Applied Mechanics and Materials Vol. 372

Abstract: The aim of the contribution is to confirm or rule, by using non-parametric Kruskal Wallis test, the hypothesis published [1] that the construction type and building materials have not statistically relevant effect on the final building airtightness. For non-parametric test is used the same sample as in [1], where the impact of construction type on the airtightness is refused by using parametric test - one way analysis of variance (ANOVA).

Abstract: This study is conducted to evaluate analytically the effect of cement binder proportions (ordinary Portland cement, blast-furnace slag and fly ash) on the hydration heat of mass concrete with specific compressive strength of 30 MPa. Two types of blended concretes were mixed; binder of PSLB_352 consists of ordinary Portland cement (OPC) : blast-furnace slag (BFS) : fly ash (FA) = 3 : 5 : 2 and binder of PSLB_442 comprise OPC : BSF : FA = 4 : 4 : 2. For comparison, a control concrete mixture was mixed with commercial low-heat cement. To measure temperature characteristics due to hydration heat of each mixture, large concrete blocks were cast and temperature within concrete blocks was measured until the equilibrium temperature was reached. Finite element model was developed for predicting hydration heat of mass concrete based on thermal characteristics of mass concrete derived from large concrete blocks. The effect of cement binder proportions on the hydration heat of mat foundation was evaluated by developed finite element model.

Abstract: This research investigates the influence of shrinkage reducing admixture (SRA) on the tensile behavior of strain-hardening cement composite (SHCC). SHCC materials with specified compressive strength of 50MPa were mixed and tested. All SHCC mixes with different dosage of shrinkage reducing admixtures were reinforced with 2.2 % polyvinyl alcohol (PVA) fibers at the volume fraction. A special SRA, i.e. strontium (Sr)-based SRA, used in this study was based on a phase change material (PCM) that has the ability to absorb or release the hydration heat of cement composite. This paper focuses on the tensile behavior and cracking characteristics of SHCC materials under direct tension. The effect of a special SRA on the fresh properties, such as flow and air content, and hardened properties of SHCC materials was investigated. Test results showed that SRA reduces the air content of SHCC material. The SRA can also improve the tensile strength of SHCC material.

Abstract: Three 1/3-scale squat steel fiber reinforced concrete (SFRC) shear walls with height-to-length ratio of 0.55 were manufactured and tested up to failure. Two walls (SFRC-SS and-LS) are similar to each other except the height (230 and 460mm) of vertical slits with the width of 40mm. For comparison, solid wall (SFRC-NS) was made. All specimens had the same rectangular cross-section of 1,100mm x 50mm, with wall panel height of 600mm. The experimental results showed that squat SFRC shear walls with vertical slits exhibited more stable hysteretic behavior than a solid SFRC shear wall. Vertical slits on the squat SFRC shear walls improve the ductility and energy dissipation capacity but decrease the load-carrying capacity and stiffness of squat SFRC walls.

Abstract: The use of strain-hardening cement composite (SHCC), which exhibits metal-like deformation behavior and has ability to restrict crack opening, as a retrofit material for seismic retrofitting of existing infrastructures, has been the subject of high expectations. In this work, Three SHCC mixtures including different chemical or mineral admixtures were prepared and evaluated based on the mechanical properties, such as flow, sprayability, compressive and uniaxial tensile performances. All SHCC mixtures were reinforced with polyvinyl alcohol (PVA) fibers at volume fraction of 2.2%. Mechanical properties of each SHCC mixture were measured and evaluated after mixing, pumping, and shotcreting. Experimental results indicated that the compressive strength and elastic modulus of three SHCC mixtures increased almost linearly according to shotcreting procedure from mixer to nozzle. And the uniaxial tensile of SHCC mixture (SHCC-AE) with AE agent was superior to the other SHCC mixtures (SHCC-MC and-N).

Abstract: This paper describes the experimental results of 70 MPa high strength steel fiber reinforced concrete (SFRC) with different steel fiber volume fractions in compression. The effect of steel fiber on fresh properties, compressive strength, toughness index, cracking procedure of high strength steel fiber concrete is also investigated. The steel fibers were added as the volume fractions of 0%, 0.5%, 1.0%, 1.5% and 2.0%. The cylindrical specimens with Φ100 x 200 for compressive tests were manufactured in accordance with ASTM C 39[. The experimental results showed that the slump of fresh SFRC was inversely proportional to the fiber volume fraction added to high strength concrete. As the addition of steel fiber increased, compressive strength of SFRC decreased. Inclusion of steel fiber improves compressive toughness of high strength SFRC.

Abstract: This work evaluated the applicability of polyethylene (PE) fiber reinforced strain-hardening cement composite (PE-SHCC) layer at the bottom of reinforced concrete (RC) beams to improve the flexural performance and cracking behavior. PE-SHCC material with specific compressive strength of 70MPa was reinforced with 1.5% PE fibers at the volume fraction. Four RC beams with cross-section of 130 x 170mm and length of 1,460mm were made and tested under four-point monotonic loading. Three beams were layered with PE-SHCC material and one whole RC beam was a control specimen for comparison. Principal variable is the thickness of PE-SHCC layer; 20, 40 and 60mm that are equivalent to 11, 23 and 35% of beams depth. Experimental results indicated that the addition of PE-SHCC layer enhanced the crack-damage mitigation of RC beams and improve the structural behavior, such as strength and ductility, of RC beams.

Abstract: The effects of aggregate size and fiber volume fraction on the flexural behavior of 70MPa high strength steel fiber-reinforced concrete (SFRC) were investigated in this work. Test variables consist of fiber volume fraction (0, 1 and 2 %) and maximum aggregate size (8, 13 and 20 mm). The prism for flexural test was 100 x 100 x 400 mm and was tested under four points loading. Flexural toughness index was measured using ASTM C 1018 procedure. Test results indicated that the addition of steel fiber to 70MPa high strength concrete improves flexural and post-cracking behaviors. This phenomenon is remarkable for SFRC mixture with higher fiber content and smaller aggregate size. Also, the flexural toughness of high strength SFRC depends primarily on fiber content. The maximum aggregate sizes were secondary in importance.

Abstract: This paper provides the analytical mode and results of three strain hardening cement composite (SHCC) infill walls tested under laterally cyclic loading. The main variables of the experimental tests were vertical slit and slit length. The comparison between the experimental and analytical results showed that the shear strength was different depending on the slit length. A two-dimensional FEM analytical model was constructed in order to predict the behavior of the tested walls. The smeared crack model for SHCC elements was determined non-orthotropically crack model considered that it is able to represent fixed cracking. A good agreement was found between the test and the prediction in terms of lateral load-displacement relations and damage distribution.

Abstract: In this study, some experimental investigations on the development of mechanical properties with age of high performance concrete (HPC) incorporated with blast furnace slag with fly ash or silica fume have been reported. Four different blended HPC were prepared in 0.40 water-binder ratio. At every four mixtures, the compressive strength, splitting tensile strength and modulus of elasticity at 7 and 28 days have been observed for HPC developments. Consequently, only replacement of silica fume significantly increases the mechanical properties in terms of compressive strength, splitting tensile strength and modulus of elasticity.