Properties and composition of recycled aggregates from construction and demolition waste suitable for concrete production

Cracks on the concrete surface are one of the earliest indications of degradation of the structure which is critical for the maintenance as well the continuous exposure will lead to the severe damage to the environment. Manual inspection is the acclaimed method for the crack inspection. In the manual inspection, the sketch of the crack is prepared manually, and the conditions of the irregularities are noted. Since the manual approach completely depends on the specialist’s knowledge and experience, it lacks objectivity in the quantitative analysis. So, automatic image-based crack detection is proposed as a replacement. Literature presents different techniques to automatically identify the crack and its depth using image processing techniques. In this research, a detailed survey is conducted to identify the research challenges and the achievements till in this field. Accordingly, 50 research papers are taken related to crack detection, and those research papers are reviewed. Based on the review, analysis is provided based on the image processing techniques, objectives, accuracy level, error level, and the image data sets. Finally, we present the various research issues which can be useful for the researchers to accomplish further research on the crack detection.

Crack detection using image processing: A critical review and analysis

Advances in Computer Vision-Based Civil Infrastructure Inspection and Monitoring

Use of sea-sand and seawater in concrete construction: Current status and future opportunities

At present, the cement industry generates approximately 5% of the world’s anthropogenic CO2 emissions. This share is expected to increase since demand for cement based products is forecast to multiply by a factor of 2.5 within the next 40 years and the traditional strategies to mitigate emissions, focused on the production of cement, will not be capable of compensating such growth. Therefore, additional mitigation strategies are needed, including an increase in the efficiency of cement use. This paper proposes indicators for measuring cement use efficiency, presents a benchmark based on literature data and discusses potential gains in efficiency. The binder intensity (bi) index measures the amount of binder (kg m−3) necessary to deliver 1 MPa of mechanical strength, and consequently express the efficiency of using binder materials. The CO2 intensity index (ci) allows estimating the global warming potential of concrete formulations. Research benchmarks show that bi ∼5 kg m−3 MPa−1 are feasible and have already been achieved for concretes >50 MPa. However, concretes with lower compressive strengths have binder intensities varying between 10 and 20 kg m−3 MPa−1. These values can be a result of the minimum cement content established in many standards and reveal a significant potential for performance gains. In addition, combinations of low bi and ci are shown to be feasible.

Measuring the eco-efficiency of cement use

http://saetaequina.com/files/1-s2_0-S0029549305002888-main.pdf

Effect of specimen sizes, specimen shapes, and placement directions on compressive strength of concrete

Effect of oyster shell substituted for fine aggregate on concrete characteristics: Part I. Fundamental properties

Due to the shortage of natural fine aggregates in many countries, sea sand has been alternatively used in the production of concrete. However, due to the presence of chlorides in sea sand, the threat of corrosion of steel reinforcing bars embedded in such concrete has become a major concern. Therefore, many studies related to corrosion level and bond behavior have been performed. The realistic corrosion levels at which the aged structures are exposed to danger are usually greater than 1% and beyond minimal 2%. Since safety predictions of aged concrete structures based on corrosion failure are of the utmost importance, research concerning more realistic corrosion levels would help the prediction process. For this purpose, two types of specimens are investigated to understand the bond properties as a function of corrosion level in RC members. Prismatic concrete specimens with reinforcements subjected to corrosion before and after casting of concrete are used for pullout tests. Based on the experimental data, an equation for bond strength prediction is developed. Also, the validity of the proposed equation is demonstrated through comparison with the existing prediction curves.

Bond strength prediction for reinforced concrete members with highly corroded reinforcing bars

Effect of partial replacement of sand with dry oyster shell on the long-term performance of concrete

Many experimental and theoretical investigations have been carried out to examine the reduction phenomenon of compressive strength of cylindrical concrete specimens with size, but up until now, an adequate analysis technique has not been developed. In this paper, the fracture mechanics type size effect on the compressive strength of cylindrical concrete specimens was studied, with the diameter, the height/diameter ratio, and the volumetric spiral ratio of the cylinder considered as the main parameters. For this purpose, theoretical and statistical analyses were conducted. First, a size effect equation was proposed to predict the compressive strength of cylindrical concrete specimens with various diameters and height/diameter ratios. Second, the model equation derived from the plain concrete was extended for predicting the compressive strength of spirally reinforced concrete cylinders. The proposed equation showed good agreement with the existing test results for concrete cylinders with and without spiral reinforcement.

Seong-Tae Yi

Papers

Effect of specimen sizes, specimen shapes, and placement directions on compressive strength of concrete

Effect of oyster shell substituted for fine aggregate on concrete characteristics: Part I. Fundamental properties

Bond strength prediction for reinforced concrete members with highly corroded reinforcing bars

Effect of partial replacement of sand with dry oyster shell on the long-term performance of concrete

Size Effect on Compressive Strength of Plain and Spirally Reinforced Concrete Cylinders