Local Wisdom of Builders on The Quality of Making Concrete in Kendari City Southeast Sulawesi Province

In Kendari City, the concrete structure made by construction workers consists of: (a) concrete for the lower class; (b) concrete for middle society, and; (c) concrete for the upper community. The concrete is made with different sand material. This research is important to find out the method of making concrete made by construction workers in Kendari City. This research is intended to test the compressive strength and absorbency of the concrete made by construction workers in Kendari City. This study uses an experimental method with a quantitative approach. Based on laboratory test results that concrete material from 100% Unaha sand with the composition of 1 sack of cement: 4 barrel of unaha sand included in structural concrete. Concrete material from split stone and Pohara sand with a composition of 1 sack of cement: 4 barrel of Pohara sand : 4 barrel of split stone, concrete material from Unaha sand and Pohara sand with a composition of 1 sack of cement: 4 barrels of Unaha sand : 4 barrels of Pohara sand, concrete material from 100% Nambo sand with the composition of 1 sack of cement: 4 barrels of Nambo sand, concrete material from Nambo sand and Unaha sand with a composition of 1 sack of cement: 3 barrels of Nambo sand : 1 barrel of Unaha sand, and concrete material from Nambo sand and Sabulakoa sand with composition of 1 sack of cement : 3 barrels of Nambo sand : 1 barrel of Sabulakoa sand are included in non-structural concrete.

Modelling and Simulation on Penetration into Stone Concrete

Penetration into stone concrete is an important research area of concrete penetration, and related experiments and simulation tests have been carried out. However, complete theories have not been formed yet. This paper develops a differential facet resistance model for penetration into stone concrete target. Firstly, the plastic damage model is used to analyze the penetration of concrete target, and the reliability of the numerical model is verified by comparing with the classical experimental results. Besides, the numerical model of stone concrete is established based on 3D Voronoi diagram according to the random characteristics of the shape and spatial distribution of stones in concrete. Then, simulation tests are carried out with the validated numerical model, a differential facet resistance model suitable for the penetration of stone concrete target is then proposed referring to the resistance formula of Forrestal and Rosenberg. At last, a method for fast calculation of penetration into stone concrete is introduced.

Efficiency justification for stone-concrete face zone of rockfill dams with reinforced concrete face

At present, over 600 dams with a reinforced concrete face are built worldwide; 7 of them are higher than 200 m. However, most of these dams have an inherent disadvantage – face cracking [1, 2, 3], caused by face deformations resulted from the difference in deformation properties of the face and downstream toe. To solve this problem, the authors consider the arrangement of a massive stone-concrete face zone.

Environmental Factors Causing the Development of Microorganisms on the Surfaces of National Cultural Monuments Made of Mineral Building Materials—Review

The ability of microorganisms to degrade building materials depends on several factors. Biological corrosion occurs in close dependence with chemical and physical factors affecting microorganisms. The growth and development of microorganisms is stimulated by external stimuli, i.e., environmental factors. Microorganisms have a relatively large tolerance range for changes in environmental conditions. Under the right conditions, microorganisms thrive very well. The adverse effects may cause the inhibition of cell growth, damage, or lead to the death of the microorganism. Considering the impact of environmental factors on microorganisms, it is not possible to identify the most important of them. The result effect of overlapping factors determines the possibility of the growth of certain microorganisms. The main factors affecting the growth are temperature, humidity, hydrogen ion concentration in the environment, oxidoreductive potential, water activity in the environment, and hydrostatic pressure. This article provides a comprehensive overview of the factors causing biodeterioration. The influence of external/internal environment on the surface of cultural monuments made of mineral building materials, i.e., stone, concrete, mortar, etc., is presented.

Mixed greywater treatment for irrigation uses

Water contamination comes from many different sources, including, among others, factories, sewage treatment plants, mining activities (heavy metals), food-processing waste, agriculture runoff, animal waste, disposal of personal care products, and household chemicals. Therefore, the reuse of wastewater has become a fundamental strategy for sustainable water management and maintaining environmental quality. In this sense, this research presents a simple and economic alternative to solving the problems caused by greywater, resulting from laundry activities. This paper evaluates a mixed system for the treatment of greywater. The mixed system has physical filters that are composed of river stone, concrete, river sand, and coal. A bioremediation technique is also evaluated, involving two types of aquatic plants, watercress (Nasturtium officinale L.) and duckweed (Lemma minor L.). This study showed significant differences in pH reduction, from 9.56 to 7.50, total suspended solids (TSS), from 1742.00 mg/L to 298.50 mg/L, phosphates, from 1.12 mg/L PO43¯ to 0.31 mg/L PO43- , and chemical oxygen demand (COD), from 472.38 mg/L to 8.52 mg/L. Thus, the results indicate that this system is efficient for the reuse of grey water for irrigation uses. Moreover, each parameter, with the exception of dissolved oxygen and total suspended solids (TSS), meets the maximum limits set by the Environmental Quality Standards for Category 3: irrigation water for vegetables and animal beverages and the FAO irrigation water standards.

Strength of concrete produced with different sources of aggregates from selected parts of Abia and Imo States of Nigeria

Purpose This paper aims to investigate the 28-day compressive strength of concrete produced with aggregates from different sources. Design/methodology/approach Coarse aggregates were crushed granite and natural local stones mined from Umunneochi, Lokpa and Uturu, Isuakwato, respectively, in Abia State, Nigeria. Fine aggregate (river sand) and another coarse aggregate (river stone) were dredged from Otammiri River in Owerri, Imo State, Nigeria. The nominal mix ratios were 1:1:2, 1:2:4 and 1:3:6, whereas the respective water–cement ratios were 0.45, 0.5, 0.55 and 0.6. Findings The compressive strength of granite concrete, river stone concrete and local stone concrete ranged 17.79-38.13, 15.37-34.57 and 14.17-31.96 N/mm2, respectively. Compressive strength was found to increase with decreasing water–cement ratio and increasing cement content. Practical implications Granite concrete should be used in reinforced-concrete construction, especially when a cube compressive strength of 30 N/mm2 or higher is required. Originality/value Granite concrete exceeded the target compressive strength for all the concrete specimens, whereas river stone concrete and local stone concrete failed to achieve the target strength for some mix proportions and water–cement ratios.

СРАВНИТЕЛЬНАЯ ОЦЕНКА РАЗЛИЧНЫХ ТЕХНОЛОГИЧЕСКИХ ПРИЕМОВ ВВЕДЕНИЯ ДОБАВОК УГЛЕРОДНЫХ НАНОМАТЕРИАЛОВ В БЕТОНЫ И БЕТОННЫЕ СМЕСИ

В материале статьи отражены основные результаты исследования влияния различных технологических приемов введения отечественных углеродных наноматериалов (УНМ) в тяжелые и мелкозернистые бетоны и бетонные смеси. Введение малого количества твердофазного вещества УНМ в бетон представляет собой сложную задачу с позиций его равномерного распределения по объему приготавливаемой бетонной смеси, т. к. это не растворимое в воде вещество. Кроме этого, вследствие малого собственного размера частицы УНМ при комнатной температуре и атмосферном давлении начинают самоорганизовываться , объединяясь и укрупняясь вплоть до образования микроскопических гранул . Введение в цемент (бетон, раствор) углеродных наноматериалов различными технологическими приемами обеспечивает рост прочности цементного камня (бетона, раствора) как в условиях естественного (нормально-влажностного) твердения, так и в случае ускоренного твердения при тепловой обработке образцов. На уровень прироста прочности цементного камня (бетона, раствора), в отдельных случаях достигавшего 4060 , оказывает основное влияние вид (состав) УНМ и дозировка вещества оптимальная примерно соответствует 0,05 от массы цемента. Все проверенные способы введения УНМ могут быть реализованы при производстве бетонных смесей (бетонов, растворов). При тщательной проработке технологии введения тем или иным способом возможно обеспечение равномерного распределения УНМ в объеме смеси, что подтверждается примерным равенством увеличения прочности цементного камня для различных способов введения (смешиванием с цементом, песком, химическими добавками, диспергированием в воде затворения). Но наиболее перспективным представляется прием введения УНМ в комплексе с порошкообразными твердофазными пластифицирующей и ускоряющей твердение цемента химическими добавками для бетона. Полученные результаты исследований развивают предпосылки к более широкому использованию УНМ в конструкционных цементных бетонах.Тhe main results of a research of influence of various processing methods of introduction of domestic carbon nanomaterials (СNM) to heavy and fine-grained concrete and concrete mixes are reflected in material of article. Introduction of small amount of solid-phase substance СNM to concrete represents a difficult task from positions of its uniform distribution on volume of the prepared concrete mix since this insoluble substance in water. Besides, owing to the small own size of a particle of СNM at the room temperature and atmospheric pressure begin to self-organize, uniting and being integrated up to formation of microscopic granules. Introduction to cement (concrete, mortar) of carbon nanomaterials various processing methods, provides growth of durability of a cement stone (concrete, mortar) both in the conditions of natural (normal and moist) curing, and in case of the accelerated curing at thermal treatment of samples. The type (structure) of СNM and dosage of substance has the main impact on the level of gain of durability of a cement stone (concrete, mortar) in some cases reaching 40 60 optimum approximately there correspond 0,05 of the mass of cement. All checked ways of introduction of СNM can be realized by production of concrete mixes (concrete, mortar). At careful study of technology of introduction ensuring uniform distribution of СNM in volume of mix is one way or another possible that is confirmed by approximate equality of increase in durability of a cement stone for various ways of introduction (mixing with cement, sand, chemical additives, dispersion in water). But reception of introduction of СNM in a complex with the powdery solid-phase chemical additives plasticizing and accelerating cement curing for concrete is represented to the most perspective. The received results of researches develop prerequisites to wider use of СNM in constructional cement concrete.

Development of Seismic Fragility Curves of RC Infilled Frame Buildings in Jordan

This article examines the seismic fragility of low- and mid-rise RC infilled frame buildings in Jordan comprising stone-concrete infill panels. Three dimensional models of 2, 4 and 6 story regular and irregular representative buildings were developed. Pushover analyses were performed to construct capacity curves of the model buildings. Four damage states were considered: slight, moderate, extensive and complete and damage state thresholds were assigned, using expert opinion, based on yield and ultimate spectral displacements of the capacity spectra. Sets of preliminary fragility curves were developed to quantify earthquake damage probabilities in terms of spectral displacements.