Concrete structures are susceptible to cracking during their service life. These cracks become the main route through which liquids and aggressive agents penetrate into and through concrete mass. Does the use of fibers in concrete result in a reduction of crack widths compared to concrete without fibers? Does crack width reduction correlate with maintaining a lower permeability, thus improving the long-term durability of a structure?

Core testing is the most direct method to determine the compressive strength of concrete in a structure. Generally, cores may be obtained to assess whether concrete in a new structure complies with strength-based acceptance criteria or to evaluate structural capacity of an existing structure based on in-place concrete strength. In either case, the process of obtaining core specimens and interpreting strength test results is often confounded by various factors affecting in-place concrete strength or the measured strength of a test specimen. The scatter in strength test data, which is unavoidable given the inherent randomness of in-place concrete strengths and the uncertainty attributable to preparation and testing of the specimen, may further complicate compliance and evaluation decisions. This guide summarizes practices for obtaining cores and interpreting core compressive strength test results. Factors that affect in-place concrete strength are reviewed so sampling locations that are consistent with objectives of the investigation can be selected. Strength correction factors are presented for converting measured strength of nonstandard core-test specimens to strength of equivalent specimens with standard diameters, length-to-diameter ratios, and moisture conditioning that have been derived using data for normalweight concrete with strengths between 2000 and 13,400 psi (14 and 92 MPa). This guide also provides direction for checking strength compliance of concrete in a structure under construction and methods for determining equivalent specified strength to assess existing structure capacity.

Concrete parking lots serve many kinds of public facilities, commercial and retail developments, businesses, and multifamily housing projects. They primarily accommodate parked vehicles but may also provide maneuvering areas and access for delivery vehicles. The design and construction of concrete slabs for parking lots and outside storage areas share many similarities with the design and construction of industrial pavements, streets, and highways, but they also have some very distinct differences. A full appreciation of the differences and the modification of design and construction procedures to take these differences into account can result in economical concrete parking lots that will provide satisfactory service for many years with little maintenance. This guide includes information on site investigation, thickness determination, design of joints and other details, durability considerations, paving operations, and quality-assurance procedures during construction. Maintenance and repair are also discussed. Information related to the design and construction of concrete site paving for industrial and trucking facilities is in ACI 330.2R.

Concrete parking lots serve many kinds of public facilities, commercial and retail developments, businesses, and multifamily housing projects. They primarily accommodate parked vehicles but may also provide maneuvering areas and access for delivery vehicles. The design and construction of concrete slabs for parking lots and outside storage areas share many similarities with the design and construction of industrial pavements, streets, and highways, but they also have some very distinct differences. A full appreciation of the differences and the modification of design and construction procedures to take these differences into account can result in economical concrete parking lots that will provide satisfactory service for many years with little maintenance. This guide includes information on site investigation, thickness determination, design of joints and other details, durability considerations, paving operations, and quality-assurance procedures during construction. Maintenance and repair are also discussed. Information related to the design and construction of concrete site paving for industrial and trucking facilities is in ACI 330.2R.

The conversion of a historic brewery in Bavaria, Germany, into an office and events space posed a challenge: the need to replace five large stone window frames while retaining the original aesthetic of the façade. Using computer-aided design files specifying the geometry of the window frames, digital patterns were created to print polymer formwork elements that were successfully used to cast the window frame elements.