In this article, we are going to discuss the reasons that asphalt concrete pavement deterioration happens. Damage to concrete structures (concrete) caused by cracks, deterioration, amorphization, and delamination can result in disaggregation (concrete broken down into very small particles) and hollowing out of the concrete. 4-5 hours after a snow melting agent has been sprayed on the surface of concrete pavements, large amounts of aggregate pop out, causing damage. Surface course disaggregation, blistering, cracking, and peeling have also been known to cause damage to asphalt runways and highways. Damage from disaggregation, cracks, and pop-out of aggregate in concrete and asphalt structures has long been regarded as strange and unexpected. Following extensive testing, it was determined that trace quantities of organic matter (TQOM), air entrained (AE) water reducing agents in cement and/or air, and surfactant in snow melting agents were to blame for all unexplained types of damage to both asphalt pavements and concrete structures. Chemical analysis was used to identify the sources of these unexpected and perplexing phenomena, such as TQOM emissions and organic substances. TQOM substances include sodium polyoxyethylene nonyl phenyl ether sulfate, amine compounds, phosphate compounds, and phthalate compounds (phthalates are defined further below) (SPNES).
SPNES is a surfactant that can be found in windshield washer fluid. Other critical damage indicators discovered by us include the amount of water and organic matter present in damaged concrete and asphalt structures. This study also proposed a new amorphization evaluation method that appears appropriate for assessing the safety of concrete structures alongside roads exposed to TQOM in extremely polluted environments. It is critical to address the issues that cause damage in cement concrete structures in order to extend the useful life of the structures. To investigate the damage, a phenolphthalein solution is frequently applied to a cross-section of concrete, and the degree of concrete deterioration is determined by the color of the reaction products or the pH level (amount of hydroxide ions: OH-). However, judging concrete damage solely by the pH level found on the concrete's surface appears insufficient. The use of phenolphthalein and the crack width (0.2 mm or greater) on the concrete surface serves as the foundation for assessing damage to modern concrete. However, little research has been conducted on the severity of concrete damage and the relationship between cracks and deterioration. As a result, determining the depth and length of repairs required for previously thought-to-be-damaged concrete structures is impossible.
For this reason, it is necessary to develop a new technique for assessing damaged samples that incorporates various chemical elements of the concrete. Furthermore, in indoor tests, cement concrete structures exhibit unexplained damage far exceeding that caused by carbon dioxide. According to the findings of this study, the effectiveness of modern evaluation techniques for detecting concrete damage is limited. Delamination near the surface, disaggregation (concrete broken down into very small particles), amorphization (cement crystal components turned into an amorphous substance), cracks, and aggregate pop-out are all examples of seemingly unexpected and unexpected phenomena in modern concrete structures. The mechanisms underlying surface course disaggregation and peeling off on asphalt pavements in airport runways and on roads have yet to be identified. Disaggregation has occurred in concrete bridges at the intersection of concrete slabs and asphalt pavements. The useful lives of concrete and asphalt pavements are shortened as a result of this damage, which also jeopardizes their safety. As a result, resolving the causes of the damage and developing new evaluation techniques for the damage caused by deterioration are urgent and critical issues from the standpoint of structural safety.
We investigated the possibility that trace amounts of unknown organic matter were responsible for some of the unexplained concrete damage in this study. This theory was supported by the unusual odor that commercially available cement emits when mixed with water. TQOM, which has not yet been identified in fresh cement but is present in the air, is assumed to contribute to the unusual damage to concrete structures and asphalt pavements in this study. To investigate this, numerous samples were taken from damaged concrete buildings and asphalt pavements where various unexplained phenomena had occurred. Furthermore, substances that have not yet been identified were sought from these in order to investigate these causes, as well as the relationship between these causes and the strange phenomena. Based on the results of the various experiments, it was determined that TQOM and AE water reducing agents in cement and/or air, as well as surfactants in snow melting agents, were responsible for all of the strange damage sustained by both types of structures. This study proposed a novel method of assessing damage to concrete structures and asphalt pavements. Furthermore, the use of a microfocus CT scanner as a new method of evaluating concrete structure damage was proposed (CT). Damages such as disaggregation, delamination, amorphization, and cracks were thought to be caused by the materials (aggregate, asphalt), type and content of TQOM in the air and/or fresh cement, construction technique, construction equipment used, environmental factors such as temperature and relative humidity, and surfactants in snow melting agents.
The following 11 types of themes were chosen for the current study in order to understand the causes and mechanisms of damages (disaggregation, delamination, amorphization, and cracks) in concrete structures and asphalt pavements, and numerous tests were performed.
- Determining the specifics of the strange smell caused by TQOM in fresh cement during mortar preparation (quality of cement),
- The volume of mortar samples increased as a result of multiple chemical TQOM components in cement (TQOM, quality of cement, AE water reducing agent),
- Mortar sample delamination as a result of TQOM separation (construction method and vibration processed),
- TQOM-induced mortar amorphization in new cement (TQOM, quality of cement, construction method)
- Comparison of damage (crack widths and crack lengths) between 120-year-old and modern mortar samples (quality of cement, TQOM),
- Degradation of mortar samples due to various chemical components of TQOM in freshly mixed cement (quality of cement, construction method)
- Aggregate pop-out caused by surfactants in snow melting agent and TQOM in cement (aggregate, concrete structure, surfactant of snow melting agent),
- Emissions and total suspended organic matter (TSM) sources in the environment (air pollution, environmental conditions),
- Water was found to have permeated through waterproofing sheets in cored samples from a new concrete bridge after transient moisture permeation tests (described in section 2.2.5). (structure, material, environmental condition),
- The material, TQOM in the air, multiple emission sources, and chemical organic matter components in damaged concrete structures and asphalt pavements
- The cause of disaggregation in damaged concrete structures and asphalt pavements (material, structure, construction method).
It was determined that an understanding of these concepts is required in the disaggregation of concrete structures and asphalt pavements.
Asphalt Cement Deterioration
Eleven different types of asphalt cement from seven different countries were gathered to investigate the cement's quality to susceptibility to damage of mortar samples and to be used to investigate the level of deterioration in new mortar samples. In this study, the contents and chemical components of TQOM in fresh cement were investigated using Nittetsu Portland cement (also known as Nittetsu cement), a standard modern cement used in Japan. The 120-year-old sample (referred to as the 120-year-sample in the following) is thought to have had a reasonably long useful life as a mortar sample created 120 years ago in Otaru, Hokkaido, Japan, and kept indoors at room temperature for that entire time. The makeup and shape of the 120-year sample are as follows. Asano Ordinary Portland Cement was used for the mortar sample. The mortar sample was 4.5 cm wide, 8 cm long, and 2.2 cm thick. It was made up of 1:0.5:3 cement, volcanic ash, and sand, with a water content of 44%. The 120-year sample was made from old cement and did not contain any AE water-reducing agent (silica, clay, and limestone). In this sample, natural sand and volcanic ash were used. The new mortar samples measure 2 x 2 x 2 cm and have a cement-to-sand ratio of 1: 2 and a water-to-cement ratio of 50%. All new mortar samples contained AE water reducing agent (Pozzolith 70; 0.25% x cement) and Toyoura standard sand (high silica content, maximum particle size: 0.3 mm, coefficient of uniformity: 1.71). Using mortar samples, the extent of deterioration caused by TQOM and AE water reducing agents, amorphization, delamination, cracks, and volume expansion were investigated. The TQOM of the crushed 120-year sample was also examined.
The damage to concrete structures was assessed in this study using two different types of structures: concrete bridges and runway pavements. The newly constructed concrete bridge was composed of a concrete slab (thickness: 16 cm; compressive strength: 24 MPa; AE water reducing agent: 1% cement; water/cement: 55%) and two layers of asphalt pavement with a waterproofing layer. The old cement bridge, built in 1934 (Tokachi bridge: slab: 30 cm, two-layered asphalt pavements: 7 cm), was destroyed in 1980. There were no waste products or AE water-reducing agents used in the cement's production. The surface (0-3 cm) of core samples was used to select the samples for the foundation (width: 40 cm, height: 45 cm) of the Tokachi bridge's hand-rail and bridge pier (diameter 10cm). The thirty-year-old disaggregated concrete protective wall measures 1 m in height, 20 cm in width, and 50 cm in height and width for the wall bed. The wall and wall bed were held together by reinforced concrete. It is situated in Kobe on the median strip of an elevated highway. Samples of disaggregated concrete (disaggregated concrete wall) were collected from the Kobe highway for this study. The runway concrete pavement (30 cm) at Chitose Airport in Japan was damaged by a snow melting agent. Concrete disintegration and aggregate pop-out were observed on this runway. The concrete in the concrete runway is made up of the following ingredients. Slump: 2.5 cm, Nittetsu cement, AE water reducing agent (Pozzolith 70; 0.25% cement). These samples were used to investigate damaged concrete pavement (30 cm) of runway concrete divided into 9 layers, volume expansion of mortar, and aggregate damage caused by the snow melting agent's surfactant. The organic materials in Nittetsu cement and a crushed 120-year sample were extracted four times using a Soxhlet extractor and chloroform solution (over the course of 24 hours). It's known as "substance extracted with Soxhlet." The following substances were identified as TQOM in cement using GC-MS. Di-(2-ethyhexyl) phthalate (DEHP) and Di-(butyl) phthalate (DBP) were both found in 119 and 2 g of Nittetsu cement, respectively.
The 120-year sample in 10 g of Asano Portland cement contained 1 g of DBP, 0.1 g of DEHP, and trace amounts of 2, 2, 4-trimethyl-1, 3-pentanediol di-isobutylate (TMPDIB: Texanol). These elements are TQOM in the 120-year air sample. The organic material in the 120-year sample was believed to have come from the air. The above result suggests that the strange odors released by cement containing TQOM-like phthalates (DBP, DEHP) when in contact with water are possibly caused by chemical hydrolysis of phthalates in the cement and that the organic materials present in cement were instantly hydrolyzed and produced the odor of 2-ethyl-1-hexanol gas and/or butanol. The smell appeared instantly while making the mortar samples with the 9 different types of cement, but not with the extracted cement (cement extracted organic matter from Nittetsu cement with Soxhlet and chloroform solution), indicating that this cement contained trace amounts of phthalates. It is believed that TQOM in cement has no effect on the wear and tear of concrete buildings and asphalt roads. ICP detected 0.12% phosphate compounds (Nittetsu cement) that are not dissolved in chloroform solution and thus cannot be extracted using this method (emission spectral analysis: ALS Chemex Ltd., Canada). These experiments show that commercially available Nittetsu cement contains phthalates and phosphate compounds, and that modern concrete structures are also exposed to trace amounts of surfactants found in snow melting agents. Researchers investigated the effect of surfactants on the deterioration of concrete caused by damage using cement paste samples (mixtures of cement and water) (T. Tomoto, Constr. Build. Mater. 25 (1) (2011) 267-281). In this test, calcium that is both water-soluble and refractory is produced as a result of an instantaneous reaction in aqueous solutions with trace amounts of surfactants between cement paste and the chemical constituents of cement (anionic and nonionic). Furthermore, it is well known that in aqueous solutions, very small amounts of phosphate compounds found in meat-and-bone meals react with calcium constituents. Given the foregoing, it is possible that these organic components (TQOM) associated with phosphate compounds in cement influence unexplained concrete damage and degradation.