Early-age carbonation curing of fresh concretes has shown its capacity to accelerate the production, recycle CO 2 , and to improve the concrete performance. The challenge facing this technology is the moisture content in fresh concrete which impedes CO 2 diffusion. This paper studies the effects of moisture content on carbonation reactivity of lightweight concretes (LWCs). The moisture content in LWC was adjusted by varying (1) the water to cement ratio, (2) the moisture carried in by lightweight aggregates, (3) the moisture removed by forced fan drying, and (4) the externally added water by surface spray as compensation of water loss. The performance of the carbonated concretes was evaluated by carbon uptake, strength gain, plastic shrinkage, and pH values. A process involving vibration compact forming, preconditioning, carbonation, water compensation, and subsequent hydration proved to be effective in achieving high degree of carbonation and hydration.

No abstract

No abstract

About 53% area of Bangladesh is alluvial deposited and affected by sulfate, salinity and chloride in water and soil. Existing sulfate and chloride can severely damage the building in coastal regions. In this paper durability of cement is evaluated on the basis of strength of mortar cube, concrete cylinder test. Besides the sulfate resistance is measured by change of length of the mortar bar specimens during exposure to sulfate solution and the attacking chloride properties by Rapid chloride ion penetration test using OPC, PCC, 20% FA, 30% FA and 40% FA. The strength was observed in cube sample about 40.65, 37.2MPa after 13 weeks in sulfate solution and linear expansion was obtained about 0.28% and 0.133% for OPC and PCC cement with reference to the water. The compressive strength of the cylindrical specimens was about 16.96, 18.34 MPa for OPC and PCC, respectively at the age of 28 days. The permeability of chloride ion of OPC sample was 22.8% higher than the PCC at this age. Journal of Engineering Science 12(1), 2021, 69-75

In this research, an investigation was carried out through experimentation and numerical modeling to evaluate the cracking pressure induced due to corrosion of reinforcement for different cover thicknesses, grades of concrete and bar locations. The model was also used to determine the patterns of crack for a different number of bars and the effect of bar diameter on cracking pressure. The critical pressure was measured experimentally by applying hydraulic pressure through a hole in concrete cubes of 150 mm. Abaqus 6.14 was used as a modeling platform. From the experimentation and numerical modeling, it was found that with the increase of cover thickness the critical pressure was increased irrespective of bar locations. A lower cracking pressure was observed for corner bar with respect to the sidebar. On the other hand, with the increase in bar diameter, a decrease in cracking pressure was observed. The critical pressure observed was also increased with higher grades of concrete. For corner bars with cover thickness 37.5 mm, the critical pressure was found as 6-10 MPa and it increased up to 17 MPa for the cover thickness of 64 mm for different grades of concrete. On the other hand, for other bar location with the cover thickness of 37.5 mm and 64 mm, the pressure required to initiate crack was about 7.6 MPa and 14.8 MPa, respectively, for C20 grade concrete.