Emerging Rapid Aggregate and Concrete Test Methods for Formulating Asr-Resistant Concrete

The main objective of this study was to develop rapid aggregate and concrete test methods and a combined innovative approach for formulating performance based ASR resistant concrete mixes. An innovative step by step approach has been developed to formulate ASR resistant concrete mixes based on four recommended steps. In step 1, determination of aggregate ASR composite activation energy (CAE) and threshold alkalinity (THA) by using a rapid aggregate chemical test called volumetric change measuring device (VCMD) is performed. The lower the CAE the higher the reactivity is. Based on the measured CAE and THA, mix design formulation is conducted in step 2 by applying mix design controls and special protection measures. In step 3, verification and adjustment of the mix developed in step 2 is performed based on THA and pore solution alkalinity (PSA) relationship - PSA needs to be below THA in order to prevent/minimize ASR. Mix design validation by using a newly developed accelerated concrete cylinder test (ACCT) is a part of step 4. Job concrete mixes made of aggregates with different levels of ASR reactivity were tested using the above approach with the four steps. The CAE-based method shows better correlation with ASTM C1293 than ASTM C1260 and was found to be effective to consistently identify the aggregates belong to false positive (i.e., failed by C1260 but passed by C1293) and negative (passed by C1260 but failed by C1293) categories. The proposed approach has the ability to rapidly assess the ASR potential of each aggregate at various alkali loadings and tailoring mix design depending on the level of protection needed

A Novel Multiscale Modelling Approach for Evaluation of the ASR in Concrete Structures

This paper presents a new multiscale approach for evaluation of the volume change in concrete structures due to the alkali-silica reaction (ASR). A practical step by step approach that can be applied to the real structures is developed based on combined experimental and numerical assessment by considering the most influential ASR parameters at different scales. In the first step, the ASR expansion is measured using accelerated concrete cylinder test (ACCT) for different concrete mixtures covering different variables of important factors such as mix design (e.g., w/cm, fly ash type and replacement percentages), aggregate reactivity, alkali loadings, temperature, and relative humidity etc. All measured expansion data are then modelled using artificial neural network (ANN) modeling approach in the second step. In the third step, finite element (FE) model is utilized at different scales to analyze the real structures and representative volume element (RVE) taking into account the ASR gel expansion and structural boundary conditions. Finally, the effects of the structural constraints are taken into account by introducing correction factors to the predicted free expansion (i.e. no constraints) of the RVE by ANN model. It was found that a combined effect of both internal gel pressure and structural constraints determines the net volume expansion in a concrete structure. In order to show the applicability of the proposed approach, the model is employed for evaluation of the ASR-induced net volume expansion at different locations of a dam structure under realistic in-service conditions. The microstructural study was also done by using X-ray CT that can be used to estimate the ASR progress in concrete structure and validate / support the FEM based predictions

RECYCLING AND REUSE OF MATERIALS IN TRANSPORTATION PROJECTS —CURRENT STATUS AND POTENTIAL OPPORTUNITIES INCLUDING EVALUATION OF RCA CONCRETE PAVEMENTS ALONG AN OKLAHOMA INTERSTATE HIGHWAY (FHWA-OK-18-04)

Oklahoma Department of Transportation (ODOT) is committed to protect and enhance human and natural environment while developing a safe, economical, and effective transportation system. The first objective of this research was to evaluate the availability of the recycled materials and develop strategies for increasing use of recycled materials in ODOT transportation construction projects. In this objective, an extensive literature search was conducted to acquire information pertaining to properties, current practices, and available field investigations of the commonly used recycled materials. Use of recycled concrete aggregate in concrete paving mixtures (RCA-CPM) was determined to be the major focus in this research as applications of RCA-CPM by ODOT and other DOTs have been reported as a sustainable and durable construction practice. Subsequently, a review of the key findings pertaining to RCA material properties and effects of RCA on portland cement concrete pavement (PCCP) performance was performed. Additionally, a life cycle assessment addressing all the three aspects of sustainability (i.e., economic, social, and environmental) was performed to do a comparative assessment between RCA-PCCP and plain PCCP and project the benefits of using RCA-CPM. The second objective was to evaluate the long-term performance of existing PCCP made with RCA in Oklahoma. A jointed plain concrete pavement (JPCP) and a continuously reinforced concrete pavement (CRCP) section were selected and evaluated through various tests covering different aspects, which includes visual survey, determination of mechanical properties, petrographic examination, and evaluation of the existing base through falling weight deflectometer (FWD). From the lab and field studies, it was verified that good base support, strong load transfer, and shorter joint spacing are essential design considerations for JPCP made of RCA-PCC. CRCP using effective anti-corrosion measures might be more suitable for implementing RCA-PCC; CRCP could better protect the base from erosion caused by higher differential energy and help restrain high drying and thermal volume change of RCA-PCC.Final Report October 2016-September 2018N

The Impact of Extended Heat Exposure on Rapid Sulphoaluminate Cement Concrete Up To 120°C

This study examined the stability of rapid sulphoaluminate cement concrete (R-SACC) when exposed to heat for extended periods of time. The physicochemical processes present in R-SACC as a function of temperature were determined through various tests. The general behavior of rapid sulphoaluminate cement (R-SAC) at a range of temperatures is summarized. The results show that observing color change could be a simple way to identify deterioration of R-SACC, along with the rebound hammer. The matrix formation of ettringite was broken and the mass of the hydrated product decreased with heat exposure; the major mineral composition of the paste consisted of CaSO4, CaCO3 and β-C2S; and the interface between aggregate and paste in the R-SACC become loosely structured with cracks. Between 50°C and 120°C, the rapid sulphoaluminate cement (R-SAC) paste first expanded and then shrank, and the shrinkage rate of R-SAC was much greater than that of R-SACC

0-6656-01: Further Validation of Alkali-Silica Reaction (ASR) Testing and Approach for Formulating ASR Resistant Mix

0-6656-01Alkali-silica reaction (ASR) is recognized as a major concern for the Texas Department of Transportation (TxDOT). In the previous project 0-6656, a volumetric change measuring device (VCMD)\u2013based aggregate chemical method was validated as a rapid (within 5 days) and reliable method to determine aggregate reactivity in terms of measuring composite activation parameter (CAP) and measure aggregate threshold alkalinity (THA). A new accelerated concrete cylinder testing (ACCT) was developed in that project as a potential concrete ASR test

0-6941: Direct Determination of Cement Composition Using X-ray Diffraction [Project Summary]

0-6941This project established protocols and specifications for the direct determination of cement composition by Quantitative X-ray Diffraction (QXRD). The main objectives of this research were: 1) developing protocols for routinely performing QXRD testing, 2) testing the effectiveness of the protocols using commercial cement samples, and 3) documenting the potential qualitative and economic benefits of utilizing QXRD. Researchers developed a state of the art QXRD methodology through regular collaboration and knowledge transfer with industrial experts. In addition to the important findings, further recommendations to improve the current phase quantification were proposed to address some of the gaps in existing research and testing. Researchers predicted the financial implications using life-cycle cost analysis procedures if industrial quality control adopts these protocols. The conclusions, both important and supplementary, were recorded with recommendations for future implementation projects