Expansive Cement Research Articles

Evaluation of the sealing effectiveness of expansive cement grouts through a novel water penetration test

The main objective of the work presented in this paper is to evaluate the effectiveness of using three inorganic expansive agents in developing expansive cementitious grouts for sealing concrete cracks. Two of the agents were ettringite-based (K and NK) and one was CaO-based (G). Nine expansive cement grouts and one non-expansive cement grout were developed, and their expansive and mechanical performance were characterized. Additionally, an original method based on the water penetration test is proposed to evaluate the sealing capability of the produced grouts which has demonstrated high feasibility in determining the sealing effectiveness of the cement grouts designed. After sealing the simulated cracks, a strong decrease (≈80%) of the water penetration was detected when using 5% in weight cements of G or NK agents. An important but lower decrease (≈50%) was detected by using 5% of K agent. Moreover, the results obtained in the Brazilian test indicated that sealing with expansive cement grouts allows a high integration of the sealing material within the surrounding concrete element, achieving good mechanical bonding, so the sealing material and concrete act as a compact sole material. BSEM-EDAX analyses also showed slight evidence of chemical interaction between the sealing expansive grout and the surrounding concrete when using NK agent, but strong evidence of physical interaction since the penetration of some kind of amorphous hydrates from the grout side to the concrete side was detected.

A numerical investigation of seismic performance for an RC frame with latticed concrete infill walls

Expansive polystyrene granule cement (EPSC) latticed concrete wall can be used as an infill wall. After the expanded polystyrene granule cement form has been demolished, the part that remains is a latticed concrete infill wall comprising lattice beams and columns whose cross section is circular with a diameter of 0.12 m. The horizontal and vertical rebar are arranged within the beams and columns. The dynamic responses of a full-scale single-story reinforced concrete (RC) frame with latticed concrete infill walls subjected to earthquake-induced ground motion are simulated using the nonlinear finite element ABAQUS software. This study aims to investigate the effects of different types of earthquakes on the structure and the acceleration responses of the structure. The results obtained indicate that the structure has excellent seismic behavior, although the structural responses vary between earthquakes. This research may help in promoting the design and application of RC frames with latticed concrete infill walls.

Application of micro expansion cement in Pavement Base

Cement stabilized macadam base is widely used as a road building material in various grades of highways. Based on the law that the base cracking is mainly affected by the shrinkage of cement stabilization materials, this paper introduces the method of adding micro-expanding cement to the base that can effectively reduce the hydration shrinkage coefficient and dryness shrink factor. At the same time, it is pointed out that strict control of the amount of micro-expansion cement and the quality of the construction can also effectively reduce the occurrence of cracks in the base.

Influence of calcium sulphoaluminoferrite on the cement stone structure

Usually to obtain expansive cements sulphoaluminate clinker or mix aluminate clinker with calcium sulphates (gypsum, hemihydrate, anhydrate) are used. This paper deals with the composition and properties of solid solution of calcium sulphoaluminoferrite. It was studied an influence of calcium sulphoaluminoferrite on structure and properties cement phases. For these cements ettringite is an important hydration product. The investigation of hydration and properties of sulphomineral cements shows that ettringite are formed thus providing expansion of cement stone. Study of the hydration processes of the calcium sulfoaluminoferrite mineral in gypsum solution showed that the hydration of fine mineral fractions (less than 28 μm) occurs during partial dissolution with crystallization of small ettringite crystals from solution. Sulphoaluminoferrite mineral is characterized by the growth of large prismatic ettringite crystals with their subsequent cleavage in fractions of 45–63 μm. Research showed that for expanding additives based on calcium sulfoaluminoferrite, a polyfraction composition combining only small fractions is preferable.

Impact of elevated curing temperature on mechanical properties and microstructure of MgO‐based expansive additive cement mortars

AbstractMgO‐based expansive additive (MEA) is uniquely used in China to compensate for the thermal shrinkage. For mass concrete, its inner temperature can soar up to 60°C due to the accumulation of hydration heat, which will strongly impact the mechanical properties and microstructures. In this paper, the impacts of elevated curing temperatures on the compressive strength developments, the tensile strengths as well as the pore structures of MEA cement mortars are investigated by means of X‐ray diffraction, scanning electron microscope, and mercury intrusion porosimetry. The results show that the external addition of MEA weakens, not eliminates, the crossover effect found in the temperature‐affected strength developments, which is mainly attributed to the accelerated expansion of MEA. For the tensile strength, the weakness of the crossover effect is found more obvious. The ratio of tensile to compressive strength is also positively correlated to the MEA content and the curing temperature. A scattered prestress effect is proposed to explain this phenomenon. The microcosmic evidence proves that the elevated temperature promotes the hydration of MEA and cement, and thereby improves the early‐age microstructures but impairs the late‐age one, which is generally consistent with the mechanical results.

Application of expanding cements for sprayed concrete in tunnel construction

Introduction. The paper substantiates the actuality of the problem connected with obtaining efficient fine concretes possessing enhanced crack resistance, tightness, and duration for tunnel construction. This aim is pursued with the application of expansive cements (EC).
 Materials and methods. Various types of expansive agents were used in composition binders. Portland cement PTs 500 D0 was taken as the basic Portland cement. Studying hydration and structure formation processes during hardening of the ECs and EC-based concretes was executed utilizing a system of physicochemical methods. Assessment of construction and technical properties of the fine concretes based on composition binders was accomplished using standard research methods.
 Results. Analysis results are given for the effect of type and amount of the expansive agents on strength and volume deformation values of the concretes used in tunnel installation construction. Improvement of physical, mechanical, and technological properties and performance of sprayed concrete is shown. A general mechanism of influence of expansive additives (EA) on fine concrete properties is established. A classification of expansive cements for solving various tasks in tunnel installation construction is suggested.
 Conclusions. EA application efficiency is theoretically substantiated and experimentally proved for the case when the EA is used as an active agent in the composition binder for sprayed concrete in tunnel construction. General enhancement of technical indicators of concrete mixture and concretes is determined. EA classification is suggested for the different extent of hydrated EA expansion and various construction tasks. Replacement of standard Portland cement for an EC for underground structures concrete used in tunnel construction provides a significant increase in their maintainability.

Seismic performance of RC frames with EPSC latticed concrete infill walls

An expansive polystyrene granule cement (EPSC) latticed concrete wall, which has advantages of higher load-bearing and better environmental-friendly construction, has been widely applied in reinforced concrete (RC) frames to form a new structural system, and its seismic performance has become a hot topic in the field of earthquake engineering. This paper presents the experimental and numerical studies on the seismic performance of RC frames with EPSC latticed concrete infill walls. A full-scale single-storey model structure with openings in the walls, various spacings of steel rebar and binding methods between the walls and the RC frame was designed, and then tested on a shaking table to investigate the seismic performance. A numerical analysis model was constructed using the nonlinear dynamic modelling software ABAQUS. The comparative analysis of the test data and simulation results indicate that the designed RC frame with EPSC latticed concrete infill walls has satisfactory seismic performance, including the good collapse resistance and energy dissipation capacity. Especially the latticed concrete walls can significantly strengthen the RC frame and increase its lateral stiffness, and the model structure undergoes a super-major earthquake with minor inter-storey rotational displacements (only 1/513). Reduction in spacing of bars can delay the growth of cracks in the walls and increase the ductility of the structural system. Both local binding method and through-rebar binding method can effectively restrain the walls. Compared with local binding method, the through-rebar binding method can play an effective role in the out-of-plane stability of the wall, thus improve the integrity of the structural system. The proposed analytical procedure can be also applied in simulating the seismic performance of infilled multi-storey RC frames. To achieve more comprehensive assessment the performance of the RC frames with latticed concrete infill walls, further study on its global and local ductility relationships and the failure model of the infilled multi-storey frame should be carried out.

Block Extraction of Himalayan Rock Salt by Applying Conventional Dimension Stone Quarrying Techniques

A salt block is a regular prism of rock salt containing least undesirable cracks which is mainly used for carving artifacts especially salt lamps, tiles and other products. This research work is focused on the comparison of three common and simple dimension stone quarrying techniques including wedges and feathers, expansive cement, and controlled blasting methods for the extraction of rock salt block. The selected techniques were applied at the underground working face of Khewra Salt Mines (Punjab, Pakistan) to extract representative blocks in accordance with a predefined field experimental program. In order to find out the most suitable block extraction technique in terms of the quality of excavated salt blocks, physical and mechanical rock property tests were performed comprising of core recovery, uniaxial compressive strength, Brazilian tensile strength, dynamic Young’s modulus, quality and P-wave velocity. This paper statistically confirms that the rock salt blocks excavated by using wedges and feathers method have higher quality in comparison to the blocks obtained by expansive cement and controlled blasting techniques. Further the results of overall technique wise comparison are also discussed.

Application of coal-powder borehole-sealing material in borehole-sealing engineering

In order to make scientific analysis of the material of the coal-powder borehole-sealing technology and verify its actual sealing performance, the authors performed studies involving laboratory experiments and field tests. The research results are shown as follows. (a) The borehole-sealing material has good microexpansion properties. With an increase in additive proportion, the expansion and strength of the sealing material increase. In addition, contraction expansibility is also affected by the water/material ratio of the slurry. The smaller the water/material ratio is, the greater the degree of deformation becomes. (b) Considering the coal-powder borehole-sealing material’s expansion properties, strength characteristics and application cost determined the optimum composition ratio of the coal-powder borehole-sealing material: the volume of coal powder accounted for 70% and the additive volume accounted for 30%. In this condition, the expansion rate and maximum compressive strength of the sealing material are 6‰ and 7·30 MPa, respectively. (c) The gas concentration extracted out of the borehole sealed by using the coal-powder sealant is slightly higher than that for the borehole sealed by using expansive cement (72·50 and 69·65%, respectively).

Effect of temperature rising inhibitor on expansion behavior of cement paste containing expansive agent

The present study aims to examine the mechanism influencing the expansion characteristics of expansive cement paste in presence of different dosages of Temperature Rising Inhibitor (TRI). The expansion of cement pastes showed a higher expansion strain of the OPC-EA mixture with 0.2% and 0.4% TRI in comparison to the reference sample and a decreased shrinkage of cement pastes containing expansive agent (OPC-EA). Meanwhile, dynamic elastic modulus, hydration kinetics, mineral phase compositions and microstructure characterization of hydration products were also investigated by ultrasonic method, isothermal calorimetry, quantitative X-ray diffraction and scanning electron microscope, respectively. The delayed hydration process of expansive agent increases the amount of expansive agent available to react after the setting of cement pastes, resulting in the increased expansion strain of OPC-EA-0.2%TRI sample. The higher expansion strain of OPC-EA-0.4%TRI sample can be attributed to the lower stiffness of cement paste affected by TRI. The results showed that the addition of TRI is the main force in delaying the hydration process of ye’elimite in expansive agent by acting on the formation and morphology of ettringite. The delayed ye’elimite hydration process can be explained by inhibition of the precipitation or/and growth of ettringite.

Dependence of the Structure of Cement Stone from the Dispersion of the Alumina Component

Usually, sulfoaluminate clinker or a mixture of aluminate clinker with calcium sulphates is used to obtain expansive cements. For these cements ettringite is an important hydration product. This paper deals with the composition and properties of solid solution of calcium aluminate. It was studied an influence of calcium aluminate on structure and properties cement phases. The properties of cements containing these phase were also studied. The investigation of hydration and properties of aluminate cements shows that ettringite and its analogies are formed thus providing expansion and compression of cement stone.

The influence of expansive cement on the mechanical, physical, and microstructural properties of hybrid-fiber-reinforced concrete

This work reports the properties of hybrid-fiber-reinforced concrete (HyFRC) made with expansive (Type K) cement. Combinations of metallic and non-metallic fibers at total fiber volume fraction of 1% were studied. The effectiveness of double hooked-end (DHE) steel fibers in concrete containing expansive cement is investigated for the first time in this study. The mechanical, physical, and microstructural properties of concretes have been assessed. Additionally, the fiber pull-out test was also performed to investigate the effectiveness of Type K cement in improving the fiber-matrix interfacial bond. The results indicate that Type K cement has small influence on the mechanical properties of concrete fabricated at the same water-cement ratio of 0.35 with a similar consistency. However, as expected, it enhances the volume stability of concrete subjected to drying condition. The pull-out resistance of steel fibers increased by 26% as a result of full replacement of ordinary Portland cement (OPC) with Type K cement. A deflection-hardening performance is achieved by introducing of DHE steel fibers in HyFRC. The partially replacement of DHE steel fibers with other type of fibers results in a reduction in the strengths of HyFRC. The results obtained in this study proves that the bond between fiber and cement matrix is enhanced by fully replacement of OPC with expansive cement, which subsequently improves the mechanical properties of HyFRC.

On the interaction of Class C fly ash with Portland cement–calcium sulfoaluminate cement binder

Shrinkage cracking in concrete is a widespread problem, especially in concrete structures with high surface-to-volume ratio such as bridge decks. Expansive cements based on calcium sulfoaluminate phase were developed to mitigate the shrinkage cracking of concrete. The compressive stress induced due to restrained expansion of concrete has been shown to counteract the tensile stress generated during drying shrinkage. This research attempts to address the differential behavior of fly ash type (i.e., Class C vs. Class F) on early-age expansion and hydration characteristics of ordinary Portland cement (OPC)–calcium sulfoaluminate (CSA) cement blend. It was observed earlier that the presence of Class C fly ash (CFA), unlike Class F fly ash, shortened the expansion duration of OPC–CSA cement blend, which was hypothesized to be correlated to early depletion of gypsum. This paper presents a detailed verification of the hypothesis. Addition of external gypsum to OPC–CSA–CFA blend led to simultaneous increase in expansion and disappearance of a shoulder peak in the calorimetric curve. Thermodynamic calculations using a geochemical modeling program (GEMS-PSI) revealed higher saturation levels of ettringite in presence of external gypsum, which led to higher crystallization stress, and thereby increased expansion.

Effects of expansive additive on cement composite properties

Shrinkage is a due to chemical and physical processes in concrete. The results of these are volume changes that may cause cracking, deformation, decrease in strength and especially durability of a construction. The amount of water in concrete, the fine particles content, the dimension of construction, the method of curing of the fresh concrete and environmental conditions (temperature, humidity) are some factors influencing the shrinkage of concrete. This article deals with reduction the shrinkage of cement composites by addition of expansive cement Denka CSA and synthetic gypsum. The additives were used at a dosage of 10% of the original weight of cement. The obtained results showed different impact of these additives to the volume changes and the compressive strength of cement composites. The Denka CSA additive had a positive effect to monitored properties of cement mortars. It caused the lowest shrinkage; slight increasing of long-term compressive strength and decreasing of bulk densities after 2, 28 and 90 days of hardening.

A new approach for the mix design of (patch) repair mortars

The failure of most repairs in concrete structures is mainly manifested in the form of cracking and/or debonding of the repair layer. These two repair mechanisms could lead to the continuous corrosion of reinforcing steel in concrete. Cracking and debonding have been attributed to the high differential shrinkage that exists between the concrete substrate and repair layer as well as the lack of adherence, which commonly results from poor workmanship. It is crucial that restrained shrinkage mechanisms of patch repairs be understood so that the abovementioned effects can be prevented. The performance of patch repairs can be improved through the optimization of their mix design. Thus, it is common to use admixtures, non-cementitious compounds and polymers. However, promising technologies such as expansive admixtures that counteract shrinkage have found little application to date.Polymers do not chemically react with the cementitious matrix. They, however, have been reported to modify the microstructure in cementitious materials, consequently, resulting in improved properties with respect to mechanical, chemical and durability aspects. They increase chemical interactions with mineral phases, which improves the bond between the mortar and the substrate. Besides this, expansive cements are types of cement whose volume increases, unlike plain Portland cement where the volume typically decreases with time. This property relates to the use of expansive admixtures like quicklime, which exhibits an enormous volume increase upon hydration. This property leads to the reduction of the shrinkage, which is increased by the combination of the quicklime to a shrinkage-reducing admixtures (SRA).Using polymer technology and expansive admixtures, it is possible to develop a new approach for the mix design of repair mortars that combines the positive effects of polymer latex (increasing of bond strength) and expansive admixture (reducing the shrinkage) properties to reduce cracking and debonding failures in patch repairs.

Numerical simulation of the thermomechanical behavior of cement sheath in wells subjected to steam injection

The exposure of oil wells to extreme conditions may lead to numerous problems associated with the loss of integrity of the cement sheath. A damaged cement sheath may result in fluid leakage and in some cases cause significant economic loss and environmental degradation. Thermal recovery processes are common techniques used to enhance oil recovery by submitting the materials to severe temperature gradients. However, this heating process induces thermomechanical stresses in the cement sheath which may lead to its cracking. This paper investigates the effects of cement slurry formulation on the thermomechanical behavior of cement sheath in wells subjected to the first heating phase of steam injection. For this purpose, three types of cement slurry formulations, one standard and two others with latex additions, were designed, mixed and tested in the laboratory to evaluate their mechanical properties. An axisymmetric finite element model was then developed and used to conduct a parametric study to investigate the thermomechanical response of oil wells with cement sheaths made of the various cement slurries, as well as the influence of applied temperature gradients, heating durations and formation stiffness. The results mainly show that issues of cement sheath integrity under steam injection are generally localized in the region near the formation, and that they are closely related to the heating phase of the well. It is also found that combining the use of a more flexible and expansive cement slurry formulation with the slow application of temperature gradient generally improves cement sheath integrity during steam injection. These beneficial effects were shown to be more effective for stiffer rock formation and larger applied temperature gradients.

Expansive high-performance concrete for chemical-prestress applications

By inducing a large expansion in concrete at early age, chemical-prestressing of reinforcement can be achieved. Expansions sufficient to achieve this purpose are normally obtained with a combination of admixtures (or expansive cement) and special curing methods. However, these special concrete mixtures may suffer from excessive expansion and the resulting loss of mechanical properties and durability. In this work, a combination of expansion-promoting (based on calcium sulfoaluminate, CSA) and shrinkage reducing additives (superabsorbent polymers, SAP and shrinkage-reducing admixture, SRA) is applied to produce concrete with outstanding mechanical properties and good durability. After initial underwater curing until 28 d and further drying at 70%RH, a residual expansion in unrestrained conditions of about 4000 μm/m was obtained, which enables reaching a central concrete prestress of about 2.5–3 MPa. In spite of the high residual expansion, compressive strength of about 100 MPa was obtained and the concrete had very high freeze-thaw resistance.

Numerical Study of Stresses around Holes Drilled and Filled by Expansive Cement: Case of Isotropic Linear Elastic Block of Rock

This work dealt with an essential problem of fragmentation of rocks with expansive cement. The redistribution and magnitude of stresses and displacement generated around holes were done by using Ansys Inc. Code which is based on finite element code. Blocks of rock with one hole, two holes, and nine holes drilled in square mesh and staggered mesh have been considered. Numerical results reveal that many factors can influence the mechanism of fragmentation of a rock by using expansive cement: hole diameter, hole spacing, panel mesh, expansive pressure applied, and the elastic properties of the massif. Stresses and displacements generated globally decrease when spacing holes increase. Normal stresses allow a better stress interaction between holes in the case of square mesh disposition. Staggered mesh disposition generates higher stresses than the square mesh disposition. But the square mesh disposition can be useful for controlled fragmentation in order to obtain block of rock with square geometry. For each expansive cement and rock, there exist suitable range of diameter and spacing hole which can generate high stresses for breaking the rock.

The development of an expansive type special cement bonded investment powder for castings of non ferrous metals and alloys

ABSTRACTAn attempt has been made to develop an investment powder which expands significantly in the setting period to meet the solidification shrinkage of most metals and alloys. Investment powders consisting of tricalcium aluminate, quartz, various sulphate bearing compounds and a small amounts of controlling agents (additives) were used in the preparation of the block investment molds. A413 Al-Si (Etial 140) alloy was melted and poured in these molds to cast a test specimen of a special geometry. The preliminary results show that it is possible to produce dimensionally accurate castings by using expansive type investment powders. Samples cast into block investment molds prepared from ordinary non-expansive investment powder were smaller than the pattern size, while those poured into molds produced from expansive type powders were the same size or greater than the pattern size.

Experimental study on compressive behavior and failure analysis of composite concrete confined by glass/epoxy ±55° filament wound pipes

This paper investigates the strength and ductility of concrete confined by Glass/Epoxy ±55° Filament Wound Pipes (GFRP) under axial compression. A total of 24 cylindrical specimens were prepared with expansive and Portland cements, properly compacted and un-compacted for different composite fresh concrete matrix. Test results showed that compressive strength and axial deformation at failure of concrete confined with GFRP tubes increased by an average of 2.85 and 5.57 times these of unconfined concrete, respectively. Macro and micro analyses of GFRP pipes after failure were also investigated. Debonding, whitening, matrix/transfer cracking, delamination and splitting mechanisms were detected at failure, respectively. The experimental results were also employed to assess the reliability of design models available in the literature for confined concrete compressive strength.