burst zone in the dangara irrigation tunnel

The method of tunneling through a rock burst zone with preliminary grouting of the rock pile proved to be successful both with respect to the technically selected variant and with respect to its accomplishment and can be widely used for consolidating rocks with a considerable content of loose filling on other objects.