Wilfrido Martínez-Molina

Predicting Concrete Compressive Strength and Modulus of Rupture Using Different NDT Techniques

Quality tests applied to hydraulic concrete such as compressive, tension, and bending strength are used to guarantee proper characteristics of materials. All these assessments are performed by destructive tests (DTs). The trend is to carry out quality analysis using nondestructive tests (NDTs) as has been widely used for decades. This paper proposes a framework for predicting concrete compressive strength and modulus of rupture by combining data from four NDTs: electrical resistivity, ultrasonic pulse velocity, resonant frequency, and hammer test rebound with DTs data. The model, determined from the multiple linear regression technique, produces accurate indicators predictions and categorizes the importance of each NDT estimate. However, the model is identified from all the possible linear combinations of the available NDT, and it was selected using a cross-validation technique. Furthermore, the generality of the model was assessed by comparing results from additional specimens fabricated afterwards.

Cement-Based, Materials-Enhanced Durability from Opuntia Ficus Indica Mucilage Additions

Physical characterization tests were performed on cement-based mortar containing different addition levels (0, 1.5, 4, 8, 42, and 95%, by water replacement concentration) of opuntia ficus indica (OFI) mucilage. Cement mortar cubes prepared with and without mucilage were tested 2145 days after being fabricated. These preliminary findings suggest that the addition of OFI mucilage at water replacement concentrations between 4 and 8% (by water mass replacement) may be suitable for durability-enhancing applications in cement-based mortar.

Physical Properties of Cement-Based Paste and Mortar With Dehydrated Cacti Additions

This article presents results for the physical characterization of mortar cubes fabricated with botanical (green) dehydrated additions such as nopal (Opuntia ficus indica) and aloe vera. A total of 84 mortar cubes were fabricated with and without these natural additions and tested for a period up to 900 days. Mortar without such additions served as controls. The natural dehydrated additions, nopal and aloe vera, were mixed with CPO cement (the name used in Mexico for type I Portland cement) at different percent replacements (0%, 1%, 2%, and 4%). To characterize physical properties of such mixtures, four tests were performed at ˜900 days: total void content, compressive strength, ultrasound wave propagation, and wet electrical resistivity. Marginal improvements were observed within the dehydrated aloe vera replacement mixtures. Dehydrated nopal additions did increase the physical performance of the mortar with time.

Influence of the Organic and Mineral Additions in the Porosity of Lime Mortars

The main objective was to determine the effect of additions of cactus mucilage (colloquially called cactus slime which on drying produces weddellite and whewellite crystals, calcium oxalates) and/or volcanic ash in masonry mortars made with lime, on the properties as mechanical resistance to compression, tension and bending, and the physical properties such as porosity which,leachates and capillary absorption. The Fagerlünd method was used, on lime mortar specimens according to ASTM standards. Four mortar mixtures were debeloped: with additions and without them, like sample witness. The lime is slaked handcrafted and comes from Piedras de Lumbre Quarry Stone, Zitacuaro, Michoacan, Mexico; the volcanic ash is a mud from Acambaro, Guanajuato, Mexico and the fine aggregate, sand, proceeds from Joyitas Quarry stone in Morelia, Michoacan, Mexico. A correlation of the mechanical properties of the four mortar mixes versus its degree of porosity was made. Porosity and absorption were affected by the mucilage and/or ashes addition increasing the mechanical strength; however this was not the aim of the research, since it is not intended that the mortars were rigid, it was intended that they were capable of absorbing deformations of the natural stone masonry. The addition of mucilage and/or ash, did reduce the percentage of total porosity, the cactus mucilage when dried formed crystals of whewellite and wheddellite which filled in the pores of the mortar matrix, and the ash, mud, as it is an igneous extrusive stone, in crypto crystallite form, it presented puzolan activity forming new minerals filling the matrix pores.

Damaged and Healthy Ignimbrites from the Surroundings of Morelia, Mexico; Uses for Restoration of the Colonial Inheritance

The historic centre of Morelia, Mexico has over a thousand architectonic monuments catalogued. This allowed the city to become part of the list of world heritage site by UNESCO in the 90s of 20th century. The location of Michoacan, the State in which Morelia is the capital, allowed it to have an abundance of acidic extrusive igneous rocks such as the ignimbrite quarry stones. The ignimbrites were carved into blocks to build vertical elements such as the walls and the foundations. Cases of carved and sculpted blocks were not designed to be coated with mortars, non sculpted ignimbrites were used in the case of buildings that were designed to carry coatings mortars and/or paintings; constructions in which the time to build was small, the money was scarce or the destination was not particularly important. These monuments are colonial ones, the European brought building techniques in vogue in Europe; books written by Vitruvius, Palladio and Alberti were adapted to local conditions as ethnic and regional materials and costumes. Ignimbrites, after exposed to the environment have begun to damage on the blocks posted as facades. In cases of severe exfoliation or acute devitrifying of the matrix in the ignimbrites, it is necessary to replace the damaged blocks by healthy rocks earned from the quarry stones of the surrounding places but it has not been able to find full match between rocks; sometimes do not match the resistance, porosity, durability, color or geographical location in the historical archives. Results to date show matches and the discrepancies between the different quarry stones and uses that are targeting in heritage buildings.