This study investigates the mechanical and transport properties of polymer-modified repair composites developed with Portland pozzolana cement (PPC), river sand, styrene acrylic ester-based polymer (SAR), metakaolin (MK), and silica powder (SP). Eight distinct combinations of repair composites were formulated under the two major categories of MK and SP to evaluate their performance. Cement and sand were each substituted with 10 % MK and SP, respectively. In both types, polymer modification was performed at 1, 2, and 5 % by weight of cement. By conducting compressive, flexural, splitting tensile, and shear strength tests, the developed repair composites mechanical properties were investigated. Water absorption and sorptivity tests were performed to evaluate the transport properties. Incorporating synergy aspects, the results of this study demonstrate improved mechanical and transport properties for MK and SP-based repair composites modified with SAR. The optimum dosage was found as 2 % for both MK and SP-based repair composites, considering economy aspects versus performance.
Due to the shortage of natural coarse aggregate, demolition of old concrete deposits are incorporated into structural concrete after various surface treatments. The presence of adherent mortar on the exterior of the recycled aggregate tends to degrade the properties of the recycled coarse aggregate. To eradicate the old mortar on the recycled aggregate, there are several types of treatment. In this current study, we discuss the different treatment methods, namely mechanical scrubbing, sulphuric acid, hydrochloric acid, cement coating and silica fume coating treatments. Each techniques is uniquely analyzed and the results are also analyzed for each and every methods. Treating recycled aggregate with all treatment methods improves its physical, mechanical and durability properties compared to untreated concrete made from recycled coarse aggregate. All techniques show their best results from their treatment. Some of the techniques are environmentally friendly and cost-effective for the treatment method. Fresh concrete properties are enhanced by 20.79 % after using abrasive treated recycled aggregates and its most effective treatments for enhancing fresh properties. The compressive strength of recycled aggregate concrete reduced significantly by 23.96 % after abrasive treatment it’s enhanced by 17.85 % at 28 days when compared to controlled concrete.
Geopolymer concrete prepared using fly ash is a unique environment friendly construction material. It is essential to know the hardened properties of geopolymer concrete (GPC) for design purpose. For better density well graded aggregate is needed. In most of the rivers, coarser sand is available which is less suitable as a fine aggregate for concrete. However, the fine sand is abundantly available in the creek, which is called sea sand. In this work the fly ash based GPC has been prepared with 45 % river sand plus 55 % treated sea sand as a fine aggregate. It is impossible to provide the hot air (temperature) curing to fly ash GPC structural elements. Push-off shear strength of GPC has been evaluated of four different mixes of fly ash with temperature curing and ambient curing. ordinary Portland cement (OPC) is added by 4 % in the mixes of ambient curing. For compressive strength 100 mm size cubes and for shear strength the push-off specimens (S-shaped) of 100 × 100 × 300 mm have been casted. Toughness for shear has been evaluated from load deflection curve. The results show the geopolymer concrete with temperature curing gives greater shear strength than that of geopolymer concrete with ambient curing. But geopolymer concrete with ambient curing gives the higher shear strength than the similar grade of cement concrete.
This study utilises moisture distribution profiles harvested from literature and gravimetric observations made in the laboratory to analyse the robustness of three Boltzmann-profile, ?n(?) models which were previously adopted by various researchers for the modelling of non-linear hydraulic diffusivity, D(?n) of drying mortar and concrete. Such an analysis is necessary to ensure that the D(?n) data is reliable and free from modelling artefacts. A 2-parameter ?n(?) model is found to be better suited for the inverse estimation of D(?n) in comparison to a widely used 3-parameter model. The 2-parameter model captures the effects of water-to-cement ratio and temperature on D(?n) in accordance to the physics of the drying phenomenon. Also, it does not cause a sudden drop in the diffusivity curve near high saturation levels as is noted with the 3-parameter model. It is further noted that the 3-parameter ?n(?) model fails to fit low ?n - low ? data which is typically obtained using non-destructive imaging techniques. The 2-parameter model can fit low ?n - low ? data and is also suitable for high ?n - low ? data, obtained through gravimetric experiments, within the limit of ?n < 0.80.
