“…This can be attributed to higher compressive strength in PCC35-0.5 M Na 2 SO 4 mortars as a result of accelerated pozzolana reaction and formation of more AFt phase. High compressive strength results in reduced spaces in mortar matrix hence greatly reducing the penetration of chloride ions [31]. PCC35-0.5 M Na 2 SO 4 also exhibited lower porosity compared to PCC35-H 2 O.…”
Chloride-laden environments pose serious durability concerns in cement based materials. This paper presents the findings of chloride ingress in chemically activated calcined Clay-Ordinary Portland Cement blended mortars. Results are also presented for compressive strength development and porosity tests. Sampled clays were incinerated at a temperature of 800 ∘ C for 4 hours. The resultant calcined clay was blended with Ordinary Portland Cement (OPC) at replacement level of 35% by mass of OPC to make test cement labeled PCC35. Mortar prisms measuring 40 mm × 40 mm × 160 mm were cast using PCC35 with 0.5 M Na 2 SO 4 solution as a chemical activator instead of water. Compressive strength was determined at 28th day of curing. As a control, OPC, Portland Pozzolana Cement (PPC), and PCC35 were similarly investigated without use of activator. After the 28th day of curing, mortar specimens were subjected to accelerated chloride ingress, porosity, compressive strength tests, and chloride profiling. Subsequently, apparent diffusion coefficients ( app ) were estimated from solutions to Fick's second law of diffusion. Compressive strength increased after exposure to the chloride rich media in all cement categories. Chemically activated PCC35 exhibited higher compressive strength compared to nonactivated PCC35. However, chemically activated PCC35 had the least gain in compressive strength, lower porosity, and lower chloride ingress in terms of app , compared to OPC, PPC, and nonactivated PCC35.
“…This can be attributed to higher compressive strength in PCC35-0.5 M Na 2 SO 4 mortars as a result of accelerated pozzolana reaction and formation of more AFt phase. High compressive strength results in reduced spaces in mortar matrix hence greatly reducing the penetration of chloride ions [31]. PCC35-0.5 M Na 2 SO 4 also exhibited lower porosity compared to PCC35-H 2 O.…”
Chloride-laden environments pose serious durability concerns in cement based materials. This paper presents the findings of chloride ingress in chemically activated calcined Clay-Ordinary Portland Cement blended mortars. Results are also presented for compressive strength development and porosity tests. Sampled clays were incinerated at a temperature of 800 ∘ C for 4 hours. The resultant calcined clay was blended with Ordinary Portland Cement (OPC) at replacement level of 35% by mass of OPC to make test cement labeled PCC35. Mortar prisms measuring 40 mm × 40 mm × 160 mm were cast using PCC35 with 0.5 M Na 2 SO 4 solution as a chemical activator instead of water. Compressive strength was determined at 28th day of curing. As a control, OPC, Portland Pozzolana Cement (PPC), and PCC35 were similarly investigated without use of activator. After the 28th day of curing, mortar specimens were subjected to accelerated chloride ingress, porosity, compressive strength tests, and chloride profiling. Subsequently, apparent diffusion coefficients ( app ) were estimated from solutions to Fick's second law of diffusion. Compressive strength increased after exposure to the chloride rich media in all cement categories. Chemically activated PCC35 exhibited higher compressive strength compared to nonactivated PCC35. However, chemically activated PCC35 had the least gain in compressive strength, lower porosity, and lower chloride ingress in terms of app , compared to OPC, PPC, and nonactivated PCC35.
“…At a Nano scale level, porosity appears between the layers C-S-H; from Nano scale to micro scale capillary networks can be observed due to the excess of free water in the concrete, identifying them as gel pores (0, 5 nm to 10 nm) and capillary pores (10 nm to 10 µm); between 50 µm and 1 mm porosity is a result, mainly, if the air enters during the mixing process; finally, the millimetric scale includes those air holes caught during the concrete vibration process, having a tight relation with its workability. [16]. in our case, this last rank is due to the process of rodding during the filling of the test tube.…”
Section: B Pre-processingmentioning
confidence: 64%
“…The influence of porosity in concrete and mortar strength is distinguished and addressed by many authors. [ [16]. In that aspect, [17] and [18], have also kept in mind this air void separation when testing concrete strength through images processing.…”
the concrete quality evaluation is defined by the statistical processing of the resistance values obtained from the rupture test specimen (potential strength), or samples (real strength). In certain occasions, when the methods above mentioned are not possible or in order to get extra information, mainly on-site, it is common to use nondestructive testing (NDT). Lately, taking advantage of photography cameras and the growing capacity and processing speed of computers, strength evaluation and concrete deformation measuring procedures have been developed based on no-contact techniques consisting of images record, their subsequent digital processing and their treatment through algorithms of computing engineering. This paper s suggests developing, based on new techniques, a classification model of conventional concrete based exclusively on the shooting of images and the subsequent proceeding of the characteristics deduced from their digitalization. The images come from tests and/or witnesses to be tested in the tutor College, National Technology University, Córdoba Regional College, while their proceeding and the extraction of correlations with the obtained strength in those tests, was done in the tutored College of the National Technology University Regional College Rafaela Keywords-Concrete, digital proceeding, images, quality I.
“…Ca 2+ and Mg 2+ show higher chloride diffusivity than Na + [28][29][30][31]. Blended cements, for example, pozzolana based, are less permeable due to increased cementitious material from the reaction between the included pozzolana and Ca(OH) 2 resulting from hydration of cement [32][33][34]. Blended cements have also exhibited higher binding ability of chlorides, because of the proportionate amount of alumina if it forms part of the reactive phase, and hence decrease chloride diffusion [2].…”
This paper reports study findings on the diffusivity of chloride ions in potential blended cement. The cement, abbreviated as PCDC, was made from blending ordinary Portland cement (OPC) with dried calcium carbide residue and an incinerated mix of rice husks, spent bleaching earth, and broken bricks. The aim of the study was to investigate the ability of PCDC to withstand aggressive chloride environment. 10 cm × 10 cm mortar cubes were prepared using PCDC and cured for 28 days in saturated calcium hydroxide solution. The cured mortar cubes were subjected to aggressive chloride media in a laboratory set up. The test cement was subjected to chloride profile analysis with depth of cover as a function of w/c ratio and curing period in alternate dry and wet environments of 3.5 percent sodium chloride solution. The experiments were carried alongside neat OPC and OPC + 25% pulverised fuel ash (OPC + 25% PFA). Results showed that PCDC exhibited lower chloride ingress as the depth of cover increased. In conclusion, the study showed that PCDC was a potential cementitious material with high ability to withstand aggressive environment of chlorides.
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