Concrete biodeterioration is defined as the damage that the products of microorganism metabolism, in particular sulfuric acid, do to hardened concrete. In Canada and in the northern part of the United States, sewer failures from concrete biodeterioration are almost unknown. In the southern part of the United States and in Mexico, however, it is a serious and expensive problem in sewage collection systems, which rapidly deteriorate. Also, leaking sewage systems result in the loss of groundwater resources particularly important in this arid region. Almost every city in the Mexican-American border region, who's combined population is more than 15 million people, faces this problem. The U.S. cities have made some provision to face these infrastructure problems, but the Mexican cities have made less effort. We recommend here the Mexican norm (NMX-C-414-ONNCCE-2004) [1] to be reviewed, or at least that a warning be issued as a key measure to avoid concrete biodeterioration.

The effectiveness of lightweight aggregate (LWA) as an internal curing agent (ICA) to reduce concrete shrinkage is evaluated for repair concrete used in cultural heritage works (RCCHW) using curing periods of 30 days. Normal weight aggregate is replaced by LWA at volume replacement levels ranging from 10 to 14%. The mixtures contain Portland cement maintaining the paste content at approximately 24.1% of concrete volume. Comparisons are made with mixtures containing low-absorption granite and high-absorption limestone normal weight coarse aggregates. At the replacement levels used in this study, LWA results in a small reduction in concrete density, no appreciable effect on concrete compressive strength, and a decrease in concrete shrinkage for drying periods up to 30 days. With a curing period of 14 days, all mixtures with LWA exhibited less shrinkage than the mixtures with either low-or high-absorption normal weight aggregates.

Sulfate attack on concrete has been studied worldwide for more than 60 years. However, the mechanisms of attack are still not entirely understood, and deterioration of concrete from sulfates still occurs. The source of the sulfates may be either external or internal. External sources are the naturally occurring sulfates in the environment or those sulfates that are the product of industrial processes or various human activities (e.g. fertilizers often release sulfates into the soil and groundwater). Internal sources of sulfates may include the sulfates introduced in the cements from which concrete is made. The purpose of this study is to find out the amount of sulfates that concrete can withstand in the water. Standards tests have been developed to evaluate the resistance of concretes to sulfate attack. Some, but not all of these tests, take into account the mechanisms of sulfate attack so far discovered in research work. The tests range from those that monitor changes in the strength of concrete specimens after set periods of immersion in known compositions sulfate solutions, to those that use x- ray diffraction to examine concrete specimens for expansive products (e.g. ettringite and thaumasite) that have resulted from sulfate attack.

We present the beginning of an ambitious project to extend initiatives of education and research in optics and photonics for population with disabilities. Specifically, we describe an activity organized by different student chapters in countries of Latin America geared towards the discussion and development of materials to teach optics and astronomy with and to the visually and hearing impaired. The particular event has been completed twice, once remote, in 2020, and another hybrid in 2022, with the in-person section hosted in Bogota, Colombia with remote participants from several countries. The event aims to develop educational materials, create a space for synergy interactions between different populations, and facilitate the expansion to different languages and regions in the Americas, particularly to reach under-served and remote communities. Different spaces are proposed and quantitative outcomes are provided.

The damage that the products of microorganism metabolism, in particular biogenic sulfuric acid, do to hardened concrete is known as concrete biodeterioration. These microorganisms, Acidithiobacillus thiooxidans, Acidithiobacillus ferrooxidans and sulfate-reducing bacteria (SRB) are ubiquitous in the environment and they produce either hydrogen sulfide or sulfuric acid that can dissolve and disintegrate the concrete matrix. Their activity plays a very important function in the whole spectrum of degradation processes such as corrosion of reinforced metals and concrete.In Canada and in the northern part of the United States, concrete structure failures from concrete biodeterioration are less common than in the southern part of the United States and in Mexico, nevertheless, it is a serious and expensive problem in hydraulic structures and sewage collection systems, which rapidly deteriorate. Also, leaking sewage systems result in the loss of groundwater resources particularly important in this arid region. Almost every city in the Mexican-American border region, who’s combined population is more than 15 million people, faces this problem. The U.S. cities have made some provision to face these concrete structure problems, but the Mexican cities have made less effort. Additives and admixtures are used to improve the properties of the concrete; nonetheless, we have exposed here the importance of the factual composition of the Portland cement and concrete to mitigate concrete biodeterioration in the hydraulic structures and sewage collection systems.