Advanced Materials Research Vols. 919-921

Abstract: The degree of soil salinization in the west region of Jilin province is very serious, where the composition of salts in the soil and surface water is complex and mainly contains Na⁺, HCO₃^- or CO₃^2-, Cl^-, SO₄^2-, etc. The concrete engineering projects in such environments are often corroded by a variety of salt corrosion damage under the condition of dry-wet alternation. Based on the previous experimental study on the durability of concrete affected by the factors of both multiple salts and dry-wet cycles, different salts (bicarbonate, sulfate, and chloride salt) soak and dry-wet cycle tests to normal strength concrete (NSC) are conducted in this article. The test results show that all of the bicarbonate, sulfate, and chlorine salt can cause certain corrosion on NSC under the condition of dry-wet cycle. The influence degree of different harmful salts on the mass loss of concrete is as NaHCO₃ > Na₂SO₄ > NaCl > water; the influence degree of different salts on the dynamic elastic modulus of concrete is as NaHCO₃ > Na₂SO₄ > NaCl > water. Under the condition of dry-wet cycle, a variety of salts can make the erosion damage of concrete produce superposition effect, and make the concrete corrosion damage sharpened.

Abstract: Based on the mechanism of punching shear and patterns of failure of Specimen,using the unified strength theory and rigid-plastic models,the punching strength of reinforced concrete slabs supported on four sides is obtained.The theoretical formula of punching shear strength for concrete slab is given.The calculated results are in good agreement with the experimental results.

Abstract: This paper studies the impact of different dosage of GGBS on the early age and later shrinkage deformation of concrete. Through the testing method of early age shrinkage of concrete the volume stability of shrinkage of concrete under different dosage of GGBS is evaluated, and the causes and effect mechanisms of that are analyzed.

Abstract: The aim of this paper is to study the impact of GGBS on the early age cracking resistance of concrete. To assess the volume stability of premixed concrete under different dosage of GGBS an innovative cracking test method is adopted, and the causes and effect mechanisms of that are analyzed.

Abstract: Non-destructive testing using infrared thermography has been used in civil construction basically in situations involving electrical conductors or mechanical wear that normally generate heat. In the specific case of materials, the application of thermography to metal stud is well documented, but there are few reports in the literature covering thermography in concrete; these are usually limited to the inspection of cracks and to the localization of water infiltration in prefabricated concrete structures. The present report evaluates the potential of the active infrared thermography method in the detection of changes in the macrostructure of engineering cementitious composite, as well as in order to estimate its thermal performance. The results show that thermography is able to detect changes in the macrostructure and is sensitive to temperature differences among the constituents of concrete.

Abstract: Orthogonal experiments at concrete materials proved: notable errors will occur when using chemical catalyzing to predict the concrete strength. Errors are unavoidable since such methods have neglected much factors. Ground on test data, effects on concrete intensity were analyzed with changes of sand ratio, bigger aggregate, and environment humidity, cement components. Error origins of concrete intensity were found, and the fact of avoidless errors from chemical catalyzing was notarized. Materials testing combining with fieldwork, new technique was proposed for monitoring quality of fresh concrete in building site. So hidden trouble would be known betimes before elementary solidification in concrete. Practices indicated that this technique is simple and speedy, it can avoid the loss of doing over again in concrete structures and can effectively improve quality of concrete engineering.

Abstract: An experimental program was carried out to investigate whether EVA (ethylene vinyl acetate) heat-melt adhesive can potentially act as a self-healing agent in cement-based material. The effects of incorporation of EVA and heating on the properties of mortar were studied. Experimental results show that the interface between EVA and cement matrix was well improved after heating, which allows a significant improvement in flexural strength and toughness of specimen; Pre-damaged specimens in various degrees (30%, 50% and 70%) were effectively repaired by EVA and the repair efficiency all exceeded 100%. Keywords:crack; heat-melt adhesive; self-repairing

Abstract: Realistic prediction of concrete creep is of crucial importance for the safety, durability and long term serviceability of concrete structures. High performance concrete (HPC) contains combinations of various components, such as aggregate, cement, water-reducing agent and other ingredients which affect the properties of the HPC including creep. This paper reviews the accuracy of the conventional concrete (CC) creep prediction models, including B3,GL2000 and CEB-FIP(2010). Further, a new creep prediction model based on the comprehensive analysis is proposed. The improved model was calibrated through a joint optimization of laboratory creep tests. Comparisons of the results of the proposed methold with 76 data points of creep coefficient showes good agreement.

Abstract: Factors such as poor design, bad workmanship and a harsh environment can combine to cause deterioration within a concrete structure leading to visually unacceptable surface cracking or spalling of concrete cover [. In aggressive environments, corrosion of steel reinforcing bars is responsible for major deteriorations in concrete structures. Reduction in bar diameter leads to a lower resistance, which can result in brittle failure of the bar. Initiation and progression of reinforcing steel corrosion can lead to progressive weakening of the structure due to damage accumulation over a period of time, or in sudden catastrophic failures, such as the Berlin Congress Hall, a parking garage in Minnesota [. Antonaci et al. [ conducted an experimental study on different concrete cylinders damaged in compression followed by means of linear and nonlinear ultrasonic methods. Arndt et al. [ tested a concrete slab representing typical bridge decks in order to evaluate the ability of NDT methods to detect different phases of corrosion progression in concrete. Reinforced concrete beam-shaped samples were tested by Aveldano and Ortega [ in order to characterize concrete cracking due to reinforcing corrosion under different environments. Shah and Ribakov [ performed nonlinear ultrasonic testing of cubic concrete specimens with different frequency transducers. Al-Amoudi et al. [ investgated the relatioship between compressive strength of ordinary concrete and blended cement concrete with durability propeties of concrete samples and conculded that the addition of blended cement will improve the performance of concrete in ressiting corrosion of reinforcement. The main objective of this study is to investigate the effectiveness of using nondestructive testing to assess the performance of different types of concrete such as OPC and SFC. Also, to correlate different types of nondestructive testing and to investigate the possibility of capturing the occurrence of corrosion in reinforcing bars in concrete.

Abstract: The paper analyzed the phyllite properties in the highway from Shiyan-Tianshui the eastern An-kang 25^th section through the related indoor and outdoor testing. As the on-site filler CBR value didnt meet highway subgrade filling on the filler mechanical properties, and it should be improved with cement. The engineering and compaction properties were analyzed under different cement doses and gradation combinations, whose result was shown that selecting the improved phyllite gradation composition of 5% cement content and 60% stone content was the optimal. In that it could not only meet subgrade strength design requirement and the on-site application, but also be the most economical and reasonable.