Use of Prefabrication, Construction and Demolition Wastes as an Aggregate in Vibropressed Precast Concrete Blocks Production

The aim of current study was to determine the recycled concrete aggregate (RCA) applicability in the production of concrete mixture for vibropressed concrete blocks. The experiments were focused especially on the crushed waste material from the same concrete elements producing plant. For this type of precast elements only some finer fractions can be implemented and the “earth-moist” consistency of fresh mixture is required. The series of samples was prepared in which the mixture of natural aggregates was partially or totally substituted by recycled concrete aggregate. The 0/4 RCA fraction, which is usually rejected in ready mix concrete technology, plays a role of 0/2 sand. The substitution of sand fraction was from 20% to 100% respectively. The substitution of the coarser aggregate fractions by 4/16 RCA was also done. The standard properties of vibropressed elements, such as the degree of densification, the density of material, the compressive and splitting tensile strength and the water absorption capacity according to the relevant standards were determined. The parameters of materials with the natural aggregate substitution by RCA are affected by the ratio of recycled concrete aggregate. In most cases the results do not decline specially from those for reference samples, when only the natural sand (0/2) fraction is substituted by the 0/4 recycled aggregate. As one could expect, as lower the substitution, as better the test results. The partial substitution of natural aggregate by coarser fractions requires experimental verification; over 20% substitution of natural aggregate by 4/8, 8/16 or 0/16 RCA should be excluded.

Comparative Analysis of Facade Work Using Kumkang Precast, Concrete Precast, and Curtain Wall Methods in terms of Cost and Time

The development of the construction world in terms of innovation has become one of the methods of supporting success to gain advantages in terms of cost and time, one of which is the outer wall which can generally categorize into cast-in-situ and precast methods. (1) Comparison of the cost of implementing precast kumkang materials, precast concrete facades, and curtain wall facades. The precast kumkang method is 24% cheaper than the precast concrete method, the precast kumkang method is 87% cheaper than the curtain wall method, and the precast concrete method is 52% cheaper than the curtain wall method. Sorted from the cheapest to the most expensive are precast kumkang facades, precast concrete facades, and curtain wall facades. (2) Comparison of the working time of precast kumkang materials, precast concrete facades, and curtain wall facades with the results, namely curtain wall facades for 31 weeks, kumkang material precast facades for 53 weeks, and precast concrete facades for 55 weeks. Sorted from the fastest to longest, namely curtain wall facades, precast kumkang material facades, and then precast concrete facades.

INVESTIGATE THE CARBON FOOTPRINTS OF THREE INTERMEDIATE FLOORING SYSTEMS: CROSS-LAMINATED TIMBER, SOLID CONCRETE, AND HOLLOW-CORE PRECAST CONCRETE

This paper evaluates and compares the embodied energy and embodied carbon using a Life Cycle Assessment (LCA) approach for three different intermediate floor structures, all of which use prefabricated materials—cross-laminated timber (CLT), precast hollow-core concrete, and solid concrete—to decide which floor construction materials have less environmental impact for use in the construction of a semi-detached house in the UK. The Inventory of Carbon & Energy (ICE) and the Carbon Calculator tool were used to calculate the carbon footprint from “cradle to grave” to determine whether the use of a CLT solution provides improved environmental performance over the traditional concrete solutions. The carbon footprint results indicate that the use of a hollow-core precast concrete floor system emits less carbon than the other two systems, although the concrete requires more fossil fuel input than the timber during the manufacturing process, so based on this, the footprint from cradle to gate for the timber was expected to be the less than that of the concrete. However, the results show the opposite; this is because of the differences in the material quantities needed in each system.

ACCOUNTING FOR THE MALLEABILITY OF PRECAST REINFORCED CONCRETE STRUCTURES WHEN CALCULATING BUILDINGS USING PC SCAD OFFICE

The article discusses the main problems of accounting for the malleability of joints in the calculations of buildings from precast concrete