Integral mixing using nano silicon for concrete waterproofing

Permeation of water and other aggressive fluids in concrete can result in degradation and other aesthetic problems. Consequently, these affect the service life of concrete structures. A number of research studies were undertaken to extend the service life of concrete infrastructures using various waterproofing agents. To this effect, a great deal of repair and maintenance cost can be avoided. The aim of this study is to investigate and establish waterproofing performance of nano silicon-based mortar. In this regard, nano silicon was characterized using Field Emission Scanning Electron Microscope (FESEM), Energy Dispersion Spectroscopy (EDS), Fourier Transformed Infrared (FTIR), X-Ray Diffraction (XRD), surface zeta potential and Water Contact Angle Test (WCA). Response Surface Methodology (RSM) was employed to establish the optimum mix ratio. The relationship between the experimental factors and response was modelled and validity of the model was further evaluated to ensure accurate predictions. To establish precision of the mathematical model, an experiment was planned based on Central Composite Design (CCD). The model was investigated using Analysis of Variance (ANOVA). Optimum mix ratio, necessary to increase resistance to water absorption was established at nano silicon dosage of 6.6% by weight of cement and w/c of 0.42. Furthermore, an appropriate experimental control test steps for producing waterproof cement mortar was designed. In this regard, necessary test methods from established standards were adopted to constitute supporting structure of the approach. Besides, the results were validated using macro and microstructure tests and indicated that water resistance to capillary absorption of cement mortar increased to 62%. Likewise, water absorption by immersion increased by 37%. Furthermore, resistance to water vapor transmission rate increased to 52%. On the other hand, resistance to gas permeability increased to 31% as compared to reference specimen. Moreover, while the volume of water permeable voids for nano silicon-based mortar was 16.9%, the total porosity of the same specimen was 14%. Macrostructure test indicated a good quality mortar specimen recorded an Ultra Sonic Pulse Velocity (UPV) value of 3623 (m/s). In addition, FESEM and XRD indicated the formation of a crystalline hydrophobic thin film layer of nano silicon within the pore structure of the mortar specimen. In conclusion, the nano silicon-based mortar has been proven to have a good resistance to water permeation

Waterproof performance of concrete: a critical review on implemented approaches

Permeation of water and other fluids in concrete can result in degradation and other aesthetic problems which shorten concrete structures' life. Several studies have been undertaken to produce waterproofing additives that extend the service life of concrete elements. Consequently, a great deal of repair and maintenance costs could be avoided. This paper aims to review the studies which have used various agents and tests to evaluate the waterproofing efficiency of concrete. The study establishes the taxonomy and construct of research in concrete waterproofing research. Study established frequency aggregation of different additive used and tests applied. The technique adopted by majority of the researchers was the use of surface coating. Water absorption was found to be the most common test in this research area. Study delineated that most researchers focused on the use of polymer-based materials, silicates containing compound, silanes, siloxanes, cementing materials and some nano materials. Finally, study established three classification of additives based on material structure, method of application and additives functions

Causes of variation order in building and civil engineering projectsin Nigeria

Variation does not only affect labour productivity but also leads to the dispute, time and cost overrun. Consequently, it affects projects performance. It is, therefore, imperative for construction professionals to eliminate unnecessary additional cost from a project so as to optimize the client’s benefit against input resources. This paper identifies and examines the most significant causes that contribute to the variation orders. Also, Nigerian construction industry is used as a case study. Variation orders causing factors were assessed. Questionnaires were administered to clients, consultants and contractors to elicit information regarding variation causing factors. These factors were analyzed using frequency aggregation, mean score method and subsequently ranked according to their severity. The result revealed three most significant causes of variation which are: ‘Change of plan’’ with the highest frequency of 58% then followed by ‘‘Conflicting contract documents (50%). The next most frequent causing factors were the “substitution of materials” and “change in design” each with frequency of 43%. The least causing factor of variation was the “error and omission in design” with the frequency of 10%. Also differing site condition, new government regulation, weather condition were identified as other cause of variation with the frequency of 27%, 29% and 10% respectively. It has also shown that most critical source of variation order is the client due to change of plan then followed by consultant due to conflicting contract document

Strength and Microstructure of Concrete with Iron Ore Tailings as Replacement for River Sand

River Sand is one of the basic ingredients used in the production of concrete. Consequently, continuous consumption of sand in construction industry contributes significantly to depletion of natural resources. To achieve more sustainable construction materials, this paper reports the use of iron ore tailings (IOT) as replacement for river sand in concrete production. IOT is a waste product generated from the production of iron ore and disposed to land fill without any economic value. Concrete mixtures containing different amount of IOT were designed for grade C30 with water to cement ratio of 0.60. The percentage ratios of the river sand replacements by IOT were 25%, 50%, 75% and 100%. Concrete microstructure test namely, XRD and Field Emission Scanned Electron Microscopic/Energy dispersive X-ray Spectroscopy (FESEM/EDX) were conducted for control and IOT concretes in order to determine the interaction and performance of the concrete containing IOT. Test results indicated that the slump values of 130 mm and 80 to 110 mm were recorded for the control and IOT concretes respectively. The concrete sample of 50% IOT recorded the highest compressive strength of 37.7 MPa at 28 days, and the highest flexural strength of 5.5 MPa compared to 4.7 MPa for reference concrete. The texture of the IOT is rough and angular which was able to improve the strength of the concrete

Strength and Microstructure of Concrete with Iron Ore Tailings as Replacement for River Sand

River Sand is one of the basic ingredients used in the production of concrete. Consequently, continuous consumption of sand in construction industry contributes significantly to depletion of natural resources. To achieve more sustainable construction materials, this paper reports the use of iron ore tailings (IOT) as replacement for river sand in concrete production. IOT is a waste product generated from the production of iron ore and disposed to land fill without any economic value. Concrete mixtures containing different amount of IOT were designed for grade C30 with water to cement ratio of 0.60. The percentage ratios of the river sand replacements by IOT were 25%, 50%, 75% and 100%. Concrete microstructure test namely, XRD and Field Emission Scanned Electron Microscopic/Energy dispersive X-ray Spectroscopy (FESEM/EDX) were conducted for control and IOT concretes in order to determine the interaction and performance of the concrete containing IOT. Test results indicated that the slump values of 130 mm and 80 to 110 mm were recorded for the control and IOT concretes respectively. The concrete sample of 50% IOT recorded the highest compressive strength of 37.7 MPa at 28 days, and the highest flexural strength of 5.5 MPa compared to 4.7 MPa for reference concrete. The texture of the IOT is rough and angular which was able to improve the strength of the concrete