Drying Shrinkage Strain Research Articles

Study on early strength agent for improving early strength performance of water-stabilized macadam material

Because triethanolamine (TEA) and anhydrous sodium sulfate (Na2SO4) can both improve the performance of cement stabilized macadam material, an optimal dosage group is found by compounding the two materials to improve the dry shrinkage performance of cement stabilized macadam material. Based on unconfined compression test and dry shrinkage strain test, the changes of compressive strength of water-stabilized macadam materials caused by different compound dosage groups and original materials were compared. The results show that the three dosage groups can improve compressive strength and reduce the dry shrinkage strain of the cement stabilized macadam material. The compressive strength of 2.0 % anhydrous sodium sulfate and 1.0 % triethanolamine was the best, increasing 73.8 %; moreover, the dosage group can effectively reduce shrinkage cracks, which is 3.88 % less than that of the blank control group. The test data were tested by correlation analysis and there were significant differences between the control group and each dosage group, which indicated that the admixture had a significant improvement on the material properties.

Drying Shrinkage Strain of Palm-oil by-products Lightweight Concrete: A Comparison between Experimental and Prediction Models

Drying shrinkage in concrete can be attributed to loss of moisture, variations in temperature, and the chemical reactions of cement with water and carbon dioxide, is one of the most important parameters which affects the durability and service life of the concrete structures. Recently, the lightweight concrete has got a considerable attention to be used in structural applications. Although, this concrete has very high drying shrinkage compared to conventional concrete. Therefore, the design engineers need an accurate and precise estimation of the concrete shrinkage, so that the safe and durable structure can be produced. The main objective of this research is to compare the development of drying shrinkage strain of three concrete mixes made of by-product aggregate namely oil pam shell and oil-palm-boiler clinker from the palm oil industry with the prediction models. For that purpose, ten (ACI209R, EN1992, MC2010, CEB/FIP1990, AASHTO-LRFD, GL2000, AS3600, JSCE, SAK and B3) prediction models of drying shrinkage have been selected from the standards, codes and researchers. All suggested parameters for the prediction models were considered in the estimation of shrinkage strain for the by-product concretes. In addition, the error percentage and coefficient of variation methods have been used to compute the accuracy of prediction models. The results showed that in early ages, almost all the prediction models estimated similar results with the experimental curves. However, at later ages, only few models for each concrete predicted similar results to the experimental values.

Durability of cementitious materials reinforced with various Kraft pulp fibers

This study was completed to determine the strength, permeability, stability, and interfacial properties of cementitious materials reinforced with engineered Kraft pulp fibers namely, mechanically modified fiber and chemically treated fiber. These two engineered fibers, along with a commercially available unmodified fiber, were used in reinforcing cementitious materials. Test results showed an increase in the permeability characteristics for the reinforced concretes. Hence, these fibres reduced the compressive strength and durability of reinforced concretes as compare to the unreinforced concrete. However, the two engineered fibres performed better than the unmodified fibre in terms of compressive strength, chloride ion permeability and water sorptivity. Further, the drying shrinkage strain was reduced considerably when only 1% chemically treated fiber was added. The study concludes that these two engineered pulp fibers are better alternatives to commercially available unmodified cellulose fibers.

Ceramic waste powder an alternative cement replacement – Characterization and evaluation

In a rapidly growing world population and toward meeting consumers' needs, solid waste landfills will continue receiving extensive volumes of waste. Transforming large amount of solid wastes into an alternative resource will preserve the reducing nonrenewable resources of materials; maintain the required energy and in addition will help solve environmental and exhausted landfill problems. The utilization of solid waste materials in concrete, which is a predominant construction material, has attracted numerous studies especially those that can replace cement which is a major contributor to global green-house gas emissions. Ceramic tiles industry generates ceramic waste powder during the final polishing process. Ceramic waste powder (CWP) can cause soil, water and air pollution. Using ceramic waste powder (CWP) as an alternative ingredient in concrete will have a positive environmental impact. The aim of this study was to characterize the CWP with respect to its composition, morphology and activity. Also, the study evaluated the use of CWP as an alternative ingredient partially replacing cement on the performance of fresh and hardened concrete. In this investigation, concrete mixtures incorporating CWP as cement replacement with different replacement levels (i.e., 10%, 20%, 30% and 40% by mass) were examined. Three concrete grades with different cement contents were used (i.e., 25 MPa, 50 MPa and 75 MPa). The fresh concrete workability retention of the mixtures was evaluated by measuring time to reach zero slump. Compressive strength development with age (i.e., 7, 28 and 90 days) and drying shrinkage strain at 120 days were measured. The chloride ion penetration (i.e., rapid chloride ion penetration test - RCPT) and bulk electrical resistivity were conducted to evaluate durability performance of the mixtures. The permeable pores were measured to assess the development in the concrete microstructure. Test results showed that CWP has potential to be used as an ingredient in concrete mixtures to partially replace cement. The study showed that concrete mixtures with ceramic waste powder (CWP) had variable performance of the measured properties depending on the replacement level used. In general, CWP can be used in concrete mixtures to partially replace cement and improve specific performance criteria. A performance index (PI) approach was developed in order to be able to select the suitable CWP replacement level to optimize the mixture's specific properties to achieve a desired performance criteria. In this study, the PI considered workability retention, compressive strength and durability as performance measures for selecting the most suitable CWP replacement level. The PI could be extended to include additional criteria. The use of 10% CWP replacement level was adequate for strength improvement, replacement levels between 10% and 20% could be used to improve workability retention while a level of 40% replacement was needed for durability enhancement. For more than one performance criteria the CWP replacement level varied; a 10% to 20% CWP was suitable for optimizing the workability retention and strength of the mixture. However, the use of 30% to 40% CWP would optimize the combination of all studied criteria.

Effect of shrinkage-reducing admixture and expansive agent on mechanical properties and drying shrinkage of Engineered Cementitious Composite (ECC)

In order to reduce the drying shrinkage strain of traditional ECC and diminish the shrinkage differences between concrete and PVA (PolyVinyl Alcohol) fiber, this paper designs eighteen groups mix proportions based on Taguchi Methods. The influences of water-binder ratio, sand-binder ratio, fly ash content, expansive agent content, shrinkage-reducing agent content and PVA fiber volume content on the compressive strength, tensile properties and drying shrinkage are researched. In addition, the effect of PVA fiber on the crack resistance is investigated. The results indicate that the shrinkage strain of ECC increases with the raising of water-binder ratio, and decreases with the increasing of sand-binder ratio, fly ash content, expansive agent, and shrinkage-reducing agent; The anti-cracking performance is significantly improved along the fiber volume content changes, but it has little effect on ECC shrinkage strain. The compressive and tensile strength of ECC will greatly reduce with the increasing of shrinkage-reducing agent, rather, the compressive strength of ECC will enhance with the increase of expansive agent; But the expansive agent will lower the tensile strength and ultimate tensile strain. In the scope of this research, the water-binder ratio, sand-binder ratio, and fly ash content is about 0.25–0.33, 0.33–0.45, and 65% respectively. The research generated a set of reliable and valuable test data for the researchers and practical structural engineers in the field of ECC drying shrinkage.

Effect of fines on the drying crack resistance of composite soil stabiliser-stabilised gravel soil

The objective of this research was to investigate the effect of fines on the drying crack resistance of composite soil stabiliser-stabilised gravel soil (CSSSGS) using the following laboratory tests: indirect tensile strength (ITS), indirect tensile resilient modulus (ITRM), and drying shrinkage (DS). The indirect tensile failure strain (ITFS), which was calculated according to the ITS and ITRM, was used to replace the direct tensile failure strain (DTFS). The DS energy anti-cracking coefficient (DSEAC) and the ratio of ITFS to DS strain (RID) were used to estimate the crack resistance of CSSSGS with varying fines contents. This study showed that the values of these two indices decreased with the increase in fines content and water loss time, indicating that fines content and water loss adversely affect the crack resistance of CSSSGS.

Time-dependent deflection of conventional, self-compacting and lightweight concrete slabs

Design codes usually define time-dependent deflection as a multiple of instantaneous deflection. Therefore, the ratio of long-term to instantaneous deflection is crucial in the design of concrete structures. The experimental results of three series of experiments on long-term deflection of conventional, lightweight and self-compacting concrete slabs under sustained loads are compared and discussed in this study. The slabs were subjected to loading at age 14 d after casting. The flexural deflection caused by two distinct levels of applied load, and the effects of the drying shrinkage and creep were monitored for 225 d for three pairs of simply supported one-way slabs. Comparative analysis of the mechanical properties of concrete types at 14 and 28 d is conducted and the creep coefficient and drying shrinkage strain in the mixtures are determined. Furthermore, individual effects of these parameters on the ratio of long-term to instantaneous deflection are discussed. The results obtained confirm that, in the existing time-dependent deflection models, the effects of loading age, load value and the environmental conditions should be included. In addition, the experimental ratio of the long-term to instantaneous deflection in slabs is far from the predictions of ACI 318-14, AS 3600-09, EN 1992.1.1 and CSA-A23-04 codes.

Modeling and numerical investigations for hierarchical pattern formation in desiccation cracking

Desiccation cracking and its pattern formation are widely observed in nature. The network of the surface cracks forms polygonal cells with typical size. This crack pattern is not formed in a simultaneous manner, instead, formed in a sequential and hierarchical manner. The strain energy accumulated by the heterogeneous drying shrinkage strain is systematically released by the cracks. In this sense, desiccation cracking phenomenon can be regarded as a typical example of the pattern formation in the dynamical system with dissipation. We propose a mathematical model for the pattern formation in desiccation cracking with emphasis on the emergence of the typical length scale with the typical geometry resulting from the hierarchical cell tessellation. The desiccation crack phenomenon is modeled as the coupling of desiccation, deformation, and fracture. This coupling model is numerically solved by weakly coupled analysis of the desiccation process and the deformation/fracture process. The basic features of the desiccation crack pattern and its formation process reproduced by the numerical analysis show reasonable agreement with experimental observations. This agreement implies that the proposed coupling model properly addresses the fundamental mechanism for the hierarchical pattern formation in desiccation cracking.

Water reducing agent effects on the engineering performance of cement stabilized aggregates

Water reducing agents (WRAs) are usually utilized in cement concretes to reduce the water-cement ration, increasing mechanical strength and improving the durability of concrete structures. As a kind of widely used construction materials in pavement structures, i.e., base or subbase course, cement stabilized aggregates (CSAs) have to face their own problems, e.g., drying shrinkage at early ages. To evaluate the feasibility of water reducing agent in cement stabilized aggregates, and its effects on engineering performance, six groups of cement stabilized aggregates were prepared (water reducing content = 0, 0.5, 1.0, 1.5, 2.0 and 2.5 wt.%). Engineering performances including density-water relationships, unconfined compressive strength (UCS), tensile splitting strength (TSS), compressive resilience modulus (CRM) and drying shrinkage strain(DSS) were measured. Result indicates that water reducing agents used in this study can significantly benefit the engineering performances of cement stabilized aggregates. The function or role of water reducing agent in cement stabilized aggregates were summarized, which would be beneficial to guide the water reducing agent utilization in cement stabilized aggregates.

High Strength Lightweight Aggregate Concrete using Blended Coarse Lightweight Aggregate Origin from Palm Oil Industry

The benefits of using structural lightweight concrete in construction industry, particularly in high rise buildings, over normal weight concrete are numerous. The main method of producing structural lightweight concrete is the use of lightweight aggregates instead of ordinary aggregates in concrete. Due to the limited resources for natural and artificial lightweight aggregates, the alternative sources for lightweight aggregates should be discovered from industrial wastes. Oil palm shell (OPS) and oil-palm-boiler clinker (OPBC) are two solid wastes from palm oil industry and are available in abundance in tropical regimes. The use of just OPS as coarse lightweight aggregate in concrete mixture has some drawbacks for concrete. The aim of this study was to investigate engineering properties of a lightweight concrete containing both of these aggregates. For this purpose, in this study, 50% (by volume) of OPS was replaced with OPBC in an OPS lightweight concrete. The test results showed that when OPS was substituted with OPBC, significant improvement was observed in the compressive, splitting tensile and flexural strengths. In addition, initial and final water absorption as well as drying shrinkage strain of blended coarse lightweight aggregate concrete were significantly less than OPS concrete.

Influence of geogrid on the drying shrinkage performance of concrete pavements

The aim of this study is to investigate the effect of geogrid on the drying shrinkage behaviour of concrete pavements. For this purpose, two categories of concrete specimens were prepared and tested by drying them within the controlled environmental conditions, for 56days. The first category of specimens included casting and testing nine concrete prism specimens having dimensions of 75×75×280mm. These specimens were divided into three groups. The first group included three unreinforced concrete prism specimens and taken as references. The second group consisted of three concrete prism specimens reinforced with a single biaxial geogrid layer located at 20mm from the top of specimen. The last three specimens (third group) were reinforced with a biaxial geogrid layer placed at 37.5mm from the top of specimen. The second category of specimens, which was suggested in this study to simulate the behaviour of concrete pavements, consisted of preparing and testing six concrete slab specimens. They had dimensions of 30×280×280mm. The specimens of this category were divided into two groups. The first group included three unreinforced concrete slab specimens (References). The second group included three concrete slab specimens reinforced with a single biaxial geogrid layer placed at 15mm from the top of specimen. The changes in the length of the prisms and the changes in the area of the slabs were measured and evaluated. Test results obtained illustrate that, under the controlled drying conditions, the geogrid can slightly reduce the drying shrinkage strains of the concrete pavements.

Comprehensive study of concrete creep, shrinkage, and water content evolution under sealed and drying conditions

AbstractA comprehensive study of the time‐dependent behaviour of concrete, enhanced by measuring the evolution of the respective mass water content, is presented. Compressive creep as well as shrinkage are investigated on sealed and unsealed specimens in terms of the concrete age at loading of 2, 7, and 28 days, respectively, at a loading level of 30% of the compressive strength at loading. In addition, on the basis of the collected measurement data, the impact of load application on the moisture content is studied and the Pickett effect is re‐examined. The obtained set of material data consists of basic and drying creep strains for different concrete ages at loading, autogenous shrinkage strains as well as combined autogenous and drying shrinkage strains, the evolution of the mass water content, the water desorption isotherm, and the time‐dependent evolution of Young's modulus and the compressive strength. It provides a consistent set of material data for a particular concrete grade and will be available for calibrating and validating concrete models.

Characteristics of dry shrinkage and temperature shrinkage of cement-stabilized steel slag

The objective of the present study was to investigate the characteristics of dry shrinkage and temperature shrinkage of cement-stabilized steel slag (CSS). The steel slag was intended to be utilized to replace the macadam in cement-stabilized base course to reduce dry shrinkage and temperature shrinkage of semi-rigid base materials. Dry shrinkage and temperature shrinkage tests were performed to analyze the water loss rate, dry shrinkage strain, dry shrinkage coefficient and temperature shrinkage strain of CSS and cement-stabilized macadam (CSM) as functions of time, cement content and gradation types of the material. The water loss rate of CSS increased with the rise in time, and then tended to be flat on about 10th days. The hygroscopicity of coarse gradation CSS was larger than those of intermediate gradation and fine gradation CSS. With the same gradation, the more the cement content was, the greater the water loss rate was. It was suggested that the cement content of CSS should not be more than 4%, which can obviously reduce the dry shrinkage strain. Compared with CSM, CSS with rational adjustment of gradation owned a smaller dry shrinkage strain and would not produce a larger temperature shrinkage strain. It is feasible to replace the base macadam with waste steel slag, which is beneficial to improve the characteristics of dry shrinkage and temperature shrinkage of semi-rigid base material and utilization of waste steel slag. This paper aims to provide a solid theoretical foundation to popularize the wide utilization of CSS in engineering applications.

Long-Term Behavior of Low-Heat Cement Concrete under Different Curing Temperatures

The present study is to estimate long-term characteristics of low-heat cement-based ternary blended concrete prepared for reducing hydration heat in mass concrete. 15% modified fly ash and 5% limestone powder were added for partial replacement of the low-heat cement. To achieve the designed compressive strength of 42 MPa, water-to-binder ratios were determined to be 27.5, 30 and 32.5% for ambient curing temperatures of 5, 20 and 40°C, respectively. Test results showed that, with the decrease in curing temperature, the drying shrinkage strains tended to decrease, whereas creep strain increased.

Behaviour of Recycled Coarse Aggregate Concrete: Age and Successive Recycling

Recycled Coarse Aggregate (RCA) concrete construction technique can be called as ‘green concrete’, as it minimizes the environmental hazard of the concrete waste disposal. Indian standard recommends target mean compressive strength of the conventional concrete in terms of water cement ratio (w/c). The present work is an attempt to study the behaviour of RCA concrete from two samples of parent concrete having different age group with regard to the relationship of compressive strength with water cement ratios. Number of recycling may influence the mechanical properties of RCA concrete. The influence of age and successive recycling on the properties such as capillary water absorption, drying shrinkage strain, air content, flexural strength and tensile splitting strength of the RCA concrete are examined. The relationship between compressive strength at different w/c ratios obtained experimentally is investigated for the two parameters such as age of parent concrete and successive recycling. The recycled concrete using older recycled aggregate shows poor quality. While the compressive strength reduces with successive recycling gradually, the capillary water absorption increases abruptly, which leads to the conclusion that further recycling may not be advisable.

Oil palm shell as an agricultural solid waste in artificial lightweight aggregate concrete

The aim of this study was to produce a sustainable construction material by incorporating an agricultural solid waste, namely oil palm shell (OPS), in an artificial lightweight aggregate concrete. For this purpose, in a structural lightweight aggregate concrete made of expanded clay, the lightweight aggregate was substituted with OPS in 0, 25 and 50% by volume. Properties such as compressive strength under different curing conditions, as well as density, splitting tensile and flexural strengths, modulus of elasticity and drying shrinkage of expanded clay–OPS concretes were measured and discussed. The test results showed that partial substitution of expanded clay by OPS increased the density, compressive strength, specific strength (compressive strength to weight ratio), as well as splitting tensile and flexural strengths of lightweight concrete. However, it was observed that the modulus of elasticity decreased by about 4 and 13% in the 25 and 50% substitution levels, respectively. The expanded clay–OPS concretes showed greater drying shrinkage strain compared to expanded clay lightweight concrete. In addition, it was found that the sensitivity of compressive strength of concretes containing OPS to the lack of curing is due to high drying shrinkage and consequently micro-cracks formation in the interfacial transaction zone of the concretes.

Mechanical properties of alkali activated blast furnace slag pastes reinforced with carbon fibers

Alkaline activation has become a useful procedure to obtain high strength cement composites without Portland cement. Different industrial byproducts can be activated using this technique, e.g. blast furnace slag, fly ash or metakaolin. Thus a new generation of more sustainable composites is being developed. However, the main disadvantage of these composites is their high drying shrinkage strain. Among the different approaches to address this problem, shrinkage reducing admixtures are the most used, but the addition of fibers can be useful for this purpose. In this work, alkali activated slag (AAS) pastes have been reinforced with carbon fibers (CF). The effect of the concentration of alkaline activator (Na2O% and silica modulus) and the fiber aspect ratio (using different length fibers with the same diameter) on the mechanical properties has been assessed. Mechanical characterization comprised bending and compressive strength tests, ultrasonic pulse velocity and density measurements, and drying shrinkage tests, in which CF were capable of improving the mechanical strengths of AAS pastes while controlling the specimens strain due to shrinkage. CF additions increased bending strength up to five times, and increases up to 20% in compressive strength were observed. Furthermore, CF can be a convenient addition to control the drying shrinkage of AAS composites. Even in adverse conditions, such us 50% RH, where unreinforced specimens actually broke, CF could guarantee the stability of the specimen.

Influence of type of fibers on the properties of high performance cement-based composites

In this work twenty fiber reinforced cement-based composites (FRCCs) were studied, in which CaO-based expansive agent was used. Five different kinds of fibers were added, three hooked metallic: steel, zinc-coated and brass-coated; two plastic: corrugated polypropylene (PP) and hooked polyethylene terephthalate (PET) fibers. All the twenty mixtures, as well as a reference mixture without fibers, were characterized by recording fresh consistency, compressive and flexural strength, as well as drying shrinkage strains. Results obtained showed an improved flexural strength if high dosage of CaO-based expansive agent is used with either zinc or brass-coated fibers. The reason could be the formation of calcium hydroxide zincate (CHZ) crystals at the interface between fibers and cement paste promoted by alkaline environment. These CHZ crystals were observed by SEM, and they are likely able to enhance the quality of the interface fiber-matrix by increasing adhesion. On the other hand, the use of CaO seemed to accelerate PET fiber degradation due to alkaline hydrolysis leading to reduced FRCC mechanical performance. When used in the presence of either PP fibers or steel hooked fibers, CaO produced insignificant effects on mechanical performance. Finally, drying shrinkage was reduced due to the addition of CaO, whichever the type of fiber used.

Restrained Shrinkage Cracking and Dry Shrinkage of Rapid-Set Prepackaged Cementitious Materials

AbstractThe dry shrinkage characteristics of 23 rapid-set prepackaged cementitious materials collected from the current market have been investigated in this study. The materials showed various trends and rates of free dry shrinkage strain development. Overall, most materials had the free dry shrinkage of less than 0.05% at 28 days; however, only materials with the 28-day free dry shrinkage of less than 0.025% were observed to exhibit a low risk of restrained shrinkage cracking. The restrained shrinkage cracking typically occurred within a week after casting primarily because of the rapid growth of dry shrinkage during this period. A higher free dry shrinkage strain or a higher rate of free dry shrinkage strain development at the early age normally resulted in an earlier formation of cracking and a larger crack size during the restrained shrinkage test. Coarse aggregate extension reduced the free dry shrinkage and the risk or the size of restrained shrinkage cracking or delayed the time of restrained shri...

Physical model of drying shrinkage of recycled aggregate concrete

We prepared concretes (RC0, RC30, and RC100) with three different mixes. The poresize distribution parameters of RAC were examined by high-precision mercury intrusion method (MIM) and nuclear magnetic resonance (NMR) imaging. A capillary-bundle physical model with random-distribution pores (improved model, IM) was established according to the parameters, and dry-shrinkage strain values were calculated and verified. Results show that in all pore types, capillary pores, and gel pores have the greatest impacts on concrete shrinkage, especially for pores 2.5-50 and 50-100 nm in size. The median radii are 34.2, 31, and 34 nm for RC0, RC30, and RC100, respectively. Moreover, the internal micropore size distribution of RC0 differs from that of RC30 and RC100, and the pore descriptions of MIM and NMR are consistent both in theory and in practice. Compared with the traditional capillary-bundle model, the calculated results of IM have higher accuracy as demonstrated by experimental verification.