Othman AlShareedah from CMCL presented his work on developing a mechanistic thickness design method for pervious concrete pavement (PCP) at the American Concrete Institute (ACI) 2019 Fall Convention in Cincinnati, Ohio. The mechanistic method involved investigating the in-situ elastic modulus and modulus of subgrade reaction of 14 PCPs across Washington State and developing a flexural fatigue model for pervious concrete pavement. The fatigue model was developed using a total of 66 PC beams made with two aggregate types (angular and round) and three porosity levels (20%, 25%, and 30%) under flexural fatigue loading in three stress ratios (SR): 0.75, 0.8, and 0.85. Recommended PCP thicknesses were proposed using the developed fatigue model, the in-situ mechanical properties of PCP, and traffic categories based on the American Concrete Institute (ACI) guide for the design of concrete parking. The developed thickness design method and the database will bridge the current knowledge gap in the structural design of pervious concrete pavement. The results are published in two papers in ASCE and C&BM journals.
CMCL was recently awarded a project by the ARPA-E program of the Department of Energy to work on using bio-based nanofibers in concrete. The focus will be on the rheology and mechanical performance of cementitious systems. In this exciting project, we work with material scientists at WSU and the Pacific NW National Laboratories to design a green effective new additive for concrete.
Our article titled, “Advanced calibration of historic apparent moisture diffusivity models for mortar” led by CMCL former student, Dr. Milena Rangelov was recently accepted for publication in ACI’s Materials J. Keep a watch out for this publication in the upcoming issue of the ACI journal. This paper provides insight into apparent diffusivity models commonly used by researchers and used in building codes by simplifying their so many parameters and providing guidance to choose suitable values.
PULLMAN, Wash. – A Portland Cement Association grant to improve concrete durability testing methods has been presented to Washington State University researcher Somayeh Nassiri.
Nassiri, assistant professor in the Department of Civil and Environmental Engineering, and her fellow researchers hope to improve the efficiency of durability testing methods for concrete by using embedded sensors to measure concrete permeability.
Unlike traditional testing methods that are conducted on cast specimens on certain test dates, embedded sensors can provide real-time and continuous data. The long-term goal of the research is to improve the durability of concrete infrastructure against road salt and deicer application and freeze-thaw cycling in cold climate regions.
The PCA is the premier policy, research, education and market intelligence organization serving America’s cement manufacturers. PCA promotes safety, sustainability, and innovation in all aspects of construction fosters continuous improvement in cement manufacturing and distribution and promotes economic growth and sound infrastructure investment.
The use of pervious concrete pavement is increasing nationwide and hence it is important to understand the structural behavior of this type of concrete. In this research, we used Lightweight Deflectometer (LWD), a simple and non-destructive test, to obtain the structural properties of pervious concrete pavement. The test is conducted by dropping the weight on a circular plate and measuring the deflection of the pavement by three sensors (as seen in the photo). LWD test was conducted on different pavement locations across Washington State including a number of streets, parking lots, and sidewalks in different structures. The goal is to use the resulted deflections from different layer thicknesses to obtain the elastic modulus and modulus of subgrade reaction (k-value) of pervious concrete which are the key parameters in rigid pavement thickness design. This will provide a database for the properties of pervious concrete at different layer thicknesses. The LWD test results will be combined with further research work on a fatigue model to provide a mechanistic design procedure of pervious concrete pavements.
Pervious concrete pavements are becoming popular in the Pacific Northwest and other areas with cold winter months. This pavement system’s high permeability offers advantages in stormwater management and can reduce flash urban flooding in areas with high rain volume.
While offering several benefits in urban areas, we know very little about pervious concrete pavement’s surface skid resistance under wet, icy and snowy and even dry conditions. In a project funded by the Pacific Northwest Transportation Consortium (PacTrans), we are empirically quantifying the surface condition of pervious concrete pavements in terms of skid resistance under those critical conditions and also when treated with deicers.
Our initial experiments (see the photo) showed a significant influence induced by the number of pores in the pervious concrete on the surface skid resistance. Next, we are characterizing skid resistance on a large database of slabs with a wide range of porosity.
This research explores Pervious Concrete Pavement (PCP), a technology that is often a desirable pavement option for city streets, bike lanes, parking lots, and sidewalks due to its fast infiltration of storm water. PCP minimizes ponding, spraying, and hydroplaning. While PCP is gaining in popularity for low-volume applications, no fatigue model is currently calibrated for use in mechanical pavement design procedures. This project will perform field and laboratory testing on several PCP installments to study how CPC fatigues. Findings from this project will be integrated into pavement design procedures, specifically PerviousPave and will be coupled with future field performance in order to create a workable fatigue model for PCP.
Our research in this area thrives to identify simple methods- mainly electrical based- to characterize the evolution of porosity in fresh concrete. We work on identifying critical markers during the hydration of cement, such as the initial and final set times, and predicting the water content and porosity of the hydrating cement paste. Our research includes studying the effect of secondary cementitious materials (SCMs) and other constituents of the mixture on the porosity of the hardened cement matrix. Capillary porosity is critical to the diffusion of vapor and ions such as chloride and sulfate, which are the cause of corrosion of the embedded reinforcement. However, due to its small scale, capillary porosity is difficult to quantify even using the costliest instruments such as the scanning electron microscopy (SEM). Our goal is to use simple methods to indirectly but accurately establish indicators of the size, distribution and other properties of the pores to predict the structure’s durability.
Anchor systems used in concrete structures are critical in all types of applications, including infrastructure (bridges, tunnels, and dams), industrial structures (heavy machinery footings, nuclear power plants) and residential projects (pipes attached to the wall or the ceiling). They must be reliable and durable, manufactured and designed to ensure of their intended application. Our industry partner-Simpson Strong-Tie (SST)’s- years of experience in the field has shown that more often than not, the hole is drilled at the wrong location for anchor installation. We are testing anchors installed in concrete slabs to establish any reduction effect that an adjacent abandoned hole may have on concrete anchor tensile capacity. Two types of anchors: torque-controlled mechanical anchors and adhesive anchors with different diameters, embedment depths from different manufacturers will be tested to build a database. The test results will be first statistically analyzed. Then, Finite Element Models (FEM) based on elasticity theory, plasticity theory, bond-slip relationship, and fracture mechanics will be developed and validated by the results.