pH-Triggered Release Performance of Microcapsule-Based Inhibitor and Its Inhibition Effect on the Reinforcement Embedded in Mortar

The smart release of healing agents is a key factor determining the inhibition efficiency of microcapsules-based corrosion inhibitors for reinforced concrete. In this study, the release behavior of benzotriazole (BTA) in microcapsule-based inhibitors was investigated in mortar sample to clarify the influence of different hydration products on the release process. The results indicated that under high pH environment (pH > 12.4), only about 5% reserved BTA was released from the mortar sample. pH drop resulted in the increased release of BTA from mortar sample. Most BTA in the microcapsule-based inhibitors was released from mortar sample in low pH environment, which was closely related to morphology/composition alterations of hydration products caused by pH drop of the environment. The smart release of BTA dramatically delayed corrosion initiation of reinforced mortar and halted corrosion product accumulation on the steel surface. Therefore, the corrosion resistance of the reinforced mortar was improved after corrosion initiation.

Properties of Mortar Incorporating Spent Garnet as Fine Aggregates Replacement

The rapid growth in the construction industry has increased the consumption of fine aggregates whereby it depletes the natural resources. Also, garnet is a material that can be reused for several times in the ship cleaning process. However, when this garnet can no longer be used, it is then disposed in landfill, oceans and rivers, thus increase the volume of landfill waste and causing environmental problems. Therefore, this research is aimed to study the effect of spent garnet as a fine aggregates replacement in terms of physical, fresh and hardened properties of mortar. In this study, several specimens are prepared by using different percentage of spent garnet range from 0%, 25%, 50%, 75% and 100% as a fine aggregates replacement in mortar. The specimens are cast using 50 mm x 50 mm x 50 mm mould and the materials used in preparing the mortar sample are cement, fine aggregates, water and spent garnet. The samples are then cured in the water before tested at the age of 7, 14, and 28 days. The characteristic of the materials, fresh and hardened properties of mortar were investigated. It was found that the workability of mortar increases with the increasing amount of spent garnet. Overall, it is found out that the spent garnet can be used as fine aggregates replacement in mortar up to 50% since it has a comparable strength (40 MPa at 28 days) with a conventional mortar with 16% improvement in water absorption test. In addition, the environmental impact can also be reduced through the use of spent abrasive waste by preserving the use of natural resources.

Asian Building Techniques for Colonial Manila: Reviewing the Concept of Cultural Hybridity

Historical building techniques have been pointed out as a sample of local resistance to colonial technical influence during the early modern period, although this could not be proven by chemical analysis. A clay brick with an attached lime mortar sample was acquired from the former San Francisco Church’s foundation in Intramuros, Manila, Philippines and representative portions (BRK-1, BRK-2, BRK-3, MTR-1, MTR-2, and MTR-3) of the sample were utilized for chemical analysis using various analytical techniques. These are the energy dispersive x-ray fluorescence (EDXRF), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and ultraviolet-visible spectroscopy (UV-Vis) for quantifying organic compounds. The clay brick sample is made of typical sand and clay specifically composed of non-calcareous clay and low refractory fluxes. The brick’s firing temperature was determined to be between 600°C to 800°C in an oxidizing environment. The attached lime mortar sample is probably manufactured using crushed seashells and classified as a hydraulic lime where clayey and sand particles serving as pozzolans. The lime mortar’s microstructure shows that it is well carbonated. Possible organic compounds specifically egg whites (albumen) which may have been added to the lime mortar yielded negative results. Both qualitative tests (Xanthoproteic Test, Ninhydrin Test and Biuret Test) and quantitative assays (Biuret Assay and Bradford Assay) were not able to detect the presence of any proteinaceous compounds in the sample. It has been established based on this material sample that eighteenth century Asian builders working in Manila kept local traditions and rejected European preferences.

The initial research on the compressive strength of mortar when using bottom ash from thermal power plants to replace natural sand in construction

The paper presents the compressive strength of mortar samples when replacing natural sand by bottom ash of An Khanh and Cao Ngan thermal power plants (TPPs) in Thai Nguyen province. Experimental research is the main method applied in this research. Research results show that replacing natural sand by bottom ash in the two TPPs, the compressive strength of samples reached the required mortar’s strength. The compressive strength of the mortar sample replaced all-natural sand, particularly for masonry mortar and plastering mortar, is 10.9 MPa and 16.4 MPa respectively for An Khánh TTP, and 12.7 MPa and 12.6 MPa for Cao Ngan TTP, while the compressive strength of the motar used all natural sand, reached 13.2 MPa and 8.6 MPa.

Influence of treated mud on free shrinkage and cracking tendency of self-compacting concrete equivalent mortars

The present work aims at studying the formulation and characterization of self-compacting concrete equivalent mortars, using calcined mud from the dredged sediments brought from the dam (Western Algeria) and fly ash from the Central Thermal EDF (France). Three SCCEM samples were prepared; a control mortar sample and two mortar samples containing 22% of mineral additions, with a ratio W/B = 0.47. The analysis of the experimental results obtained indicates that mortars comprising calcined mud develop greater compressive strengths than those containing fly ash. Regarding free shrinkage, mortar with calcined mud is characterized by an autogenous shrinkage similar to those of control and fly ash mortars. However, it is more sensitive to total shrinkage and drying as compared to the other mortars. Under the conditions of restrained shrinkage, control and calcined mud mortars are more sensitive to early cracking than mortar based on fly ash.

Experimental Study on Physicochemical and Mechanical Properties of Mortar Subjected to Acid Corrosion

The 28 days cured cement mortar samples were soaked in HCl (pH = 1 and 2) and H2O (pH = 7) solutions for 90 days. By monitoring the ion concentration of H+ and Ca2+ and measuring the changes in weight loss, longitudinal wave velocity, and uniaxial compressive strength values of the corroded mortar, the physicochemical and mechanical properties of the mortar specimens were studied. Experimental results indicate that the process of the mortar sample subjected to HCL erosion has apparent stage characteristics. In the initial stage of corrosion, the chemical reaction increased the porosity of the specimen, which leads to the decrease of longitudinal wave velocity of the samples. At the same time, the corrosion solution continuously penetrates into the mortar pore system, which leads to the increase of the mass, and it is considered that the diffusion process plays a leading role during this period. Moreover, the colloidal compounds generated by the chemical reaction can not only fill the pore space but also block the continuous reaction, which led to the increase of the longitudinal wave velocity of the specimen. With the prolonging of corrosion time and infiltration path, the pH value and the concentration of Ca2+ tend to be stable, the diffusion action is weakened, and the chemical reaction is continuous, which led to the decrease of the mass and wave velocity gradually. It is considered that the chemical reaction plays a leading role in this process. Based on the induction and analysis of the test results, a generalized porosity model regarding the increase of the porosity and the decrease of effective bearing area of the mortar sample was proposed. The relation between the uniaxial compressive strength and the corrosion time of the corroded mortar is deduced, and the unknown parameters are determined based on the regression analysis of the test data.

Characterization of Mortar from Church Ruins in Barangay Budiao, Daraga, Albay

The lack of information about the correct ways of restoring historical masonry materials from cultural heritage structures tends to create more damage to the said structures. According to Cesare Brandi’s theory of restoration, existing historical materials must be replaced with their equivalent. This paper presents the chemical composition of historical mortars acquired from church ruins of barangay Budiao, Daraga, Albay, Philippines. The historical mortar sample was characterized using petrographic analysis, sieve analysis, atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), and infrared spectroscopy (IR). Petrographic analysis shows that the mortar sample is bounded by 90% organic material particularly coral and is held together by microcrystalline calcite (micrite) matrix that comprises of 10% of the total sample mortar composition. Sieve analysis shows a well-graded particle distribution. Atomic absorption spectroscopy (AAS) was also utilized to determine the %Ca for each sieve fraction using HCl for acid digestion. TGA thermograph shows the non-linear drop in weight between 740°C and 850°C, which corresponds to the degradation temperature of calcium carbonate or limestone. IR analysis shows essential characteristic peaks of CaCO3 at 712 cm-1, 874 cm-1, and 1437 cm-1.

AN INVESTIGATION ON THE USE OF BACILLUS SUBTILIS HU58 IN CEMENT MORTAR

Literature studies reveal the fact that incorporating bacteria into cement matrix could generate the formation of precipitated product of calcium carbonate. In this work, a new type of microorganism Bacillus subtilis HU58 was used as mixing component in formulating mortar sample of Portland cement and the effectiveness of self-healing character after 1 year of curing time was observed. Results showed the consequence in the enhancement of both compressive and flexural strengths of bacteria-modified mortar while comparing to a controlled mortar: 60MPa>56MPa (in compression) and 11MPa >9MPa (in flexion). Furthermore, those pre-existing artificial cracks 1mm in width of the prismatic mortar 40x40x160mm filled up partially (self-healing) by mineral glue.