Drying Shrinkage Values Research Articles

Performance of magnesium silicate hydrate cement modified with dipotassium hydrogen phosphate

Magnesium silicate hydrate (M−S−H) cement has been extensively studied in recent years. However, poor fluidity and large drying shrinkage restrict its application. To improve the fresh state and hardening properties, this study investigates the effect of dipotassium hydrogen phosphate (DKP) on the fluidity, setting time, rheological behaviour, compressive strength and drying shrinkage of magnesium silicate hydrate cement. The effect of DKP content on hydration reactions and hydration process was also investigated via pH measurement, XRD, FTIR and TG/DTG. The microstructural analysis was conducted using ESEM. The experimental results indicated that DKP presents a higher water reduction efficiency than sodium hexametaphosphate (SHMP) and can be used as a superplasticizer for magnesium silicate hydrate cement. The compressive strength of M−S−H cement was increased by the addition of DKP, especially at early ages. The maximum compressive strength for specimens containing DKP is 96 MPa at 56 days. Moreover, the cement with the addition of DKP exhibited lower drying shrinkage, and the drying shrinkage value was only 0.085% when a mortar with a water to cement ratio of 0.45 and sand to binder ratio of 3 is prepared. The addition of DKP was shown to improve performance of M−S−H cement for potential construction applications.

The Durability of Recycled Fine Aggregate Concrete: A Review.

With the rapid development of urbanization, many new buildings are erected, and old ones are demolished and/or recycled. Thus, the reuse of building materials and improvements in reuse efficiency have become hot research topics. In recent years, scholars around the world have worked on improving recycle aggregates in concrete and broadening the scope of applications of recycled concrete. This paper reviews the findings of research on the effects of recycled fine aggregates (RFAs) on the permeability, drying shrinkage, carbonation, chloride ion penetration, acid resistance, and freeze–thaw resistance of concrete. The results show that the content of old mortar and the quality of recycled concrete are closely related to the durability of prepared RFA concrete. For example, the drying shrinkage value with a 100% RFA replacement rate is twice that of normal concrete, and the depth of carbonation increases by approximately 110%. Moreover, the durability of RFA concrete decreases as the RFA replacement rate and the water–cement ratio improve. Fortunately, the use of zeolite materials such as fly ash, silica fume, and meta kaolin as surface coatings for RFAs or as external admixtures for RFA concrete had a positive effect on durability. Furthermore, the proper mixing methods and/or recycled aggregates with optimized moisture content can further improve the durability of RFA concrete.

Physicomechanical properties, stabilization mechanism, and antifungal activity of alkali-activated slag mixed with Cr6+ and Ni2+ rich industrial wastewater

An eco-sustainable approach applied to full disposal of Ni and Cr (VI) wastewater through the fabrication of alkali-activated slag (AAS). The impact of activator type (NaOH, Na2SiO3, and NaAlO2), heavy metal-containing-wastewater (Ni or Cr), and curing time (1-90-day) on the compressive strength, drying shrinkage, and immobilization efficiency have been addressed. Both compressive strength gain and loss were detected when Cr- and Ni-wastewater was mixed with AAS, depending on the type of alkali-activator. Nevertheless, all activated mixtures with wastewater demonstrated drying shrinkage values lower than that of the control sample (mixed with tap water). Ni and Cr have stabilized inside AAS-microstructure through the cationic exchange between Mg/Ni and Cr/Al within hydrotalcite phase or their localization on a negative charge of tetrahedral Al atom inside activated aluminosilicate skeleton. All the fabricated samples showed Ni and Cr concentrations in leachates lower than the regularity limits of toxicity characteristic leaching procedure (TCLP) and solubility threshold limit concentration (STLC) after 28-day of curing. The proposed strategy not only successfully applied for the safe disposal of heavy metals but also led to the fabrication of cementitious materials with high resistivity to detrimental sulfur oxidizing Aspergillus Niger fungal strain, which makes such cement effectively applied in microorganisms-rich-media.

Pozzolanic reactivity and drying shrinkage characteristics of optimized blended cementitious composites comprising of Nano-Silica particles

Measurement of reaction rate amid Pozzolans and portlandite (Ca(OH2) in the pore solution of cementitious system is the essential mechanism that need to be quantified for any blended cementitious system. So, in this study pozzolanic reactivity of multi-blended cementitious composites (binary, ternary and quaternary) was determined and corroborated using three different techniques i.e., strength activity index (SAI), selective dissolution method (SDM) and thermogravimetric analysis (TGA). In addition, efforts were made to correlate the measured drying shrinkage values of multi-blended cementitious mix with pozzolanic reactivity indices. Theory of particle packing which works on the basis of modified Andreasen and Andersen model was adopted to design the optimized blended cementitious mixes. It is observed that pozzolanic reactivity was found to be the highest for 3% nano-silica admixed binary cementitious mix, however, this binary mix reported that associated drying shrinkage is a cause of concern. Further measurement on ternary and quaternary blended mix revealed that SCMs at triplet scale (quaternary blended) is found to be equally pozzolanic and also sustainable with respect to the phenomenon of drying shrinkage. This is attributed to the fact that synergic effect of multiple SCMs (quaternary blend) triggered the pozzolanic activity by enhancing the CH consumption rate from the pore solution. From the results of the experimental investigation, it is also proposed that there exists a “three-phase drying system” for all kind of cementitious mixes. Drying shrinkage results also showed best fit in correspondence to measured pozzolanic reactivity indices.

Mechanical strengths, drying shrinkage and pore structure of cement mortars with hydroxyethyl methyl cellulose

This paper aims at investigating the long-term mechanical strengths and drying shrinkage, as well as pore structure of cement mortars with hydroxyethyl methyl cellulose (HEMC). The results show that the 3-d flexural strength and compressive strength of cement mortars tend to decrease with the HEMC content increasing. At 28 d to 360 d, the strengths keep decreasing with the HEMC content increasing at 0–1%, and then increase from the minimum value with the HEMC content increasing at 1–3%, still being much lower than those of the control (0% HEMC). Throughout the curing age, both the tensile bond strength and the drying shrinkage value gradually increase with the HEMC content, to be nearly twice at 3% HEMC than those of the control. HEMC significantly delays the 3-d hydration of cement pastes, but has negligible retardation effect on the hydration after 28 d, to bring the similar late hydration degree of cement pastes with HEMC or not. With the HEMC content increasing in the range of 0–1%, incorporating HEMC brings the sharp increase of macro pores, large capillary pores and porosity, and decreases the interconnected pores to bring many more closed pores. Further increasing the HEMC content to 3%, macro pores and porosity decrease, large capillary pores slightly increase and interconnected pores have a negligible change. Obviously, the understanding on the performance development of cement mortars with HEMC is conducive to the better application of HEMC in dry-mix mortars to meet different requirements.

Microstructure and durability properties of lightweight and high-performance sustainable cement-based composites with rice husk ash.

Sustainable solutions are investigated to reduce the environmental damage caused by greenhouse gases and CO2 emissions. Cement is a construction material responsible for greenhouse gases and CO2 emissions. Thus, CO2 emissions are reduced by using replacement materials such as rice husk ash instead of cement. This study investigated the durability and mechanical properties of lightweight and high-performance, sustainable cement-based composites. A foaming agent was used to reduce the unit weight of the mixtures. Also, pumice powder (PP) and rice husk ash (RHA) were used to improve cement-based composites' durability and mechanical properties. The density of mixtures varies between 1666 and 2205 kg/m3. The early age strength of the mixes using 12.5% RHA has increased. The mixtures' compressive strength (91 days) with 25% RHA and 50% PP was 46.6 MPa. As the PP content of mixes increased, drying shrinkage values increased. Expansions decrease as the initial compressive strength increases in mixtures exposed to sulfate. As RHA and PP's ratio increased, weight loss decreased in mixes exposed to HCl, while weight loss increased in mixes exposed to H2SO4. It was determined that the content of CH(OH)2 is important in mixes exposed to HCl and impermeability is important in mixes exposed to H2SO4. It has been observed that the initial compressive strength is also important in mixes exposed to the freeze-thaw effect. As the foam content of the mixes increased, the compressive strength decreased, while the drying shrinkage increased. As a result, using up to 25% RHA has increased the performance of cement-based composites.

Improvement of traditional clay bricks’ thermal insulation characteristics by using waste materials

This study aims to improve clay bricks' thermal insulation properties by using waste materials. Laboratory scale samples were produced by an extrusion process, which simulates a feasible industrial production technique. The study results reveal that the unit weight of brick was reduced, and thermal properties were improved by introducing grapevine twig and poplar dust by forming pores in the brick mud after firing. When the substitution ratio of waste materials increased from 2.5 %–15 % by volume gradually, it was determined that the thermal conductivity coefficient (λ), dry bulk specific gravity, and compressive strength value of the clay brick decreased. However, the moisture content for extrusion and the water absorption ratio increased. The amount of waste material in clay brick mud was optimized, and the effect of these waste materials on the plastic and hardened properties of clay bricks were investigated. As a result, the optimum mix ratio of grapevine twig and poplar dust was 7.5 % by volume considering extrudability, physical, thermal and mechanical properties of the final product. It was shown that the bricks' weight was reduced by 25 %, and the thermal conductivity coefficient was decreased by 22 % at a 7.5 % substitution ratio by volume, respectively. With the addition of waste materials, drying shrinkage values decreased due to waste materials restricting effect, while firing shrinkage values increased due to increased porosity. Moreover, it was determined that these two waste materials could be used at similar dosages because they have introduced similar characteristics to traditional clay bricks.

Effect of Lightweight Foamed Concrete Confinement with Woven Fiberglass Mesh on its Drying Shrinkage

Drying shrinkage is the major drawback of lightweight foamed concrete (LFC) as reported by many researchers. It is happened due to the loss of water in the capillary of concrete mixture. This problem caused the changes of dimension or volume of the concrete structure which lead to the cracking and failure thus shorten the life performance of the material. Once the water evaporated from the cement paste, it is impossible to replace it back. Thus, this paper studies the drying shrinkage behaviour of LFC with the confinement of woven fiberglass mesh at three different densities were 600kg/m3, 1100kg/m3, and 1600kg/m3. The woven fiberglass mesh implemented in this research is a synthetic textile fabric with an alkali resistance characteristic. The LFC specimens were wrapped 1-layer to 3-layer(s) of woven fiberglass mesh to enhance the drying shrinkage performance. The drying shrinkage test was measured accordance with the ASTM C157 specification and cured under air storage condition. Protein-based foaming agent (NORAITE PA-1) was used to produce the desirable density of LFC. The result shows that confinement of 160g of woven fiberglass mesh significantly improves the drying shrinkage of LFC compared to control and the enhancement also increase as the layer(s) of textile fabric is added from l-layer to 3-layer(s). Besides, the densities of LFC also play an important role to control its drying shrinkage behaviour. As proven at higher density of LFC the reduction of drying shrinkage value can be obtained.

Drying Shrinkage and Rapid Chloride Penetration Resistance of Recycled Aggregate Concretes Using Cement Paste Dissociation Agent.

In the present study, a recycled concrete aggregate (RCA) coating treatment using a cement paste dissociation agent (CPDA) with different mixing methods was newly incorporated in RCA concrete mixtures. First, a preliminary test program was conducted to determine the proper dosage of the CPDA solution throughout its RCA concrete test results from compressive strength, flexural strength, and elastic modulus. Then, a series of experimental tests were carried out to investigate the effect of RCA coating treatment, different mixing method such as the equivalent mortar volume (EMV) method and conventional method, and different RCA replacement ratios on durability test results of RCA concrete such as drying shrinkage values and rapid chloride penetration test (RCPT) values. The test results showed that all RCA concretes mixed with the coated RCAs were found to be workable regardless of different mix methods, with the slump and air contents of all the mixes being almost identical. All the concrete specimens, which were mixed with the coated RCAs with CPDA solution, represented lower drying shrinkage and RCPT values than those mixed without RCA coating treatment, regardless of different mix proportioning methods or RCA replacement ratios. This holds for the concrete specimens proportioned with the EMV method, regardless of different RCA replacement ratios.

Strength and Shrinkage Properties of Heat-Cured Fly Ash–Based Geopolymer Mortars Containing Fine Recycled Concrete Aggregate

Abstract Geopolymer has obtained significant importance as an alternative eco-friendly binder material for ordinary portland cement (OPC) as it can be produced from the reaction between the industrial by-product materials rich in alumina, silica, and alkaline solutions. Therefore, usage of geopolymer effectively in the construction industry will help to reduce the consumption of a huge quantity of natural resources for the energy processes required for the production of OPC. It is also one of important solution to control carbon dioxides emission by the usage of OPC. On the other hand, using construction and demolition waste (C&DW) as the source of recycled aggregates in construction industry helps to reduce the huge consumption of natural aggregates and protect the environment from the disturbances caused by the unorganized dumping of C&DW. In this study, an attempt has been made to produce fly ash (FA)-based geopolymer mortar mixes using C&DW effectively as fine aggregates partially. The effects of recycled fine aggregates (RFA), the ratio of alkaline liquid (AL) to FA, and duration of heat curing on the properties of the produced geopolymer mortar mixes have been discussed in this article. To determine the influence of RFA on the strength and volume change behavior of mixes, natural fine aggregates were replaced by RFA at 0, 10, 20, 30, 40, and 50 % by mass. The AL/FA ratio was adopted as 0.4 and 0.6. Higher compressive strength was observed for most of the mortar mixes having RFA up to 20 %, and higher drying shrinkage value was found for the mixes with higher RFA content. Scanning electron microscopy (SEM) images were also studied for knowledge about the signature of the formed structures in the mortar mixes, which were observed having higher strength.

Combined effects of microsilica, steel fibre and artificial lightweight aggregate on the shrinkage and mechanical performance of high strength cementitious composite

In this study, the effects of micro-steel fiber, pelletized fly ash lightweight aggregate and microsilica content on the fresh and hardened properties of high-performance cementitious composite (HPCC) were experimentally investigated. Micro-steel fibers having a length of 6 mm were used in the production of mixtures at the level of 0%, 1% and 2% by total volume. Besides, artificial lightweight aggregate produced by the pelletizing method was employed in the mixture production by 0% and 20% of total aggregate volume. 0% and 25% of the total binder content were designated as microsilica. Thus, a total of 12 different HPCC mixtures were obtained. The water-to-binder ratio of 0.2 was chosen in the design of all HPCC mixtures. A high-rate water-reducing chemical admixture is used to give a suitable flow for the fresh mixtures. The mechanical properties of HPCC mixtures are evaluated in terms of compressive and flexural strengths and elastic modulus. In addition to these, total water absorption and capillary water absorption tests were performed to evaluate the pore structure and permeability. The drying and autogenous shrinkage values were determined during the 60-day drying period. Thus, the effects of fiber content, microsilica addition, and artificial lightweight aggregate content were examined. The results of the experiment showed that the mechanical properties of HPCC and shrinkage behavior have been improved with the increase of steel fiber volume fraction. Furthermore, the negative effects of artificial lightweight aggregate can be eliminated by microsilica.

Optimising High Lime Fly Ash Content By Means of Silica Fume İncorporation To Control Alkali-Silica Reaction And Drying Shrinkage of Mortars

In this study, the effect of binary and ternary cementitious systems composed of portland cement, high-lime fly ash and silica fume on the compressive strength, alkali-silica reaction (ASTM C 1567) and drying shrinkage of mortar mixtures was researched. For this purpose, binary and ternary binders were prepared with partial replacement of cement with either fly ash (15wt% and 30wt%) or silica fume (5wt%) or both mineral admixtures (15wt+%5wt% and 30wt%+5wt%). An alkali reactive basalt aggregate was used in this study. It was found that partial replacement of cement with high-lime fly ash reduced the strength of mortar mixtures even up to 28-days. Besides, addition of 5% silica fume had not a significant effect on the early strength of fly ash-bearing mixtures. However, silica fume inclusion improved the 28-day strength of mixtures. In terms of alkali-silica reaction (ASR), the fly ash with lower lime content reduced the 14-day expansion more than that of fly ash with higher lime content. The opposite results were the case in 28-day ASR expansions. The ASR expansions of the fly ash-bearing mixtures were significantly reduced by the introduction of the additional 5% silica fume to these mixtures. However, silica fume incorporation remarkably increased the drying shrinkage values of the mixtures. Finally, fly ash with higher lime content was found to be more satisfactory in terms of compressive strength, alkali-silica reaction and drying shrinkage in the ternary binder system.

Study on the role of activators to the autogenous and drying shrinkage of lime-based low carbon cementitious materials

In order to improve the recycling of industrial solid wastes in the build materials area, the long-term development of auotogenous and drying shrinkage of lime-based low carbon cementitious materials (LCMs) was investigated in this work. In addition, the influence of chemical admixture (Na2SO4 and NaOH) on the shrinkage behavior of LCMs was systemically studied and compared. Moreover, the hydration kinetics, evolution of the compositions of hydration products and microstructure of LCM were investigated and analyzed to reveal the mechanism of the shrinkage behavior of LCM. The results showed that LCMs have lower autogenous and drying shrinkage value compared to those of Portland cement (PC). The addition of Na2SO4 to the LCM mixture further mitigated the shrinkage value of the LCM, especially for autogenous shrinkage. Na2SO4 in the LCM led to an additional number of ettringite (AFt) crystals formed in the paste at the early age, and the autogenous shrinkage of LCM was effectively decreased due to the compensation effect of the AFt on the shrinkage. Moreover, a large number of AFt crystals as skeletons embedded in the C(A)SH gel contributed to restricting the shrinkage of the paste. However, NaOH in the LCM caused the alkali activated reaction of the slag particles in the LCM and resulted in a LCM microstructure with fewer AFt crystals and more fine pores. Thus, the NaOH increased the autogenous and drying shrinkage of the LCM to some extent.

Volume Change Characteristics of Eco-Friendly Mortar Mixes Produced with Geopolymeric Binder and Recycled Fine Aggregate

Abstract The production of geopolymer mortar using recycled fine aggregate (RFA) generated from concrete waste has significant potential to be a sustainable construction material. In this article, the volume change properties of the produced geopolymer mortar mixes are studied in terms of drying shrinkage up to the age of 180 days and reported as the percentage increase with respect to the shrinkage value of 3 days. The influence of RFA content, alkaline liquid (AL) in terms of the concentration of sodium hydroxide (SH) solution, the ratio of sodium silicate (SS) solution to SH solution, and the ratio of AL to fly ash (FA) were investigated on the drying shrinkage properties of the geopolymer mortar mixes. All the cast specimens were cured at 80°C for 24 hours. Higher drying shrinkage values were observed for the mortar mixes produced with higher RFA content, AL/FA, SS/SH ratio, and lower concentration of SH solution. Scanning electron microscope images were studied for the samples taken from the geopolymer mixes showing lower drying shrinkage values to understand the microstructure.

Effects of Corn Stalk Fly Ash (CSFA) on the Mechanical and Deformation Properties of Cemented Coal Gangue Backfill

To reduce the amount of cement used in cemented coal gangue backfill (CCGB, a mixture of coal gangue, cement, fly ash, and water), mechanical and deformation properties of CCGB in which CSFA partially replaces the cement (0, 10, 20, 30, and 40 wt%) were studied. Compressive strength, acoustic emission during uniaxial loading, shear strength, and drying shrinkage were analysed. The compressive strength, shear strength, and drying shrinkage tests were performed at different curing times. The results showed that cemented coal gangue and corn stalk fly ash backfill (CGCAB) presented better performance, and the CGCAB with a 20% substitution rate had the best performance at day 28. Despite having the largest drying shrinkage value, 20% is the best choice for the substitution rate of CSFA. A 20% CSFA addition can enhance the bearing capacity of CGCAB and improve its failure mode, which is of great significance to support the upper overburden load and maintain the surface stability of the goaf.

Shrinkage Behavior of Cementitious Mortars Mixed with Seawater

Abstract The shrinkage behavior of cementitious materials mixed with seawater is investigated. Cement mortar mixtures were prepared with two water-to-cementitious materials ratios (w/cm = 0.36 and 0.45), two binder compositions (namely, ordinary portland cement (OPC) and OPC with 20 % fly ash replacement), and two types of water (tap water and seawater). The autogenous and drying shrinkage behavior of these mixtures are examined using ASTM standard test methods for 65 days. The use of seawater as mixing water increased the autogenous shrinkage. At w/cm 0.36, the ultimate autogenous shrinkage increased from 213 μs in the mixture with tap water to 387 μs in the mixture with seawater; the corresponding values were 149 and 314 μs, respectively, for mixtures with w/cm 0.45. An acceleration of the cement hydration at early ages caused by the seawater is identified as the cause of the increase in autogenous shrinkage in mixtures with seawater. At w/cm 0.36, seawater did not have a strong effect on the drying shrinkage, and tested mixtures had ultimate drying shrinkage values between 543 and 663 μs. At w/cm 0.45, in mixtures without fly ash, ultimate drying shrinkage increased from 838 μs in the mixture with tap water to 1,027 μs in the mixture with seawater. In mixtures with fly ash, the ultimate drying shrinkage increased from 738 μs in the mixture with tap water to 1,370 μs in the mixture with seawater. The drastic increase in the drying shrinkage in mixtures containing fly ash and seawater at w/cm 0.45 seems to be due to changes in mass loss behavior and the development of a finer pore size distribution. In applications where drying shrinkage may be a concern, the use of fly ash in seawater-mixed concrete could be problematic and lead to increased cracking risk. While the trends observed here will also hold in concrete, quantifying drying shrinkage and cracking of concrete based on the drying shrinkage of mortar mixtures is complex and depends on many other factors.

Effects of high-calcium sepiolite on the rheological behaviour and mechanical strength of cement pastes and mortars

This paper presents an experimental study on the rheological behaviour and mechanical strength of cement pastes and mortars prepared with high-calcium sepiolite (HCSP). HCSP was used to replace 0.0%, 2.5%, 5.0%, 7.5%, 10.0%, and 15.0% of cement. The rheological behaviour of fresh specimens was investigated along with the yield stress and plastic viscosity, which were approximated using the Bingham plastic model. Tests were also conducted to investigate the compressive strength, flexural strength, and drying shrinkage of hardened specimens. The results showed that the addition of HCSP has an adverse effect on the rheological behaviour of fresh specimens. The compressive strength and flexural strength are highest for specimens with an HCSP content of 7.5% but this is somewhat negated by the high drying shrinkage values. In contrast, the drying shrinkage values are lowest for specimens with the highest HCSP content (15.0%). It can be concluded that HCSP is a potential cement replacement material, but it is necessary to improve the workability of the fresh specimens and reduce drying shrinkage of the hardened specimens before this mineral can be used in the production of structural concrete.

Thermo- mechanical properties of alkali-activated slag–Red mud concrete

This study conducts an experimental programme to investigate the possibility of utilising a binary combination of red mud (RM) and slag in the form of alkali-activated slag-RM (AASR) as a useful material for application in jointed plain concrete pavement (JPCP). Slag was replaced with RM at levels of 10, 20, 30, and 40% by weight, and the mechanical, thermal and dimensional stability properties of the mixtures were measured at various ages. The results show that mechanical strength was reduced with increasing RM. Samples of AASR concrete with 30% RM had the best thermal properties with increases in thermal conductivity and specific heat of 9% and 5%, respectively, over those of neat alkali-activated slag (AAS) concrete. The drying shrinkage of AASR is high and samples with 30% RM had the highest drying shrinkage values of 1.90 and 3.95 times those of neat AAS and ordinary portland cement (OPC) concretes, respectively.

Fabrication of GO/Cement Composites by Incorporation of Few-Layered GO Nanosheets and Characterization of Their Crystal/Chemical Structure and Properties.

Original graphene oxide (GO) nanosheets were prepared using the Hummers method and found to easily aggregate in aqueous and cement composites. Using carboxymethyl chitosan (CCS) as a dispersant, few-layered GO nanosheets (1–2 layers) were obtained by forming CCS/GO intercalation composites. The testing results indicated that the few-layered GO nanosheets could uniformly spread, both in aqueous and cement composites. The cement composites were prepared with GO dosages of 0.03%, 0.05% and 0.07% and we found that they had a compact microstructure in the whole volume. A special feature was determined, namely that the microstructures consisted of regular-shaped crystals created by self-crosslinking. The X-ray diffraction (XRD) results indicated that there was a higher number of cement hydration crystals in GO/cement composites. Meanwhile, we also found that partially-amorphous Calcium-Silicate-Hydrate (C-S-H) gel turned into monoclinic crystals. At 28 days, the GO/cement composites reached the maximum compressive and flexural strengths at a 0.05% dosage. These strengths were 176.64 and 31.67 MPa and, compared with control samples, their increased ratios were 64.87% and 149.73%, respectively. Durability parameters, such as penetration, freeze-thaw, carbonation, drying-shrinkage value and pore structure, showed marked improvement. The results indicated that it is possible to obtain cement composites with a compact microstructure and with high performances by introducing CCS/GO intercalation composites.

Investigation on Failures of Composite Beam and Substrate Concrete due to Drying Shrinkage Property of Repair Materials

A Finite Element Analysis (FEA) and an experimental study was conducted on composite beam of repair material and substrate concrete to investigate the failures of the composite beam due to drying shrinkage property of the repair materials. In FEA, the stress distribution in the composite beam due to two concentrate load and shrinkage of repair materials were investigated in addition to the deflected shape of the composite beam. The stress distributions and load deflection shapes of the finite element model were investigated to aid in analysis of the experimental findings. In the experimental findings, the mechanical properties such as compressive strength, split tensile strength, flexural strength, and load–deflection curves were studied in addition to slant shear bond strength, drying shrinkage and failure patterns of the composite beam specimens. Flexure test was conducted to simulate tensile stress at the interface between the repair material and substrate concrete. The results of FEA were used to analyze the experimental results. It was observed that the repair materials with low drying shrinkage are showing compatible failure in the flexure test of the composite beam and deform adequately in the load deflection curves. Also, the flexural strength of the composite beam with low drying shrinkage repair materials showed higher flexural strength as compared to the composite beams with higher drying shrinkage value of the repair materials even though the strength of those materials were more.